Speed ​​control based on brake temperature

Abstract

The speed control process limits the speed of the vehicle so that the vehicle can be slowed down without the brakes overheating. The speed control process includes estimating the current temperature of at least one brake. The speed control process then calculates a speed limit for the vehicle that will prevent the brakes from exceeding a maximum temperature when slowing the vehicle to a stop, for example. The speed control process can limit the vehicle to below the speed limit by setting a motor torque limit.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Provisional Patent Application No. 63 / 374,218, filed August 31, 2022, the entire disclosure of which is incorporated by reference in its entirety for all purposes.

[0002] This application relates to a process for controlling the speed of a vehicle. More specifically, the process for controlling the speed may be based on an estimation of the braking performance of the vehicle. [Background technology]

[0003] Vehicle brakes slow a vehicle through friction between the brake pads and the vehicle's rotors. During braking, kinetic energy is converted into thermal energy. Therefore, when a vehicle brakes hard, repeatedly, and / or for long periods of time, heat can accumulate and overheat the brakes. When vehicle brakes overheat, fade can occur due to a loss or reduction in friction between the brake pads and rotors. Brakes can also suffer irreversible damage once they reach a certain temperature. Therefore, fade and permanent brake damage can occur when a vehicle is traveling at high speeds and / or for long periods of time, and the brakes may not function as expected and fail to slow the vehicle within the desired time or distance. Accurately understanding brake performance without explicit sensors can reduce cost and design complexity. Furthermore, proactive speed control based on estimation or prediction of brake performance can improve user safety by notifying and acting to limit potentially dangerous situations associated with reduced brake performance or loss of function. Summary of the Invention

[0004] FIELD OF THE DISCLOSURE The present disclosure relates generally to a process for controlling the speed of a vehicle. More particularly, various embodiments of the present disclosure relate to a process for controlling the speed of a vehicle based on an estimation of brake temperature.

[0005] One aspect relates to a method for controlling a vehicle's speed based on braking performance, the method including estimating a current temperature of brakes of the vehicle. The brakes may have a maximum operating temperature. The method further includes determining a thermal margin for the brakes and determining a speed limit for the vehicle. The speed limit may be based at least in part on the thermal margin. The method also includes enforcing the speed limit on the vehicle.

[0006] In a variation of the above aspect, determining the speed limit includes determining road conditions for the vehicle.

[0007] In a variation of the above embodiment, the brakes are the hottest brakes on the vehicle at the time of temperature estimation.

[0008] In a variation of the above aspect, the thermal margin includes an amount of thermal energy that, if absorbed by the brake, would raise the temperature of the brake from its current temperature to its maximum operating temperature.

[0009] A variation of the above aspect further includes determining a torque limit for a motor of the vehicle. The torque limit can be based at least in part on the speed limit. The method further includes applying the torque limit to the vehicle.

[0010] In a variation of the above aspect, determining a speed limit for the vehicle includes estimating a current temperature, determining a thermal margin, determining the speed limit based at least in part on the thermal margin for each brake of the vehicle, and selecting a minimum speed limit as the speed limit for the vehicle.

[0011] In a variation of the above aspect, the current temperature of the vehicle's brakes is estimated based at least in part on brake pressure data and / or the current speed of the vehicle.

[0012] Another aspect relates to a system for controlling a vehicle's speed based on braking performance. The system includes a processor configured to estimate a current temperature of brakes of the vehicle, the brakes having a maximum operating temperature. The processor may also be configured to determine a thermal margin for the brakes and to determine a speed limit for the vehicle. The speed limit may be based at least in part on the thermal margin. The processor may also be configured to enforce a speed limit on the vehicle.

[0013] In a variation of the above aspect, the thermal margin includes an amount of thermal energy that, if absorbed by the brake, would raise the temperature of the brake from its current temperature to its maximum operating temperature.

[0014] In a variation of the above aspect, the processor is configured to determine a torque limit for a motor of the vehicle, the torque limit being based at least in part on the speed limit, and the processor is also configured to apply the torque limit to the vehicle.

[0015] In a variation of the above aspect, calculating the torque limit further includes determining road conditions for the vehicle.

[0016] In a variation of the above embodiment, the brakes are the hottest brakes on the vehicle at the time of temperature estimation.

[0017] In a variation of the above aspect, the processor is further configured to measure the current temperature, determine a thermal margin, determine a speed limit based at least in part on the thermal margin for each brake of the vehicle, and select the minimum speed limit as the speed limit for the vehicle.

