A method and system for estimating automobile tire load

Abstract

This invention relates to the field of automotive electronics technology, specifically to a method and system for estimating automotive tire load. This invention utilizes a tire module and a central module to estimate the tire load. The tire module extracts tire contact characteristics and contact cycle signals and sends them to the central module inside the vehicle. When the vehicle is traveling at a constant speed in a straight line, the tire load is estimated using the tire pressure, contact characteristics, and contact cycle received from the tire module. This invention comprehensively considers the changes in radial and longitudinal acceleration during tire rotation, extracts tire contact characteristics and contact cycle signals, and estimates the tire load by weighting a linear function, cross term, and quadratic function of tire contact characteristics, tire contact cycle, tire pressure, and tire wear information. This fully utilizes information from tire pressure, contact characteristics, contact cycle, and wear, resulting in more accurate estimation results, easier parameter identification, a simpler estimation process, and better adaptability.

Description

Technical Field

[0001] This invention relates to the field of automotive electronics technology, and more specifically to a method and system for estimating automotive tire load. Background Technology

[0002] Car tires are the only part of a car that contacts the ground; the car's driving force, braking force, and steering force all function through the tires. Tire load is a crucial tire parameter that directly affects the forces acting on the tire. By obtaining tire load information, engine control can be optimized to improve fuel economy, and tire braking force distribution can be optimized to enhance driving safety and comfort.

[0003] Directly measuring tire load is quite difficult. Currently, tire load changes are generally estimated using measurement information from acceleration sensors installed inside the tire. Patent application number 200380110584.8, published on November 8, 2006, entitled "Method and System for Detecting Tire Load During Vehicle Operation," uses the distance between two peaks of the radial acceleration signal during one rotation of the tire to represent the tire contact length, and estimates load changes using the tangent function or a first-half power function of the contact length.

[0004] In this estimation method, the ground contact length is represented by the distance between the peak values ​​of radial acceleration, which introduces a certain degree of error. Furthermore, it does not consider changes in tire pressure, speed, and wear. Patent application number 202010733445.6, published on November 24, 2020, entitled "A Real-Time Tire Load Identification Device and Method," considers the influence of tire pressure and speed, estimating the load using a nonlinear function of tire ground contact length, speed, and pressure. However, the ground contact length is still represented by the distance between the peak values ​​of radial acceleration, which introduces a certain degree of error. Additionally, the functional relationship is relatively complex, making accurate parameter identification difficult and affecting the estimation accuracy. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned shortcomings in the prior art by providing a method and system for estimating vehicle tire load. This method fully utilizes measurement information from radial acceleration sensors, longitudinal acceleration sensors, and pressure sensors installed inside the tire, considers the influence of tire pressure, speed, and wear, and estimates tire load changes through a simple function. This reduces the difficulty of parameter identification and improves the accuracy and adaptability of vehicle tire load estimation.

[0006] The objective of this invention is achieved through the following technical solution: a method for estimating vehicle tire load, comprising a tire module mounted on the vehicle tire and a central module mounted inside the vehicle; comprising the following steps:

[0007] S1. After the central module determines that the car has started, the central module inside the car sends a wake-up command to the tire module to wake up the tire module.

[0008] S2. The tire module measures the tire's pressure, temperature, longitudinal acceleration, and radial acceleration, processes and judges the measurement signals, and extracts the tire's grounding characteristics and grounding cycle information after removing interference noise through smoothing filtering.

[0009] S3. The central module receives the vehicle's speed, acceleration, and steering angle information via the CAN bus, and receives the tire pressure, temperature, grounding characteristics, and grounding cycle information sent by the tire module wirelessly. Based on the vehicle's speed, acceleration, and steering angle information, the module determines the vehicle's driving status. If the vehicle is driving in a straight line at a constant speed, proceed to step S4; otherwise, return to step S2.

[0010] S4. The central module uses the received tire pressure, temperature, grounding characteristics and grounding cycle information to estimate the tire load. Based on the tire load estimate, tire pressure and tire temperature, the central module makes a tire safety judgment. If the tire is safe, the central module displays the tire pressure, temperature, tire load and safety status on the LCD screen, and then returns to step S2; otherwise, it proceeds to step S5.

[0011] S5. The central module sends an alarm message to the alarm display device, displaying the tire pressure, temperature, tire load, and safety status information to remind the driver to pay attention and take timely action. After the action is completed, the alarm message disappears, the tire danger is eliminated, and the process returns to step S2.

[0012] In step S2, the tire module uses the measured longitudinal and radial accelerations to extract the tire's ground contact characteristics and ground contact cycle information.

[0013] The tire's ground contact characteristics consist of part or all of the peak ground contact time, mean ground contact time, left width, left height, left area, right width, right height, right area, valley height, and depression area extracted from the measured radial acceleration, as well as the maximum, minimum, width, and area extracted from the measured longitudinal acceleration.

[0014] The peak ground time of the radial acceleration is the distance between two consecutive peak values ​​of the radial acceleration within one cycle;

[0015] The mean grounding time of the radial acceleration is the first mean point extracted after the first peak is reached within a cycle, and the second mean point is extracted after the first mean point and before the second peak. The distance between the first and second mean points is the mean grounding time.

