Method for monitoring a braking system for a vehicle

Abstract

Method for monitoring a braking system (30) for a vehicle (10), the method comprising: Detecting a braking event; Determining the applied braking force during the braking event; and Monitoring of a total stopping distance during the braking event and a holding time via a sensor (55); characterized by Integrating the applied braking force during the braking event; Evaluating the braking system (30) via a controller (60) based on the total stopping distance, holding time and the integrated applied braking force during the braking event; Determining a fault associated with the braking system (30) based on the evaluation of the braking system (30); and Communicating the fault associated with the braking system (30) via the control unit (60).

Description

[0001] The present invention relates to a method according to the preamble of claim 1 for monitoring a braking system for a vehicle, as is essentially known from EP 2 902 278 A1. Further prior art can be found in US 2015 / 0 100 190 A1. INTRODUCTION

[0002] Vehicles may include on-board monitoring systems to monitor and identify any need for system maintenance and / or servicing.

[0003] The invention is based on the object of specifying a method with which the braking system of a vehicle can be monitored particularly reliably for possible malfunctions. SUMMARY

[0004] This object is achieved by a method having the features of claim 1.

[0005] Further described is a braking system for a vehicle. The braking system includes devices configured to apply a braking force to a wheel in response to a braking command. A first sensor is arranged to monitor a parameter associated with the braking force, and a spatial sensor is arranged to determine a linear range between the vehicle and a predefined location. A controller is operatively connected to the braking system and in communication with the first sensor and the spatial sensor. The controller includes an instruction set executable to detect a braking event and determine an applied braking force during the braking event, which can be integrated over a time to stop.The total stopping distance during the braking event is monitored, and the braking system is evaluated based on the total stopping distance, the stopping time, and the integrated braking force during the braking event. A fault associated with the braking system is determined based on the braking system evaluation and communicated via a controller.

[0006] One aspect of the invention includes determining a state of health (SOH) for the braking system based on the evaluation of the total stopping distance, the stopping time and the integrated applied braking force during the braking event and communicating the SOH for the braking system to a vehicle operator via a human-machine interface device when the SOH is less than a threshold SOH.

[0007] Another aspect of the invention includes determining a state of health (SOH) for the braking system based on the evaluation of the total stopping distance, the stopping time and the integrated applied braking force during the braking event and communicating the SOH for the braking system to an off-board controller via a telematics device when the SOH is less than a threshold SOH.

[0008] Another aspect of the invention includes determining a setting of the applied braking force during a subsequent braking event based on the total stopping distance and the integrated applied braking force during the braking event.

[0009] Another aspect of the invention includes determining an initial vehicle speed to initiate the braking event and evaluating the braking system via the controller based on the initial vehicle speed, the total stopping distance, and the integrated applied braking force during the braking event.

[0010] Another aspect of the invention includes the in-vehicle sensor that monitors the total stopping distance during braking and is one of a lidar device, a radar device, a global positioning system, or an ultrasonic device.

[0011] Another aspect of the invention includes the sensor that monitors the applied braking force during the braking event, which is a pressure sensor arranged to monitor the hydraulic brake pressure in a master cylinder of the braking system.

[0012] Another aspect of the invention includes the sensor that monitors the applied braking force during the braking event, which is a sensor arranged to monitor the displacement of a brake piston of the braking system.

[0013] Another aspect of the invention involves communicating the need to service the braking system to an off-board controller via a telematics device.

[0014] Another aspect of the invention includes evaluating the braking system based on the total stopping distance, the stopping time, and the integrated applied braking force during the braking event, including determining an average deceleration rate based on the total stopping distance and evaluating the braking system based on a ratio between the integrated applied braking force and the average deceleration rate.

[0015] The above features and advantages, as well as other features and advantages of the present teachings, will become more apparent from the following detailed description of some of the best modes and other embodiments for carrying out the present teachings, as defined in the appended claims, with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In the following, one or more embodiments are described by way of example with reference to the accompanying drawings, in which: Fig. Figure 1 schematically illustrates a portion of a vehicle with a vehicle braking system and associated controls according to the invention; and Fig. Figure 2 schematically illustrates an information flow diagram for a brake monitoring routine associated with the operation of the vehicle, which is provided according to the invention with reference to Fig. 1 is described.

