Current Sensor Zero Point Adjustment in Multi-Motor Inverter Systems
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Solution Overview
Problem
In motor driving systems with multiple motors and devices, accurate zero point adjustment of current sensors is hindered by electromagnetic wave noise from other motor driving devices, leading to detection errors and vibration in vehicles.
Innovation Solution
The system determines when each current detector is in a non-energized state and executes zero point adjustment during the stop of switching operations in other motor driving devices, minimizing noise influence by using electromagnetic or magnetic shielding to ensure accurate detection.
Engineering Contradictions & Design Principles
Engineering 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 other motor driving devices causes errors in offset correction
Solution Approach 1:
The system performs zero point adjustment preliminarily when the motor is not operating, before actual motor control begins. This timing ensures that no electromagnetic wave noise from switching operations interferes with the current sensor measurements during the offset correction process
Solution Approach 2:
The control device acts as an intermediary that coordinates between multiple motor driving devices. It determines when each device is in a non-operating state and schedules zero point adjustment only when all other devices are also non-operating, thereby eliminating noise interference from other devices
2Productivity
If multiple motor driving devices operate simultaneously to improve productivity, then system output is improved, but noise from other devices causes errors in offset correction
Solution Approach 1:
The control system segments the zero point adjustment process for each motor driving device independently. It determines the non-operating state of each device separately and performs offset correction for each device only when that specific device and all other devices are in non-operating states, allowing coordinated operation while maintaining measurement accuracy
3Ease of operation
If zero point adjustment is performed during motor operation to maintain continuous control, then ease of operation is improved, but detection accuracy deteriorates due to noise interference
Solution Approach 1:
The system performs zero point adjustment preliminarily before motor operation begins or during idle periods when the motor is not running. This preliminary offset correction ensures accurate current detection for subsequent motor control without requiring interruption of control functionality
Solution Approach 2:
The control device continuously monitors the operating states of all motor driving devices and uses this feedback information to determine appropriate timing for zero point adjustment. The system adjusts offset values based on real-time noise environment assessment, ensuring high accuracy while maintaining continuous operational readiness
Data Source
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AI summary
A plurality of current sensors (41, 42, 51, 52, 61, 62) are provided to correspond to a plurality of inverter circuits (40, 50, 60) for driving a plurality of motor generators (MG1, MG2, MGR), 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 (105). 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.