Method for determining the remaining service life of a brake component

Abstract

A method for determining a remaining service life of a brake component, the method comprising: providing vehicle parameters that identify the operating conditions of a motor vehicle; using the vehicle parameters to determine work performed by a brake of the motor vehicle as braking work; using the braking work to determine the brake rotor temperature; using the brake rotor temperature to determine fatigue damage of the brake component; accumulating the fatigue damage to determine cumulative fatigue damage of the brake component, and comparing the cumulative fatigue damage to a damage limit to provide an estimate of the remaining service life of the brake component;wherein the brake component is a vehicle brake rotor and the fatigue damage is a thermal and mechanical energy-based damage calculation, and wherein the method further comprises: using the brake rotor temperature to determine energy-based brake rotor wear; accumulating the brake rotor wear to provide an estimate of the thickness of the vehicle brake rotor; calculating oxidative brake rotor wear based on an exposure time of the vehicle brake rotor; calculating the brake rotor wear by summing the oxidative brake rotor wear and the energy-based brake rotor wear, and using the brake rotor wear to determine the cumulative fatigue damage of the vehicle brake rotor; wherein the oxidative brake rotor wear is calculated by scaling the exposure time of the vehicle brake rotor by a predetermined oxidative wear parameter.

Description

Technical area

[0001] The present invention relates generally to the field of motor vehicles and, more particularly, to a system and method for estimating the remaining life of a brake component that is wearing through use. introduction

[0002] The brake rotor is an integral component of braking systems on various types of motor vehicles. The disc brake is an energy conversion device that converts mechanical energy into heat. Disc brake systems consist of a non-rotating friction material and application subsystems, as well as a brake rotor that rotates with the wheel. To stop or decelerate the motor vehicle, the friction material subsystem is brought into contact with the braking surfaces (rotor shoes) of the brake rotor to generate heat through friction, thereby converting mechanical energy into heat and slowing the wheel's rotation.

[0003] The performance of the braking system in general, and of the brake rotor in particular, is largely determined by the surface condition of the rotor shoes. Normal operation of a braking system involves the generation of high levels of friction, which in turn generates high temperatures on the rotor shoe surfaces. Environmental impacts from contact with corrosive substances such as road salt and water exacerbate rotor corrosion. These effects, either individually or in combination, can lead to pedal pulsation or a corroded braking surface.

[0004] The braking system is an aggressive environment for corrosion and high-temperature oxidation of the brake rotors, which are typically made of cast iron. The resulting oxides can spall off during normal braking applications. Spalling oxides create locally raised areas, forming deep notches or grooves on the rotor shoe surfaces. These surface features can generate pedal pulsation during braking.

[0005] Furthermore, some motor vehicles use open wheel designs that leave the rotor braking surfaces visible to the observer. Surface corrosion, which would normally be insignificant in terms of the operation of the braking system, becomes a problem due to the visible oxidation.

[0006] Corrosion causes the thickness of the rotor to decrease over time, and below certain thickness levels, rotor operation may be suboptimal, e.g., the motor vehicle may not stop as quickly.

[0007] FR 2 959 717 A1 describes a device for continuously monitoring the condition of brake disc damage in a vehicle's braking system. The device has a converter unit that provides a macroscopic measurement value for quantifying the intensity of a braking event. A logical control unit is designed to acquire and process the macroscopic measurement value. The control unit accesses a readable memory containing an empirical relationship between the macroscopic measurement value and a brake disc damage rate. An alarm module can query a read-write memory to trigger an alarm when the accumulation of the damage rate reaches a certain threshold. A method for creating a brake disc damage indicator for a monitoring device is also described.

[0008] DE 10 2008 015 288 A1 describes a method for providing an estimate of brake pad thickness. The method uses a fusion of sensors, if used, and driver braking modeling to predict vehicle brake pad life. An algorithm is employed that uses various inputs, such as brake pad friction material properties, brake pad cooling rate, brake temperature, vehicle mass, road gradient, weight distribution, brake pressure, brake energy, brake power, etc., to provide the estimate. The method calculates braking work using total work minus losses, such as air resistance, engine braking, and / or brake power as brake torque times speed divided by rolling resistance, to determine the brake disc and pad temperature.The method then uses the brake temperature to determine the brake pad wear, accumulating the wear for each braking event. A brake pad sensor may be included to provide one or more indications of the brake pad thickness, allowing the estimate to be revised.

[0009] EP 2 899 081 A2 describes a system and method for estimating the condition of the friction material of an aircraft braking system. The method includes sensing a temperature of the friction material and supplying the sensed temperature to a processor-implemented thermal model configured to estimate the friction material temperatures at one or more locations on the friction material. The estimated friction material temperatures are supplied to a processor-implemented thermal oxidation model configured to estimate the friction material loss due to thermal oxidation based on the estimated friction material temperatures.Data representative of the runway fluid loading is fed to a processor-implemented catalytic oxidation model configured to estimate friction material loss due to catalytic oxidation based on the runway fluid loading. Friction material condition is estimated based on the friction material loss estimates from the processor-implemented thermal oxidation model and the processor-implemented catalytic oxidation model.

