Closed-Loop Cadence and Instantaneous Power Control on a Motorized Functional Electrical Stimulation Cycle

FES Cycling and Closed-Loop Feedback Control for Rehabilitative Human–Robot Interaction

“…In the following, an overview of the authors' previous results on FES cycling is presented [15][16][17][18][19][20]. Sections are divided by tracking objectives:(1) cadence control, where the cycle and rider have a shared tracking objective [15,16]; (2) direct torque control, where the cycle and rider have separate tracking objectives [17,18]; and (3) indirect torque control, where the cycle and rider have coupled tracking objectives [19,20]. Within each section (i.e., for each tracking objective), the results are further divided into robust [15,17,19] and adaptive control [16,18,20].…”

“…Sections are divided by tracking objectives:(1) cadence control, where the cycle and rider have a shared tracking objective [15,16]; (2) direct torque control, where the cycle and rider have separate tracking objectives [17,18]; and (3) indirect torque control, where the cycle and rider have coupled tracking objectives [19,20]. Within each section (i.e., for each tracking objective), the results are further divided into robust [15,17,19] and adaptive control [16,18,20]. For each result, sample experimental results are provided to highlight various measures and metrics including average tracking errors and standard deviations.…”

“…For a shared control objective, the rider's muscles and the cycle's motor jointly contribute to the same objective (e.g., attaining a desired cadence on the FES cycle) [15,16]. Similarly, when dealing with separate objectives, the cycle's motor can be tasked with keeping the cycle at a desired cadence, while the rider's muscles maintain the desired interaction torque [17,18]. Finally, the rider's muscles and the cycle's motor can also have coupled tracking objectives, as in the case of indirect torque control or admittance control [19,20].…”

“…For the aforementioned objectives, the authors implemented two closed-loop control approaches on FES-cycles: robust [15,17,19] and adaptive [16,18,20] control. A fundamental use of feedback for automatic control is to provide robustness to uncertainty or undesired effects such as disturbances.…”

“…Specifically, this paper addresses the scenarios in which the human and motorized cycle have shared, separate and coupled tracking objectives that yield significant challenges in the control design and stability analysis of the human-robot system. To address the challenges, the authors' previous work on FES cycling is discussed [15][16][17][18][19][20] for each combination of controller (robust and adaptive) and tracking objective (cadence, direct torque and indirect torque tracking). By comparing and contrasting the results, many considerations involved in intimate human-robot interaction are discussed.…”