[0018] In a variation of the above aspect, the current temperature of the vehicle's brakes is estimated based at least in part on brake pressure data and / or the current speed of the vehicle.

[0019] Another aspect relates to a method for controlling a speed of a vehicle based on braking performance, the method including estimating a current temperature of brakes of the vehicle. The brakes may have a maximum operating temperature. The method further includes determining a thermal margin for the brakes and determining a torque limit for the vehicle. The torque limit may be based at least in part on the thermal margin. The method also includes applying the torque limit to the vehicle.

[0020] In a variation of the above aspect, determining the torque limit includes determining road conditions for the vehicle.

[0021] In a variation of the above aspect, the brakes are the hottest brakes on the vehicle at the time of temperature estimation.

[0022] In a variation of the above aspect, the thermal margin includes an amount of thermal energy that, if absorbed by the brake, would raise the temperature of the brake from its current temperature to its maximum operating temperature.

[0023] In a variation of the above aspect, determining a speed limit for the vehicle includes estimating a current temperature, determining a thermal margin, determining the speed limit based at least in part on the thermal margin for each brake of the vehicle, and selecting a minimum speed limit as the speed limit for the vehicle.

[0024] In a variation of the above aspect, the current temperature of the vehicle's brakes is estimated based at least in part on brake pressure data and / or the current speed of the vehicle. [Brief explanation of the drawings]

[0025] The present disclosure will be described with reference to the accompanying drawings, in which like reference numerals refer to like elements.

[0026] [Figure 1] 1 is an exemplary chart illustrating a mapping of torque limit as a function of speed limit and brake temperature.

[0027] [Figure 2] 2 is the exemplary chart of FIG. 1 with the addition of a torque vs. speed line at a temperature of 25° C. and a torque vs. speed line at a temperature of 500° C.

[0028] [Figure 3] 3 is the example chart of FIG. 2 with an envelope curve formed between the three lines.

[0029] [Figure 4] 10 shows exemplary simulation results recording temperature versus time performed at different temperature limits and with different test profiles.

[0030] [Figure 5] 10 shows exemplary simulation results recorded at different temperature limits and speed versus time performed with different test profiles.

[0031] [Figure 6] 10 shows exemplary simulation results recording torque versus time performed at different temperature limits and different test profiles.

[0032] [Figure 7] FIG. 1 shows a block diagram illustrating an exemplary speed control system according to the present disclosure.

[0033] [Figure 8] 1 shows a flow diagram illustrating an exemplary rate control process according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0034] Generally described, one or more aspects of the present disclosure relate to a process for controlling the speed of a vehicle. In particular embodiments, the present disclosure relates to a process for controlling the speed of a vehicle based on an estimate of brake temperature. The process for controlling the speed can include estimating brake temperature using a thermal model. The brake thermal model can vary for vehicles with different weights, configurations, and speed / braking mechanisms. In some embodiments, the brake thermal model can provide an estimate of brake temperature without a temperature sensor. The brake thermal model can provide information about the remaining thermal margin and thermal performance of the vehicle's braking system. For example, the thermal margin, or the amount of thermal energy required to raise each brake above its maximum temperature (e.g., the temperature at which the brakes may fade or fail), can be calculated using the brake temperature estimate from the brake thermal model.

[0035] The speed control process may further include using a vehicle model to determine the maximum speed the vehicle can reach when the brakes are at a particular temperature. Within the maximum speed limit, the vehicle brakes may be actuated to safely slow the vehicle without degradation or loss of friction-generating performance (e.g., without exceeding a maximum temperature at which the brakes may fade or fail). In some embodiments, as shown in FIG. 7, the vehicle model may employ a speed control system 100 that uses vehicle model data 110. In some embodiments, the vehicle model data 110 may include vehicle brake pressure data 112 and vehicle speed data 114. The vehicle model data 110 may be used by a processing component 120 to calculate and convert thermal performance into a vehicle-specific maximum vehicle speed.

[0036] 8 , when a vehicle is traveling at a particular speed, processing component 120 of speed control system 100 can estimate the current brake temperature using a thermal model in step 1002. In step 1004, in some embodiments, processing component 120 of speed control system 100 can calculate the thermal performance of the braking system (e.g., the amount of thermal energy required to raise each brake above its maximum temperature) using the current estimated brake temperature and other data (e.g., the thermal capacity of the brakes) for the particular vehicle model from vehicle model data 110. Then, in step 1006, in some embodiments, speed control system 100 can then convert the thermal performance to a maximum vehicle speed using vehicle model data 110 (e.g., the vehicle's mass) from the vehicle model.

