Estimation and volitional feedback control of active work rate during robot-assisted gait

Body weight supported robotic-assisted devices are normally used in gait rehabilitation of neurologically impaired persons but also have potential for application in cardiopulmonary rehabilitation. In this paper, a method of estimating and controlling the rate of active work done during supported stepping is proposed and experimentally validated through ambulation of three subjects with a spinal cord injury. The estimation and feedback scheme enabled work rates to be produced in close agreement to reference values. The efficacy of the proposed control scheme will facilitate the use of the technology in cardiopulmonary training and testing protocols. © 2008 Elsevier Ltd. All rights reserved

Feedback control of oxygen uptake during robot-assisted gait

Body-weight-supported robot-assisted devices can be used to promote gait rehabilitation and as exercise tools for neurologically impaired persons such as stroke and spinal-cord-injured patients. Here, we propose a novel feedback-control structure for real-time control of oxygen uptake during robot-assisted gait, in which we use the following methods. 1) A feedback-control structure is proposed, consisting of a dynamic controller operating on target and actual levels of oxygen uptake in order to set a target work rate. Target work rate is achieved by an inner volitional feedback loop which relies on the subject's exercise input. 2) The dynamic oxygen-uptake controller is based on an empirically derived model of the oxygen-uptake dynamics and is synthesized by pole placement. 3) The resulting control system is tested during the robot-assisted treadmill ambulation of five able-bodied subjects. A single linear controller was designed based on identification data from tests with one subject and used for closed-loop control tests with all five subjects. In all cases, the actual oxygen-uptake response closely followed the ideal response as specified by the feedback design parameters. The control of oxygen uptake during body-weight-supported robot-assisted ambulation is feasible in the able-bodied population; the robustness of the system is demonstrated within the class of subjects tested. Further testing is required to validate the approach with neurologically impaired subjects. © 2009 IEEE

Estimation and volitional feedback control of active work rate during robot-assisted gait

Body weight supported robotic-assisted devices are normally used in gait rehabilitation of neurologically impaired persons but also have potential for application in cardiopulmonary rehabilitation. In this paper, a method of estimating and controlling the rate of active work done during supported stepping is proposed and experimentally validated through ambulation of three subjects with a spinal cord injury. The estimation and feedback scheme enabled work rates to be produced in close agreement to reference values. The efficacy of the proposed control scheme will facilitate the use of the technology in cardiopulmonary training and testing protocols. © 2008 Elsevier Ltd. All rights reserved

Control of work rate-driven exercise facilitates cardiopulmonary training and assessment during robot-assisted gait in incomplete spinal cord injury

Treadmill training is used for gait rehabilitation in various neurological conditions. Robot-assisted treadmill training automates repetition of the gait cycle and can reduce the load on therapists. Here we investigate the use of robot-assisted treadmill technology in cardiopulmonary rehabilitation and assessment. Using a new approach to exercise work rate estimation and volitional control, we propose cardiopulmonary assessment protocols for robot-assisted gait exercise, designed for estimation of cardiopulmonary performance parameters. Feasibility was explored in three subjects with incomplete spinal cord injury using the Lokomat system. Estimation and visual feedback of exercise work rate allowed all subjects to accurately follow specified work rate profiles in real time by means of volitional control. We were able to estimate the main cardiopulmonary performance parameters from constant work rate and incremental tests. "Passive" walking elicited a substantial metabolic response: on average, oxygen uptake (over(V, ̇)O2) was a factor of 1.8 higher than during rest. The magnitude of peak over(V, ̇)O2 above rest, obtained from incremental tests, was a factor of 4-6 higher than the increment in over(V, ̇)O2 for passive walking, thus emphasising the importance of the subjects' active participation in the exercise. Visual feedback and volitional control of estimated exercise work rate facilitates the imposition of work rate profiles for estimation of cardiopulmonary performance parameters in robot-assisted gait. This new approach could be used to guide a patient's training regime during a cardiopulmonary rehabilitation programme, and for periodic assessment of cardiopulmonary status. © 2007 Elsevier Ltd. All rights reserved