Chuck-Mounted Sensing for Precise Robot Workpiece Centering
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Solution Overview
Problem
Conventional robot arms face challenges in achieving precise positioning relative to the chuck of a machine tool for automatic workpiece changes, often resulting in collisions or inaccurate insertion due to elasticities and positioning inaccuracies, especially in designs with limited space.
Innovation Solution
An arrangement comprising a machine tool with a rotatable chuck, a measuring device with two sensor units, and a robot arm with a gripping device, where the measuring device is attached to the chuck to rotate with it, allowing the sensor units to measure distances from the chuck axis and transmit signals for precise positioning of the workpiece, enabling the robot arm to adjust the gripping device to align the workpiece axis with the chuck axis within a predetermined tolerance range in multiple rotational positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the robot arm is adjusted in a position relative to the coordinate system of the machine tool, then the positioning accuracy at that specific position is improved, but the positioning accuracy in other positions within the working area deteriorates due to elasticities and joint inaccuracies
Solution Approach 1:
The system performs preliminary measurement and adjustment of the robot arm at multiple predetermined positions within the working area before actual operation. By pre-characterizing the positioning deviations at these positions and storing correction data, the system compensates for elasticities and joint inaccuracies during subsequent workpiece insertion operations, ensuring reliable positioning across the entire working area rather than just at a single adjusted position
Solution Approach 2:
The system uses measurement devices to detect actual positioning deviations of the robot arm at multiple positions and feeds this information back to the control unit. The control unit then calculates and applies correction values to compensate for these deviations, creating a closed-loop system that continuously improves positioning accuracy across the working area based on actual measured performance
2Manufacturing precision
If the robot arm positioning is adjusted for precision, then accurate workpiece insertion is achieved, but the complexity of the adjustment system increases
Solution Approach 1:
The system enables the robot arm to self-adjust and self-calibrate by using its own measurement devices to detect positioning deviations and automatically calculate correction values. The control unit processes the measurement data and applies corrections without requiring external intervention or complex manual adjustment mechanisms, allowing the system to achieve high insertion accuracy through automated self-correction rather than complex mechanical adjustment systems
Solution Approach 2:
The system replaces complex mechanical adjustment mechanisms with a software-based correction approach. Instead of using intricate mechanical devices to physically adjust the robot arm positioning, the system uses measurement data to calculate virtual correction values that are applied in the control software, substituting mechanical complexity with computational simplicity while achieving the same positioning accuracy
Data Source
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AI summary
The invention relates to an assembly (15) having a machine tool (16) with a chuck (17), a measuring device (36), a robot arm (31), and a controller (30). The chuck (17) can be rotated about a chuck axis (S). The robot arm (31) supports a gripping device (32) on the free end of the robot arm in order to receive a workpiece (18). The measuring device (36) has two sensor units (41). An automatic adjustment method can be carried out by means of the controller (30). The robot arm (31) is first actuated so as to receive a workpiece (18), and the workpiece (18) is then positioned in the region of the measurement points (M1, M2) of the sensor units (41) on the basis of the measurement signals (S1, S2) such that a deviation in the inclination and the offset between the workpiece axis (W) and the chuck axis (S) lies within a specified tolerance range. The process is carried out at least in two different rotational positions (A, B) and is optionally iteratively repeated.