Motor Controller Torque Estimation for Smooth Mode Transition

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Solution Overview

Problem

Existing motor control methods experience significant speed variations and changeover shocks when transitioning from synchronous operation mode to position feedback operation mode, particularly due to inadequate load torque estimation and voltage determination, leading to peak current issues and instability in permanent magnet motor control.

Innovation Solution

A motor controller that includes current regulators, a voltage command generator, and a power conversion circuit, where the controller estimates torque proportionate values and sets control constants based on these estimates to smoothly transition between operation modes, using a dc-qc control rotation coordinate system for position sensor-less control and automatic speed regulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If synchronous operation mode is used without position feedback, then the control system can operate without magnetic pole position sensors, but large speed variations and changeover shocks occur when transitioning to position feedback operation mode

Engineering Contradiction:

Improveelimination of magnetic pole position sensorVSAvoidspeed stability during mode transition

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The controller performs preliminary torque estimation during synchronous operation mode before mode transition. By estimating the torque value in advance and using it to set appropriate control constants for the automatic speed regulator, the system prepares for smooth transition to position feedback operation mode, preventing large speed variations and changeover shocks

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback by estimating torque during synchronous operation and using this estimated value to adjust control parameters. The torque estimation serves as a feedback mechanism that enables the controller to adapt control constants before transitioning to position feedback mode, ensuring stable speed control during mode changeover

Inventive Principle:

Principle #23Feedback

2Ease of operation

If conventional voltage determination method is used based on current change, then the control system can operate in synchronous mode, but peak current occurs during mode changeover

Engineering Contradiction:

Improvesynchronous operation capabilityVSAvoidpeak current during transition

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The controller estimates torque during synchronous operation mode before mode transition and uses this preliminary torque value to determine appropriate voltage and current control parameters. This preliminary action prevents peak current during transition by preparing the control system with accurate torque information in advance

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses torque estimation as a feedback mechanism during synchronous operation to continuously monitor load conditions. This feedback enables the controller to adjust voltage commands appropriately before and during mode transition, preventing harmful peak current

Inventive Principle:

Principle #23Feedback

3Loss of time

If mode changeover is conducted based on phase difference range, then the transition timing can be determined, but large speed variation occurs after changeover

Engineering Contradiction:

Improvetransition timing determinationVSAvoidspeed variation after changeover

Core Design Contradiction:

Loss of timeVSSpeed

Solution Approach 1:

The system implements torque estimation feedback during synchronous operation mode to monitor actual load conditions. By comparing the estimated torque with control requirements, the system determines the optimal transition timing that minimizes speed variation, rather than relying solely on fixed phase difference thresholds

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The controller dynamically adjusts the transition timing based on real-time torque estimation feedback. Instead of using a fixed phase difference range, the system adapts the transition point according to the estimated torque conditions, enabling smooth mode changeover with minimal speed variation

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS7619385B2Motor controller, washing machine, air conditioner and electric oil pump

Publication Date: 2009.11.17 HITACHI IND EQUIP SYST CO LTD

AI summary

A motor controller capable of suppressing a large speed change generated at the time of changeover from a synchronous operation mode to a position feedback operation mode and implementing even acceleration characteristics regardless of the load torque by estimating a torque of a permanent magnet motor in the synchronous operation mode for driving the permanent magnet motor and setting an initial value of a current command value in a position sensor-less operation mode on the basis of information of the torque estimated value.