Motor Control Device Torque Responsiveness
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Solution Overview
Problem
In motor control devices, the responsiveness of torque is deteriorated due to insufficient rotor flux when the excitation current is limited by a constant maximum allowable current, leading to restricted current flow during transiently large excitation.
Innovation Solution
The solution involves amplifying the base current command value based on the torque command value to compensate for rotor flux response delays, calculating a compensation value for the amplified current command value, and adding it to the post-compensation command value to improve torque responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the excitation current is limited by a constant maximum allowable current to protect the driving circuit, then the driving circuit is protected from excessive current, but the torque responsiveness deteriorates due to insufficient rotor flux when transiently large excitation current is required
Solution Approach 1:
The patent applies dynamics by making the current limit value variable rather than constant. The current limit determination unit dynamically adjusts the current limit value based on the relationship between excitation current and torque current, allowing the system to protect the driving circuit under normal conditions while permitting transiently large excitation current when needed for rapid torque response.
Solution Approach 2:
The patent changes the parameter of current limit value from a fixed constant to a dynamically determined value. By calculating the current limit value based on the ratio of excitation current to torque current and comparing it with a predetermined threshold, the system adapts the current limit parameter to match the actual operational needs, resolving the contradiction between protection and responsiveness.
2Speed
If the excitation current command value is amplified to compensate for rotor flux response delay, then the rotor flux response is improved, but the current command value exceeds the maximum allowable current limit causing insufficient current flow
Solution Approach 1:
The patent applies preliminary action by determining the current limit value in advance based on the expected relationship between excitation current and torque current. The current limit determination unit calculates and sets the appropriate current limit value before the excitation current command is executed, ensuring that the amplified current command can be properly limited without causing insufficient current flow or exceeding safety thresholds.
Solution Approach 2:
The patent uses feedback by continuously monitoring the relationship between excitation current and torque current to dynamically adjust the current limit value. The current limit determination unit receives feedback about the actual current conditions and adjusts the limit accordingly, ensuring that the system maintains both rapid response capability and current limit compliance.
Data Source
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AI summary
A motor control device is provided with: current command value calculating means which, based on a torque command value input from the outside and the rotation speed of a motor, calculates a basic current command value; first compensation means which compensates for delay in the rotor magnetic flux response of the motor (3) by amplifying the basic current command value; first current command value limiting means for restricting a post-compensation current command value by a first current limiting value; second compensation means which, based a current amplification command value calculated by the first compensation means and a first post-limitation current command value calculated by the first current value limiting means, calculates a compensation value for the amplified current command value; adding means which calculates the post-compensation current command value by adding the amplified current command value and the compensation value; and motor control means which, based on the first limited current command value, controls the motor (3), the second compensation means calculating, as the compensation value, a command value corresponding to a portion limited by the first current limiting value of the amplified current amplification command value.