[0010] EP 2 988 120 A1 describes that the exposure of an aircraft component to an oxidation catalyst, such as a de-icing solution, can be detected using an electrical conductivity sensor. A system is described that includes an aircraft component, an electrical conductivity sensor mechanically connected to the aircraft component and configured to generate an output signal, and a processor configured to detect an oxidation catalyst exposure event based on the output signal generated by the electrical conductivity sensor. The electrical conductivity sensor may be configured and positioned to generate a signal indicative of the electrical conductivity of a substance to which the aircraft component is exposed.The processor may be configured to detect an oxidation catalyst exposure event by at least determining whether the electrical conductivity indicated by the signal is greater than or equal to a predetermined conductivity threshold.

[0011] WO 2017 / 062590 A1 describes a method for diagnosing and predicting various operational systems so that maintenance can be planned and performed efficiently and effectively. The method is applicable to a wide range of systems, but in particular to aircraft brake systems and tires. An aircraft brake can be modeled by assigning brake wear factor values to various parameters associated with the aircraft brake that affect wear. Over time and during braking events, the brake wear factor values are summed, and the sum is retained over the lifetime of the brake. At a time when the sum of the weighted factors exceeds a predetermined threshold, an indication is generated that maintenance is required.

[0012] DE 10 2017 206 593 A1 describes a method for monitoring the condition of a mechanical brake of an aircraft. The method comprises the following steps: a. Measuring the temperature T of the brake at at least one time t during a landing procedure after the start of a mechanical braking procedure; b. Comparing the measured temperature T with a standard temperature determined for the brake at at least one time t during a landing procedure after the start of a mechanical braking procedure; c. Detecting a wear condition of the brake based on the measured temperature T exceeding the standard temperature by a predetermined amount. A system for implementing the method is also described.

[0013] US 2019 017 561 A1 describes technical solutions for determining the thickness of a vehicle brake disc. An example method includes providing vehicle parameters that identify operating conditions of a vehicle and using the vehicle parameters to determine the work performed by a brake of the vehicle as braking work. Furthermore, the method includes using braking work to determine the brake rotor temperature and using the brake rotor temperature to determine brake rotor wear. The method further includes accumulating brake disc wear to obtain an estimate of the thickness of the vehicle brake disc.

[0014] US 2008 236 269 A1 describes methods for estimating brake pad thickness. The method utilizes sensor fusion, if used, and driver brake modeling to predict vehicle brake pad life. An algorithm is employed that uses various inputs, such as brake pad friction material properties, pad cooling rate, brake temperature, vehicle mass, road gradient, weight distribution, brake pressure, brake energy, brake power, etc., to produce the estimate. The method calculates braking work based on total work minus losses such as aerodynamic drag, engine braking, and / or brake power as braking torque times speed divided by rolling resistance to determine the brake rotor and pad temperature.The method then uses the brake temperature to determine brake pad wear, accumulating wear for each braking event. A brake pad sensor can be included to provide one or more brake pad thickness readings that can be used to correct the estimate.

[0015] Therefore, the object of the invention is to determine and indicate the condition of the brake rotor so that the brake system can be maintained and the rotors can be replaced in a timely manner. Description of the invention

[0016] The object of the invention is achieved by the subject matter of claims 1 and 8. Advantageous further developments emerge from the subclaims and the following description.

[0017] The invention is defined by the claims.

[0018] Embodiments according to the present disclosure provide a number of advantages. For example, embodiments according to the present disclosure enable real-time determination of brake rotor fatigue for each braking event and accumulation of brake rotor fatigue to determine brake rotor life.

[0019] In one aspect of the invention, the method for determining a remaining service life of a brake component includes the steps of providing vehicle parameters that identify the operating conditions of a motor vehicle and using the parameters to determine the work performed as braking work by a brake of the motor vehicle, using the braking work to determine the brake rotor temperature, using the brake rotor temperature to determine fatigue damage of the brake component, accumulating the fatigue damage to determine cumulative fatigue damage of the brake component, and comparing the cumulative fatigue damage to a damage threshold to provide an estimate of the remaining service life of the brake component. The brake component is a vehicle brake rotor, and the fatigue damage is a thermal and mechanical energy-based damage calculation.The method according to the invention further comprises using the brake rotor temperature to determine energy-based brake rotor wear, accumulating the brake rotor wear to provide an estimate of the thickness of the vehicle brake rotor, calculating oxidative brake rotor wear based on the exposure time of the vehicle brake rotor, calculating the brake rotor wear by summing the oxidative brake rotor wear and the energy-based brake rotor wear, and using the brake rotor wear to determine the cumulative fatigue damage of the vehicle brake rotor. The oxidative brake rotor wear is calculated by scaling the exposure time of the vehicle brake rotor with a predetermined oxidative wear parameter.

[0020] According to one embodiment, the predetermined oxidative wear parameter is specific to a material of the vehicle brake rotor.

