Semi-Powered Exoskeleton Knee Torque Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Individuals face difficulties in carrying heavy or bulky objects while walking on slopes or stairs due to fatigue and potential injury, as existing solutions do not provide efficient assistance for these tasks.
Innovation Solution
A semi-powered lower extremity exoskeleton with two leg supports and an exoskeleton trunk, equipped with torque generators and a power unit that injects power during stance phases on slopes or stairs, while minimizing resistance during swing phases and conserving energy when not needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fully powered exoskeleton is used to assist carrying loads on slopes, then the assistance capability is improved, but the energy consumption and device complexity increase significantly
Solution Approach 1:
The patent applies partial action by providing powered assistance only during the stance phase when the foot is on the ground and support is needed, while the torque generator provides passive resistance or minimal resistance during the swing phase. This selective application of power reduces energy consumption while maintaining assistance capability when most needed.
Solution Approach 2:
The exoskeleton operates in periodic cycles, switching between powered mode during stance phase and passive/minimal resistance mode during swing phase. This periodic modulation of power delivery aligns with the natural gait cycle, providing assistance when needed and conserving energy during transition phases.
2Reliability
If a fully powered exoskeleton is used to assist carrying loads on slopes, then the assistance capability is improved, but the device complexity increases
Solution Approach 1:
The system uses partial action by engaging the torque generator only when needed (during stance phase on slopes), rather than continuously. This reduces the complexity requirements for control systems and power management while maintaining assistance capability when most beneficial.
Solution Approach 2:
The exoskeleton leverages the user's own movement and the passive mechanical properties of the torque generator to provide assistance. The device serves itself by using the user's gait cycle to trigger appropriate assistance modes, reducing the need for complex sensors and control algorithms.
3Stability of the object's composition
If the torque generator provides resistance during swing phase to maintain stability, then the stability is improved, but the ease of movement decreases
Solution Approach 1:
The torque generator dynamically adjusts its characteristics based on the gait phase. During swing phase, it provides minimal resistance to allow easy leg movement, while during stance phase it provides appropriate resistance or assistance for stability and load carrying. This dynamic adaptation resolves the contradiction between stability and ease of movement.
Solution Approach 2:
The system periodically switches between providing resistance and minimal resistance based on the gait cycle phase. This periodic modulation ensures stability is provided when the foot is planted and support is needed, while ease of movement is maintained during the swing phase when the leg needs to move freely.
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
Enables efficient and safe carrying of loads on slopes or stairs by providing powered assistance during stance phases and reducing energy consumption during swing phases, thereby alleviating user fatigue and injury risks.
Implementation Method 1
the power unit does not dissipate any stored power in said power unit, but forces the torque generator to resist flexion of the respective knee joint
Implementation Method 2
the power unit does not dissipate any stored power in said power unit, but forces the torque generator to minimize its resistance to knee flexion and extension
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The lower extremity exoskeleton comprises two leg supports connectable to person's lower limbs and configured to rest on the ground during their stance phase. Each leg support comprises a thigh link and a shank link; a knee joint configured to allow flexion and extension between the shank link and the thigh link. The lower extremity exoskeleton further comprises an exoskeleton trunk connectable to the person's upper body. The exoskeleton trunk is connectable to the thigh links of the leg supports allowing for the flexion and extension between the leg supports and the exoskeleton trunk. Two torque generators are coupled to each of the knee joints. A power unit, capable of providing power, is coupled to the torque generators. In operation when a leg support is in a stance phase and climbing a slope or stairs, the power unit injects power into the respective torque generator thereby extending the respective knee angle. When a leg support is in stance phase and not climbing a slope or stairs, the power unit does not inject any power to the respective torque generator, but without dissipating any stored power in said power unit, it forces the torque generator to resist flexion of the respective knee joint. When a leg support is in a swing phase, the power unit does not inject any power to the respective torque generator, but without dissipating any stored power in said power unit, it forces the torque generator to minimize its resistance to knee flexion and extension.