A method, device and system for measuring tire slip ratio based on inertia sensing signals

Abstract

This invention relates to the field of intelligent tire condition sensing and vehicle operation safety monitoring technology, and discloses a method, apparatus, and system for calculating tire slip ratio based on inertial sensing signals. The method is executed by a processor. By acquiring radial acceleration signals from an accelerometer installed in the tire's inner liner and rolling angular velocity signals from a gyroscope, the non-grounding intervals within the tire's rolling cycle are determined. Within these non-grounding intervals, the tire's linear velocity is determined based on the relationship that radial acceleration in circular motion equals the product of linear velocity and angular velocity. After correction, the tire slip ratio is calculated in conjunction with the vehicle's speed. This invention does not rely on tire radius parameters, fundamentally avoiding the calculation errors caused by radius uncertainty in traditional methods, and can accurately calculate tire slip ratio in real time.

Description

Technical Field

[0001] This invention relates to the field of intelligent tire condition perception and vehicle operation safety monitoring technology, specifically to a method, device, and system for calculating tire slip ratio based on inertial sensing signals. Background Technology

[0002] With the development of the automotive industry and the continuous improvement of vehicle safety performance requirements, accurate detection of tire slip ratio is of great significance for vehicle driving safety. Existing tire slip ratio detection methods mainly obtain tire rotation speed through wheel speed sensors, then combine this with tire radius parameters to calculate tire linear velocity, and finally calculate the slip ratio. However, the dynamic radius of a tire is not a fixed value, but is constantly changing due to the combined influence of various factors such as vehicle load, tire pressure, ambient temperature, driving speed, and wear. Whether using a factory-set fixed radius value or correcting the radius using empirical formulas, existing technologies struggle to accurately reflect the tire's real-time radius, leading to significant errors in the tire linear velocity calculation results, directly affecting the accuracy of slip ratio measurement. Excessive slip ratio measurement errors not only reduce the responsiveness of the vehicle's anti-skid control system but may also create safety hazards during emergency braking or driving conditions.

[0003] Therefore, there is an urgent need for a tire slip ratio calculation technology that does not rely on tire radius parameters, in order to improve the accuracy and reliability of slip ratio detection. Summary of the Invention

[0004] This invention provides a method for calculating tire slip ratio based on inertial sensing signals, executed by a processor, comprising: S1: Acquire the radial acceleration signal from the tire liner accelerometer and the rolling angular velocity signal from the gyroscope; S2: Based on the time-domain waveform characteristics of the radial acceleration signal, determine the non-grounded interval in the tire rolling cycle; S3: Within the non-grounded zone, the tire linear velocity at the sensor mounting position is determined by the radial acceleration and rolling angular velocity, based on the product relationship between radial acceleration, linear velocity, and angular velocity. S4: Based on the distance parameter between the accelerometer and the tire tread, the tire linear velocity at the sensor is corrected to obtain the tire linear velocity at the tread. S5: Obtain vehicle speed; S6: Calculate the slip ratio based on the tire linear velocity at the tread and the vehicle speed.

[0005] Preferably, the step of determining the non-grounded interval includes: performing time-domain waveform analysis on the radial acceleration signal to detect the ground peak and the off-ground peak; determining the interval between the ground peak and the off-ground peak as the grounded interval; determining the interval in the tire rolling cycle that is outside the grounded interval and whose time-domain waveform of the radial acceleration signal meets a preset stability condition as the non-grounded interval; wherein, the preset stability condition is that the fluctuation of the radial acceleration signal within a set time window is less than or equal to a preset fluctuation threshold.

[0006] Further preferably, the step of determining the tire linear velocity at the sensor installation location includes: dividing the sampled value of the radial acceleration signal within the non-grounded interval by the sampled value of the rolling angular velocity signal at the same moment to obtain the tire linear velocity at the corresponding moment; the product relationship is... , where a is the radial acceleration, v is the tire linear velocity, and ω is the rolling angular velocity.

[0007] More preferably, the step of correcting the tire linear velocity at the tread includes: obtaining the radial distance parameter between the sensor mounting position and the tread; multiplying the distance parameter by the value of the rolling angular velocity signal to obtain a speed correction amount; and adding the tire linear velocity at the sensor mounting position to the speed correction amount to obtain the tire linear velocity at the tread.

[0008] More preferably, the accelerometer and the gyroscope are integrated into the same multi-axis sensing chip, which is attached to the middle position of the tire inner liner along the width direction. The radial sensing axis of the accelerometer is arranged along the radial direction of the tire, and the rolling sensing axis of the gyroscope is arranged along the rolling axis of the tire.

[0009] More preferably, the sampling frequency of the radial acceleration signal and the rolling angular velocity signal is 100-5000Hz.