[0017] It should be understood that the accompanying drawings are not necessarily to scale and present a somewhat simplified representation of various preferred features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, positions, and shapes. Details pertaining to such features will be determined in part by the particular intended application and use environment. DETAILED DESCRIPTION

[0018] With reference to the drawings, in which like reference numbers correspond to like or similar components in the various figures, Fig.1, in accordance with the embodiments disclosed herein, a vehicle 10 includes a braking system 30 for applying braking force to a vehicle wheel 20 and an associated braking controller 50 illustrating the concepts described herein. The vehicle 10 may be equipped with an autonomous controller 60 implementing autonomous vehicle functionalities in one embodiment. The vehicle 10, in one embodiment, includes a four-wheel drive passenger vehicle with steerable front and rear wheels. The vehicle 10 may be, by way of non-limiting examples, a passenger car, a light or heavy-duty vehicle, a multi-purpose vehicle, an agricultural vehicle, an industrial / warehouse vehicle, or a recreational off-road vehicle.

[0019] The vehicle wheel 20 is mounted on an axle section that includes a rotatable disc 22 and a wheel speed sensor 24 arranged to monitor the rotational position and speed of the disc 22 and thus of the wheel 20. The braking system 30, in one embodiment, includes a brake caliper 34, a brake actuator 36, and a master cylinder 32 that cooperate to generate hydraulic pressure for applying a braking force to the disc 22 to perform wheel braking during a braking event. A pressure sensor 38 is arranged in the master cylinder 32 to monitor the hydraulic pressure and the associated applied braking pressure. Brake pressure is a metric associated with the applied braking force, which can be sensed during a braking event. Other metrics related to braking force may be used.Alternatively or additionally, other braking system configurations may be arranged to apply a braking force to the vehicle wheel 20, such as drum brake configurations. Alternatively, another braking system configuration may include electrically actuated brake caliper devices including an electrically activated brake piston and a linear sensor arranged to monitor the linear displacement, i.e., the stroke length of a plunger of the brake piston. Further, the braking force may originate from an electric machine, such as an electric wheel motor or an electric motor / generator that is an element of an electrified powertrain, wherein the applied braking force is a reaction torque of the electric device that is part of a regenerative braking event.

[0020] In one embodiment, vehicle 10 includes a driver brake pedal 40 disposed within a passenger compartment of vehicle 10 and used by a vehicle operator to generate a braking command. A pedal position sensor 42 is disposed to monitor the operator's input to brake pedal 40. Alternatively or additionally, brake controller 50 may be configured to generate a braking command that may be communicated to master cylinder 32 and / or brake actuator 36 to autonomously control actuation of braking system 30 to effect vehicle braking in response to the sensed conditions. The autonomously commanded braking command may be separate from or in conjunction with the driver-generated braking command.

[0021] The vehicle 10 may be equipped with a spatial monitoring system 54 arranged to monitor the spatial environment surrounding the vehicle 10. The vehicle 10 may be equipped with a global positioning system (GPS) 52 for navigation. The vehicle 10 may be equipped with a telematics device 56 to enable communication with other vehicles. The vehicle 10 may be equipped with a human-machine interface (MMI) device 70 to enable communication with the vehicle driver. Communication between the various controllers may be performed using a communication link 75.

[0022] The braking system 30 is configured to control vehicle braking and includes wheel braking devices, e.g., disc brake elements, brake calipers, master cylinders, and a braking actuator, e.g., a pedal. Wheel speed sensors monitor individual wheel speeds, and the brake controller 50 may be equipped with anti-lock brake control functionality. The brake controller 50 may also coordinate the braking force generated via the wheel brakes and the regenerative braking force generated via the electric motor(s) during a braking event. The braking system 30 further includes numerous other components and subsystems capable of transmitting braking commands and monitoring braking performance, each of which may be subject to wear and deterioration over its useful life.

