For robotic systems that use on/off (solenoid) pneumatic actuators, a sliding mode control law for precise position control and low switching (open-close) activity of the valves is presented in this paper. Given a pneumatic actuator with two chambers and four solenoid valves, there are sixteen possible input combinations defined directly from the state of the four on/off valves present in the system; however, only seven of these discrete operating modes are considered both functional and unique. Therefore, we introduce a novel seven-mode sliding controller that minimizes the position tracking error using modes that have both the necessary and sufficient amounts of drive energy and, thus, involve reduced switching activity. An analysis of the closed-loop system stability is carried out. The performance of the proposed control design is experimentally verified on a single pneumatic actuator setup comprising of two chambers with four on/off valves.

Abstract-A pneumatic actuator with solenoid valves is a discontinuous-input system because each valve can be either in on or off state. For such an actuator, this paper proposes a slidingmode control scheme that is based on an averaged continuousinput model of the discontinuous-input open-loop system. The averaged model is obtained from the nonlinear dynamics of the open-loop system undergoing pulse-width-modulation (PWM) at the input (i.e., valve open/close action). The PWM duty cycle will be regarded as a continuous input to the proposed averaged model, and thus generated by the proposed slidingmode controller.For the sliding control design, we note that a pneumatic actuator has two chambers with a total of four on/off valves. Thus, there are sixteen possible combinations for valves' switching. Seven of these sixteen operating "modes" are considered both functional and unique. The proposed sliding control utilizes and switches between these seven modes of the open-loop system in order to select the ones with necessary and sufficient amounts of drive energy. In comparing the new 7-mode controller to previous controllers, we will demonstrate reductions in the position tracking error and the number of switches made by the actuator's on/off valves. The proposed control scheme is used in both position control of a pneumatic cylinder and bilateral control of a one degree of freedom teleoperation system. Experimental results are presented to validate our theoretical findings.

Abstract-This paper proposes a sliding mode law for precise position control with minimal switching activity for a robotic system that uses on/off (solenoid) pneumatic actuators, For a two-chamber pneumatic actuator with four binary solenoid valves, there is a total of sixteen possible input combinations defined directly from the state of the four on/off solenoid valves present in the system. However, only seven of these discrete operating modes are considered both functional and unique. Accordingly, we use a seven-mode sliding controller that minimizes the position error using modes that have both the necessary and sufficient amounts of drive energy and, thus, involve reduced switching activity. An analysis of the closedloop system stability is carried out. The performance of the proposed control design is experimentally verified on a single pneumatic actuator comprising of two chambers driven by four on/off solenoid valves.

This paper proposes a sliding mode law for precise position control with minimal switching activity for a robotic system that uses on/off (solenoid) pneumatic actuators, For a two-chamber pneumatic actuator with four binary solenoid valves, there is a total of sixteen possible input combinations defined directly from the state of the four on/off solenoid valves present in the system. However, only seven of these discrete operating modes are considered both functional and unique. Accordingly, we use a seven-mode sliding controller that minimizes the position error using modes that have both the necessary and sufficient amounts of drive energy and, thus, involve reduced switching activity. An analysis of the closedloop system stability is carried out. The performance of the proposed control design is experimentally verified on a single pneumatic actuator comprising of two chambers driven by four on/off solenoid valves.

Abstract-A pneumatic actuator with solenoid valves is a discontinuous-input system because each valve can be either in on or off state. For such an actuator, this paper proposes a sliding-mode control scheme based on an averaged continuousinput equivalent model for the open-loop system. The averaged model is obtained from the nonlinear dynamics of the open-loop discontinuous-input system undergoing pulse-width-modulation (PWM) at the input (i.e., valve open/close action). The PWM duty cycle will be regarded as a continuous input to the proposed averaged model, and thus generated by the proposed sliding-mode controller. By adjusting the PWM duty cycle, the controller switches between seven modes of operation of the open-loop system in order to select the ones with necessary and sufficient amounts of drive energy to achieve position tracking. We will show that this results in reduced position error and valve switching activity for the actuator. The proposed control scheme is experimentally used in the position control of a pneumatic actuator and the results are presented.

For a pneumatic teleoperation system with on/off solenoid valves, sliding mode control laws for position and force ensuring low switching (open/close) activity of the valves are developed. Since each pneumatic actuator has two pneumatic chambers with a total of four on/off valves, 16 possible combinations ('operating modes') for the valves' on/off positions exist, but only seven of which are both functional and unique. While previous work has focused on three-mode slidingbased position control of one pneumatic actuator, this paper develops the seven-mode sliding-based bilateral control of a teleoperation system comprising a pair of pneumatic actuators. The proposed bilateral sliding control schemes are experimentally validated on a pair of actuators utilizing position-position and force-position teleoperation architectures. The results demonstrate that leveraging the additional modes of operation leads to more efficient and smoother control of the pneumatic teleoperation system. It was found that viscous friction forces were crippling haptic feedback in the position-position architecture. Through the use of force sensors, the force-position architecture was able to compensate for the heavy viscous friction forces.

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For a pneumatic teleoperation system, slidingmode control laws ensuring both transparency and low switching (open/close) activity of the valves are developed. Each pneumatic actuator has four on/off valves, thus sixteen possible combinations ("operating modes") for the valves exist but only seven of them are both functional and unique. While previous works have focused on three-mode sliding-based position control of one pneumatic actuator, this paper develops seven-mode sliding-based bilateral control of a teleoperation system comprising a pair of pneumatic actuators. The proposed bilateral sliding control scheme is experimentally validated on a pair of actuators arranged in a force-position teleoperation architecture. The results demonstrate that leveraging the additional modes of operation leads to more efficient and smooth control of the system.