Design and hybrid control of the pneumatic force-feedback systems for Arm-Exoskeleton by using on/off valve

Volume Flow Characterization of PWM-Controlled Fast-Switching Pneumatic Valves

“…The PWM signal frequencies f PWM [Hz] 50 Hz [7], 100 Hz [8], up to 50 Hz [9], 100 Hz [10], 50 Hz [11] and 20 to 60 Hz [12]. Efforts were made to develop electro-pneumatic valve models based on the electrical and pneumatic parts modelling and to use these models in a PWM-driven pneumatic system [8], [9] and [13]. The relationship between the pulse width and the fluid flow was always defined to be linear, and the minimum PWM pulse was used in only one paper, [7] and [14].…”

Control of pneumatic artificial muscle system through experimental modelling

“…Furthermore, negligible valve dead zone time was recorded. In comparison, van den Brink [10] obtained a steady state time of 0.3 s for a step of 0.5 bar using low cost on-off valves and a loop-shaped linear controller whereas Ying et al [20] obtained a steady state time of $0.1 s with a on-off valves and a fuzzy controller. Similarly, using conventional PI control with proportional valves, Wakimoto et al [19] achieved a steady state time of 0.5 s for a 2 bar step with nearly 20% overshoot.…”

Nonlinear Discontinuous Dynamics Averaging and PWM-Based Sliding Control of Solenoid-Valve Pneumatic Actuators

“…However, they suffer from drawbacks including friction and variation of the actuator dynamics to load and piston position along the cylinder stroke [12] and accurate position control of such actuators is difficult due to the nonlinear dynamics [13]. Despite these difficulties, this kind of systems could be found in medical robotics applications for needle insertion, MRI compliant telerobots (where electric actuators are banned) [14], and exoskeletons [15] for rehabilitation purpose.…”

“…Shen et al also created a haptic interface which implemented a pneumatically actuated impedence to simulate stiffness [19]. Ying et al developed an arm-exoskeleton with pneumatically driven force-feedback systems employing on/off valves and fuzzy logic controllers [15]. All of these works demonstrated how effective model-based control can be for implementing a pneumatically actuated system.…”