Numerical Controller Mode Switching with Compensation Pulses

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Solution Overview

Problem

The existing numerical controllers require significant time for deceleration and stopping the spindle motor when switching from speed control mode to position control mode, which increases machining cycle time and reduces productivity.

Innovation Solution

A numerical controller with a control mode switching function that maintains the spindle motor's rotational speed during mode switching from speed control to position control, using a position control start reference position and compensation pulses to ensure accurate positioning without deceleration, allowing continuous rotation until a movement command is initiated.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the spindle motor is decelerated and stopped when switching from speed control mode to position control mode, then the reference position return can be executed, but the machining cycle time increases

Engineering Contradiction:

Improvereference position returnVSAvoidmachining cycle time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-calculating and storing the differential value (difference between current spindle position and reference position) before switching to position control mode. This allows the reference position return to be executed simultaneously with mode switching rather than sequentially, eliminating the time loss from deceleration and stopping.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent maintains continuous rotation of the spindle motor during mode switching from speed control to position control. By keeping the motor rotating and using compensation pulses to achieve reference position return, the useful action of spindle rotation continues uninterrupted, thereby reducing machining cycle time while still accomplishing the reference position return.

Inventive Principle:

Principle #20Continuity of useful action

2Measurement precision

If the spindle motor is decelerated and stopped for mode switching, then accurate reference position can be established, but power consumption increases and productivity decreases

Engineering Contradiction:

Improvereference position accuracyVSAvoidmachining productivity

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent maintains continuous spindle rotation during mode switching, eliminating the stopping and restarting cycles that reduce productivity. The reference position accuracy is maintained through compensation pulses that account for the position differential, allowing both continuous operation and precise positioning.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent changes the control parameter from speed control to position control without changing the physical state of the spindle (keeping it rotating). By using compensation pulses to adjust the position command, the system achieves accurate reference position establishment while maintaining the spindle in a continuous rotation state, improving productivity.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the spindle motor is stopped for mode switching, then coordinate system can be established, but the machining cycle time increases

Engineering Contradiction:

Improvecoordinate system establishmentVSAvoidmachining cycle time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent pre-calculates the differential value between current position and reference position before mode switching. This preliminary calculation allows the coordinate system establishment to occur concurrently with the mode switching process rather than requiring a separate stopping phase, thereby reducing machining cycle time.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses compensation pulses as an intermediary mechanism to establish the coordinate system during continuous rotation. The compensation pulses bridge the gap between the current spindle position and the reference position, allowing coordinate system establishment without requiring the spindle to stop.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP2071419B1Numerical controller having control mode switching function

Publication Date: 2012.02.01 FANUC LTD

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AI summary

A pulse distribution unit (3) notifies a mode control/instruction unit (4) of an output start signal Sa that notifies of the start of output of a position command signal. The mode control/instruction unit (4) outputs a mode setting signal, a speed command signal, and a compensation pulse Sc to an axis control unit (5). In a position control mode, the mode control/instruction unit (4) continues outputting the speed command signal to the axis control unit (5) until the mode control/instruction unit (4) receives the output start signal Sa from the pulse distribution unit (3), and stops, up receiving the output start signal Sa, outputting the speed command signal. The compensation pulse Sc is output to the axis control unit (5) to cancel the difference between a spindle position and the position control start reference position of the spindle. The axis control unit (5) adds the compensation pulse Sc to the position command signal of the spindle output from the pulse distribution unit (3) and outputs the result to a servo control unit (6).