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.
Pennycott, A., Hunt, K. J., Coupaud, S., Allan, D. B., & Kakebeeke, T. H. (2010). Feedback control of oxygen uptake during robot-assisted gait. IEEE Transactions on Control Systems Technology, 18(1), 136-142. https://doi.org/10.1109/TCST.2008.200946