Numerical Controller Master-Slave Axis Synchronization Failure
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Solution Overview
Problem
In press machine systems, synchronous control between master and slave axes is disrupted when a slave axis encounters obstacles or fails, leading to asynchronous states and potential interference, which existing technologies, such as those described in Japanese Patent No. 3720825, cannot effectively manage.
Innovation Solution
A numerical controller with a position table defining the positional relationship between master and slave axes, a slave axis synchronous control unit, a parent determining unit, and a master axis control unit that determines a stopped or failed slave axis as the parent to maintain synchronization, allowing the master axis to follow the slave axis, thereby preventing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the slave axis is immediately stopped or moved in a retracting direction to avoid obstacles, then collision with obstacles is prevented, but the synchronous control between master axis and slave axis is disrupted and interference may occur
Solution Approach 1:
The patent inverts the traditional master-slave control relationship by making the slave axis (that encountered an obstacle) the parent axis, and the master axis becomes the child axis that follows the slave axis. This inversion allows the system to maintain synchronous control while avoiding obstacles, as the master axis now adapts to the slave axis's position rather than the slave axis adapting to the master axis.
Solution Approach 2:
The patent dynamically changes the parent-child relationship between axes based on operational conditions. When a slave axis encounters an obstacle, the system dynamically reassigns the slave axis as the parent, allowing flexible adaptation to different operational states while maintaining synchronous control throughout the process.
2Reliability
If excitation of the servo motor driving the slave axis is turned off to stop the uncontrollable slave axis, then the slave axis can be stopped due to inertia, but synchronous control cannot be performed and interference may occur
Solution Approach 1:
When the slave axis becomes uncontrollable due to servo motor excitation failure, the patent inverts the control relationship by designating the failed slave axis as the parent axis. The master axis then follows the slave axis's position, maintaining synchronous control even though the slave axis cannot be actively controlled. This prevents interference because the master axis adapts to the slave axis's inertial movement rather than continuing to drive the slave axis.
Solution Approach 2:
The failed slave axis effectively serves itself as the reference for synchronous control. By making the uncontrollable slave axis the parent, the system allows the slave axis's inertial movement to define the synchronous reference, eliminating the need for active control of the failed axis while maintaining system-wide synchronization.
3Reliability
If axes other than the uncontrollable slave axis are stopped without turning off excitation, then the uncontrollable slave axis can be stopped, but the axes are placed in an asynchronous state and interference may occur
Solution Approach 1:
The patent inverts the control hierarchy to maintain synchronous state after failure. By making the failed slave axis the parent and the other axes children that follow the parent, the system ensures all axes remain synchronized even though one axis cannot be actively controlled. This prevents asynchronous states and potential interference.
Solution Approach 2:
The system uses feedback from the failed slave axis's position (even though it can no longer be actively controlled) to guide the movement of the master and other slave axes. The parent determining unit continuously monitors which axis should be the parent, and the control units adjust other axes to follow the parent's position, maintaining synchronous control through feedback.
Data Source
AI summary
A numerical controller contains a position table where a positional relationship is defined between a position of a master axis and positions of a plurality of slave axes, a slave axis synchronous control unit that drives and controls the plurality of slave axes in accordance with the position table so that the slave axes are synchronized with the master axis, a parent determining unit that determines one slave axis, which is stopped due to a failure, to be a parent of the master axis, and a master axis control unit that drives and controls the master axis based on a command position, and if a slave axis serving as the parent of the master axis is determined by the parent determining unit, drives and controls the master axis in accordance with the position table, so that the master axis is synchronized with the slave axis determined to be the parent.