Torque compensation for angle designation controller using analog rate loop

This paper proposes a torque disturbance compensator for a digital controlled angle designation loop that uses an analog rate loop with proportional gain as an inner loop in anti-backlash geared platform. This is basically designed as alternative scheme based on conventional disturbance observer so as to be adopted in the analog rate loop where measurable state variables are limited. The stabilities for linear closed-loop, and for internal disturbance with nonlinear characteristics are, respectively, evaluated by Nyquist Diagram, and extended Nyquist criterion which uses a relay-type describing function. The design guideline to make the angle designation loop robust is presented step by step. In the end, the improved performances in real plant are demonstrated by experimental results of both frequency and time responses.