Inverter Controller Speed Followability via Interval-Based Acceleration
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Solution Overview
Problem
In on-vehicle fluid machines, non-periodic transmission of command rotation speed can lead to a difference between actual and commanded rotation speeds, resulting in decreased noise and vibration (NV) characteristics due to poor followability of the motor speed.
Innovation Solution
An inverter controller that counts the command obtaining interval and calculates a target acceleration based on this interval and the new command rotation speed to control the electric motor, ensuring it follows changes in the command rotation speed effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If command rotation speed is transmitted non-periodically from outside, then communication flexibility is improved, but followability of actual rotation speed deteriorates
Solution Approach 1:
The system performs preliminary actions by counting the command obtaining interval and calculating target acceleration in advance based on the time period from when the old command rotation speed was obtained to when the new command rotation speed is obtained. This allows the motor to proactively adjust its acceleration profile before the actual speed deviation occurs, maintaining good followability even with non-periodic command transmission.
Solution Approach 2:
The system implements feedback by continuously monitoring the command obtaining interval and using this information to dynamically adjust the target acceleration calculation. The processing circuitry uses the counted interval as feedback to determine appropriate acceleration rates, ensuring the motor responds appropriately to varying command transmission patterns while maintaining speed followability.
2Loss of energy
If command rotation speed is not obtained at predetermined updating interval, then communication load is reduced, but difference between actual and command rotation speed increases
Solution Approach 1:
The system changes parameters by dynamically adjusting the target acceleration based on the actual command obtaining interval rather than using a fixed predetermined updating interval. This allows the control system to adapt to varying communication conditions, maintaining speed control precision even when commands are transmitted less frequently, thereby reducing communication load while preserving control accuracy.
3Device complexity
If acceleration is calculated based on predetermined updating interval, then control simplicity is improved, but noise and vibration characteristics deteriorate
Solution Approach 1:
The system applies dynamics by making the acceleration calculation adaptive rather than fixed. The target acceleration is dynamically determined based on the actual command obtaining interval, which varies with communication conditions. This dynamic approach smooths speed transitions and reduces abrupt changes that cause noise and vibration, while the processing circuitry handles the complexity automatically to maintain control simplicity.
Data Source
AI summary
An inverter controller includes a processing circuitry. The processing circuitry is configured to obtain a command rotation speed transmitted repeatedly from outside of the inverter controller, count a command obtaining interval that is a period from a point in time where an old command rotation speed was obtained to a point in time where a new command rotation speed is obtained, set a target acceleration of the electric motor when the command rotation speed has been obtained, and control the inverter circuit such that the electric motor rotates at the set target acceleration. The processing circuitry is configured to calculate a command acceleration based on the counted command obtaining interval and the new command rotation speed, the command acceleration being set as the target acceleration.