Direct Pose Feedback Control for Real-Time Tool Pose Compensation
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Solution Overview
Problem
CNC machine tools and industrial robots face positioning errors due to geometric and thermal issues, which current compensation methods fail to fully address, especially in real-time applications.
Innovation Solution
A direct pose feedback control method and system that uses a pose measuring mechanism with working and reference double ballbars to calculate and compensate for tool pose errors, integrating thermal error compensation and position feedback control to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If geometric error compensation through PDGE and PIGE is used, then positioning accuracy is improved, but thermal errors cause the compensation to be insufficient
Solution Approach 1:
The patent implements real-time feedback control by continuously measuring the actual pose of the tool platform using a pose measuring mechanism (PMR) and comparing it with the target pose. The controller calculates pose errors and generates compensation driving values to correct these errors dynamically, ensuring accurate compensation despite thermal variations.
Solution Approach 2:
The patent performs preliminary calibration by establishing coordinate transformations between different coordinate systems (tool platform coordinate system, base platform coordinate system, reference coordinate system) before actual operation. This preliminary setup enables real-time pose calculation and compensation during machining operations.
2Manufacturing precision
If real-time pose measurement and compensation is implemented, then positioning accuracy is improved, but control system complexity increases
Solution Approach 1:
The patent uses a universal coordinate transformation framework that can handle multiple coordinate systems (tool platform, base platform, reference) and various error types (geometric, thermal, pose errors) through a unified mathematical model. This multi-functional approach simplifies the control architecture despite the complexity of real-time compensation.
Solution Approach 2:
The patent introduces a pose measuring mechanism (PMR) as an intermediary device that bridges the gap between the tool platform and base platform. This mediator provides real-time pose information without requiring direct complex measurements between all components, simplifying the overall measurement and control system.
3Manufacturing precision
If thermal error compensation is added to position feedback control, then positioning accuracy is improved, but response time may be affected
Solution Approach 1:
The patent implements continuous real-time pose measurement and compensation by continuously reading displacement values from the PMR, calculating actual pose and errors, and generating compensation driving values without interruption. This continuous action ensures both high accuracy and responsive time compensation without periodic delays.
Data Source
AI summary
A direct pose feedback (DPF) control method applied to a DPF controlled machine is provided. The DPF control method includes a pose compensation control in addition to the position feedback control. The pose compensation control includes an initiation step, a reference system step, an actual pose calculation step and a position compensation step. The sum of the primary driving value and the compensation driving value is output to the driver of each of the motors. The advantage of the DPF control method is that the existing real-time position control loop in the controller can remain unchanged, while the pose compensation control is added to eliminate tool pose error resulted from geometric errors in the machine. The DPF controlled machine uses a pose measuring mechanism to measure the actual pose of the tool and to compensate the tool pose error. Hence, the DPF controlled machine is free of geometric errors.