Tire vertical force measurement apparatus and measurement method

Abstract

Disclosed in the present invention are a tire vertical force measurement apparatus and measurement method. The apparatus comprises a strain sensing module, a data transmission module and a control module, wherein the strain sensing module and the data transmission module are both arranged on an inner side of a tire to be measured; the strain sensing module is connected to the data transmission module, and the data transmission module is connected to the control module; the strain sensing module comprises a strain sensor, and the strain sensor comprises an upper substrate made of a rubber material, a lower substrate made of a rubber material, a sensitive layer and sensor terminals; the sensitive layer is arranged between the upper substrate and the lower substrate, and the sensor terminals are arranged on two sides of the strain sensor; the strain sensing module is used for acquiring a strain waveform of said tire and transmitting the strain waveform to the data transmission module; the data transmission module is used for transmitting the strain waveform to the control module; and the control module is used for performing tire vertical force measurement on the basis of the strain waveform, so as to obtain a tire vertical force. The present invention can effectively improve the accuracy of tire vertical force measurement.

Description

Tire vertical force measuring device and measuring method Technical Field

[0001] The present invention relates to the field of vehicle engineering technology, and in particular to a tire vertical force measuring device and a measuring method. Background Art

[0002] Real-time measurement of tire vertical force is of great significance. By measuring tire vertical force, it not only accurately records tire usage and extends tire life, but also improves vehicle control smoothness and handling stability. Smart tires typically incorporate an internal sensor system to collect and transmit real-time signals such as tire ground strain and acceleration, thereby monitoring tire forces.

[0003] Existing tire vertical force measurement devices typically place an acceleration sensor on the outside of the tire, directly decipher information such as contact time based on the acceleration signal, and further calculate the tire vertical force. However, since the accuracy of the acceleration signal is easily affected by the external environment, large calculation errors are prone to occur, making it difficult to accurately measure the tire vertical force.

[0004] Summary of the Invention

[0005] The present invention provides a tire vertical force measurement device and a measurement method to solve the technical problem that the accuracy of the acceleration signal obtained by the acceleration sensor arranged on the outside of the tire is easily affected by the external environment, which is prone to large calculation errors and makes it difficult to accurately measure the tire vertical force.

[0006] The present invention provides a tire vertical force measuring device, comprising:

[0007] Strain sensing module, data transmission module and control module;

[0008] The strain sensing module and the data transmission module are both arranged on the inner side of the tire to be measured;

[0009] The strain sensing module is connected to the data transmission module, and the data transmission module is connected to the control module;

[0010] The strain sensing module includes a strain sensor, and the strain sensor includes an upper substrate made of rubber material, a lower substrate made of rubber material, a sensitive layer and a sensor terminal;

[0011] The sensitive layer is arranged between the upper substrate and the lower substrate, and the sensor terminals are arranged on both sides of the strain sensor;

[0012] The data transmission module is provided with a rubber sleeve housing;

[0013] The strain sensing module is used to obtain the strain waveform of the tire to be measured and transmit the strain waveform to the data transmission module;

[0014] The data transmission module is used to receive the strain waveform and transmit the strain waveform to the control module;

[0015] The control module is used to measure the vertical force of the tire according to the strain waveform to obtain the vertical force of the tire to be measured.

[0016] The present invention also provides a tire vertical force measurement method, which is applicable to the tire vertical force measurement device as described above, comprising:

[0017] Acquire the contact time and rotation cycle time of the tire to be measured based on the strain waveform acquired by the strain sensing module, and calculate the contact angle of the tire to be measured based on the contact time and the rotation cycle time;

[0018] Calculating a contact patch length of the tire to be measured based on the contact angle and the free rolling radius of the tire to be measured;

[0019] Calculating the speed of the tire to be measured according to the rotation cycle time, the diameter of the tire to be measured, and the sampling frequency of the strain sensor;

[0020] constructing a first dynamic model based on the contact patch length, the free rolling radius, the tire vertical force, and the tire vertical stiffness;

[0021] The vertical force of the tire to be measured is obtained by solving the problem according to the speed of the tire to be measured and the first dynamic model.

