Zeroing Control Barrier Functions for Safe Volitional Pedaling in a Motorized Cycle⁎This research is supported in part by AFOSR award number FA9550-19-1-0169 and NSF Award number 1762829. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reect the views of the sponsoring agency. Issue 5 (2020)

• Record Type: Journal Article
• Authors: Isaly, Axton; Allen, Brendon C.; Sanfelice, Ricardo G.; Dixon, Warren E.
• Is Part Of: IFAC-PapersOnLine. Volume 53:Issue 5(2020)
• Page Start: 218
• Page End: 223
• Publication Date: 2020
• Subjects: Rehabilitative Cycling -- Barrier Function -- Safety-critical -- Euler-Lagrange; Automatic control -- Periodicals; 629.805
• DOI: 10.1016/j.ifacol.2021.04.100
• Languages: English
• ISSNs: 2405-8963

Abstract

Abstract: A minimally restrictive robust controller is developed for a motorized rehabilitative cycling system. The controller yields a forced-use movement therapy that constrains the rider's cadence to remain within a user-defined range. The controller is designed using a zeroing control barrier function (ZCBF), which facilitates the therapy by reducing control effort when the rider can sustain the desired cadence volitionally. Moreover, the ZCBF design approach certifies the rider's safety by ensuring the desired cadence range is an asymptotically stable set. The effectiveness of the controller is demonstrated with a preliminary experimental result, which shows the cadence constrained within a range of 50 ±8 RPM even when the rider stops pedaling volitionally mid-trial. Additionally, the rider was able to pedal with no intervention from the motor when volitional effort was present.