Biomimetic Transfemoral Prosthesis Series-Elastic Actuator Control
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Solution Overview
Problem
Conventional prosthetic leg systems, particularly for transfemoral amputees, fail to provide a biomimetic response, leading to balance issues, increased metabolic energy expenditure, and reduced walking speed due to non-biomimetic ankle-foot and knee designs, inefficient actuator systems, and poor terrain adaptation.
Innovation Solution
A prosthetic system incorporating a series-elastic actuator (SEA) with neuromuscular-inspired control and intrinsic inertial sensing, utilizing a high-torque transverse-flux motor and muscle-tendon unit (MTU) architecture to emulate biological muscle-tendon units, enabling efficient and adaptive joint torque control across various terrains and speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional passive-elastic ankle-foot prostheses are used, then the device structure is simple, but the metabolic energy consumption increases and walking speed decreases
Solution Approach 1:
The patent replaces the conventional passive-elastic mechanical ankle-foot prosthesis with a powered robotic ankle-foot prosthesis that uses electric motors, sensors, and control systems to actively generate torque and control joint movement, thereby reducing metabolic energy consumption and improving walking speed
Solution Approach 2:
The prosthesis incorporates inertial sensors and control algorithms that enable the device to autonomously adapt to terrain changes and user gait patterns without requiring manual adjustment, providing self-regulating energy-efficient operation
2Device complexity
If conventional passive-elastic ankle-foot prostheses are used, then the device structure is simple, but the walking speed decreases
Solution Approach 1:
The patent replaces the passive-elastic mechanical system with an active powered system using electric motors and control algorithms that can dynamically adjust ankle joint torque to propel the user forward, thereby increasing walking speed
Solution Approach 2:
The prosthesis transitions from a static passive-elastic design to a dynamic powered system that can actively modulate joint torque and adapt to varying terrain and walking conditions, enabling faster and more natural gait patterns
3Power
If high gear-ratio transmissions are employed to deliver increased power, then the joint power output increases, but the motor heating increases and battery power is dissipated excessively
Solution Approach 1:
The patent replaces high gear-ratio mechanical transmissions with direct-drive or low-gear-ratio electric motor systems that deliver high torque at low speeds, eliminating excessive motor heating and battery power dissipation while maintaining high joint power output
Solution Approach 2:
The prosthesis changes the motor operating parameters by using high-torque low-speed motors instead of high-RPM motors with high gear ratios, thereby reducing motor heating and improving energy efficiency while delivering the necessary joint power
4Measurement precision
If explicitly controlled systems are used to match biological behavior, then the control precision can be high, but the system requires extensive tuning and becomes complex
Solution Approach 1:
The patent implements self-tuning control algorithms that automatically adapt to the user's gait patterns and terrain conditions without requiring manual calibration, achieving high control precision while minimizing system complexity
Solution Approach 2:
The prosthesis uses inertial sensors and control algorithms that continuously monitor gait parameters and automatically adjust control signals to match biological behavior, achieving precise control through feedback rather than extensive manual tuning
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 system significantly reduces metabolic energy consumption, normalizes walking speed, and improves gait stability and symmetry, providing a more natural and efficient walking experience for amputees by mimicking biological biomechanics.
Implementation Method 1
employing a series-elastic actuator (SEA) 202, motor technology, neuromuscular-inspired actuator control, and intrinsic inertial sensing
Implementation Method 2
A wearable of the biomimetic prosthesis may experience an improved walking speed, metabolic economy, gait symmetry, and gait stability across level, sloped, and stair ground surfaces when compared to conventional prostheses
Data Source
AI summary
In an artificial limb system having an actuator coupled to a joint for applying a torque characteristic thereto, a control bandwidth of a motor controller for a motor included in the actuator can be increased by augmenting a current feedback loop in the motor controller with a feed forward of estimated back electromotive force (emf) voltage associated with, the motor. Alternatively, the current loop is eliminated and replaced with a voltage loop related to joint torque. The voltage loop may also be augmented with the feed forward of estimated back emf, to improve the robustness of the motor controller.