Multi-joint Robot Single Sensor Torque Repositioning
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Solution Overview
Problem
Existing multi-joint robots require multiple torque sensors to accurately detect forces and torques, leading to increased costs and potential interference with human operators during repositioning, as existing methods like soft-floating servo control and magnetic torque sensors are inefficient in distinguishing between applied forces and frictional influences.
Innovation Solution
A multi-joint robot design utilizing a single sensor with a torque detecting part and a controller that calculates disturbance torques by subtracting mass and motion-generated torques, allowing for repositioning commands to be generated based on threshold exceedances, thereby reducing the need for multiple sensors and improving force detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple torque sensors are arranged on each arm to eliminate friction influence, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges multiple torque detection functions into a single torque sensor by strategically positioning it to detect torques about multiple axes (first and second axes with orthogonal vectors) simultaneously. This consolidation eliminates the need for multiple separate sensors while maintaining measurement precision through the sensor's specific placement and the controller's ability to calculate disturbance torques for each axis.
Solution Approach 2:
The single torque sensor is designed to perform multiple functions by detecting torques about different axes. The sensor serves as a multi-functional device that can measure disturbance torques for both the first and second axes, reducing the overall sensor count while maintaining comprehensive force detection capability.
2Ease of operation
If soft-floating servo control is used to allow easy repositioning, then ease of operation is improved, but measurement precision deteriorates due to frictional influence
Solution Approach 1:
The patent extracts the frictional influence from the torque measurement by calculating and subtracting disturbance torques (which include friction) from the total detected torque. This separation allows the system to maintain soft-floating servo control for ease of repositioning while obtaining accurate force measurements by isolating the external force component from the friction component.
Solution Approach 2:
The controller uses feedback from the torque sensor to calculate disturbance torques and determine external forces. By continuously monitoring the detected torque and comparing it with calculated disturbance torques, the system can accurately determine external forces applied during repositioning operations, maintaining measurement precision even with soft-floating control enabled.
Data Source
AI summary
A multi-joint robot using substantially one sensor, capable of performing a proper repositioning motion of an arm of the robot. The controller has a disturbance torque estimating part which estimates a first disturbance torque and a second disturbance torque, by calculating a torque generated by a mass and motion of the robot and subtracting the calculated torque from the first torque and the second torque detected by a torque detecting part. The controller has a repositioning commanding part which generates a motion command for rotating each axis so that the disturbance torque is reduced, when the disturbance torque exceeds a torque threshold. Since the axis is repositioned based on the motion command, a portion of the robot pushed by the operator is repositioned, whereby the operator can easily perform one's work without using a teaching board, etc.