Control of Magnetorheological Fluid Brake for Medical Ergometers based on Cycling Model

Bicycle ergometers offer a convenient means of exercise independent of outdoor conditions, finding application not only in sport and leisure but also in medical diagnostics and rehabilitation. Existing models predominantly employ eddy current brakes, necessitating additional components like planetary gearboxes and flywheels to compensate for speed-dependent torque. Magnetorheological fluid (MRF) brakes represent a promising alternative, offering precise torque adjustment regardless of speed. This paper presents a control scheme of an MRF-based ergometer optimized for medical rehabilita-tion and competitive sports. A brief overview of MRF-based actuators provides the foundation for discussing the ergom-eter's implementation, control system, and experimental validation. A cascaded control system was design, in which a low level control strategy optimizes the torque adjustment, utilizing dynamic feedforward and nonlinear compensation structure. And a high level control is used, to accurately replicate real-world driving behavior of a bicycle in a Hardware-in-the-Loop (HiL) test bench. Finally, experimental results demonstrate the effectiveness of the developed MRF-based ergometer, offering precise control and realistic driving behavior.