Electric window wiper centering control method and system without centering sensing signal

Abstract

The invention discloses a centering control method and system for an electric window wiper without a centering sensing signal, and the method comprises the steps: firstly calibrating the distance S1 and time t1 when a reset disc of a wiper motor operates from a starting point to a quarter circle of the centering position, and calculating a target speed V1 = S1 / t1; after the car washing function is started, the wiper motor is controlled to run for a complete wiping period, the actual perimeter S2 and the time t2 are measured, and the actual average speed V2 = S2 / t2 is obtained. And the V2 and the V1 are compared, and the PWM duty ratio of the driving motor is dynamically adjusted, so that the V2 approaches the V1. And finally, running for time t1 at the adjusted speed from the starting point, and then stopping, so that the wiper arm is accurately stopped at the central position of the windshield. A centering sensor is not needed, accurate positioning is achieved through speed control, and system reliability and cost effectiveness are improved.

Description

Technical Field

[0001] This invention relates to the field of windshield wiper control technology, and in particular to a centering control method and system for an electric windshield wiper without a centering sensor signal. Background Technology

[0002] Rail transit vehicles are typically equipped with windshield wiper systems, mainly divided into two categories: electric wipers and pneumatic wipers. With the continuous development of electronic control and motor technologies, electric wipers have gradually become dominant in rail transit vehicles due to their high safety, stability, simple structure, and mature control principles. Among them, electric wipers using brushed motors are particularly widely used. These wipers regulate the motor's operating status in real time through an electronic control system, using PWM (Pulse Width Modulation) signals to drive MOSFETs, and adjusting the PWM duty cycle to achieve motor speed control. They offer advantages such as simple control, reliable operation, and high stability. Common functions include slow wiping, fast wiping, intermittent wiping, car washing, stopping, and spraying.

[0003] Traditionally, car wash functionality relies on a centering sensor mounted on the motor mount. When the wipers are in wash mode and the motor linkage detects the centering signal, the motor immediately stops, centered on the windshield. However, this method has significant limitations: if the centering sensor malfunctions or is not present in the system, the car wash function becomes unreliable, severely impacting the user experience.

[0004] To address the issue of car wash functionality without a centering sensor signal, various manufacturers in the industry have attempted multiple alternative methods. However, due to the potential for changes in external factors such as windshield damping force and wiper arm clamping force during actual operation, existing methods struggle to stably and accurately control the wiper arm to stop at the center position, thus affecting the functionality and user experience. Summary of the Invention

[0005] To address the above problems, this invention provides a centering control method and system for electric windshield wipers without centering sensor signals. It aims to replace physical sensors with software algorithms and speed closed-loop control to achieve precise centering of the wiper arm. This method not only effectively overcomes the interference caused by glass damping and wiper arm pressure changes, but also significantly improves the system's reliability and adaptability, while reducing hardware costs.

[0006] In a first aspect, the present invention provides a centering control method for an electric windshield wiper without a centering sensor signal, comprising: Step 1: Obtain the calibration distance S1 from the starting point to the center position of a quarter revolution of the wiper motor reset disc, and the calibration time t1 corresponding to the operation at this calibration distance S1; Step 2: Calculate and determine the target speed V1 for car wash centering control based on the calibrated distance S1 and calibrated time t1, where V1 = S1 / t1; Step 3: After the car wash function is turned on, control the wiper motor to run at the current speed for a complete wiping cycle, measure the actual circumference S2 and actual time t2 of this cycle, and calculate the actual average speed V2, where V2 = S2 / t2; Step 4: Control the actual average speed V2 to approach the target speed V1, and control the wiper motor to start from the starting point of the reset disk, run at the approaching speed for the calibrated time t1 and then stop, so that the wiper arm stops at the center position of the windshield.

[0007] Furthermore, compare the actual average speed V2 with the target speed V1, and dynamically adjust the duty cycle of the PWM signal of the drive motor according to the comparison result to make V2 approach V1.

