Multi-Axis Servo Command Timing for Trajectory Alignment

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Solution Overview

Problem

The calculation of compensation torque based on servo delay time for each axis and the reference time is complex, leading to trajectory misalignment due to deviations in response delay times among multiple servomotors.

Innovation Solution

A control device that sets a standard servomotor with the maximum response delay time and adjusts the command timing for other servomotors by the difference in response delay times, calculating response delay times as the inverse of position loop gains to align command issuance and suppress trajectory misalignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If compensation torque is calculated based on servo delay time for each axis and reference time, then trajectory alignment is improved, but control complexity increases

Engineering Contradiction:
Improvetrajectory alignmentVSAvoidcontrol complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent extracts and addresses only the dominant factor causing trajectory misalignment (servo delay time differences) while ignoring less significant factors. By focusing solely on timing synchronization rather than calculating complex compensation torques, the solution achieves trajectory alignment with simpler control logic.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the control parameter from compensation torque (complex calculation requiring multiple parameters) to command timing delay (simple time offset). By adjusting when commands are issued to each servo driver rather than how much torque is applied, the system achieves the same trajectory alignment effect with reduced complexity.

Inventive Principle:
Principle #35Parameter changes

2Manufacturing precision

If command timing is delayed for servomotors with shorter response delay times, then trajectory misalignment is suppressed, but control response time increases

Engineering Contradiction:
Improvetrajectory accuracyVSAvoidcontrol response time
Core Design Contradiction:
Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent applies preliminary timing adjustment by delaying command issuance to servomotors with faster response characteristics. This preliminary synchronization ensures all servomotors reach their target positions simultaneously, suppressing trajectory misalignment while maintaining overall system responsiveness.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP3385813B1Control device, control method, control program and recording medium
Publication Date: 2024.11.27 OMRON CORP
  • EP3385813B1 patent drawingFigure 1
  • EP3385813B1 patent drawingFigure 2
  • EP3385813B1 patent drawingFigure 3a~3b

AI summary

The objective of the present invention is to provide a control device capable of suppressing trajectory misalignment due to deviation between the response delay times of a plurality of axes (a plurality of servomotors). In this control device, which issues commands to a plurality of servo drivers corresponding to a plurality of servomotors, the servo driver corresponding to a standard servomotor for which the response delay time is the greatest among the plurality of servomotors is set as a standard servo driver, and the command timing for the other servo drivers is delayed more than the command timing for the standard servo driver, by an amount equal to the difference between the response delay time of the standard servomotor and the response delay time of the servomotors corresponding to the other servo drivers.