Windscreen wiper software vehicle speed downshift algorithm

Abstract

The invention discloses a vehicle speed downshift algorithm for windscreen wiper software. The algorithm comprises the following steps of working condition classification, wherein a red light waiting scene and a low-speed vehicle following scene are divided through a vehicle speed signal v and an acceleration a; safety evaluation: judging the speed reduction feasibility by combining the rainfall sensor signal R and the motor current I; dynamic speed reduction: based on the working condition classification and the safety evaluation result, the wiping frequency of the windscreen wiper is adjusted according to the gradient; quit condition judgment: when a preset quit condition is met, the standard wiping frequency of the windscreen wiper is recovered immediately. By reasonably controlling the wiping frequency of the windscreen wiper, unnecessary high-frequency wiping is reduced, the abrasion of the windscreen wiper blade is reduced, and the service life is prolonged; a rainfall sensor and motor current detection are fused, the whole scene from light rain to heavy rain is covered, and the risk of fuzzy view is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile electronic control, in particular to a windshield wiper software vehicle speed downshift algorithm. Background Art

[0002] The existing speed downshift algorithm on the market reduces the wiper frequency when the vehicle speed is less than threshold A and resumes the wiper frequency when the vehicle speed is greater than threshold B, without detailed judgment of the user's working conditions. For example, using the same speed reduction strategy in different low-speed scenarios such as following a car or waiting at a red light can easily lead to scene misjudgment and fail to accurately meet user needs. The existing rain recognition on the market is all based on rain sensors. However, rain sensors are sensitive to light, emitting infrared light and detecting infrared light reflected by the glass. They determine the amount of rain by identifying changes in the intensity of the reflected light and signal fluctuations. In light rain or dim scenes, the judgment is inaccurate. For example, dim external light, strong light, glass stains, wax-containing glass cleaners, etc. can interfere with its detection results, resulting in insufficient field of view and affecting driving safety.

[0003] Based on this, existing wiper speed reduction algorithms rely solely on a speed threshold (e.g., speed reduction when the vehicle speed is less than 15 km / h). These algorithms fail to distinguish between "waiting at a red light" (stationary) and "low-speed following" (slowly moving). This can lead to excessive speed reduction and blurred vision when following a vehicle. Furthermore, their sole reliance on the rain sensor results in low detection accuracy in light rain (due to interference from light and glass stains), posing the risk of dry wipes. Therefore, we propose a software-based speed reduction algorithm for wipers. Summary of the Invention

[0004] The purpose of the present invention is to provide a wiper software vehicle speed downshift algorithm to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a wiper software speed downshift algorithm, comprising the following steps:

[0006] Working condition classification: The vehicle speed signal v and acceleration a are used to classify the red light scenario and the low-speed following scenario;

[0007] Safety assessment: Determine the feasibility of speed reduction by combining the rain sensor signal R and the motor current I;

[0008] Dynamic deceleration: Based on the operating condition classification and safety assessment results, the wiper frequency is adjusted in a gradient manner;

[0009] Exit condition judgment: When the preset exit condition is met, the standard wiper frequency will be restored immediately.

[0010] Preferably, in the operating condition classification, the vehicle speed signal v is obtained through LIN communication between the body control module BCM and the wiper, and the acceleration a is obtained by taking the second-order derivative of the vehicle speed signal.

[0011] Preferably, the determination condition for the red light waiting scenario is: timing starts when the vehicle speed changes from non-zero to 0 km / h for the first time, and when the time t for which the vehicle speed remains zero reaches 5 seconds.

[0012] Preferably, the judgment conditions for the low-speed following scene are: vehicle speed 0<v≤12km / h and acceleration |a|<0.5m / s 2 .

[0013] Preferably, in the safety assessment, the detection principle of the rain sensor signal R is: emitting infrared light and detecting the infrared light reflected by the glass, and judging the amount of rainfall by identifying the change in the reflected light intensity and the signal fluctuation; the detection accuracy is divided into 4-8 levels, and speed reduction is allowed when R≤2mm / h.

[0014] Preferably, the motor current I is collected in a method as follows: a sampling resistor r is connected in series to the motor MOS output terminal, a chip collects voltages v1 and v2 across the resistor, and the current is calculated by I=(v1-v2) / r.

[0015] Preferably, the standard scraping frequency is set by the shift position of the lever switch, including 40 rpm for the first gear and 60 rpm for the second gear.