[0016] The left width of the radial acceleration is the distance between the first mean point and the first peak point;

[0017] The left height of the radial acceleration is the difference between the amplitude of the radial acceleration at the first peak position and the amplitude of the radial acceleration at the first mean point position;

[0018] The left area of ​​the radial acceleration is the sum of the differences between the amplitude of the radial acceleration and the amplitude of the mean radial acceleration between the first peak point and the first mean point;

[0019] The right width of the radial acceleration is the distance between the second mean point and the second peak point;

[0020] The right height of the radial acceleration is the difference between the amplitude of the radial acceleration at the second peak position and the amplitude of the radial acceleration at the second mean point position;

[0021] The right area of ​​the radial acceleration is the sum of the differences between the radial acceleration amplitude and the radial acceleration mean amplitude between the second mean point and the second peak point;

[0022] The valley height of the radial acceleration is the difference between the amplitude of the radial acceleration at the lowest point between the first and second mean points and the amplitude of the mean radial acceleration.

[0023] The area of ​​the radial acceleration depression is the sum of the differences between the radial acceleration amplitude and the mean radial acceleration amplitude between the first and second mean points.

[0024] The mean value of the radial acceleration is obtained by averaging the radial acceleration signals collected continuously for at least one cycle;

[0025] The maximum value of the longitudinal acceleration is the difference between the amplitude of the longitudinal acceleration at the maximum value position within one cycle and the amplitude of the mean longitudinal acceleration.

[0026] The minimum value of the longitudinal acceleration is the difference between the amplitude of the longitudinal acceleration at the minimum position within one cycle and the amplitude of the mean longitudinal acceleration.

[0027] The width of the longitudinal acceleration is the distance between the maximum and minimum values ​​of the longitudinal acceleration;

[0028] The area of ​​the longitudinal acceleration is the sum of the difference between the amplitude of the longitudinal acceleration between the maximum and minimum points and the amplitude of the longitudinal acceleration at the minimum point.

[0029] The mean value of the longitudinal acceleration is obtained by averaging the longitudinal acceleration signals collected for at least one cycle;

[0030] The grounding cycle information is the distance between two minimum values ​​of tire radial acceleration detected over two consecutive cycles.

[0031] The present invention is further configured such that the grounding characteristic is a weighted sum of different characteristics of radial acceleration and longitudinal acceleration:

[0032]

[0033] In the formula, F represents the grounding characteristic, and f k To differentiate between radial and longitudinal acceleration characteristics, selections can be made from: radial acceleration peak ground time, radial acceleration mean ground time, radial acceleration left width, radial acceleration left height, radial acceleration left area, radial acceleration right width, radial acceleration right height, radial acceleration right area, radial acceleration valley height, radial acceleration depression area, longitudinal acceleration maximum, longitudinal acceleration minimum, longitudinal acceleration width, and longitudinal acceleration area. k For the selected radial and longitudinal acceleration characteristics f k The corresponding weighting coefficients are obtained through experimental testing based on the correlation between different features and tire load, where m is the number of selected radial and longitudinal acceleration features.

[0034] The present invention is further configured such that the tire contact feature is a weighted sum of different feature transformations of radial acceleration and longitudinal acceleration:

[0035]

[0036] In the formula, F represents the grounding characteristic. The results of different characteristic transformations of radial and longitudinal acceleration can be selected from the following: radial acceleration peak ground time / ground period information, radial acceleration mean ground time / ground period information, radial acceleration left width / ground period information, radial acceleration left height * ground period information, radial acceleration left area * ground period information, radial acceleration right width / ground period information, radial acceleration right height * ground period information, radial acceleration right area * ground period information, radial acceleration valley height * ground period information, radial acceleration depression area * ground period information, longitudinal acceleration maximum * ground period information, longitudinal acceleration minimum * ground period information, longitudinal acceleration width / ground period information, and longitudinal acceleration area * ground period information. l The selected radial and longitudinal acceleration characteristic transformation results The corresponding weighting coefficients were obtained through experimental testing based on the correlation between different feature transformation results and tire load. The number of selected radial and longitudinal acceleration characteristic transformation results.

[0037] The present invention is further configured such that the central module estimates the tire load by performing a combination of linear functions, cross terms, and quadratic functions based on the received tire pressure, ground contact characteristics, and ground contact cycle information:

[0038]

[0039] In the formula, Fz is the tire load, x1 is the tire pressure, x2 is the reciprocal of the tire contact cycle information, x3 is the tire contact characteristics, and p1, p2, p3, p4, p5, p6, p7, p8, p9, p 10 These are parameters related to tire structure and wear.

[0040] The present invention is further configured such that, when performing tire load estimation, the estimated parameter p i There is a nonlinear relationship between (i = 1-10) and the degree of wear w. Parameter a ij This can be identified based on experimental test data of tires with different wear levels.

[0041] A vehicle tire load estimation system includes a tire module installed on a vehicle tire and a central module installed inside the vehicle; the tire module and the central module are wirelessly connected.

[0042] The tire module can receive a wake-up signal sent by the central module. After being woken up, the tire module measures the tire pressure, temperature, longitudinal acceleration and radial acceleration, performs data processing and judgment of the measurement information, extracts the tire's ground contact characteristics and ground contact cycle information, and transmits the acquired tire pressure, temperature, ground contact characteristics and ground contact cycle information to the central module wirelessly.

[0043] The central module receives information from the tire module. The central module receives the vehicle's speed, acceleration, and steering angle information via the CAN bus. Based on the received information, it determines whether the vehicle is traveling at a constant speed in a straight line. When the vehicle is traveling at a constant speed in a straight line, the central module uses the tire pressure, ground contact characteristics, and ground contact cycle information sent by the tire module to estimate the tire load.

