FA compensation variable Bang-Bang controller for pneumatic position servo

At first, this paper presents a pulse width modulation (PWM) control method for the rodless cylinder based on two-bit two-channel high speed on-off valves, which features in the ability of cutting-off the chambers of the cylinder. To overcome the phenomena of overshooting and oscillation exiting in the common Bang-Bang controller, a force and acceleration (FA) compensation variable Bang-Bang controller for PWM based pneumatic position servo is presented. Based on a trigger evaluation function whose parameters are the position error and the velocity error, the controller is able to compensate the friction force brought out by the movement of the piston by adding the friction force in the chamber force evaluation equation. To adjust the controlling parameters dynamically, some kinds of increasing functions, such as step function, linear function and invert tangent function, are used to setting the piston's desired acceleration with the reduction of the position error. A pneumatic glass-wall cleaning robot 'Sky-cleaner IV' is used to implement a series of on loading position servo experiments to testify the feasibility of the controllers with the above three desired acceleration setting functions respectively. The different results of them are compared to find that the FA compensation variable Bang-Bang Controller is available in promoting the position servo precision.