Development of 2-DOF haptic devices working with magnetorheological fluids

The thesis presents the design and development of a 2-DOF (degree of freedom) magnetorheological (MR) fluid based haptic joystick and studies its applications in virtual reality. MR fluids are controllable fluids that can generate adaptable resistance forces when subjected to a magnetic field. This feature is capable of realizing novel haptic devices. The developed system consists of three main parts: MR joystick, control and display hardware, and software. The MR joystick is constructed of two disc-shaped MR actuators positioned perpendicularly with a gimbal structure, which transfers the movement of the joystick handle into two actuator rotary movements. Therefore, operators can feel the resisting force generated by the two actuators. The dimensions of the actuators have been optimized using finite element analysis, and the steady-state performance of the actuators has been measured and analyzed. The kinetics of the joystick in terms of working space and resistance will be discussed. In the thesis, a subhysteresis model and a torque converting method will be employed to enhance the accuracy of the force control. The applications of the MR joystick in virtual reality will be demonstrated by using six typical interface examples designed in LabVIEW. These demonstrations show that the MR haptic devices have a huge application potential in entertainment, medical, and general industry fields.