[0044] The present invention is further configured such that the tire module is attached to the center line of the inner wall of the automobile tire;

[0045] The tire module includes a tire pressure sensor, a tire temperature sensor, a tire acceleration sensor, a first microcontroller, a memory, a battery, a wake-up circuit, a radio frequency transceiver, and an antenna.

[0046] The tire pressure sensor measures tire pressure changes, the tire temperature sensor measures tire temperature changes, and the tire acceleration sensor measures tire longitudinal and radial acceleration changes.

[0047] The memory stores tire pressure sensor measurement information, tire temperature sensor measurement information, tire acceleration sensor measurement information, tire measurement information processing and judgment program, tire contact feature extraction program, and tire contact cycle extraction program;

[0048] The radio frequency transceiver receives the wake-up pulse transmitted by the central module and sends information on tire pressure, temperature, grounding characteristics, and grounding cycle.

[0049] The battery is connected to the first microcontroller, and the wake-up circuit is connected to the first microcontroller. The wake-up circuit generates a wake-up signal under the action of the wake-up pulse sent by the central module to wake up the first microcontroller. The antenna is connected to the radio frequency transceiver.

[0050] Tire pressure sensor, tire temperature sensor, tire acceleration sensor, RF transceiver, and memory are connected to the input / output interface of the first microcontroller. Information received by the RF transceiver, information stored in the memory, tire pressure measured by the tire pressure sensor, tire temperature measured by the tire temperature sensor, and radial and longitudinal acceleration measured by the tire acceleration sensor are sent to the first microcontroller through its input / output ports. The first microcontroller processes and judges the sensor measurement information, extracts tire ground contact characteristics and ground contact period, sends storage or retrieval commands to the memory through its input / output ports to store or retrieve information, sends receive or transmit commands to the RF transceiver to control its receiving or transmitting operation, and sends measurement and read commands to the tire pressure sensor, tire temperature sensor, and tire acceleration sensor to measure and read the tire status.

[0051] The present invention is further configured such that the central module is installed in the driver's cab of a car, and the central module includes a keypad, a second microcontroller, a memory, a display alarm device, a power supply, a CAN transceiver, a radio frequency transceiver, and an antenna;

[0052] The keypad is used for human-computer interaction. The memory stores tire pressure measurement information, tire temperature measurement information, tire ground contact characteristic information, tire ground contact cycle information, tire load estimation program and estimation results, tire safety status judgment program, tire safety status judgment results, vehicle driving status judgment program and vehicle driving status judgment results.

[0053] The display and alarm device displays the tire pressure, temperature, load, and safety status, and issues an alarm message when the tire condition is abnormal.

[0054] The CAN transceiver receives information about the vehicle's speed, acceleration, and steering angle.

[0055] The radio frequency transceiver receives tire pressure, temperature, grounding characteristics and grounding cycle information transmitted by the tire module, and transmits a low-frequency wake-up pulse signal;

[0056] The power supply is connected to the second microcontroller, and the antenna is connected to the RF transceiver. The keypad, memory, display alarm device, CAN transceiver, and RF transceiver are respectively connected to the input / output interface of the second microcontroller. Information input from the keypad, information stored in the memory, information received by the CAN transceiver, and information received by the RF transceiver are all sent to the second microcontroller through its input / output ports. The second microcontroller sends storage or retrieval commands to the memory through its input / output ports to access information. The second microcontroller sequentially executes the vehicle driving status judgment program, the tire load estimation program, and the tire safety status judgment program. Based on the estimation and judgment results, the second microcontroller sends a command and content to the display alarm device to display the alarm. The second microcontroller sends receive or transmit commands to the CAN transceiver to control the reception or transmission of CAN bus signals. The second microcontroller sends receive or transmit commands to the RF transceiver to control the RF transceiver's reception or transmission status.

[0057] The beneficial effects of this invention are as follows: This invention utilizes sensors installed inside the tire to detect tire pressure, temperature, longitudinal acceleration, and radial acceleration. By comprehensively considering the changes in radial and longitudinal acceleration during tire rotation, it extracts tire contact patch characteristics and contact patch cycle signals. The tire load is estimated by weighting a linear function, cross term, and quadratic function of tire contact patch characteristics, tire contact patch cycle, tire pressure, and tire wear information. This estimation method fully utilizes information from tire pressure, contact patch characteristics, contact patch cycle, and wear level, resulting in more accurate estimation results, easier parameter identification, a simpler estimation process, and better adaptability. Attached Figure Description

[0058] The invention will be further illustrated with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the invention. For those skilled in the art, other drawings can be obtained based on the following drawings without any creative effort.

[0059] Figure 1 This is a flowchart of the vehicle tire load estimation method of the present invention;

[0060] Figure 2 This is a schematic diagram illustrating the extraction of the tire radial acceleration ground contact feature of the present invention;

[0061] Figure 3 This is a schematic diagram illustrating the extraction of the longitudinal acceleration ground contact feature of the tire according to the present invention;

[0062] Figure 4This is a schematic diagram illustrating the extraction of tire radial acceleration ground contact cycle characteristics according to the present invention;

[0063] Figure 5 This is a schematic diagram comparing the estimated tire load value with the actual value of the present invention;

[0064] Figure 6 It is the ratio of the deviation of the tire load estimation result of this invention to the actual load;

[0065] Figure 7 This is a schematic diagram of the structure of the automobile tire load estimation system of the present invention;

[0066] Figure 8 This is a schematic diagram of the tire module of the automobile tire load estimation system of the present invention;

[0067] Figure 9 This is a schematic diagram of the central module of the vehicle tire load estimation system of the present invention. Detailed Implementation

[0068] The present invention will be further described in conjunction with the following embodiments.

