Dynamic Load Torque Estimation for Electric Motors
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Solution Overview
Problem
Existing load torque estimation methods for electric motors face inaccuracies due to changes in the state of the control target, as they assume fixed mechanical and electrical time constants regardless of rotational speed, leading to errors in estimated load torque.
Innovation Solution
The proposed solution involves a load torque estimation apparatus that updates the mechanical and electrical time constants based on actual rotational speed or load torque values, using approximation formulas or tables derived from experimental relationships, to improve the accuracy of load torque estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fixed mechanical and electrical time constants are used in the estimation model, then the device complexity is reduced and ease of operation is improved, but the measurement precision of load torque deteriorates due to inaccuracies when the state of the control target changes
Solution Approach 1:
The patent applies the dynamics principle by transitioning from fixed time constants to dynamically updated time constants. The mechanical and electrical time constants are no longer static parameters but are continuously updated based on the current state of the motor (rotational speed, load torque). This allows the estimation model to adapt to changing operating conditions, thereby improving load torque estimation accuracy without requiring a fundamentally more complex system architecture.
Solution Approach 2:
The patent implements parameter changes by modifying the time constant parameters (mechanical time constant and electrical time constant) based on the current operating state. Instead of using fixed parameter values, the system adjusts these parameters dynamically according to rotational speed and load torque conditions. This approach enables the model to maintain high estimation accuracy across varying operating conditions while keeping the overall model structure relatively simple.
2Reliability
If fixed time constants are assumed in the estimation model, then the ease of operation is improved and implementation is simplified, but the reliability of load torque estimation deteriorates when the state of the control target changes
Solution Approach 1:
The patent applies feedback by using the estimated load torque and rotational speed information to continuously update the mechanical and electrical time constants. The system feeds back the current state measurements into the model to adjust the parameters, creating a closed-loop adaptation mechanism. This feedback approach ensures that the estimation model remains reliable under varying operating conditions while maintaining relatively simple operation through automated parameter adjustment.
3Measurement precision
If dynamic updating of time constants is implemented, then the measurement precision of load torque is improved, but the device complexity increases due to additional derivation and update mechanisms
Solution Approach 1:
The patent applies preliminary action by pre-establishing the relationships between time constants and operating parameters (rotational speed, load torque) through derivation. The mechanical and electrical time constants are derived in advance based on the motor's electrical characteristics and mechanical properties. This preliminary derivation work allows the system to perform dynamic updates during operation without requiring complex real-time calculations, thereby improving measurement precision while limiting the increase in system complexity.
Data Source
AI summary
A load torque estimation apparatus inputs a controlling value for controlling the electric motor and an actually measured value of a rotational speed of the electric motor to a model to estimate load torque of the electric motor; and derives a mechanical time constant of the electric motor corresponding to the load torque estimated by the estimation part. The load torque estimation apparatus updates the mechanical time constant included in the model by using the mechanical time constant corresponding to the load torque estimated at an (n−1)th control period (where n denotes an integer greater than or equal to 2) and estimates the load torque of the electric motor at an nth control period by inputting the controlling value and the actually measured value acquired at the nth control period to the model acquired through the updating.