Abstract
An adaptive control scheme for mechanical manipulators proposed. The control loop consists of a network for learning the robot's inverse dynamics and on-line generating the control signal. Some simulation results were provided to evaluate the design. A supervisor was used to improve the performances of the system during the adaptation transients. The supervisor exerts two supervisory actions. The first one consists of updating the free-design adaptive controller parameters so that the value of a quadratic loss function maintained sufficiently small. The second supervisory action consists of an on-line adjustment of the sampling period within an interval centered at its nominal value.
Highlights
The problem of designing adaptive control laws for rigid robot manipulators has interested researchers for many years
A supervisor was used to improve the performances of the system during the adaptation transients
The second supervisory action consists of an on-line adjustment of the sampling period within an interval centered at its nominal value
Summary
The problem of designing adaptive control laws for rigid robot manipulators has interested researchers for many years. Some parameters of a robot are measurable, some other effects, such as friction, mass distribution or payload variations cannot, in general, be accurately modeled and the assumption of obtaining negligible modeling errors is quite unrealistic in practice In these conditions, it looks apparent that some sort of adaptive parameter estimation mechanism should be included in the control loop, so that equation (5) became approximately linear and uncoupled and the servo errors could be asymptotically eliminated. Rule 2: If the tracking error is decreasing with respect to preceding samples decrease (increase) the last value of the sequence of the free design parameter provided that the previous action was to decrease ( increase) it . The use of a unique sample in the supervisory loop would lead, in general, to unsuitable actions when measurement failures arise or when abrupt changes in the control input appear art isolated sampling instants
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