Michael Ruderman

• Efimov, Denis & Ruderman, Michael (2024). Stability analysis and integral extension of sub-optimal nonlinear damping control. International Journal of Robust and Nonlinear Control. ISSN 1049-8923. doi: 10.1002/rnc.7447. Show summary

  The problems of robustness with respect to external inputs and of convergence rate estimation are considered for the so called sub-optimal nonlinear damping control [1]. To this end, existence of solutions is justified, a strict Lyapunov function is found and its properties are investigated. The hyperexponential convergence of the unperturbed sub-optimal nonlinear damping control is demonstrated. Moreover, an integral extension is proposed to complement the controller with capability of compensation for static errors. The results are illustrated by numeric simulations and the control experiments.

• Voss, Benjamin; Ruderman, Michael & Reger, Johann (2024). Experimental Evaluation of Homogeneous Differentiators Applied to Hydraulic Stroke with Measurement Noise and Acceleration Disturbance, IEEE AMC2024 conference proceeding. IEEE conference proceedings. ISSN 979-8-3503-4281-9.
• Estrada, Manuel; Ruderman, Michael & Fridman, Leonid M. (2024). Super-twisting based sliding mode control of hydraulic actuator without velocity state. Control Engineering Practice. ISSN 0967-0661. 142. doi: 10.1016/j.conengprac.2023.105739. Show summary

  This paper provides a novel surface design and experimental evaluation of a super-twisting algorithm (STA) based control for hydraulic cylinder actuators. The proposed integral sliding surface allows to track a sufficiently smooth reference without using the velocity state which is hardly accessible in the noisy hydraulic systems. A design methodology based on LMI’s is given, and the STA gains are designed to be adjusted by only one free parameter. The feasibility and effectiveness of the proposed control method are shown on a standard hydraulic test bench with one linear degree of freedom and passive load, where a typical motion profile is tracked with a bounded average error below 1% from the total drive effective output.

• Ruderman, Michael (2023). Energy dissipation and hysteresis cycles in pre-sliding transients of kinetic friction. Applications of Mathematics. ISSN 0862-7940. 68(6), p. 845–860. doi: 10.21136/AM.2023.0283-22. Full text in Research Archive Show summary

  The problem of transient hysteresis cycles induced by the pre-sliding kinetic friction is relevant for analyzing the system dynamics, e.g., of micro- and nano-positioning instruments and devices and their controlled operation. The associated energy dissipation and consequent convergence of the state trajectories occur due to the structural hysteresis damping of contact surface asperities during reversals, and it is neither exponential (i.e., viscous type) nor finite-time (i.e., Coulomb type). In this paper, we discuss the energy dissipation and convergence during the pre-sliding cycles and show how a piecewise smooth force-displacement hysteresis map enters into the energy balance of an unforced system of the second order. An existing friction modeling approach with a low number of the free parameters, the Dahl model, is then exemplified alongside the developed analysis.

• Ruderman, Michael (2023). Time-delay based output feedback control of fourth-order oscillatory systems. Mechatronics (Oxford). ISSN 0957-4158. 94. doi: 10.1016/j.mechatronics.2023.103015. Full text in Research Archive Show summary

  We consider stabilization of the fourth-order oscillatory systems with non-collocated output sensing. Worth recalling is that the fourth-order systems are relatively common in mechatronics as soon as there are two-mass or more generally two-inertia dynamics with significant elasticities in the link. A novel yet simple control method is introduced based on the time-delayed output feedback. The delayed output feedback requires only the oscillation frequency to be known and allows for a robust control design that leads to cancelation of the resonance peak. We use the stability margins to justify the transfer characteristics and robustness of the time-delay control in frequency domain. The main advantage of the proposed method over the other possible lead-based loop-shaping strategies is that neither time derivatives of the noisy output nor the implementation of transfer functions with a numerator degree greater than zero are required to deploy the controller. This comes in favor of practical applications. An otherwise inherently unstable proportional-integral (PI) feedback of the non-collocated output is shown to be stabilized by the proposed method. The control developed and associated analysis are also confirmed by the experimental results shown for the low damped two-mass oscillator system with uncertainties.

• Ruderman, Michael (2023). Inversion-free feedforward hysteresis control using Preisach model, Proceedings of 2023 European Control Conference (ECC). IEEE conference proceedings. ISSN 978-3-907144-08-4. Full text in Research Archive
• Ruderman, Michael (2023). Robust asymptotic observer of motion states with nonlinear friction, 22nd IFAC World Congress. Elsevier. ISSN 9781510850712. p. 5931–5936. doi: 10.1016/j.ifacol.2023.10.1909. Full text in Research Archive
• Checchin, Riccardo; Ruderman, Michael & Oboe, Roberto (2023). Robust two-degrees-of-freedom control of hydraulic drive with remote wireless operation. In Ruderman, Michael & Chen, Wen-Hua (Ed.), Proceeding IEEE International Conference on Mechatronics (ICM2023). IEEE conference proceedings. ISSN 978-1-6654-6661-5. doi: 10.1109/ICM54990.2023.10101993. Full text in Research Archive Show summary

  In this paper, we present a controller design targeting a remotely operated hydraulic drive system. We use a two-degrees-of-freedom PID position controller, which is designed so that to maximize the integral action under robust constraint. A linearized model of the system plant, affected by the parameters uncertainties such as variable communication time-delay and overall system gain, is formulated and serves for the control design and analysis. The performed control synthesis and evaluation target a remote operation where the wireless communication channel cannot secure a deterministic real-time of the feedback loop. The provided analysis of uncertainties makes it possible to ensure system stability under proper conditions. We demonstrate the theoretically expected results through laboratory experiments on the standard industrial hydraulic components.

• Oboe, Roberto & Ruderman, Michael (2022). The 17th IEEE International Conference on Advanced Motion Control [Society News]. IEEE Industrial Electronics Magazine. ISSN 1932-4529. 16(3). doi: 10.1109/MIE.2022.3190982.
• Ruderman, Michael (2022). Motion control with optimal nonlinear damping: From theory to experiment. Control Engineering Practice. ISSN 0967-0661. 127. doi: 10.1016/j.conengprac.2022.105310. Full text in Research Archive Show summary

  Optimal nonlinear damping control was recently introduced for the second-order SISO systems, showing some advantages over a classical PD feedback controller. This paper summarizes the main theoretical developments and properties of the optimal nonlinear damping controller and demonstrates, for the first time, its practical experimental evaluation. An extended analysis and application to more realistic (than solely the double-integrator) motion systems are also given in the theoretical part of the paper. As comparative linear feedback controller, a PD one is taken, with the single tunable gain and direct compensation of the plant time constant. The second, namely experimental, part of the paper includes the voice-coil drive system with relatively high level of the process and measurement noise, for which the standard linear model is first identified in frequency domain. The linear approximation by two-parameters model forms the basis for designing the PD reference controller, which fixed feedback gain is the same as for the optimal nonlinear damping control. A robust sliding-mode based differentiator is used in both controllers for a reliable velocity estimation required for the feedback. The reference PD and the proposed optimal nonlinear damping controller, both with the same single design parameter, are compared experimentally with respect to trajectory tracking and disturbance rejection.