[0021] According to another embodiment, providing vehicle parameters includes providing brake rotor friction material, brake rotor cooling rate, vehicle mass, road gradient, dynamic braking distribution, vehicle weight distribution, vehicle speed, wheel speed, and brake pressure.

[0022] According to a further embodiment, determining the braking work includes subtracting the resistance values from the total work performed by the brake of the motor vehicle, wherein the resistance values are forces that reduce the total work.

[0023] According to a further embodiment, determining the braking work includes determining the braking force as brake pressure times brake rotor area times brake rotor friction coefficient.

[0024] According to a further embodiment, determining the braking work includes determining a braking force as torque generated by the vehicle times the speed of the motor vehicle divided by the rolling radius of a vehicle wheel.

[0025] According to another embodiment, the method further includes notifying of the estimation of the remaining life of the brake component using telematics.

[0026] According to a further aspect of the invention, a vehicle braking system for determining a remaining service life of a braking component includes the braking component and a processor, wherein the processor is configured to carry out the above-described method according to one of the described embodiments. Brief description of the drawings

[0027] The present disclosure is described in conjunction with the following figures, wherein like numerals refer to like elements. Fig. 1 shows exemplary components of a disc brake system of a motor vehicle according to an embodiment. Fig. 2 is a block diagram of a system for estimating the life of brake components according to one or more embodiments. Fig. 3 is an example block diagram of a model and data fusion processor according to one or more embodiments. Fig. 4 is a flowchart of an exemplary method for estimating a lifetime of a brake component according to one or more embodiments. Fig. 5 is a flowchart of an exemplary method for notifying the vehicle operator of the estimated life of the brake components according to one or more embodiments. Detailed description

[0028] Vehicle brake components such as brake rotors and brake calipers are subject to intense stress and, depending on the application, are subject to fatigue damage. For example, rotors used in race cars can develop fatigue cracks after grueling use on the racetrack.

[0029] Autonomous motor vehicles are heavily used in cyclical operation and may be subject to regular, mandatory inspections. For this purpose, the rotors / drums of heavy-duty and commercial vehicles can fracture due to high loads and intensive operating cycles. The methods described above combine thermal models of rotor wear, fatigue damage models, and customer load data to create a predictive model that can be executed in the vehicle control unit and, in some embodiments, used to notify the vehicle operator of the remaining service life of a braking component of the motor vehicle, such as the remaining service life of a brake rotor.

[0030] Fig. 1 shows exemplary components of a disc brake system 51 of a motor vehicle according to one or more embodiments. It should be noted that in other examples, the disc brake system 51 may include additional, fewer, and / or different components than those shown here. The disc brake system 51 includes a rotor 53 and brake pads 55. In one or more examples, the rotor 53 is also referred to as a disc. The brake system 51 further includes a brake caliper assembly 57. In one or more examples, the rotor 53 has brake pad contact surfaces (shoes) 66, 67. The brake caliper 57 is typically attached to the motor vehicle and fits around a portion of the rotor 53.When a motor vehicle driver depresses a brake pedal of the motor vehicle, hydraulic fluid in a brake hose connected to the brake caliper 57 is pressurized, pressing the friction material of the brake pads 55 against both surfaces 66, 67 of the rotor 53, which rotates with a wheel of the vehicle. The friction between the brake pads 55 and the rotating rotor 53 serves to slow and possibly stop the vehicle wheel.

[0031] It should be noted that solid rotors can be used, however, medium to large rotors used on heavier or more powerful vehicles can be ventilated rotors. Ventilated rotors have radial cooling channels between the brake pad contact surfaces of the rotor 66, 67, which act as air pumps as the rotor rotates, circulating air from the center of the rotor to the outside of the rotor. The location of the rotor cooling holes can vary depending on the rotor type.

[0032] The technical solutions described herein enable the use of sensor information, driver braking information, and driver braking models to predict or estimate brake rotor thickness, which is one of the inputs used to generate a rotor fatigue damage calculation and a real-time cumulative fatigue damage calculation, and to provide an indication of remaining brake rotor life, remaining mileage, or brake rotor thickness percentage.As detailed below, the rotor fatigue damage algorithm and cumulative fatigue damage algorithm use various parameters and sensor signals to build the models, including brake rotor material properties, brake rotor cooling rate, brake temperature, vehicle mass, road gradient, dynamic braking distribution, vehicle weight distribution, applied braking pressure, braking energy, braking torque, fatigue damage, cooling coefficients, cumulative rotor damage threshold, etc.

[0033] The fatigue and cumulative fatigue damage calculations addressed herein, in some embodiments, include a rotor wear model disclosed in U.S. Patent Application No. 15 / 651,475 (US 2019 017 561 A1), filed July 17, 2017, entitled "BRAKE ROTOR PROGNOSIS," which is hereby incorporated by reference in its entirety. Additionally, the fatigue and cumulative fatigue damage calculations addressed herein include a rotor temperature model disclosed in U.S. Patent Application No. 7,694,555 (US 2008 236 269 A1), entitled "BRAKE PAD PROGNOSIS SYSTEM," which is hereby incorporated by reference in its entirety.

