TY  - BOOK
AU  - Lum, Peter S
AU  - Nguyen, Hoi B
TI  - Compensation for the intrinsic dynamics of the InMotion2 robot
SN  - 0165-0270
KW  - *Robotics
KW  - Adult
KW  - Algorithms
KW  - Anisotropy
KW  - Arm/ir [Innervation]
KW  - Arm/ph [Physiology]
KW  - Biomechanics
KW  - Electric Impedance
KW  - Female
KW  - Humans
KW  - Male
KW  - Movement Disorders/rh [Rehabilitation]
KW  - Psychomotor Performance
KW  - Robotics/is [Instrumentation]
KW  - Torque
KW  - Young Adult
KW  - MedStar National Rehabilitation Network
KW  - Journal Article
KW  - Randomized Controlled Trial
KW  - Research Support, U.S. Gov't, Non-P.H.S
N2  - 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
UR  - http://dx.doi.org/10.1016/j.jneumeth.2013.01.001
ER  -