Assist-As-Needed FES Control for Force-Occlusion Measurement
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Solution Overview
Problem
Current assistive functional electrical stimulation (FES) systems fail to accurately determine patient effort, leading to slacking and reduced rehabilitation effectiveness due to force occlusion and EMG interference, which can result in permanent disabilities.
Innovation Solution
A closed-loop feedback system that measures both volitional and stimulated muscle forces to adjust FES accordingly, preventing slacking and enhancing rehabilitation by providing assistance as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If FES is applied to assist muscle movement, then patient mobility is improved, but patient effort measurement becomes inaccurate due to force occlusion
Solution Approach 1:
The patent segments the total muscle force into distinct components: volitional force (from patient effort) and stimulated force (from FES). By using separate measurement channels and signal processing techniques, the system can isolate and measure volitional force independently even when FES is actively assisting movement, thereby resolving the measurement inaccuracy caused by force occlusion
Solution Approach 2:
The patent introduces an intermediary measurement system that uses surface electromyography (sEMG) signals as a mediator to indirectly assess volitional muscle activation. Since sEMG detects electrical activity in muscles before mechanical force is produced, it provides a proxy measure of patient effort that is not directly affected by the mechanical occlusion of FES forces
2Reliability
If FES stimulation force is increased to assist movement, then rehabilitation effectiveness is improved, but slacking behavior increases due to reduced patient effort requirement
Solution Approach 1:
The patent implements a closed-loop feedback system that continuously monitors measured patient effort via sEMG and force sensors, then dynamically adjusts FES stimulation parameters in real-time. When patient effort is sufficient, FES assistance is reduced or withheld; when patient effort is insufficient, FES provides targeted support. This feedback mechanism ensures that higher stimulation forces are only applied when medically necessary, maintaining both rehabilitation effectiveness and patient engagement
Solution Approach 2:
The patent makes the FES system dynamic by enabling real-time adjustment of stimulation parameters based on current patient performance and effort levels. Rather than applying fixed stimulation protocols, the system adapts stimulation intensity and timing to match patient capabilities, thereby preventing slacking while preserving rehabilitation effectiveness through optimized force assistance
3Reliability
If FES is applied continuously to ensure movement completion, then task achievement is improved, but patient effort differentiation becomes impossible
Solution Approach 1:
The patent employs periodic assessment of patient effort through continuous sEMG monitoring during FES-assisted movements. By analyzing sEMG signal characteristics at specific intervals and comparing them against baseline measurements, the system can differentiate between genuine fatigue (reduced capacity) and slacking (reduced effort) even when movement is being assisted by FES, thus maintaining both task completion and effort measurement accuracy
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 system effectively differentiates between fatigue and slacking, ensuring patients engage actively, thereby improving rehabilitation outcomes and muscle recovery.
Implementation Method 1
The at least one stimulating electrode provides an electrical signal to at least a first muscle of the one or more muscles of the user. The electrical signal can be used for FES and can cause a stimulated muscle force.
Implementation Method 2
The at least one measuring device records data indicative of at least one movement of one or more muscles of a user. The data indicative of the at least one movement the one or more muscles includes both the stimulated muscle force and the volitional muscle force.
Data Source
AI summary
Functional Electrical Stimulation (FES) can be applied to a user in an assist as needed manner using a closed feedback loop based on user effort. A system can include at least one measuring device to record data indicative of a movement of at least one muscle, at least one stimulating electrode to provide an electrical signal to a muscle, and a controller to implement the closed feedback loop. The controller can instruct the user to try to perform a movement, apply the electrical signal, receive the recorded data, estimate an effort expended by the user, correct the effort expended by the user, determine if the electrical signal should be altered based on at least the user's effort, and if needed, alter the electrical signal. The controller can correct the effort based on a volitional muscle force, a stimulated muscle force, and an occlusion between the two.