[0069] Depend on Figure 1 As can be seen, the vehicle tire load estimation method described in this embodiment involves a central module inside the vehicle wirelessly receiving tire pressure, temperature, ground contact characteristics, and ground contact cycle information sent by the tire module. It also receives the vehicle's speed, acceleration, and steering angle information via the CAN bus to determine whether the vehicle is traveling at a constant speed in a straight line. When the vehicle is traveling at a constant speed in a straight line, the tire load is estimated using the tire pressure, ground contact characteristics, and ground contact cycle received from the tire module, including the following steps:

[0070] S1. After the central module determines that the car has started, the central module inside the car sends a wake-up command to the tire module to wake up the tire module.

[0071] S2. The tire module measures the tire's pressure, temperature, longitudinal acceleration, and radial acceleration, processes and judges the measurement signals, and extracts the tire's grounding characteristics and grounding cycle information after removing interference noise through smoothing filtering.

[0072] S3. The central module receives the vehicle's speed, acceleration, and steering angle information via the CAN bus, and receives tire pressure, temperature, grounding characteristics, and grounding cycle information sent by the tire module wirelessly. It then determines the vehicle's driving status. If the vehicle is driving in a straight line at a constant speed, it proceeds to step S4; otherwise, it returns to step S2.

[0073] S4. The central module uses the received tire pressure, temperature, grounding characteristics and grounding cycle information to estimate the tire load. Based on the tire load estimate, tire pressure and tire temperature, the central module makes a tire safety judgment. If the tire is safe, the central module displays the tire pressure, temperature, tire load and safety status on the LCD screen, and then returns to step S2; otherwise, it proceeds to step S5.

[0074] S5. The central module sends alarm information to the alarm display device. The LCD screen displays the pressure, temperature, load and safety status information of different tires, and the digital tube displays the specific alarm information, such as: too high pressure, too low pressure, too high temperature, overload, etc. At the same time, the diode flashes and the alarm horn sounds an alarm to remind the driver to pay attention and take timely action. After the action is completed, the alarm information disappears, the tire danger is eliminated, and the process returns to step S2.

[0075] In step S2, the tire module uses the measured longitudinal and radial accelerations to extract the tire's ground contact characteristics and ground contact cycle information.

[0076] The tire's ground contact characteristics consist of part or all of the peak ground contact time, mean ground contact time, left width, left height, left area, right width, right height, right area, valley height, and depression area extracted from the measured radial acceleration, as well as the maximum, minimum, width, and area extracted from the measured longitudinal acceleration.

[0077] like Figure 2 As shown, the peak ground time of the radial acceleration is the distance between two consecutive peak values ​​of the radial acceleration within one cycle;

[0078] The mean grounding time of the radial acceleration is the first mean point extracted after the first peak is reached within a cycle, and the second mean point is extracted after the first mean point and before the second peak. The distance between the first and second mean points is the mean grounding time.

[0079] The left width of the radial acceleration is the distance between the first mean point and the first peak point;

[0080] The left height of the radial acceleration is the difference between the amplitude of the radial acceleration at the first peak position and the amplitude of the radial acceleration at the first mean point position;

[0081] The left area of ​​the radial acceleration is the sum of the differences between the amplitude of the radial acceleration and the amplitude of the mean radial acceleration between the first peak point and the first mean point;

[0082] The right width of the radial acceleration is the distance between the second mean point and the second peak point;

[0083] The right height of the radial acceleration is the difference between the amplitude of the radial acceleration at the second peak position and the amplitude of the radial acceleration at the second mean point position;

[0084] The right area of ​​the radial acceleration is the sum of the differences between the radial acceleration amplitude and the radial acceleration mean amplitude between the second mean point and the second peak point;

[0085] The valley height of the radial acceleration is the difference between the amplitude of the radial acceleration at the lowest point between the first and second mean points and the amplitude of the mean radial acceleration.

[0086] The area of ​​the radial acceleration depression is the sum of the differences between the radial acceleration amplitude and the mean radial acceleration amplitude between the first and second mean points.

[0087] The mean value of the radial acceleration is obtained by averaging the radial acceleration signals collected continuously for at least one cycle;

[0088] like Figure 3 As shown, the maximum value of the longitudinal acceleration is the difference between the amplitude of the longitudinal acceleration at the maximum value position within one cycle and the amplitude of the mean longitudinal acceleration.

[0089] The minimum value of the longitudinal acceleration is the difference between the amplitude of the longitudinal acceleration at the minimum position within one cycle and the amplitude of the mean longitudinal acceleration.

[0090] The width of the longitudinal acceleration is the distance between the maximum and minimum values ​​of the longitudinal acceleration;

[0091] The area of ​​the longitudinal acceleration is the sum of the difference between the amplitude of the longitudinal acceleration between the maximum and minimum points and the amplitude of the longitudinal acceleration at the minimum point.

[0092] The mean value of the longitudinal acceleration is obtained by averaging the longitudinal acceleration signals collected for at least one cycle;

[0093] like Figure 4 As shown, the grounding cycle information is the distance between two minimum values ​​of tire radial acceleration detected within two consecutive cycles.

[0094] The vehicle tire load estimation method described in this embodiment uses ground contact characteristics as a weighted sum of different characteristics of radial and longitudinal acceleration.

