Generalised predictive control with input constraints

Abstract

Generalised predictive control (GPC), which has been shown to be effective for the selftuning control of complex plant, is based on the minimisation of a long-range cost function. In previous work this has been achieved by an analytic solution which is not valid if there are constraints on the input control signals. A simple extension is proposed which caters for rate or amplitude limits, and simulations show the corresponding improvements in closed-loop performance that can be achieved. A common problem, in practice, is the effect of torque saturation in DC motor drives: results from a compliant link, where the control sample-rate is 60Hz, show that the proposed method overcomes this and is also computationally acceptable. Bang-bang control, a limiting case of constrained inputs, is also treated within the GPC framework