• Ruderman, Michael; Zagvozdkin, Andrei & Rachinskii, Dmitrii (2022). Dynamics of inertial pair coupled via frictional interface. In Aghdam, Amir & IEEE, . (Ed.), IEEE 61st Conference on Decision and Control (CDC 2022). IEEE conference proceedings. ISSN 978-1-6654-6761-2. p. 1324–1328. doi: 10.1109/CDC51059.2022.9993163. Full text in Research Archive
• Ruderman, Michael & Fridman, Leonid M. (2022). Analysis of relay-based feedback compensation of Coulomb friction. In Oliveira, Tiago (Eds.), Proceeding of IEEE 16th International Workshop on Variable Structure Systems. IEEE conference proceedings. ISSN 1479955663. p. 95–100. doi: 10.1109/VSS57184.2022.9902091. Show summary

  Standard problem of one-degree-of-freedom mechanical systems with Coulomb friction is revised for a relay-based feedback stabilization. It is recalled that a system with Coulomb friction is asymptotically stabilizable via a relay-based output feedback, as formerly demonstrated in [1]. Assuming an upper bounded Coulomb friction disturbance, a time-optimal gain of the relay-based feedback control is found by minimizing the derivative of the Lyapunov function proposed in [2] for the twisting algorithm. Furthermore, changing from the discontinuous Coulomb friction to a more physical discontinuity-free one, which implies a transient presliding phase at motion reversals, we analyze the residual steady-state oscillations, in the sense of stable limit cycles, in addition to chattering caused the by the actuator dynamics. The numerical examples and an experimental case study accompany the provided analysis.

• Voss, Benjamin; Weise, Christoph; Ruderman, Michael & Reger, Johann (2022). Fractional-Order Partial Cancellation of Integer-Order Poles and Zeros. In Peaucelle, Dimitri (Eds.), Proceeding of 10th IFAC Symposium on Robust Control Design (ROCOND 2022). IFAC Papers Online. ISSN 978-3-902823-37-3. p. 259–264. doi: 10.1016/j.ifacol.2022.09.356. Full text in Research Archive
• Voss, Benjamin; Ruderman, Michael; Weise, Christoph & Reger, Johann (2022). Comparison of Fractional-Order and Integer-Order H-infinity Control of a Non-Collocated Two-Mass Oscillator. In Peaucelle, Dimitri (Eds.), Proceeding of 10th IFAC Symposium on Robust Control Design (ROCOND 2022). IFAC Papers Online. ISSN 978-3-902823-37-3. p. 145–150. doi: 10.1016/j.ifacol.2022.09.338. Full text in Research Archive
• Ruderman, Michael (2021). One-parameter robust global frequency estimator for slow-varying amplitude and noisy oscillations. Mechanical systems and signal processing. ISSN 0888-3270. 170. doi: 10.1016/j.ymssp.2021.108756.
• Ruderman, Michael (2021). Stick-slip and convergence of feedback-controlled systems with Coulomb friction. Asian journal of control. ISSN 1561-8625. 24(6), p. 2877–2887. doi: 10.1002/asjc.2718. Full text in Research Archive Show summary

  An analysis of stick-slip behavior and convergence of trajectories in the feedback-controlled motion systems with discontinuous Coulomb friction is provided. A closed-form parameter-dependent stiction region, around an invariant equilibrium set, is proved to be always reachable and globally attractive. It is shown that only asymptotic convergence can be achieved, with at least one but mostly an infinite number of consecutive stick-slip cycles, independent of the initial conditions. Theoretical developments are supported by a number of numerical results with dedicated convergence examples.

• Ruderman, Michael (2021). Convergent dynamics of optimal nonlinear damping control, 6th IFAC Conference on Analysis and Control of Chaotic Systems CHAOS 2021. IFAC Papers Online. ISSN 2405-8963. p. 141–144. doi: 10.1016/j.ifacol.2021.11.039. Full text in Research Archive Show summary

  Following the Demidovich’s concept and definition of convergent systems, we analyze the optimal nonlinear damping control which was recently proposed for the second-order systems. Targeting the problem of servo-regulation, and more specifically output tracking of the C1 reference trajectories, it is shown that all solutions of the proposed control system are globally uniformly asymptotically stable. The existence of the unique limit solution in the coordinates origin of the control error and its time derivative are shown in the sense Demidovich’s convergent dynamics. Explanatory numerical examples are provided to accompany the analysis.

• Weise, Christoph; Pfeffer, Philipp; Reger, Johann & Ruderman, Michael (2021). Parameter Identification of Fractional-Order LTI Systems using Modulating Functions with Memory Reduction, Proceedings of IEEE CDC2021 conference. IEEE conference proceedings. ISSN 978-1-6654-3659-5. Show summary

  The parameter estimation problem of a linear time-invariant fractional-order system is investigated by means of the modulating function method. Based on the assumption of known model structure and derivative orders, the modulating function method can be generalized to the fractional-order case in three different ways. We show that two approaches are identical for linear systems. This facilitates the computation of the fractional-order derivatives of modulating functions. The second part includes the initialization of the fractional-order system. We show that the spline type modulating function is capable of reducing the effect of the memory on the parameter estimation. However, it is not possible to compensate the initialization completely. In contrast to these tuning principles also the robustness against measurement noise must be considered. For this purpose we decouple the memory and noise compensation. The adjusted spline-type modulating functions reduce the initialization effect and the recursive least square estimation provides the possibility to increase the numbers of equations such that the effect of the noise is reduced.

• Ruderman, Michael (2021). Optimal terminal sliding mode control for second-order motion systems, Proceedings of IEEE CDC2021 conference. IEEE conference proceedings. ISSN 978-1-6654-3659-5. p. 6421–6426. Show summary

  Terminal sliding mode (TSM) control algorithm and its non-singular refinement have been elaborated for two decades and belong, since then, to a broader class of the finite-time controllers, which are known to be robust against the matched perturbations. While TSM manifold allows for different forms of the sliding variable, which are satisfying the q/p power ratio of the measurable output state, we demonstrate that q/p=0.5 is the optimal one for the second-order Newton’s motion dynamics with a bounded control action. The paper analyzes the time-optimal sliding surface and, based thereupon, claims the optimal TSM control for the second-order motion systems. It is stressed that the optimal TSM control is fully inline with the Fuller’s problem of optimal switching which minimizes the settling time, i.e. with time-optimal control of an unperturbed double-integrator. Is is also shown that for the given plant characteristics, i.e. the overall inertia and control bound, there is no need for additional control parameters. The single surface design parameter might (but not necessarily need to) be used for driving system on the boundary layer of the twisting mode, or for forcing it to the robust terminal sliding mode. Additional insight is given into the finite-time convergence of TSM and robustness against the bounded perturbations. Numerical examples with different upper-bounded perturbations are demonstrated.

• Tranninger, Markus & Ruderman, Michael (2021). Stability Analysis of a Linear Parameter Varying Adaptive Output Feedback Control System, 4th IFAC Workshop on Linear Parameter-Varying Systems. IFAC Papers Online. ISSN 9781713807773. doi: 10.1016/j.ifacol.2021.08.582. Show summary

  Output feedback control systems often require an adaptive filter for properly shaping the loop transfer function, as certain system plant parameters may be uncertain or varying. This renders the overall closed loop to a linear parameter varying (LPV) system, for which the stability analysis is challenging due to non-trivial dynamics of the adaptation law. This paper develops a stability analysis technique of a feedback controlled oscillatory system. A polytopic overapproximation of the parameter set together with the feasibility of certain LMIs guarantees asymptotic stability of the closed loop. The varying parameter is only required to be lower and upper bounded, where the bounds can be obtained from the proposed strategy. Hence, any filter adaptation law is allowed for this parameter range. A meaningful numerical example based on a fifth-order plant and a second-order adaptive filter demonstrates the usefulness and appealing simplicity of the proposed approach.

• Ruderman, Michael (2021). On stiffness and damping of vibro-impact dynamics of backlash, IEEE 30th International Symposium on Industrial Electronics (ISIE). IEEE conference proceedings. ISSN 978-1-7281-5635-4. doi: 10.1109/ISIE45552.2021.9576274. Full text in Research Archive Show summary

  We consider the stiffness and damping properties of the vibro-impact in a backlash pair. Opposed to the existing and mostly used models of the backlash, we address the problem of contact and separation, and the associated force propagation within a mechanical pair, from a viewpoint of vibro-impact dynamics. We discuss the impact forces with the coefficient of restitution as a principal factor which shapes the transient backlash response. We show that a common approach to modeling the backlash by means of a dead-zone in a restoring force is unsuitable for correctly capturing the mechanical impact. We exemplary demonstrate a qualitative accord between an experimental backlash response and the postulated modeling approach. Backlash related energy losses of the vibroimpact damping are also addressed in brief.

