Magnetorheological fluids are composite materials made of ferromagnetic particles, medium oils, and several types of additives. We have developed actuation systems for the fine haptic control of master–slave robots. In this study, we proposed a new structure of a magnetorheological fluid–based actuator suitable for haptic devices. For the basic structure of the actuator, we proposed a twin-driven magnetorheological fluid actuator using two multi-layered disc-type magnetorheological fluid clutches for haptics. We conducted performance measures for the magnetorheological fluid clutches for haptics with three commercially available magnetorheological fluids (i.e. 122EG, 132DG, and 140CG from Lord Corp.). The experimental results show that 132DG is a better material for force control. Then, we proposed two types of twin-driven magnetorheological fluid actuators (i.e. link type and belt type) and compared their performance. The results show that the averages of the time constant are 19.1 and 16.1 ms for the link type and belt type, respectively. Furthermore, the averages of torque error are 0.033 and 0.068 N m for the link type and belt type, respectively. However, the belt-type twin-driven magnetorheological fluid actuator is better if a large range of motion is required, while the link-type twin-driven magnetorheological fluid actuator is better if accurate torque control is required.
Magnetorheological fluids (MRFs) are composite materials made of ferromagnetic particles, medium oils, and several types of additives. We have developed an actuation system for the fine haptic control of leader-follower robots. In this study, we developed a haptic interface with two link-type twin-driven MR fluid actuators and two MR fluid brakes for a teleoperation endoscopic surgery system and conducted evaluation tests for a remote operational task with a leader-follower robot system. For evaluations, we adopted the NASA-TLX questionnaire as a subjective assessment method. According to the experimental results, the total success rates were 0.462, 0.333, and 0.591, for the first haptic, middle no-haptic, and second haptic phases, respectively. The force information of the haptic forceps helped users to perceive grasping sensation on their fingers. Statistical analyses on the answers to the questionnaire indicate no significant differences. However, a decreasing tendency in the mental stress in the complicated manipulation tasks for fragile objects is observed.
A magnetorheological (MR) fluid is a composite material comprising ferromagnetic particles, medium oils, and several types of additives. We developed an MR fluid clutch for haptics (H-MRC) and installed it in a haptic interface that simulates teleoperation endoscopic surgery (ES). To enhance its operability, we redesigned the H-MRC to reduce its weight and improve its control system. We reduced the weight of the H-MRC and haptic gripper by 77.0 g and 137.0 g, respectively. To evaluate the influence of the improvement and force feedback functions on remote operation skills, we conducted pick-and-place tests with a remotely controlled system. In the tests, we subjectively evaluated the NASA-TLX and quantitatively evaluated the success rate of the task. The results of the subjective assessment showed significant reductions in mental stress during the teleoperation task. In addition, the results of the quantitative evaluation showed that the force feedback function was effective against the teleoperation skills of the operators.
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