Resolver-Based Vehicle Location Determination via Motor Feedback
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Solution Overview
Problem
Autonomous vehicles face challenges with wheel sensors due to exposure to harsh conditions and ambiguity in changing motion modes, leading to design complexity and increased costs.
Innovation Solution
The use of a displacement measuring device, such as a resolver, coupled with an electric motor's rotor and stator, to determine the orientation and displacement of the rotor, allowing for precise control of the vehicle's braking, steering, and acceleration systems, with a processor operating these systems based on the determined displacement and its derivatives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wheel sensors are used to measure speed and direction, then navigation capability is improved, but device complexity and cost increase due to harsh operating conditions and ambiguous readings during motion mode changes
Solution Approach 1:
The patent extracts the sensing function from the harsh wheel environment and relocates it to the motor assembly. The resolver is coupled to the motor shaft or rotor, measuring motor position and speed instead of wheel position and speed. This extraction removes the sensor from the harmful environment while maintaining navigation measurement capability.
Solution Approach 2:
The resolver serves multiple functions: it provides position feedback for motor control, speed feedback for navigation, and direction information for trajectory determination. By making the motor assembly a multi-functional sensing platform, the patent eliminates the need for separate wheel-mounted sensors.
2Ease of operation
If wheel sensors are attached to wheels exposed to harsh conditions, then speed and direction measurement is enabled, but reliability decreases due to sensor damage from potholes and curbs
Solution Approach 1:
The sensing function is extracted from the vulnerable wheel location and relocated to the protected motor assembly. The resolver remains stationary or moves with the motor housing, shielded from potholes, curbs, and other road hazards that would damage wheel-mounted sensors.
Solution Approach 2:
The motor shaft or rotor acts as an intermediary between the protected motor assembly and the wheels. The resolver measures the intermediary's motion, which correlates to wheel motion through the drivetrain, thereby protecting the sensor while maintaining measurement capability.
3Measurement precision
If traditional wheel sensors are used, then navigation data is obtained, but measurement precision decreases during transitions from forward to reverse motion
Solution Approach 1:
The resolver provides continuous feedback on motor rotor position and speed. By monitoring the motor's rotational direction and speed, the system can accurately determine when the vehicle transitions between forward and reverse motion, eliminating the ambiguity that plagues wheel sensors during mode changes.
Solution Approach 2:
The patent replaces the mechanical wheel sensor system with an electromagnetic sensing system (resolver) coupled to the motor. This substitution eliminates the mechanical ambiguity issues that occur when wheels transition between forward and reverse rotation, as the resolver can continuously and unambiguously measure motor rotor position.
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 enables accurate and reliable navigation and control of autonomous vehicles by effectively addressing the limitations of wheel sensors, reducing complexity and cost, and providing precise vehicle location and trajectory determination.
Implementation Method 1
In some instances, the displacement measuring device may be a resolver.
Data Source
AI summary
A method and apparatus are provided for determining the location of a vehicle. According to one aspect the method and apparatus the movements of motor rotors in a vehicle are monitored and used to determine speed, travel distance and/or travel path of a vehicle may be determined. Using various navigation techniques, the distance and travel path may then be used to determine the vehicle's location. Furthermore, movements of the motor rotors may also be used to report the positions of the steering and drive systems for the purpose of informing the vehicle controller as a method of feedback.