[0016] Preferably, in the dynamic deceleration, the scraping frequency is reduced to 50% of the standard value in the red light waiting scenario, and is reduced to 70% of the standard value in the low-speed following scenario; the deceleration method includes direct deceleration or linear deceleration.

[0017] Preferably, the exit conditions include: when any one of the vehicle speed v>12km / h, the rain sensor signal R>2mm / h, and the average current is lower than 5A is met, the standard frequency is immediately restored.

[0018] Compared with the prior art, the beneficial effects of the present invention are: the wiper software speed downshift algorithm has a simple and reasonable structural design and has the following advantages:

[0019] Precise noise reduction: noise is reduced when waiting at red lights, improving driving comfort;

[0020] Extended service life: By reasonably controlling the wiper wiping frequency and reducing unnecessary high-frequency wiping, the wiper blade wear is reduced and the service life is extended;

[0021] Double safety: Integrating a rain sensor with motor current detection, it covers all scenarios from light rain to heavy rain, avoiding the risk of blurred vision.

[0022] Scenario Adaptation: Dynamically distinguishes between waiting at a red light and following a vehicle at low speed, with a low misjudgment rate. This solves the defect of the traditional algorithm's "one-size-fits-all" frequency reduction. When users are following a vehicle at low speed or waiting to change lanes, the wipers can reasonably adjust the wiping frequency according to the actual scenario, ensuring a clear field of view and improving the driving experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the working condition identification process of the present invention. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] Example:

[0026] See also Figure 1 The present invention provides a technical solution: a wiper software speed downshift algorithm, comprising the following steps:

[0027] Working condition classification: The vehicle speed signal v and acceleration a are used to classify the red light scenario and the low-speed following scenario;

[0028] Safety assessment: Determine the feasibility of speed reduction by combining the rain sensor signal R and the motor current I;

[0029] Dynamic deceleration: Based on the operating condition classification and safety assessment results, the wiper frequency is adjusted in a gradient manner;

[0030] Exit condition judgment: When the preset exit condition is met, the standard wiper frequency will be restored immediately.

[0031] Condition Classification: Vehicle speed and acceleration data are collected in real time through onboard sensors to construct a vehicle motion model. Unlike traditional classification methods that rely solely on speed thresholds, this step uses the absolute value of vehicle speed (0 or low speed) and the rate of change of acceleration (reflecting the magnitude of acceleration and deceleration) to accurately distinguish between two typical low-dynamic conditions: "waiting for a red light" (completely stationary for a certain period of time) and "low-speed following" (slow and steady driving). This addresses the problem of misjudgment in existing scenarios.

[0032] Safety Assessment: A dual field-of-view safety verification mechanism integrates the optical detection of the rain sensor and the resistance feedback of the wiper motor current. The rain sensor directly detects the amount of water on the glass surface, while the motor current indirectly reflects the contact resistance between the wiper and the glass (less water, greater frictional resistance, and higher current). These two complementary mechanisms cover all blind spots in light to heavy rain, ensuring uncompromised visibility during deceleration.

[0033] Dynamic Speed Reduction: Based on the operating condition classification (waiting at a red light / following a vehicle at low speed) and safety assessment conclusions (light rain, no risk of dry scraping), the wiper frequency is reduced by a preset gradient (50% / 70%). This gradient design balances noise reduction with visual safety, avoiding the safety hazards associated with a "one-size-fits-all" speed reduction.

[0034] Exit Condition Judgment: Set multiple exit trigger conditions (vehicle speed, rainfall, current). If any of these conditions are met, the standard frequency is restored, ensuring real-time system response. Unlike traditional conservative designs that require all conditions to be met simultaneously, this solution prioritizes field of view safety through "OR" logic, avoiding response delays caused by delayed combinations of conditions.

[0035] Preferably, in the operating condition classification, the vehicle speed signal v is obtained through LIN communication between the body control module BCM and the wiper, and the acceleration a is obtained by taking the second-order derivative of the vehicle speed signal.

[0036] Vehicle speed signal acquisition: LIN bus communication is used to enable low-speed data exchange between the wiper controller and the BCM, ensuring real-time speed signal delivery (communication cycle ≤ 10ms) and reliability (the bus protocol includes built-in error checking). Unlike directly collecting wheel speed sensor signals, the BCM-integrated vehicle speed signal incorporates data from multiple sensors (such as ABS and ESP), resulting in higher accuracy (error ≤ 0.5 km / h).