[0008] By introducing a dynamic speed adjustment mechanism based on PWM duty cycle, it is possible to actively and real-time compensate for speed deviations caused by factors such as windshield damping changes, wiper arm pressure changes, or power supply voltage fluctuations. This enables the system to have an adaptive ability, ensuring the accuracy and stability of speed control.

[0009] Furthermore, when V2 > V1, reduce the duty cycle of the PWM signal; When V2 < V1, increase the duty cycle of the PWM signal; Among them, the adjustment amount of the duty cycle is positively correlated with the difference between V1 and V2.

[0010] The adjustment logic of the duty cycle is further refined, the relationship between the adjustment direction and the speed difference is clarified, and an adjustment amount positively correlated with the difference size is introduced, achieving fast convergence and stable control: when the speed deviation is large, a large adjustment is made to quickly approach the target speed; when the speed deviation is small, a fine adjustment is made to avoid overshoot and oscillation. This control strategy significantly improves the response speed and control accuracy of the system, can complete speed matching within a few wiping cycles, and enhances the user experience.

[0011] Furthermore, the calibrated distance S1 and calibrated time t1 are obtained from the memory of the wiper control board.

[0012] Fixing the ideal parameters of the factory calibration in the hardware provides a unified and accurate reference speed (V1) for the vehicle, ensuring the initial accuracy and consistency of the control method. This storage method also facilitates subsequent on-site debugging and parameter correction, enhances the adaptability of this method to different vehicle models and installation differences, and improves the flexibility of engineering applications.

[0013] Furthermore, the method also includes correcting the target speed V1 via software during vehicle installation and commissioning.

[0014] If a centering deviation occurs after actual installation on the vehicle, the target speed V1 can be directly corrected via software without replacing or adjusting any hardware components. This design greatly enhances the system's adaptability to different vehicle models, installation conditions, and changes in mechanical characteristics after long-term operation, improves debugging efficiency and engineering application flexibility, and ensures the persistence of centering control accuracy throughout the entire product lifecycle.

[0015] Furthermore, the reset plate is provided with an elastic contact piece, which is used to cooperate with the fixed contact when the motor is running to identify the starting point and the center position of 1 / 4 turn of the reset plate.

[0016] By utilizing the mechanical interaction between the elastic contact plates and fixed contacts on the reset plate, a low-cost, high-reliability physical position reference is provided. This structure can accurately identify the starting point and 1 / 4-turn center position of the reset plate, replacing expensive dedicated centering sensors. While simplifying the system structure, reducing hardware costs, and minimizing potential failure points, it also provides a crucial position trigger signal for the entire speed-time control algorithm.

[0017] Furthermore, the windshield is sprayed simultaneously when the car wash function is activated to reduce the impact of glass damping on the wiping speed.

[0018] By simultaneously spraying water onto the windshield when activating the car wash function, the glass surface is effectively wetted, significantly reducing the enormous frictional damping between the scraper arm rubber strip and the dry glass. This measure effectively avoids drastic fluctuations in motor load and speed instability caused by abrupt changes in the glass surface condition, creating a more stable and consistent operating condition for subsequent speed measurement and closed-loop control. This fundamentally ensures the accuracy and reliability of the center stop, improving the user experience.

[0019] Secondly, the present invention also provides a centering control system for an electric windshield wiper without a centering sensor signal. The system is used to implement the centering control method for an electric windshield wiper without a centering sensor signal, and includes a wiper motor, a reset disk, a control board and an EEPROM, wherein the control board is configured to perform the storage, speed calculation, PWM adjustment and stop control steps.