[0022] Furthermore, obtaining the contact time and rotation cycle time of the tire to be measured according to the strain waveform obtained by the strain sensing module includes:

[0023] Acquire multiple data points of the strain sensor according to the strain waveform acquired by the strain sensing module, and perform first-order derivative, second-order derivative, and third-order derivative on each data point;

[0024] When the second-order derivative of the n+2th data point multiplied by the second-order derivative of the previous or next point is less than or equal to 0, and the third-order derivative of the current data point is greater than 0, the current data point is placed in the first-order guide valley candidate data point set, and n is the first data point;

[0025] If the current data point is the last data point, clear the points whose first-order derivative is less than a set threshold in the first-order guide valley candidate data point set;

[0026] Starting from the first data point of the remaining data points in the first-order guided wave valley candidate data point set, a set width window is established, and the data point with the smallest first-order derivative is extracted according to the set width window to the first-order guided wave valley data point set until there are no remaining data points in the first-order guided wave valley candidate data point set;

[0027] Taking each data point in the first-order guided wave valley data point set as the right edge, establishing a set width window, and extracting the data point with the largest first-order derivative value in the first-order guided wave valley data point set from the first-order guided wave peak data point set according to the set width window;

[0028] Taking the data point in the first-order guided wave valley data point set as the starting point, set the current data point to a and the next data point to b. If a ≥ b, assign b to a, and b is the next data point. When b> a, data point c is the previous data point of a. If c= a, assign c to a, and c is the previous data point. When c> a, take a as the subsequent valley. Traverse all data points in the first-order guided wave valley data point set to obtain all subsequent valleys in the first-order valley data point set.

[0029] Taking the data point in the first-order guide wave peak data point set as the starting point, set the current data point to a and the previous data point to b. If a ≥ b, assign b to a, b is the previous data point, until b> a, data point c is the next data point of a, if c= a, assign c to a, c is the next data point, until c> a, a is used as the previous trough, traverse all data points in the first-order guide wave peak data point set, and obtain all previous troughs in the first-order guide wave peak data point set;

[0030] The contact time of the tire to be measured is determined according to the front trough and the rear trough.

[0031] Furthermore, the step of calculating the contact angle of the tire to be measured based on the contact time and the rotation cycle time includes:

[0032] The ratio of the contact time to the rotation cycle time is recorded as the contact ratio of the tire;

[0033] The contact angle of the tire to be measured is obtained by multiplying the contact ratio by the angle corresponding to the rotation cycle time, where the angle corresponding to the rotation cycle time is 360°.

[0034] Furthermore, the calculating of the contact patch length of the tire to be measured based on the contact angle and the free rolling radius of the tire to be measured includes:

[0035] The contact patch length of the tire to be measured is calculated according to the following formula:

[0036] l=R0*sinθ

[0037] C l =2l

[0038] Where, the contact patch half length, R0 is the free rolling radius, θ is half of the contact angle, C l is the ground footprint length.

[0039] Furthermore, calculating the speed of the tire to be measured according to the rotation cycle time, the diameter of the tire to be measured, and the sampling frequency of the strain sensor includes:

[0040] The speed of the tire to be measured is calculated according to the following formula:

[0041] Wherein, v is the speed of the tire to be measured, D is the diameter of the tire to be measured, f is the sampling frequency of the strain sensor, and L is the rotation cycle time of the tire to be measured.

[0042] Furthermore, the first kinetic model is:

[0043] Among them, C l is the contact patch length, R0 is the free radius, F z is the vertical force, C z is the vertical stiffness, k1 and k2 are the times to be fitted.

[0044] Furthermore, the solving and obtaining the tire vertical force of the tire to be measured based on the speed of the tire to be measured and the first dynamic model includes:

[0045] The first kinetic model is approximated as the second kinetic model as follows:

[0046] Wherein, P is tire pressure;

[0047] Substituting the tire speed into the second dynamic model for correction, the following third dynamic model is obtained:

[0048] The third dynamic model is solved to obtain the tire vertical force of the tire to be measured.

[0049] The present invention also provides a tire vertical force measuring device, comprising:

[0050] a contact angle calculation module, configured to obtain a contact time and a rotation cycle time of the tire to be measured based on the strain waveform obtained by the strain sensing module, and calculate a contact angle of the tire to be measured based on the contact time and the rotation cycle time;

[0051] a contact patch length calculation module, configured to calculate the contact patch length of the tire to be measured based on the contact angle and the free rolling radius of the tire to be measured;

[0052] a tire speed calculation module, configured to calculate the speed of the tire to be measured based on the rotation cycle time, the diameter of the tire to be measured, and the sampling frequency of the strain sensor;

[0053] a dynamic model construction module, configured to construct a first dynamic model based on the contact patch length, the free rolling radius, the tire vertical force, and the tire vertical stiffness;

[0054] The tire vertical force solving module is used to solve and obtain the tire vertical force of the tire to be measured according to the speed of the tire to be measured and the first dynamic model.

