A real-time monitoring method for tire vertical load using angle calculation and a tire for real-time load monitoring

Abstract

The present invention provides a real-time monitoring method for tire vertical load using angle calculation and a tire for real-time load monitoring. By installing a sensor on the tire sidewall, when the tire starts to roll, the Z-axis acceleration of the sensor is sampled, and the time when the sensor installed on the tire sidewall enters the tire ground contact patch area is calculated through the tire rotation speed. When the sensor of the tire enters the tire ground contact patch area calculated by the tire rotation speed, there is a negative value in the first half of the sampling period of the Z-axis acceleration of the sensor, and when the absolute value obtained in the sampling period is greater than the set threshold, the X-axis acceleration and Y-axis acceleration of the tire are obtained by sampling the sensor. The obtained value is calculated through the X-axis acceleration and Y-axis acceleration of the tire. Step 13) Each value obtained by sampling is compared with the previous value, and the minimum value obtained within the sampling interval is used as the transmitted data and sent to the vehicle-mounted terminal. The vehicle-mounted terminal obtains the data sent by the sensor and estimates the vehicle load through the load correspondence table.

Description

Technical Field

[0001] The present invention relates to the field of tire monitoring, and more specifically, to a method for real-time monitoring of tire vertical load using angle calculation and a tire for real-time load monitoring. Background Art

[0002] A tire pressure monitoring system can monitor the air pressure and temperature of a tire. A more complete tire condition monitoring system, also known as an intelligent tire system, can achieve more functions by collecting more useful signals. It buries micro sensors inside the tire to directly monitor various parameters of the tire (such as tire air pressure, tire temperature, vertical load, wear condition, six-component force, and tire-road adhesion coefficient), and provides the information to the vehicle's power control system. Real-time acquisition of tire force information is an important research content of intelligent tires, which has important significance for automotive mechanical control. The real-time measurement of tire force has always attracted the attention of scholars at home and abroad. However, due to the non-linearity of the tire system, it is difficult to directly obtain tire force information. In many studies, tire force is mostly derived or estimated indirectly.

[0003] In the prior art, Patent CN201410071985.7 discloses a mapping relationship between the vertical load of a tire and tire parameters calibrated through a bench test, and then obtains the vehicle driving parameters required for the mapping relationship through a GPS vehicle speed test device, a tire pressure monitoring system, an ABS wheel speed sensor, etc., so as to obtain the tire load during vehicle driving.

[0004] However, in the prior art, sensors are all arranged at the bottom of the tire crown, and the centrifugal acceleration value at the bottom of the tire crown is used to estimate the length of the tire contact patch, so as to calibrate the tire vertical load. However, the acceleration magnitude at the bottom of the tire crown fluctuates too much with the vehicle speed (taking a 13R22.5 all-steel tire as an example, the centrifugal acceleration is 15.4 m 2 / s when the vehicle speed is 10 Km / h, and the centrifugal acceleration is 1250 m 2 / s when the vehicle speed is 90 Km / h. Generally, the acceleration range is selected to be around ±200g). To improve the measurement accuracy, the measurement of the load is usually started at a fixed vehicle speed (such as a vehicle speed of 60 Km / h). However, the above technical solutions have the following technical defects, for example: 1. It is impossible to measure the tire load at low speed or when the vehicle is moving slowly (such as: it is impossible to monitor the vehicle load when the vehicle moves slowly after loading goods). 2. High-frequency acceleration sampling must be carried out during the tire rolling period, increasing the battery power consumption. 3. It is easy to be damaged by a nail piercing the sensor at the bottom of the tire crown. Summary of the Invention

[0005] The present invention overcomes the deficiencies of the prior art and provides a method for real-time monitoring of tire vertical load using angles and a tire for real-time load monitoring.

[0006] To solve the above technical problems, the technical solution of the present invention is as follows:

[0007] A method for real-time monitoring of tire vertical load using angles includes the following steps:

[0008] Step 11): Install the sensor on the tire sidewall. When the tire starts to roll, sample the Z-axis acceleration of the sensor, and calculate the time when the sensor installed on the tire sidewall enters the tire ground contact patch area through the tire rotation speed.

[0009] Step 12): When the sensor of the tire enters the tire ground contact patch area calculated by the tire rotation speed, if the Z-axis acceleration of the sensor has a negative value in the first half of the sampling period and the absolute value obtained in the sampling period is greater than the set threshold, sample the X-axis acceleration and Y-axis acceleration of the tire by the sensor, and calculate the tanθ value through the X-axis acceleration and Y-axis acceleration of the tire.