[0023] The spatial monitoring system 54 may include a controller and one or a plurality of spatial sensors 55, each of which is arranged on the vehicle to monitor a field of view of objects and geographic regions located near the vehicle 10. The spatial monitoring system 54 generates digital representations of each field of view, including neighboring distant objects, based on the data inputs from the spatial sensors. The spatial monitoring system 54 may evaluate the inputs from the spatial sensors 55 to determine a linear range, relative speed, and trajectory of the vehicle 10 with respect to each neighboring distant object. The distant objects may include a predefined location point, such as an intersection, a crosswalk, a stop sign at an intersection, etc.Spatial sensors 55 may be arranged at various locations on the vehicle 10, including the front corners, rear corners, rear sides, and center sides. In one embodiment, spatial sensors 55 may include a front radar sensor and a camera. The arrangement of the noted spatial sensors 55 enables the spatial monitoring system 54 to monitor traffic flow, including nearby vehicles and other objects around the vehicle 10. Data generated by the spatial monitoring system 54 may be used by the pavement marking detection processor (not shown) to estimate the roadway.The spatial sensors 55 may further include object-detecting sensor devices, including range sensors such as FM-CW (Frequency Modulated Continuous Wave) radars and FSK (Frequency Shift Keying) radars and LIDAR (Light Detection and Ranging) devices, and ultrasonic devices that rely on effects such as Doppler effect measurements to locate forward objects. Possible object-detecting devices include charge-coupled devices (CCD) or complementary metal-oxide-semiconductor (CMOS) video image sensors and other known camera / video image processors that utilize digital photographic techniques to 'view' forward objects, including one or more vehicles.Such sensor systems are used to detect and locate objects in automotive applications and can be used with systems including, for example, adaptive cruise control, autonomous braking, autonomous steering, and side object detection.

[0024] The spatial monitoring system 54 can be further configured to monitor the driving dynamics conditions and the spatial environment in the vicinity of the vehicle 10. This includes monitoring and characterizing the spatial environment in the vicinity of the vehicle 10, which is provided to the autonomous controller 60 to ensure a degree of driving automation. Data and signal inputs include spatial environment data in the form of inputs from the spatial sensor(s) 55 and map data in the form of a detailed 3D map of the environment and position data from the GPS 52. The data inputs further include driving dynamics data in the form of data collected by in-vehicle sensors, such as gyros and wheel speed sensors, as well as information transmitted from other vehicles, e.g., V2V data, and information transmitted from the infrastructure, e.g., V2X data.The data collected by the spatial sensor(s) 55 is used in localization, object detection, and classification algorithms to estimate the position of the current road, the current lane, the type and position of objects and obstacles, including static and dynamic obstacles and objects, and to estimate the movement and behavior of surrounding moving obstacles on the road and in the lane. The spatial monitoring system 54 monitors and estimates the vehicle position and dynamic states as described herein. The vehicle position states include geographically defined x and y states (e.g., latitude and longitude) and an angular direction. The vehicle dynamic states include yaw, lateral, and longitudinal acceleration states.

[0025] The spatial sensors 55 associated with the spatial monitoring system 54 are preferably positioned within the vehicle 10 in a relatively unobstructed position to monitor the spatial environment. As applied herein, the spatial environment includes external elements, including fixed objects such as signs, poles, trees, houses, businesses, bridges, etc., and moving or mobile objects such as pedestrians and other vehicles. Each of these spatial sensors 55 provides an estimate of the actual position or condition of an object, where the estimate includes an estimated position and standard deviation. As such, the sensory detection and measurement of object locations and conditions are commonly referred to as 'estimates'. It will be further recognized that the characteristics of these spatial sensors 55 are complementary, such that some are more reliable than others in estimating certain parameters.Spatial sensors 55 may each have different operating ranges and angular coverages, which can estimate various parameters within their operating ranges. For example, radar sensors can be used to estimate the range, range rate, and azimuth position of an object. A camera with a vision processor may be more accurate at estimating an object's shape and azimuth position, but less efficient at estimating the range and range rate of an object. Scanning lidar sensors can be used to estimate range and azimuth position. Ultrasonic sensors can be used for range estimation. Furthermore, it is recognized that the performance of each sensor is affected by different environmental conditions. Thus, some of the spatial sensors 55 present parametric variances during operation, although overlapping sensor detection ranges create opportunities for sensor data fusion.