[0055] The present invention also provides a storage medium, which includes a stored computer program, wherein when the computer program is running, the device where the storage medium is located is controlled to execute the tire vertical force measurement method as described above.

[0056] The present invention provides a strain sensor on the inner side of the tire. The rubber upper and lower bases of the strain sensor enable the strain sensor to strain synchronously with the tire, thereby accurately reflecting the strain condition of the tire based on the strain waveform of the strain sensor. In addition, the ground contact area waveform is obvious in the strain waveform output by the strain sensor. The ground contact time and rotation cycle time of the tire can be accurately calculated based on the data points of the ground contact area waveform. Furthermore, the vertical force of the tire can be accurately calculated based on the ground contact time and rotation cycle time of the tire, thereby effectively improving the accuracy of the tire vertical force measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] FIG1 is a schematic structural diagram of a tire vertical force measuring device provided by an embodiment of the present invention;

[0058] FIG2 is a schematic structural diagram of a sensor module provided by an embodiment of the present invention;

[0059] FIG3 is a schematic diagram of the structure of an acquisition circuit of a strain sensor provided by an embodiment of the present invention;

[0060] FIG4 is a comparison diagram of strain waveforms of a tire contact process strain sensor and an acceleration sensor provided by an embodiment of the present invention.

[0061] FIG5 is a schematic diagram of an output waveform of a strain sensor provided by an embodiment of the present invention;

[0062] FIG6 is a schematic flow chart of a tire vertical force measurement method provided by an embodiment of the present invention;

[0063] FIG7 is a schematic diagram of a grounding point identification algorithm flow diagram provided by an embodiment of the present invention;

[0064] FIG8 is another schematic structural diagram of a tire vertical force measuring device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0066] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0067] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0068] Referring to FIG1 , one embodiment of the present invention provides a tire vertical force measuring device, comprising:

[0069] Strain sensing module 1, data transmission module 2 and control module 3;

[0070] The strain sensing module 1 and the data transmission module 2 are both arranged on the inner side of the tire 5 to be measured;

[0071] In an embodiment of the present invention, the strain sensing module 1 is attached to the inner side of the tire so that the modulus of the strain sensing module 1 is close to that of the tire inner tread material, thereby accurately detecting the strain degree of the tire and outputting an accurate strain waveform.

[0072] The strain sensing module 1 is connected to the data transmission module 2, and the data transmission module 2 is connected to the control module 3;

[0073] In the embodiment of the present invention, the strain sensing module 1 may be connected to the data transmission module 2 via a wire 4 .

[0074] Please refer to FIG2 , the strain sensing module 1 includes a strain sensor, which includes an upper substrate made of rubber material, a lower substrate made of rubber material, a sensitive layer, and sensor terminals;

[0075] In the embodiment of the present invention, the upper and lower substrates made of rubber material can cause the strain sensor to strain synchronously with the tire, thereby accurately reflecting the strain condition of the tire according to the strain waveform of the strain sensor.

[0076] The sensitive layer is arranged between the upper substrate and the lower substrate, and the sensor terminals are arranged on both sides of the strain sensor;

[0077] The data transmission module 2 is provided with a rubber sleeve housing 21;

[0078] In this embodiment of the present invention, the rubber housing 21 is primarily used to support the hardware module and is bonded to the tire. The tire vertical force measurement device may also include a battery module, which is primarily used to power the tire vertical force measurement device and may be an automotive-grade button cell battery.

[0079] In the embodiment of the present invention, the data transmission module 2 includes a fixed-value voltage-dividing resistor, an ADC module, an air pressure sensor, a Bluetooth module, and an antenna.

[0080] The strain sensing module 1 is used to obtain the strain waveform of the tire 5 to be measured and transmit the strain waveform to the data transmission module 2;

[0081] In an embodiment of the present invention, the strain sensor is provided with an acquisition circuit to obtain the strain waveform of the tire 5 to be measured. Please refer to FIG3 , which is a schematic structural diagram of a built-in acquisition circuit of a strain sensor provided in an embodiment of the present invention.

[0082] The data transmission module 2 is used to receive the strain waveform and transmit the strain waveform to the control module 3;

[0083] In the embodiment of the present invention, the data transmission module 2 transmits the waveform data to the control module 3 via a Bluetooth wireless transmission signal.

