access icon free Trust-region reflective adaptive controller for time varying systems

The new algorithm presented in this study, called TRAC (trust-region reflective adaptive controller), performs online adaptive control of time-varying linear or linearisable systems subject to parametric disturbances. The process of accomplishing such adaptive control consists of feeding the measured output signal back to TRAC – which occupies the outer loop of a control scheme – as well as the reference signal. Knowing the order of the closed-loop system in the inner loop, a parametric model of the time-varying output is derived as a function of the system's variables, such as damping and natural frequencies. Using trust-region optimisation, these parameters are estimated in real-time by recursively fitting the actual output into the parametric model. This allows for the location of the actual poles to be estimated in the s-domain after the poles have been shifted by the disturbance. Accordingly, the gains are re-tuned in order to return the actual poles to their desired location and absorb the disturbance. The primary advantage of TRAC relative to the state-of-the-art is its computational simplicity which is owed to search space restriction and heuristic approximations with trust-region search. A video of a sample application describing real-time TRAC-based control can be found on the IET's Digital Library.

Inspec keywords: linear systems; time-varying systems; closed loop systems; optimisation; search problems; adaptive control; approximation theory

Other keywords: linearisable system; online adaptive control; parametric disturbance; natural frequencies; trust-region optimisation; closed-loop system; damping; trust-region reflective adaptive controller; time varying linear system; heuristic approximation; TRAC; search space restriction; trust-region search

Subjects: Optimisation techniques; Interpolation and function approximation (numerical analysis); Time-varying control systems; Self-adjusting control systems

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