Electric Machine Torque Control via Rotor Sensor Offset Adjustment
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Solution Overview
Problem
Hybrid/electric vehicles face challenges in accurately controlling torque due to offset errors in rotor position sensors, leading to potential unintended vehicle acceleration or motion, which existing technologies fail to address effectively.
Innovation Solution
A control system that includes a rotor position sensor, an inverter, and a controller, which converts DC electrical power to AC and back, adjusts the signal from the rotor position sensor to include offset values to accurately control the electric current or voltage delivered to the stator, based on the switching mode and torque differences, to drive the electric machine towards a commanded torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rotor position sensor signal is used directly for torque control, then control system is simple, but torque control accuracy deteriorates due to offset errors
Solution Approach 1:
The system implements feedback by continuously monitoring the difference between commanded torque and measured torque, and adjusting the rotor position sensor signal offset accordingly. The controller calculates measured torque based on DC electrical power input and rotational speed, compares it with commanded torque, and uses this feedback to correct offset errors in the rotor position sensor signal, thereby improving torque control accuracy without requiring complex additional hardware.
Solution Approach 2:
The system replaces complex mechanical torque sensing mechanisms with an electrical measurement approach. Instead of using mechanical sensors to directly measure torque, the system calculates measured torque based on electrical parameters (DC electrical power input from battery and rotational speed), substituting mechanical measurement with electrical field-based measurement to achieve accurate torque control.
2Reliability
If rotor position sensor offset is not corrected, then control system is simple, but unintended vehicle acceleration or motion occurs
Solution Approach 1:
The system uses feedback control to detect and correct offset errors in the rotor position sensor. By continuously monitoring torque control performance and comparing commanded torque with measured torque (calculated from DC electrical power and rotational speed), the system identifies offset errors and adjusts the rotor position sensor signal accordingly, preventing unintended vehicle acceleration while maintaining control system reliability.
Solution Approach 2:
The system performs preliminary correction of rotor position sensor offset errors before they can cause unintended vehicle motion. The controller proactively calculates offset adjustments based on the difference between commanded and measured torque, and applies corrections to the rotor position sensor signal in advance, preventing harmful effects before they occur.
3Adaptability or versatility
If inverter switching mode changes, then system adaptability improves, but torque control accuracy deteriorates due to mode transition effects
Solution Approach 1:
The system dynamically adjusts the rotor position sensor offset based on the inverter's switching mode. The controller monitors which switching mode the inverter is operating in (first or second mode) and applies appropriate offset corrections tailored to each mode's characteristics. This dynamic adaptation allows the system to maintain accurate torque control across different operating conditions and switching modes.
Solution Approach 2:
The system changes the rotor position sensor signal parameters (offset values) based on the inverter's switching mode. By adjusting the offset parameter according to the active switching mode, the system compensates for mode-specific measurement errors and maintains accurate torque control across different operational states, resolving the contradiction between adaptability and measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances torque monitoring accuracy, prevents unintended vehicle motion, and optimizes drive control by correcting offset errors in rotor position sensors, ensuring precise torque control and efficient energy utilization in hybrid/electric vehicles.
Implementation Method 1
The inverter is configured to convert DC electrical power from the battery into AC electrical power
Implementation Method 2
The inverter is also configured to convert AC electrical power from the electric machine into DC electrical power
Implementation Method 3
control an electric current being delivered to the stator relative to the angular position of the rotor to drive a first estimated torque of the electric machine toward a commanded torque
Implementation Method 4
receive a signal from the rotor position sensor that is indicative of an angular position of the rotor
Data Source
AI summary
A vehicle includes a battery, an electric machine, a rotor position sensor, an inverter, and a controller. The electric machine is configured to propel the vehicle. The electric machine has a stator and a rotor. The inverter is disposed between the battery and the electric machine. The inverter is configured to convert DC electrical power from the battery into AC electrical power. The inverter is configured to deliver the AC electrical power to the electric machine. The controller is programmed to adjust the offset position of the rotor position senor and control the torque of the electric machine based on the offset position of the rotor position sensor.