Abstract
Teleoperated robotic systems are widely spreading in multiple different fields, from hazardous environments exploration to surgery. In teleoperation, users directly manipulate a master device to achieve task execution at the slave robot side; this interaction is fundamental to guarantee both system stability and task execution performance. In this work, we propose a non-disruptive method to study the arm endpoint stiffness. We evaluate how users exploit the kinetic redundancy of the arm to achieve stability and precision during the execution of different tasks with different master devices. Four users were asked to perform two planar trajectories following virtual tasks using both a serial and a parallel link master device. Users' arm kinematics and muscular activation were acquired and combined with a user-specific musculoskeletal model to estimate the joint stiffness. Using the arm kinematic Jacobian, the arm end-point stiffness was derived. The proposed non-disruptive method is capable of estimating the arm endpoint stiffness during the execution of virtual teleoperated tasks. The obtained results are in accordance with the existing literature in human motor control and show, throughout the tested trajectory, a modulation of the arm endpoint stiffness that is affected by task characteristics and hand speed and acceleration.
Highlights
Teleoperated robotic systems are widely used in several long-short range application fields, from plant decommissioning (Cragg and Hu, 2003), environment exploration (Mitsou et al, 2006), hazardous material handling and surgery (Johnson and Somu, 2016)
We present a non-disruptive method for the computation of the arm endpoint stiffness based on a user specific 7 degrees of freedom (DoF) musculoskeletal model of the upper limb (Delp et al, 2007)
While the stiffness variance increases in the Shape Fitted Half Cloverleaf (SFHC) task when teleoperating with parallel links haptic interface (PL), when teleoperating with the serial links haptic interface (SL) master device, instead, users decreased the arm stiffness variance when performing SFHC with respect to Half Cloverleaf (HC)
Summary
Teleoperated robotic systems are widely used in several long-short range application fields, from plant decommissioning (Cragg and Hu, 2003), environment exploration (Mitsou et al, 2006), hazardous material handling and surgery (Johnson and Somu, 2016). In order to control the remotely operated system, the user interacts with a master interface, a robot whose precise and accurate manipulation allows task execution at the slave side. The design of master interfaces is a fundamental aspect in teleoperation, several studies focused on the master devices physical and control characteristics to achieve control transparency while assuring system stability (Fischer et al, 1990; Conti et al, 2014; Enayati et al, 2016). Stability of humanrobot interaction (Colgate, 1994) is guaranteed by closing the control loop with the user sensory and motor systems and, in this context, both the robot and the user are considered as passive elements (Lee and Spong, 2006).
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