Multi-Motor PWM Carrier Phase Control for Common-Mode Noise

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Solution Overview

Problem

Existing motor control devices experience increased noise due to overlapping switching timings and synchronization of carrier signals between axes, leading to noise generation and magnetic saturation in noise filters.

Innovation Solution

A motor control device that determines phases of carrier signals to ensure the sum of noise vectors is zero, avoiding overlapping switching timings and incorporating a noise filter to suppress common mode noise and reduce heat generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If carrier signals are synchronized at the same phase between axes, then switching operation coordination is improved, but noise increases due to overlapping switching timings

Engineering Contradiction:

Improvecarrier signal synchronizationVSAvoidnoise

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The patent applies asymmetry by intentionally introducing phase differences between carrier signals of different axes. Instead of symmetric synchronization at the same phase, the invention sets each axis's carrier signal to a different phase, which asymmetrically distributes switching timings and prevents overlapping, thereby reducing noise while maintaining coordination.

Inventive Principle:

Principle #4Asymmetry

2Productivity

If switching timings are overlapped between axes, then control coordination is improved, but noise generated by switching operation increases

Engineering Contradiction:

Improvecontrol coordination efficiencyVSAvoidnoise

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent utilizes periodic action by employing PWM (Pulse Width Modulation) with periodic carrier signals for each axis. By controlling the phase and frequency of these periodic signals, the invention achieves coordinated control while distributing switching events in time, preventing overlapping and reducing noise generation.

Inventive Principle:

Principle #19Periodic action

3Object-generated harmful factors

If noise filter is added to suppress common mode noise, then noise suppression is improved, but magnetic saturation of the inductor occurs

Engineering Contradiction:

Improvecommon mode noiseVSAvoidinductor magnetic saturation resistance

Core Design Contradiction:

Object-generated harmful factorsVSStrength

Solution Approach 1:

The patent applies beforehand cushioning by proactively preventing noise generation at the source through phase-differentiated carrier signals. This preventive approach cushions against the formation of large common mode noise currents that would otherwise saturate the noise filter inductor, allowing the filter to operate within its linear range and maintain effectiveness.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS12407279B2Motor control device, motor control method, and program

Publication Date: 2025.09.02 OMRON CORP

AI summary

An increase in noise can be suppressed. A motor control device includes N inverters configured to control N motors connected via power cables based on PWM signals, respectively, and a phase controller configured to determine phases of N carrier signals to be used for generating PWM signals to be supplied to the N inverters so that a sum of N vectors represented by noise amounts related to the respective N motors becomes zero.