Patent Publication Number: US-2022221016-A1

Title: Wireless vehicle area network having connected brake sensors

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage of International Application No. PCT/US2020/029296, filed Apr. 22, 2020, which claims priority to and the benefit of: U.S. Provisional Patent Application No. 62/849,347, filed on May 17, 2019; U.S. Provisional Patent Application No. 62/849,344, filed on May 17, 2019; U.S. Provisional Patent Application No. 62/849,343, filed on May 17, 2019; U.S. Provisional Patent Application No. 62/849,339, filed on May 17, 2019; U.S. Provisional Patent Application No. 62/944,981, filed on Dec. 6, 2019; U.S. Provisional Patent Application No. 62/951,561, filed on Dec. 20, 2019; U.S. Provisional Patent Application No. 62/951,734, filed on Dec. 20, 2019; U.S. Provisional Patent Application No. 62/951,594, filed on Dec. 20, 2019; and U.S. Provisional Patent Application No. 62/951,660, filed on Dec. 20, 2019, the contents of each of which are incorporated herein by reference as though fully set forth herein. 
    
    
     FIELD OF THE TECHNOLOGY 
     The subject technology relates to wireless networks, and particularly to brake sensors connected to a vehicle area network. 
     BACKGROUND OF TECHNOLOGY 
     In the United States, the Dwight D. Eisenhower National System of Interstate and Defense Highways, commonly known as the Interstate Highway System, is a network of controlled-access highways that forms part of the National Highway System in the United States. Construction of the Interstate Highway System was authorized by the Federal Aid Highway Act of 1956. The Interstate Highway System extends throughout the contiguous United States and has routes in Hawaii, Alaska, and Puerto Rico. 
     With great roads, trucking is an essential component of the economy infrastructure. Indeed, a tractor-trailer vehicle cruising down the Interstate Highway is common. Trucking is involved in the delivery of not only almost every consumer product but industrial products as well. Truck drivers are often independent drivers who may or may not own their own trailer but, in any case, contract to deliver one or more full-load or part-load trailers. Indeed, being a truck driver is one of the most common jobs in America. 
     A paradigm shift is on the horizon as the asphalt highway is integrated into the information age. Such vehicles will be equipped with a suite of technology to connect to the information superhighway and image the physical superhighway. The vehicles will form a virtual image of the road that is processed for navigation and control. The technology will include cameras, LIDAR, RADAR, sensors of all sorts, motors and of course a large processing capacity (e.g., processors, memory, power supplies etc.). 
     Problems with transport by tractor-trailer vehicle remain despite the longstanding and ubiquitous use. Mobile vehicles have been slow to beneficially utilize the potential benefits of interconnection and analysis. Other obstacles stem from the typical driver not being comfortable navigating use of sophisticated electronics or various configurations that are simply not interoperable. Further, without drivers, many more tasks and maintenance activities must be automated. Thus, a need exists for easy, automatic connection and operation of vehicles with more sophisticated communication and networking technology on vehicles, particularly tractor-trailer vehicles. 
     Various types of sensors have been employed on vehicles, and particularly on tractor-trailer trucks. Normally these sensors are placed on the tractor-trailer truck and manually calibrated to trigger a generic alert (e.g. a tire pressure alert) when a certain measurement is returned. This requires the sensors to be initially tested and calibrated on the vehicle. The utility of each sensor is limited to selectively triggering the alert, and no data from the sensors is gathered or processed for analysis. 
     Further, challenges arise with adequately placing sensors within an existing vehicle system, such as a braking system. It is difficult to place a sensor, or multiple sensors, within an existing braking system without potentially impacting the integrity of the braking system. Further, assemblies for indicating brakewear are typically integrated into consumable components like the pads themselves. Thus, when the pads are changed, the sensor assembly is also replaced. 
     SUMMARY OF THE TECHNOLOGY 
     In light of the needs described above, in at least one aspect, the subject technology relates to a number of brake sensors connected directly to the braking components of a vehicle and reporting data to a wireless hub over a wireless vehicle area network. Further, the sensor assemblies are separate from the consumable components so that use is uninterrupted by routine repair and maintenance. 