[0034] Fig. Figure 2 is a block diagram of a brake component life estimation system 10 according to one or more embodiments. The system 10 includes a brake control unit 12 and a powertrain control unit 14. The system 10 further includes a model and data fusion processor 16, a brake rotor wear estimation processor 18, and a brake component life estimation processor 20.

[0035] The brake control unit 12 includes a brake rotor temperature estimation processor 26, wheel speed sensors 28, a brake pressure processor 30, and a brake power calculation processor 32. In addition, the brake control unit 12 includes a processor 34 that provides brake system dynamics, a processor 36 that provides brake cooling rate, and a processor 38 that provides signals from an anti-lock brake system (ABS), a traction control system (TCS), an electronic control system (ECS), and an active cornering control (ACC). All or most of the calculations performed in the processors 26-38 are currently available on motor vehicles and / or are well known to those skilled in the art.

[0036] The powertrain control unit 14 includes a vehicle mass estimation processor 40, a road grade estimation processor 42, and a road roughness estimation processor 44. Additional signals may be available for estimating brake rotor thickness, such as a vehicle odometer 46, global positioning system (GPS) signals 48, map information 50, vehicle telematics 52, and an ambient temperature sensor 54. All signals provided by these processors and devices are also typically available in a motor vehicle and would be readily available to one of ordinary skill in the art.

[0037] The brake rotor temperature estimation processor 26 estimates the temperature of the brake rotor 53. Depending on the brake rotor material, brake rotor wear depends on the temperature of the brake rotor 53. The cooling rate of the brake rotor helps determine the brake rotor temperature and depends on the design of the motor vehicle, vehicle speed, wheel speed, ambient temperature, altitude, etc. During operation of the motor vehicle, the air flowing around the brake rotor 53 determines how quickly the rotor 53 cools from the previous braking event. In one or more examples, the temperature of the brake rotor is measured using sensors. However, such sensors are expensive, and thus, in one or more examples, an algorithm is used to estimate the brake rotor temperature.

[0038] The brake performance processor 30 estimates the braking energy dissipation in the braking system 51. This calculation uses various inputs such as stopping distance, stopping time, brake rotor temperature, etc. The brake pressure processor 30 can use the master cylinder pressure of the braking system 51, the weight distribution in the vehicle, and the dynamic braking distribution for the proportional brake pressure at each wheel to determine the braking pressure. The dynamic braking distribution is based on how the weight is distributed in the vehicle and is a known calculation.

[0039] The vehicle mass estimation processor 40 estimates the vehicle mass, typically based on engine torque, a process well known to those skilled in the art. The mass of the motor vehicle may vary due to the number of passengers, cargo in the trunk, fuel capacity, etc. Furthermore, it is well known in the art to determine the road gradient in the estimation processor 42 in combination with the vehicle mass estimate.

[0040] Processor 16 can calculate braking energy using equation (1) below. Braking energy is the work performed by the brakes to decelerate the motor vehicle and is the total work minus rolling resistance, air resistance, engine braking, and road grade. Braking work can be used to calculate the power dissipated by the brakes, where power equals work / time. Power can be calculated at predetermined time intervals during the braking event, for example, every 10 ms. Braking energy=12M(VI2−VF2)−ERR−EG−EE

[0041] In equation (1), M is the mass of the motor vehicle, E RR (RR = Rolling Resistance) is the energy required to roll the motor vehicle on a flat road surface, which is a known value and can be represented as a function of the vehicle speed, for example E RR= aV 2 + bV + C, where “V” is the vehicle speed and “a”, “b”, “c” are predetermined coefficients. Furthermore, in equation (1), E G (G = Degrees (inclination)) the energy required to roll the vehicle due to the inclination of the road, which is also a known value, E E (E = Engine) is the braking by the engine itself, and is also a known value, V I is the speed of the vehicle at the start of braking and V F is the vehicle speed at the end of the braking process. In an alternative embodiment, the vehicle deceleration can be used instead of the vehicle speed V and provided by a longitudinal acceleration sensor.

[0042] The braking power consumed by the braking event can also be estimated as Power = Force X Speed. The braking force can be calculated by processor 16 as follows: Braking force=pressure.area.μ

[0043] In equation (2), µ is the friction coefficient of the brake rotor 53, which depends on the rotor temperature, and area is the surface area of the brake rotor 53.

[0044] Alternatively, the braking power can be calculated by the processor 16 as follows: Braking force = torque rolling radius ⋅ speed

[0045] In equation (3), the torque is calculated for both the front and rear of the vehicle and depends on the brake pressure and the dynamic brake distribution. The rolling radius is the rolling radius of the wheel, and the speed is the vehicle speed.

[0046] In one or more examples, the integration of the applied braking force is input into a physical thermal model for first-order dynamics to determine an estimate of the brake temperature. Brake rotor dynamometer tests can be used to obtain the brake pad friction coefficient as a function of temperature. The tests are used to determine the expected wear at different rotor temperatures, and the thermal model is configured accordingly.

