Motor Control Device Holding Torque for Gravity Shaft Stability

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Solution Overview

Problem

Conventional motor control devices fail to provide an appropriate holding torque when a motor stops suddenly or is stopped by a collision, leading to potential bouncing or falling of the gravity shaft upon power resumption, risking collisions with peripheral devices or workers.

Innovation Solution

The motor control device incorporates a PI controller with a selection unit that calculates and sets a holding torque based on gravitational torque and collision sensitivity, distinguishing between sudden stops and collisions to adjust the torque command, thereby preventing the gravity shaft from bouncing or falling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If the motor stops suddenly or is stopped by a collision, then the stopping time is reduced, but the holding torque becomes inappropriate causing the gravity shaft to bounce or fall

Engineering Contradiction:

Improvestopping timeVSAvoidholding torque accuracy

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The control device performs preliminary action by storing the torque command value at the moment of brake activation. When the brake is released, this pre-stored value is immediately applied as holding torque, ensuring the gravity shaft remains stable without bouncing or falling, thus resolving the contradiction between fast stopping and reliable holding.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the brake is released quickly to resume operation, then the productivity is improved, but the gravity shaft may fall or bounce causing safety issues

Engineering Contradiction:

Improveoperation resumption speedVSAvoidgravity shaft bouncing or falling

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The torque command value is stored in advance during brake activation. Upon brake release, this pre-prepared torque value is immediately applied, allowing quick resumption of operation while simultaneously preventing the gravity shaft from bouncing or falling, thus resolving the contradiction between productivity and safety.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the holding torque is increased to prevent gravity shaft falling, then the reliability is improved, but the energy consumption increases

Engineering Contradiction:

Improvegravity shaft stabilityVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The control device dynamically adjusts the holding torque parameter based on the stored torque command value from the brake activation moment. This optimized parameter setting provides just enough torque to prevent gravity shaft bouncing or falling, avoiding excessive energy consumption while maintaining reliability.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3439168B1Motor control device

Publication Date: 2022.02.23 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

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AI summary

A disclosed motor control device includes: a PI controller which controls a velocity of a motor; an input unit which receives specification information including information of a weight and a center of mass of a tool; a calculation unit which calculates a gravitational torque based on the specification information; a storage which stores the gravitational torque output from the calculation unit and an integral value output from the PI controller, and outputs the gravitational torque and the integral value in response to a break signal; and a selection unit which sets, to the PI controller, the integral value output from the storage, according to a collision sensitivity input from the input unit.