[0010] More preferably, the step of obtaining the vehicle speed includes: The vehicle's speed is obtained through an onboard GPS receiver. Using its second pulse signal as a unified time reference, the vehicle's driving speed, radial acceleration signal, and rolling angular velocity signal are synchronized in time.

[0011] Further preferred options include: The tire slip ratio is compared with a preset threshold; a slip warning signal is generated when the preset threshold is exceeded. The slip warning signal is sent to the vehicle brake control unit to perform braking intervention and power torque adjustment.

[0012] A device for calculating tire slip ratio based on inertial sensing signals, applied to the method described in any of the above-mentioned methods, includes: a signal acquisition module for acquiring radial acceleration signals from an accelerometer in the tire liner and rolling angular velocity signals from a gyroscope; an interval determination module for determining a non-grounded interval in the tire rolling cycle based on the time-domain waveform characteristics of the radial acceleration signals; a speed calculation module for determining the tire linear velocity at the sensor mounting position within the non-grounded interval based on the product relationship between radial acceleration, linear velocity, and angular velocity; a speed correction module for correcting the tire linear velocity at the tread based on the distance parameter between the accelerometer and the tread; a vehicle speed acquisition module for acquiring the vehicle speed; and a slip ratio calculation module for calculating the tire slip ratio based on the tire linear velocity at the tread and the vehicle speed.

[0013] A system for calculating tire slip ratio based on inertial sensing signals includes: a sensing unit comprising an accelerometer and a gyroscope, both mounted on the inner liner of the tire, for acquiring radial acceleration and rolling angular velocity signals, respectively; a vehicle speed detection unit for detecting vehicle speed; a processing unit communicatively connected to the sensing unit and the vehicle speed detection unit for executing the method described above; and a warning output unit communicatively connected to the processing unit for generating a slip warning signal based on the tire slip ratio output by the processing unit.

[0014] Technical effects: This invention is based on the relationship that radial acceleration in circular motion equals the product of linear velocity and angular velocity. By using an accelerometer and gyroscope installed in the tire's inner liner to directly acquire radial acceleration and rolling angular velocity, the tire's linear velocity can be calculated. This fundamentally eliminates the dependence on tire radius parameters and completely avoids the speed calculation errors caused by changes in the tire's dynamic radius due to factors such as load, temperature, and air pressure, which are common in traditional methods. This solution utilizes the basic physical principles of circular motion and achieves direct tire speed calculation through simple algebraic operations. It involves minimal computation, has a fast response time, and can accurately measure tire slip ratio in real time, providing reliable technical support for vehicle driving safety. Attached Figure Description

[0015] Figure 1 This is a flowchart of a method for calculating tire slip ratio based on inertia sensor signals. Figure 2 This is a block diagram of the system structure for calculating tire slip ratio based on inertia sensor signals. Figure 3 This is a schematic diagram of the time-domain waveform of the radial acceleration signal during the tire rolling cycle. Figure 4 This is a timing diagram of a system for calculating tire slip ratio based on inertia sensor signals. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] Traditional methods rely on tire radius to estimate speed, which results in significant errors.

[0018] Based on this, please refer to Figures 1-4 This invention provides a method for calculating tire slip ratio based on inertial sensing signals. In this scheme, executed by a processor, radial acceleration signals are acquired from an accelerometer installed in the tire's inner liner, and rolling angular velocity signals are acquired from a gyroscope. An accelerometer is a sensing element capable of measuring acceleration. It detects the displacement or stress changes of a mass under acceleration and converts the physical quantity of acceleration into an electrical signal output. An accelerometer can measure acceleration components in multiple directions; this scheme uses the radial acceleration component, i.e., acceleration along the tire's radius. A gyroscope is a sensing element capable of measuring angular velocity. It detects the Coriolis force or other physical effects generated by rotational motion and converts the physical quantity of angular velocity into an electrical signal output. A gyroscope can measure angular velocity components around multiple axes; this scheme uses the angular velocity component around the tire's rolling axis, i.e., the angular velocity of the tire's rolling motion. The accelerometer and gyroscope are installed in the tire's inner liner and roll with the tire, allowing direct measurement of the tire's own motion state without the need for indirect calculation using sensors on the vehicle's side. The tire liner is a rubber layer inside the tire, near the rim. It has a certain thickness and strength, making it suitable for mounting sensors. The advantage of mounting sensors inside the tire is that the sensor is rigidly connected to the tire, ensuring complete synchronization of movement, and the measurement results directly reflect the tire's actual motion.