[0084] The control module 3 is used to measure the tire vertical force according to the strain waveform to obtain the tire vertical force of the tire 5 to be measured.

[0085] Please refer to FIG4 , which is a comparison diagram of strain waveforms of a strain sensor and an acceleration sensor during tire contacting process according to an embodiment of the present invention.

[0086] Referring to FIG. 5 , in an embodiment of the present invention, the strain waveform output by the strain sensor can accurately reflect the strain condition of the tire. The different waveforms of the tire in the entry zone, contact zone, and exit zone can be identified from the strain waveform. Furthermore, the strain waveform is composed of a plurality of strain data points. Based on the data points of the strain waveform, the vertical force of the tire 5 to be measured can be calculated.

[0087] In the embodiment of the present invention, a strain sensor is provided on the inner side of the tire. The strain waveform output by the strain sensor has a distinct contact zone waveform. Based on the data points of the contact zone waveform, the tire's contact time and rotation cycle time can be accurately calculated. Furthermore, the tire's vertical force can be accurately calculated based on the tire's contact time and rotation cycle time, effectively improving the accuracy of tire vertical force measurement.

[0088] Referring to FIG. 6 , the present invention provides a tire vertical force measurement method, applicable to the tire vertical force measurement device described above, comprising:

[0089] S1. Obtaining the contact time and rotation cycle time of the tire to be measured based on the strain waveform obtained by the strain sensing module, and calculating the contact angle of the tire to be measured based on the contact time and rotation cycle time;

[0090] In this embodiment of the present invention, tire calibration testing involves conducting uniform rolling tests on a test bench under varying loads, tire pressures, and speeds to obtain relevant data. During calibration, strain sensors are placed inside the tire to monitor its ground contact deformation.

[0091] The strain sensor outputs a waveform corresponding to the rotation of the tire. The contact time and rotation cycle time of the tire to be measured can be obtained based on the sensor output waveform.

[0092] S2. Calculating the contact patch length of the tire to be measured based on the contact angle and the free rolling radius of the tire to be measured;

[0093] In the embodiment of the present invention, the free rolling radius of the tire can be obtained by direct measurement, and the contact patch length of the tire can be calculated based on the contact angle and the free rolling radius using a trigonometric function relationship.

[0094] S3. Calculate the speed of the tire to be measured based on the rotation cycle time, the diameter of the tire to be measured, and the sampling frequency of the strain sensor;

[0095] S4. constructing a first dynamic model based on the contact patch length, the free rolling radius, the tire vertical force, and the tire vertical stiffness;

[0096] S5. Obtain the tire vertical force of the tire to be measured based on the speed of the tire to be measured and the first dynamic model.

[0097] The embodiment of the present invention is based on a calibration test on the tire to obtain a strain waveform output by the strain sensor according to the tire strain condition, and calculates the tire's contact patch length and speed based on the strain waveform. Based on the contact patch length, free rolling radius, tire vertical force and tire vertical stiffness, a first dynamic model is constructed. According to the speed of the tire to be measured and the first dynamic model, the tire vertical force of the tire to be measured is solved. The touchdown point can be accurately identified and the touchdown time can be determined based on the data during the tire calibration test, and it is not affected by external conditions such as tire speed, thereby effectively reducing calculation errors and effectively improving the accuracy of tire vertical force measurement.

[0098] In an embodiment of the present invention, a strain sensor is attached to the interior of the tire, having a modulus close to that of the tire's inner tread material. This allows for in-situ detection of the tire's strain level, thereby enabling a clear and distinct strain waveform output by the sensor when the tire touches the ground. This allows for accurate identification of the touchdown point at both high and low speeds, without being affected by the tire's travel speed. This effectively improves the accuracy of tire vertical force measurements.

[0099] In one embodiment, S1, obtaining the contact time and rotation cycle time of the tire to be measured based on the strain waveform obtained by the strain sensing module, includes:

[0100] S11. Acquire multiple data points of the strain sensor according to the strain waveform acquired by the strain sensing module, and perform first-order derivative, second-order derivative, and third-order derivative on each data point;

[0101] S12. When the product of the second-order derivative of the n+2th data point and the second-order derivative of the previous or next point is less than or equal to 0, and the third-order derivative of the current data point is greater than 0, the current data point is placed in the first-order guide valley candidate data point set, and n is the first data point;

[0102] S13. If the current data point is the last data point, clear the points whose first-order derivative is less than the set threshold in the first-order guide wave valley candidate data point set; if the current data point is not the last data point, return to step S12 for the next data point until the last data point is executed.

