Robot Control Unit Deflection Compensation for Assembly Precision
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Solution Overview
Problem
Existing robot control units for assembly robots face challenges in accurately determining the successful fitting of a first work to a second work due to limitations in force detection and deflection calculations, particularly when dealing with complex shapes or densely arranged machines, which can lead to inaccurate positioning and potential damage.
Innovation Solution
A robot control unit equipped with a force detecting device, storage device for deflection amount tables or calculation formulas, and a controller that calculates deflection amounts and work positions based on detected forces, enabling precise determination of the real fitting amount between the first and second works, even without the use of cameras, by correcting for deflection in the fitting direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a force sensor is used to detect force during fitting operation, then the fitting success can be determined, but the measurement precision is insufficient due to deflection of the robotic arm and workpieces
Solution Approach 1:
The patent replaces direct mechanical force measurement with a computational model that calculates deflection amounts based on detected force values and pre-stored mechanical characteristics (deflection-amount calculation formulas). This substitution eliminates the need for complex high-precision force sensors while achieving accurate fitting detection by compensating for robotic arm and workpiece deflections through mathematical calculations.
Solution Approach 2:
The patent transforms the force detection problem into a deflection calculation problem by changing the measurement parameter. Instead of directly measuring displacement or using complex force-torque sensors, the system detects force and converts it into deflection amount information through pre-calibrated formulas that account for the robotic arm's and workpieces' mechanical characteristics, thereby achieving precise fitting determination.
2Measurement precision
If camera-based detection is used to determine fitting position, then visual feedback is provided, but the device complexity increases and it cannot work in densely arranged manufacturing environments
Solution Approach 1:
The patent extracts the essential measurement function from complex optical systems by using only simple force sensors to detect contact. Instead of employing cameras and complex vision systems, the system isolates the critical information (force at contact point) and uses pre-stored mechanical characteristic data to calculate position and fitting status, thereby eliminating unnecessary device complexity while maintaining detection accuracy.
Solution Approach 2:
The patent creates a virtual model of the robotic arm and workpieces' mechanical characteristics by pre-storing deflection-amount calculation formulas obtained through offline measurements. This virtual copy allows the system to simulate and calculate actual positions and fitting states based on simple force measurements, replacing the need for physical optical measurement systems.
3Productivity
If deflection amounts are not corrected in position calculations, then the calculation process is simplified, but the manufacturing precision of fitting operation deteriorates
Solution Approach 1:
The patent performs preliminary measurements and calculations of the robotic arm's and workpieces' deflection characteristics before actual operation. By pre-storing deflection-amount calculation formulas that incorporate these characteristics, the system can quickly correct position calculations during fitting operations without performing complex real-time measurements, thereby maintaining both high processing speed and high precision.
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 solution enhances the accuracy of determining successful fitting, reduces the risk of damage, and simplifies the operation management of assembly robots, making them applicable to complex shapes and densely arranged manufacturing environments.
Implementation Method 1
a force detecting device configured to detect a force applied to the first work or the second work at the time of fitting
Implementation Method 2
the first-work deflection amount table associating at least magnitude variations of the force applied at the time of fitting with the deflection amounts of the first holding device or the deflection amounts of the first holding device and the first work in the direction of the fitting
Data Source
AI summary
A robot control unit for an assembly robot includes a force detecting device configured to detect forces applied to first and second works and, when the first work is fitted to the second work by a first robotic arm, a storage device stores a deflection amount table associating a force applied when fitting with the deflection amount of the robotic arm in a direction of the fitting, a deflection-amount acquiring process configured to calculate the deflection amount of the robotic arm in the direction of the fitting by using a value detected by the force detecting device and the deflection amount table, a work-position acquiring process configured to calculate a work position as the position of the first work relative to the second work in the direction of the fitting based on operation information about the robotic arm, and a real-fitting-amount acquiring process configured to correct the work position based on the calculated deflection amount.