Powered Orthotic Actuator Positioning for Hemiparesis Rehabilitation
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Solution Overview
Problem
Individuals with hemiparesis due to stroke or brain injury face difficulty in performing rehabilitation exercises due to severe weakness in limbs, requiring assistance to execute functional tasks that aid motor pattern re-learning.
Innovation Solution
A powered orthotic device with an electromyographic sensor and actuator assembly that applies forces based on muscle activity, allowing for adjustable assistance levels and operational modes to facilitate rehabilitation and functional tasks, including asymmetric control algorithms to mimic natural motion patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If passive orthotic braces are used to support limbs with hemiparesis, then structural support and stability are provided, but the patient cannot actively perform rehabilitation exercises or execute functional tasks due to severe muscle weakness
Solution Approach 1:
The patent replaces passive mechanical support structures with an active electromechanical system that includes EMG sensors, microprocessors, and actuators. This system detects muscle activity through EMG signals and provides powered assistance through actuators coupled to the orthotic brace, enabling patients with severe weakness to actively perform rehabilitation exercises that would be impossible with passive braces alone.
Solution Approach 2:
The orthotic device incorporates EMG sensors that detect the patient's own residual muscle activity to trigger and control actuator assistance. The system uses the patient's voluntary muscle contractions as control signals, allowing the device to respond to and amplify the patient's own motor intentions rather than requiring external control input.
2Productivity
If powered actuators are added to provide active assistance for rehabilitation exercises, then functional capacity and exercise execution ability are enhanced, but device complexity and control system requirements increase
Solution Approach 1:
The system employs EMG feedback by continuously monitoring muscle electrical activity and using these signals to control actuator output. The microprocessor processes EMG signals in real-time to determine when and how much assistance to provide, creating a closed-loop control system that automatically adjusts support based on the patient's instantaneous muscle activity levels.
Solution Approach 2:
The orthotic device integrates multiple functions into a single system: EMG signal acquisition through sensors, signal processing and control decisions through a microprocessor, mechanical support through the brace structure, and powered assistance through actuators. This multi-functional integration reduces overall system complexity compared to separate systems for each function.
3Force
If the actuator assembly is positioned to provide effective torque about the joint, then assistive force application is optimized, but the device occupies more volume and may interfere with natural limb motion
Solution Approach 1:
The patent positions the actuator assembly in the outside region of the brace (laterally displaced from the limb axis) rather than attempting to place it directly on the limb. This lateral positioning in another spatial dimension allows the actuator to apply effective torque through the brace structure without interfering with the natural anterior-posterior motion of the limb, while minimizing volume occupation in the motion path.
Solution Approach 2:
The brace structure serves as an intermediary between the laterally positioned actuator assembly and the limb joint. The actuator applies force to the brace, which then transmits the torque to the joint through its mechanical coupling, allowing the actuator to be positioned away from the joint axis while still providing effective rotational assistance.
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
Enhances the wearer's functional capacity by providing assistive torques and forces, promoting motor pattern re-learning and rehabilitation by mimicking natural motion and force patterns, even in cases of asymmetric muscle control.
Implementation Method 1
an electromyographic sensor and actuator assembly in communication with the electromyographic sensor
Data Source
AI summary
A powered orthotic device includes a brace having a first section and a second section, the first section and the second section operationally coupled at a pivot, the first and the second sections moving about the pivot to define flexion and extension directions, such directions defining inside and outside regions of the brace respectively. The device further includes at least one set of straps that removably attach the first section and the second section to a corresponding limb segment such that the pivot is proximate to a joint between each limb segment. The device also includes and an electromyographic sensor and an actuator assembly in communication with the electromyographic sensor, the actuator assembly mounted to the brace, and occupying a volume of which a majority is disposed proximately to the outside region of the brace, and coupled to the first and second sections of the brace so as to apply a force for driving the first and second sections about the pivot, the force based on signals from the electromyographic sensor.