[0026] The autonomous controller 60 is configured to effect autonomous vehicle operation. Autonomous vehicle functionality may include an on-board control system capable of providing a degree of driving automation. The terms 'driver' and 'operator' describe the person responsible for controlling the operation of the vehicle 10, whether actively participating in controlling one or more vehicle functions or in controlling the autonomous operation of the vehicle. Driving automation may include a range of dynamic driving and vehicle functions. Driving automation may include some degree of automatic control or intervention related to a single vehicle function, such as steering, acceleration, or braking, respectively, with the driver constantly assuming overall control of the vehicle 10.Driving automation may include some degree of automatic control or intervention related to the simultaneous control of multiple vehicle functions, such as steering, acceleration, and / or braking, with the driver maintaining overall control of the vehicle 10 at all times. Driving automation may include the simultaneous automatic control of all driving functions of the vehicle, including steering, acceleration, and braking, with the driver relinquishing control of the vehicle for a certain period of time during a trip. Driving automation may include the simultaneous automatic control of driving functions of the vehicle, including steering, acceleration, and braking, with the driver maintaining overall control of the vehicle 10 throughout the trip.Driving automation includes hardware and controllers configured to monitor the spatial environment under various driving modes to perform various driving tasks during vehicle dynamics. Driving automation may include, as non-limiting examples, cruise control, adaptive cruise control, lane change warning, intervention and control, automatic parking, acceleration, braking, and the like. Autonomous vehicle functions include, as non-limiting examples, automatic cruise control (ADR), lane guidance and lane keeping operations, lane change operations, steering assistance operations, object avoidance operations, parking assistance operations, vehicle braking operations, vehicle speed and acceleration operations, vehicle lateral movement operations, e.g., as part of lane guidance, lane keeping, and lane change operations, etc.Thus, the braking command may be generated by the autonomous controller 60 independently of any action by the vehicle operator and in response to an autonomous control function.

[0027] The controls may be integrated into the passenger compartment of the vehicle 10 and may include, as non-limiting examples, a steering wheel, an accelerator pedal, a brake pedal 40, and an operator input device that is an element of the HMI device 70. The controls enable the vehicle operator to interact with and directly operate the passenger vehicle 10. The operator control device includes the steering wheel, the accelerator pedal, the brake pedal 40, the gear selector, and the like, and may be omitted in some embodiments of the vehicle 10.

[0028] The MMS device 70 enables human / machine interaction to control the operation of an infotainment system, a GPS 52, a navigation system, and the like, and includes a controller. The MMS device 70 monitors operator requests and provides information to the operator, including the status of the vehicle systems and service and maintenance information. The MMS device 70 communicates with and / or controls the operation of the plurality of user interface devices, wherein the user interface devices are capable of sending a message in connection with one of the autonomous vehicle control systems. The MMS device 70 may also communicate with one or more devices that monitor biometric data associated with the vehicle operator, including, for example, gaze direction, posture, and head position detection, among others.The HMI device 70 is a unitary device for ease of description, but may be configured as multiple control modules and corresponding sensor devices in one embodiment of the system described herein. User interface devices may include devices capable of sending a reminder message prompting operator action and may include an electronic display module, e.g., a liquid crystal display (LCD) device, a heads-up display (HUD) (not shown), an audio feedback device, a wearable device, and a haptic seat. User interface devices capable of prompting operator intervention are preferably controlled by or via the HMI device 70.The HUD can project information that is reflected onto an interior surface of a vehicle windshield within the driver's field of view, including conveying a confidence level associated with the operation of an autonomous vehicle control system. The HUD can also provide augmented reality information, such as lane location, vehicle path, heading and / or tracking information, and the like.

[0029] In one embodiment, vehicle 10 may be configured to communicate with an additional vehicle communications network 85 via telematics device 56, which includes communication between a controller associated with a smart highway system and vehicle 10. A smart highway system may be configured to monitor the positions, speeds, and trajectories of a plurality of vehicles, using such information to enable control of one or more similarly positioned vehicles. This may include communicating the geographic location, front-end speed, and acceleration rate of one or more vehicles relative to vehicle 10.In one embodiment, the vehicle 10 is configured to communicate with an off-board controller 80, for example, in a remote maintenance center employing an external administrator, via the communication network 85.