• Ruderman, Michael (2021). Robust output feedback control of non-collocated low-damped oscillating load, Proceeding of IEEE 2021 29th Mediterranean Conference on Control and Automation (MED). IEEE conference proceedings. ISSN 978-1-6654-2258-1. p. 639–644. Show summary

  For systems with order of dynamics higher than two and oscillating loads with low damping, a non-collocation of the sensing and control can deteriorate robustness of the feedback and, in worst case, even bring it to instability. Furthermore, for a contactless sensing of the oscillating mechanical load, like in the system under investigation, the control structure is often restricted to the single proportional feedback only. This paper proposes a novel robust feedback control scheme for a low-damped fourth-order system using solely the measured load displacement. For reference tracking, the loop shaping design relies on a band reject filter, while the plant uncertainties are used as robustness measure for determining the feedback gain. Since prime uncertainties are due to the stiffness of elastic link, correspondingly connecting spring, and due to the gain of actuator transducer, the loop sensitivity function with additive plant variation is used for robustness measure. In order to deal with unknown disturbances, which are inherently exciting the load oscillations independently of the loop shaping performance, an output delay-based compensator is proposed as a second control-degree-of-freedom. That one requires an estimate of the load oscillation frequency only and does not affect the shaped open-loop behavior, correspondingly sensitivity function. An extensive numerical setup of the modeled system, a two-mass oscillator with contactless sensing of the load under gravity and low damping of the connecting spring, is used for the control evaluation and assessment of its robustness.

• Ruderman, Michael (2021). Optimal nonlinear damping control of second-order systems. Journal of the Franklin Institute. ISSN 0016-0032. 358(8), p. 4292–4302. doi: 10.1016/j.jfranklin.2021.03.022. Full text in Research Archive Show summary

  Novel nonlinear damping control is proposed for the second-order systems. The proportional output feedback is combined with the damping term which is quadratic to the output derivative and inverse to the set-point distance. The global asymptotic stability, passivity property, and convergence time and accuracy are demonstrated. Also the control saturation case is explicitly analyzed. The suggested nonlinear damping is denoted as optimal since requiring no additional design parameters and ensuring a fast convergence, without transient overshoots for a non-saturated and one transient overshoot for a saturated control configuration.

• Ruderman, Michael (2021). Extended fractional-order Jeffreys model of viscoelastic hydraulic cylinder. Journal of Dynamic Systems Measurement, and Control. ISSN 0022-0434. 143(7). doi: 10.1115/1.4050253. Show summary

  A novel modeling approach for viscoelastic hydraulic cylinders, with negligible inertial forces, is proposed, based on the extended fractional-order Jeffreys model. Analysis and physical reasoning for the parameter constraints and order of the fractional derivatives are provided. Comparison between the measured and computed frequency response functions and time domain transient response argues in favor of the proposed four-parameter fractional-order model.

• Aracil, Carmen; Sziebig, Gabor; Korondi, Peter; Oh, Sehoon; Tan, Zhichao & Ruderman, Michael [Show all 11 contributors for this article] (2021). Toward Smart Systems: Their Sensing and Control in Industrial Electronics and Applications. IEEE Industrial Electronics Magazine. ISSN 1932-4529. 15(1), p. 104–114. doi: 10.1109/MIE.2020.3042171.
• Ruderman, Michael; Kaltenbacher, Stefan & Horn, Martin (2021). Pressure-flow dynamics with semi-stable limit cycles in hydraulic cylinder circuits, Proceeding of IEEE International Conference on Mechatronics (ICM2021). IEEE conference proceedings. ISSN 978-1-5386-6959-4. doi: 10.1109/ICM46511.2021.9385620. Show summary

  In hydraulic circuits of the standard fluid-power actuators and mechanisms, like the linear-stroke cylinders, some hydrodynamic effects are often neglected. It happens mainly due to their complexity and secondariness in comparison with the principal transient and steady-state behavior of the hydromechanical process variables, such as the differential pressure and relative displacement and its rate, in other words the piston stroke and velocity. However, a constrained motion of the cylinder piston can give rise to the back coupled excitation of the pressure-flow dynamics, especially upon mechanical impact at the cylinder limits. Following to that, semi-stable limit cycles can arise while the hydraulic cylinder remains under pressure without apparent displacement. This paper analyzes such back-coupled pressure-flow dynamics, derived from the partial differential momentum equation with involvement of Darcy-Weisbach hydraulic damping and continuity equation, out from which the closed-form system dynamics is formulated. In both, simulations and laboratory experiments, it is shown that if a constrained motion applies, the solution diverges from steady-state and can develop to the behavior similar to a semi-stable limit cycle.

• Tavares, Rafael Pinto & Ruderman, Michael (2021). Frequency-domain experimental setup for mechatronic and suspension system components, Proceeding of IEEE International Conference on Mechatronics (ICM2021). IEEE conference proceedings. ISSN 978-1-5386-6959-4. doi: 10.1109/ICM46511.2021.9385640. Show summary

  This paper presents a frequency-domain experimental setup for modal analysis of mechatronic and suspension system components. Design, instrumentation and dynamic behavior of the one degree-of-freedom (DOF) system, capable of providing both, periodic and application-specific, excitation forces is described. The excitation is realized by an electromagnetic modal shaker with additional assembly and interface components designed and instrumented for frequency -domain analysis of vertical dynamics. Frequency response functions (FRFs) of the implemented system are experimentally measured and the associated basic model parameters are calculated, correspondingly identified. Accurate fit between the measured FRFs and modeled dynamics is shown for sufficiently large frequency range 0.1-30 Hz of the mechanical system response. Exemplary standard road profile excitations are also conducted to demonstrate the applicability of the designed system for frequency-domain testing of components in the vehicle suspension systems.

• Ano, Shuta; Seki, Kenta; Ruderman, Michael & Iwasaki, Makoto (2021). Estimating Sway Angle of Pendulum System Using Hybrid State Observer Incorporating Continuous and Discrete Sensing Signals. IEEJ Journal of Industry Applications. ISSN 2187-1094. 10(1), p. 69–75. doi: 10.1541/IEEJJIA.20004820. Full text in Research Archive
• Oboe, Roberto; Ruderman, Michael & Fujimoto, Yasutaka (2020). Guest Editorial: Advanced Motion Control for Mechatronic Applications with Precision and Force Requirements. IEEE transactions on industrial electronics (1982. Print). ISSN 0278-0046. 68(1), p. 721–723. doi: 10.1109/TIE.2020.3023847.
• Pasolli, Philipp Thomas & Ruderman, Michael (2020). Hybrid Position/Force Control for Hydraulic Actuators, Proceeding IEEE 28th Mediterranean Conference on Control and Automation (MED'2020). IEEE conference proceedings. ISSN 978-1-5386-7890-9. p. 73–78. doi: 10.1109/MED48518.2020.9183305.
• Tavares, Rafael Pinto & Ruderman, Michael (2020). Dissipation in suspension system augmented by piezoelectric stack: port-Hamiltonian approach, Proceeding IEEE 28th Mediterranean Conference on Control and Automation (MED'2020). IEEE conference proceedings. ISSN 978-1-5386-7890-9. p. 168–173. doi: 10.1109/MED48518.2020.9183317.
• Ruderman, Michael (2020). On stability of linear dynamic systems with hysteresis feedback. Mathematical Modelling of Natural Phenomena. ISSN 0973-5348. 15(52). doi: 10.1051/mmnp/2020014. Full text in Research Archive Show summary

  The stability of linear dynamic systems with hysteresis in feedback is considered. While the absolute stability for memoryless nonlinearities (known as Lure’s problem) can be proved by the well-known circle criterion, the multivalued rate-independent hysteresis poses significant challenges for feedback systems, especially for proof of convergence to an equilibrium state correspondingly set. The dissipative behavior of clockwise input-output hysteresis is considered with two boundary cases of energy losses at reversal cycles. For upper boundary cases of maximal (parallelogram shape) hysteresis loop, an equivalent transformation of the closed-loop system is provided. This allows for the application of the circle criterion of absolute stability. Invariant sets as a consequence of hysteresis are discussed. Several numerical examples are demonstrated, including a feedback-controlled double-mass harmonic oscillator with hysteresis and one stable and one unstable poles configuration.

