Pneumatic actuator with embedded MR-brake for haptics

A pneumatic cylinder with an embedded magnetorheological (MR) brake has been developed. The new hybrid actuator benefits from the advantages of MR-brakes and pneumatic cylinders. It can apply forces using compressed air and can resist external forces using the MR-brake. The embedded brake enables dealing with challenges of using compressed air in precise positioning of the piston anywhere in its stroke with simple solenoid valves. The actuator may be beneficial in haptics as it can create rigid collision effects with its MR-brake and can also apply forces unlike some of the existing haptic interfaces with only MR-brakes. The paper presents mathematical model and experimental results. The simulated responses have good agreement with the measured responses from the actual system. Identification of some of the system parameters in the model proved to be challenging but was accomplished using multivariate optimization.