[0103] S14, starting from the first data point of the remaining data points in the first-order guided wave valley candidate data point set, establishing a set width window, and extracting the data point with the smallest first-order derivative according to the set width window to the first-order guided wave valley data point set until there are no remaining data points in the first-order guided wave valley candidate data point set;

[0104] S15, taking each data point in the first-order guided wave valley data point set as the right edge, establishing a set width window, and extracting the data point with the largest first-order derivative value from the first-order guided wave valley data point set and the first-order guided wave peak data point set according to the set width window;

[0105] S16, starting from a data point in the first-order guided wave valley data point set, setting the current data point to a and the next data point to b, if a ≥ b, assigning b to a, b is the next data point, until b> a, data point c is the previous data point of a, if c=a, assigning c to a, c is the previous data point, until c> a, taking a as the next valley, traversing all data points in the first-order guided wave valley data point set, and obtaining all next valleys in the first-order valley data point set;

[0106] S17, starting from a data point in the first-order guide wave peak data point set, setting the current data point to a and the previous data point to b, if a ≥ b, assigning b to a, b as the previous data point, until b> a, data point c is the next data point of a, if c= a, assigning c to a, c as the next data point, until c> a, with a as the previous trough, traversing all data points in the first-order guide wave peak data point set, and obtaining all previous troughs in the first-order guide wave peak data point set;

[0107] S18. Determine the contact time of the tire to be measured according to the front trough and the rear trough.

[0108] Please refer to FIG7 , which is a schematic flow chart of a grounding point identification algorithm provided by an embodiment of the present invention.

[0109] In one embodiment, step S1, calculating the contact angle of the tire to be measured based on the contact time and the rotation cycle time, includes:

[0110] S101, recording the ratio of the contact time to the rotation cycle time as the contact ratio of the tire;

[0111] S102: Multiply the contact angle ratio by the angle corresponding to the rotation cycle time to obtain the contact angle of the tire to be measured. The angle corresponding to the rotation cycle time is 360°.

[0112] In the embodiment of the present invention, the contact ratio of the tire can be determined according to the contact time and the rotation cycle time, thereby further determining the contact angle of the tire.

[0113] In one embodiment, step S2, calculating the contact patch length of the tire to be measured based on the contact angle and the free rolling radius of the tire to be measured, includes:

[0114] The contact patch length of the tire to be measured is calculated using the following formula:

[0115] l=R0*sinθ

[0116] C l =2l

[0117] Where, the contact patch half length, R0 is the free rolling radius, θ is half of the contact angle, C l is the ground footprint length.

[0118] In one embodiment, step S3, calculating the speed of the tire to be measured based on the rotation cycle time, the diameter of the tire to be measured, and the sampling frequency of the strain sensor, includes:

[0119] The speed of the tire to be measured is calculated according to the following formula:

[0120] Where v is the speed of the tire to be measured, D is the diameter of the tire to be measured, f is the sampling frequency of the strain sensor, and L is the rotation cycle time of the tire to be measured.

[0121] In one embodiment, the first kinetic model is:

[0122] Among them, C l is the contact patch length, R0 is the free radius, F z is the vertical force, C z is the vertical stiffness, k1 and k2 are the times to be fitted.

[0123] The dynamic model in the embodiment of the present invention may be a Swift Tire dynamic model. In this embodiment of the present invention, the load, tire pressure, speed, free rolling radius, and contact patch length may be substituted into the Swift Tire dynamic model to output a calibration relationship between contact patch length and load. The relationship includes factors such as speed and tire pressure that affect contact patch length.

[0124] In one embodiment, step S5, solving and obtaining the tire vertical force of the tire to be measured based on the speed of the tire to be measured and the first dynamic model, includes:

[0125] S51, approximating the first kinetic model to the following second kinetic model:

[0126] Wherein, P is tire pressure;

[0127] In the embodiment of the present invention, since the vertical stiffness of the tire is mainly determined by the tire pressure, the first dynamic model can be approximated as the second dynamic model.

[0128] S52: Substitute the tire speed into the second dynamic model for correction to obtain the following third dynamic model:

[0129] In the embodiment of the present invention, as the speed changes, the contact patch length will also change. By introducing the tire speed into the second dynamic model, a modified third dynamic model can be obtained.

