Volitional Knee Control via Surface EMG Impedance Modulation

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Solution Overview

Problem

Conventional prosthetic knee joints require physical input from users for control, especially during non-weight-bearing activities like sitting or standing, which limits volitional control and natural movement.

Innovation Solution

A system using surface electromyography (EMG) to generate velocity references for powered knee joints, allowing volitional control through impedance modulation, enabling users to control knee movement without significant physical input by interpreting muscle intent and co-contraction patterns.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional passive knee prostheses are used, then the device structure is simple and energy consumption is low, but the user must provide significant physical input for control and volitional control capability is lost

Engineering Contradiction:

Improvevolitional control capabilityVSAvoiddevice structure

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent replaces the purely mechanical control system with a hybrid electromechanical system. Surface EMG sensors detect muscle electrical signals to determine user intent, which then drives the powered knee joint through motor actuation. This substitution of mechanical sensing and control with electrical/biological signal processing enables volitional control while reducing the need for physical manipulation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces surface EMG sensors as an intermediary between the user's muscle intent and the powered knee joint. These sensors detect electrical signals from the skin surface overlying the muscle, providing a non-invasive interface that translates physiological intent into control commands without requiring direct physical contact or manipulation of the prosthesis.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If powered knee prostheses with physical input sensors are used, then control during weight-bearing activities is improved, but control during non-weight-bearing activities remains limited

Engineering Contradiction:

Improvecontrol across activity typesVSAvoidcontrol during non-weight-bearing activities

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The patent implements a universal control interface using surface EMG sensors that functions across all activity types. The same sensor system and signal processing architecture serve both weight-bearing and non-weight-bearing activities, eliminating the need for activity-specific control mechanisms. The EMG-based intent detection works whether the user is standing, sitting, or performing any other activity, providing consistent volitional control capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Use of energy by moving object

If traditional dissipative knee prostheses are used, then the device is simple and reliable, but the user must provide energy for movement and natural gait mechanics are disrupted

Engineering Contradiction:

Improveenergy exchange during gaitVSAvoidnatural movement capability

Core Design Contradiction:

Use of energy by moving objectVSEase of operation

Solution Approach 1:

The patent implements a feedback control system where surface EMG signals provide real-time information about user muscle activation and intent. This feedback loop allows the powered knee joint to respond dynamically to the user's physiological state, adjusting torque and movement characteristics to match natural gait patterns. The system continuously monitors EMG signals and modifies actuation accordingly, enabling energy-efficient movement that respects the user's natural biomechanics.

Inventive Principle:

Principle #23Feedback

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

Enables effective volitional control of knee joints during non-weight-bearing activities, achieving trajectory tracking performance close to that of intact knees, with reduced reliance on artificial manipulation and improved interaction with the environment.

Implementation Method 1

A system using surface electromyography (EMG) to generate velocity references for powered knee joints

Methodology Applied

Scientific EffectElectromyography (EMG): Electromagnetic Induction

Data Source

PatentUS10517745B2Systems and method for volitional control of jointed mechanical device based on surface electromyography

Publication Date: 2019.12.31 VANDERBILT UNIV

AI summary

Systems and methods for controlling a weight bearing member having at least one powered joint are provided. A system includes a velocity reference module for receiving myoelectric control signals from a user during a non-weight bearing mode for the powered joint and generating a velocity reference for the powered joint based on the myoelectric control signals. The system further includes a volitional impedance module for generating a torque control signal for actuating the powered joint based at least on the velocity reference.