Resolver-Based Wheel Speed Sensor Low-Speed Velocity Measurement
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Solution Overview
Problem
Frequency-based wheel speed sensors, such as tachometers, fail to produce usable signals at low speeds, limiting their effectiveness in applications like unmanned vehicles where accurate speed information is necessary down to zero speed.
Innovation Solution
A resolver-based wheel speed sensor system that includes a stator and rotor connected to a rotating wheel, using a resolver-to-digital converter to generate digital signals indicative of angular position, and a digital controller to calculate wheel velocity, allowing operation over a wide range of speeds including zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency-based wheel speed sensors are used, then the sensor structure is simple, but the sensor cannot produce usable signals at low speeds
Solution Approach 1:
The patent replaces frequency-based mechanical sensing with a resolver-based electromagnetic positioning system. The resolver uses electromagnetic fields between stator and rotor windings to generate position signals that can be differentiated to obtain velocity, enabling reliable low-speed measurement including zero speed while maintaining a relatively simple structure.
Solution Approach 2:
The patent changes the measurement parameter from frequency output to position output. By measuring angular position with high resolution and calculating velocity from position changes over time, the system achieves accurate low-speed and zero-speed measurement capability that frequency-based systems cannot provide.
2Measurement precision
If analog position signals from resolvers are used, then the device complexity is reduced, but velocity information down to zero speed is not provided and precision is limited
Solution Approach 1:
The patent implements a feedback-based velocity calculation where the digital controller continuously processes position signals to derive velocity information. The system uses the relationship between consecutive position measurements to calculate velocity, providing precise velocity data including at zero speed through mathematical differentiation of position over time.
Solution Approach 2:
The patent introduces a digital controller as an intermediary that bridges the resolver position output and the required velocity information. This intermediary performs digital differentiation of position signals to generate accurate velocity measurements, resolving the limitation of analog resolver outputs without adding significant hardware complexity.
3Loss of information
If frequency-based sensors are used for unmanned vehicles, then the system is simpler, but accurate speed information at zero speed cannot be obtained
Solution Approach 1:
The patent replaces frequency-based mechanical sensing with electromagnetic field-based position sensing. The resolver measures angular position through electromagnetic coupling between stator and rotor, and velocity is derived from position changes, providing continuous accurate speed information including at zero speed where frequency-based systems fail.
Solution Approach 2:
The patent makes the sensor system universal by enabling it to function accurately across the entire speed range from zero to high speeds. The same resolver-based position measurement system provides reliable velocity information for all operating conditions of unmanned vehicles, eliminating the need for different sensor types for different speed ranges.
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
Enables accurate velocity measurement at low speeds, providing reliable control for unmanned vehicles and reducing mechanical complexity and temperature limitations, with redundant signals for increased reliability.
Implementation Method 1
When a rotor winding is excited with an AC reference signal, the stator windings produce AC voltage outputs that vary in amplitude according to the sine and cosine of rotor position
Data Source
AI summary
A method of determining a speed of a wheel that involves providing a resolver having a rotor and a stator which resolver produces at least one output signal, operatively connecting the rotor to a wheel such that the resolver is rotated by the rotation of the wheel, producing digital signals indicative of a position of the rotor relative to the stator based on the at least one output signal, and calculating a velocity of the wheel from the digital signals. The digital signals may be used alone or in conjunction with analog wheel speed signals. Also a speed sensor for practicing this method.