Prosthetic Ground Contact Sensor Array With Compliant Load Discrimination
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Solution Overview
Problem
Existing lower-limb prosthetic and orthotic devices face challenges with high costs, complex integration requirements, and inadequate handling of asymmetry in acceleration spikes during transitions, leading to reduced performance and reliance on advanced signal processing.
Innovation Solution
A sensor array with non-contact displacement sensors is used to detect ground contact, comprising a first and second body with sensors that measure changes in distance between them, generating data for control signals, and employing a selectively compliant mechanical structure to differentiate between torque and axial loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If advanced signal processing and interpretation are used to handle asymmetry in acceleration spikes, then ground contact detection accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex electronic signal processing systems with a mechanically compliant sensor mounting structure. The compliant mounting passively filters acceleration spikes through its mechanical properties, eliminating the need for advanced digital signal processing algorithms while maintaining ground contact detection accuracy.
Solution Approach 2:
The compliant mounting structure acts as an intermediary between the sensor and the prosthetic device structure. It mediates the transmission of mechanical loads to the sensor, selectively allowing ground contact forces to pass through while blocking harmful acceleration spikes, thereby simplifying the overall system requirements.
2Measurement precision
If sensor array with compliant mechanical structure is used, then sensitivity around zero-load point is improved, but mechanical response to torque loads increases
Solution Approach 1:
The compliant mounting structure exhibits different mechanical properties in different directions. It is designed to be compliant in the direction of ground contact forces to maximize sensitivity around zero-load points, while being stiffer in directions that would transmit torque loads, thereby selectively filtering mechanical responses.
Solution Approach 2:
The mounting structure employs asymmetric compliance characteristics, being more compliant for axial ground contact forces than for torque loads. This asymmetry allows the sensor to detect subtle ground contact events while remaining insensitive to rotational torque disturbances.
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 provides robust control of lower-limb prosthetics by maximizing sensor sensitivity around zero-load points, reducing installation precision needs, and accurately detecting load progression directions, while minimizing sensitivity to inertial loads and overcoming calibration complexities.
Implementation Method 1
A sensor array for the lower-limb POD may include two or more sensors, which may be non-contact displacement sensors... The plurality of sensors may comprise Hall effect sensors and the respective target portions of the second body comprise magnets.
Data Source
AI summary
Systems, devices and methods for detecting ground contact with a lower-limb POD. A sensor array for the POD on a first or second body may include two or more sensors in an array that each detect a distance to a respective target on the other of the first or second body. The first and second bodies may move relative to each other thereby changing an offset distance or distances between the two bodies which is detected by the sensors. In some embodiments, the sensors may include Hall Effect sensors that detect distances to respective magnets. Load data based on the detected distances may be generated for control of the POD, such as for stance phase control.