[0019] The accelerometer and gyroscope are integrated on the same chip. The integrated multi-axis sensor chip fabricates the accelerometer and gyroscope sensing units on the same semiconductor substrate, sharing the same package and interface circuitry, resulting in small size, light weight, low power consumption, and good consistency. The integrated chip is typically only a few millimeters square, and its impact on tire dynamic balance is negligible. The adhesive mounting method uses a rubber-specific adhesive to fix the sensor chip to the surface of the tire's inner liner, ensuring a tight fit between the sensor and the tire's inner wall. This allows the sensor to deform and vibrate with the tire, transmitting tire motion information. The installation position is chosen at the middle of the tire's width, near the centerline of the tire tread. During tire rolling, the deformation at this position is most uniform, and the stress state is most symmetrical, reflecting the overall motion of the tire. The deformation characteristics of the tire shoulder and sidewall differ from those of the center of the tread, potentially introducing additional vibration components and affecting the representativeness of the measurement results.

[0020] The radial sensing axis of the accelerometer is set along the radial direction of the tire, and the rolling sensing axis of the gyroscope is set along the rolling axis of the tire. The sensing axis is the direction in which the sensor is most sensitive to the corresponding physical quantity. Only when the direction of the measured physical quantity is consistent with the direction of the sensing axis will the measurement result match the true value. If there is an angle between the direction of the sensing axis and the measured direction, the measured value will be the projection of the true physical quantity onto the direction of the sensing axis, introducing measurement deviation. Therefore, the direction of the sensing axes needs to be calibrated during installation to ensure that the radial sensing axis coincides with the radial direction of the tire, and the rolling sensing axis coincides with the rolling axis of the tire. Radial refers to the direction from the center of tire rotation towards the tread, and the rolling axis refers to the central axis around which the tire rotates. Calibration can be performed by rotating the tire under static conditions and observing the change in the sensor output signal to determine if the sensing axis direction is correct.

[0021] Based on the time-domain waveform characteristics of the radial acceleration signal, the non-grounded intervals in the tire rolling cycle are determined. During tire rolling, the motion state of any point on the tire changes continuously with time. When the point is in a non-grounded state, it moves in an approximate circular motion with the tire, and the force it experiences is mainly centrifugal force. The radial acceleration is mainly composed of centripetal acceleration, and its value is relatively stable with a relatively flat waveform. When the point enters a grounded state, the tire contacts the ground and is subjected to the normal and tangential forces of the ground. The tire tread undergoes compression deformation, and the motion state of the point is no longer pure circular motion. The radial acceleration is superimposed with the ground impact component and the tire deformation vibration component, resulting in a significant abrupt change in the waveform. A positive impact peak is generated at the moment of ground contact because the tire suddenly contacts the ground from a non-grounded state, causing a sudden change in the velocity direction and generating impact acceleration. A significant acceleration abrupt change also occurs at the moment of ground lift-off because the ground constraint force suddenly disappears, the tire deformation recovers, and the acceleration returns from a constrained state to a free circular motion state.

[0022] The time interval between the moment corresponding to the ground contact peak and the moment corresponding to the moment corresponding to the ground lift peak is defined as the ground contact interval. The ground contact peak corresponds to the moment when a point on the tire begins to contact the ground, and the ground lift peak corresponds to the moment when that point leaves the ground. The time interval between the two peaks is the time that point is in contact with the ground, i.e., the ground contact interval. Within the ground contact interval, the tire is affected by the ground force, and its motion deviates from pure circular motion. The radial acceleration does not satisfy the physical relationship of circular motion, so it cannot be used for speed calculation. The time interval in the tire rolling cycle other than the ground contact interval is defined as the non-ground contact interval. A complete tire rolling cycle includes two parts: the ground contact interval and the non-ground contact interval. The ground contact interval only accounts for a small part of the rolling cycle, and most of the time, the points on the tire are in a non-ground contact state. Within the non-ground contact interval, the tire particles undergo approximately uniform circular motion, and the radial acceleration is mainly composed of centripetal acceleration, satisfying the physical relationship of circular motion, and can be used for speed calculation.

[0023] a=rω²=vω Where a represents radial acceleration, r represents the rotation radius at the sensor mounting position, ω represents the tire rolling angular velocity, and v represents the tire linear velocity at the sensor mounting position. This formula establishes the relationship between radial acceleration, linear velocity, and angular velocity in circular motion. The equivalent form of this relationship, a=vω, does not directly include the tire radius parameter, which is the physical basis for this invention to be independent of tire radius dependence.

