Current Sensor Error Compensation via Virtual Current and Disturbance Observer
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Solution Overview
Problem
Current control devices face challenges in accurately suppressing periodic disturbances caused by offset and gain errors in current sensors, which lead to oscillations and noise, particularly in motor systems, as existing methods require external torque sensors and increase calculation loads.
Innovation Solution
A control device is designed to correct gain and offset errors in current sensors by generating a voltage command, calculating a virtual current value, and using a periodic disturbance observer to estimate and compensate for errors, thereby reducing periodic disturbances without the need for external sensors and minimizing calculation loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a periodic disturbance observer is used to suppress torque ripple, then suppression effect is improved, but calculation load increases
Solution Approach 1:
The patent extracts only the necessary components for disturbance observation by using a simplified plant model that excludes certain terms (e.g., setting Ldq = 0). This extraction approach maintains the essential disturbance suppression capability while removing unnecessary calculation elements, thereby reducing computational load while preserving the suppression effect.
Solution Approach 2:
The patent changes the parameters of the plant model by simplifying the mathematical expressions and reducing the order of the model. By modifying the model parameters to be less computationally intensive while retaining the core functionality of disturbance observation, the calculation load is reduced without significantly compromising the suppression performance.
2Measurement precision
If system identification is performed for accurate model acquisition, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs system identification in advance during the design phase to obtain the plant model parameters. By completing the time-consuming identification process beforehand, the accurate model is stored and reused during actual operation, thereby achieving high measurement precision without incurring time delays during real-time control execution.
Solution Approach 2:
The patent prepares the plant model parameters through prior system identification and stores them for future use. This beforehand preparation cushions against the time loss that would otherwise occur during real-time operations, allowing the system to maintain high accuracy without repeated identification processes.
3Measurement precision
If external torque sensors are used for disturbance measurement, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent enables the system to self-measure disturbances using its own internal sensors and a simplified plant model, eliminating the need for external torque sensors. The system serves itself by observing disturbances through electrical measurements and model-based estimation, thereby maintaining measurement precision while reducing device complexity and cost.
Solution Approach 2:
The patent introduces a simplified plant model as an intermediary that bridges the gap between available electrical measurements and disturbance estimation. This mathematical model acts as a mediator that allows accurate disturbance measurement without requiring direct mechanical sensing, thereby avoiding the complexity of external torque sensors.
Data Source
AI summary
Periodic disturbance occurs in current etc. due to offset error and gain error of a current sensor used in a control device. A voltage command value is generated from a current command value and a current detection value by the current sensor in a current control section. The generated voltage command value is inputted to a plant model section, and a virtual current value is calculated. The virtual current value is inputted to a periodic disturbance observer via a coordinate transform section, and a compensation value is calculated. The compensation value is superimposed on the current detection value via a coordinate inverse-transform section, and the current detection value of the current sensor is corrected.