TY - JOUR T1 - Evaluation of Velocity Estimation Methods Based on their Effect on Haptic Device Performance JF - IEEE/ASME Transactions on Mechatronics Y1 - 2018 A1 - V. Chawda A1 - O. Celik A1 - M. K. O'Malley KW - Estimation KW - Frequency division multiplexing KW - Haptic interfaces KW - Impedance KW - Kalman filters KW - Performance evaluation KW - Rendering (computer graphics) AB -

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.

VL - 23 ER - TY - Generic T1 - A Cable-based Series Elastic Actuator with Conduit Sensor for Wearable Exoskeletons T2 - International Conference on Robotics and Automation (ICRA) Y1 - 2017 A1 - L. H. Blumenschein A1 - C. G. McDonald A1 - M. K. O'Malley KW - actuation system design KW - Actuators KW - cable tension control KW - cable tension measurement KW - cable-based series elastic actuator KW - cable-conduit transmission KW - cables (mechanical) KW - compliance control KW - compliant force sensor KW - conduit sensor KW - DC motor KW - DC motors KW - deflection measurement KW - dynamic effect KW - Exoskeletons KW - Feedback KW - flexible cable conduit transmission KW - Force KW - Force control KW - force sensors KW - full wearable exosuit KW - gearbox KW - Hall effect sensors KW - Hall effect transducers KW - human arm KW - human-robot interaction KW - Impedance KW - Magnetic flux KW - physical assistance KW - robot dynamics KW - Robots KW - series elastic force sensor KW - soft exosuit KW - soft wearable exoskeleton KW - springs (mechanical) KW - translational steel compression spring KW - transmission conduit KW - user interface KW - virtual impedance KW - wearable robotic device JF - International Conference on Robotics and Automation (ICRA) PB - IEEE CY - Singapore ER -