[0024] Dividing the sampled value of the radial acceleration signal within the ungrounded zone by the sampled value of the rolling angular velocity signal at the same moment yields the tire linear velocity at the sensor's mounting position at that corresponding moment. The product relationship is a equal to v multiplied by ω, where a represents radial acceleration, v represents tire linear velocity, and ω represents rolling angular velocity. Here, the radial acceleration 'a' is the centripetal acceleration of the tire mass in the ungrounded zone as it undergoes circular motion. Since the motion of the tire mass in the ungrounded zone is approximately uniform circular motion, the radial acceleration is primarily the centripetal acceleration. The rolling angular velocity ω is directly measured by the gyroscope and is the angular velocity of the tire rotating around its own axis. Dividing the sampled value of radial acceleration at the same moment by the sampled value of angular velocity yields the tire linear velocity at the sensor's mounting position at that moment. The radial acceleration and angular velocity used in the calculation must come from the same moment to ensure temporal synchronization; otherwise, calculation deviations will be introduced. Within the ungrounded zone, multiple sampled values ​​can be selected to calculate the velocity separately, and then the average value can be taken as the final velocity result to reduce the influence of random noise. Alternatively, the signal can be filtered before calculation to further improve the stability of the calculation results.

[0025] v=a / ω Where v represents the tire linear velocity at the sensor mounting location, a represents the radial acceleration, and ω represents the rolling angular velocity. This formula is derived from the equivalent form a=vω of a=rω²=vω. By directly measuring the radial acceleration and angular velocity, the linear velocity can be calculated without knowing the tire radius, thus fundamentally avoiding the speed estimation error caused by the uncertainty of the tire's dynamic radius in traditional solutions.

[0026] Based on the distance parameter between the accelerometer and the tire tread, the tire linear velocity at the sensor's mounting location is corrected to obtain the tire linear velocity at the tread. The accelerometer is mounted in the tire's inner liner, and its radial distance from the tire's axis of rotation is less than the radial distance at the tread. In other words, the circumferential radius at the sensor is smaller than the circumferential radius at the tread. Since the angular velocity is the same at all points on the same rigid body, and linear velocity is proportional to the radius of rotation, the linear velocity at the sensor is less than the linear velocity at the tread. If the slip ratio is calculated directly using the linear velocity at the sensor, the result will be too small, resulting in a systematic bias. Therefore, it is necessary to correct the linear velocity at the sensor and convert it to the linear velocity at the tread.

[0027] Obtain the radial distance parameter between the sensor mounting position and the tire tread. This distance parameter refers to the vertical distance from the sensor mounting position to the tire tread surface along the tire's radial direction. This parameter is determined during sensor installation and primarily depends on the tire's structural dimensions and the sensor's mounting depth. Tire structural dimensions include tread thickness, belt layer thickness, and inner liner thickness, which can be obtained from the tire's design specifications. The sensor mounting depth refers to the distance from the sensor's sensitive element location to the tire tread surface after the sensor is attached to the inner liner surface. Multiply the distance parameter by the value of the rolling angular velocity signal to obtain the speed correction. The physical meaning of the speed correction is the difference in linear velocity between the sensor and the tire tread due to the radius difference. Its derivation is as follows: Let the rotation radius at the sensor be r1, the rotation radius at the tire tread be r2, and the radial distance between the sensor and the tire tread be h. Then r2 equals r1 plus h. Since the angular velocity ω is the same, the linear velocity v1 at the sensor is equal to r1 multiplied by ω, and the linear velocity v2 at the tire tread is equal to r2 multiplied by ω. Substituting r2 into the expression for v2, we get v2 equals the sum of r1 and h multiplied by ω. Expanding this, we get v2 equals r1 multiplied by ω plus h multiplied by ω. Since v1 equals r1 multiplied by ω, v2 equals v1 plus h multiplied by ω. Here, h multiplied by ω is the velocity correction factor.

[0028] v′=(h+r)ω=(h+r)v / r=(h+a / ω²)ω Where v′ represents the tire linear velocity at the tread, h represents the radial distance between the sensor mounting position and the tread, r represents the rotation radius at the sensor mounting position, ω represents the rolling angular velocity, and a represents the radial acceleration. This derivation chain contains three layers of meaning: First, the velocity at the tread is equal to the product of the rotation radius (h+r) and the angular velocity ω at the tread; second, it is rewritten using v=rω to the corrected form of the velocity v at the sensor: (h+r)v / r; third, further using r=v / ω=a / ω², it is completely expressed as a function of the measurable quantities a, ω, and the distance parameter h, i.e., v′=(h+a / ω²)ω, and the entire correction process does not depend on the tire radius.

[0029] The tire linear velocity at the sensor mounting location is added to the speed correction amount to obtain the tire linear velocity at the tread. This corrected tread linear velocity is the true linear velocity at the tire-ground contact point, and only then does it have the correct physical meaning for calculating the slip ratio. The distance parameter h is not absolutely constant during tire use; tire wear reduces the tread thickness, causing a slight decrease in the h value. However, normal tire wear is typically only a few millimeters, a very small proportion relative to the overall tire radius, so the change in h is also small and its impact on the speed calculation result is negligible. If higher accuracy is required, the h value can be dynamically corrected using a wear monitoring algorithm to further improve calculation accuracy. Tire wear monitoring can be achieved in various ways, such as estimating wear through tire pressure and load, or updating the h value through periodic calibration.

