Robot Torque Sensor Load Weight and Center of Gravity Estimation
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Solution Overview
Problem
Conventional methods for estimating the weight and position of a load attached to a robot arm face challenges due to the difficulty in identifying frictional forces, which leads to errors, and require pre-measurement of the load's properties that may not be easily obtainable.
Innovation Solution
A device and method utilizing a torque sensor to detect torques at different positions and postures of a load attached to a robot, allowing for the calculation of the load's weight and gravity center position without needing to identify frictional forces, by using equations that relate torques, positions, and postures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If motor current is used to calculate load weight, then weight estimation can be performed, but frictional force identification becomes necessary and error-prone
Solution Approach 1:
The invention extracts the frictional force component from the torque measurement by using a torque sensor that measures torque independently of friction. The torque sensor is installed on the robot arm's rotation axis to directly measure the torque applied to the load, separating this measurement from the motor current-based method that requires friction identification.
Solution Approach 2:
A torque sensor serves as an intermediary device between the motor and the load, providing direct torque measurement without requiring friction force identification. This intermediary device enables accurate weight estimation by measuring torque directly rather than calculating it from motor current.
2Loss of information
If pre-measurement of load properties is performed, then weight and gravity center information can be obtained, but measurement equipment and time are required
Solution Approach 1:
The robot system performs self-measurement of load properties by using its own torque sensor and control system. The load's weight and gravity center position are measured automatically during robot operation through multi-position torque measurements, eliminating the need for external measurement equipment and pre-measurement processes.
Solution Approach 2:
The invention performs preliminary torque measurements at multiple robot arm positions to calculate load properties before actual operation begins. By measuring torque at different positions and using mathematical calculations, the system obtains load weight and gravity center information in advance, ready for precise control operations.
3Ease of manufacture
If manual input of load information is used, then measurement equipment is avoided, but operator intervention and potential input errors occur
Solution Approach 1:
The system uses feedback from torque sensor measurements to automatically determine load properties. By measuring torque at multiple robot arm positions and using these measurements to calculate load weight and gravity center position, the system eliminates manual input and ensures accurate load information for precise control.
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 precise estimation of the load's weight and gravity center position with high accuracy while the load is attached to the robot, improving control accuracy without requiring pre-measurement or friction identification.
Implementation Method 1
a torque sensor configured to detect a torque applied to an axis for driving a movable part of a robot
Data Source
AI summary
A device, a method and a program, by which a weight and/or a position of a gravity center of a load attached to a movable part of a robot can be estimated by a simple configuration. The device has a torque sensor configured to detect a torque applied to an axis for driving the movable part of the robot, and a calculation section configured to calculate the weight of the article, by using: a first torque applied to the axis, when the article attached to the movable part is positioned at a first position and represents a first posture; a second torque applied to the axis, when the article attached to the movable part is positioned at a second position different from the first position and represents the first posture; the first position; and the second position.