[0095]

[0096] In the formula, F represents the grounding characteristic, and f kTo differentiate between radial and longitudinal acceleration characteristics, selections can be made from: radial acceleration peak ground time, radial acceleration mean ground time, radial acceleration left width, radial acceleration left height, radial acceleration left area, radial acceleration right width, radial acceleration right height, radial acceleration right area, radial acceleration valley height, radial acceleration depression area, longitudinal acceleration maximum, longitudinal acceleration minimum, longitudinal acceleration width, and longitudinal acceleration area. k For the selected radial and longitudinal acceleration characteristics f k The corresponding weighting coefficients are obtained through experimental testing based on the correlation between different features and tire load, where m is the number of selected radial and longitudinal acceleration features.

[0097] The tire load estimation method described in this embodiment uses the tire contact patch feature as a weighted sum of different feature transformations of radial acceleration and longitudinal acceleration:

[0098]

[0099] In the formula, F represents the grounding characteristic. The results of different characteristic transformations of radial and longitudinal acceleration can be selected from the following: radial acceleration peak ground time / ground period information, radial acceleration mean ground time / ground period information, radial acceleration left width / ground period information, radial acceleration left height * ground period information, radial acceleration left area * ground period information, radial acceleration right width / ground period information, radial acceleration right height * ground period information, radial acceleration right area * ground period information, radial acceleration valley height * ground period information, radial acceleration depression area * ground period information, longitudinal acceleration maximum * ground period information, longitudinal acceleration minimum * ground period information, longitudinal acceleration width / ground period information, and longitudinal acceleration area * ground period information. l The selected radial and longitudinal acceleration characteristic transformation results The corresponding weighting coefficients were obtained through experimental testing based on the correlation between different feature transformation results and tire load. The number of selected radial and longitudinal acceleration characteristic transformation results.

[0100] This embodiment describes a method for estimating vehicle tire load, in which the central module estimates the tire load by combining a linear function, a cross term, and a quadratic function based on received tire pressure, ground contact characteristics, and ground contact cycle information.

[0101]

[0102] In the formula, Fz is the tire load, x1 is the tire pressure, x2 is the reciprocal of the tire contact cycle information, x3 is the tire contact characteristics, and p1, p2, p3, p4, p5, p6, p7, p8, p9, p 10 The parameter p is related to tire structure and wear; when estimating tire load, the estimated parameter p is used. i There is a nonlinear relationship between (i = 1-10) and the degree of wear w. Parameter a ij This can be identified based on experimental test data of tires with different wear levels.

[0103] In this embodiment, a 275 / 80R22.5 semi-worn tire was selected for experimental testing. Tire speeds were 20km / h, 30km / h, 40km / h, 50km / h, and 60km / h. Tire pressures were 700MPa, 800MPa, 900MPa, 1000MPa, and 1100MPa (cold state). Actual tire loads were 700kg, 900kg, 1100kg, 1300kg, 1500kg, 1700kg, 1900kg, 2100kg, 2300kg, 2500kg, 2700kg, 2900kg, 3100kg, 3300kg, 3500kg, and 3700kg. The tire pressure, longitudinal acceleration, and radial acceleration were measured using pressure and acceleration sensors installed inside the tire. The tire ground contact characteristics and ground contact period were extracted, and the tire load was estimated using a fitting formula.

[0104] Different grounding characteristics result in different fitting parameters. Based on actual experimental test results, the correlation between the characteristics of longitudinal and radial acceleration and the load is analyzed. Weighting coefficients are determined according to the magnitude of the correlation, and the required grounding characteristics are formed through weighted combination. In this embodiment, based on actual experimental test results, the radial acceleration peak grounding time t, which has a high correlation with tire load, is selected. m Mean radial acceleration grounding time t v Radial acceleration left width t lw Radial acceleration right width t rw Weighted summation is used as a grounding characteristic, i.e.

[0105] x3 = 0.25t m +0.4t v +0.2t lw +0.15t rw ;

[0106] The weighting coefficients were selected by fitting experimental test data.

[0107] After determining the ground contact characteristics, using experimental test data of the tire under different pressures, speeds, and loads, and based on the load estimation method described above, the relevant parameter results can be identified as follows:

[0108] p1=1408.0022; p2=-1.3337; p3=-445541.7749; p4=-0.0103; p5=204.1;

[0109] p6=1.6398e-05; p7=1.0211; p8=1.2307e-4; p9=63850876.8549; p10=2.1099e-08.

[0110] Based on experimental test data and identified parameters, tire load is estimated using a fitting formula. The estimated load results are as follows: Figure 5 As shown in the figure, the estimated load fluctuates around the actual value, and the ratio of the estimated deviation to the actual load is as follows: Figure 6 As shown, most of the estimation errors are within 10%, indicating that the estimation results are very accurate.

[0111] This embodiment describes a vehicle tire load estimation system, such as... Figure 7 As shown, it includes a tire module installed on the car tire and a central module installed inside the car; the tire module and the central module are wirelessly connected.

[0112] The tire module can receive a wake-up signal sent by the central module. After being woken up, the tire module measures the tire pressure, temperature, longitudinal acceleration and radial acceleration, performs data processing and judgment of the measurement information, extracts the tire's ground contact characteristics and ground contact cycle information, and transmits the acquired tire pressure, temperature, ground contact characteristics and ground contact cycle information to the central module wirelessly.

[0113] The central module receives information from the tire modules. It receives the vehicle's speed, acceleration, and steering angle information via the CAN bus and determines whether the vehicle is traveling at a constant speed in a straight line. When the vehicle is traveling at a constant speed in a straight line, the central module uses the tire pressure, ground contact characteristics, and ground contact cycle information sent by the tire modules to estimate the tire load. Specifically, when the vehicle speed exceeds 20 km / h, the acceleration is less than 0.01 m / s², and the steering angle is less than 2 degrees, the central module determines that the vehicle is traveling at a constant speed in a straight line and uses this information to estimate the tire load.