• Weise, Christoph; Tavares, Rafael Pinto; Wulf, Kai; Ruderman, Michael & Reger, Johann (2020). A Fractional-Order Control Approach to Ramp Tracking with Memory-Efficient Implementation, Proceeding of IEEE International Workshop on Advanced Motion Control (AMC2020). IEEE conference proceedings. ISSN 978-1-7281-3189-4. p. 15–22. doi: 10.1109/AMC44022.2020.9244309.
• Kapp, Daniela; Weise, Christoph; Ruderman, Michael & Reger, Johann (2020). Fractional-Order System Identification of Viscoelastic Behavior: A Frequency Domain Based Experimental Study, Proceeding of IEEE International Workshop on Advanced Motion Control (AMC2020). IEEE conference proceedings. ISSN 978-1-7281-3189-4. p. 153–160. doi: 10.1109/AMC44022.2020.9244449.
• Tavares, Rafael Pinto; Ruderman, Michael; Menjoie, Daan; Molina, Joan Vazquez & Dhaens, Miguel (2020). Modeling and field-experiments identification of vertical dynamics of vehicle with active anti-roll bar, Proceeding of IEEE International Workshop on Advanced Motion Control (AMC2020). IEEE conference proceedings. ISSN 978-1-7281-3189-4. p. 161–167. doi: 10.1109/AMC44022.2020.9244454.
• Ruderman, Michael (2020). Lead-Lag-Shaped Interactive Force Estimation by Equivalent Output Injection of Sliding-Mode, Proceeding of European Control Conference (ECC 2020). IEEE conference proceedings. ISSN 978-3-907144-01-5. p. 1619–1623. doi: 10.23919/ECC51009.2020.9143619.
• Ruderman, Michael; Iwasaki, Makoto & Chen, Wen-Hua (2020). Motion-Control Techniques of Today and Tomorrow: A Review and Discussion of the Challenges of Controlled Motion. IEEE Industrial Electronics Magazine. ISSN 1932-4529. 14(1), p. 41–55. doi: 10.1109/MIE.2019.2956683. Full text in Research Archive
• Tavares, Rafael Pinto & Ruderman, Michael (2020). Energy harvesting using piezoelectric transducers for suspension systems. Mechatronics (Oxford). ISSN 0957-4158. 65. doi: 10.1016/j.mechatronics.2019.102294. Full text in Research Archive
• Ruderman, Michael & Fridman, Leonid (2019). Model-free sliding-mode-based detection and estimation of backlash in drives with single encoder. IEEE Transactions on Control Systems Technology. ISSN 1063-6536. 29(2), p. 812–817. doi: 10.1109/TCST.2019.2956914. Full text in Research Archive
• Ruderman, Michael; Fridman, Leonid & Pasolli, Philipp Thomas (2019). Virtual Sensing of Load Forces in Hydraulic Actuators using Second- and Higher-Order Sliding Modes. Control Engineering Practice. ISSN 0967-0661. 92. doi: 10.1016/j.conengprac.2019.104151. Full text in Research Archive Show summary

  External load forces are challenging for sensing or estimating in the hydraulic actuators. Once it is due to inconvenient instrumentation of the force sensors, especially on an open-end mechanical interface. The other way, the complex nonlinear system behavior aggravates reconstructing the system states in a robust and real-time suitable manner. This paper proposes a sensorless estimation of external load forces in standard hydraulic actuators by using a well-established equivalent output injection of the second-order sliding mode and also higher-order sliding mode differentiator. Only the basic inertial and frictional parameters are assumed to be known from an initial identification without external load. Afterwards, the robust exact differentiators are used in order to reconstruct the system states. Noisy signals of the cylinder chamber pressures and piston stroke are the single quantities available from the measurement. An experimental case study, accomplished on the setup of two hydraulic cylinders arranged and operated in antagonistic way, is provided. The force-cell on the rigid interface between both cylinders is used for reference measurements and evaluation of the estimation algorithms. Two estimation approaches, one of the 2nd and another of the 4th order, are assessed in performance and compared to each other along with discussion.

• Ruderman, Michael (2019). On Stability of Virtual Torsion Sensor for Control of Flexible Robotic Joints with Hysteresis. Robotica (Cambridge. Print). ISSN 0263-5747. doi: 10.1017/S0263574719001358. Full text in Research Archive Show summary

  Aim of the virtual torsion sensor (VTS) is in observing the nonlinear deflection in the flexible joints of robotic manipulators and, by its use, improving positioning control of the joint load. This model-based approach utilizes the motor-side sensing only and, therefore, replaces the load-side encoders at nearly zero hardware costs. For being applied in the closed control loop, the stability and robustness of VTS are most crucial. This work extends the previous analysis by a general case of nonlinear joint stiffness with hysteresis and provides straightforward conditions with respect to the system dynamics. The dissipativity and passivity of the torsion-torque hysteresis map are analyzed and discussed in detail. The absolute stability of VTS inclusion into position control loop is shown based on the equivalent loop transformations and Popov criteria, including the sector conditions. Illustrative numerical examples of the control error dynamics and its convergence are provided.

• Ano, Shuta; Seki, Kenta; Ruderman, Michael & Iwasaki, Makoto (2019). Estimation of Sway-angle Based on Hybrid State Observer Using Continuous and Discrete Sensing, Proceeding 45th Annual Conference of the IEEE Industrial Electronics Society - IECON 2019. IEEE conference proceedings. ISSN 978-1-7281-4878-6. p. 3123–3128. doi: 10.1109/IECON.2019.8927378. Show summary

  A hybrid state observer design is presented herein to estimate sway-angle and angular velocity in trolley systems with pendulum. In general, anti-sway control for trolley systems with pendulum such as overhead cranes are designed based on sway-angle signals detected by angular sensors. Opposed to that, a state observer without those sensors is proposed to estimate the sway-angle of the pendulum. A standard linear continuous feedback observer causes estimation error owing to the system nonlinearity and modeling error. This paper proposes a hybrid state observer incorporating discrete sensor signals. In the hybrid state observer, the estimation performance is improved by correcting the state of the system based on discrete signals. The effectiveness of the hybrid state observer is verified by conducting experiments using a downscaled testbed of a trolley system with pendulum.

