  This paper presents a multi-objective digital PID controller design method
using the parameter space approach of robust control. Absolute stability is
treated first by finding the digital PID controller gain parameter space
corresponding to closed loop poles being inside the unit circle. Phase margin,
gain margin and a mixed sensitivity bound are treated as frequency domain
constraints. Determination of digital PID controller parameter space regions
satisfying these constraints is presented. All of these regions are
superimposed to obtain a multi-objective digital PID controller gain parameter
space solution region. The path following controller design of an automated
driving vehicle is used as an example to illustrate the method.