[0030] The term "controller" and related terms such as control module, module, controller, control unit, processor, and similar terms refer to one or various combinations of application-specific integrated circuits (ASICs), electronic circuit(s), central processing unit(s), e.g., microprocessor(s), and associated non-transitory storage component(s) in the form of memory and storage devices (read-only memory, programmable read-only memory, random access memory, hard disk, etc.). The non-transitory storage component is capable of storing machine-readable instructions in the form of one or more software or firmware programs or routines, combinational logic circuit(s), input / output circuit(s) and devices, signal conditioning and buffer circuit(s), and other components accessible by one or more processors to provide a described functionality.Input / output circuitry and devices include analog-to-digital converters and related devices that monitor sensor inputs at a predetermined polling frequency or in response to a trigger event. Software, firmware, programs, instructions, control routines, code, algorithms, and similar terms refer to sets of instructions executable by a control unit, such as calibrations and look-up tables. Each controller executes one or more control routines to provide desired functions. The routines may be executed at regular intervals, such as every 100 microseconds during operation. Alternatively, routines may be executed in response to a trigger event. The term 'model' refers to processor-based or processor-executable code and associated calibration that simulates the physical existence of a device or physical process.The term "dynamic" describes steps or processes that are performed in real time and are characterized by monitoring or otherwise determining parameter states and regularly or periodically updating parameter states while executing a routine or between iterations of program execution. The terms "calibration," "calibrating," and related terms refer to a result or procedure that compares an actual or standard measurement associated with a device with a sensed or observed measurement or a commanded position. A calibration described herein may be reduced to a storable parametric table, multiple executable equations, or other suitable form.

[0031] Communication between the controllers and communication between controllers and actuators and / or sensors may occur via the communication link 75, which may be a direct wired point-to-point connection, a networked communication bus connection, a wireless connection, or other communication link. Communication involves the exchange of data signals, including, for example, the exchange of electrical signals over a conductive medium, electromagnetic signals through the air, optical signals over fiber optics, and the like. Data signals may include discrete, analog, or digitized analog signals representing inputs from sensors and actuator commands, as well as communication signals between control units. The term "signal" refers to a physically perceivable indication that conveys information and may be a suitable waveform (e.g.,Electrical, optical, magnetic, mechanical, or electromagnetic, such as direct current, alternating current, sine waves, triangular waves, square waves, vibration, and the like, that can pass through a medium. A parameter is defined as a measurable quantity that represents a physical property of a device or other element that is detectable by one or more sensors and / or a physical model. A parameter may have a discrete value, e.g., "1" or "0," or may be continuously adjustable.

[0032] Telematics device 56 includes a wireless telematics communication system enabling external vehicle communication, including communication with communication network 85 having wireless and wired communication capabilities. Telematics device 56 is capable of additional vehicle communication, including short-range vehicle-to-vehicle (V2V) communication. Alternatively or additionally, telematics device 56 includes a wireless telematics communication system capable of short-range wireless communication with a portable device, such as a cellular phone, a satellite phone, or other telephony device.In one embodiment, the handheld device is provided with a software application including a wireless protocol for communicating with the telematics device 56, and the handheld device performs the additional vehicle communication, including communication with the external administrator via the off-board controller 80 over the communication network 85. Alternatively or additionally, the telematics device 56 performs the additional vehicle communication directly by communicating with the external controller over a communication network.

[0033] Different components, subsystems, and systems may exhibit different rates of deterioration over the useful life of a vehicle and may be managed and controlled to induce fewer stresses under certain conditions in order to extend their useful life and / or maintain an acceptable level of performance. Brake elements, such as brake pads, are serviceable parts that wear with use and require periodic replacement to maintain braking performance. Proactive and early detection of brake wear and performance degradation can be provided to the driver and autonomous control programs. In autonomous braking control systems, the magnitude of the applied braking force can be determined based on a relative speed and a relative distance to a target, which may be an intersection point in one embodiment.

