Motor Load Meter Accuracy in Nonlinear Control Regions
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Solution Overview
Problem
Existing motor control systems face inaccuracies in load meter calculations due to nonlinear motor operation, where the proportional relationship between torque command and motor output is lost, leading to significant errors in load information, especially when motor speed and efficiency vary.
Innovation Solution
A motor control apparatus that measures the relationship between motor speed, output, and affecting factors to compute accurate load information using a function or table, and applies corrections to the torque command to ensure accurate load meter values across the entire speed range, including nonlinear regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the motor operates in the nonlinear control region to achieve high-speed and high-output performance, then the motor output performance is improved, but the load meter value computed based on the torque command deviates from the correct value
Solution Approach 1:
The patent changes the parameter used for load meter computation from torque command to amplifier output power. This parameter substitution resolves the contradiction because amplifier output power maintains a proportional relationship with motor output even in nonlinear regions, whereas torque command loses its proportionality. The load meter computing unit now uses amplifier output power W and motor efficiency η to compute load meter value LM, ensuring accuracy across the entire speed range including nonlinear regions.
2Ease of operation
If the load meter value is computed using torque command to simplify the computation process, then the ease of operation is improved, but the measurement precision deteriorates in nonlinear regions
Solution Approach 1:
The patent substitutes the computation parameter from torque command to amplifier output power. This change maintains computational simplicity while improving accuracy because amplifier output power is directly measurable and maintains proportionality with motor output in both linear and nonlinear regions. The load meter computing unit performs straightforward computation using amplifier output power W and motor efficiency η stored in memory, avoiding complex corrections while ensuring accuracy.
3Measurement precision
If the load meter value is computed using amplifier output power and motor efficiency, then the measurement precision is improved across the entire speed range, but the device complexity increases
Solution Approach 1:
The patent implements a self-service mechanism where the load meter computing unit automatically acquires amplifier output power W from the amplifier and motor efficiency η from memory storage. The system self-manages the data acquisition and computation process without requiring external intervention or complex coordination between multiple units. This approach improves accuracy while keeping the device structure relatively simple by leveraging existing system components.
Solution Approach 2:
The patent makes the load meter computing unit multi-functional by enabling it to compute load meter values accurately across the entire motor speed range using a unified computation formula based on amplifier output power and motor efficiency. This universal approach eliminates the need for separate computation methods for linear and nonlinear regions, simplifying the overall system while maintaining high precision throughout the operating range.
Data Source
AI summary
A motor control apparatus for computing or outputting motor load information, comprises: a storage unit which stores a function or table obtained in advance based on parameters used for the computation of the load information and on an actually measured value of a motor output or motor torque; and a load meter computing unit which computes the load information from the function or table stored in the storage unit by using the parameters used for the computation of the load information. With the above configuration, the load meter is computed in such a manner as to accurately indicate the load condition of a motor in real time over the entire speed range of the motor including the nonlinear control region of the motor, and the motor is controlled using the thus computed value or the computed value is displayed on a display unit.