| For robotic systems that use pneumatic actuators with on/off solenoid valves, sliding-mode control laws for precise position control and low switching (open/close) activity of the valves are presented. A pneumatic actuator has two chambers with a total of four on/off solenoid valves. Thus, there are sixteen possible combinations for the valves' on/off positions. Only seven of these sixteen operating modes" are considered both functional and unique. While previous work has focused on three-mode closed-loop control of such an actuator, this thesis extends the three-mode control to seven-mode control. This thesis also extends the application from the position control of a single robot to the bilateral control of a telerobot.;We introduce and compare two novel seven-mode controllers for a pneumatic actuator. The first is a sliding-mode controller utilizing a switching function that is a function of the system states. The second is a sliding-mode, pulse-width-modulation (PWM) controller utilizing a time-averaged model of the open-loop system. Both controllers minimize the tracking error by employing the operating modes that have the necessary and sufficient amounts of drive energy and, thus, involve reduced switching activity while maintaining satisfactory tracking performance. The performance of the proposed control design is experimentally verified on a single pneumatic actuator.;Also, the seven-mode position control is extended to force control to make seven-mode teleoperation control possible. Experimental verification on a pair of pneumatic actuators utilizing position-position based and force-position based teleoperation control to verify the validity of our theoretical results. Overall, it is found that leveraging the additional modes of operation leads to more efficient and smoother control in both the single-actuator and the dual-actuator teleoperated pneumatic systems. |