• Tavares, Rafael Pinto; Molina, Joan Vazquez; Al Sakka, Monzer; Dhaens, Miguel & Ruderman, Michael (2019). Modeling of an active torsion bar automotive suspension for ride comfort and energy analysis in standard road profiles, Proceeding of 8th IFAC Symposium on Mechatronic Systems and 11th IFAC Symposium on Nonlinear Control Systems. IFAC Papers Online. ISSN 2405-8963. p. 181–186. doi: 10.1016/j.ifacol.2019.11.671. Full text in Research Archive
• Ruderman, Michael (2019). On Switching between Motion and Force Control, IEEE 27th Mediterranean Conference on Control and Automation (MED'19) . IEEE conference proceedings. ISSN 978-1-5386-7890-9. p. 445–450. doi: 10.1109/MED.2019.8798545. Full text in Research Archive
• Seki, Kenta; Hirata, Jun-ya; Ruderman, Michael & Iwasaki, Makoto (2019). Creep Modeling with Time-dependent Damping Parameters in Piezoelectric Actuators, IEEE 2019 International Conference on Mechatronics. IEEE conference proceedings. ISSN 978-1-5386-6959-4. p. 135–140. doi: 10.1109/ICMECH.2019.8722864.
• Tavares, Rafael Pinto & Ruderman, Michael (2019). On Energy Harvesting Using Piezoelectric Transducer with Two-Port Model under Force Excitation, IEEE 2019 International Conference on Mechatronics. IEEE conference proceedings. ISSN 978-1-5386-6959-4. p. 414–419. doi: 10.1109/ICMECH.2019.8722871. Full text in Research Archive
• Pasolli, Philipp Thomas & Ruderman, Michael (2019). Hybrid State Feedback Position-Force Control of Hydraulic Cylinder, IEEE 2019 International Conference on Mechatronics. IEEE conference proceedings. ISSN 978-1-5386-6959-4. p. 54–59. doi: 10.1109/icmech.2019.8722829. Full text in Research Archive
• Ruderman, Michael; Yamada, Shota & Fujimoto, Hiroshi (2019). Backlash Identification in Two-Mass Systems by Delayed Relay Feedback. Journal of Dynamic Systems Measurement, and Control. ISSN 0022-0434. 141(6). doi: 10.1115/1.4042672. Full text in Research Archive
• Pasolli, Philipp Thomas & Ruderman, Michael (2019). Design, Control, and Analysis of Nonlinear Circuits with Tunnel Diode with Piecewise Affine Dynamics. IEEJ Journal of Industry Applications. ISSN 2187-1094. 8(2), p. 240–249. doi: 10.1541/ieejjia.8.240.
• Ruderman, Michael (2019). Relay feedback systems - established approaches and new perspectives for application. IEEJ Journal of Industry Applications. ISSN 2187-1094. 8(2), p. 271–278. doi: 10.1541/ieejjia.8.271. Full text in Research Archive
• Pasolli, Philipp Thomas & Ruderman, Michael (2018). Linearized Piecewise Affine in Control and States Hydraulic System: Modeling and Identification, 44th Annual Conference of the IEEE Industrial Electronics Society (IECON2018). IEEE conference proceedings. ISSN 978-1-5090-6684-1. p. 4537–4544. doi: 10.1109/IECON.2018.8591572. Full text in Research Archive
• Ruderman, Michael & Rachinskii, Dmitrii (2018). Discrete-time adaptive hysteresis filter for parallel computing and recursive identification of Preisach model, 2nd IEEE Conference on Control Technology and Applications. IEEE conference proceedings. ISSN 9781538676974. p. 1096–1101. doi: 10.1109/CCTA.2018.8511459. Full text in Research Archive
• Ruderman, Michael & Fridman, Leonid (2018). Use of second-order sliding mode observer for low-accuracy sensing in hydraulic machines, IEEE 15th International Workshop on Variable Structure Systems and Sliding Mode Control (VSS18). IEEE conference proceedings. ISSN 978-1-4673-9788-9. p. 315–318. doi: 10.1109/VSS.2018.8460227. Full text in Research Archive
• Karimi, Wais; Ruderman, Michael; Seki, Kenta & Iwasaki, Makoto (2018). Experimental framework of traveling trolley with swinging load for hybrid motion control, Proceeding of IEEE 15th International Workshop on Advanced Motion Control (AMC2018). IEEE conference proceedings. ISSN 978-1-5386-1946-9. p. 60–65. doi: 10.1109/AMC.2019.8371063. Full text in Research Archive
• Ruderman, Michael (2018). Minimal-model for robust control design of large-scale hydraulic machines, Proceeding of IEEE 15th International Workshop on Advanced Motion Control (AMC2018). IEEE conference proceedings. ISSN 978-1-5386-1946-9. p. 397–401. doi: 10.1109/AMC.2019.8371125. Full text in Research Archive
• Yamada, Shota; Ruderman, Michael & Fujimoto, Hiroshi (2018). Piecewise Affine (PWA) Modeling and Switched Damping Control of Two-Inertia Systems with Backlash, Proceeding of IEEE 15th International Workshop on Advanced Motion Control (AMC2018). IEEE conference proceedings. ISSN 978-1-5386-1946-9. p. 479–484. doi: 10.1109/AMC.2019.8371140. Full text in Research Archive
• Pasolli, Philipp Thomas & Ruderman, Michael (2018). Design and Analysis of non-linear Circuit with Tunnel Diode for Hybrid Control Systems, Proceeding of IEEE 15th International Workshop on Advanced Motion Control (AMC2018). IEEE conference proceedings. ISSN 978-1-5386-1946-9. p. 181–186. doi: 10.1109/AMC.2019.8371084. Full text in Research Archive
• Ivanov, Valentin; Augsburg, Klaus; Ruderman, Michael; Schiffer, Johannes & Horn, Martin (2017). Interdisciplinary Design Methodology for Systems of Mechatronic Systems: Focus on Highly Dynamic Environmental Applications, 43rd Annual Conference of the IEEE Industrial Electronics Society (IECON2017). IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-5090-3474-1. p. 4062–4067. doi: 10.1109/IECON.2017.8216696.
• Ruderman, Michael (2017). Full- and Reduced-order Model of Hydraulic Cylinder for Motion Control, 43rd Annual Conference of the IEEE Industrial Electronics Society (IECON2017). IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-5090-3474-1. p. 7275–7280. doi: 10.1109/IECON.2017.8217274. Full text in Research Archive
• Ruderman, Michael (2017). Impulse-Based Hybrid Motion Control, 43rd Annual Conference of the IEEE Industrial Electronics Society (IECON2017). IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-5090-3474-1. p. 4049–4054. doi: 10.1109/IECON.2017.8216694. Full text in Research Archive
• Rudolfsen, Morten H.; Aune, Teodor N.; Auklend, Oddgeir; Aarland, Leif Tore & Ruderman, Michael (2017). Identification and Control Design for Path Tracking of Hydraulic Loader Crane, Proceedings: IEEE International Conference on Advanced Intelligent Mechatronics (AIM 2017). IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781509020669. p. 565–570. doi: 10.1109/AIM.2017.8014077.
• Ruderman, Michael (2017). On break-away forces in actuated motion systems with nonlinear friction. Mechatronics (Oxford). ISSN 0957-4158. 44, p. 1–5. doi: 10.1016/j.mechatronics.2017.03.007. Full text in Research Archive Show summary

  The phenomenon of so-called break-away forces, as maximal actuation forces at which a sticking system begins to slide and thus passes over to a steady (macro) motion, is well known from the engineering practice but still less understood in its cause-effect relationship. This note analyzes the break-away behavior of systems with nonlinear friction, which is well-describable analytically by combining the Coulomb friction law with the rate-independent presliding transitions and, when necessary, Stribeck effect of the velocity-weakening steady-state curve. The break-away conditions are brought into an analytic form of the system description and shown to be in accord with a relationship between the varying break-away force and actuation force rate – that is observable in experiments reported in various independently published works.

