Robot Hand Force Feedback for Precise Workpiece Chuck Alignment
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Solution Overview
Problem
Existing robot systems face issues with workpiece alignment and force management during supply to machine tools, leading to potential damage and reduced machining precision due to misalignment, excessive force, and gaps, which conventional correction methods fail to adequately address.
Innovation Solution
A robot system equipped with a force sensor to detect and correct the position and posture of the workpiece gripping mechanism based on external force components, using feedback control to minimize misalignment and excessive force, thereby ensuring precise alignment and contact with the chuck mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the robot device moves to a previously taught position in a previously taught posture to supply the workpiece, then the workpiece can be supplied to the chuck mechanism, but misalignment between the workpiece center line and chuck center line causes excessive external force that may damage the robot link, rotary joint, or chuck mechanism
Solution Approach 1:
The robot control device detects external force components acting on the workpiece gripping mechanism during workpiece supply, and based on this feedback, corrects the position and posture of the gripping mechanism to minimize misalignment and external force, thereby preventing damage to robot components and chuck mechanism
Solution Approach 2:
The system dynamically adjusts the position and posture of the workpiece gripping mechanism based on real-time external force detection, transitioning from fixed taught positions to adaptive dynamic positioning that responds to actual workpiece variations and alignment requirements
2Productivity
If the robot device supplies the workpiece in a previously taught posture, then the workpiece can be positioned at the chuck, but tolerance in the workpiece outer shape causes gaps between the chuck surface and workpiece, leading to vibration during machining and preventing high-precision machining
Solution Approach 1:
The system detects external force components that indicate gaps between the workpiece and chuck surface, and uses this feedback to correct the position and posture of the workpiece gripping mechanism, ensuring complete contact between the workpiece and chuck surface for high-precision machining
Solution Approach 2:
The robot control device performs position and posture correction of the workpiece gripping mechanism before the workpiece is fully supplied to the chuck, preliminarily adjusting alignment based on detected external force components to prevent gaps from forming during the supply process
3Measurement precision
If camera-based correction is used to adjust the workpiece posture, then some alignment can be achieved, but the center line of the chuck and workpiece still do not coincide when the workpiece is not a perfect circle, and the distance from gripping position to butt surface and inclination cannot be accurately detected
Solution Approach 1:
The system replaces camera-based optical measurement with force sensor-based mechanical detection, using external force component detection to accurately determine workpiece position, posture, gripping position distance, and inclination, providing more reliable alignment data for correction
Solution Approach 2:
The robot control device acts as an intermediary that processes external force component data from the force sensor and translates it into position and posture correction commands, mediating between the detected force components and the mechanical adjustment of the workpiece gripping mechanism
4Reliability
If motor current monitoring is used to detect external force and correct robot posture, then some error correction is possible, but the detected current value includes errors making it difficult to completely minimize force between hand and chuck, and the workpiece can be held only in a fixed posture
Solution Approach 1:
The system replaces motor current monitoring with direct force component detection using a force sensor attached to the workpiece gripping mechanism, providing accurate real-time external force data without the errors inherent in current-based indirect measurement
Solution Approach 2:
The system changes the detection parameter from motor current (indirect measure) to external force components (direct measure), enabling accurate detection of force magnitude and direction to completely minimize force between the hand and chuck during workpiece supply
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 system reduces cycle time, minimizes wear and tear, and enhances machining accuracy by accurately aligning workpieces with the chuck surface, reducing external forces, and minimizing gaps, thus improving the efficiency and durability of the robot and machine tool components.
Implementation Method 1
a force sensor for detecting an external force applied to the workpiece gripping mechanism
Data Source
AI summary
A robot system includes a robot device for supplying a workpiece to a machine tool, a hand attached to a distal end of an arm of the robot device, a force sensor for detecting an external force applied to the hand, and a robot control device for controlling the robot device. The robot control device includes an operation control unit for controlling the robot device to correct the position and posture of the hand with respect to the machine tool, based on an output of the force sensor, and a storage unit to store data relating to the corrected position and posture of the hand.