Robot Arm Payload Estimation Using Distal Joint Inertia Measurement
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Solution Overview
Problem
Existing robot arm systems face challenges in accurately estimating payload inertial parameters due to user input errors, which can lead to incorrect motor gains, shaking during operation, and potential mechanical damage, especially in SCARA systems with multi-joint designs.
Innovation Solution
A method for payload estimation that involves calculating the payload mass and inertial parameters by rotating the most distal joint (fourth joint) of a robot arm, using dynamic equations to measure equivalent moment of inertia and center of mass, simplifying calculations and reducing user input errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If user inputs payload inertial parameters manually through user interface, then the robot arm system can be operated, but user input errors occur leading to incorrect motor gains and shaking during operation
Solution Approach 1:
The robot arm system performs self-measurement of payload inertial parameters by automatically detecting and calculating mass, center of mass, and moment of inertia without requiring manual user input. The system uses its own actuators to rotate joints and measure dynamic responses, then computes the inertial parameters automatically, eliminating human error while maintaining ease of operation.
2Measurement precision
If all joint dynamic equations are involved in payload estimation, then comprehensive parameters can be obtained, but calculation complexity increases
Solution Approach 1:
The patent extracts and uses only the dynamic equation of the most distal joint (fourth joint) for payload estimation, removing the need to solve the complex system of all four joint equations. This extraction approach maintains the ability to obtain complete inertial parameters (mass, center of mass, moment of inertia) while dramatically simplifying the calculation process.
3Reliability
If payload inertial parameters are not accurately estimated, then the robot arm system may operate, but the risk of mechanical damage increases and performance level cannot be achieved
Solution Approach 1:
The system performs preliminary measurement and estimation of payload inertial parameters before actual operation begins. By measuring the equivalent moment of inertia through joint rotation and calculating all inertial parameters in advance, the system ensures accurate motor gain settings are established beforehand, preventing mechanical damage and performance degradation during subsequent operations.
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 method accurately estimates payload mass, center of mass, and moment of inertia, ensuring optimal robot arm performance by automating the estimation process and improving calculation accuracy.
Implementation Method 1
rotating merely the fourth joint to drive the spline shaft and payload to rotation, in order to measure the equivalent moment of inertia of the payload associated with the fourth joint
Implementation Method 2
rotating merely the second joint or simultaneously rotating both the first and second joints, to measure the dynamic parameters of the payload associated with the fourth joint
Data Source
AI summary
A method of payload estimation and a robot arm system and an electronic device using the same are disclosed for acquiring inertial parameters of a payload. The method comprises calculating a payload mass, merely rotating a forth joint of the robot arm system to calculate an equivalent moment of inertia of the payload, merely rotating a second joint to measure data for dynamic equations of a fourth joint, repeating at least two times to obtain at least two sets of the dynamic parameters to calculate a center of mass of the payload, and substituting the payload mass, the equivalent moment of inertia and the center of mass into an equation of parallel axis theorem to obtain a moment of inertia of the payload. The center of mass is calculated by solving two dynamic equations associated with the fourth joint, thus the computation complexity of the payload inertial parameters is reduced.