[0037] In some embodiments, in step 1008, the processing component 120 of the speed control system 100 can further calculate operational limits (e.g., torque limits for the vehicle engine or electric motor) that can limit the vehicle to the determined speed limit. In some embodiments, the vehicle can be limited to traveling at or below the speed limit, for example, as long as the motor is controlled to apply a torque that does not exceed the torque limit. In some embodiments, the speed control system 100 can further include a control component 130 that can be configured to receive and implement operational limits to control the speed of the vehicle, for example, by controlling the vehicle engine or electric motor, in step 1010. The calculation of operational limits can also depend on many variables, such as the condition and incline of the road on which the vehicle is traveling. In some embodiments, the speed control process can also include determining the torque limit using road gradient information. For example, if the vehicle is traveling on a flat road, the torque limit may be set low to limit the vehicle at a certain speed limit.

[0038] In some embodiments, the speed control system 100 may also be implemented in a vehicle with a regenerative braking system by using a set of vehicle data and calculations specific to the regenerative braking system.

[0039] A vehicle may include a brake on each drive axle (e.g., a front brake and a rear brake). In some embodiments, the speed control process may be calculated based on a temperature estimate of all brakes on the vehicle and then apply a minimum speed limit to prevent degradation or loss of function of any brake. In some embodiments, the speed control process may be calculated based on an estimated maximum temperature for all brakes. In some embodiments, the estimated maximum temperature is the front axle brake. In some embodiments, the estimated maximum temperature is the rear axle brake. In some embodiments, the speed control process may be calculated based on an estimated temperature of only the front axle brake. In other embodiments, the speed control process may be calculated based on other performance estimates or predictions of one or more brakes on the vehicle.

[0040] 1-3 are exemplary charts mapping torque limits as a function of speed limit and brake temperature, where X is speed, Y is temperature, and Z is torque limit. Line 10 in FIG. 1 illustrates how torque limits can correspond to speed limits and brake temperatures for a particular vehicle model under certain conditions using a speed control process according to the present disclosure. For example, if the vehicle's brake temperature is estimated to be Y2°C, the vehicle can be limited to X2 mph or less. Below Z2 mph, the remaining performance or capacity of the brake system is sufficient to safely stop the vehicle. To maintain a speed of Z2 mph, the vehicle can limit the motor torque output to Z2 Nm. That is, according to FIG. 1, by applying the speed control process under certain conditions, the vehicle can be configured to operate under a torque limit of Z2 Nm and travel at or below X2 mph when the brake temperature is estimated to be Y2°C. The flat portion of line 10, where the Z value is constant (e.g., Z3 Nm), corresponds to the torque value required to maintain the vehicle's corresponding speed limit. In certain embodiments, the flat portion corresponds to a temperature and speed range where torque limits are not actually applied according to the speed control process. FIG. 1 shows that in some embodiments, the speed control process can use the function represented by line 10 to determine speed and / or torque limits based on brake temperature.

[0041] FIG. 2 adds an exemplary system-level torque versus speed line 20 at a brake temperature of Y4° C. (e.g., 500° C.) and an exemplary torque versus speed line 30 at a temperature of Y5° C. (e.g., 25° C.) to the chart of FIG. 1 to form the boundaries of the torque output limit envelope. The flat portions of lines 20 and 30 with constant Z values ​​(e.g., Z4 Nm on line 20 and Z5 Nm on line 30) correspond to the torque values ​​required to maintain the vehicle's corresponding speed limit. In certain embodiments, the flat portions correspond to the temperature and speed ranges where no torque limit is actually applied pursuant to the speed control process. In some embodiments, line 20 is added at a brake temperature of 500° C. because at that temperature, the remaining performance or capacity of the brake system is sufficient to safely stop the vehicle from its maximum speed. In some embodiments, lines 20 and 30 can be added at temperatures of 600° C. and 0° C. In other embodiments, wires 20 and 30 can be applied at any other desired temperature based on various considerations and factors (eg, different brake materials, vehicle conditions, and road conditions).