[0020] Compared with existing technologies, the advantages of this invention are: it fundamentally eliminates the reliance on dedicated centering sensors, replacing traditional physical sensors with innovative software algorithms. This not only directly reduces the hardware cost and structural complexity of the system, but also significantly improves the reliability and lifespan of the entire windshield wiper system by reducing potential failure points. By measuring the operating speed in real time and performing closed-loop feedback control with the target speed, this method can automatically compensate for speed deviations caused by uncertainties such as changes in windshield damping, wiper arm clamping force, voltage fluctuations, or mechanical wear, ensuring the accuracy and consistency of centering positioning under different operating conditions and significantly improving the user experience. After speed calibration, by controlling the motor to run precisely at the calibrated speed for a preset calibration time, time-based precise point-to-point control is achieved, enabling the wiper arm to stop stably and accurately at the expected centering position, perfectly realizing the "car wash" function. This method stores the core calibration parameters in memory, allowing the same control scheme to be easily applied to different vehicle models. Furthermore, if minor deviations occur after installation, fine-tuning can be performed through software parameter correction without changing the hardware, greatly enhancing the system's adaptability and the convenience of on-site debugging. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this drawing or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this drawing. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This invention relates to a wiper motor reset disc; Figure 3 This is a logic diagram of the target speed V1 setting process in this invention; Figure 4 This is a logic diagram of the actual average speed V2 adjustment process in this invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments provided by this invention without inventive effort are within the scope of protection of this invention.

[0024] This invention provides a centering control method for electric windshield wipers without a centering sensor signal, such as... Figure 1 Specifically, it includes the following steps: Step 1: Obtain the calibration distance S1 from the starting point to the center position of a quarter revolution of the wiper motor reset disc, and the calibration time t1 corresponding to the operation at this calibration distance S1.

[0025] Specifically, such as Figure 2 As shown, the circumference from the starting point of the wiper motor reset disc to the center position of 1 / 4 revolution is measured as S1, which is the distance the wiper motor travels from the starting point of the reset disc to the center position of 1 / 4 revolution. The value of S1 is stored in the EEPROM of the wiper control board. This value is generally consistent in the same motor and can be understood as a fixed value.

[0026] like Figure 3 As shown, during factory testing, the centering sensor on the test bench is used to identify the time it takes for the wiper motor reset disc to reach the center position at 1 / 4 revolution, which is defined as time t1. Time t1 is then stored in the EEPROM of the wiper control board.

[0027] Step two: Based on the calibration distance S1 and calibration time t1, calculate and determine the target speed V1 for car wash centering control, where V1 = S1 / t1. Car wash centering control will use speed V1 as the control target.

[0028] Step 3, as Figure 4 As shown, after the car wash function is turned on, the wiper motor is controlled to run at the current speed for a complete wiping cycle. The actual circumference S2 and the actual time t2 of this cycle are measured, and the actual average speed V2 is calculated, where V2=S2 / t2.

[0029] The wiper motor has a fixed metal reset plate inside, and the reset plate is equipped with elastic contact pieces. When the wiper motor is working, the reset plate is synchronized with the motor shaft. When the elastic contact pieces on the wiper motor reset plate move to 1 / 4 position of the reset plate, that is, when the wiper arm reaches the center position of the windshield; in order to reduce abnormal damping of the windshield, the windshield is sprayed simultaneously during the car wash mode.

[0030] Step four: Control the actual average speed V2 to approach the target speed V1, and control the wiper motor to run at the approached speed for the calibrated time t1 from the starting point of the reset disc, so that the wiper arm stops at the center position of the windshield.

[0031] The operation of the windshield wiper motor is achieved by using PWM wave to control the conduction time of the MOSFET to adjust the motor speed, thus providing a basis for real-time adjustment of the wiper speed.

[0032] Specifically, such as Figure 4As shown, the actual average speed V2 is compared with the target speed V1, and the duty cycle of the PWM signal of the drive motor is dynamically adjusted according to the comparison result, so that V2 approaches V1.

[0033] When V2 > V1, the duty cycle of the PWM signal is decreased; when V2 < V1, the duty cycle of the PWM signal is increased. The duty cycle adjustment amount is determined according to the difference between V1 and V2. Specifically, the percentage of the difference is obtained by (V2 - V1) / V1×100, and the PWM duty cycle adjustment amount is adjusted according to the percentage of the speed difference. When the percentage of the speed difference is within 1%, it is considered that V2 is equal to V1. When adjusting the PWM signal duty cycle according to the percentage of the speed difference, if the adjustment amount is too large or too small, the speed control program will automatically compensate 1% of the PWM duty cycle after detection: if the adjustment amount is too large, the duty cycle will be -1%, and if the adjustment amount is too small, the duty cycle will be +1%. The greater the speed difference, the greater the PWM duty cycle adjustment amount.