[0034] Fig.Figure 2 schematically illustrates an information flow diagram associated with a brake monitoring routine 200 that may advantageously be implemented in a controller of an embodiment of the vehicle 10 described with reference to Fig.1. The brake monitoring routine 200 may be implemented as one or more control routines. Overall, the brake monitoring routine 200 includes detecting the occurrence of a braking event and monitoring the applied braking force during the braking event. Monitoring the applied braking force may be achieved via the pressure sensor 38, which in one embodiment is arranged to monitor the hydraulic pressure and associated applied brake pressure in the master cylinder 32 during the braking event. A total stopping distance and a stop time of the vehicle 10 during the braking event are also monitored. The stop time is measured from a starting point occurring at the time of the braking event and an ending point occurring at the time the vehicle 10 comes to a stop. The applied brake pressure is integrated over the course of the stop time.The braking system is evaluated based on the total stopping distance and the integrated applied braking force during the braking event. Based on the evaluation of the total stopping distance and the integrated braking force during the braking event, maintenance requirements for the braking system can be determined. The vehicle's stopping distance can vary depending on brake wear. The brake monitoring routine 200 compares the stopping distance and the braking time to the stopping value with a calibrated stopping distance and the braking time to the stopping value in conjunction with the comparison of the braking force to a calibrated braking force, using the existing braking hardware and without adding sensors or other devices specifically configured to detect brake wear.

[0035] For a method not belonging to the invention, Table 1 provides a breakdown, with the numerically labeled blocks and corresponding functions listed as follows, corresponding to the brake monitoring routine 200. The teachings herein may be described in terms of the functional or logical block components, or various processing steps. It should be noted that such block components may be constructed from hardware, software, and / or firmware components configured to perform the specified functions. Table 1 BLOCK BLOCK CONTENT 201 Vehicle calibration 202 Is the vehicle in operation? 204 Is the vehicle in propulsion and is the vehicle speed higher than a minimum threshold? 206 Is braking instructed? 208 Is there a predefined location point assigned to an attack? 210 Collecting information related to the calibration stop event, including initial vehicle speed, cumulative braking force (e.g. pressure), stopping distance 212 Calibration of the vehicle's internal map, stopping distance 220 Vehicle operation 222 Is the vehicle in operation? 224 Detecting the vehicle location; Is the location on the map = calibrated map? 226 Detect and monitor the stop event (stopping distance, applied brake pressure, distance); Is the stop = a calibrated stop? 228 Comparing the stopping distance, the accumulated brake pressure for the distance 230 Is the difference greater than a threshold? 232 Incrementing the event counter 234 Frequency of events exceeding the maximum threshold? 236 Notification of the operator 238 Updating the calibrated time to stop 240 Running the diagnostic / prediction routine 242 Running the fault isolation routine 244 Performing SOH monitoring of the braking system

[0036] The brake monitoring routine 200 includes a vehicle calibration subroutine 201 and a vehicle operation subroutine 220. A braking event is any event during vehicle operation in which vehicle braking is commanded either by an operator or by an autonomous control system. A stopping event is a braking event that results in the vehicle 10 reaching a stopping condition, i.e., reaching a zero speed. The designation of (1) indicates that the described condition is TRUE or reached, and the designation (0) indicates that the described condition is FALSE or not reached.The vehicle calibration subroutine 201 includes verifying that the vehicle is operating (202)(1), verifying that the vehicle is traveling in a forward gear and that the vehicle speed is greater than a minimum threshold speed (204)(1), verifying the presence of a braking command (206)(1), and verifying the presence of a predefined location point, such as a stop sign, a pedestrian signal, an intersection signal, or other associated stopping event (208)(1). If all of the aforementioned conditions are met, the data associated with the calibration stop event is captured in a vehicle-mounted storage device and stored in a database (210), including an initial vehicle speed, a cumulative braking force, e.g., pressure, a time to stop, and a stopping distance.Preferably, the stopping distance is determined using information from the spatial sensors 55 of the spatial monitoring system 54, e.g., the lidar sensors, which estimate the linear range and azimuth position. The location of the vehicle 10, as indicated by the GPS 52, may also be acquired, and a desired stopping distance may be linked to a vehicle map for the GPS location (212). The result of the vehicle calibration subroutine 201 may be in the form of a lookup table stored in a memory array in the controller and including, for the position indicated in the vehicle map, a braking force required to achieve a stopping distance and / or a stopping time related to an initial vehicle speed. This information is acquired in a vehicle-side controller or, alternatively, in a vehicle-side controller for referencing during subsequent stopping events.The vehicle calibration subroutine 201 described herein is one embodiment of a method for calibrating an embodiment of the vehicle 10 to determine a vehicle-specific empirical relationship between vehicle speed, cumulative applied braking force, stopping time, and stopping distance. As described with respect to the drive operation subroutine 220, additional vehicle data in the form of initial vehicle speeds, cumulative braking forces, e.g., pressure, stopping and stopping distance times, may be collected and incorporated into the database to cover braking events across a wide range of braking situations, weather conditions, and braking temperatures. These additional items may also be incorporated into the database, including the use of normalization models that account for these factors in determining the relationship between vehicle speed, cumulative applied braking force, stopping time, and stopping distance.