[0130] S53: Solve the third dynamic model to obtain the tire vertical force of the tire to be measured.

[0131] In the embodiment of the present invention, the obtained parameters or known parameters are substituted into the third dynamic model to obtain the tire vertical force of the tire to be measured.

[0132] In an embodiment of the present invention, parameters such as contact patch length, tire speed, tire pressure, tire free rolling radius, vertical stiffness, and parameters to be fitted are substituted into the third dynamic model to obtain an accurate tire vertical force of the tire to be measured.

[0133] The implementation of the embodiments of the present invention has the following beneficial effects:

[0134] The embodiment of the present invention calculates the tire's contact patch length and speed based on data from a tire calibration test, and constructs a first dynamic model based on the contact patch length, free rolling radius, tire vertical force, and tire vertical stiffness. The tire vertical force of the tire to be measured is solved based on the speed of the tire to be measured and the first dynamic model. This embodiment can accurately identify the touchdown point and determine the touchdown time based on the data from the tire calibration test, without being affected by external conditions such as tire speed. This effectively reduces calculation errors and further improves the accuracy of tire vertical force measurement.

[0135] Furthermore, the embodiment of the present invention considers the influencing factors of tire pressure, approximates the first dynamic model to a second dynamic model, and substitutes the tire speed into the second dynamic model for correction to obtain a third dynamic model. This fully considers the various factors that affect the measurement of tire vertical force, thereby further improving the accuracy of tire vertical force measurement.

[0136] Referring to FIG. 6 , based on the same inventive concept as the above embodiment, the present invention further provides a tire vertical force measuring device, comprising:

[0137] A contact angle calculation module 10 is configured to obtain the contact time and rotation cycle time of the tire to be measured based on the strain waveform obtained by the strain sensing module, and calculate the contact angle of the tire to be measured based on the contact time and rotation cycle time;

[0138] A contact patch length calculation module 20 is configured to calculate the contact patch length of the tire to be measured based on the contact angle and the free rolling radius of the tire to be measured;

[0139] A tire speed calculation module 30 is configured to calculate the speed of the tire to be measured based on the rotation cycle time, the diameter of the tire to be measured, and the sampling frequency of the strain sensor;

[0140] A dynamic model building module 40 is configured to build a first dynamic model based on the contact patch length, the free rolling radius, the tire vertical force, and the tire vertical stiffness;

[0141] The tire vertical force solving module 50 is used to solve and obtain the tire vertical force of the tire to be measured according to the speed of the tire to be measured and the first dynamic model.

[0142] In one embodiment, the touchdown angle calculation module 10 is further configured to:

[0143] According to the strain waveform obtained by the strain sensing module, multiple data points of the strain sensor are obtained, and the first-order derivative, the second-order derivative and the third-order derivative are respectively performed on each data point;

[0144] When the second-order derivative of the n+2th data point multiplied by the second-order derivative of the previous or next point is less than or equal to 0, and the third-order derivative of the current data point is greater than 0, the current data point is placed in the first-order guide valley candidate data point set, and n is the first data point;

[0145] If the current data point is the last data point, clear the points whose first-order derivative is less than the set threshold in the first-order guide valley candidate data point set;

[0146] Starting from the first data point of the remaining data points in the first-order guided wave valley candidate data point set, a set width window is established, and the data point with the smallest first-order derivative is extracted according to the set width window to the first-order guided wave valley data point set until there are no remaining data points in the first-order guided wave valley candidate data point set;

[0147] Taking each data point in the first-order guided wave valley data point set as the right edge, a set width window is established, and the data point with the largest first-order derivative value in the first-order guided wave valley data point set is extracted from the first-order guided wave peak data point set according to the set width window;

[0148] Taking the data point in the first-order guided wave valley data point set as the starting point, set the current data point to a and the next data point to b. If a ≥ b, assign b to a, and b is the next data point. When b> a, the data point c is the previous data point of a. If c= a, assign c to a, and c is the previous data point. When c> a, a is taken as the subsequent valley. Traverse all the data points in the first-order guided wave valley data point set to obtain all the subsequent valleys in the first-order valley data point set.

[0149] Taking the data point in the first-order guide wave peak data point set as the starting point, set the current data point to a and the previous data point to b. If a ≥ b, assign b to a, b is the previous data point, until b> a, data point c is the next data point of a, if c= a, assign c to a, c is the next data point, until c> a, a is used as the previous trough, traverse all data points in the first-order guide wave peak data point set, and obtain all previous troughs in the first-order guide wave peak data point set;

[0150] The contact time of the tire to be measured is determined based on the front trough and the rear trough.