[0037] Acceleration calculation: The vehicle longitudinal acceleration is indirectly obtained by performing a second-order differential (numerical differentiation) on the discrete vehicle speed signal. This method does not require additional hardware sensors, reducing costs, and suppresses noise through software filtering (such as sliding average), ensuring that acceleration fluctuations are ≤0.1m / s. 2 It is judged as "stable driving".

[0038] Preferably, the determination condition for the red light waiting scenario is: timing starts when the vehicle speed changes from non-zero to 0 km / h for the first time, and when the time t for which the vehicle speed remains zero reaches 5 seconds.

[0039] A timer trigger mechanism monitors vehicle speed changes through a state machine, starting the timer only when the vehicle's speed jumps from a non-zero value (>0 km / h) to zero for the first time. This prevents misjudgment of temporary stops (such as a sudden stop caused by a preceding vehicle braking). For example, if a vehicle temporarily stops but then restarts within two seconds, the red light mode will not be triggered, ensuring robust scene recognition.

[0040] 5-second threshold setting: Based on traffic scenario statistics, the average waiting time for red lights at urban intersections is ≥30 seconds. 5 seconds as the judgment threshold can effectively filter out short-term static scenes (usually <5 seconds) such as "temporary parking for lane change" and "briefly giving way to pedestrians", reducing the number of false downtimes (false judgment rate <5%).

[0041] Preferably, the judgment conditions for the low-speed following scene are: vehicle speed 0<v≤12km / h and acceleration |a|<0.5m / s 2 .

[0042] A speed threshold of 12 km / h corresponds to the typical low-speed range for following vehicles in congested urban traffic (15 km / h below the typical creeping speed), preventing misjudgment of high-speed driving (e.g., in low-speed lanes on roundabouts). This threshold can be fine-tuned through vehicle calibration to adapt to the acceleration performance of different models.

[0043] Acceleration threshold 0.5m / s 2 : reflects the vehicle is in a "slow acceleration / slow deceleration" state (such as smooth acceleration and deceleration when following a car in congestion), excluding frequent start-stop scenarios (such as complex road conditions with frequent congestion, when |a|>0.5m / s 2 The combined judgment of the two ensures that the speed reduction is triggered only during "low and steady" following, avoiding incorrect speed reduction during sudden acceleration / deceleration due to high vision requirements.

[0044] Preferably, in the safety assessment, the detection principle of the rain sensor signal R is: emitting infrared light and detecting the infrared light reflected by the glass, and judging the amount of rainfall by identifying the change in the reflected light intensity and the signal fluctuation; the detection accuracy is divided into 4-8 levels, and speed reduction is allowed when R≤2mm / h.

[0045] Detection principle details: A rain sensor (typically integrated inside the windshield) emits infrared light onto the glass surface. When there's no rain, most of the light is reflected back to the receiver by the glass (refractive index 1.52). During rainfall, water droplets change the glass's refractive index, causing the intensity of the reflected light to decrease as the amount of water increases. A / D conversion quantifies the light intensity signal into a rainfall level (e.g., Level 0: no rain, Levels 1-3: light rain, Levels 4-6: moderate rain, and Levels 7-8: heavy rain). R ≤ 2 mm / h corresponds to Levels 1-2: light rain or no rain.

[0046] The speed reduction threshold is 2mm / h, the dividing line between "light rain" and "moderate rain" in international standards (ISO4513). At this level, the rain has minimal impact on visibility, and a low wiper speed is sufficient to maintain clear vision. Above this threshold (e.g., moderate rain or above), speed reduction may cause rainwater to accumulate, so speed reduction is prohibited.

[0047] Preferably, the method for collecting the motor current I is: a sampling resistor r is connected in series at the motor MOS output end, the chip collects the voltages v1 and v2 at both ends of the resistor, and the current is calculated by I = (v1-v2) / r; when the average current I>8A, it is determined that the amount of glass water is very small and the speed reduction is allowed.

[0048] Current acquisition circuit: Low-temperature drift alloy resistors (accuracy ±0.1%, temperature coefficient ≤50ppm / °C) are used as sampling resistors to ensure a current measurement error of ≤0.2A within the -40°C to 85°C temperature range. A chip (such as an STM32 ADC module) synchronously samples the voltage difference at a 100Hz frequency and calculates the average current using a sliding average filter (window length 100ms) to suppress high-frequency noise caused by the PWM drive.

