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Session: Motor Control I
Session starts: Friday 25 January, 10:30
Presentation starts: 11:30
Room: Lecture room 558

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Bram Onneweer (TU Delft)
Winfred Mugge (TU Delft)
Alfred Schouten (TU Delft / Universiteit Twente)

Abstract:
In haptic tele-manipulation systems, the human operator manipulates objects and uses tools in remote environments using a master-slave system. The human controls the slave (e.g. a remote robot arm), via the master (e.g. a joystick) while haptic information of the forces at the slave is fed back to the human operator. For optimal system design, it is important to understand the accuracy and limitations of human force perception. Previous research demonstrated that humans generate higher forces when asked to reproduce an externally applied target force [1,2]. It has been proposed that the nervous system attenuates feedback from self-generated forces, i.e. humans perceive self-generated forces lower than externally applied forces [1]. Walsh et al. 2011 found that the force difference diminished when matching higher externally applied force levels or when the target was self-generated with the other hand [2]. The goal of our study was to determine how accurately subjects reproduce self-generated forces with the same hand over a broad range of force levels. Subjects (n=10) were instructed to generate an onscreen target force with visual support and subsequently reproduce the same force without visual support with their right hand against a static handle equipped with a force sensor. In the experiment, six force levels (10, 40, 70, 100, 130, 160N) were presented in random order; each with eight repetitions. Subjects generated too high forces for lower force levels (<70N) and too low forces for higher force levels (>100N). The results for low force levels are in accordance to previous findings using externally applied target forces [1,2], but contradicts with the findings using self-generated target forces [2]. Our results indicate that attenuated feedback of self-generated forces is not the key factor in force reproduction. Instead we suggest that the integration of tactile and proprioceptive feedback plays an important role in force estimation and varies with force level.