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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