[0030] The vehicle's speed is acquired via an onboard GPS receiver. This receiver, installed on the vehicle, receives satellite signals via an antenna and outputs the vehicle's position and speed information after processing by an internal processor. The speed information output frequency is typically 1Hz or higher, sufficient for most applications. The second pulse signal output by the onboard GPS receiver serves as a unified time reference for time synchronization of the vehicle's speed, radial acceleration, and roll angular velocity signals. The second pulse signal is a time reference signal output by the GPS receiver, typically outputting one pulse per second. The rising edge of the pulse is aligned with the exact second of International Standard Time (USST), achieving microsecond or even nanosecond accuracy. Since the accelerometer and gyroscope inside the tires are from different hardware systems and each has its own independent clock, a time synchronization issue would result in a time discrepancy between the two sets of data.

[0031] The tire slip ratio is calculated based on the tire linear velocity at the tread and the vehicle speed. Tire slip ratio is a physical quantity that measures the degree of relative slippage between the tire and the ground. It is defined as the difference between the vehicle speed and the tire tread linear velocity divided by the greater of the absolute values ​​of the vehicle speed and the tread linear velocity. The slip ratio typically ranges from -1 to 1, and can also be expressed as a percentage. When the tire is rolling purely, the tread linear velocity equals the vehicle speed, and the slip ratio is zero. When the tire is completely slipping, the tread linear velocity is zero, and the slip ratio is 100%. Under driving conditions, the tire speed is higher than the pure rolling speed, the tread linear velocity is greater than the vehicle speed, and the slip ratio is negative; in this case, the denominator is the absolute value of the tread linear velocity. Under braking conditions, the tire speed is lower than the pure rolling speed, the tread linear velocity is less than the vehicle speed, and the slip ratio is positive; in this case, the denominator is the vehicle speed. Different slip ratios correspond to different tire adhesion characteristics. The coefficient of adhesion shows a peak value as the slip ratio changes, typically reaching its maximum when the slip ratio is between 10% and 20%.

[0032] s=(v1-v′) / max(v1, |v′|) Where s represents the tire slip ratio, v1 represents the vehicle speed, and v′ represents the tire linear velocity at the tread. In the formula, max(v1, |v′|) means taking the larger of the absolute values ​​of the vehicle speed v1 and the tread linear velocity v′ as the denominator, so that the slip ratio has a unified physical meaning and consistent dimensions under both braking and driving conditions. When the tire is rolling purely, the tread linear velocity equals the vehicle speed, i.e., v′=v1, and the slip ratio s=0; when the tire is completely slipping, the tread linear velocity is zero, i.e., v′=0, and the slip ratio s=1 (i.e., 100%). Under driving conditions, the tire speed is higher than the pure rolling speed, the tread linear velocity is greater than the vehicle speed, and the slip ratio is negative; under braking conditions, the tire speed is lower than the pure rolling speed, the tread linear velocity is less than the vehicle speed, and the slip ratio is positive.

[0033] When the vehicle is braking, i.e., the vehicle speed is greater than the tire tread speed (v1>v′), the denominator is v1, and the slip ratio s = (v1-v′) / v1, where s is a positive value. When the vehicle is driving, i.e., the tire tread speed is greater than the vehicle speed (v′>v1), the denominator is |v′| = v′, and the slip ratio s = (v1-v′) / v′, where s is a negative value. When the vehicle is rolling (v′=v1), s = 0. If only the magnitude of the slip between the tire and the ground needs to be characterized without distinguishing between braking and driving directions, the absolute value of the slip ratio |s| can be used, with a range from zero to one.

[0034] The tire slip ratio is compared with a preset slip ratio threshold. The preset slip ratio threshold is a reference value used to determine whether tire slip exceeds a set range. When the actual measured slip ratio exceeds this threshold, the tire is considered to be slipping, and a warning signal needs to be issued. The specific value of the preset slip ratio threshold needs to be determined based on the application scenario and control strategy. Different thresholds can be set for different road conditions, vehicle types, and driving conditions. For low-friction surfaces such as icy or snowy roads, even a small slip ratio may cause the vehicle to lose control, so the threshold can be set lower. For high-friction surfaces such as dry asphalt roads, the tire can withstand a larger slip ratio, so the threshold can be set higher. The threshold setting also needs to consider the impact of measurement errors and noise to avoid false triggering.

