Current Sensor Zero Point Adjustment in Multi-Motor Inverter Systems

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In motor driving systems with multiple motors and devices, accurate zero point adjustment of current sensors is challenging due to electromagnetic wave noise from switching operations in power converter circuits, leading to detection errors and vibration in vehicles.

Innovation Solution

A motor driving system with a control circuit that determines the non-energized state of each current detector and identifies noise from other motor driving devices, allowing for zero point adjustment only when noise influence is minimal, thereby enhancing detection accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If zero point adjustment is performed continuously to improve detection accuracy, then measurement precision is improved, but electromagnetic wave noise from switching operations causes errors in adjustment

Engineering Contradiction:

Improvecurrent sensor detection accuracyVSAvoidelectromagnetic wave noise influence

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The system performs zero point adjustment in advance during periods when the power converter circuit is not operating (low noise periods). By determining the non-energized state of the power converter circuit before adjustment, the system prepares the accurate zero point value when noise conditions are favorable, rather than attempting adjustment during high-noise operating conditions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control circuit continuously monitors the operating state of the power converter circuit and uses this feedback to determine the appropriate timing for zero point adjustment. By detecting whether the circuit is in an energized or non-energized state, the system dynamically adjusts its measurement strategy based on real-time noise conditions.

Inventive Principle:

Principle #23Feedback

2Area of stationary object

If multiple motor driving devices are disposed close to each other to save space, then device compactness is improved, but noise from other devices causes errors in zero point adjustment

Engineering Contradiction:

Improvelayout spaceVSAvoidnoise from other motor driving devices

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

Before performing zero point adjustment on any current sensor, the control circuit checks whether other motor driving devices are in a non-energized state. This preliminary verification ensures that even in compact layouts where devices are close together, the adjustment occurs only when neighboring devices are not generating electromagnetic noise.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control circuit acts as an intermediary that coordinates between multiple motor driving devices. It monitors the state of all devices and selectively enables zero point adjustment only when the overall system noise environment is acceptable, effectively mediating between the need for compact layout and the need for accurate adjustment.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If zero point adjustment is performed during energized state to maintain continuous operation, then productivity is improved, but detection accuracy deteriorates due to noise

Engineering Contradiction:

Improvecontinuous operation capabilityVSAvoidzero point adjustment accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

Instead of continuous adjustment, the system performs zero point adjustment periodically during brief non-energized intervals. The control circuit identifies these periodic opportunities when the power converter circuit is not switching, and performs adjustment during these windows without requiring continuous interruption of motor operation.

Inventive Principle:

Principle #19Periodic action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables highly accurate zero point adjustment of current sensors, improving motor driving current detection and reducing torque pulsation, leading to enhanced vehicle driving performance.

Implementation Method 1

a current detector provided to correspond to each motor driving device to detect a motor driving current

Methodology Applied

Scientific EffectMagnetic field detection: Magnetic Field

Implementation Method 2

electric power semiconductor elements carry out switching operations at high frequencies, which generates electromagnetic wave noise

Methodology Applied

Scientific EffectElectromagnetic wave noise detection: Electromagnetic Induction

Data Source

PatentUS8115423B2Motor driving system and controlling method of the same

Publication Date: 2012.02.14 DENSO CORP

AI summary

A plurality of current sensors are provided to correspond to a plurality of inverter circuits for driving a plurality of motor generators, respectively. Zero point adjustment of each current sensor is executed in a non-energized state recognized based on a stop of operation of the corresponding inverter circuit and when noise influence is determined to be small based on stops of operations of the other inverter circuits in the same casing. As a result, it is possible to avoid a risk of performing the zero point adjustment in a state in which an output of the current sensor is not exactly a value corresponding to zero current due to the noise influence from the other inverter circuits. In this way, it is possible to highly accurately execute the zero point adjustment of the current sensor for measuring motor driving current.