Trunk Exoskeleton Torque Control for Lumbar Support
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Solution Overview
Problem
Conventional back support devices fail to differentiate between walking and bending, leading to discomfort and hazards in industrial settings, as they require the wearer to push against the device during these activities, restricting movement.
Innovation Solution
A trunk supporting exoskeleton with torque generators that only impose resisting torque when the wearer bends forward beyond a predetermined angle, reducing muscle forces in the back by providing support only during lumbar flexion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional passive spring resistance devices are used to create torque during bending, then the probability of injury of the L5/S1 area of the spine is greatly reduced, but the wearer cannot walk or sit comfortably since the legs must push against the devices during these activities
Solution Approach 1:
The exoskeleton employs a dynamic control system that actively adjusts torque generation based on real-time detection of wearer posture and movement state. The control system distinguishes between walking, sitting, and bending activities, applying resisting torque only during forward lumbar flexion while eliminating torque during walking and sitting, thereby resolving the contradiction between injury prevention and comfort during various activities
Solution Approach 2:
The system incorporates sensors that continuously monitor the angle between the trunk and legs, as well as the state of the knee joints. This feedback mechanism enables the control system to detect when the wearer is walking versus bending, and accordingly modulate the torque output of the actuators to provide support only when needed during lumbar flexion
2Reliability
If passive spring resistance devices provide continuous torque, then spinal support is maintained, but the wearer's movement is restricted and the device becomes hazardous in industrial settings
Solution Approach 1:
The system transitions from static continuous torque provision to dynamic conditional torque application. The exoskeleton remains adaptable to different industrial tasks by using the control system to determine when torque should be applied based on real-time posture detection, allowing unrestricted movement during appropriate activities while maintaining spinal support during bending tasks
3Reliability
If torque generators are activated during the entire range of motion, then continuous support is provided, but muscle forces during bending are not effectively reduced
Solution Approach 1:
The exoskeleton applies torque locally and selectively at the hip joint during forward lumbar flexion, rather than providing uniform continuous support throughout the entire range of motion. This localized torque application precisely counteracts the gravitational moment during bending while allowing natural movement during walking and sitting, effectively reducing muscle forces where needed without over-supporting other movements
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 comfortable walking and sitting by minimizing muscle forces during bending, thus preventing injuries and improving mobility without restricting movement.
Implementation Method 1
two torque generators located on both left and right halves of the wearer substantially close to the wearer's hip. The torque generators couple the supporting trunk to the respective thigh links and are configured to generate torque between the thigh links and the supporting trunk
Implementation Method 2
when the wearer bends forward in the sagittal plane such that a predetermined portion of the supporting trunk passes beyond a predetermined angle from the vertical gravity line
Data Source
AI summary
A trunk supporting exoskeleton comprises: a supporting trunk; thigh links configured to move in unison with a wearer's thighs; and first and second torque generators located on both left and right halves of the wearer substantially close to the wearer's hip. The torque generators couple the supporting trunk to the thigh links, and generate torque between the thigh links and the supporting trunk. When the wearer bends forward such that a predetermined portion of the supporting trunk passes beyond a predetermined angle from vertical, a torque generator(s) imposes a resisting torque between the supporting trunk and the thigh link(s), causing the supporting trunk to impose a force against the wearer's trunk, and the thigh link(s) to impose a force onto the wearer's thigh. When the predetermined portion does not pass beyond the predetermined angle, the torque generators impose no resisting torques between said supporting trunk and respective thigh links.