[0114] like Figure 8As shown, this embodiment discloses a vehicle tire load estimation system. The tire module is attached to the centerline of the inner wall of the vehicle tire. The tire module includes a tire pressure sensor, a tire temperature sensor, a tire acceleration sensor, a first microcontroller, a memory, a battery, a wake-up circuit, a radio frequency transceiver, and an antenna. In this embodiment, the tire pressure and tire temperature sensors use integrated HIWAY800 sensors to measure tire pressure and temperature. The tire acceleration sensor uses an ADXL372 sensor to measure the radial and longitudinal acceleration changes during tire movement. The microcontroller uses the integrated HIWAY800 microcontroller, and the memory uses the HIWAY800's built-in FLASH, which can store tire pressure sensor measurement information, tire temperature sensor measurement information, tire acceleration sensor measurement information, tire measurement information processing and judgment programs, tire ground contact feature extraction programs, and tire ground contact cycle extraction programs. The battery is connected to the first microcontroller to provide power. The wake-up circuit is connected to the first microcontroller and is used to generate a wake-up signal to wake up the first microcontroller under the action of an external wake-up pulse. The RF transceiver is an nRF905. It receives wake-up pulses from the central module and transmits tire pressure, temperature, grounding characteristics, and grounding cycle information. An antenna is connected to the RF transceiver. The tire pressure sensor, tire temperature sensor, tire acceleration sensor, RF transceiver, and memory are connected to the input / output interface of the first microcontroller. Information received by the RF transceiver, information stored in the memory, tire pressure measured by the tire pressure sensor, tire temperature measured by the tire temperature sensor, and radial and longitudinal acceleration measured by the tire acceleration sensor are sent to the first microcontroller through its input / output ports. The first microcontroller processes and judges the sensor measurement information, extracts tire grounding characteristics and grounding cycles, sends store or read commands to the memory to store or retrieve information, sends receive or transmit commands to the RF transceiver to control its receiving or transmitting status, and sends measurement and read commands to the tire pressure sensor, tire temperature sensor, and tire acceleration sensor to measure and read the tire status.

[0115] This embodiment describes a vehicle tire load estimation system, as shown in the attached figure. Figure 9 The central module shown is installed in the car's driver's cab. The central module includes a keypad, a second microcontroller, a memory, a display and alarm device, a power supply, a CAN transceiver, an RF transceiver, and an antenna.