[0010] Step 13): Compare the tanθ value obtained each time with the previous value, and take the minimum tanθ obtained within the sampling interval as the data to be sent and send it to the vehicle-mounted terminal.

[0011] Step 14): The vehicle-mounted terminal obtains the data sent by the sensor and estimates the vehicle load through the load correspondence table.

[0012] Further, the sensor is a triaxial acceleration sensor, and its Z-axis acceleration is the circumferential acceleration.

[0013] Further, the load correspondence table is obtained through the following steps:

[0014] 31): Install the tire with the sensor on the load calibration device and inflate it to the standard air pressure.

[0015] 32): Load the tire to the maximum load, start the internal calibration program of the sensor through the excitation device, and slowly roll the tire to let the sensor find the maximum angle deformation point of the tire.

[0016] 33): Keep the tire stationary, and the load calibration device continuously reduces the load from the maximum load to 0, and then loads from 0 to the maximum load. The sensor records the angle change data of the whole process.

[0017] 34): Automatically upload and store the relationship between the sensor angle change data and the load through the load calibration device, so as to obtain the load calibration correspondence table.

[0018] Further, the load correspondence table can be the relationship between the tanθ value and the load.

[0019] Further, in step 12), when the sensor of the tire enters the tire imprint area, the sensor adopts a low sampling rate f 1 Collect the Z-axis acceleration in the tire rolling direction in real time, and compare it with the set threshold in real time. When the Z-axis acceleration of the sensor has a negative value in the first half of the sampling period, and the absolute value obtained in the first half of the sampling period is greater than the absolute value of the set threshold;, trigger the Y-axis acceleration of the sensor and the X-axis acceleration to perform high-frequency sampling rate f n , and calculate the tanθ value after filtering.

[0020] Further, when the tanθ values obtained by continuous three calculations are successively increasing, the high-frequency sampling rate f of the X-axis acceleration and the Y-axis acceleration of the sensor stops. n .

[0021] Further, the load calibration device automatically uploads to the cloud, and the cloud calculates and converts the load correspondence table at different air pressures, temperatures and rotational speeds by combining the sensor angle change data and the load relationship.

[0022] A tire for real-time load monitoring obtains the real-time load by using the method for real-time monitoring of the vertical load of the angular tire.

[0023] The advantages of the present invention compared with the prior art are as follows:

[0024] 1. Different from the prior art, the present invention does not calculate and monitor the real-time load by detecting the radial centrifugal acceleration. Therefore, when the vehicle tire rolls at a low speed (for example: when moving the vehicle just after loading the goods, it is necessary to know the load weight), the acceleration value at the bottom of the tire crown is too small, and due to the low resolution of the large-range acceleration at a small acceleration value, the measurement accuracy of the load is affected.

[0025] 2. Since the acceleration measurement interval related to the load calculation is only in the ground contact imprint area, and the acceleration value in the ground contact imprint area is the vector decomposition of the gravitational acceleration value on the X and Y axes, a large-range accelerometer is not required, and the small-range accelerometer has a lower cost, thus reducing the manufacturing cost.

[0026] 3. An acceleration chip with three axes is adopted. Based on the comparison between the absolute value of the acceleration in the Z-axis and the absolute value of a set threshold, in the non-imprint area, calculations are performed through the tire rotation speed. At this time, only the Z-axis of the sensor performs low-frequency sampling, and the X-axis and Y-axis can be in a sleep state or perform low-frequency sampling. When entering the grounding imprint area, the Z-axis acceleration of the sensor is sampled at a lower frequency. When there is a negative value in the Z-axis acceleration value obtained by sampling in the first half cycle, and the absolute value of the Z-axis acceleration in the first half cycle is greater than the absolute value of the set threshold, high-frequency sampling of the X-acceleration and Y-acceleration of the wheel sensor is triggered. That is, the acceleration chip with three axes does not need to be turned on throughout the process. It judges when to perform high-frequency sampling work based on the Z-axis acceleration value, reducing power consumption. Description of the Drawings

[0027] Figure 1 Schematic diagram of the installation direction of the three-axis acceleration sensor;

[0028] Figure 2 Schematic diagram of the position where the three-axis acceleration sensor is set on the side of the tire;

[0029] Figure 3 Schematic diagram of the changes before and after loading of the 13R22.5 tire;

[0030] Figure 4 Schematic diagram of the change in the Z-axis acceleration in the theoretical state during one week of the tire;

[0031] Figure 5 Schematic diagram of the inclination change during the rolling of the tire. Detailed Implementation Manner

[0032] The following detailed implementation manner further describes the present invention.

