Patent Application
20230211766
The subject disclosure relates to brake fluids used in brakes on vehicles and, in particular, a method for determining a remaining life of a brake fluid based on continuous fluid level and quality measurements.
A brake system of an automobile or a vehicle is used to control and slow the rotation of wheels of the vehicle. An integral part of the brake system is a brake fluid that is used for hydraulic operation of a brake pad. The brake fluid can deteriorate over time, degrading the operation of the brake system. Current brake fluid sensors only provide an alarm when the brake fluid achieves a certain fluid level in its reservoir. Such sensors do not provide a thorough knowledge of the remaining usefulness of the brake fluid. Accordingly, it is desirable to provide a system and method that can determine a health of the brake fluid at any time in the life of the brake fluid.
In one exemplary embodiment, a method of monitoring a condition of a brake fluid is disclosed. A fluid level of the brake fluid within a reservoir is measured at a first sensor. A concentration of the brake fluid is measured at a second sensor. A temperature of the brake fluid is measured at a third sensor. The condition of the brake fluid is estimated from the fluid level, the concentration and the temperature at a processor. A signal is sent to a display, the signal being indicative of the condition of the brake fluid.
In addition to one or more of the features described herein, the method further includes determining a wear on a brake pad based on at least one of the condition of the fluid and a rate of depletion of the brake fluid. The condition of the brake fluid is at least one of a remaining useful life of the brake fluid, a presence of water in the brake fluid, a chemical composition of the brake fluid, and a level of oxidation of the brake fluid. Wherein the reservoir is disposed on a vehicle, the method further includes applying a filter to a measurement of the fluid level to compensate the measurement for a motion of the, wherein the filter is based on dynamics of the vehicle. The method further includes comparing the fluid level, the concentration and the temperature to at least one of simulated data and historical data. The method further includes detecting replacement of a brake pad from a discontinuity in the fluid level. Measuring the fluid level includes determining obtaining a plurality of measurements of the fluid level over time.
In another exemplary embodiment, a system for monitoring a condition of a brake fluid is disclosed. The system includes a first sensor configured to measure a fluid level of the brake fluid within a reservoir, a second sensor configured to measure a concentration of the brake fluid, a third sensor configured to measure a temperature of the brake fluid, and a processor. The processor is configured to estimate the condition of the brake fluid from the fluid level, the concentration and the temperature and send a signal to a display, the signal indicative of the condition of the brake fluid.
In addition to one or more of the features described herein, the processor is further configured to determine a wear on a brake pad based on at least one of the condition of the fluid and a rate of depletion of the brake fluid. The condition of the brake fluid is at least one of a remaining useful life of the brake fluid, a presence of water in the brake fluid, a chemical composition of the brake fluid, and a level of oxidation of the brake fluid. Wherein the reservoir is disposed on a vehicle, the processor is further configured to apply a filter to a measurement of the fluid level to compensate the measurement for a motion of the, wherein the filter is based on dynamics of the vehicle. The processor is further configured to compare the fluid level, the concentration and the temperature to at least one of simulated data and historical data. The processor is further configured to detect a replacement of a brake pad from a discontinuity in the fluid level. The first sensor is further configured to measure the fluid level by obtaining a plurality of measurements of the fluid level over time.
In yet another exemplary embodiment, a vehicle is disclosed. The vehicle includes a reservoir having a brake fluid therein, a first sensor configured to measure a fluid level of the brake fluid in the reservoir, a second sensor configured to measure a concentration of the brake fluid, a third sensor configured to measure a temperature of the brake fluid, and a processor. The processor is configured to estimate a condition of the brake fluid from the fluid level, the concentration and the temperature and send a signal to a display, the signal indicative of the condition of the brake fluid.
In addition to one or more of the features described herein, the processor is further configured to determine a wear on a brake pad based on at least one of the condition of the fluid and a rate of depletion of the brake fluid. The condition of the brake fluid is at least one of a remaining useful life of the brake fluid, a presence of water in the brake fluid, a chemical composition of the brake fluid, and a level of oxidation of the brake fluid. The processor is further configured to apply a filter to a measurement of the fluid level to compensate the measurement for a motion of the, wherein the filter is based on dynamics of the vehicle. The processor is further configured to compare the fluid level, the concentration and the temperature to at least one of simulated data and historical data. The processor is further configured to detect a replacement of a brake pad from a discontinuity in the fluid level.
The above features and advantages, and other features and advantages of the disclosure are readily apparent from the following detailed description when taken in connection with the accompanying drawings.
Other features, advantages and details appear, by way of example only, in the following detailed description, the detailed description referring to the drawings in which:
The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
In accordance with an exemplary embodiment,
The vehicle 100 includes a vehicle dynamics sensor 106 that obtain measurements of dynamic parameters of the vehicle 100. The vehicle dynamics sensor 106 can refer to a plurality of dynamics sensors. The dynamic parameters can include, but are not limited to, a vehicle grade or incline of the vehicle from horizontal, a pitch of the vehicle, a roll of the vehicle, a yaw of the vehicle, a longitudinal acceleration of the vehicle, a lateral acceleration of the vehicle, and a commanded brake torque of the vehicle.
The vehicle 100 also includes a controller 108 that performs various operations at the vehicle. The brake system 102 and the vehicle dynamics sensor 106 are in communication with the controller 108 and provide their measurements to the controller. The controller 108 includes a processor 110 and a computer readable storage device or storage medium 112. The storage medium 112 includes programs or instructions 114 that, when executed by the processor 110, allow the processor to estimate a remaining life of the brake fluid based on the measurements obtained from the brake system 102 and from the vehicle dynamics sensor 106. The remaining life estimate can be sent to a display 116 to alert a user of a need for a brake pad change, brake fluid replacement or other maintenance procedure.
