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O'Connor, William
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O'Connor, William
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O'Connor, William
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- PublicationWave-Echo Control of Lumped Flexible SystemsAn elegant, generic solution is presented to the problem of point-to-point control by a single actuator of a remote load through an intermediate flexible system, modelled by a system of lumped masses and springs. It is based on new ways of looking at the problem that respect and exploit the underlying dynamics. Under wide-ranging conditions the strategy allows rapid, almost-vibrationless, precise position control of the load, independently of the order of the system, without the need for a detailed system model or ideal actuator. During the start-up, the system itself reveals to the controller how to terminate the motion, so that the real system also acts as the model for the controller. The scheme is very robust to modelling, actuator and sensor errors. The strategy is presented, with some of the motivating ideas reviewed.
Scopus© Citations 34 625 - PublicationWave-based control of under-actuated flexible structures with strong external disturbing forcesWave-based control of under-actuated, flexible systems has many advantages over other methods. It considers actuator motion as launching a mechanical wave into the flexible system which it absorbs on its return to the actuator. The launching and absorbing proceed simultaneously. This simple, intuitive idea leads to robust, generic, highly efficient, precise, adaptable controllers, allowing rapid and almost vibrationless re-positioning of the system, using only sensors collocated at the actuator-system interface. It has been very successfully applied to simple systems such as mass-spring strings, systems of Euler-Bernoulli beams, planar mass-spring arrays, and flexible three-dimensional space structures undergoing slewing motion. In common with most other approaches, this work also assumed that, during a change of position, the forces from the environment were negligible in comparison with internal forces and torques. This assumption is not always valid. Strong external forces considerably complicate the flexible control problem, especially when unknown, unexpected or unmodelled. The current work extends the wave-based strategy to systems experiencing significant external disturbing forces, whether enduring or transient. The work also provides further robustness to sensor errors. The strategy has the controller learn about the disturbances and compensate for them, yet without needing new sensors, measurements or models beyond those of standard wave-based control.
374Scopus© Citations 7 - PublicationWave-based control of non-linear flexible mechanical systems(Springer Netherlands, 2009-07)
; ; ; The need to achieve rapid and accurate position control of a system end-point by an actuator working through a flexible system arises frequently, in cases from space structures to disk drive heads, from medical mechanisms to long-arm manipulators, from cranes to special robots. The system’s actuator must then attempt to reconcile two, potentially conflicting, demands: position control and active vibration damping. Somehow each must be achieved while respecting the other’s requirements. Wave-based control is a powerful solution with many advantages over previous techniques. The central idea is to consider the actuator motion as launching mechanical waves into the flexible system while simultaneously absorbing returning waves. This simple, intuitive idea leads to robust, generic, highly efficient, adaptable controllers, allowing rapid and almost vibrationless re-positioning of the remote load (tip mass). This gives a generic, high-performance solution to this important problem that does not depend on an accurate system model or near-ideal actuator behaviour. At first sight wave-based control assumes superposition and therefore linearity. This paper shows that wave-based control is also robust (or can easily be made robust) to non-linear behaviour associated with non-linear elasticity and with large-deflection effects.1452Scopus© Citations 30