Electric Machine Rotor Positioning for Zero-Speed Launch Torque
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Solution Overview
Problem
Electric vehicles may struggle to launch from a standstill due to insufficient torque output from the propulsion system, especially on inclined surfaces, leading to potential unintended movement or failure to move, and oversizing the inverter or motor to address this issue increases system costs and losses.
Innovation Solution
Adjusting the angular position of the electric machine's rotor to optimize torque output at zero speed by positioning it at specific angles to maximize torque or minimize losses, using a controller to adjust the rotor position based on surface grade and vehicle conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inverter is oversized to provide sufficient torque for vehicle launch on inclined surfaces, then the vehicle startability is improved, but the system cost and energy losses increase
Solution Approach 1:
The patent changes the operational parameters of the electric machine by adjusting the rotor angular position to optimize torque output. By controlling the rotor position angle within specific ranges (e.g., 0-30 degrees or 330-360 degrees), the system achieves improved startability without requiring an oversized inverter, thus avoiding increased energy losses and system costs
Solution Approach 2:
The system performs preliminary action by pre-positioning the rotor at optimal angular positions before vehicle launch. The controller anticipates launch conditions and adjusts the rotor position in advance to ensure maximum torque availability, eliminating the need for oversizing components
2Force
If the electric motor is oversized to produce more torque for vehicle propulsion, then the torque output capacity is improved, but the system cost increases
Solution Approach 1:
The patent employs parameter changes by adjusting the rotor position angle to maximize torque output from the existing motor size. By controlling the angular position within specific ranges, the system achieves higher torque capacity without physically enlarging the motor, thereby reducing system cost while maintaining ease of manufacture
Solution Approach 2:
The system introduces dynamics by making the rotor position adjustable and controllable rather than fixed. The controller dynamically positions the rotor based on operating conditions, enabling the motor to deliver optimized torque output without requiring a larger physical size
3Force
If the rotor angular position is adjusted to increase torque output capacity, then the torque generation capability is improved, but the device complexity increases
Solution Approach 1:
The patent simplifies the approach by changing only one key parameter - the rotor position angle - while keeping other system components unchanged. The controller adjusts the rotor to specific angular ranges (e.g., 0-30 degrees, 330-360 degrees) to maximize torque, avoiding the need for complex mechanical modifications or additional hardware
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
Enhances torque output and consistency at zero speed, reducing the need for oversized inverters or motors, and maintaining consistent performance across varying road grades without increasing system losses.
Implementation Method 1
An electric machine configured to propel a vehicle... an electric machine may have a torque output capacity to generate 52,000 Newtons of tractive effort at zero vehicle speed
Implementation Method 2
an angular position of a rotor of an electric machine may be adjusted from a position where the electric machine is capable of generating less torque at zero speed to generating more torque at zero speed
Data Source
AI summary
Methods and systems for controlling torque of an electric machine that propels a vehicle when the vehicle is stopped are described. The methods and systems may be applied to synchronous and induction electric machines that are configured to propel a vehicle. The methods and systems may allow a consistent amount of torque to be delivered by an electric machine when vehicle speed and electric machine speed is zero.