Velocity Acquisition Methods for Stable Haptic Simulation Systems
Haptic simulation systems enable the perception of virtual environments through the sense of touch. These systems are composed of a haptic device through which an operator interacts with the virtual environment that is graphically and dynamically rendered in a computer. The stability of haptic simulation systems is compromised by the data acquisition sample and hold process that connects continuous and virtual worlds. Typically in these systems, the haptic device position is sampled and the velocity is estimated in discrete-time from the position samples in order to simulate the real environment dynamics and generate the environment force feedback. Velocity estimation in discrete-time domain limits the range of virtual environment dynamics that can be implemented in stable way. In order to increase the range, two velocity acquisition methods are investigated. First, sampling velocity directly from an analog gyro. Second, sampling analog velocity approximation obtained from passing analog position through a high-pass lter. Uncoupled stability and passivity criteria, considered as the most stringent stability conditions, are employed to analytically and experimentally evaluate the system stability and robustness of the proposed methods. Results indicate that the direct velocity measurement improves the stability, while the analog velocity approximation method offers a wide range of virtual environments that can be stably simulated.