Servo Control Device Coarse Fine Movement Inertia Compensation

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Solution Overview

Problem

Conventional servo control systems for machines like laser beam machines and machine tools face issues with response delays and inertia forces, leading to errors in position control, especially at high speeds, due to the combination of coarse-movement and fine-movement servo responses.

Innovation Solution

A servo control device with a coarse-movement shaft motor and a fine-movement shaft motor, utilizing reference model units for filter computations to calculate and control positions, allowing for independent response settings and minimizing inertia forces by using parameter changing units to adjust response time constants based on command changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a plurality of actuators (coarse-movement actuator and fine-movement actuator) are used to control motion in one direction, then high-speed response is improved, but response delay occurs in the servo system with respect to each command

Engineering Contradiction:

Improveresponse speedVSAvoidresponse delay

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The patent applies preliminary action by calculating model positions (coarse-movement model position and integrated model position) in advance through filter computations before actual movement commands are executed. This allows the servo system to anticipate required positions and reduce response delay when commands are issued, as the control system is already prepared with predicted position data.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements dynamics by making the response time constants of the filter computations adjustable and changeable based on operating conditions. The parameter changing unit dynamically modifies the response time constants to optimize the balance between response speed and accuracy, allowing the system to adapt to different speed requirements and load conditions in real-time.

Inventive Principle:

Principle #15Dynamics

2Stability of the object's composition

If feedback control system is used to determine coarse-movement position response, then stability is ensured, but high-speed response causes the control system to be unstable

Engineering Contradiction:

Improvecontrol system stabilityVSAvoidresponse speed

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

The patent introduces model position calculations as an intermediary between the command input and the actual servo response. Instead of directly controlling the servo motor based on feedback, the system first computes a model position through filter computations, which then serves as the reference for the follow-up control. This intermediary layer smooths the control signal and prevents direct high-speed commands from causing instability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies parameter changes by adjusting the response time constants of the filter computations based on operating conditions. The parameter changing unit modifies these time constants to optimize the balance between stability and response speed, allowing the system to maintain stability at high speeds by adapting the filter characteristics to the current operating state.

Inventive Principle:

Principle #35Parameter changes

3Speed

If coarse-movement shaft performs acceleration and deceleration, then high-speed operation is achieved, but inertia force is generated in fine movement shaft causing error in response

Engineering Contradiction:

Improveoperation speedVSAvoidposition accuracy

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The patent extracts and separately handles the inertia force effect by calculating it as a distinct disturbance component. The inertia force generated by coarse-movement shaft acceleration and deceleration is computed separately and then compensated for in the fine-movement shaft control, preventing this force from causing position errors in the fine movement.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies preliminary anti-action by calculating and compensating for inertia forces before they cause errors in the fine-movement shaft. The control system predicts the inertia force generated by coarse-movement acceleration and deceleration and applies a compensating torque to the fine-movement shaft in advance, preventing position errors before they occur.

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS10061277B2Servo control device with coarse and fine movement

Publication Date: 2018.08.28 MITSUBISHI ELECTRIC CORP

AI summary

A servo control device includes a coarse-movement reference model unit calculating a coarse-movement model position by performing predetermined filter computation based on a position command; a coarse-movement follow-up control unit controlling the coarse-movement shaft motor such that a coarse-movement-shaft motor position follows the coarse-movement model position based on the coarse-movement-shaft motor position provided from the coarse-movement shaft motor and the coarse-movement model position; an integrated reference model unit calculating an integrated model position by performing predetermined filter computation based on a position command; and a fine-movement follow-up control unit controlling the fine-movement shaft motor such that a fine-movement-shaft motor position follows a fine-movement model position based on the fine-movement-shaft motor position provided from the fine-movement shaft motor and the fine-movement model position obtained from the integrated model position and the coarse-movement model position.