There are three gains to adjust in the P.I .D. controller, Kp, Ki and Kd. These gains all act on the position
error defined in (4). Note the superscript "* " refers to a commanded value. error(t) = q* (t )- q(t ) (4)
The output of the P.I .D. controller is a torque signal. I ts mathematical expression in the time domain is
given in (5). . . . ( ) = p ( ( )) + i ò( ( )) + d ( ( )) We now look at how one selects the gains, Kp, Ki and Kd.