A New Approach for Simplifying Multi-Degree of Freedom Haptic Device Dynamics Model

A haptic device (HD) is an interface used for simulating a virtual environment (VE) for its operator. While simulating a VE, the HD should be stable; otherwise, it can damage itself or its operator. Usually, HDs are multi-degree-of-freedom serial manipulators with sensor quantization and friction in their joints. Hence, the HD dynamics is complex and its analytical stability analysis is complicated. During simulating of the VE for the operator, stylus movements are small. In the previous studies, the multi-DOF nonlinear dynamics of the HD was replaced with simple dynamics in which mass and viscous values are constant. However, there were neither analytical methods to determine the values of the mentioned parameters in the simplified model nor studying the accuracy of this simplification is studied. In this paper, a novel and general approach is employed for simplifying a multi-degree-of-freedom haptic device dynamics during arbitrary motion around the operating point, and its accuracy in the prediction of the stable simulation of the VE is discussed. Meanwhile, sensor quantization and Coulomb friction are considered in the model. This method is evaluated through simulation for stability analysis of the PHANToM 1.5 and KUKA Light Weight Robot IV (LWR IV) as haptic interfaces in various situations.