Four-Bar Linkage Deflection Estimation for Robot Positioning
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Solution Overview
Problem
Conventional control systems for industrial robots with low stiffness struggle to accurately position components due to deflections and vibrations caused by increased speed and weight reduction, particularly in four-bar linkage structures, making it difficult to estimate deflection amounts accurately.
Innovation Solution
A deflection amount estimating device that calculates the swing angle, load, and stiffness value of a four-bar linkage structure using a stiffness-value determining function, allowing for the estimation of deflection amounts based on a stiffness matrix, thereby reducing calculation complexity and improving operation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the speed of industrial robots is increased and weight of links is reduced, then productivity is improved, but deflections and vibrations occur which worsen positioning precision
Solution Approach 1:
The system performs preliminary calculation of deflection amounts based on measured swing angles and predetermined stiffness characteristics before executing positioning operations. This allows the control system to compensate for anticipated deflections in advance, maintaining positioning accuracy despite high-speed operation and weight reduction
Solution Approach 2:
The system uses feedback from swing angle sensors to continuously monitor the state of the four-bar linkage structure. This feedback is fed into the deflection calculation unit to dynamically adjust positioning commands, enabling real-time compensation for deflections and vibrations that occur during high-speed operation
2Reliability
If a four-bar linkage structure is used to achieve stable operation under high-load condition, then reliability is improved, but the structure becomes complicated making deflection estimation difficult
Solution Approach 1:
The system extracts and isolates the swing angle of the four-bar linkage structure as a specific measurable parameter. By focusing on this single key parameter rather than attempting to model the entire complex linkage system, the deflection calculation becomes tractable while still capturing the essential mechanical behavior for compensation purposes
Solution Approach 2:
The system transforms the complex structural problem into a parameter-based calculation by using predetermined stiffness values and swing angle measurements. This parameter transformation approach simplifies the estimation process while maintaining accuracy for the high-load stable operation characteristics of the four-bar linkage
3Device complexity
If conventional control methods are used without considering deflection, then device complexity is kept low, but positioning accuracy deteriorates due to unaccounted deflections
Solution Approach 1:
The system introduces a deflection calculation unit as an intermediary component between the swing angle measurement and the positioning control. This intermediary processes the mechanical state information and generates compensation commands, bridging the gap between simple measurement and accurate positioning without requiring a fully complex control system
Data Source
AI summary
A deflection amount estimating device is provided for estimating an amount of deflection of a four-bar linkage structure part of a robotic arm. The four-bar linkage structure part swings in a given angle range. The deflection amount estimating device comprises processing circuitry configured to calculate a swing angle of the four-bar linkage structure part; calculate a load received by the four-bar linkage structure part, determine a stiffness value, corresponding to the swing angle of the four-bar linkage structure part, based on a stiffness-value determining function indicating a correlation between the stiffness value and the swing angle of the four-bar linkage structure part, the stiffness value indicating a value of each element in a stiffness matrix associating the load with the amount of deflection of the four-bar linkage structure part; and calculate the amount of deflection of the four-bar linkage structure part based on the load and the stiffness matrix.