Wiper Motor Control Circuit Speed Deviation Handling
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Solution Overview
Problem
Existing wiper control devices face challenges in smoothly controlling wiper motor operation when overloaded, due to complex and costly structures for load detection and high processing loads related to computing driving voltage and rotational speed.
Innovation Solution
A wiper device with a speed detecting section, a driving section, and a control section that adjusts voltage to the wiper motor to reduce rotational speed when deviation exceeds a threshold, preventing overrunning by supplying deceleration voltage and gradually lowering target rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the rotational speed of the wiper motor is increased to eliminate deviation from target speed, then the speed control accuracy is improved, but the motor becomes overloaded and unstable operation occurs
Solution Approach 1:
The patent applies dynamics by making the target rotational speed variable rather than fixed. The control section dynamically adjusts the target rotational speed based on the current rotational speed and deviation magnitude, allowing the system to adapt to changing load conditions. This resolves the contradiction by enabling speed correction without causing motor overload, as the target speed is adjusted in real-time based on actual operating conditions.
Solution Approach 2:
The patent changes the parameter of target rotational speed from a constant value to a variable value that depends on current operational state. By calculating a new target rotational speed that incorporates the current speed and deviation, the system modifies the speed parameter adaptively. This allows the motor to recover from overload conditions while maintaining control accuracy, resolving the contradiction between speed precision and operational stability.
2Measurement precision
If a separate load detector is added to detect load torque, then the load detection precision is improved, but the device complexity and cost increase
Solution Approach 1:
The patent applies self-service by enabling the wiper motor control system to detect load conditions using its own existing sensors and control data, without requiring external load detection devices. The control section calculates load state by analyzing the relationship between commanded rotational speed, actual rotational speed, and deviation, allowing the system to self-diagnose overload conditions. This eliminates the need for separate load detectors while maintaining accurate load monitoring.
Solution Approach 2:
The patent makes the existing speed sensing and control systems multi-functional by using them for both speed control and load detection. The same speed detecting section and control section that manage motor operation also detect overload conditions by analyzing speed deviation patterns. This universal approach allows load detection without adding dedicated load sensing hardware, reducing device complexity while maintaining detection capability.
3Measurement precision
If complex computation is performed to determine driving voltage from duty ratio and rotational speed, then the control precision is improved, but the processing load increases
Solution Approach 1:
The patent extracts the essential control function from complex voltage computation by directly controlling rotational speed through the speed detecting section and control section. Instead of computing driving voltage from duty ratio and speed relationships, the system directly adjusts the target rotational speed based on deviation, simplifying the control process. This extraction of the core speed control function eliminates complex voltage calculations while maintaining precise control.
Solution Approach 2:
The patent replaces complex computational control with a simpler feedback-based speed adjustment mechanism. Rather than performing detailed computations to determine driving voltage, the system uses direct speed feedback and deviation analysis to adjust the target rotational speed. This substitution of complex computation with simpler feedback control reduces processing load while maintaining control precision.
Data Source
AI summary
A wiper motor control circuit carries out control in which a driving circuit generates, and supplies to a wiper motor, a voltage that eliminates deviation between a target speed and an actual speed of an output shaft. In a case in which a state in which the deviation between the target speed and the actual speed is greater than or equal to a predetermined threshold value continues for a predetermined time or more, the wiper motor control circuit carries out control that lowers the target speed and in which the driving circuit generates, and supplies to the wiper motor, a voltage that eliminates deviation between the lowered target speed and the actual speed of the output shaft.