• Ruderman, Michael & Rachinskii, Dmitrii (2017). Use of Prandtl-Ishlinskii hysteresis operators for Coulomb friction modeling with presliding. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 811(1). doi: 10.1088/1742-6596/811/1/012013. Show summary

  Prandtl-Ishlinskii stop-type hysteresis operators allow for modeling elasto-plasticity in the relative stress-strain coordinates including the saturation level of the residual constant-tension flow. This lies in direct equivalence to the force-displacement characteristics of nonlinear Coulomb friction, whose constant average value at unidirectional motion depends on the motion sign only, after the transient presliding phase at each motion reversal. In this work, we analyze and demonstrate the use of Prandtl-Ishlinskii operators for modeling the Coulomb friction with presliding phase. No viscous i.e. velocity-dependent component is considered at this stage, and the constant damping rate of the Coulomb friction is combined with the rate-independent losses of presliding hysteresis. The general case of Prandtl-Ishlinskii operator with a continuous distribution function is considered together with a finite elements case, which is useful for implementation in multiple applications. Finally, identification of parameters is addressed and discussed along with two experimental examples.

• Ruderman, Michael (2016). On stability and robustness of Virtual Torsion Sensor (VTS) for flexible joint robots, 42nd Annual Conference of the IEEE Industrial Electronics Society (IECON2016). IEEE conference proceedings. ISSN 978-1-5090-3474-1. p. 6894–6898. doi: 10.1109/IECON.2016.7793907.
• Ruderman, Michael (2016). Integral Control Action in Precise Positioning Systems with Friction. In Pogromsky, A. (Eds.), 12th IFAC International Workshop on Adaptation and Learning in Control and Signal Processing. IFAC Papers Online. ISSN 978-3-902823-37-3. p. 82–86. doi: 10.1016/j.ifacol.2016.07.931. Full text in Research Archive Show summary

  For high precision positioning systems a fast and accurate settling to the reference state is most significant and, at the same time, challenging from the control point of view. Traditional use of an integral coaction in feedback can attain a desired reference tracking at steady-state motion, but can fail in case of precise positioning. Most crucial is that this is independent on how accurate the integral control part is tuned. This paper addresses the feedback control action in precise positioning systems with friction. Analyzing the closed-loop control dynamics with nonlinear friction in feedback it is shown why the integral action cannot efficiently cope with Coulomb friction which becomes time-varying at motion onsets and reversals. The latter leads to the reduced control performance expressed in desired immediate stop at the reference position. The nature of presliding friction as functional of positioning control error, in vicinity to the reference position, and not as function of the time argument, is postulated as main disturbing factor that limits efficiency of the integral control coaction. The conclusions drawn in performed analysis are also reinforced by the demonstrated numerical examples of a controlled motion with nonlinear friction.

• Rachinskii, Dmitrii & Ruderman, Michael (2016). Convergence of direct recursive algorithm for identification of preisach hysteresis model with stochastic input. SIAM Journal on Applied Mathematics. ISSN 0036-1399. 76(4), p. 1270–1295. doi: 10.1137/140986633. Show summary

  We consider a recursive iterative algorithm for identification of parameters of the Preisach model, one of the most commonly used models of hysteretic input-output relationships. This online algorithm uses a simple rule for updating the values of the piecewise constant density function in the switching region at each time step. The so-called persistent excitation condition has been shown to play an important role for convergence of recursive iteration schemes when input-output data are generated by a deterministic input (such as, for example, a periodically repeated sequence of test inputs prescribed by the classical Mayergoyz identification algorithm). In this work, we assume that the input randomly fluctuates and these fluctuations can be described by a stochastic Markov process. Assuming that accurate measurements of the input and output are available, we prove the exponential convergence of the recursive identification algorithm, estimate explicitly the convergence rate, and explore which properties of the stochastic input and the algorithm affect the guaranteed convergence rate. An analogue of the persistent excitation condition suitable for analysis of stochastic Markov inputs is established. Numerical examples that test the convergence of the algorithm in the case of a time-dependent density function and in the presence of measurement noise are presented.

• Ruderman, Michael (2016). Compensation of Nonlinear Torsion in Flexible Joint Robots: Comparison of Two Approaches. IEEE transactions on industrial electronics (1982. Print). ISSN 0278-0046. 63(9), p. 5744–5751. doi: 10.1109/TIE.2016.2574299. Show summary

  Flexible joint robots, in particularly those equipped with harmonic drive gears, can feature torsional elasticities with hysteresis. Under heavy loads and large joint torques the hysteresis lost motion can lead to the control errors when reference tracking and positioning of robotic links. In this paper, two approaches for compensating the nonlinear joint torsion with hysteresis are described and compared with each other. Both methods assume the measured states only available on the motor side of the joint transmission. The first approach assumes a rigid-link manipulator model and transforms the desired link trajectory into that of the motor drives by using the inverse of dynamics and hysteresis map. This is inspired by former works on robotic manipulators with linear joint elasticities and extended to the general nonlinear case. The second approach, introduced previously and revised here with further analysis, relies on the modeling of motor drives and inverse hysteresis map and uses generalized momenta for the torque prediction. Both methods are discussed in detail along with numerical example of the two-link planar manipulator under gravity.

• Ruderman, Michael & Iwasaki, Makoto (2016). On damping characteristics of frictional hysteresis in pre-sliding range. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 727(1). doi: 10.1088/1742-6596/727/1/012014.
• Ruderman, Michael & Iwasaki, Makoto (2016). Analysis of Linear Feedback Position Control in Presence of Presliding Friction. IEEJ Journal of Industry Applications. ISSN 2187-1094. 5(2), p. 61–68. doi: 10.1541/ieejjia.5.61.

View all works in Cristin

• Ruderman, Michael & Seki, Kenta (2024). IEEE AMC2024 conference proceeding. IEEE conference proceedings. ISBN 979-8-3503-4281-9. 660 p.
• Ruderman, Michael (2023). Analysis and Compensation of Kinetic Friction in Robotic and Mechatronic Control Systems. CRC Press. ISBN 9781032539454. 67 p. Show summary

  This book comprehensively covers kinetic friction in a robotics, mechatronics, and control engineering context. Providing the theory behind kinetic friction, as well as compensation methods and practical solutions, the book is a key companion to studying different control systems. Beginning with a clear introduction to the subject, the book goes on to include three main facets of kinetic friction, starting with phenomena of kinetic friction in drives. This chapter explains friction interfaces and friction effects. Following on from this, the next chapter looks at motion dynamics with friction, which introduces dynamic system equations and focuses on both energy balance and dissipation. Finally, the book looks at compensation of friction in motion control, which summarises key compensation methods in controlled mechanical systems. Introducing various basic feedback control methods, including observer-based methods to compensate for kinetic friction, the book provides practical information which can be used in a wide variety of contexts not specific to particular systems or applications. The book will be of interest to students and industry workers in the field of robotics, mechanical systems and control engineering.

• Ruderman, Michael & Chen, Wen-Hua (2023). Proceeding IEEE International Conference on Mechatronics (ICM2023). IEEE conference proceedings. ISBN 978-1-6654-6661-5. 450 p.
• Ruderman, Michael & Tsuji, Toshiaki (2021). 2021 IEEE International Conference on Mechatronics (ICM). IEEE conference proceedings. ISBN 978-1-7281-4443-6. 650 p.
• Tsuji, Toshiaki; Ruderman, Michael; Fujimoto, Hiroshi & Ivanov, Valentin (2021). Proceeding of IEEE International Conference on Mechatronics (ICM2021). IEEE conference proceedings. ISBN 978-1-5386-6959-4.
• Ruderman, Michael; Pavlov, Alexey & Iwasaki, Makoto (2020). Proceeding of IEEE International Workshop on Advanced Motion Control (AMC2020). IEEE conference proceedings. ISBN 978-1-7281-3189-4.
• Ruderman, Michael (2019). IEEE 2019 International Conference on Mechatronics. IEEE conference proceedings. ISBN 978-1-5386-6959-4.
• Fujimoto, Yasutaka; Ruderman, Michael; Uchimura, Yutaka & Ohishi, Kiyoshi (2018). Proceeding of IEEE 15th International Workshop on Advanced Motion Control (AMC2018). IEEE conference proceedings. ISBN 978-1-5386-1946-9. 682 p.