[0037] The operation of the vehicle operation subroutine 220 is performed as follows. If the vehicle is operating (222)(1), the GPS 52 checks whether the vehicle 10 is operating at a location that has been calibrated (224)(1) and determines whether the vehicle 10 is executing a stop event, including a stop event with conditions related to one of the calibrated stop events of the vehicle calibration subroutine 201 (226)(1). This involves collecting data associated with the current stop event, including an initial vehicle speed, cumulative brake pressure, stop time, and stopping distance. The collected data associated with the current stop event is compared with calibration data for the stop event (228) and passed to a diagnostic / prediction routine (240) for evaluation.

[0038] The diagnostic / prediction routine (240) includes a state of health (SOH) monitoring step 242 and a fault isolation step 244. The terms "prediction," "prediction," and related terms are associated with data monitoring and with algorithms and evaluations that make a predictive statement about a likely future event associated with a component, subsystem, or system, such as the braking system 30 of the vehicle 10.Predictions may include classifications that include a first state indicating that the component, subsystem, or system is operating according to its specification ("Green" or "G"), a second state indicating a change or deterioration in the operation of the component, subsystem, or system ("Yellow" or "Y"), and a third state indicating a fault in the operation of the component, subsystem, or system ("Red" or "R"), requiring immediate operator attention. The terms "diagnostics," "diagnostics," and related terms are associated with data monitoring and algorithms and evaluations that provide an indication of the presence or absence of a specific fault in a component, subsystem, or system.The term “mitigation” and related terms are associated with operations, actions, or control routines designed to reduce the effects of a failure in a component, subsystem, or system.

[0039] The SOH monitoring step 242 includes determining the SOH of the braking system 30, wherein the SOH is determined based on evaluating and correlating data associated with the stopping events, including the initial vehicle speed, cumulative brake pressure, time to stop, and stopping distance. The green status may be associated with a stopping distance and / or a stopping time that is less than a first initial vehicle speed threshold, and the yellow status may be associated with a stopping distance and / or a stopping time that is greater than the first initial vehicle speed threshold and less than a second initial vehicle speed threshold. The red status may be associated with a stopping distance and / or a stopping time that is greater than the second initial vehicle speed threshold.The brake monitoring routine 200 can send a message to the vehicle operator via the MMS device 70 or an external administrator to initiate brake service when the SOH of the braking system 30 is yellow and the vehicle 10 is configured as an autonomous vehicle. The brake monitoring routine 200 is capable of initiating an intervention, such as limited operation or vehicle shutdown, when the SOH value of the braking system 30 is red.

[0040] The fault isolation step 244 includes evaluation steps for isolating a fault at an element in the braking system 30 based on the data associated with the stopping events, including the initial vehicle speed, cumulative brake pressure, stop time, and stopping distance. In one embodiment, a fault may be isolated to a worn brake pad if the stopping distance is greater than a first stopping distance threshold associated with an initial vehicle speed. In one embodiment, a fault may be isolated to a stuck brake caliper if the stopping distance is less than a second stopping distance threshold associated with an initial vehicle speed.Additional fault isolation routines may be developed and implemented to isolate faults in other components or subsystems of the braking system 30 with the data associated with the stopping events, including the initial speed of the vehicle, the cumulative brake pressure, the stop time, and the stopping distance.

[0041] A difference between the stopping distance for the braking event and one of the calibrated braking events of the vehicle calibration subroutine 201 is calculated and an absolute value for the difference is compared to a threshold value (230).

