Analysis of Lossless-Adjustable One-Ports: Experimental Testing, Modelling and Optimal Control

This thesis presents the novel developments for the field studying lossless-adjustable elements and the networks that contain them. First, the optimal control theory is developed for a generic mechanical network that contains lossless-adjustable elements. By exploiting a specific form of a block state-space representation, which is found for the class of the mentioned networks as well as the form of the performance index of interest, it is shown that by choosing the appropriate value function, the stochastic HJB equation for the system can be solved via three algebraic equations, providing the control variable stays in the non-saturated region. Building from this, a candidate law for a clipped-optimal control on an infinite horizon is proposed that can be applied practically. The clipped-optimal control law is then compared in simulation against the corresponding clipped-optimal control law for a quarter-car where semi-active damper is used to provide the control action and also where both components: semi-active damper and varspring, are used simultaneously. Different simulation profiles are evaluated that represent common operating conditions in the real world and it is shown that a performance improvement in some cases is possible when a varspring is used in a quarter-car suspension. Second, a methodology is presented to construct a block state-space representation for a generic mechanical network that contains lossless-adjustable elements. As part of the work done, a discussion of modelling methods of mechanical and electrical networks is presented and it is proposed how the methodologies established in electrical circuit theory can be applied to model mechanical networks. Furthermore, a review of eigenvalue structure at infinity of dynamical systems as well as the properties of strict-system equivalence are presented and the new relationships between the two concepts are established. Finally, the results concerning experimental testing of prototype rotary varspring are presented. Experiments to establish friction characteristics in the device are carried out. The device law of ideal varspring is modified to include friction and inertia effects. The torque, instantaneous power and energy are compared between the proposed device model and experimental data with close correlation between the two being achieved.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2023

Author dc:creator

• Gaudiesius, Lukas

Advisor dc:contributor.advisor

• Smith, Malcolm C

• lossless-adjustabe one-ports
• mechanical networks
• network synthesis
• optimal control
• semi-active suspension

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/7795cffe-d2ca-4bb0-8c0b-298aae51db61/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.115609

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/379567