Haptic joystick with hybrid actuator using air muscles and spherical MR-brake

Abstract

In this research, a new 2-DOF hybrid actuator concept is explored as a powerful and compact alternative to conventional haptic actuators. The actuator combines a spherical MR-brake and three air muscles and is integrated into a joystick that can apply forces in two degrees-of-freedom. The air muscles are used to create high active forces in a compact volume and the brake compensates for the “spongy” feeling associated with air muscles. To decrease the overall size of the system an inertial measurement unit has been implemented as a position measurement solution. As high as 16 N of total force output could be achieved at the tip of the joystick. Also, up to 16 times improvement in the stable virtual wall stiffness was obtained when the MR-brake was used to compensate for force errors. Experiments with an impedance-based haptic controller with force-feedback gave satisfactory wall following performance. This device can be employed in applications including computer games, military or medical training applications, rehabilitation and in teleoperation of equipment where high force feedback in 2-DOF in a compact work volume may be desirable while interacting with rigid or elastic virtual objects.