[0047] Furthermore, the force required to stop the motor vehicle can be estimated by the processor 16 as follows: Force=Mass.Acceleration

[0048] The front / rear braking distribution information and the cornering information available from the braking control unit 12 are used to determine the power distribution to each axle and corner. The vehicle mass estimate is available from the powertrain control unit 14 and is also used in these equations. From the braking energy and braking power, respectively, the brake rotor temperature can be determined as a proportional value, and from the brake rotor temperature, the brake rotor wear can be determined as a proportional value. For example, one or more lookup tables in the estimation processor 18 enable the determination of the proportional values. The one or more lookup tables are maintained based on the relationship between the braking energy and the brake rotor temperature and the brake rotor temperature and the brake rotor wear based on the calculations discussed above and the characteristics of the brake rotor.Each time the system 10 calculates brake rotor wear, this is added to previous wear calculations and can then be extrapolated from the vehicle mileage to determine the remaining mileage for each brake rotor. Alternatively or additionally, in one or more examples, the estimation processor 18 determines rotor wear dynamically, rather than using lookup tables, using a predetermined calculation formula based on the relationship between braking energy and brake rotor temperature, and brake rotor temperature and brake rotor wear.

[0049] The processor 16 uses a combination of the information available above to estimate the oxidation of the rotor 53. For example, the processor 16 uses an oxidative wear model for the material of the rotor 53 to determine how much the rotor 53 has worn based on the combination of the information available above. For example, the oxidative wear model uses an exposure time of the rotor 53 and an oxidative wear parameter that is a predetermined configurable value.

[0050] In one or more examples, the oxidative wear parameter is based on a type of rotor 53, such as material, shape, dimensions, and other parameters of the rotor 53. The oxidative wear parameter represents a penetration rate of oxides into the rotor material. In one or more examples, the exposure time of the rotor 53 is monitored from the moment the motor vehicle is manufactured and / or from the moment the rotor 53 is operated. For example, the processor measures a time associated with each braking event, such as the amount of time the vehicle operator depresses the brake pedal to cause the motor vehicle to decelerate. The measured time is accumulated to provide the exposure time of the rotor 53. Alternatively or additionally, the exposure time since the rotor 53 was installed on the motor vehicle is measured.The exposure time is reset when the rotor 53 is replaced. In one or more examples, a vehicle subsystem, such as a vehicle computer, documents the time since the rotor was installed on the vehicle and provides the value when requested.

[0051] Scaling the exposure time with the oxidative wear parameter provides an amount (e.g., in millimeters or micrometers) of corrosion of the rotor 53. Alternatively, in one or more examples, the processor 16 uses a lookup table to determine the amount of corrosion of the rotor based on the exposure time, where the lookup table includes corrosion values based on the oxidative wear parameter. The oxidative wear parameter is the corrosion rate for the rotor. In one or more examples, the oxidative wear parameter is adjusted depending on a position of the motor vehicle, available, for example, from a global positioning system (GPS) of the motor vehicle 10. For example, the processor 16 uses a lookup table to determine the oxidative wear parameter to use based on the location coordinates received by the GPS.The location coordinates may be used to identify a geographic area such as a city, state, or the like, and then an oxidative wear parameter corresponding to the geographic region is used to determine the corrosion of the rotor 53.

[0052] The wear estimate generated by wear estimation processor 18 is, in some embodiments, used by processor 16 to determine fatigue damage of the brake component. In some embodiments, the brake component is a brake rotor. As discussed in more detail herein, brake component fatigue damage is a real-time calculation of fatigue damage of a brake component based on a combination of the information discussed above. Processor 16 further determines cumulative fatigue damage of the brake components. Brake component life estimation processor 20 compares the cumulative fatigue damage of the brake component to a damage threshold to estimate a remaining life of the brake component, as discussed in more detail herein.

[0053] Fig. 3 illustrates an example block diagram of the model and data fusion processor 16, according to one or more embodiments. The rotor wear estimation processor 18 uses a combination of the information available above to estimate the thickness of the brake rotor 53. The processor 16 uses a rotor temperature model 310 to determine a temperature of the rotor 53. The processor 16 further uses a rotor energy to determine braking energy absorbed by the rotor 53. Based on the rotor temperature and the absorbed rotor braking energy, the processor 16 determines corrosion or wear of the rotor 53 according to an energy-based wear model 320. The processor 16 uses a wear volume per unit of absorbed energy by the rotor to determine how much the rotor 53 is wearing based on the model 320.For example, processor 16 determines energy-based wear of rotor 53 according to a wear volume per unit of energy absorbed at the determined temperature. For example, using the equations described herein, processor 16 calculates the units of energy absorbed by rotor 53 during a braking event at the determined temperature. Further, a wear volume of rotor 53 is calculated by multiplying the calculated energy-based wear by a surface area of rotor 53.

[0054] Further, the processor 16 uses an oxidative rotor wear model 330 to calculate oxidative wear of the rotor 53. For example, the processor 16 calculates the oxidative wear of the rotor 53 based on the oxidative wear parameter and the exposure time of the rotor 53.