[0116] The keypad is used for human-machine interaction. The microcontroller is a PIC16F877, and the memory is the microcontroller's built-in FLASH, which can store tire pressure and temperature measurement information, tire contact patch characteristic information, tire contact patch cycle information, tire load estimation programs and results, tire safety status judgment programs and results, and vehicle driving status judgment programs and results. The display and alarm devices include an LCD screen, digital tubes, LEDs, a flashing light, a horn, and an alarm. The LCD screen displays tire pressure, temperature, load, and safety status. The digital tubes and LEDs display dangerous status signals such as excessive tire pressure, insufficient pressure, excessive temperature, and overload. The flashing light, horn, and alarm provide warnings to alert the driver. The CAN transceiver is an SCM3425ASA, connecting the second microcontroller and other vehicle control modules. They exchange information via the CAN bus. The second microcontroller obtains vehicle speed, acceleration, and steering angle information via the CAN bus. The power supply is connected to the second microcontroller and can be either a battery or the vehicle's power supply to power the central module. The radio frequency transceiver is an nRF905, operating at a frequency of 433MHz. The antenna is connected to the radio frequency transceiver. The radio frequency transceiver and the antenna enable wireless information transmission between the central module and the tire module. The radio frequency transceiver receives tire pressure, temperature, grounding characteristics and grounding cycle information transmitted by the tire module and transmits a wake-up pulse signal to the tire module. The antenna is connected to the RF transceiver. The keypad, memory, display alarm device, CAN transceiver, and RF transceiver are respectively connected to the input / output interface of the second microcontroller. Information input from the keypad, information stored in the memory, information received by the CAN transceiver, and information received by the RF transceiver are all sent to the second microcontroller through its input / output ports. The second microcontroller sends store or read commands to the memory through its input / output ports to store or retrieve information. The second microcontroller sequentially executes the vehicle driving status judgment program, the tire load estimation program, and the tire safety status judgment program. Based on the estimation and judgment results, it sends a command and content to the display alarm device to display the alarm, sends a receive or send command to the CAN transceiver to control the reception or transmission of CAN bus signals, and sends a receive or transmit command to the RF transceiver to control its reception or transmission status.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method of estimating the load of a vehicle tire, characterized by: The application relates to a tire module installed on a tire of a vehicle and a central module installed in the vehicle, and comprises the following steps: S1. After the vehicle starts, the central module in the vehicle sends a wake-up command to the tire module to wake up the tire module; S2. The tire module measures the pressure, temperature, longitudinal acceleration and radial acceleration of the tire, processes and judges the measurement signals, extracts the tire ground contact characteristics and ground contact period information after removing interference noise through smooth filtering; S3. The central module receives the speed, acceleration and steering angle information of the vehicle through a CAN bus, receives the pressure, temperature, ground contact characteristics and ground contact period information of the tire sent by the tire module through a wireless mode, judges the vehicle running state according to the speed, acceleration and steering angle information of the vehicle, and if the vehicle is in a straight-line uniform-speed running state, the step S4 is entered, otherwise the step S2 is returned; S4. The central module estimates the tire load by using the received pressure, temperature, ground contact characteristics and ground contact period information of the tire, judges the tire safety according to the tire load estimation, the pressure of the tire and the temperature of the tire, if the tire is safe, the central module displays the pressure, temperature, tire load and safety state of the tire through a liquid crystal screen, and then returns to the step S2, otherwise the step S5 is entered; S5. The central module sends an alarm information to an alarm display device to display the pressure, temperature, tire load and safety state information of the tire, reminds the driver to pay attention and timely process, after the processing is completed, the alarm information disappears, the tire danger is removed, and the step S2 is returned; In the step S2, the tire module extracts the tire ground contact characteristics and ground contact period information by using the measured longitudinal acceleration and radial acceleration; The tire ground contact characteristics are composed of part or all of the peak ground contact time, mean ground contact time, left width, left height, left area, right width, right height, right area, valley bottom height and trapped area extracted from the measured radial acceleration, and the maximum value, minimum value, width and area extracted from the measured longitudinal acceleration; The peak ground contact time of the radial acceleration is the distance between two continuous peaks of the radial acceleration in a period; The mean ground contact time of the radial acceleration is that after the first peak is reached, the point closest to the mean value is extracted as a first mean value point, after the first mean value point and before the second peak, the point closest to the mean value is extracted as a second mean value point, and the distance between the first and second mean value points is the mean ground contact time; The left width of the radial acceleration is the distance between the first mean value point and the first peak; The left height of the radial acceleration is the difference between the amplitude of the radial acceleration at the first peak position and the amplitude of the radial acceleration at the first mean value point position; The left area of the radial acceleration is the cumulative sum of the amplitude difference between the radial acceleration and the mean value of the radial acceleration between the first peak and the first mean value point; The right width of the radial acceleration is the distance between the second mean value point and the second peak; The right height of the radial acceleration is the difference between the amplitude of the radial acceleration at the second peak position and the amplitude of the radial acceleration at the second mean value point position; The right area of the radial acceleration is the cumulative sum of the difference between the radial acceleration amplitude and the radial acceleration mean amplitude between the second mean point and the second peak; The valley height of the radial acceleration is the difference between the radial acceleration amplitude and the radial acceleration mean amplitude at the lowest point between the first mean point and the second mean point; The trap area of the radial acceleration is the cumulative sum of the difference between the radial acceleration amplitude and the radial acceleration mean amplitude between the first mean point and the second mean point; The mean of the radial acceleration is obtained by averaging the radial acceleration signal collected for at least one period; The maximum value of the longitudinal acceleration is the difference between the longitudinal acceleration amplitude and the longitudinal acceleration mean amplitude at the maximum value position of the longitudinal acceleration in one period; The minimum value of the longitudinal acceleration is the difference between the longitudinal acceleration amplitude and the longitudinal acceleration mean amplitude at the minimum value position of the longitudinal acceleration in one period; The width of the longitudinal acceleration is the distance between the maximum value and the minimum value of the longitudinal acceleration; The area of the longitudinal acceleration is the cumulative sum of the difference between the longitudinal acceleration amplitude and the longitudinal acceleration mean amplitude between the maximum value point and the minimum value point of the longitudinal acceleration; The mean of the longitudinal acceleration is obtained by averaging the longitudinal acceleration signal collected for at least one period; The ground contact period information is the distance between the two minimum values detected by the radial acceleration of the tire in two consecutive periods.

2. A method of estimating the load of a vehicle tire as recited in claim 1, wherein: The ground contact feature is a weighted sum of different features of the radial acceleration and the longitudinal acceleration: ; wherein is a ground feature, is a different feature of the radial acceleration and longitudinal acceleration, selected from the group consisting of: radial acceleration peak ground time, radial acceleration mean ground time, radial acceleration left width, radial acceleration left height, radial acceleration left area, radial acceleration right width, radial acceleration right height, radial acceleration right area, radial acceleration valley height, radial acceleration trap area, longitudinal acceleration maximum, longitudinal acceleration minimum, longitudinal acceleration width, and longitudinal acceleration area, is the selected radial acceleration and longitudinal acceleration feature a corresponding weighting factor, the weighting factor being obtained by experimental testing according to the correlation between the different features and the tire load, is the number of selected radial acceleration and longitudinal acceleration features.

3. A method of estimating the load of a vehicle tire as recited in claim 1, wherein: The tire ground contact feature is a weighted sum of the transformed different features of the radial acceleration and the longitudinal acceleration: ; wherein is a ground contact feature, is a result of different feature transformations of the radial acceleration and the longitudinal acceleration, and can be selected from the radial acceleration peak ground contact time / ground contact period information, the radial acceleration mean ground contact time / ground contact period information, the radial acceleration left width / ground contact period information, the radial acceleration left height / ground contact period information, the radial acceleration left area / ground contact period information, the radial acceleration right width / ground contact period information, the radial acceleration right height / ground contact period information, the radial acceleration right area / ground contact period information, the radial acceleration valley height / ground contact period information, the radial acceleration trap area / ground contact period information, the longitudinal acceleration maximum / ground contact period information, the longitudinal acceleration minimum / ground contact period information, the longitudinal acceleration width / ground contact period information, and the longitudinal acceleration area / ground contact period information, is the selected radial acceleration and longitudinal acceleration feature transformation result is a corresponding weighting coefficient, and the weighting coefficient is obtained through experimental testing according to the correlation between the different feature transformation results and the tire load, is the number of the selected radial acceleration and longitudinal acceleration feature transformation results.