A fluid level sensor 210 (first sensor) is coupled to the reservoir 202 and measures the level of the brake fluid 204 within the reservoir 202. The fluid level sensor 210 is a continuous sensor. In other words, the fluid level sensor 210 measures a fluid level at any height within a range of fluid levels of the reservoir 202. The measurements can be obtained at a plurality of times. A fluid quality sensor 212 (second sensor) is also coupled to the reservoir 202. The fluid quality sensor 212 measures a concentration or chemical composition of the brake fluid 204. For example, the fluid quality sensor 212 can detect an amount of a foreign fluid, such as water or other contaminant, in the brake fluid 204. Also, the fluid quality sensor 212 can measure an amount of oxidation in the brake fluid 204 in the reservoir 202. The oxidation of the brake fluid indicates a degradation of the brake fluid. The presence of oxidized brake fluid lowers a boiling point of the brake fluid. The concentration of the brake fluid 204 can thus be used to determine an amount of contamination or deterioration of the brake fluid. The fluid quality sensor 212 is capable of concentration measurements at any selected time. A temperature sensor 214 (third sensor) is coupled to the reservoir 202 and is capable of measuring a temperature of the brake fluid 204 at any selected time. Understanding the temperature of the brake fluid 204 in combination with the concentration measurements allows one to determine the overall quality of the fluid at an instant in time. For example, the presence of water in the brake fluid 204 (due to its hydroscopic nature) under low temperatures can change the viscosity of the brake fluid, and therefore affect the sloshing behavior.
In box 402, the temporal measurements of the level of the brake fluid 204 are obtained. In box 404, the concentration/quality of the brake fluid is measured. In box 406, a brake fluid compatibility is determined from the brake fluid concentration and the brake fluid quality. The concentration sensor determines if the medium filling the brake system is in fact brake fluid based on a calibration made to a correct brake fluid concentration. Based on the fluid concentration measurement, it can be determined whether the correct type of brake fluid has been added to the reservoir 202. For example, if a foreign or unexpected fluid (such as an incompatible type of brake fluid, other automotive fluids, or water) is detected in the reservoir 202 by the quality sensor, it is important to flag this data (at box 406) before sending the data for use in the brake fluid health monitor algorithm (box 410). In box 408, temperature measurements are obtained from temperature sensor 214.
In box 410, the processor estimates a brake fluid condition from boxes 402, 404 and 408. The estimation of brake fluid condition can be based on a comparison of the brake fluid level, fluid concentration and temperature to data obtained from a simulation (box 412) and/or historical data (box 414). In box 412, a simulation is performed that determine normal fluid quality deterioration using a model. The measurements of boxes 402, 404 and 408 can be compared to the simulated data to estimate the brake fluid condition. Box 414 includes historical data from other in-field measurements. The measurements of boxes 402, 404 and 408 can be compared to the historical data to estimate the brake fluid condition. Additionally, the measurements of boxes 402, 404 and 408 can then be stored as historical data for future calculations.
In box 416, a signal can be sent (e.g., to the display 116) to indicate, based on the estimated brake fluid condition, that the brake fluid is incompatible with the vehicle 100 and that the vehicle should be serviced and the brake fluid replaced. In box 418, the estimate of the brake fluid condition can be used to estimate a remaining life of the brake fluid. The remaining life can be quantified in various dimensions, such as remaining distance (e.g., in kilometers), a percentage, and/or a remaining time.
In box 604, the brake fluid level in the brake fluid reservoir is measured. The brake fluid level is either a continuous measurement or a plurality of measurements obtained over time, or both.
In box 606 a slosh filter is applied to the brake fluid level measurements obtained in box 604. The slosh filter is based on the dynamic vehicle parameters obtained in box 602. The slosh filter outputs an adjusted brake fluid level that corrects fluid level measurements for the dynamic motion of the vehicle. Table 1 illustrates decision method for a slosh filter, in an illustrative embodiment.
In a first row, the vehicle grade or incline is determined and, if above a threshold, is used to correct the fluid level measurements. In a second row, the lateral and/or longitudinal acceleration of the vehicle is measured. Corrections are made to the fluid level to account of the effects of the lateral and/or longitudinal acceleration on the fluid level measurement. In a third row, a commanded brake torque is measured. If the commanded brake torque is greater than or approximately zero, the filter is warned to expect sloshing of the brake fluid and to compensate for a flutter in the fluid level measurements.
The testing results obtained using Table 1 generate a slosh detection flag that indicates whether there is any amount of sloshing of the brake fluid 204 in the reservoir 202. In an embodiment, if the results of the slosh filter indicate that sloshing is expected, the measured data points (i.e., fluid level, etc.) can be recorded for historical data without making any immediate control changes based of the status of the brake fluid condition.
Box 608 includes a model that simulates normal brake pad wear over time given various usage scenarios. Box 610 includes historical data of brake pad wear for a given usage time for the brake pad 120. Box 612 receives the continuous fluid level measurements from box 604, the filtered brake fluid level from box 604, the simulated data from box 608 and the historical data from box 610 and estimates an amount of brake wear based on a comparison of the measurements to either the simulation data or the historical data or both.
While the above disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from its scope. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed, but will include all embodiments falling within the scope thereof