[0055] Processor 16 calculates energy-based wear and oxidative wear periodically at a predetermined frequency, such as every 10 ms, 20 ms, or another predetermined frequency. Alternatively or additionally, processor 16 calculates wear each time a braking event occurs.

[0056] The processor 16 forwards the calculated wear to the rotor thickness estimation processor 18. The rotor thickness estimation processor 18 collects the wear of the rotor 53 during operation of the motor vehicle over time. The rotor thickness estimation processor 18 uses the collected wear to determine an estimated thickness of the rotor 53. The rotor thickness estimation processor 18 further uses the thickness of the rotor 53 to estimate the service life of the rotor 53, for example, in terms of time, mileage, or some other parameter, for example, using a corrosion model specific to the rotor 53.

[0057] Processor 16 also uses a rotor fatigue model 340 to calculate rotor damage based on braking torque, speed / power, and rotor temperature. For example, processor 16 uses rotor temperature, braking torque, and speed in a thermal and mechanical surface loading-based model to determine real-time rotor fatigue damage. Rotor fatigue damage for a single braking event is modeled, in some embodiments, as a proportional ratio of the product of heat flow into the braking surface and the square root of the braking time to the strength of the rotor material at the maximum temperature reached during the braking event. Proportionality depends on the relevant thermomechanical properties of the rotor material, such as elastic modulus, density, thermal conductivity, and Poisson's ratio.

[0058] The real-time fatigue damage calculated by processor 16 using rotor fatigue model 340 is used by a cumulative fatigue damage model 350 to accumulate or sum the rotor fatigue damage caused by each individual application of the brake. The cumulative damage of the rotor across multiple braking events can be calculated, for example, using Miner's rule, previously generated knowledge of loading or stress versus fatigue life behavior of the rotor. The stress versus life characterization is generated via physical testing in some embodiments and is characterized by the slope of the fitted curve on a logarithmic scale, known to those skilled in the art as an "SN" curve.Fatigue life is estimated in some embodiments by comparing the accumulated damage from all braking events involving the component since the rotor was installed to a validated rotor damage level or damage threshold. In some embodiments, the damage threshold or validated rotor damage level generally refers to the expected life of a rotor subject to heavy use in practice. In some embodiments, the cumulative fatigue damage model includes rotor wear determined by the rotor thickness estimation processor 18 to refine the calculation of cumulative fatigue damage to the brake rotor. In such an embodiment, the stress and corresponding damage would be calculated at the rotor face and also at discrete levels below the rotor face.The risk of brake rotor failure is predicted when the cumulative damage of a rotor layer exceeds a predetermined maximum threshold. In some embodiments, the stress is calculated using a one-dimensional thermal-mechanical stress model.

[0059] Processor 16 calculates the real-time fatigue damage of the brake component and the cumulative fatigue damage periodically at a predetermined frequency, such as every 10 ms, 20 ms, or another predetermined frequency. Alternatively or additionally, processor 16 calculates the real-time fatigue damage and cumulative fatigue damage each time a braking event occurs.

[0060] Processor 16 forwards the cumulative fatigue damage estimate to a brake component life estimation processor 20. The brake component life estimation processor 20 accumulates the cumulative fatigue damage of the brake component during operation of the motor vehicle over time. The accumulated cumulative fatigue damage of the brake component is compared to a brake component damage limit. The brake component damage limit, in some embodiments, is a limit determined by testing and validating the brake component, which in some embodiments is set by a predetermined safety factor.

[0061] The brake component life estimation processor 20 generates a brake component life estimate signal. In some embodiments, the life estimate signal is used alone or in combination with a wear model, such as rotor wear models 320, 330, to generate a refined rotor life estimate. The brake component life estimation processor 20, in one embodiment, estimates the life of a vehicle brake rotor. In some embodiments, the estimated life is expressed as a percentage of the remaining life of the brake component.

[0062] The distribution of information can be calibrated for different applications and different motor vehicles. An estimate of the amount of brake wear material is recorded on the motor vehicle, along with the mileage the motor vehicle has driven since the rotors were last changed. The current estimate can be stored in separate modules of the motor vehicle. This procedure is used to store the information in case a fault occurs on one of the modules and it needs to be replaced. An estimate of the motor vehicle's remaining mileage can be obtained in several ways, such as through the driver's braking characteristics, linear interpolation, or mileage lookup tables and estimation of the brake rotor thickness.The estimate of the remaining service life or life expectancy of the brake component is recorded on the motor vehicle and can be stored in separate modules on the motor vehicle for use in future calculations of the estimates of the total wear of the brake component.

[0063] If the system 10 includes a brake rotor sensor that provides signals indicative of the actual brake rotor thickness, the signals are used to gradually compensate for differences between the brake rotor thickness estimate and the actual thickness over the remaining rotor thickness and service life of the rotor 53. For example, the sensor may be set so that one or more wires break at a certain rotor thickness. If a significant difference exists between the estimate and the actual thickness, which is determined when the sensor wires break contact, this is used to gradually adjust the estimate so that when the rotor 53 is near the replacement period or the next sensor measurement, the overall system accuracy is as high as possible.For example, the estimate of the remaining rotor life is increased or decreased by a rate different from the observed rate so that the end of life of the rotor 53 is accurately determined.