[0049] 8A Current Threshold: This value is the "dry-wiping critical current," determined through vehicle calibration testing (different models vary in dry-wiping current range from 7-10A due to differences in wiper blade material and glass curvature). When I > 8A, it indicates insufficient water between the wiper and the glass (possibly due to light rain or dry glass). In this case, reducing the frequency will not cause dry-wiping noise. Conversely, if I < 5A (sufficient water, low resistance), high-frequency wipers should be restored.

[0050] Furthermore, the above current threshold is confirmed based on actual vehicle calibration, and the light rain current of different vehicles is different.

[0051] Preferably, the standard scraping frequency is set by the shift position of the lever switch, including 40 rpm for the first gear and 60 rpm for the second gear.

[0052] Human-Machine Interaction Basics: The standard frequency is manually selected by the user via the wiper stalk (e.g., INT intermittent, LO low speed, HI high speed). "First gear" (40 rpm) corresponds to LO (low-speed continuous wiping), and "Second gear" (60 rpm) corresponds to HI (high-speed continuous wiping), in compliance with the SAE J903 standard. This frequency is factory-set to ensure compatibility with traditional wiper functions. The frequency reduction strategy only takes effect temporarily when operating conditions are met and does not change user operation logic.

[0053] Preferably, in the dynamic deceleration, the scraping frequency is reduced to 50% of the standard value in the red light waiting scenario, and is reduced to 70% of the standard value in the low-speed following scenario; the deceleration method includes direct deceleration or linear deceleration.

[0054] Gradient frequency reduction is based on the following: When waiting at a red light (vehicle stationary), rainwater accumulates slowly, and a 50% frequency reduction (e.g., 60rpm→30rpm) can reduce wiper noise by 6-10dB, while avoiding rainwater retention caused by low frequency. In low-speed following scenarios (vehicle speed ≤12km / h), the airflow generated by the relative motion of the vehicles helps to separate rainwater, and a 70% frequency reduction (e.g., 60rpm→42rpm) can reduce noise while ensuring that the wiper frequency is ≥25rpm (the minimum frequency for clear vision acceptable to the human eye).

[0055] Speed reduction mode selection: Direct speed reduction is suitable for noise-sensitive scenarios (such as waiting for a red light while stationary), with a response time of less than 200ms; linear speed reduction (such as reducing the speed by 4rpm every 500ms) is suitable for following a vehicle, avoiding mechanical shock to the wiper caused by frequency mutations and extending the life of the transmission mechanism (gears, swing arms, etc.).

[0056] Preferably, the exit conditions include: when any one of the vehicle speed v>12km / h, the rain sensor signal R>2mm / h, and the average current is lower than 5A is met, the standard frequency is immediately restored.

[0057] Multi-condition "OR logic": any condition is triggered to restore the standard frequency, reflecting the "safety first" principle:

[0058] v>12km / h: The vehicle enters normal driving state and requires high-frequency scraping to deal with possible splashing water (such as road water caused by the vehicle ahead);

[0059] R>2mm / h: Rainfall increases to moderate rain level, and high-frequency scraping is necessary for safety;

[0060] I<5A: The decrease in current indicates that there is sufficient water (small resistance). At this time, frequency reduction may cause untimely scraping and brushing, and the standard frequency needs to be restored.

[0061] Response mechanism: The exit condition monitoring period is 100ms, ensuring that the total delay from condition satisfaction to frequency recovery is less than 300ms, which is better than the industry standard (conventional wiper response delay ≥500ms).

[0062] This wiper software speed downshift algorithm achieves intelligent adjustment of wiper frequency through a closed-loop control logic of "data collection → operating condition identification → safety verification → strategy execution → real-time monitoring". The specific working principle is as follows:

[0063] 1. Data Collection Layer

[0064] Vehicle speed and acceleration: The wiper controller obtains the real-time vehicle speed v (accuracy ±0.5km / h, update frequency 100Hz) from the BCM via the LIN bus, and calculates the acceleration a (reflecting the acceleration and deceleration amplitude of the vehicle, with filtered noise ≤0.1m / s) using a second-order difference algorithm. 2 ).

[0065] Rainfall signal: The rain sensor emits infrared light, receives the light intensity reflected by the glass and converts it into rainfall level R (resolution 0.5mm / h, detection range 0-20mm / h), which is output every 200ms.

[0066] Motor current: A sampling resistor (r = 0.1Ω) is connected in series with the motor drive circuit. The ADC collects the voltage difference and calculates the current I (accuracy ±0.3A). The 1-second average current I is also calculated (after filtering out PWM high-frequency noise).

