Motor Torque Ripple Compensation Using Cross-Correlated Feedforward

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Solution Overview

Problem

Existing motor control systems struggle to accurately determine and suppress the magnitude and phase of load torque ripple components in permanent magnet alternating current (PMAC) motors, particularly in applications with non-linear loads, leading to mechanical vibrations and inefficiencies.

Innovation Solution

A motor controller that measures the mechanical angle and rotational speed of the shaft, generates a speed feedback signal, and employs a load torque ripple compensator using a torque feedforward function to dynamically adjust the magnitude and phase of the feedforward compensation signal in real-time, matching the frequency, magnitude, and phase of the load torque ripple to reduce or eliminate it.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a PI controller is used to regulate torque reference value, then speed control stability is improved, but load torque ripple cannot be accurately compensated due to unknown magnitude and phase

Engineering Contradiction:

Improvespeed control stabilityVSAvoidload torque ripple measurement precision

Core Design Contradiction:

Stability of the object's compositionVSMeasurement precision

Solution Approach 1:

The system performs preliminary identification of load torque ripple characteristics (magnitude and phase) before the main control operation. The feedforward compensation signal is pre-calculated based on identified ripple parameters, allowing the PI controller to focus on stability while the feedforward path handles ripple compensation proactively.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

An intermediary feedforward compensation path is introduced between the reference torque and the actual torque application. This intermediary path contains the identified load torque ripple characteristics and generates compensating signals that are added to the PI controller output, enabling precise ripple compensation without disrupting the stability-providing PI control action.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If manual commissioning is performed to determine load torque ripple parameters, then control accuracy is improved, but time consumption and complexity increase

Engineering Contradiction:

Improveload torque ripple parameter accuracyVSAvoidcommissioning time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs self-identification of load torque ripple parameters automatically during operation. The microcontroller automatically determines the magnitude and phase of load torque ripple components without requiring manual intervention, trial-and-error commissioning, or external measurement equipment, thereby eliminating time-consuming manual setup while achieving accurate parameter identification.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Manual mechanical commissioning procedures are replaced with automated digital signal processing. The system uses digital algorithms to identify load torque ripple characteristics from measured signals, substituting manual adjustment and measurement with automated computational methods that are both faster and more precise.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If feedforward compensation signal is added to reduce load torque ripple, then mechanical vibrations are reduced, but control system complexity increases

Engineering Contradiction:

Improvemechanical vibrationsVSAvoidcontrol system complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The system dynamically adjusts the parameters (magnitude and phase) of the feedforward compensation signal based on identified load torque ripple characteristics. By changing these parameters automatically rather than using fixed values, the system effectively reduces mechanical vibrations while keeping the control structure relatively simple and adaptive to different operating conditions.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12381499B2Automated load torque ripple compensation using feedforward signals calculated using a cross-correlation function

Publication Date: 2025.08.05 INFINEON TECH AUSTRIA AG

AI summary

A motor controller includes a measurement interface configured to measure a mechanical angle of a shaft driven by a motor and a rotational speed of the shaft, and generate a speed feedback signal representative of the rotational speed, a speed regulator, and a current regulator. The speed regulator includes an error component configured to generate a speed error signal based on a difference between a speed reference signal and the speed feedback signal; a proportional integral controller configured to, based on the speed error signal, regulate a torque reference value that is configured to sustain a speed reference value; and a load torque ripple compensator configured to apply a torque feedforward function to reduce a load torque ripple in the torque reference value. The current regulator is configured to drive motor currents of the motor for generating a torque corresponding to the torque reference value.