[0033] Regarding the implementation manner of the present invention, a large angle change is beneficial to sensor measurement and resolution improvement. Therefore, the placement positions of the sensors for different tire models should meet the following: 1) The inclination change is large; 2) The angle change range is in the area between 30° and 60° with respect to the horizontal plane. Selecting the angle within this range is beneficial for having a better slope interval when using trigonometric functions, facilitating the improvement of calculation accuracy.

[0034] To further illustrate the technical solution of the present invention, the embodiments are all based on the 13R22.5 tire as an example of the tire.

[0035] Embodiment 1:

[0036] Manufacturing stage:

[0037] As follows Figure 1As shown, the sensor chip is encapsulated and integrated into the housing, and then the housing is embedded into the rubber sleeve formed by molding. During the encapsulation process, the coordinate systems of the acceleration sensor correspond one by one with those on the rubber sleeve. In this way, the acceleration sensor assembly for measuring the vertical load of the tire (including components such as battery, Bluetooth, air pressure, temperature, acceleration, and circuit board) is ready for use.

[0038] First, the acceleration sensor assembly is embedded inside the rubber patch.

[0039] Secondly, different from the prior art where the acceleration sensor assembly is arranged at the bottom of the tire crown, in the present invention, the rubber patch embedded with the speed sensor assembly is installed in the corresponding area on the inner side wall of the tire airtight layer. Since the working principle is completely different from that of the prior art, it does not need to detect the radial acceleration of the tire. Preferably, according to the parameters of this type of tire, the corresponding area on the inner side wall of the tire airtight layer is calculated. After finding the corresponding area, the subsequent specific installation method can be, for example, using a manipulator for installation. Through processes such as cleaning, grinding, applying vulcanizing machine, heating, mounting and pressing, applying sealant, and information binding, it is ensured that the sensor is firmly adhered to the tire. See the patent "A System for Automatically Fitting TPMS Sensors Inside Tires" CN201911088548.

[0040] As Figure 1 shown, during the pasting process, it is necessary to ensure that the Z-axis acceleration arrow marked on the rubber patch embedded with the acceleration sensor assembly points to the sensor installation direction, which is the circumferential acceleration. For example, in Figure 2 , the Z-axis acceleration points in the direction passing through the paper surface, the Y-axis acceleration direction of the sensor points obliquely downward, and at this time, the X-axis acceleration direction is the tangential direction of the tire side.

[0041] Thirdly, a tire load comparison table is calibrated. As Figure 2 shown, the tire with the rubber patch embedded with the speed sensor assembly installed is mounted on the load calibration device and filled with standard air pressure (such as 930 kPa).

[0042] Step 1: First, apply the maximum load to the tire. Through the excitation device, start the internal calibration process of the sensor, and slowly roll the tire to make the sensor mounting position on the tire undergo the maximum deformation (the condition for the sensor to measure the side deformation of the tire is that since the mounting area of the rubber patch embedded with the speed sensor assembly must be in the exact middle of the tire contact patch, the mounting position of the rubber patch embedded with the acceleration sensor assembly must roll to the bottom. Generally, the mounting position of the rubber patch embedded with the speed sensor assembly is the light point of the tire dynamic balance. The light point position of the tire can be directly rolled to the bottom first, and in this way, quickly locate near the area with the maximum deformation to improve the calibration efficiency). Preferably, in order to improve the accuracy, it is necessary to roll back and forth three times in the maximum deformation area to confirm the maximum point.

[0043] Step 2: The tire remains stationary. The load calibration device continuously reduces the load from the maximum load to 0, and then increases the load from 0 to the maximum value, and repeats the measurement once. The sensor records the angular change data throughout the process. What tanθ reflects is the angle θ between the mating surface at the sensor installation location after deformation and the horizontal plane. When there is no load on the tire, the angle at this location with the horizontal plane is relatively large. After loading, it starts to deform and the angle decreases.

[0044] So far, the load calibration corresponding table for this type of tire's tanθ and load is obtained for this tire, and is automatically uploaded to the cloud storage of the tire intelligent system through the load calibration device. This tire can thus achieve the calibration work of a tire load. Preferably, the intelligent system platform will calculate and convert the load corresponding tables under different air pressures, temperatures, and rotational speeds based on this data. When this tire with real-time load monitoring is applied to a certain vehicle, after the user binds the unique ID of this tire, the system sends the load corresponding table of this tire to the vehicle terminal. The load corresponding table includes the influences of factors such as tire temperature, air pressure, and rotational speed.

