AC Motor Torque Feedback Control Under Sensor Offset Error
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Solution Overview
Problem
AC motor control devices face issues with voltage phase control due to offset errors in rotation angle sensors, leading to unintended torque generation, power imbalance, and reduced drivability.
Innovation Solution
An AC motor control device with an inverter, torque feedback control unit, and switching command generation unit, which calculates and limits the voltage phase using a secondary limit range set based on the maximum offset error of the rotation angle sensor, thereby minimizing the influence of offset errors on voltage phase control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotation angle sensor is used to detect the rotor rotation angle for voltage phase control, then the AC motor can be controlled based on rotor position, but offset errors in the sensor cause unintended torque generation and power imbalance
Solution Approach 1:
The patent implements feedback control by calculating the actual torque from the rotation angle sensor detection and comparing it with the command torque. The torque feedback control unit adjusts the voltage phase based on the torque deviation, creating a closed-loop control system that compensates for sensor offset errors dynamically.
Solution Approach 2:
The patent changes the control parameter from direct rotation angle control to torque-based voltage phase control. By calculating the voltage phase based on torque feedback rather than directly using the rotation angle sensor output, the system transforms the control approach to eliminate the influence of sensor offset errors on voltage phase determination.
2Device complexity
If the voltage phase is calculated without considering offset errors, then the control calculation is simple, but unintended torque generation and power imbalance occur
Solution Approach 1:
The torque feedback mechanism continuously monitors the actual torque output and feeds it back to the control unit. This feedback loop enables the system to detect and compensate for unintended torque generation caused by sensor offsets without requiring complex recalibration procedures.
Solution Approach 2:
The patent introduces torque as an intermediary parameter between the rotation angle detection and the voltage phase control. Instead of directly using the potentially erroneous rotation angle data, the system uses torque calculation as an intermediate step that filters out the impact of sensor offsets before determining the voltage phase.
3Speed
If traditional voltage phase control is used, then the system responds to command torque changes, but the response to sudden changes is delayed due to offset errors
Solution Approach 1:
The torque feedback control operates continuously, constantly adjusting the voltage phase based on the current torque deviation. This continuous control action ensures that the system responds immediately to sudden changes in command torque without the delays or instability that would result from periodic correction or offset compensation.
Solution Approach 2:
The real-time torque feedback enables the control system to detect sudden changes in command torque immediately and adjust the voltage phase without delay. The feedback loop operates continuously, ensuring that the actual torque follows the command torque closely even during rapid transitions.
Data Source
AI summary
A limit range setting section sets a primary limit range from a primary lower limit phase to a primary upper limit phase within an interval from a minimum torque phase to a maximum torque phase in a voltage phase-torque map. The limit range setting section calculates a phase obtained by adding a maximum amount of offset error of a rotation angle sensor to a zero phase as a secondary upper limit phase, and calculates a phase obtained by subtracting the maximum amount of offset error from the zero phase as a secondary lower limit phase. The limit range setting section sets a range from the primary lower limit phase to the secondary upper limit phase when a command torque is negative, and a range from the secondary lower limit phase to the primary upper limit phase when the command torque is positive as a secondary limit range.