View all works in Cristin

• Ruderman, Michael (2024). Seminar: Robustly estimating and compensating uncertain oscillatory output.
• Ruderman, Michael (2024). Robustly estimating and compensating uncertain oscillatory output. Show summary

  Oscillatory quantities occur in almost all types of the processes, for instance mechanical vibrations, electric and power circuits, electromagnetic waves, bio-medical signals, and others. Often, an oscillatory output state must first be estimated, in particular regarding the unknown and/or time varying frequency, and then compensated for in a robust manner. A general problem with physical oscillatory signals is that they can be biased, have time-varying parameters, and can also be influenced by noise. Moreover, there is often only a limited set of the state variables available from the sensors to compensate for oscillatory behavior. In the worst case, only an output feedback value can be used for control in the applications, while the internal dynamic states cannot be measured or accurately observed. This talk will illustrate how a robust estimation of the unknown and even varying frequency, proposed in [1], can be combined with the time-delay based output feedback control of the low-damped oscillations, provided in [2]. Since both the robust frequency estimator [1] and output oscillations compensator [2] are independent from each other in analysis and design, the former can be used as a plug-in, thus making the whole compensation scheme truly adaptive [3]. We will first present and examine both approaches and then evaluate their interaction on a real experimental system with noisy measurements and additional process noise. Some additional aspects of parameter tuning and constraints limiting applicability will also be demonstrated, theoretically and based on experimental observations, and brought into a concluding discussion.

• Ruderman, Michael (2024). Understanding kinetic friction and its control related challenges. Show summary

  Kinetic friction occurs wherever two mechanical parts are in physical contact and there is relative motion between the two. Our engineering understanding of the Coulomb and viscous friction go back to the classical one- (or maximal two-) lumped parameter models, while the overall resulting dynamics of actuated bodies with friction is always non-trivial for analysis, identification and, especially, control. Despite more sophisticated heuristic dynamic friction models (with more parameters and internal unmeasurable states) are also available, they are not always helpful in mastering the kinetic friction. This talk will provide a brief introduction to the main context and assumptions related to kinetic friction, focusing on the linear viscous and nonlinear Coulomb friction in a one-dimensional setting of the generalized coordinates and forces. In addition to a well-understood frictional behavior at steady-state, we will pay attention especially to pre-sliding transients at the beginning and stop and reversals of relative motion. Kinetic friction will equally be considered from the perspective of energy dissipation and incorporated into the standard Lagrangian framework of dynamic system modeling. The problems associated with using the standard feedback regulators (like PD or PID) for motion with friction will be highlighted and discussed in context of convergence of an output value under control. The talk will also demonstrate several motivating numerical examples and experimental observations, picked out from the own and also from other independently published works.

• Ruderman, Michael (2023). Interplay between linear integral and discontinuous relay feedback: challenging issue for standard PI/PID controllers in presence of Coulomb friction. Show summary

  We consider linear time invariant system plants with an unbounded integral control action and discontinuous relay in feedback. Examples for that are the standard PI/PID controllers, widely used in various types of robotic and mechatronic systems. Inherent challenge of a discontinuous relay feedback can be directly associated with presence of the Coulomb friction and mechanical setups, that downgrades the convergence performance of motion control systems for set-point stabilization tasks. Other application examples in which a relay non-linearity in the loop represents part of the plant dynamics are also conceivable. As a matter of fact, a slowly converging stick-slip behavior with continuously growing periods appears in such systems, owing to an interplay between the integral feedback and relay nonlinearity. In this talk, we will look into analysis of the convergence behavior and highlight the appearance of sticking phases and set of possible trajectories in vicinity to the globally stable equilibrium and associated region of attraction. A novel solution to convergence analysis of such systems, based on the classical sliding mode principles, will be presented. Some aspects of estimating upper bound of the convergence time will also be treated at the edge. The talk will also include several motivating numerical examples and experimental observations known from the other published works.

• Lucia, Oscar; Ruderman, Michael & Chen, Wen-Hua (2023). 2023 IEEE International Conference on Mechatronics [Society News]. IEEE Industrial Electronics Magazine. ISSN 1932-4529. 17(3), p. 68–69. doi: 10.1109/MIE.2023.3300089.
• Ruderman, Michael (2023). Motion control with optimal nonlinear damping. Show summary

  In second-order feedback control systems, a linear damping enables shaping the transient response and obtaining sub-optimality in the output trajectory without transient overshoot. However, linear damping has certain limitations in performance given by the locus of double real poles. Considering a second-order feedback system from the point of view of energy balance through the control, it becomes clear what role the feedback of the output and its time derivative play. The first one is creating a potential field and supplies the system with potential energy unless the output control error becomes zero. The second one is shaping the system energy via the corresponding damping and, this way, ensures convergence to zero equilibrium. In systems with linear damping, the asymptotic convergence slows down near zero equilibrium, according to the exponential behavior. For improving transient and convergence performance of the feedback controlled second-order systems, the nonlinear damping control was proposed in [1,2]. This talk will summarize that so-called optimal nonlinear damping control, discuss its principal properties, and show some further developments and experimental evaluation results [3]. Several open questions of interest for future research will also be discussed along with practical challenges of the motion control. References: [1] Optimal nonlinear damping control of second-order systems. M. Ruderman. Journal of The Franklin Institute, Vol 358, pp 4292-4302, 2021, https://doi.org/10.1016/j.jfranklin.2021.03.022 [2] Convergent dynamics of optimal nonlinear damping control. M. Ruderman. IFAC 6th Hybrid Conference on Analysis and Control of Chaotic Systems, IFAC-PapersOnLine, Vol 54(17), pp 141-144, 2021, https://doi.org/10.1016/j.ifacol.2021.11.039 [3] Motion control with optimal nonlinear damping: from theory to experiment. M. Ruderman. Control Engineering Practice, Vol 127, pp 105310, 2022, https://doi.org/10.1016/j.conengprac.2022.105310

• Nguyen, Anh-Tuan; Quang Dinh, Truong; Chong, Junjie; Iwasaki, Makoto; Precup, Radu-Emil & Ruderman, Michael (2023). Guest editorial introduction to the special issue on “Emerging control and automation technologies for advanced mechatronic systems”. Control Engineering Practice. ISSN 0967-0661. 136. doi: 10.1016/j.conengprac.2023.105532.
• Ruderman, Michael (2023). Motion control with optimal nonlinear damping and convergent dynamics. Show summary

  In second-order feedback control systems, a linear damping enables shaping the transient response and obtaining sub-optimality in the output trajectory without transient overshoot. However, linear damping has certain limitations in performance given by the locus of double real poles. This talk will summarize the recently developed optimal nonlinear damping control, discuss its principal properties, and show some theoretical and experimental results.

• Ruderman, Michael (2022). Constrained input modulation for impulse-based motion control.
• Ruderman, Michael (2022). Application of motion control with optimal nonlinear damping and convergent dynamics.
• Ruderman, Michael (2022). Energy dissipation and hysteresis cycles in pre-sliding transients of kinetic friction.
• Ruderman, Michael (2021). Modeling and control of kinetic friction for robotics.
• Ruderman, Michael (2020). Nonlinear damping in system dynamics and control. Show summary

  Damping is a natural way to extract energy from an autonomous, to say isolated, dynamic system. Physically it means an irreversible dissipation process, mostly through heat transfer, while in the control systems it is inherently associated with stabilization of the state solutions, correspondingly convergence to a stable equilibrium. Nonlinear damping is relevant but, at the same time, not trivial for both – analysis and modeling of the dynamic systems and controller synthesis for their efficient regulation. This talk, devoted to nonlinear damping, will consist of two parts. In the first one, we will analyze some nonlinear damping phenomena, while focusing on rate-independent (sometimes called structural or hysteresis) damping and discussing dissipation power, local stabilizing properties, and invariant sets of equilibria. The second part of the talk will discuss nonlinear damping in the feedback control, with focus on the phase-plane analysis of solution trajectories. A novel nonlinear damping control with optimal convergence without transient overshoot will also be illustrated in detail.

