Prosthesis Stance Controller for Adaptive Torque
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Solution Overview
Problem
Current robotic prostheses face challenges in providing biologically accurate torque across a wide range of walking speeds and ground inclinations, requiring speed-specific tuning and failing to adapt to individual gait cadences, leading to inefficient gait and increased stress on the musculoskeletal system for users with transfemoral amputations.
Innovation Solution
A control framework that enforces quasi-stiffness profiles in the stance phase and employs a minimum-jerk trajectory generator for the swing phase, allowing the prosthesis to generate biologically accurate kinetics and kinematics without the need for user- or speed-specific tuning, using a combination of biomechanical data interpolation and sensor feedback to adjust joint torques based on walking speed and ground inclination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If impedance-inspired control with speed-specific parameter tuning is used, then biologically accurate torque can be provided at a specific walking speed, but the prosthesis function becomes incorrect at other speeds and requires user-specific tuning
Solution Approach 1:
The control system dynamically adjusts impedance parameters based on detected walking speed and gait phase. The stiffness, damping, and equilibrium values are continuously modified according to real-time speed information, allowing the prosthesis to maintain biologically accurate torque across varying speeds without manual retuning for each speed condition
Solution Approach 2:
The system changes control parameters (stiffness, damping, equilibrium) as functions of walking speed and gait phase. By parameterizing the impedance model with speed-dependent values, the prosthesis adapts its torque output to match biological characteristics at different speeds while maintaining a unified control framework that eliminates the need for separate speed-specific tuning
2Reliability
If impedance-inspired control with user-specific tuning is used, then optimal prosthesis function can be achieved for a specific user at a specific speed, but the system becomes infeasible for clinical practice due to tuning complexity
Solution Approach 1:
The control system automatically adapts to each user's gait characteristics and walking speed without requiring manual tuning. By using speed detection and automated parameter adjustment, the prosthesis self-calibrates to match the user's biological characteristics, eliminating the need for clinician or user involvement in the tuning process
Solution Approach 2:
The system incorporates feedback from speed sensors and gait phase detection to continuously adjust impedance parameters. This closed-loop control allows the prosthesis to automatically adapt to varying user conditions and walking speeds, maintaining optimal function without requiring manual intervention or user-specific programming
3Device complexity
If passive prostheses are used, then device simplicity is maintained, but they cannot provide biologically accurate torque and require increased compensatory effort from the user
Solution Approach 1:
The system replaces passive mechanical compliance with active electronic control. Instead of relying on fixed mechanical properties, the prosthesis uses motor actuators controlled by impedance-based algorithms that dynamically adjust torque output, enabling biologically accurate force generation that reduces user compensatory effort and metabolic cost
Data Source
AI summary
Systems and methods are disclosed for operating a joint of a prosthesis during a phase of stance. In an embodiment, a method for such operation comprises determining a joint angle of the joint, determining a walking speed of the prosthesis, retrieving a torque value from a lookup table stored in a memory, on the basis of the joint angle and the walking speed, and initiating a signal to apply a torque to the joint of the prosthesis in an amount based on the torque value.