Wearable Robot Torque Control via Multi-Joint Sensor Feedback
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Solution Overview
Problem
Wearable robots struggle to provide real-time assistive torque adjustments based on the wearer's motion intentions, such as speed changes or motion stops, which can lead to discomfort and inefficiency in tasks like walking, sitting, or standing.
Innovation Solution
A wearable robot system that includes sensors to measure joint angles and angular velocities, a controller to calculate target joint angles and assistive torque, and a mechanical unit with actuators to apply the calculated torque, allowing for real-time adjustments to assistive torque based on the wearer's motion intentions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If assistive torque is applied to support muscle strength, then the wearer's ability to perform daily motions is improved, but the system fails to adjust in real-time to the wearer's motion intentions causing discomfort
Solution Approach 1:
The system employs feedback mechanisms by detecting the wearer's actual motion state through sensors (joint angles, angular velocities) and comparing it with intended motion to calculate appropriate assistive torque. This closed-loop control enables real-time adaptation to the wearer's motion intentions, resolving the contradiction between providing stable assistance and adapting to changing motion needs.
Solution Approach 2:
The assistive torque is dynamically adjusted based on real-time detection of joint angles and angular velocities of multiple joints. The control system modifies the torque magnitude and direction according to the wearer's current motion state and intended motion, enabling the system to adapt flexibly to various daily motions while maintaining comfort.
2Measurement precision
If multiple joints are controlled independently, then each joint receives targeted assistance, but the coordination between joints deteriorates leading to unnatural motion
Solution Approach 1:
The system merges the control of multiple joints into a coordinated system. By detecting joint angles and angular velocities of multiple joints simultaneously and calculating target joint angles considering the motion of other joints, the system ensures natural coordination between joints while providing precise targeted assistance to each joint.
Solution Approach 2:
The control system performs multiple functions simultaneously: it detects joint angles, calculates angular velocities, determines target joint angles based on multi-joint coordination, and calculates assistive torque. This multi-functional approach ensures that precise measurement of individual joints does not compromise the overall coordination stability.
3Force
If assistive torque is increased to reduce muscle load, then the wearer's effort is reduced, but the system becomes less responsive to motion speed changes and motion stops
Solution Approach 1:
The system dynamically changes the parameters of assistive torque (magnitude, direction, timing) based on detected motion state and intended motion. By adjusting these parameters in real-time according to joint angles and angular velocities, the system maintains high responsiveness to motion speed changes and stops while providing sufficient torque to reduce muscle load.
Data Source
AI summary
There are provided a wearable robot and a method of controlling the same. The method includes obtaining a joint angle and a joint angular velocity of a plurality of joints, calculating a target joint angle of one joint among the plurality of joints using a joint angle and a joint angular velocity of at least one joint among the other joints, calculating assistive torque to be applied to the one joint using the calculated target joint angle, and outputting the calculated assistive torque to the one joint.