Motor Load Torque Estimation via Dynamic Time Constant
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Solution Overview
Problem
Existing load torque estimation methods for electric motors face challenges in accurately estimating load torque, especially when the control target's state changes or when the electric motor operates over a wide range of rotational speeds, leading to increased estimation errors.
Innovation Solution
A load torque estimation apparatus that updates the mechanical time constant of the motor model based on the actual rotational speed, using derived mechanical and electrical time constants to improve the accuracy of load torque estimation by adapting the model in real-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed control model is used for load torque estimation, then the device complexity is reduced, but the measurement precision deteriorates when the motor operates over a wide range of rotational speeds
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed control model to a dynamic model that automatically adapts to changing motor operating conditions. The mechanical time constant is updated in real-time based on the actual rotational speed, allowing the estimation model to remain accurate across the entire speed range without requiring manual intervention or complex switching mechanisms.
Solution Approach 2:
The patent implements parameter changes by modifying the mechanical time constant parameter in the control model based on the motor's rotational speed. Instead of using a single fixed parameter value, the system adjusts the parameter dynamically according to the operating conditions, thereby maintaining high estimation accuracy across different speed ranges while keeping the overall system relatively simple.
2Measurement precision
If the mechanical time constant is updated in real-time based on rotational speed, then the load torque estimation accuracy improves, but the calculation complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-establishing the relationship between rotational speed and mechanical time constant through derivation or lookup tables. This allows the system to quickly retrieve or calculate the appropriate time constant value during operation without performing complex real-time derivations, thereby reducing computational burden while maintaining accuracy.
Solution Approach 2:
The system uses feedback by continuously monitoring the actual rotational speed and using this information to update the mechanical time constant in the estimation model. This closed-loop approach ensures that the model parameters remain synchronized with the actual operating conditions, improving accuracy without requiring overly complex calculation processes.
3Reliability
If a single control model is used for all rotational speeds, then the ease of operation is improved, but the reliability of load torque estimation deteriorates at extreme speeds
Solution Approach 1:
The patent applies universality by creating a unified estimation framework that works across the entire rotational speed range. Instead of requiring separate models for different speed ranges, the system uses a single flexible model structure that adapts to various operating conditions through dynamic parameter adjustment, thereby maintaining both reliability and ease of operation.
Data Source
AI summary
A load torque estimation apparatus estimates load torque of an electric motor. The apparatus includes an estimation part configured to input a controlling value for controlling the electric motor and an actually measured value of a rotational speed of the electric motor to a model and estimating load torque of the electric motor; and a derivation part configured to derive a mechanical time constant of the electric motor corresponding to the actually measured value of the rotational speed of the electric motor. The estimation part is configured to update, according to a timing of acquiring the actually measured value of the rotational speed of the electric motor, the mechanical time constant included in the model by using the mechanical time constant corresponding to the acquired actually measured value and estimate the load torque of the electric motor by using the updated model.