Motor Controller Stopping Strategy Using Segmented Deceleration

Solution Overview

Problem

Existing motor control techniques for stopping a servo motor at a specific position are inefficient, leading to prolonged stopping times and reduced productivity due to inaccuracies in maximum deceleration control operations.

Innovation Solution

A motor controller that calculates and compares two time periods for stopping a rotary shaft: one without changing the rotation direction and another after a temporary halt and counterclockwise rotation, allowing the motor to stop at the target position in the shortest possible time by selecting the optimal control method based on these calculations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If maximum deceleration control operation is carried out by causing maximum current to flow to the motor, then the motor can be stopped at a specific position in a short period of time, but it becomes difficult to stop the motor at the specific position with accuracy

Engineering Contradiction:

Improvestopping timeVSAvoidpositioning accuracy

Core Design Contradiction:

Loss of timeVSManufacturing precision

Solution Approach 1:

The stopping operation is divided into two distinct phases: a first stopping operation using maximum deceleration control for rapid deceleration, and a second stopping operation using feedrate control for precise positioning. This segmentation allows the system to benefit from both fast deceleration and accurate positioning without the drawbacks of using either method alone.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The control method dynamically switches between two different control modes based on the motor's current state and the remaining distance to the target position. The system transitions from maximum deceleration control to feedrate control at an optimal switching point, adapting the control strategy to the real-time requirements of the stopping operation.

Inventive Principle:

Principle #15Dynamics

2Speed

If maximum current is applied to achieve maximum deceleration, then stopping speed is improved, but positioning precision deteriorates

Engineering Contradiction:

Improvedeceleration speedVSAvoidpositioning precision

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The stopping operation is divided into two distinct phases: a first stopping operation using maximum deceleration control for rapid deceleration, and a second stopping operation using feedrate control for precise positioning. This segmentation allows the system to benefit from both fast deceleration and accurate positioning without the drawbacks of using either method alone.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The control method dynamically switches between two different control modes based on the motor's current state and the remaining distance to the target position. The system transitions from maximum deceleration control to feedrate control at an optimal switching point, adapting the control strategy to the real-time requirements of the stopping operation.

Inventive Principle:

Principle #15Dynamics

3Manufacturing precision

If the motor is controlled to stop at a specific position using conventional methods, then positioning is achieved, but the stopping period is prolonged

Engineering Contradiction:

Improvepositioning accuracyVSAvoidstopping period

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The stopping operation is divided into two distinct phases: a first stopping operation using maximum deceleration control for rapid deceleration, and a second stopping operation using feedrate control for precise positioning. This segmentation allows the system to benefit from both fast deceleration and accurate positioning without the drawbacks of using either method alone.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system performs preliminary maximum deceleration control to rapidly reduce the motor speed before transitioning to feedrate control for final positioning. This preliminary action removes the bulk of the motion quickly, allowing the subsequent precision control phase to complete much faster than if precision control were used throughout the entire stopping process.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11404981B2Motor controller

Publication Date: 2022.08.02 FANUC LTD

AI summary

The present disclosure provides a motor controller which can effectively stop a motor at a specific position in a short period of time, and can achieve an orientation operation quickly. A motor controller is configured to stop a rotary shaft, and includes: a first time period calculator that calculates a target stop position and an acceleration at a time of positioning, a first time period that is to be taken by the rotary shaft to stop at the target stop position; a second time period calculation unit that calculates the target stop position and the acceleration at the time of positioning, a second time period that is to be taken by the rotary shaft to stop at the target stop position; a comparison unit that compares the first time period with the second period; and an orientated stop control unit that controls and stops the motor.