Sensorless Motor Drive Control via Impedance Modeling

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Deep well submersible pump motor systems face challenges in controlling motor speed and torque without feedback sensors, particularly due to long motor cables and complex impedance components, which complicates precise control and efficient operation.

Innovation Solution

A sensorless closed-loop control system is implemented using a configuration tool that determines equivalent impedance values for the motor, filter, and transformer, allowing for user-defined parameters to configure the motor drive, enabling precise speed and torque control through programmable algorithms and inverter switching control signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If feedback sensors are installed at the motor for speed and torque control, then control precision is improved, but device complexity and cost increase

Engineering Contradiction:

Improvespeed and torque control precisionVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system uses the motor drive's own current sensors and voltage measurements to estimate speed and torque through mathematical models, eliminating the need for external feedback sensors. The object model containing impedance parameters enables the drive to self-determine operational state without additional measurement devices.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Physical feedback sensors are replaced with electrical measurement-based estimation using current sensors and voltage measurements combined with mathematical modeling. The mechanical/sensor-based measurement system is substituted with an electrical-field-based estimation system using the object model.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If long motor cables are used in deep well applications, then installation flexibility is improved, but impedance complexity and control difficulty increase

Engineering Contradiction:

Improveinstallation flexibilityVSAvoidimpedance complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The system compensates for cable impedance effects by incorporating cable parameters (resistance, inductance, capacitance) into the object model. The drive adjusts its control parameters based on the modeled cable characteristics, allowing it to maintain control precision despite varying cable lengths and impedances in different installation scenarios.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If sensorless control is implemented, then device complexity is reduced, but measurement precision and control accuracy deteriorate

Engineering Contradiction:

Improvesystem complexityVSAvoidspeed and torque estimation accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The system implements software-based feedback through the object model, which continuously estimates motor state based on measured currents and voltages. The model provides virtual feedback signals that enable closed-loop control without physical sensors, maintaining accuracy through mathematical relationships rather than direct physical measurement.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The object model acts as an intermediary between the motor drive and the motor, providing estimated speed and torque values based on electrical measurements and impedance parameters. This intermediary model translates electrical measurements into mechanical state estimates without requiring direct mechanical sensors.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Measurement precision

If configuration parameters for filter, transformer, and cable are collected, then control accuracy is improved, but ease of operation deteriorates

Engineering Contradiction:

Improvecontrol accuracyVSAvoidconfiguration complexity

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The object model serves multiple functions: it characterizes the motor, filter, transformer, and cable together as a single integrated system. By combining all impedance parameters into one unified model, the system achieves accurate control across different configurations without requiring separate adjustment procedures for each component.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9595896B1Methods and systems for sensorless closed loop motor speed and torque control

Publication Date: 2017.03.14 ROCKWELL AUTOMATION TECH INC

AI summary

Methods and systems are presented for closed loop motor speed and torque control without a sensor at the motor, in which configuration parameters are received from a user interface to define operating characteristics of a filter, a transformer, a cable, and the motor coupled with the output of a motor drive, and an object model of the motor drive is configured according to the filter, transformer, cable and motor configuration parameters to facilitate sensorless closed loop motor speed and/or torque control.