Multi-axis Robotic Platform for Ankle Neuromechanics
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Solution Overview
Problem
Existing methods fail to accurately characterize the dynamic properties of the ankle joint's neuromuscular interactions during functional tasks, as they are limited to static postures and do not provide insight into mechanical impedance, which is crucial for understanding human motor control and designing advanced wearable robots and exoskeletons.
Innovation Solution
A multi-axis robotic platform that applies position perturbations to the ankle joint in both sagittal and frontal planes, enabling the characterization of mechanical impedance and reflex characteristics by simulating various haptic environments and providing accurate torque responses, with actuators capable of high-speed movements and precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple devices consisting of a servomotor and a cast supporting the leg are used to measure ankle impedance, then the device complexity is reduced, but the adaptability to functional tasks and dynamic properties is limited
Solution Approach 1:
The robotic platform is divided into multiple independent axes (sagittal plane actuator, frontal plane actuator, transverse plane actuator), each capable of performing specific perturbation tasks. This segmentation allows the system to handle complex functional tasks through coordinated simple actuators, resolving the contradiction between device simplicity and task adaptability.
Solution Approach 2:
The robotic platform is designed with multi-functional capabilities to perform various ankle perturbation tasks across different planes (sagittal, frontal, transverse) and under different conditions (static, dynamic, seated, standing). This universal design enables a single device to study diverse neuromuscular interactions without requiring multiple specialized devices.
2Device complexity
If simple devices are used for measuring ankle impedance, then the device complexity is reduced, but the measurement precision for dynamic properties and mechanical impedance is insufficient
Solution Approach 1:
The robotic platform incorporates feedback mechanisms where torque sensors measure the torque applied to the ankle joint, and position sensors measure the resulting angular displacement. This feedback loop enables precise calculation of mechanical impedance (torque-to-position transfer function) across different frequencies and conditions, achieving high measurement precision despite relatively simple device architecture.
Solution Approach 2:
The system replaces simple mechanical measurement approaches with a controlled robotic actuation system that can apply precise, repeatable perturbations across multiple planes. The use of electronic torque sensors and position sensors substitutes for complex mechanical measurement apparatus, enabling accurate dynamic impedance characterization.
3Ease of operation
If conventional gait lab measurements of quasi-stiffness are used, then the ease of operation is improved, but the measurement precision for dynamic mechanical impedance is insufficient
Solution Approach 1:
The robotic platform transitions from static measurement conditions to dynamic perturbation conditions, applying time-varying forces across different frequencies. This dynamic approach enables the system to measure frequency-dependent mechanical impedance properties (stiffness, damping, inertia) that cannot be captured by static quasi-stiffness measurements, while maintaining ease of operation through automated control.
Data Source
AI summary
A multi-axis robotic platform for studying neuromechanics comprises a bottom plate, a middle plate, and a top plate is disclosed herein. The middle plate is movably coupled between the bottom plate and the top plate. The top plate comprises a support surface for receiving an ankle. A first actuator is disposed upon the bottom plate and is connected to the middle plate via a first coupling such that a shaft of the first actuator rotates the middle plate along a dorsiflexion-plantarflexion (DP) axis of the ankle. A second actuator is disposed upon the middle plate and is connected to the top plate via a second coupling such that a shaft of the second actuator rotates the top plate along an inversion-eversion (IE) axis of the ankle. The multi-axis robotic platform can analyze ankle impedance and reflex characteristics in two degrees-of-freedom (DP movement and IE movement) during postural and locomotion tasks.