[0045] The angle change measurement principle of the present invention is as Figure 2 shown. Before loading After loading Among them, the measured values of X and Y are, in an ideal state, the components of gravity g in two directions (when the tire acceleration sensor rotates to contact the road surface, the radial centrifugal acceleration of the tire in this area is 0 at this time; the sensor has a built-in filtering algorithm to remove the influence of ground interference acceleration). After the tire is subjected to a load, the tire acceleration sensor tilts, so the measured values of the X and Y axial accelerations will also change significantly.

[0046] As Figure 3 shown, in this case, when the tire is unloaded, X 0 = 0.776g, Y 0 = 0.632g, then that is, θ 0 = 50.78°. When the tire is loaded to the maximum calibration load, X 1 = 0.475g, Y 1 = 0.880g, then that is, θ 1 = 28.39°. Preferably, considering that the sensor consumes battery energy for collecting data, processing data, and sending data, the sensor only calculates the value of tanθ, that is, the ratio of X to Y, fills it into the radio frequency message and transmits it to the vehicle terminal, without further solving the inverse trigonometric function θ. After receiving the acceleration sensor, temperature, tire pressure, and rotational speed data, the vehicle terminal uses the tire load corresponding table of this terminal to estimate the vehicle load.

[0047] Preferably, after receiving the data from the acceleration sensor, the in-vehicle terminal combines a filtering algorithm, a terminal tire load comparison table, and the tire distribution to estimate the vehicle load.

[0048] Operation stage:

[0049] In the embodiment of the present invention, when the tire rolls, in the non-ground contact imprint area of the tire, the mounting area of the tire sidewall sensor is basically invariant. Since the acceleration values where the change of tanθ is not in the ground contact imprint area of the tire are all invalid, detecting the inclination angle in this area is also invalid at this time. At this time, the X and Y axis accelerations of the sensor can be in a dormant state or low-frequency sampling, thereby saving electric energy.

[0050] In the operation stage of the embodiment of the present invention, during one revolution of the tire, the sensor only needs to perform high-frequency measurement on the period at the ground contact imprint of the tire. Preferably, according to the change of the value of tanθ, within the period at the ground contact imprint of the tire, it can be achieved by high-frequency measurement of most of the period data, and the sampling frequency can be further increased according to the inclination change speed, while further saving power and improving the load measurement accuracy.

[0051] As Figure 4 shown, the data sampled by the Z-axis acceleration in the sensor of the present invention, that is, the circumferential acceleration of the tire, its greatest feature is that the acceleration suddenly becomes very large when it first touches the ground, gradually decreases to 0 as the sensor mounting area on the tire further contacts the ground, and gradually increases again in the second half of the period in the imprint area. The present invention uses the fluctuation of the Z-axis circumferential acceleration as the starting condition for judging load measurement. When specific conditions are met, the sampling frequency is increased, thereby improving the measurement accuracy. When not met, the X and Y axis accelerations of the sensor are in a dormant state or low sampling frequency, thereby saving electric energy. Compared with the published scheme of collecting radial acceleration to calculate tire load measurement, the advantage is that it does not require continuously turning on the high-speed acceleration sampling frequency in real time within one measurement period, reducing data processing and calculation, thereby saving electric energy.

[0052] The specific steps are as follows:

[0053] Step 1: Set the absolute value threshold |a z |, where |a z | is the absolute value of a z . When the tire starts to roll, calculate the time when the tire enters the ground contact imprint area according to the rotational speed of the tire. At this time, the Z-axis acceleration of the sensor has a lower sampling rate, for example, lower than 100 Hz, and the X and Y axis accelerations are in a dormant state or low-frequency sampling and other states to save electric energy.

[0054] When entering the ground contact imprint area of the tire, the sensor performs low sampling rate f 1 (for example: f1 The setting of this value satisfies the requirement of sampling more than 4 times within the imprint area. The MCU in the sensor collects the Z-axis acceleration in real time, filters it to remove interference, and compares it with |a z | in real time.

[0055] Step 2: When the tire enters the ground contact imprint area, the Z-axis acceleration value obtained by sampling has a negative value in the first half of the sampling period. If it is set that f 1 is to sample 4 times within the imprint area, then the Z-axis acceleration value obtained in the first or second sampling is negative, and when the absolute value of the Z-axis acceleration value is greater than |a z | during the first half of the sampling period, the x-axis acceleration and y-axis acceleration are triggered to sample at a high sampling frequency f h For example, a frequency above 3000 Hz is used. After filtering and removing interference data, the tanθ value is calculated.

