Phase Current Offset Error Detection in EPS Motor Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electric Power Steering (EPS) systems using Permanent Magnet Synchronous Machines (PMSM) face issues with torque ripple and current measurement errors due to offset errors in phase current measurements, leading to motor torque errors opposite to the desired command, which can result in increased effort for the driver.
Innovation Solution
A system and method for detecting current measurement offset errors using a programmable high pass filter and gain/phase compensation modules to filter and compensate voltage commands, determining offsets in the stator reference frame, thereby improving diagnostic robustness and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed loop current control is used to minimize error between commanded and measured currents, then current tracking accuracy is improved, but offset errors in phase current measurement cause torque ripple and motor position dependent torque errors
Solution Approach 1:
The system performs preliminary detection of offset errors in phase current measurements using high pass filtering and gain/phase compensation before these errors can cause significant torque ripple. By detecting and flagging offset errors proactively, the system prevents reliability issues from developing
Solution Approach 2:
The patent implements a feedback mechanism where the detected offset errors are used to adjust or compensate the current control system. The error detection module continuously monitors for offset conditions and provides feedback to maintain accurate torque control, resolving the contradiction between measurement precision and reliability
2Extent of automation
If phase current measurements are transformed into synchronous frame via Park Transform, then FOC torque control is enabled, but offset errors produce torque in opposite direction from motor torque command
Solution Approach 1:
The patent introduces an intermediary error detection module that sits between the Park Transform and the torque control execution. This intermediary detects offset errors in the transformed synchronous frame measurements and prevents them from causing harmful opposite direction torque by flagging or compensating the erroneous measurements
3Measurement precision
If high pass filtering is applied to detect offset errors, then measurement accuracy is improved, but system complexity increases
Solution Approach 1:
The patent changes the parameter domain by transforming the current measurements into the synchronous reference frame using Park Transform before applying high pass filtering. This parameter change allows the offset detection to be performed more effectively while keeping the added complexity manageable through the use of standard control transformations
Data Source
AI summary
A system for detecting offset error in a power steering system is provided. The system includes a programmable high pass filter module configured to filter a final voltage command and generate a filtered final voltage command. The filtered final voltage command includes the sinusoidal component, a gain and phase compensation module configured to perform a gain compensation and a phase compensation on the filtered final voltage command to generate a compensated final voltage command. An error detection module is configured to determine an offset of the compensated final voltage command in a stator reference frame.