A Unit-Gain D-type Iterative Learning Control Scheme: Application to a 6-DOF Robot Manipulator

In this paper, a novel method to realize a unit-gain feature in iterative learning control (ILC) is proposed, using both forward and backward filtering. Based on this method, a unit-gain derivative is proposed as a remedy to the undesirable high gain feature of the conventional derivative at high frequency. The scheme is equivalent to an all-pass unit-gain phase shifter; the forward altering uses a 0.5-order derivative and the backward filtering employs a 0.5-order integral. The all-pass phase shifter is then deployed in a unit-gain D-type ILC. For implementation, frequency-band synthesis of non-integer differentiator is introduced. The effectiveness of the unit-gain D-type ILC is demonstrated by experimental results on a 6 DOF robot manipulator.