Torque control of Virtual Bike with magnetorheological fluid brake and sensory evaluation for difference threshold of pedal resistance

In this study, we developed a virtual cycling system (VR Bike) using a magnetorheological fluid brake (MRB). This system consists of a bike, the MRB, a 3-D projector, a screen, a controller and a sound device. Users can drive the bike in virtual worlds with vision, sound, and reaction force on its pedal. We have developed a cylindrical MRB in the previous study, and it was utilized as the torque generator for the pedaling resistance of the VR Bike. This system is useful for aerobic exercise device. In this paper, we discussed torque control methods of the MRB. A braking torque generated with a constant current input normally changes depending on the rotational speed of the MRB. However, torque compensation based on the velocity feedback reduced the error between reference torques and output torques. We also conducted sensory evaluation tests for young healthy male subjects. In their experiments, difference thresholds of the pedaling forces are about 1 ~ 2 Nm for all standard stimulus.