Adaptive control is now finding its way into the marketplace after many years of effort. This paper reviews some ideas used to design adaptive control systems. It covers early ideas which primarily attempt to compensate for gain variations and more general methods like gain scheduling, model reference adaptive control, and self-tuning regulators. It is shown that adaptive control laws can be obtained using stochastic control theory. Techniques for analyzing adaptive systems are discussed. This covers stability and convergence analysis. Issues of importance for applications like parameterization, tuning, and tracking, as well as different ways of using adaptive control are also discussed. An overview of applications which includes feasibility studies as well as products based on adaptive techniques concludes the paper.

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Adaptive feedback control

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Adaptive Feedback Control

Robust low level control of robotic excavation

Due to the properties such as small size-to-power ratio, large force output capability and fast response, the hydraulic position servo system is widely used in industrial automation fields High-pr

Adaptive control of hydraulic position servo system using output feedback

A continuous-time robust indirect adaptive control (IAC) algorithm with a self-excitation capability is proposed for position control of an electrohydraulic servo system subject to parametric uncertainties and load disturbances. In this algorithm, a gradient least squares dead zone estimation is used to identify the plant parameters and then a linear pole-placement controller is designed using the estimate. By a coprimeness verification procedure, the proposed algorithm facilitates the establishment of the adaptive pole-placement control of the closed-loop system by using an additional nonlinear feedback signal implemented for supplying the system with sufficiently rich signals. An analysis shows this algorithm can guarantee parameter estimation convergence and system stability based on the certainty equivalence principle. The performance of the proposed algorithm is evaluated through both the simulation results and the experimental studies. Simulations and experiments are conducted to see how well the proposed algorithm compares with two existing control schemes in controlling the same process. The results show that the IAC scheme confirms the analysis and has considerable robustness subject to parametric uncertainties and load disturbances and has better performance than the other two controllers.

Continuous-time indirect adaptive control of the electrohydraulic servo systems

In a hydraulic system input/output relation of the control valve is nonlinear and load dependent. An adaptive control would therefore be necessary for large changes in load parameter. The paper considers a position control system. This becomes a third order system under inertia load and with compressibility of oil considered. Load pressure and integration of the load pressure are suggested as additional feedbacks. PRBS is used as the input signal and the cross-corelation technique is used for identification of the impulse response. Performance parameters are defined and then they are brought to their respective model parameters by iteratively adjusting the gains of the additional feedback loops. An 8-bit microprocessor based system has been used for identification and control. The proposal seems practical and can be economically implemented.

An Adaptive Control of an Electro-Hydraulic Position Control System

The paper proposes a scheme for implementing an adaptive controller design based on Lyapunov stability critarion. Aircraft T.F. consisting of one zero and a complex conjugate pair of poles is considered. The model has also similar structure but the poles are based on HQR considerations. The controller uses analog filters for generating derivatives whereas the parameters are computed and updated by a digital means. The scheme is thus differentiator free. The performance of the scheme has been evaluated by simulating aircraft dynamics plus filters on an Analog computer and then interfacing it to a general purpose Instrumentation & Control digital computer. The results show satisfactory response under widely different Aircraft T.F. including one having an unstable pole.

J. Chandrasekhar

Papers

An Adaptive Control of an Electro-Hydraulic Position Control System

An MRAC System for Aircraft Longitudinal Control