Wiper Control Device Simplified Motor State Testing
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Solution Overview
Problem
Existing wiper control devices require complex circuits for testing wiper motor and drive circuit states, necessitating additional diodes for microcomputer protection and complicating the testing process.
Innovation Solution
A wiper control device with a simplified configuration using switching elements to generate a test voltage, allowing the microcomputer to determine wiper motor and drive circuit states through computed motor terminal voltage differences, eliminating the need for complex voltage dividers and diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complex test circuit with additional diodes and voltage dividers is used to test wiper motor and drive circuit states, then the testing capability is improved, but the device complexity increases
Solution Approach 1:
The patent merges the test circuit functionality with the existing drive circuit by utilizing the same switching elements (FETs) and voltage divider circuitry that are already present in the drive circuit. The microcomputer controls the switching elements to generate test voltages and measures voltages through the same ADC interface used for normal operation, eliminating the need for separate dedicated test components.
Solution Approach 2:
The switching elements and voltage divider circuit are designed to serve dual purposes: they function as part of the drive circuit during normal wiper operation and as test circuit components when activated by the microcomputer. This multi-functionality allows the same hardware to perform both driving and testing functions without requiring additional dedicated test components.
2Reliability
If additional diodes are added to protect the microcomputer from high voltages during testing, then the protection capability is improved, but the device complexity increases
Solution Approach 1:
The voltage divider circuit is designed with appropriate resistance values that inherently limit the voltage reaching the microcomputer to safe levels before any potential overvoltage events occur. This pre-configured voltage division provides continuous protection without requiring additional protective components like diodes, as the voltage is already reduced to microcomputer-safe levels through the divider ratio.
3Device complexity
If a simplified configuration without additional diodes and complex voltage dividers is used, then the device complexity is reduced, but the testing capability may be compromised
Solution Approach 1:
The microcomputer dynamically changes the resistance values in the voltage divider circuit by controlling the switching elements to be in ON or OFF states. This allows the circuit to present different resistance configurations during testing versus normal operation, enabling accurate voltage measurements and motor state determination without requiring additional physical components.
Data Source
AI summary
A voltage divider circuit is configured by a resistor having one end connected to a positive electrode of a battery configuring a power source and another end connected to a first terminal that is a motor terminal on one side of a wiper motor, and a FET having one end connected to the first terminal and another end grounded. The voltage divider circuit lowers a voltage of the battery to a test voltage that does not cause the wiper motor to rotate. A microcomputer detects a detected voltage that is a voltage output from the voltage divider circuit to a second terminal that is a motor terminal on the other side of the wiper motor via the first terminal of the wiper motor and the wiper motor, and computes a motor terminal voltage, this being a potential difference between the first terminal and the second terminal, from the detected voltage.