[0035] When the tire slip ratio exceeds the preset slip ratio threshold, a slip warning signal is generated. The slip warning signal is an electrical signal characterizing abnormal tire slippage, used to notify other vehicle control systems that tire slippage has occurred. The warning signal can be a digital level signal, a bus communication message, or an analog signal, selected according to the system architecture. The slip warning signal is sent to the vehicle brake control unit, causing the vehicle brake control unit to perform braking intervention and torque adjustment actions. The vehicle brake control unit is the control unit on the vehicle responsible for controlling the braking system, and has the ability to adjust the braking force of each wheel. Braking intervention refers to controlling the tire slip ratio by adjusting the braking force of each wheel to prevent further slippage. Torque adjustment refers to adjusting the engine output torque to reduce driving force, thereby reducing the degree of tire slippage. The combination of braking intervention and torque adjustment allows for control of tire slippage from both braking and driving perspectives, restoring the slip ratio to the set range.

[0036] The signal acquisition module acquires radial acceleration signals from an accelerometer installed in the tire's inner liner and rolling angular velocity signals from a gyroscope. As the input interface of the entire device, the signal acquisition module receives the raw signals from the sensors and performs necessary signal conditioning and analog-to-digital conversion, converting analog signals into digital signals for subsequent processing. Signal conditioning includes amplification and filtering to improve signal quality. The interval determination module is connected to the signal acquisition module. Based on the time-domain waveform characteristics of the radial acceleration signal, the interval determination module determines the non-grounded intervals within the tire's rolling cycle. It receives the radial acceleration signal from the signal acquisition module, identifies ground-to-ground and off-ground peak values ​​using waveform analysis algorithms, and then divides the tire into grounded and non-grounded intervals, outputting interval identification information.

[0037] The speed calculation module is connected to the signal acquisition module and the interval determination module. Within the non-grounded interval, the speed calculation module determines the tire linear velocity at the sensor mounting position using the radial acceleration signal and the rolling angular velocity signal, based on the relationship that radial acceleration in circular motion equals the product of linear velocity and angular velocity. The speed calculation module receives the radial acceleration signal and rolling angular velocity signal from the signal acquisition module and the identification information of the non-grounded interval from the interval determination module. It performs speed calculations within the non-grounded interval and outputs the tire linear velocity at the sensor mounting position. The speed calculation module internally includes a division unit for performing the calculation of radial acceleration divided by angular velocity.

[0038] The speed correction module is connected to the speed calculation module. The speed correction module corrects the tire linear velocity at the sensor mounting position based on the distance parameter between the accelerometer and the tire tread, obtaining the tire linear velocity at the tread. The speed correction module receives the sensor velocity output from the speed calculation module, combines it with preset distance parameters and angular velocity signals, performs correction calculations, and outputs the tire linear velocity at the tread. The speed correction module internally includes a multiplication unit and an addition unit, used to calculate the speed correction amount and perform the correction addition, respectively.

[0039] The vehicle speed acquisition module is used to acquire the vehicle's speed. It is another input channel responsible for receiving the vehicle speed signal from the vehicle speed detection device and performing necessary format conversion and time stamping. The slip ratio calculation module is connected to both the speed correction module and the vehicle speed acquisition module. This module calculates the tire slip ratio based on the tire linear velocity at the tread and the vehicle's speed. The slip ratio calculation module receives the tire linear velocity at the tread and the vehicle's speed, performs the slip ratio calculation, and outputs the final tire slip ratio result. Internally, the slip ratio calculation module includes a subtraction unit and a division unit, used to calculate the speed difference and perform division operations, respectively.

[0040] The sensing unit includes an accelerometer and a gyroscope, both mounted in the tire's inner liner. The accelerometer collects radial acceleration signals during tire rolling, while the gyroscope collects rolling angular velocity signals. The sensing unit is the perception layer of the entire system, responsible for acquiring raw data on the tire's motion. It comprises two sensing elements, an accelerometer and a gyroscope, both mounted in the tire's inner liner and rolling with the tire, directly measuring the tire's own motion parameters. The accelerometer collects radial acceleration signals, and the gyroscope collects rolling angular velocity signals; these two signals together constitute a description of the tire's motion state.

[0041] The vehicle speed detection unit is used to detect the vehicle's speed. It is responsible for detecting the overall vehicle speed and is another data source for the system. The vehicle speed detection unit can use a GPS receiver or other speed measurement methods. The processing unit is communicatively connected to the sensing unit and the vehicle speed detection unit, and it executes the aforementioned method steps. The processing unit is the core of the entire system, undertaking data processing and calculation functions. It transmits data with the sensing unit and the vehicle speed detection unit via a communication connection, receiving radial acceleration and roll angular velocity signals from the sensing units, and vehicle speed signals from the vehicle speed detection unit. The processing unit executes data processing algorithms, including non-grounding zone identification, tire speed calculation, speed correction, and slip ratio calculation, ultimately obtaining the tire slip ratio result.

