Manipulator Compliance Determination Using Actuator Torque
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Solution Overview
Problem
Industrial robots experience deviations from programmed poses due to inaccuracies in link and joint geometries, joint and arm mechanics, force interactions, and compliance, which existing calibration methods are costly and inefficient to address, especially in smaller production facilities.
Innovation Solution
A method and system for determining manipulator properties by clamping a movable part, selecting identification and excitation joint sets, and monitoring actuator torque and joint position to calculate properties such as compliance, allowing for improved control without dismounting components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing calibration methods are used to address deviations in manipulator properties, then manufacturing precision can be improved, but device complexity and cost increase significantly
Solution Approach 1:
The manipulator performs self-calibration by using its own actuators to apply torques and its own sensors to measure resulting positions, eliminating the need for external calibration equipment. The controller coordinates the excitation torques and processes the measurement data to determine compliance properties internally.
Solution Approach 2:
The patent replaces complex mechanical calibration systems with a computational approach using software algorithms that process torque and position data to calculate compliance properties. The calibration function is transferred from hardware to software, reducing mechanical complexity.
2Manufacturing precision
If existing calibration methods are used to address deviations in manipulator properties, then manufacturing precision can be improved, but loss of time increases due to lengthy calibration procedures
Solution Approach 1:
The manipulator determines compliance properties in advance during manufacturing or setup, storing these properties for later use in compensation algorithms. This preliminary determination eliminates the need for time-consuming calibration procedures before each production run or task change.
Solution Approach 2:
The patent uses dynamic excitation torques applied through the actuators to provoke measurable responses in the manipulator structure. By applying varying torques and measuring the resulting position changes, the system efficiently extracts compliance properties through dynamic testing rather than static measurements.
3Measurement precision
If dismounting components is performed to measure manipulator properties, then measurement precision can be improved, but productivity decreases due to assembly/disassembly requirements
Solution Approach 1:
The actuators serve dual functions: they actuate the manipulator joints during normal operation and simultaneously serve as excitation sources for compliance measurement. The sensors likewise serve both normal position feedback and measurement functions, eliminating the need for separate measurement equipment and disassembly procedures.
Solution Approach 2:
The manipulator uses its own built-in actuators and sensors to perform self-diagnosis and self-characterization of compliance properties without requiring external measurement equipment or disassembly of components. The system is inherently self-sufficient for its own characterization.
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
This approach enables accurate determination of manipulator properties, reducing deviations and improving control efficiency, making it a faster and more cost-effective method than existing solutions.
Implementation Method 1
Each joint is configured to be actuated by an actuator such as a motor
Implementation Method 2
indicate compliance of the manipulator... determining the at least one property of the selected axis based on the monitored one or more quantities
Data Source
AI summary
A method and system for determining at least one property associated with a selected axis of a manipulator (2). The elasticity of the links (4, 6, 9, 10, 13, 14) and joints (3, 5, 7, 8, 11, 12) of a manipulator (2) can be modeled and the resulting compliance can be determined. A certain method is used to control the manipulator (2) such that certain quantities related to actuator torque and/or joint position can be determined for a certain kinematic configuration of the manipulator (2). Depending on the complexity of the manipulator (2) and the number of properties that are of interest, the manipulator (2) is controlled to a plurality of different kinematic configurations in which configurations the quantities are determined. Thereafter, a stiffness matrix (K) for each component of the manipulator (2) can be determined, and a global stiffness matrix (MSM) for the total manipulator (2) can be determined in order to determine at least one property of the selected axis.