[0064] It should be noted that although the brake sensor discussed above employs wires that break to indicate rotor thickness, other types of brake sensors may be used in other examples of system 10. For example, an indirect sensor or sensing mechanism may be used to infer brake rotor thickness. Suitable examples include brake fluid level sensors or measuring brake caliper displacement, such as in an electromechanical or break-by-wire system.

[0065] Fig. 4 shows a flowchart of an exemplary method for determining a remaining service life of a brake component, such as a brake disc. Fig. The method shown in Figure 4 may be used with the brake component life system discussed herein. The method includes receiving and collecting various signals, such as brake pressure, wheel speeds, vehicle speed, longitudinal acceleration, dynamic brake distribution, applied brake, etc., as shown at 410. The method further includes obtaining system estimates from the driveline controller 14, such as vehicle mass, road grade, amount of engine braking, rolling resistance, rotor area, etc., as shown at 415. The method further includes obtaining system estimates, such as brake temperature estimates, from the brake controller 12, as shown at 420. The method further includes calculating braking work from braking energy, as shown at 425. Braking energy is calculated, for example, according to equation (1).Braking energy can be calculated for any of the multiple brake rotors on the vehicle or can be a calculation per vehicle axle.

[0066] Additionally or alternatively, the method includes determining the braking work using braking power, for example, from equations (2) and (3), as shown in 430. In this calculation, the braking work is determined by the braking power and the braking pressure, such as provided by equation (2). Errors may sometimes occur when determining the mass of the motor vehicle for calculating braking energy, and the friction coefficient value µ may include errors in the estimation of braking power. Therefore, a more accurate determination of the braking work can be provided by combining the two work calculations.

[0067] The method further includes determining the brake rotor temperature as shown at 435 and determining the brake rotor wear as shown at 440 in the manner discussed above. Determining the brake rotor wear at 440 includes calculating the energy-based wear and the oxidation wear, and the total rotor wear is a sum of the two wear calculations. The brake rotor wear is determined for each braking event and is added to the accumulated value as shown at 445 to determine the remaining brake rotor thickness.

[0068] The method further includes determining brake rotor fatigue damage using the brake rotor temperature and the operating conditions of the motor vehicle, as shown at 450, in the manner discussed above. Determining brake rotor fatigue damage at 450 includes calculating the fatigue damage based at least in part on the braking torque, braking speed / power, and rotor temperature. The brake rotor fatigue damage is determined for each braking event and is added to the accumulated value, as shown at 445, to determine a cumulative fatigue damage estimate. As discussed herein, the cumulative fatigue damage estimate is a sum of the fatigue damage to the braking component, such as the brake rotor, and in some embodiments also includes the estimated brake rotor wear determined at 440.

[0069] The cumulative fatigue damage estimate determined in 455 is used to calculate the remaining life estimate of the brake rotor in 460. The remaining life estimate of the braking component, such as the brake rotor, is determined as discussed above by comparing the accumulated cumulative damage to a predetermined component damage limit.

[0070] The method includes sending the estimated thickness information to the vehicle operator as shown at 465 using, for example, vehicle telematics. Additionally or alternatively, the method at 465 includes sending the estimated remaining life to the vehicle operator using, for example, vehicle telematics.

[0071] Fig.5 is a flowchart of an exemplary method for notifying the vehicle operator of the estimated remaining life of the vehicle brake component, according to one or more embodiments. In some embodiments, the vehicle brake component is a brake rotor 53. The method includes determining, as shown at 505, whether the remaining life of the vehicle brake component is greater than a first predetermined threshold. The remaining life of the vehicle brake component is determined based on the process discussed herein. The first predetermined threshold is a predetermined value at which replacement of the brake component is recommended. For example, the threshold for replacement may be a proportional value, such as 50% of the originally expected life. It should be noted that the above values are examples, and other embodiments may use different thresholds than those noted above.

[0072] When the replacement threshold is reached, the vehicle operator is notified to replace the vehicle brake component, as shown in 515. For example, if the remaining life has not met the replacement threshold, the method includes determining whether the remaining life has reached a second predetermined threshold, as shown in 510. The second predetermined threshold may be a predetermined value representative of an inspection threshold. For example, the replacement threshold may be a proportional value, such as 75% of the original life. It should be noted that the above values are examples, and that other embodiments may use different thresholds than those noted above. When the inspection threshold is reached, the vehicle operator is notified that the vehicle brake component needs to be inspected, as shown in 525.

[0073] In one or more examples, regardless of the relationship between the remaining life and the thresholds, the vehicle operator is informed of the current estimated remaining life, as shown in 530. Further, the method includes, as shown in 520, determining a remaining life of the brake component based on the estimated wear of the brake component. For example, the life of the brake component may be measured in terms of an estimated number of kilometers the brake component may be used before the replacement threshold is reached. For example, as shown in 530, the method includes informing the vehicle operator of the remaining life of the brake component in kilometers using linear interpolation based on vehicle operation to date.The method thus makes it possible to notify the driver in any suitable way and, based on the current wear of the brake component, he can be informed of the remaining kilometers when the brake component should be replaced.

