Wheel Speed Sensor Interface Compensation for Supply Voltage Transients
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Solution Overview
Problem
Voltage transients in automotive electrical systems can cause erroneous wheel speed information from wheel speed sensors, affecting the reliability of safety-critical systems like anti-lock braking systems.
Innovation Solution
A wheel speed sensor interface circuit that detects supply voltage transients and injects a compensation current to maintain accurate sensor output, using a detector circuit with a current mirror to emulate and counteract the extra current caused by transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wheel speed sensors are used in automotive electrical systems, then wheel speed information can be obtained for safety systems, but voltage transients from the electrical system cause erroneous sensor output
Solution Approach 1:
The patent detects voltage transients that cause erroneous sensor output and converts this harmful effect into a beneficial compensation signal. The detector circuit identifies transient events and generates a compensation current that is injected into the sensor signal path, effectively canceling out the erroneous current caused by the voltage transient. This transforms the harmful voltage spike into a corrected accurate measurement.
Solution Approach 2:
The patent introduces a detector circuit and compensation current source as intermediary elements between the wheel speed sensor and the processing system. These intermediaries detect the voltage transient condition and insert a compensating signal into the signal path, mediating between the harmful electrical interference and the sensor output to preserve measurement accuracy.
2Reliability
If voltage transient compensation is added to the sensor circuit, then sensor output accuracy is maintained, but circuit complexity increases
Solution Approach 1:
The patent combines multiple functions into integrated circuit blocks. The detector circuit monitors both the reference voltage and sensor output, while the compensation current source is integrated into the signal processing path. This merging of detection and compensation functions into unified circuit modules reduces overall complexity compared to having separate independent systems.
Solution Approach 2:
The compensation system is self-regulating through feedback. The detector circuit automatically detects voltage transients and the compensation current source automatically generates the appropriate compensating signal without external intervention. The system serves itself by using its own detected error condition to generate the correction, eliminating the need for complex external control mechanisms.
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
Ensures that the wheel speed sensor output accurately represents the rotational speed of the wheels, even during voltage spikes, thereby preventing erroneous functioning of safety systems.
Implementation Method 1
detecting a transient occurring within a voltage source powering the wheel speed sensor
Implementation Method 2
The detector circuit includes a current mirror coupled to the voltage source, wherein the current mirror is configured to emulate an extra current produced within the wheel speed sensor caused by the transient
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A wheel speed sensor interface receives an analog signal from a wheel speed sensor and converts the analog signal to a digital wheel speed sensor output signal. A detector circuit is configured to detect a transient occurring within a voltage source powering the wheel speed sensor, and compensate the digital wheel speed sensor output signal as a function of the detection of the transient so that it is an accurate representation of a wheel speed detected by the wheel speed sensor. The detector circuit includes a current mirror coupled to the voltage source, and outputs a compensation current to a current comparator of the wheel speed sensor interface.