• Ruderman, Michael; Kaltenbacher, Stefan & Horn, Martin (2020). Pressure-flow dynamics with semi-stable limit cycles in hydraulic cylinder circuits.
• Molina, Juan; Tavares, Rafael Pinto; Al Sakka, Monzer; Ruderman, Michael & Dhaens, Miguel (2019). Industrial Mathematics at DRiV TM.
• Indri, Marina; Grau, Antoni M. & Ruderman, Michael (2018). Guest Editorial Special Section on Recent Trends and Developments in Industry 4.0 Motivated Robotic Solutions. IEEE Transactions on Industrial Informatics. ISSN 1551-3203. 14(4), p. 1677–1680. doi: 10.1109/TII.2018.2809000.
• Ruderman, Michael (2018). Relay feedback systems – established approaches and new perspectives for application. Show summary

  Feedback relay systems belong to the classical topics of control theory and engineering. For more than two decades, the simple and robust auto-tuning techniques with relay feedback have been developed for industrial controllers and integrated in various applications. Remarkable feature of using the relays in feedback control systems is arising of limits cycles. For the provable conditions, the stable limit cycle oscillations bear signature of the plant and control system parameter and are, therefore, useful for control tuning but also detection and identification purposes. The questions of conditions of stable limit cycles, their convergence depending on initial values, controllability of the magnitude and period are the most significant for robust and efficient use of feedback relay systems. Large part of them already found answers and solutions in the former research inspired from both theoretical curiosity and application requirements. The tutorial will summarize the basic principles of feedback relay systems, mostly known in context of auto-tuning the simple controllers. Furthermore it will look towards global properties of dynamic systems with relays in feedback and disclose several typical characteristics interesting for applications. Some perspectives for use in the system identification will be addressed based on the classical examples of mass and stiffness parameters. Novel strategies for detection and estimation of hidden and weakly-known system nonlinearities will be discussed along with the recently developed method for two-mass systems with backlash.

• Ruderman, Michael (2018). On rate-independent damping, break-away, and setpoint conditions of the relative motion with dry contact interfaces. Show summary

  We discuss several phenomena and transient properties of the dry contact interfaces of the moving bodies, generally understood as indications of nonlinear friction. Rate-independent damping with the so-called presliding distance is shown to be the principal energy dissipation factor is vicinity to the motion stops and reversals. Further the break-away conditions of a relative motion onset are exemplified for the external actuation forces depending on their rates. Finally, the setpoints conditions for the feedback controlled relative motion are addressed, while revealing inherent limits of the integral control action when absolute setpoint accuracy is required. Several examples and experimental observations will be demonstrated along with analysis and theoretical interpretations.

• Ruderman, Michael; Fujimoto, Hiroshi; Yamada, Shota & Valentin, Ivanov (2017). Examples of actuator uncertainties in environmental systems of mechatronic systems (SoMS). Show summary

  The proposed concept of systems of mechatronic systems (SoMS) focuses on a methodology aimed for robust control, state estimation, and disturbance compensation in highly dynamic environmental mechatronic systems. Three interfacing topics “mechatronic chassis systems of electric vehicles”, “mechatronic-based grid-interconnection circuitry”, and “offshore mechatronics” – have been identified as comprising a series of research challenges in relation to the state and parameter estimation, disturbance observation and attenuation, and robust control design. This paper aims to highlight several examples of actuator uncertainties in environmental SoMS, in particular those used in offshore mechatronics and electric vehicles, and to promote the research activities of the collaborative project CLOVER initiated within European Unions Horizon 2020 framework programme under Marie Sklodowska-Curie actions.

• Ruderman, Michael (2017). Control seminar at UNAM (National Autonomous University of Mexico).
• Ruderman, Michael (2016). On fast parallel computation and online identification of scalar Preisach hysteresis in real time engineering applications. Show summary

  The classical scalar Preisach hysteresis model remains a significant mathematical tool for multiple engineering applications like fast prototyping design, online condition monitoring and model‐based control, respectively hysteresis compensation. We address the problem of a fast parallel computation and online identification of the scalar Preisach hysteresis based on the model formulation introduced in [1] and online identification method proposed in [2], theoretically investigated and analyzed in [3], and evaluated on an experimental example in [4]. The main issue of a real‐time implementation and application is in synchronized two‐step computation and update mechanisms which ensures deterministic calculus and parameterization of the multiple nonideal relay operators connected in parallel. We use the formalism of timed automata and algebra of sets in order to describe and evaluated the proposed algorithm.

• Ruderman, Michael & Iwasaki, Makoto (2016). Retrospection on control-oriented case study of nonlinear elasticities in wave-motion gears.
• Pasolli, Philipp Thomas & Ruderman, Michael (2020). Hybrid modeling and control of mechatronic systems using a piecewise affine dynamics approach. Media 07. ISSN 978-82-7117-974-8. Full text in Research Archive Show summary

  Every physical system contains non-linear characteristics. When the system becomes increasingly complex, the number of non-linearities rises accordingly, which makes operating the system as desired a challenge. Thus finding a suitable control structure, tuning controller gains and evaluating the system with regard to response and stability requires a high level of in-depth knowledge about the system itself as well as the topology of modeling, identification and control. One approach to simplify this process is to linearize the system around a specified operational point. However, this will result in a model which is only representative of the physical system in the vicinity of said operation point and therefore accurately represents only a small subset of the system’s operational state-space. On the other side of the spectrum are models with high complexity, in future referred to as full-order models. These include full-order dynamics, non-linearities, etc., all of which require explicit knowledge of the system { including its characteristics and internal states { which might not be feasible to obtain. If generated, these models provide a highly accurate system representation. Introducing the topology of hybrid systems in recent years, especially its subclass of piecewise affine (PWA) systems, appears to be one class of systems capable of representing the middle ground with respect to complexity between a model linearized around an operational point and a full-order model. It allows for a linearization of a non-linear characteristic at several points, resulting in the characteristic being expressed as a combination of different cells defined by linear functions. The compliance between linearized and actual characteristics can also be easily customized by adjusting the number and locations of linearization points. This thesis investigates the topic of modeling and control of PWA systems based on two experimental cases of an electrical and hydraulic nature with varying complexity that were also built, instrumented and evaluated. A full-order model has been created for both systems, including all dominant system dynamics and non-linearities. The unknown parameters and characteristics have been identified via an extensive parameter identification. In the following, the non-linear characteristics are linearized at several points, resulting in PWA models for each respective setup. Regarding the closed loop control of the generated models and corresponding experimental setups, a linear control structure comprised of integral error, feed-forward and state-feedback control has been used. Additionally, the hydraulic setup has been controlled in an autonomous hybrid position/force control mode, resulting in a switched system with each mode’s dynamics being defined by the previously derived PWA-based model in combination with the control structure and respective mode-dependent controller gains. The autonomous switch between control modes has been defined by a switching event capable of consistently switching between modes in a deterministic manner despite the noise-afflicted measurements. Several methods were used to obtain suitable controller gains, including optimization routines and pole placement. Validation of the system’s fast and accurate response was obtained through simulations and experimental evaluation. The controlled system’s local stability was proven for regions in state-space associated with operational points by using pole-zero analysis. The stability of the hybrid control approach was proven by using multiple Lyapunov functions for the investigated test scenarios.

View all works in Cristin