[0042] The warning output unit is communicatively connected to the processing unit. The warning output unit generates a slip warning signal based on the tire slip ratio output by the processing unit. The warning output unit receives the slip ratio result from the processing unit, and when the slip ratio exceeds a preset threshold, it generates and outputs a slip warning signal. The warning signal can be provided to other vehicle control systems to trigger corresponding control actions. The communication connection serves as the channel for data exchange between units and can be implemented via wired or wireless means. Wireless communication is typically used between the sensing unit inside the tire and the processing unit on the vehicle side, as the tire is a rotating component and cannot be connected via wired means. Wireless communication can employ radio frequency communication, Bluetooth communication, or other dedicated wireless communication protocols.

[0043] In passenger vehicle applications, integrated multi-axis sensor chips are installed in the inner lining of each of the four tires. Each chip includes a three-axis accelerometer and a three-axis gyroscope, with a sampling frequency set to 500Hz. The sensor chips transmit data to a receiving unit on the vehicle side via low-power radio frequency communication. The receiving unit then transmits the data to a processing unit. The processing unit uses the vehicle's electronic control unit (ECU) to run a slip ratio calculation algorithm. The vehicle speed is obtained through the onboard GPS and synchronized using a second pulse signal. When the calculated slip ratio exceeds a preset threshold, a warning signal is sent to the brake control unit via the onboard bus, triggering anti-lock braking system (ABS) or traction control. In this application scenario, the system can continuously monitor the slip status of each tire during vehicle operation, providing data support for the vehicle stability control system.

[0044] In commercial vehicle applications, the larger tire size and wider load variation range of commercial vehicles place higher demands on the sensor's measurement range and installation reliability. Accelerometers and gyroscopes with larger measurement ranges can be selected to accommodate the greater centrifugal acceleration of commercial vehicle tires. The sampling frequency can be set to 300Hz, reducing data transmission volume and power consumption while ensuring measurement accuracy. A specialized vulcanization process is used during sensor installation to bond the sensor to the tire rubber, ensuring it will not detach under heavy load conditions. Vehicle speed can be obtained through a fusion of GPS and vehicle speed sensors, improving overall speed measurement performance. Warning signals are sent to the commercial vehicle's electronic braking system, enabling independent control of each wheel.

[0045] In test vehicle applications, higher requirements are placed on measurement accuracy and time resolution. Therefore, sensors with higher performance specifications can be selected, and the sampling frequency is set to 1000Hz to capture rich signal details. The sensor's installation position is precisely calibrated, and the alignment error in the sensitive axis direction is controlled within a very small range. Data transmission uses high-speed wireless communication to ensure that a large amount of data can be transmitted to the onboard data acquisition system. Vehicle speed is acquired through a high-precision inertial navigation system, with time synchronization accuracy reaching the microsecond level. The calculated slip ratio data can be compared and analyzed with data from other testing equipment for tire performance and vehicle dynamics studies.

[0046] There are several alternative methods for identifying ungrounded regions. Besides detecting grounding peak values ​​and above-ground peak values, the variance of radial acceleration can also be used. Ungrounded regions exhibit smaller radial acceleration fluctuations and smaller variances, while grounded regions show larger fluctuations and larger variances. Changes in angular velocity signals can also aid in the identification; grounding causes slight fluctuations in angular velocity. Alternatively, an amplitude window can be set, defining ungrounded regions as those with radial acceleration amplitudes within a certain range. These methods can be used individually or in combination to improve the accuracy and reliability of the identification.

[0047] There are several alternative methods for obtaining vehicle speed. Besides the Global Positioning System (GPS), inertial navigation systems can also be used. Inertial navigation systems obtain speed through acceleration integration, offering high short-term accuracy, but errors accumulate over time. Vehicle speed can also be estimated using wheel speed sensors in conjunction with tire radius; this is a traditional method, but it is significantly affected by changes in radius. Doppler radar can also directly measure the vehicle's speed relative to the ground; this method offers high accuracy but is also more expensive. Combining these different speed measurement methods can leverage their strengths and compensate for their weaknesses, improving the overall performance of speed measurement.

[0048] There are several alternatives to sensor mounting. Besides adhesive mounting, embedded mounting is another option, where the sensor is embedded inside the tire rubber, forming a single integrated unit. The advantages of embedded mounting are a tighter bond between the sensor and the tire, reducing the likelihood of detachment and providing more direct signal transmission. However, embedded mounting requires more sophisticated tire manufacturing processes and is more expensive. Magnetic mounting is also an option, using magnets to secure the sensor to a metal component inside the tire, facilitating removal and replacement. Different mounting methods are suitable for different application needs, and the choice can be made based on the specific requirements.