[0151] In one embodiment, the touchdown angle calculation module 10 is further configured to:

[0152] The ratio of the contact time to the rotation cycle time is recorded as the contact ratio of the tire;

[0153] The contact angle of the tire to be measured is obtained by multiplying the contact ratio by the angle corresponding to the rotation cycle time. The angle corresponding to the rotation cycle time is 360°.

[0154] In one embodiment, the contact patch length calculation module 20 is further configured to:

[0155] The contact patch length of the tire to be measured is calculated using the following formula:

[0156] l=R0*sinθ

[0157] C l =2l

[0158] Where, the contact patch half length, R0 is the free rolling radius, θ is half of the contact angle, C l is the ground footprint length.

[0159] In one embodiment, the tire speed calculation module 30 is further configured to:

[0160] The speed of the tire to be measured is calculated according to the following formula:

[0161] Where v is the speed of the tire to be measured, D is the diameter of the tire to be measured, f is the sampling frequency of the strain sensor, and L is the rotation cycle time of the tire to be measured.

[0162] In one embodiment, the first kinetic model is:

[0163] Among them, C l is the contact patch length, R0 is the free radius, F z is the vertical force, C z is the vertical stiffness, k1 and k2 are the times to be fitted.

[0164] In one embodiment, the tire vertical force solving module 50 is further configured to:

[0165] The first kinetic model is approximated as the second kinetic model as follows:

[0166] Wherein, P is tire pressure;

[0167] Substituting the tire speed into the second dynamic model for correction, we obtain the following third dynamic model:

[0168] The third dynamic model is solved to obtain the tire vertical force of the tire to be measured.

[0169] The present invention also provides a storage medium, which includes a stored computer program, wherein when the computer program is running, the device where the storage medium is located is controlled to execute the tire vertical force measurement method as described above.

[0170] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A tire vertical force measuring device, characterized in that, Comprising: A strain sensing module, a data transmission module, and a control module; Both the strain sensing module and the data transmission module are disposed on the inner side of the tire to be measured; The strain sensing module is connected to the data transmission module, and the data transmission module is connected to the control module; The strain sensing module includes strain sensors, and each strain sensor includes an upper substrate made of rubber, a lower substrate made of rubber, a sensitive layer, and sensor terminals; The sensitive layer is disposed between the upper substrate and the lower substrate, and the sensor terminals are disposed on both sides of the strain sensor; The data transmission module is provided with a rubber sleeve housing; The strain sensing module is configured to acquire a strain waveform of the tire to be measured and transmit the strain waveform to the data transmission module; The data transmission module is configured to receive the strain waveform and transmit the strain waveform to the control module; The control module is configured to measure the tire vertical force according to the strain waveform to obtain the tire vertical force of the tire to be measured.

2. A method for measuring the vertical force of a tire, characterized in that, Applicable to the tire vertical force measuring device according to claim 1, comprising: Obtaining the grounding time and the rotation period time of the tire to be measured according to the strain waveform acquired by the strain sensing module, and calculating the grounding angle of the tire to be measured according to the grounding time and the rotation period time; Calculating the grounding imprint length of the tire to be measured according to the grounding angle and the free rolling radius of the tire to be measured; Calculating the speed of the tire to be measured according to the rotation period time, the diameter of the tire to be measured, and the sampling frequency of the strain sensor; Constructing a first dynamic model based on the grounding imprint length, the free rolling radius, the tire vertical force, and the tire vertical stiffness; Solving to obtain the tire vertical force of the tire to be measured according to the speed of the tire to be measured and the first dynamic model.