[0067] 2. Working condition identification layer

[0068] Red light waiting judgment: When v jumps from > 0 to 0 km / h for the first time, a 5-second timer is started. If v remains 0 during this period, it is judged as a red light waiting scenario (filtering short-term stops).

[0069] Low-speed following judgment: When 0<v≤12km / h and |a|<0.5m / s 2 (lasting more than 1 second), it is judged as a low-speed following scenario (distinguishing between smooth following and frequent starts and stops).

[0070] 3. Security Verification Layer

[0071] Rainfall verification: If R≤2mm / h (light rain or no rain), it indicates that the current rainfall does not affect the field of view and frequency reduction is allowed; if R>2mm / h, frequency reduction is forcibly prohibited.

[0072] Current verification: If I>8A (small amount of water, large resistance), it indicates that there is no risk of dry scraping and the frequency can be reduced; if I<5A (sufficient water, small resistance), high-frequency scraping needs to be maintained.

[0073] 4. Strategy execution layer

[0074] Red light mode: When safety conditions are met, the scraping frequency is reduced to 50% of the standard value (e.g. 60rpm→30rpm), reducing mechanical noise in a stationary state.

[0075] Low-speed following mode: When safety conditions are met, the wiper frequency is reduced to 70% of the standard value (e.g. 60rpm → 42rpm), balancing noise reduction and visibility requirements during low-speed driving.

[0076] Speed reduction mode: supports direct speed reduction (immediate frequency switching, fast response) or linear speed reduction (gradient adjustment, small mechanical impact), which is selected by vehicle calibration.

[0077] 5. Real-time monitoring and exit

[0078] The system monitors exit conditions (v>12km / h, R>2mm / h, I<5A) in a 100ms cycle. When any of the conditions is triggered, the standard frequency is restored within 0.3 seconds to ensure that the wipers work at a timely and high frequency when the vehicle speed increases, the rainfall increases, or there is sufficient water, thereby ensuring driving safety.

[0079] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A wiper software speed downshift algorithm, characterized by: The following steps are involved: Working condition classification: The vehicle speed signal v and acceleration a are used to classify the red light scenario and the low-speed following scenario; Safety assessment: Determine the feasibility of speed reduction by combining the rain sensor signal R and the motor current I; Dynamic deceleration: Based on the operating condition classification and safety assessment results, the wiper frequency is adjusted in a gradient manner; Exit condition judgment: When the preset exit condition is met, the standard wiper frequency will be restored immediately.

2. The wiper software speed downshift algorithm according to claim 1, characterized in that: In the operating condition classification, the vehicle speed signal v is obtained through LIN communication between the body control module BCM and the wiper, and the acceleration a is obtained by taking the second-order derivative of the vehicle speed signal.

3. The wiper software speed downshift algorithm according to claim 1, characterized in that: The judgment condition for the red light waiting scene is: the timing starts when the vehicle speed changes from non-zero to 0 km / h for the first time, and the time t when the vehicle speed continues to be 0 reaches 5 seconds.

4. The wiper software speed downshift algorithm according to claim 1, characterized in that: The judgment conditions for the low-speed following scenario are: vehicle speed 0<v≤12km / h and acceleration |a|<0.5m / s 2 .

5. The wiper software speed downshift algorithm according to claim 1, characterized in that: In the safety assessment, the detection principle of the rain sensor signal R is to emit infrared light and detect the infrared light reflected by the glass, and determine the amount of rainfall by identifying the changes in the reflected light intensity and signal fluctuations. The detection accuracy is divided into 4-8 levels, and the speed reduction is allowed when R ≤ 2mm / h.

6. The wiper software speed downshift algorithm according to claim 1, characterized in that: The motor current I is collected in a method as follows: a sampling resistor R is connected in series to the motor MOS output terminal, a chip collects voltages V1 and V2 across the resistor, and the current is calculated by I=(V1-V2) / R.

7. The wiper software speed downshift algorithm according to claim 1, characterized in that: The standard scraping frequency is set by the shift lever, including 40 rpm in the first gear and 60 rpm in the second gear.

8. The wiper software speed downshift algorithm according to claim 1, characterized in that: In the dynamic deceleration, the scraping frequency is reduced to 50% of the standard value in the red light waiting scenario and to 70% of the standard value in the low-speed following scenario; the deceleration method includes direct deceleration or linear deceleration.

9. The wiper software speed downshift algorithm according to claim 1, characterized in that: The exit conditions include: vehicle speed v>12km / h, rain sensor signal R>2mm / h, average current lower than 5A. When any one of the conditions is met, the standard frequency is immediately restored.

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