[0042] Figure 3 is the chart of Figure 2 with envelope 40 formed by continuously integrating lines 20 and 30 with line 10. Envelope 40 can define torque limits relative to speed and brake temperature coordinates. Figure 3 shows that in some embodiments, a speed control process can use the functions represented by lines 10, 20, 30 and envelope 40 to determine speed and / or torque limits based on brake temperature.

[0043] 4-6 are exemplary simulation results performed with different temperature limits and different test profiles. FIG. 4 shows simulation results recording temperature versus time. FIG. 5 shows simulation results recording speed versus time. FIG. 6 shows simulation results recording torque versus time. As shown in FIGS. 4-6, the speed control process can be tested and fine-tuned with different temperature limits (e.g., the maximum brake temperature considered acceptable) and different test profiles (e.g., adjusting the speed from 0 mph to 134 mph and back to 0 mph, as shown in the first row of each of FIGS. 4-6).

[0044] As shown in Figure 4, each chart shows a line where the temperature, i.e., y value, does not exceed a preset temperature limit (e.g., 800°C, 850°C, etc.). These results can be taken as an indication that the implemented speed control process is effective in controlling the brake temperature so that it is below the preset allowable temperature limit for the brake.

[0045] As shown in Figure 5, each chart shows a line of speed, or y-value, corresponding to a speed prescribed in the test profile (e.g., 0-134-0 mph, 50-80-50 mph, etc.). These results can be used as an indication that the implemented speed control process is effective in controlling the speed limit so that it remains below the vehicle's determined speed limit.

[0046] 6, each chart shows a torque maximum line 100 recording the maximum torque allowable under the current brake temperature and speed, a torque limit line 200 recording the torque limit determined by the speed control process under the brake temperature and speed, and an actual torque line 300 recording the actual applied torque. These results, showing that torque limit line 200 is below torque maximum line 100 and actual torque line 300 is below that, can be an indication that the implemented speed control process is effective in enforcing the torque limit determined by the speed control process to control speed under different temperature limits and test profiles.

[0047] In certain embodiments, the speed control process may include determining and communicating a preferred front and rear brake bias to improve thermal performance. A vehicle's front and rear brakes often operate under different pressures due to their different roles, configurations, and locations within the vehicle. Adjusting the ratio of braking force (e.g., brake bias) between the front and rear brakes can maximize overall braking efficiency. The preferred front and rear brake bias may be learned by the speed control process, for example, by determining the maximum allowable temperature of the front and rear brakes, the torque applied to the front and rear brakes, and related information.

[0048] The foregoing disclosure is not intended to limit the disclosure to the precise form or particular field of use disclosed. Accordingly, various alternative embodiments and / or modifications of the disclosure, whether expressly described or implied herein, are contemplated in light of the present disclosure. While embodiments of the present disclosure have been described in this manner, those skilled in the art will recognize that changes can be made in form and detail without departing from the scope of the present disclosure. Accordingly, the present disclosure is limited only by the scope of the claims.

[0049] In the foregoing specification, the present disclosure has been described with reference to specific embodiments. However, as will be understood by those skilled in the art, the various embodiments disclosed herein can be modified or embodied in a variety of other ways without departing from the spirit and scope of the present disclosure. Accordingly, this description is to be considered illustrative and is intended to teach those skilled in the art how to make and use various embodiments of the disclosed rate control process. It should be understood that the forms of the disclosure shown and described herein are to be taken as representative embodiments. Equivalent elements, materials, processes, or steps may be substituted for those typically shown and described herein. Furthermore, certain features of the present disclosure may be utilized independently of the use of other features, all of which will be apparent to those skilled in the art after having the benefit of the present disclosure herein. The terms "including," "comprising," "incorporating," "consisting of," "having," "being," and the like, used to describe and claim the present disclosure, are intended to be construed in a non-exclusive manner, i.e., allowing for the presence of items, components, or elements not expressly recited. References to the singular should also be construed to relate to the plural.

[0050] Furthermore, the various embodiments disclosed herein should be taken in an exemplary and explanatory sense and should not be construed as controlling in any way. All joint references (e.g., attached, secured, coupled, connected, etc.) are used solely to aid the reader's understanding of the disclosure and do not create limitations regarding the position, orientation, or use of the systems and / or methods disclosed herein, among other things. Accordingly, any reference to a joint should be interpreted broadly. Furthermore, such a reference to a joint does not necessarily infer that two elements are directly connected to one another. Additionally, without limitation, all numerical terms, such as "first," "second," "third," "primary," "secondary," "main," or any other conventional and / or numerical term, should also be taken solely as identifiers to aid the reader's understanding of the various elements, embodiments, variations, and / or modifications of the disclosure, and in particular, may not create any limitations regarding the order or priority of any element, embodiment, variation, and / or modification relative to or over another element, embodiment, variation, and / or modification.