3. The tire vertical force measurement method according to claim 2, characterized in that The obtaining the grounding time and the rotation period time of the tire to be measured according to the strain waveform acquired by the strain sensing module includes: Obtaining a plurality of data points of the strain sensor according to the strain waveform acquired by the strain sensing module, and respectively performing first-order differentiation, second-order differentiation, and third-order differentiation on each data point; When the product of the second derivative of the (n + 2)-th data point and the second derivative of the previous or next data point is less than or equal to 0, and the third derivative of the current data point is greater than 0, putting the current data point into the first derivative valley candidate data point set, where n is the first data point; If the current data point is the last data point, clearing the points in the first derivative valley candidate data point set whose first derivative is less than a set threshold; Starting from the first data point of the remaining data points in the first derivative valley candidate data point set, establishing a set-width window, and extracting the data point with the minimum first derivative into the first derivative valley data point set according to the set-width window until there are no remaining data points in the first derivative valley candidate data point set; Taking each data point in the set of first-order derivative wave valley data points as the right edge, a window with a set width is established, and the data point value with the largest first-order derivative value in the set of first-order derivative wave valley data points is extracted according to the window with the set width into the set of first-order derivative wave peak data points; Taking the data points in the set of first-order derivative wave valley data points as the starting point, setting the current data point as a and the next data point as b. If a ≥ b, assign b to a, and b is the next data point. Until b > a, the data point c is the previous data point of a. If c = a, assign c to a, and c is the previous data point. Until c > a, take a as the trailing wave valley, and traverse all the data points in the set of first-order derivative wave valley data points to obtain all the trailing wave valleys in the set of first-order derivative wave valley data points; Taking the data points in the set of first-order derivative wave peak data points as the starting point, setting the current data point as a and the previous data point as b. If a ≥ b, assign b to a, and b is the previous data point. Until b > a, the data point c is the next data point of a. If c = a, assign c to a, and c is the next data point. Until c > a, take a as the leading wave valley, and traverse all the data points in the set of first-order derivative wave peak data points to obtain all the leading wave valleys in the set of first-order derivative wave peak data points; Determine the grounding time of the tire to be measured according to the leading wave valley and the trailing wave valley; 4. The tire vertical force measurement method according to claim 2, wherein, The calculating the grounding angle of the tire to be measured according to the grounding time and the rotation period time includes: Denote the ratio of the grounding time to the rotation period time as the grounding ratio of the tire; Multiply the grounding ratio by the angle corresponding to the rotation period time to obtain the grounding angle of the tire to be measured, and the angle corresponding to the rotation period time is 360°; 5. The tire vertical force measurement method according to claim 2, wherein, The calculating the grounding mark length of the tire to be measured according to the grounding angle and the free rolling radius of the tire to be measured includes: Calculate the grounding mark length of the tire to be measured according to the following formula: l = R0 * sinθ C l ＝2l Among them, the half-length of the ground contact mark, R0 is the free rolling radius, θ is half of the ground contact angle, and C l is the length of the ground contact mark.

6. The tire vertical force measurement method according to claim 2, characterized in that, Calculate the speed of the tire to be measured according to the rotation period time, the diameter of the tire to be measured, and the sampling frequency of the strain sensor, including: The speed of the tire to be measured is calculated according to the following formula: Where, v is the speed of the tire to be measured, D is the diameter of the tire to be measured, f is the sampling frequency of the strain sensor, and L is the rotation period time of the tire to be measured; 7. The tire vertical force measurement method according to claim 2, characterized in that, The first kinetic model is as follows: Among them, C l is the length of the grounding impression, R0 is the free radius, F z is the vertical force, C z is the vertical stiffness, and k1, k2 are the fitting times to be determined.

8. The tire vertical force measurement method according to claim 7, characterized in that, The solving for the tire vertical force of the tire to be measured according to the speed of the tire to be measured and the first dynamic model includes: Approximate the first kinetic model as the following second kinetic model: Where, P is the tire pressure; Substitute the speed of the tire into the second kinetic model for correction to obtain the following third kinetic model: Solve the third dynamic model to obtain the tire vertical force of the tire to be measured; 9. A tire vertical force measuring device, characterized in that, Including: A grounding angle calculation module, configured to obtain the grounding time and the rotation period time of the tire to be measured according to the strain waveform acquired by the strain sensing module, and calculate the grounding angle of the tire to be measured according to the grounding time and the rotation period time; A grounding mark length calculation module, configured to calculate the grounding mark length of the tire to be measured according to the grounding angle and the free rolling radius of the tire to be measured; A tire speed calculation module, configured to calculate the speed of the tire to be measured based on the rotation period time, the diameter of the tire to be measured, and the sampling frequency of the strain sensor; A dynamic model construction module, configured to construct a first dynamic model based on the ground contact patch length, the free rolling radius, the tire vertical force, and the tire vertical stiffness; A tire vertical force solving module, configured to solve the tire vertical force of the tire to be measured according to the speed of the tire to be measured and the first dynamic model. The storage medium includes a stored computer program, wherein when the computer program runs, it controls the device where the storage medium is located to execute a method for measuring tire vertical force according to any one of claims 2 to 8.

10. A storage medium, characterized in that, ​

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