Keiichiro Miyata

PI type hierarchical feedback control scheme for pneumatic robots

A control scheme for pneumatic drive systems is proposed. In general, static friction, Coulomb friction, and other nonlinear disturbances crucially worsen the performance of pneumatic drive systems. In the proposed control scheme, to guarantee robustness against such disturbances and stability of the motion, position feedback loops and pressure feedback loops are hierarchically connected. The stability of the motion is investigated by using a Lyapunov function. As a result, it is mathematically proven that the motion of pneumatic drive systems converges to a fixed desired point as time tends to infinity, even if the disturbances affect the motion. The effectiveness of this control scheme is demonstrated through some experimental results.<<ETX>>

Studies on a constant speed drive of a pneumatic cylinder.

In many industrial applications, open-loop control which uses on-off valves and restrictors are widely used for constant speed drive of pneumatic cylinders.This paper describes the conditions and characteristics of constant speed drive of pneumatic cylinders. First, we derived the conditions for the constant speed drive based on the equation of motion and equations of pressure change in cylinder chambers. It was shown that pressure in both chambers must be constant for constant speed drive. In case where air is exhausted with a choke velocity, the outlet restriction determines piston speed uniquely as well as the conventional meter-out circuit. Steadystate pressure of the forcing side is determined by the inlet restriction and this affects the velocity response when motion starts. In the conventional meter-out circuit, the inlet restriction is given only by the inlet valve and large overshoot occurs at the start of motion. To get a fast response with a small overshoot, the inlet restriction should be adjusted properly.The size of optimum inlet restrictions was calculated for various reference speeds and loads by using basic equations and a method to estimate the size of inlet restriction by using friction forces was discussed.Experiments were carried out and the effectiveness of inlet restriction for desirable motion was confirmed.