Petter Hansen Gøytil has followed the PhD Programme at Faculty of Engineering and Science, Specialization in Engineering Sciences, scientific field Mechatronics.
- Trial lecture starts at 10:15
- Public defence starts at 12:15
Title of trial lecture: "Variable displacement and motor controlled pumps: Operating principles, efficiency characteristics, and applications"
Disputation chair: Paul Ragnar Svennevig
Assessment committee:
- First opponent Professor Petter Krus, Linköping University
- Second opponent Professor Dr. Gudrun Mikota, Johannes Kepler University, Austria
- Head of assessment committee: Professor Rein Terje Thorstensen
Supervisors in the doctoral work:
- Main supervisor: Professor Michael Rygaard Hansen, UiA
- Co-supervisor: Damiano Padovani
Summary of thesis
With increasing demands for more energy efficient solutions, and the impressive development of modern electric drives, pressure is on the hydraulic community to produce solutions more suitable for the modern market. Pump-controlled cylinders are emerging as a promising candidate in this regard, and have already found their way into many real-life applications. Feedback control is often required in practical applications, and has been employed extensively and been well understood for valve-controlled cylinders since the 1950s and 1960s. The dynamics of pump-controlled cylinders, however, differ from that of traditional valve-controlled systems, and several challenges arise regarding their employment in feedback control applications, not faced previously with traditional valve-controlled systems.
Depending on the selected hydraulic architecture, problems may arise even before closing a feedback around the system. As an example, consider the problem of applying pump-control to a single-rod cylinder utilizing a single hydraulic pump. Although simple solutions are available for this, the majority of them have been shown to exhibit unstable behavior for certain operating conditions, even in the absence of feedback control, leading to loss of performance and potentially dangerous situations. This gives rise to the use of dual-pump solutions, but also here the designer is faced with numerous challenges. One problem common to both single- and dual-pump solutions arises from the drastic reduction in the pressure levels found in these systems, relative to valve-controlled systems, which may lead to significant decreases in the effective bulk modulus of the fluid and thus potentially drastic reductions in the achievable performance under feedback control. Additionally, the actuating element found in traditional valve-controlled cylinders, consisting of a small metal spool controlled by means of an electromagnetic solenoid, has now been replaced by a much larger electric motor. This gives rise to a number of new challenges pertaining to modeling, identification and control of these systems.
In this dissertation, the use of pump-controlled cylinders in feedback control applications is studied. Based on a review of the existing literature, a number of research gaps are identified that should be addressed prior to extensive employment of these systems in feedback control applications. Five publications are devoted to the topic, in an attempt to fill these gaps and answer the questions that arise from them. The primary goal of the dissertation is to clarify what special considerations must be made for the employment of pump-controlled cylinders in feedback control applications and how these may be addressed, focusing on performance, stability, energy efficiency as well as modeling and control design.
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The disputation is open to the public. To follow the trial lecture and the public defence online, register on Zoom.
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Opponent ex auditorio:
Deadline for the public to pose questions is during the break between the two opponents. Questions ex auditorio can be submitted to Kristine Evensen Reinfjord.
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