Reinterpretation of PDD² compensator embedded in position control for pneumatic stage

Abstract

PDD 2 (proportional + derivative + second derivative) compensator has been standardly used for position control of the pneumatic stage. This compensator is based on the integral characteristics of a pneumatic system composed of pipes, servo valves, and pneumatic cylinders. At this time, since the output of this compensator is integrated through the pneumatic system, PID control of the position is possible. However, the positioning of the pneumatic stage is slower than that of the electromagnetic actuators such as a linear and a ball screw stages. Generally, when either the controlled object or the compensator has a slow response, the response of the control system becomes slow. In the previous studies, the pneumatic stage itself, which is the controlled object, was focused on. Local feedback applied to the pneumatic and mechanical systems realized high-speed positioning. However, the influence on the positioning response using PDD 2 compensator, which forms the framework of the position control, has not been considered. Therefore, this note focuses on the structure of PDD 2 compensator. Here, the characteristics of this compensator are reinterpreted. Specifically, it is shown that a slow response cannot be avoided intrinsically due to the structure of this compensator. Furthermore, modified PDD 2 compensator with improved slow response is proposed.

Perfect Tracking Control of Linear Sliders Using Sliding Mode Control with Uncertainty Estimation Mechanism

“…For the switching surface s shown in Equation ( 29), the Lyapunov function V is defined as shown in Equation (30).…”

“…Additionally, control methods using model estimation by AI have been proposed [27][28][29]. Research on stage positioning using air pressure has also been conducted [30][31][32]. In both methods, even if uncertainty compensation is performed, it is difficult to adapt to changes in uncertainties because the uncertainty model is identified offline or learning is performed at long intervals.…”