[0056] Preferably, when determining that the Z-axis acceleration value is negative, the purpose is to further determine that the tire has just entered the ground contact imprint area. Therefore, in essence, regardless of how the sampling rate f 1 of the Z-axis acceleration value is set, only the first two times are required for the negative value judgment.

[0057] For example, corresponding to Figure 4 or Figure 5 as shown, the Z-axis acceleration value is negative and its absolute value is greater than |a z |, which means the sensor has just touched the ground and is between t-1 and t1. At this time, the measured X and Y axis acceleration values are valid. Let the sampling time of the X and Y axis accelerations started at this time be t 0 , and the calculated tanθ 1

[0058] Step 3: Compare the tanθ values. According to Figure 5 as shown, when the sensor of the tire just starts to enter the ground contact imprint area, the tanθ value gradually decreases. When the area has turned through half of the tire imprint area, tanθ starts to increase. The tanθ value should satisfy the process of gradually decreasing and then increasing.

[0059] After each data collection, it is compared with the previous sampling data until it is found that the tanθ value starts to increase. Then the minimum tanθ value is stored as the data to be sent via Bluetooth to the vehicle-mounted terminal. At this time, the sampling stops, and the threshold for stopping sampling is judged by the tanθ value, so that the sensor does not need to sample throughout the time of the entire tire ground contact imprint area, further shortening the working time and saving electrical energy. However, judging the basis for the sensor to leave the ground by whether the Z-axis acceleration value is positive can also achieve the technical effect of the present invention.

[0060] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as within the scope of protection of the present invention.

Claims

1. A real-time monitoring method for tire vertical load using angle calculation, characterized in that, it includes the following steps: Step 11) Install the sensor on the tire sidewall, ensure that the Z-axis acceleration arrow marked on the rubber patch embedded with the acceleration sensor assembly points to the sensor installation direction, and its Z-axis acceleration is the circumferential acceleration. When the tire starts to roll, sample the Z-axis acceleration of the sensor, and calculate the time when the sensor installed on the tire sidewall enters the tire grounding imprint area through the tire rotation speed; Step 12) When the sensor of the tire enters the tire grounding imprint area calculated by the tire rotation speed, there is a negative value in the first half of the sampling period of the Z-axis acceleration of the sensor, and when the absolute value obtained in the sampling period is greater than the set threshold, sample the X-axis acceleration and Y-axis acceleration of the tire by the sensor, and calculate the tanθ value through the X-axis acceleration and Y-axis acceleration of the tire; In step 12), when the sensor of the tire enters the tire imprint area, the sensor adopts a low sampling rate f 1 to collect the Z-axis acceleration in the tire rolling direction in real time and compare it with the set threshold in real time. When there is a negative value in the first half of the sampling period of the Z-axis acceleration of the sensor and the absolute value obtained in the first half of the sampling period is greater than the absolute value of the set threshold; trigger the high-frequency sampling rate f of the Y-axis acceleration and the X-axis acceleration of the sensor n , and calculate the tanθ value after filtering; Step 13) Compare the tanθ value obtained each time with the previous value, and then use the minimum tanθ obtained within the sampling interval as the transmitted data and send it to the vehicle-mounted terminal; Step 14) The vehicle-mounted terminal obtains the data sent by the sensor and estimates the vehicle load through the load correspondence table.

2. A real-time monitoring method for tire vertical load using angle according to claim 1, characterized in that, the sensor is a three-axis acceleration sensor.

3. A real-time monitoring method for tire vertical load according to claim 1, characterized in that, the load correspondence table is obtained through the following steps: Step 31) Install the tire with the sensor on the load calibration device and fill it with standard air pressure; Step 32) Load the tire to the maximum load, start the internal calibration program of the sensor through the excitation device, and slowly roll the tire to let the sensor find the maximum angle deformation point of the tire; Step 33) Keep the tire stationary, and the load calibration device continuously reduces the load from the maximum load to 0, and then loads from 0 to the maximum load. The sensor records the angle change data of the whole process; Step 34) Automatically upload and store the relationship between the sensor angle change data and the load through the load calibration device, so as to obtain the load calibration correspondence table.

4. A real-time monitoring method for tire vertical load using angle according to claim 1 or 3, characterized in that, the load correspondence table is the relationship between the tanθ value and the load.

5. A real-time monitoring method for tire vertical load using angle according to claim 1, characterized in that, When the tanθ values obtained from three consecutive calculations are successively increasing, the high-frequency sampling rate f of the X-axis acceleration and Y-axis acceleration of the sensor stops. n .

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