Backdrivable Orthotic Actuator with EMG Control
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Solution Overview
Problem
Current options for children with neuromuscular and neurological conditions that impair arm and hand movement, such as cerebral palsy and muscular dystrophy, are limited to rigid splints, physical therapy, medications, and external electrical stimulation, which do not effectively assist in functional rehabilitation.
Innovation Solution
A powered orthotic device with electrically powered, backdrivable linear actuators and an electromyographic sensor array that assists in relative motion of the forearm, upper arm, and hand, allowing for flexion, extension, and grasping motions controlled by volitional biofeedback signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rigid splints and external electrical stimulation are used to assist arm and hand movement, then some form of support is provided, but the effectiveness for functional rehabilitation is insufficient
Solution Approach 1:
The patent replaces traditional mechanical rigid splints with an electrically powered orthotic device that uses electric motors to generate motion. The system substitutes passive mechanical support with active electrical actuation, enabling dynamic control of arm and hand movements through electrical signals that drive motors to assist functional rehabilitation tasks
Solution Approach 2:
The orthotic device incorporates electromyographic sensors that detect voluntary muscle signals from the user and automatically translate them into actuator commands. This self-service mechanism allows the device to respond directly to the user's intent without requiring external control input, enabling intuitive operation where the system serves itself by converting biological signals into mechanical assistance
2Adaptability or versatility
If a powered orthotic device with multiple actuators is implemented to assist arm and hand motion, then functional rehabilitation capability is improved, but device complexity increases
Solution Approach 1:
The patent employs a single multi-functional actuator system that can produce multiple types of motion (flexion, extension, grasping) through a unified mechanical transmission mechanism. The actuator serves multiple functions by routing its output through cable-pulley systems that distribute force to different joints, eliminating the need for separate actuators for each degree of freedom and reducing overall device complexity
Solution Approach 2:
The system uses cable-pulley mechanisms as intermediary elements to transmit mechanical force from the actuator to multiple joints. These intermediaries enable a single actuator to control multiple degrees of freedom by routing cables through pulleys attached to different segments, simplifying the actuator configuration while maintaining versatile functional capability
3Reliability
If EMG sensors and electric actuators are integrated into a portable device, then rehabilitation effectiveness is enhanced, but device portability and compactness are challenged
Solution Approach 1:
The patent integrates EMG sensors, electronic control circuits, and actuator components into a nested hierarchical structure where smaller components are housed within larger assemblies. The sensors are embedded in the orthotic structure, electronic controls are integrated within the actuator housing, and the entire system is contained within a compact portable framework, enabling effective rehabilitation functionality while maintaining portability
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 children with impaired arm and hand function to perform rehabilitation and functional tasks with improved mobility and control, using portable and compact motorized prosthesis that accommodates various sizes and includes adjustable modules for comfort and effectiveness.
Implementation Method 1
electromyographic sensor array that assists in relative motion of the forearm, upper arm, and hand, allowing for flexion, extension, and grasping motions controlled by volitional biofeedback signals
Implementation Method 2
A powered orthotic device with electrically powered, backdrivable linear actuators
Data Source
AI summary
A compact, powered, orthotic device for pediatric use enables the user to control relative motion of the upper arm and the forearm about the elbow and grasping motions of the thumb and fingers. The device is powered by a set of battery-driven, backdrivable linear actuators that are positioned remotely from an arm of the subject. Control of motion of the device by the subject occurs by means of electromyographic signals from a sensor array in contact with skin on the arm of the subject. The sensors in the sensor array may be held in place on the forearm, on the upper arm, or at any other convenient location on the arm.