Adaptive Lower Limb Prosthesis Knee Control
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Solution Overview
Problem
Existing lower limb prostheses for above-knee amputees lack advanced control systems that can accurately adjust knee and ankle flexion in response to various terrains and walking conditions, leading to suboptimal performance and comfort.
Innovation Solution
A lower limb prosthesis with integrated microprocessor control combining hybrid hydraulic and pneumatic systems for the knee and hydraulic damping for the ankle, utilizing a network of sensors to adjust flexion control settings based on kinetic and kinematic parameters, such as shin bending moment, walking speed, and ground inclination, to provide coordinated and adaptive movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If integrated microprocessor control with multiple sensors is implemented to dynamically adjust knee and ankle flexion, then limb function and comfort are improved, but device complexity increases
Solution Approach 1:
The control system is segmented into separate control devices for the knee joint and ankle joint, each with its own flexion control mechanism. This allows independent optimization of each joint's control while maintaining overall integration through the microprocessor system, reducing the complexity burden on any single component.
Solution Approach 2:
The microprocessor control system serves multiple functions: it processes signals from multiple sensors (accelerometer, gyroscope, load cell), controls both knee and ankle flexion, and adapts to various terrains and walking conditions. This multi-functionality consolidates control logic into a single intelligent system, managing complexity through integration rather than multiplication of separate systems.
2Measurement precision
If multiple sensors are used to detect kinetic and kinematic parameters, then measurement precision is improved, but device complexity increases
Solution Approach 1:
Multiple sensors (accelerometer, gyroscope, load cell) are merged into a single sensor network that feeds into the microprocessor control system. This consolidation allows the system to process multiple parameters simultaneously through a unified control architecture, improving measurement precision without proportionally increasing system complexity.
Solution Approach 2:
The microprocessor acts as an intermediary that receives and processes signals from multiple sensors, translating raw sensor data into coordinated control commands for the knee and ankle joints. This intermediary function simplifies the interface between the sensor network and control mechanisms, managing complexity through intelligent signal processing.
3Adaptability or versatility
If hydraulic and pneumatic systems are combined for knee and ankle control, then adaptability to different terrains and speeds is improved, but device complexity increases
Solution Approach 1:
The system dynamically switches between hydraulic and pneumatic control modes depending on the required action and terrain conditions. Hydraulic systems provide precise control for stance phase stability, while pneumatic systems offer compliant motion for swing phase. This dynamic selection of control mechanisms based on operational requirements enhances adaptability while managing complexity through context-dependent activation.
Solution Approach 2:
The patent combines hydraulic actuators for the knee joint with pneumatic actuators for the ankle joint, utilizing the complementary characteristics of both fluid systems. Hydraulic systems provide high force and precision for load-bearing knee control, while pneumatic systems provide compliant, adjustable resistance for ankle dorsiflexion and plantarflexion, together achieving superior terrain and speed adaptability.
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 prosthesis achieves improved limb function and comfort by dynamically adjusting knee and ankle flexion resistance, enabling efficient and natural movement on different terrains and at varying speeds, with enhanced control over stance and swing phases.
Implementation Method 1
the ankle joint includes an hydraulic piston and cylinder assembly providing independent variation of damping resistance
Implementation Method 2
hybrid hydraulic, yielding stance and pneumatic swing control device in the knee
Implementation Method 3
hybrid hydraulic, yielding stance and pneumatic swing control device in the knee
Implementation Method 4
a sensor associated with the ankle joint in the form of an accelerometer mounted, e.g., on the prosthetic foot section
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A lower limb prosthesis comprises an attachment section (10), a shin section (12), a foot section (14), a knee joint (16) pivotally connecting the attachment section (10) and the shin section (12), and an ankle joint (22) pivotally connecting the shin section (12) and the foot section (14). The knee joint includes a dynamically adjustable knee flexion control device (18) for damping knee flexion. The prosthesis further comprises a plurality of sensors (52, 53, 54, 85, 87) each arranged to generate sensor signals indicative of at least one respective kinetic or kinematic parameter of locomotion or of walking environment, and an electronic control system (100) coupled to the sensors (52, 53, 54, 85, 87) and to the knee flexion control device (18) in order dynamically and automatically to modify the flexion control setting of the knee joint (16) in response to signals from the sensors. When the inclination sensor signals indicate descent of a downward incline, the damping resistance of the knee flexion control device (18) is set to a first level during a major part of the stance phase of the gait cycle and to a second, lower level during a major part of the swing phase of the gait cycle. During an interval including a latter part of the stance phase, the knee flexion control device (18) is adjusted so that the damping resistance to knee flexion is between the first and second levels.