Compensation for the intrinsic dynamics of the InMotion2 robot.
Citation: Journal of Neuroscience Methods. 214(1):15-20, 2013 Mar 30.PMID: 23313756Institution: MedStar National Rehabilitation NetworkForm of publication: Journal ArticleMedline article type(s): Journal Article | Randomized Controlled Trial | Research Support, U.S. Gov't, Non-P.H.S.Subject headings: *Robotics | Adult | Algorithms | Anisotropy | Arm/ir [Innervation] | Arm/ph [Physiology] | Biomechanics | Electric Impedance | Female | Humans | Male | Movement Disorders/rh [Rehabilitation] | Psychomotor Performance | Robotics/is [Instrumentation] | Torque | Young AdultISSN:- 0165-0270
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Journal Article | MedStar Authors Catalog | Article | Available | 23313756 |
The InMotion2 and other similarly designed robots, are commonly used for rehabilitation of neurological injuries and motor adaptation studies. These robots are used to simulate haptic environments; however, anisotropy in end-point impedance due to the intrinsic robot dynamics can compromise these experiments. The goal was to decrease the magnitude and anisotropy of the robot impedance using a dynamic compensation algorithm that reduces the forces normally felt by the user during rapid movements. We tested this algorithm with two different methods for real-time calculation of derivatives, a novel quadratic fit method (CQF) and the commonly used backward derivative method (CBD). Six subjects performed a series of point-to-point movements under three conditions (no compensation, CQF, CBD), in different directions at peak speeds of 50, 100 and 150 cm/s. Without compensation, tangential peak-to-peak forces were as large as 69 N in certain directions at the 150 cm/s speed. Both CQF and CBD significantly reduced tangential forces in all directions and speeds. CQF outperformed CBD in the directions with highest intrinsic impedance, reducing tangential forces by 64% in these directions. Compensation also significantly reduced forces normal to the movement direction, with CQF again outperforming CBD in several cases. Anisotropy was assessed by the range of tangential peak-to-peak forces across movement directions. In the no compensation condition, anisotropy was as high as 52.7 N at the 150 cm/s speed, but an average anisotropy reduction of 74% was achieved with CQF. The CQF method can significantly reduce impedance and anisotropy in this class of robot. Copyright 2013 Elsevier B.V. All rights reserved.
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