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Principles of lossless adjustable one-ports

Accepted version
Peer-reviewed

Type

Article

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Authors

Smith, Malcolm 
Georgiou, Tryphon T 
Jabbari, Faryar 

Abstract

This paper explores the possibility to construct two- terminal mechanical devices (one-ports) which are lossless and adjustable. To be lossless, the device must be passive (i.e. not requiring a power supply) and non-dissipative. To be adjustable, a parameter of the device should be freely variable in real time as a control input. For the simplest lossless one ports, the spring and inerter, the question is whether the stiffness and inertance may be varied freely in a lossless manner. We will show that the typical laws which have been proposed for adjustable springs and inerters are necessarily active and that it is not straightforward to modify them to achieve losslessness, or indeed passivity. By means of a physical construction using a lever with moveable fulcrum we will derive device laws for adjustable springs and inerters which satisfy a formal definition of losslessness. We further provide a construction method which does not require a power supply for physically realisable translational and rotary springs and inerters. The analogous questions for lossless adjustable electrical devices are examined.

Description

Keywords

Springs, Shock absorbers, Force, Valves, Control systems, Acceleration, Capacitors, Inerter, lossless, mechanical network, passivity, semiactive, variable stiffness

Journal Title

IEEE Transactions on Automatic Control

Conference Name

Journal ISSN

0018-9286
1558-2523

Volume Title

Publisher

Institute of Electrical and Electronics Engineers

Rights

All rights reserved
Sponsorship
NSF, AFOSR