[0042] If the absolute value for the difference in stopping distances is less than the threshold (230)(0), this iteration ends and the routine 200 returns to step 224 to wait for an indication from the GPS 52 that the vehicle 10 is operating at a calibrated location and the process steps are repeated.

[0043] If the absolute value for the difference in stopping distances is greater than the threshold (230)(1), an event counter is incremented (232) and the event counter is compared to a maximum threshold (234). If the maximum threshold is exceeded (234)(1), the result is communicated to the vehicle operator or administrator (236), and a value for the calibrated stop time associated with the stop event is updated (238). The updated stop time for the stop event is provided as an input to update the data associated with the calibration stop event, as acquired in step 210.

[0044] A method for evaluating wear or system degradation of the braking system 30 includes determining an average deceleration rate based on the total stopping distance and total stopping time, and evaluating the braking system 30 based on a relationship between the integrated applied braking force and the average deceleration rate. A reduction in the average deceleration rate for a known value of the integrated applied braking force may indicate increased wear or a reduction in the SOH.

[0045] In this way, monitoring initial vehicle speed, cumulative brake pressure, holding time, and stopping distance, as well as comparing them with previously acquired data, can be used to monitor braking performance and detect brake wear. Other factors, such as weather and environmental conditions, road conditions, etc., can hinder or otherwise influence the results. Furthermore, the generation of electrical energy as a result of regenerative braking can be monitored and thus checked for the magnitude of the braking force. Thus, the system can advantageously use historical data to detect deterioration in braking performance and then modify the system inputs in response to maintain braking performance.If braking performance drops below a threshold, the vehicle operator and / or the autonomous controller 60 are notified that maintenance and service is required, including a portion of the braking system that may require service. The autonomous controller 60 may communicate the SOH of the braking system 30 to the external administrator via the telematics device 56.

Claims

[1] A method for monitoring a braking system (30) for a vehicle (10), the method comprising: Detecting a braking event; Determining an applied braking force during the braking event; and Monitoring a total stopping distance during the braking event and a stopping time via a sensor (55); characterized by Integrating the applied braking force during the braking event; Evaluating the braking system (30) via a controller (60) based on the total stopping distance, the stopping time and the integrated applied braking force during the braking event; Determining an error associated with the braking system (30) based on the evaluation of the braking system (30); and Communicating the error associated with the braking system (30) via the controller (60). [2] The method of claim 1, further comprising: Determining a state of health (SOH) for the braking system (30) based on evaluating the total stopping distance, the stopping time and the integrated applied braking force during the braking event; and Communicating the SOH for the braking system (30) to a vehicle driver via a human-machine interface device when the SOH is less than a threshold SOH. [3] The method of claim 1, further comprising: Determining a state of health (SOH) for the braking system (30) based on evaluating the total stopping distance, the stopping time and the integrated applied braking force during the braking event; and Communicating the SOH for the braking system (30) to an off-board controller (80) via a telematics device (56) when the SOH is less than a threshold SOH. [4] The method of claim 1, further comprising determining a setting of the applied braking force during a subsequent braking event based on the total stopping distance and the integrated applied braking force during the braking event. [5] The method of claim 1, further comprising: Determining an initial vehicle speed at the start of the braking event; and Evaluating the braking system (30) via the controller (60) based on the initial vehicle speed, the total stopping distance and the integrated applied braking force during the braking event. [6] The method of claim 1, wherein the vehicle-side sensor (55) monitoring the total stopping distance during the braking event comprises a lidar device. [7] The method of claim 1, wherein determining the applied braking force during the braking event comprises monitoring the hydraulic brake pressure in a master cylinder of the braking system (30) via a pressure sensor. [8] The method of claim 1, further comprising communicating the need to service the braking system (30) to an external controller (60) via a telematics device based on the fault associated with the braking system (30). [9] The method of claim 1, wherein evaluating the braking system (30) based on the total stopping distance, the stopping time, and the integrated applied braking force during the braking event comprises: Determining an initial vehicle speed at the start of the braking event; Determining an average deceleration rate based on the initial vehicle speed, the total stopping distance, and the stopping time; and Evaluating the braking system (30) based on a relationship between the integrated applied braking force and the average deceleration rate.

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