     In at least one aspect, the subject technology includes system for measuring brake data from a braking assembly of a vehicle, the braking assembly including at least one caliper with a fixed portion and a floating portion. The system includes a plurality of brake sensors. Each brake sensor is attached to one of the calipers and includes a sensing element attached to the fixed portion and a target portion attached to the floating portion. The brake sensor is configured to measure brake data including a position of the target portion with respect to the sensing element indicative of brake pad thickness. The brake sensor is also configured to transmit brake data over a wireless vehicle area network. The system also includes a wireless hub which includes a transceiver configured to transmit and receive data over the wireless vehicle area network. The wireless hub is configured to receive brake data from the plurality of brake sensors, process the brake data, and generate and transmit an alert when brake data from one of the plurality of brake sensors indicates a potential fault condition. 
     In some embodiments, the target portion is a magnet that generates a magnetic field and the sensing element is an anisotropic magnet resistivity sensor configured to sense the magnetic field of the magnet to generate a signal. 
     In at least one aspect, the subject technology relates to a system for measuring brake data from a braking assembly of a vehicle. The braking assembly includes a caliper with a fixed portion and a floating portion. The caliper further includes a mounting plate configured to attach the caliper to an axle of the vehicle. The system includes a brake sensor mounted to the caliper on an interior side of the mounting plate such that the brake sensor is positioned within an interior of the caliper. The brake sensor includes a sense element attached to the fixed portion and a target portion attached to the floating portion. The brake sensor is configured to measure brake data including a position of the fixed portion with respect to the floating portion and transmit the brake data over a wireless vehicle area network. 
     In some embodiments, the system includes a wireless hub having a transceiver configured to transmit and receive data over the wireless vehicle area network. The wireless hub is configured to receive brake data from the plurality of brake sensors, process the brake data, and generate and transmit an alert when brake data from one of the plurality of the brake sensors indicates a potential fault condition. 
     In some embodiments, the braking system further comprises at least one temperature sensor. In such a case, the wireless hub can be further configured to detect an anomaly in a temperature measured by the at least one temperature sensor during a time period. After detecting an anomaly, the wireless hub can compare the temperature measured by the at least one temperature sensor during the time period to temperature data from at least one wheel end temperature sensor. The wireless hub can then generate and transmit an alert when the comparison is indicative of a fault condition. 
     In at least one aspect, the subject technology relates to a system for measuring brake data from a drum brake assembly of a vehicle, the drum brake assembly including a brake chamber which actuates a push rod when vehicle brakes are applied, actuation of the push rod causing a rotary motion of an adjuster arm and attached slack adjuster head around a cam shaft. The system includes a brake sensor mounted to the drum brake assembly and configured to measure brake data including a displacement of the drum brake assembly during braking. The brake sensor is configured to transmit brake data over a wireless vehicle area network. 
     In some embodiments, the brake sensor includes a sensing element and a target, the sensing element configured to sense a magnetic field of the target. The sense element can be attached to a fixed brake chamber bracket, the fixed brake chamber bracket remaining at a fixed location with respect to the vehicle when the vehicle brakes are applied. In such a case, the target is attached to the pushrod and configured to move, with respect to the sense element, when the vehicle brakes are applied. 
     In some embodiments, the sense element is attached to a fixed mount plate adjacent the slack adjuster head, the fixed mount plate remaining at a fixed location with respect to the vehicle when the vehicle brakes are applied. In such a case, the target is attached to the slack adjuster head and configured to move, with respect to the sense element, when the vehicle brakes are applied. 
     In some embodiments, the target is attached to a fixed indicator plate adjacent the cam shaft, the fixed indicator plate remaining at a fixed location with respect to the vehicle when the vehicle brakes are applied. In such a case, the sense element is attached to the adjuster arm such that the sense element moves as the adjuster arm and cam shaft rotate when the vehicle brakes are applied. 
     In some embodiments, the drum brake assembly is configured to rotate an s-cam when the brakes are applied such that the s-cam engages two cam followers coupled to opposing brake shoes. In such a case, the displacement of the drum brake assembly measured by the system is representative of a difference in displacement distance between the two cam followers when the brake assembly is in a disengaged state and when the brake assembly is in an engaged state. The system can be further configured to measure an s-cam rotation angle, the difference in displacement distance between the two cam followers being calculated based on the s-cam rotation angle. 
