Numerical Controller Servo Mode Switching for Cycle Time Reduction
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Solution Overview
Problem
Existing numerical controllers face challenges in seamlessly switching from position control to pressure control, leading to inefficiencies such as wasteful time delays and overpressure issues during the transition, which affect the accuracy and speed of control operations in applications like injection molding and press machines.
Innovation Solution
A numerical controller with a servo control unit that compares feedback control commands for position and pressure, automatically switches between control modes based on these comparisons, and terminates the current movement command to initiate the next command immediately after switching, allowing for synchronized operation and precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the numerical controller waits for the current movement command to complete before executing the next command, then the control transition is stable, but the cycle time is extended and productivity is reduced
Solution Approach 1:
The system prepares the next command in advance while the current command is being executed. When a mode switch is detected, the pre-prepared next command is immediately activated without waiting for the current command to complete, thus reducing cycle time while maintaining control stability
Solution Approach 2:
The command execution system dynamically adapts its behavior based on the control mode. In position control mode, commands are executed sequentially for stability. In pressure control mode, the system allows overlapping command execution to reduce cycle time, making the execution strategy flexible and adaptive
2Productivity
If the numerical controller executes the next command immediately after mode switch, then productivity is improved, but control precision deteriorates due to residual movement commands
Solution Approach 1:
The system extracts and separates the position control command from the pressure control command execution flows. When switching from position to pressure control, the position command is cleanly terminated and does not interfere with the pressure control precision, allowing immediate next command execution without precision loss
Solution Approach 2:
A command management intermediary layer is introduced between the controller and servo motor. This intermediary handles the transition by suppressing residual position commands and cleanly activating pressure commands, ensuring precision is maintained during the rapid mode switch
3Measurement precision
If the servo motor continues position control after mode switch, then position accuracy is maintained, but pressure control responsiveness is delayed causing overpressure
Solution Approach 1:
The system issues a preliminary command suppression signal at the moment of mode switch detection. This signal immediately terminates the position control command to the servo motor, preventing the residual command from causing overpressure while the pressure control command is simultaneously activated
Solution Approach 2:
The system applies preliminary anti-action by suppressing the position control command before it can cause harmful effects. The command suppression occurs at the exact moment of mode switch, preventing the residual position command from interfering with pressure control and causing overpressure
Data Source
AI summary
A servomotor in a numerical controller is controlled by automatically switching to either pressure control or position control in association with the command which is smaller from among a command obtained by performing pressure feedback control and a command obtained by performing position feedback control. When switched to pressure control while moving according to a movement command, the output of the movement command is terminated halfway, and the command in the next block is executed, and pressure control of the next command is immediately started. As a result, a wasteful time is eliminated, and a cycle time of the operation can be shortened.