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222 Computed-Torque Control

Figure 4.4.17: PID classical joint control with torque limits of ±35 N-m. Torque
inputs in N-m.

(4)

The results of the simulation with these limits are shown in Figure 4.4.16 and
are terrible. The torque is shown in Figure 4.4.17.
In Section 4.5 we show how to ameliorate the effects of actuator
saturation by using antiwindup protection in a digital controller. The
simulation results for PD control with actuator limits are not as bad as the
ones just shown for PID control, since saturation limits have less effect if
no integrator is present.

4.5 Digital Robot Control

Many robot control schemes are complicated and involve a great deal of
computation for the evaluation of nonlinear terms. Therefore, they are
implemented as digital control laws on digital signal processors (DSPs). Certain

Copyright © 2004 by Marcel Dekker, Inc.