Trunk Support Exoskeleton Actuator Design for Lumbar Flexion
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Solution Overview
Problem
Existing exoskeleton systems fail to effectively reduce muscle forces in the wearer's back during forward lumbar flexion, such as when stooping or bending.
Innovation Solution
A trunk-supporting exoskeleton with a supporting trunk frame coupled to the wearer's trunk, first and second thigh links rotatably coupled to the supporting trunk, and an electric motor with a transmission system generating actuator torque to provide extension torques between the thigh links and the supporting trunk, thereby resisting bending motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a trunk support exoskeleton is designed to reduce muscle forces during lumbar flexion, then back muscle force reduction is improved, but device complexity increases
Solution Approach 1:
The patent combines the actuator housing and shaft into a single integrated unit that serves dual functions: the housing acts as one of the thigh links while the shaft provides the actuation mechanism. This merging eliminates the need for separate components, reducing overall device complexity while maintaining the ability to generate extension torque to counteract lumbar flexion forces.
Solution Approach 2:
The actuator housing is designed to serve multiple purposes: it functions as a structural thigh link, houses the actuation mechanism, and provides mounting points for pulleys and lines. This multi-functionality reduces the total number of components needed in the exoskeleton system, addressing the complexity issue while still achieving back muscle force reduction.
2Object-affected harmful factors
If the actuator generates torque to resist bending motion, then lumbar flexion support is improved, but ease of operation during walking deteriorates
Solution Approach 1:
The exoskeleton employs dynamic pulleys with variable radii that change based on the relative positions of the thigh links and trunk. This dynamic adjustment allows the system to optimize torque generation during lumbar flexion while minimizing resistance during walking motions, thereby maintaining ease of operation during mobility activities.
Solution Approach 2:
The system changes the mechanical parameters (pulley radii, line tensions) based on the operational state. During lumbar flexion, the parameters are configured to maximize support torque, while during walking, the parameters adjust to reduce resistance, thus resolving the contradiction between support and ease of operation.
3Force
If a planetary gear transmission system is used to generate actuator torque, then force multiplication is improved, but device complexity increases
Solution Approach 1:
The planetary gear system is integrated directly into the actuator housing structure, with the ring gear formed as part of the housing itself and the sun gear mounted on the shaft. This merging of transmission components with structural elements eliminates the need for separate transmission housings and mounting mechanisms, reducing overall device complexity while maintaining force multiplication capabilities.
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 exoskeleton significantly reduces muscle forces in the wearer's back during forward lumbar flexion while allowing for free movement during activities like walking, ascending stairs, and climbing.
Implementation Method 1
The motor is configured to generate torque on the motor shaft relative to the motor housing
Implementation Method 2
The transmission system comprising a ring gear, a carrier gear, and a sun gear. The sun gear is coupled to the motor shaft, and the motor generates an actuator torque between the ring gear and the carrier gear
Implementation Method 3
The actuator torque between the carrier gear and the ring gear generates a tensile force in the ring gear line, thereby providing an extension torque between the first thigh link and the supporting trunk
Data Source
AI summary
A trunk-supporting exoskeleton for reducing muscle forces in a wearer's back during forward lumbar flexion comprises a supporting trunk, a first thigh link, a second thigh link, and an actuator, which includes an actuator first element and an actuator second element. When the wearer is in a forward-bent position, the actuator generates a first torque on the actuator first element and a second actuator torque on the actuator second element to generate extension torques between the first and second thigh links and the supporting trunk, thereby resisting bending motion of the supporting trunk in the forward-bent position. When the wearer is not in the forward-bent position, the actuator generates a substantially small first torque and second torque, resulting in small resistance to the movement of the thigh links relative to the supporting trunk during walking.