[0049] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for calculating tire slip ratio based on inertial sensing signals, characterized in that, Executed by the processor, including: S1: Acquire the radial acceleration signal from the tire liner accelerometer and the rolling angular velocity signal from the gyroscope; S2: Based on the time-domain waveform characteristics of the radial acceleration signal, determine the non-grounded interval in the tire rolling cycle; S3: Within the non-grounded zone, the tire linear velocity at the sensor mounting position is determined by the radial acceleration and rolling angular velocity, based on the product relationship between radial acceleration, linear velocity, and angular velocity. S4: Based on the distance parameter between the accelerometer and the tire tread, the tire linear velocity at the sensor is corrected to obtain the tire linear velocity at the tread. S5: Obtain vehicle speed; S6: Calculate the slip ratio based on the tire linear velocity at the tread and the vehicle speed.

2. The method according to claim 1, characterized in that, The step of determining the ungrounded interval includes: performing time-domain waveform analysis on the radial acceleration signal to detect the grounding peak value and the off-ground peak value; The interval between the ground peak value and the off-ground peak value is defined as the ground interval; the interval in the tire rolling cycle that is outside the ground interval and the time-domain waveform of the radial acceleration signal satisfies a preset stability condition is defined as the non-ground interval; wherein, the preset stability condition is that the fluctuation of the radial acceleration signal within a set time window is less than or equal to a preset fluctuation threshold.

3. The method according to claim 1, characterized in that, The step of determining the tire linear velocity at the sensor installation location includes: dividing the sampled value of the radial acceleration signal within the non-grounded interval by the sampled value of the rolling angular velocity signal at the same moment to obtain the tire linear velocity at the corresponding moment; the product relationship is... , where a is the radial acceleration, v is the tire linear velocity, and ω is the rolling angular velocity.

4. The method according to claim 1, characterized in that, The step of obtaining the tire linear velocity at the tread includes: acquiring the radial distance parameter between the sensor mounting position and the tread; multiplying the distance parameter by the value of the rolling angular velocity signal to obtain a speed correction amount; and adding the tire linear velocity at the sensor mounting position to the speed correction amount to obtain the tire linear velocity at the tread.

5. The method according to claim 1, characterized in that, The accelerometer and gyroscope are integrated into the same multi-axis sensing chip, which is attached to the middle position of the tire inner liner along the width direction. The radial sensing axis of the accelerometer is arranged along the radial direction of the tire, and the rolling sensing axis of the gyroscope is arranged along the rolling axis of the tire.

6. The method according to claim 1, characterized in that, The sampling frequency of the radial acceleration signal and the rolling angular velocity signal is 100-5000 Hz.

7. The method according to claim 1, characterized in that, The steps for obtaining the vehicle speed include: The vehicle's speed is obtained through an onboard GPS receiver. Using its second pulse signal as a unified time reference, the vehicle's driving speed, radial acceleration signal, and rolling angular velocity signal are synchronized in time.

8. The method according to claim 1, characterized in that, Also includes: The tire slip ratio is compared with a preset threshold; a slip warning signal is generated when the preset threshold is exceeded. The slip warning signal is sent to the vehicle braking control unit to perform braking intervention and power torque adjustment.

9. A device for calculating tire slip ratio based on inertia sensing signals, applied to the method described in any one of claims 1-8, characterized in that, include: The signal acquisition module is used to acquire the radial acceleration signal from the tire inner liner accelerometer and the rolling angular velocity signal from the gyroscope. The system includes: an interval determination module for determining the non-grounded interval in the tire rolling cycle based on the time-domain waveform characteristics of the radial acceleration signal; a speed calculation module for determining the tire linear velocity at the sensor mounting position within the non-grounded interval based on the product relationship between radial acceleration, linear velocity, and angular velocity; a speed correction module for correcting the tire linear velocity at the tread based on the distance parameter between the acceleration sensor and the tire tread; and a vehicle speed acquisition module for acquiring the vehicle's driving speed. The slip ratio calculation module is used to calculate the tire slip ratio based on the tire linear velocity at the tread and the vehicle speed.

10. A system for calculating tire slip ratio based on inertial sensing signals, characterized in that, include: The sensing unit includes an accelerometer and a gyroscope, both mounted on the inner liner of the tire, which respectively collect radial acceleration and rolling angular velocity signals; a vehicle speed detection unit for detecting the vehicle speed; and a processing unit, which is communicatively connected to the sensing unit and the vehicle speed detection unit, for executing the method described in any one of claims 1 to 8. The warning output unit is communicatively connected to the processing unit and is used to generate a slip warning signal based on the tire slip ratio output by the processing unit.

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