[0034] According to different working environments, after dynamically adjusting the PWM duty cycle multiple times, until the speed difference between V2 and V1 is controlled within 1%, the wiper motor starts from the starting position of the reset disk at a speed of V2, wipes for a time t1, and then immediately stops. The stop position at this time is the car wash center position.

[0035] Due to factors such as the glass state of different rail transit vehicles and the installation differences of wiper motors, there may be deviations in the car wash center position during vehicle installation and commissioning. At this time, V1 stored in the EEPROM can be corrected through software.

[0036] Specifically, the upper computer establishes communication with the wiper control box through the USB communication interface, and uses the upper computer software to correct the V1 value in the EEPROM of the wiper control box. When the wiper arm stops beyond the center position during car wash center, the V1 value is adjusted smaller; when the wiper arm stops before reaching the center position during car wash center, the V1 value is adjusted larger. The deviation size of the V1 correction can be determined according to the specific deviation situation. After the deviation value is corrected during vehicle installation, the V1 value is固化 in the EEPROM.

[0037] It should be noted that the present invention is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same composition and achieving the same effect as the technical idea within the technical solution scope of the present invention are all included in the technical scope of the present invention. In addition, within the scope not departing from the gist of the present invention, various modifications that can be想到 by those skilled in the art to the embodiments and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of the present invention.

Claims

1. A centering control method for an electric windshield wiper without a centering sensor signal, characterized in that, Comprising: Step 1: Obtain the calibration distance S1 when the wiper motor's reset disk runs from the starting point to the quarter - turn center position, and the corresponding calibration time t1 for running at this calibration distance S1; Step 2: Calculate and determine the target speed V1 for car - wash centering control according to the calibration distance S1 and calibration time t1, where V1 = S1 / t1; Step 3: After the car - wash function is enabled, control the wiper motor to run a complete wiping cycle at the current speed, measure the actual circumference S2 and actual time t2 of this cycle, and calculate the actual average speed V2, where V2 = S2 / t2; Step 4: Control the actual average speed V2 to approach the target speed V1, and control the wiper motor to start from the starting point of the reset disk, run at the approaching speed for the calibration time t1 and then stop, so that the wiper arm stops at the center position of the windshield.

2. The centering control method for an electric windshield wiper without a centering sensor signal as described in claim 1, characterized in that, The control of making the actual average speed V2 approach the target speed V1 specifically adopts the following method: Compare the actual average speed V2 with the target speed V1, and dynamically adjust the duty cycle of the PWM signal of the drive motor according to the comparison result, so that V2 approaches V1.

3. The centering control method for an electric windshield wiper without a centering sensor signal as described in claim 2, characterized in that, When V2 > V1, reduce the duty cycle of the PWM signal; When V2 < V1, increase the duty cycle of the PWM signal; Among them, the adjustment amount of the duty cycle is positively correlated with the difference between V1 and V2.

4. The centering control method for an electric windshield wiper without a centering sensor signal as described in claim 1, characterized in that, The calibration distance S1 and calibration time t1 are obtained from the memory of the wiper control board.

5. The centering control method for an electric windshield wiper without a centering sensor signal as described in claim 1, characterized in that, The method further includes correcting the target speed V1 through software during vehicle installation and debugging.

6. The centering control method for an electric windshield wiper without a centering sensor signal as described in claim 1, characterized in that, An elastic contact piece is provided on the reset disk, which is used to cooperate with the fixed contact when the motor runs to identify the starting point and the quarter - turn center position of the reset disk.

7. The centering control method for an electric windshield wiper without a centering sensor signal as described in claim 1, characterized in that, When the car - wash function is started, windshield spraying is synchronized to reduce the influence of glass damping on the wiping speed.

8. A centering control system for an electric windshield wiper without a centering sensor signal, characterized in that, The system is used to implement the control method as described in any one of claims 1 - 7, and includes a wiper motor, a reset disk, a control board, and an EEPROM, where the control board is configured to execute the steps of storage, speed calculation, PWM adjustment, and stop control.

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