FES Cycling Controller Torque Feedback RISE Control
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Solution Overview
Problem
Functional electrical stimulation (FES) devices, particularly for cycling, face challenges such as nonlinear muscle responses, muscle spasticity, and metabolic inefficiency, leading to low power output and muscle fatigue during rehabilitation and exercise for individuals with upper motor neuron lesions.
Innovation Solution
A hybrid orthotic device with sensors and a controller that dynamically generates control signals for electrical stimulation based on torque transfer ratios, using a Robust Integral of the Sign of the Error (RISE) control method and adaptive learning techniques to manage muscle fatigue and electromechanical delays, allowing for efficient and stable cycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If FES is applied to produce functional outcomes such as cycling, then rehabilitation benefits and muscle activation are improved, but power output remains low and metabolic efficiency is poor
Solution Approach 1:
The system dynamically adjusts stimulation parameters in real-time based on measured crank position and velocity. The controller modifies stimulation duty cycles and patterns according to the instantaneous mechanical state, transforming static FES application into a dynamic control system that optimizes power transfer throughout the cycling motion.
Solution Approach 2:
The system implements closed-loop feedback by continuously measuring crank position and velocity, comparing these to desired trajectories, and adjusting stimulation parameters accordingly. This feedback mechanism enables real-time optimization of muscle activation timing and intensity to maximize power output while maintaining functional reliability.
2Ease of operation
If electrical stimulation is applied to evoke muscle contractions, then motor function restoration is improved, but muscle fatigue develops rapidly
Solution Approach 1:
The system employs periodic stimulation patterns that are synchronized with the cycling motion cycles. By delivering stimulation in periodic bursts aligned with the mechanical cycle rather than continuous activation, the system maintains motor function while allowing muscle recovery periods, thereby extending effective action duration and reducing fatigue accumulation.
Solution Approach 2:
The controller applies stimulation at partial duty cycles rather than maximum intensity continuously. By providing just sufficient stimulation to achieve the required motor output and avoiding excessive activation, the system extends muscle action duration while maintaining ease of operation for functional restoration.
3Reliability
If FES cycling is implemented for rehabilitation, then physiological benefits are improved, but there is a time lag between stimulation and muscle force output
Solution Approach 1:
The system applies electrical stimulation in advance of the desired muscle force output, anticipating the electromechanical delay. By triggering stimulation before the optimal mechanical moment, the system compensates for the time lag between electrical input and muscular response, ensuring that force is generated at the correct point in the cycling motion while maintaining physiological benefit reliability.
4Power
If stimulation parameters are increased to improve power output, then cycling efficiency may improve, but muscle spasticity and nonlinear responses increase
Solution Approach 1:
The closed-loop feedback system continuously monitors crank position and velocity and adjusts stimulation parameters in real-time, preventing excessive stimulation that could trigger spasticity. The feedback mechanism enables the system to achieve adequate power output while automatically regulating stimulation intensity to avoid harmful nonlinear muscle responses.
Solution Approach 2:
The system dynamically modulates stimulation parameters according to the instantaneous mechanical state rather than applying fixed high-intensity stimulation. This dynamic adjustment allows the system to optimize power output at each phase of the cycling motion while avoiding stimulation levels that would provoke muscle spasticity and nonlinear responses.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the efficiency and power output of FES-induced cycling by accurately controlling muscle stimulation, reducing fatigue, and improving tracking errors, enabling more effective rehabilitation and exercise for individuals with motor impairments.
Implementation Method 1
a controller, coupled to the at least one sensor. The controller is programmed to generate functional electrical stimulation to a person using the exercise device
Data Source
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AI summary
Functional electrical stimulation (FES) cycling devices and associated methods are generally described. An FES cycling device may comprise a crank, two or more pedals connected to the crank, one or more sensors adapted to measure position and/or velocity of the crank, and one or more electrodes configured to deliver electrical stimulation to a person associated with the cycling device. In some cases, the FES cycling device further comprises a controller configured to receive input signals from the one or more sensors and deliver output signals to the one or more electrodes. In certain cases, the controller may dynamically generate a control signal to deliver an amount of electrical stimulation to a muscle group (e.g., quadriceps femoris, gluteal muscles, hamstring muscles) based on the value of a determined torque transfer ratio between a joint of the person and the crank of the cycling device. The electrical stimulation may, in some cases, cause the person to pedal the cycling device.