[0051] It will also be understood that one or more of the elements depicted in the drawings / diagrams may be implemented in a more separated or integrated manner, or even removed or rendered inoperable in certain cases, as may be useful depending on the particular application.

Claims

1. 1. A method for controlling vehicle speed based on braking performance, comprising: estimating a current temperature of the vehicle's brakes, the brakes having a maximum operating temperature; determining a thermal margin for the brake; determining a speed limit for the vehicle, the speed limit being based at least in part on the thermal margin; applying the speed limit to control the speed of the vehicle; A method comprising:

2. The method of claim 1 , wherein the step of determining a speed limit includes determining road conditions for the vehicle.

3. The method of claim 1 , wherein the brakes are the hottest brakes on the vehicle at the time of temperature estimation.

4. The method of claim 1 , wherein the thermal margin comprises an amount of thermal energy that, if absorbed by the brake, would raise the temperature of the brake from a current temperature to a maximum operating temperature.

5. determining a torque limit for a motor of the vehicle, the torque limit being based at least in part on the speed limit; applying the torque limit to the vehicle; The method of claim 1 further comprising:

6. 2. The method of claim 1, wherein determining a speed limit for the vehicle includes estimating a current temperature; determining a thermal margin; determining a speed limit based at least in part on the thermal margin for each brake of the vehicle; and selecting a minimum speed limit as the speed limit for the vehicle.

7. The method of claim 1 , wherein the current temperature of the vehicle's brakes is estimated based at least in part on the brake pressure data and / or the current speed of the vehicle.

8. 1. A system for controlling vehicle speed based on braking performance, comprising: estimating a current temperature of the vehicle's brakes, the brakes having a maximum operating temperature; determining a thermal margin for the brake; determining a speed limit for the vehicle, the speed limit being based at least in part on the thermal margin; applying the speed limit to control the speed of the vehicle; 1. A system comprising: a processor configured to:

9. 7. The speed control system of claim 6, wherein the thermal margin comprises an amount of thermal energy that, if absorbed by the brake, would raise the temperature of the brake from a current temperature to a maximum operating temperature.

10. The processor: determining a torque limit for a motor of the vehicle, the torque limit being based at least in part on the speed limit; applying the torque limit to the vehicle; The speed control system of claim 6 configured to:

11. 7. The speed control system of claim 6, wherein the step of calculating the torque limit includes determining road conditions for the vehicle.

12. 7. The speed control system of claim 6, wherein the brake is the hottest brake on the vehicle at the time of temperature estimation.

13. 10. The speed control system of claim 8, wherein the processor is further configured to estimate a current temperature, determine a thermal margin, determine a speed limit based at least in part on the thermal margin for each brake of the vehicle, and select a minimum speed limit as the speed limit for the vehicle.

14. 10. The speed control system of claim 8, wherein the current temperature of the vehicle's brakes is estimated based at least in part on pressure data of the brakes and / or the current speed of the vehicle.

15. 1. A method for controlling vehicle speed based on braking performance, comprising: estimating a current temperature of the vehicle's brakes, the brakes having a maximum operating temperature; determining a thermal margin for the brake; determining a torque limit for a motor of the vehicle, the torque limit being based at least in part on the thermal margin; applying the torque limit to limit the speed of the motor; A method comprising:

16. The method of claim 15 , wherein the step of determining a torque limit includes determining road conditions for the vehicle.

17. The method of claim 15, wherein the brake is the hottest brake on the vehicle at the time of temperature estimation.

18. The method of claim 15 , wherein the thermal margin comprises an amount of thermal energy that, if absorbed by the brake, would raise the temperature of the brake from a current temperature to a maximum operating temperature.

19. 16. The method of claim 15, wherein determining a speed limit for the vehicle includes estimating a current temperature, determining a thermal margin, determining a speed limit based at least in part on the thermal margin for each brake of the vehicle, and selecting a minimum speed limit as the speed limit for the vehicle.

20. The method of claim 15 , wherein the current temperature of the vehicle's brakes is estimated based at least in part on the brake pressure data and / or the current speed of the vehicle.

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