[0074] In one or more examples, the motor vehicle is an autonomous vehicle, wherein the vehicle driver is a processor unit. In such cases, the processor receives, for example, the estimated rotor thickness and / or the remaining life estimate and / or the remaining life estimate of the vehicle brake component. Based on such an indication, the vehicle driver processor unit automatically drives the motor vehicle to a repair shop. For example, if the rotor thickness falls below the inspection threshold, the processor unit causes the motor vehicle to be driven to the repair shop for rotor inspection. Alternatively or additionally, if the rotor thickness falls below the replacement threshold, the processor unit causes the motor vehicle to be driven to the repair shop for rotor replacement.In response to the rotor thickness comparison, other automatic actions can also be performed, such as scheduling vehicle maintenance.

[0075] Alternatively or additionally, the rotor thickness estimate and / or the remaining life estimate of the vehicle brake component are used to limit vehicle operation if one or more of the estimates falls below a predetermined value, such as the replacement threshold. For example, limiting vehicle operation may include limiting a maximum speed of the motor vehicle, limiting the torque generated by an engine of the motor vehicle, or imposing other such limits to maximize the safety of the passenger(s) of the motor vehicle.

[0076] It should be noted that, although the previous examples describe calculating the rotor thickness and using the calculated thickness to determine the service life of a rotor, in one or more examples, the rotor thickness of all rotors with which the motor vehicle is equipped is analyzed. Accordingly, the vehicle operator is informed of the rotor thickness and the rotor service life estimated for each rotor installed on the motor vehicle. Furthermore, although many of the examples discussed herein describe the analysis of a brake rotor, in other embodiments, the methods discussed herein are used to analyze other stress-intensive brake components.

[0077] The technical solutions described herein facilitate the prediction of rotor wear for a disc brake system by combining models based on energy and oxidative wear. The technical solutions predict brake disc wear over a wide range of vehicle usage and generate an electronic signal indicating disc wear / remaining life. Additionally, the technical solutions described herein enable the prediction of the life expectancy of one or more vehicle brake components by analyzing the component's real-time fatigue damage, accumulating the fatigue damage caused by each braking event, and comparing the accumulated fatigue damage to a predetermined damage threshold.Disc wear and / or remaining service life can be displayed to the driver and / or used in various control algorithms implemented by one or more electronic control units (ECUs) in the motor vehicle.

[0078] The technical solutions can save a vehicle owner from costly repairs resulting from excessive wear on a vehicle's brake component. Furthermore, the technical solutions can help fleet owners (such as autonomous vehicle fleets) monitor brake life (in combination with brake pad wear monitoring) to plan when motor vehicles need maintenance.

Claims

[1] A method for determining a remaining service life of a brake component, the method comprising: Providing vehicle parameters that identify the operating conditions of a motor vehicle; Using the vehicle parameters to determine work performed by a brake of the motor vehicle as braking work; Using braking work to determine brake rotor temperature; Using brake rotor temperature to determine brake component fatigue damage; Accumulating the fatigue damage to determine a cumulative fatigue damage of the brake component and Comparing the cumulative fatigue damage to a damage limit to provide an estimate of the remaining life of the brake component; wherein the brake component is a vehicle brake rotor and the fatigue damage is a thermal and mechanical energy-based damage calculation, and wherein the method further comprises: Using brake rotor temperature to determine energy-based brake rotor wear; Accumulating brake rotor wear to provide an estimate of the thickness of the vehicle brake rotor; Calculating oxidative brake rotor wear based on vehicle brake rotor exposure time; Calculating the brake rotor wear by summing the oxidative brake rotor wear and the energy-based brake rotor wear and Using brake rotor wear to determine cumulative fatigue damage of the vehicle brake rotor; wherein oxidative brake rotor wear is calculated by scaling the exposure time of the vehicle brake rotor with a given oxidative wear parameter. [2] The method of claim 1, wherein the predetermined oxidative wear parameter is specific to a material of the vehicle brake rotor. [3] The method of claim 1, wherein providing vehicle parameters includes providing brake rotor friction material, brake rotor cooling rate, vehicle mass, road gradient, dynamic brake distribution, vehicle weight distribution, vehicle speed, wheel speed, and brake pressure. [4] The method of claim 1, wherein determining the braking work includes subtracting the resistance values from the total work performed by the brake of the motor vehicle, the resistance values being forces that reduce the total work. [5] The method of claim 1, wherein determining braking work includes determining braking force as brake pressure times brake rotor area times brake rotor friction coefficient. [6] The method of claim 1, wherein determining braking work includes determining braking power as torque generated by the vehicle times vehicle speed divided by the rolling radius of a vehicle wheel. [7] The method of claim 1, further comprising notifying of the estimate of the remaining life of the brake component using telematics. [8] A vehicle braking system for determining a remaining service life of a braking component, the vehicle braking system including the braking component and a processor; and the processor being configured to carry out the method of any preceding claim.

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