4. The method of claim 1, wherein: The central module estimates the tire load according to the received tire pressure, ground contact feature, and ground contact period information, and combines the first-order function, cross term, and quadratic function: wherein, is the tire load, is the tire pressure, is the inverse of the tire ground contact periodicity information, is the tire ground contact signature, is a parameter related to the tire structure and wear.

5. A method of estimating the load of a vehicle tire according to claim 4, characterized in that: When performing tire load estimation, the estimated parameters are... and degree of wear There is a nonlinear relationship between them. ,parameter This was identified based on experimental test data of tires with different wear levels.

6. An automotive tire load estimation system characterized by: The system includes a tire module arranged in a vehicle tire and a central module arranged in the vehicle; the tire module and the central module are connected wirelessly; The tire module receives the wake-up signal sent by the central module, and after waking up, measures the tire pressure, temperature, longitudinal acceleration, and radial acceleration, processes and judges the measurement information, extracts the tire ground contact feature and ground contact period information, and transmits the obtained tire pressure, temperature, ground contact feature, and ground contact period information to the central module wirelessly; The central module receives the information sent by the tire module, receives the vehicle speed, acceleration, and steering angle information through the CAN bus, and judges whether the vehicle is in a uniform straight-line driving state according to the received information; when the vehicle is in a uniform straight-line driving state, the central module estimates the tire load using the tire pressure, ground contact feature, and ground contact period information sent by the tire module.

7. A system for estimating the load of a vehicle tire according to claim 6, characterized in that: The tire module is attached to the inner wall centerline position of the vehicle tire; the tire module includes a tire pressure sensor, a tire temperature sensor, a tire acceleration sensor, a first microcontroller, a memory, a battery, a wake-up circuit, a radio frequency transceiver, and an antenna; The tire pressure sensor measures the pressure change of the tire, the tire temperature sensor measures the temperature change of the tire, and the tire acceleration sensor measures the longitudinal and radial acceleration changes of the tire; The memory stores the tire pressure sensor measurement information, the tire temperature sensor measurement information, the tire acceleration sensor measurement information, the processing and judgment program of the tire measurement information, the tire ground contact feature extraction program, and the tire ground contact cycle extraction program; The radio frequency transceiver receives the wake-up pulse transmitted by the central module, and transmits the pressure, temperature, ground contact feature, and ground contact cycle information of the tire; The battery is connected to the first microcontroller, and the wake-up circuit is connected to the first microcontroller. The wake-up circuit generates a wake-up signal under the action of the wake-up pulse transmitted by the central module to wake up the first microcontroller. The antenna is connected to the radio frequency transceiver; The tire pressure sensor, the tire temperature sensor, the tire acceleration sensor, the radio frequency transceiver, and the memory are connected to the input / output interface of the first microcontroller. The information received by the radio frequency transceiver, the information stored in the memory, the tire pressure measured by the tire pressure sensor, the tire temperature measured by the tire temperature sensor, and the radial and longitudinal accelerations measured by the tire acceleration sensor are sent to the first microcontroller through the input / output interface of the first microcontroller. The first microcontroller processes and judges the sensor measurement information, extracts the tire ground contact feature, and extracts the ground contact cycle. The first microcontroller sends storage or reading commands to the memory through the input / output interface to store or read information, sends receiving or transmitting commands to the radio frequency transceiver to control the working state of the radio frequency transceiver, and sends measurement and reading commands to the tire pressure sensor, the tire temperature sensor, and the tire acceleration sensor to measure and read the tire state.

8. A system for estimating the load of a vehicle tire according to claim 6, characterized in that: The central module is installed in the cab of the vehicle, and the central module includes a keypad, a second microcontroller, a memory, a display alarm device, a power supply, a CAN transceiver, a radio frequency transceiver, and an antenna; The keypad is used for human-computer interaction. The memory stores tire pressure measurement information, tire temperature measurement information, tire ground contact feature information, tire ground contact cycle information, tire load estimation program and estimation results, tire safety state judgment program, tire safety state judgment results, vehicle driving state judgment program, and vehicle driving state judgment results. The display alarm device displays the pressure, temperature, load, and safety state of the tire and sends an alarm message when the tire state is abnormal; The CAN transceiver receives the vehicle speed, acceleration, and steering angle information of the vehicle; The radio frequency transceiver receives the tire pressure, temperature, ground contact feature, and ground contact cycle information transmitted by the tire module, and transmits a low-frequency wake-up pulse signal; The power supply is connected with the second microcontroller, the antenna is connected with the radio frequency transceiver, the small keyboard, the memory, the display alarm device, the CAN transceiver and the radio frequency transceiver are connected with the input and output interface of the second microcontroller respectively, the information input by the small keyboard, the information stored by the memory, the information received by the CAN transceiver and the information received by the radio frequency transceiver are all sent to the second microcontroller through the input and output interface of the second microcontroller, the second microcontroller sends the storage or reading command to the memory through the input and output interface to access the information, the second microcontroller sequentially executes the automobile running state judgment program, the tire load estimation program and the tire safety state judgment program, according to the estimation and judgment results, the second microcontroller sends the display alarm command and content to the display alarm device, the second microcontroller sends the receiving or sending command to the CAN transceiver to control the receiving or sending of the CAN bus signal, and the second microcontroller sends the receiving or sending command to the radio frequency transceiver to control the working state of the radio frequency transceiver.

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