|Evaluation of Velocity Estimation Methods Based on their Effect on Haptic Device Performance
|Year of Publication
|Chawda, V, Celik, O, O'Malley, MK
|IEEE/ASME Transactions on Mechatronics
|Estimation; Frequency division multiplexing; Haptic interfaces; Impedance; Kalman filters; Performance evaluation; Rendering (computer graphics)
This paper comparatively evaluates the effect of real-time velocity estimation methods on passivity and fidelity of virtual walls implemented using haptic interfaces. Impedance width, or Z-width is a fundamental measure of performance in haptic devices. Limited accuracy of velocity estimates from position encoder data is an impediment in improving the Z- width in haptic interfaces. We study the efficacy of Levant's differentiator as a velocity estimator, to allow passive implementation of higher stiffness virtual walls as compared to some of the commonly used velocity estimators in the field of haptics. We first experimentally demonstrate feasibility of Levant's differentiator as a velocity estimator for haptics applications by comparing Z-width performance achieved with Levant's differentiator and commonly used Finite Difference Method (FDM) cascaded with a lowpass filter. A novel Z-width plotting technique combining passivity and fidelity of haptic rendering is proposed, and used to compare the haptic device performance obtained with Levant's differentiator, FDM+lowpass filter, First Order Adaptive Windowing and Kalman filter based velocity estimation methods. Simulations and experiments conducted on a custom single degree of freedom haptic device demonstrate that the stiffest virtual walls are rendered with velocity estimated using Levant's differentiator, and highest wall rendering fidelity is achieved by First Order Adaptive Windowing based velocity estimation scheme.