     In some embodiments, the system is configured to determine a current brake pad thickness by calibrating the drum brake assembly at an initial brake pad thickness (t i ) and initial s-cam rotation angle (θ i ). The system determines a slope of a plot of cam follower displacement over s-cam rotation angle (m). The system measures a current s-cam rotation angle (On). Finally, the system calculates the current brake pad thickness by setting the current brake pad thickness as equal to the following: t i −m (θ n −θ i ). In some cases, the system is configured to provide an alert based on an expected brake pad failure thickness. In some cases, the system is configured to provide an indicator of one or more of the following: a distance until drum brake assembly maintenance is recommended; or a distance until drum brake assembly failure is expected. Actual data about particular driver habits and/or expected routes may also be used in the maintenance calculation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those having ordinary skill in the art to which the disclosed system pertains will more readily understand how to make and use the same, reference may be had to the following drawings. 
         FIG. 1  is an exemplary tractor-trailer vehicle utilizing a vehicle area network in accordance with the subject technology. 
         FIG. 2A  is an exploded view of a wireless hub in accordance with the subject technology. 
         FIG. 2B  is a block diagram schematic view of a wireless hub in accordance with the subject technology. 
         FIG. 3A  is an exploded view of a range extender in accordance with the subject technology. 
         FIG. 3B  is a block diagram schematic view of a range extender in accordance with the subject technology. 
         FIG. 4A  is a perspective view of a beacon in accordance with the subject technology. 
         FIG. 4B  an exploded view of a beacon in accordance with the subject technology. 
         FIG. 5  is another exemplary tractor-trailer vehicle utilizing a vehicle area network in accordance with the subject technology. 
         FIG. 6A  is a portion of a flowchart for automatically ordering the trailers of the vehicle of  FIG. 5  in accordance with the subject technology 
         FIG. 6B  is a portion of a flowchart for automatically ordering the trailers of the vehicle of  FIG. 5  in accordance with the subject technology. 
         FIG. 6C  is a portion of a flowchart for automatically ordering the trailers of the vehicle of  FIG. 5  in accordance with the subject technology 
         FIG. 6D  is a portion of a flowchart for automatically ordering the trailers of the vehicle of  FIG. 5  in accordance with the subject technology. 
         FIG. 7A  is a perspective view of a sensor arrangement in accordance with the subject technology. 
         FIG. 7B  is two side-by-side overhead views of the sensor arrangement of  FIG. 7A  in an initial installation orientation and an after full brake wear orientation to illustrate how the target portion moves. 
         FIG. 8A  is a perspective view of an axle with a brake system having a brake sensor assembly in accordance with the subject technology. 
         FIG. 8B  is a detailed perspective view of a brake system having a brake sensor assembly in accordance with the subject technology. 
         FIG. 8C  is an isolated view of a brake sensor assembly in accordance with the subject technology. 
         FIG. 9A  is a perspective view of an axle with a brake system having a brake sensor assembly in accordance with the subject technology. 
         FIG. 9B  is a detailed perspective view of a brake system having a brake sensor assembly in accordance with the subject technology. 
         FIG. 9C  is an isolated view of the brake sensor assembly of  FIG. 9B . 
         FIG. 10A  is a perspective semi-exploded view of a disc brake system in accordance with the subject technology. 
         FIG. 10B  is a different perspective semi-exploded view of a disc brake system in accordance with the subject technology. 
         FIG. 10C  is a detailed perspective view of a brake system having a brake sensor assembly in accordance with the subject technology. 
         FIG. 10D  is a model view of a deployed brake sensor assembly in accordance with the subject technology. 
         FIG. 10E  is a partial view of a deployed brake sensor assembly in accordance with the subject technology. 
         FIG. 11  is a perspective view of an axle with a drum brake system on each end in accordance with the subject technology. 
         FIG. 12  is an isolated perspective view of a drum brake system in accordance with the subject technology. 
         FIG. 13  is an isolated view of a brake sensor assembly in accordance with the subject technology. 
         FIG. 14  is an end view of a drum brake system in accordance with the subject technology. 
         FIG. 15  is an isolated perspective view of a sensor assembly for the drum brake system of  FIG. 14 . 
         FIG. 16  is an end view of a drum brake system in accordance with the subject technology. 
         FIG. 17  is an isolated perspective view of a sensor assembly for the drum brake system of  FIG. 16 . 
         FIG. 18  is an end view of a drum brake system in accordance with the subject technology. 
         FIG. 19  is an isolated perspective view of a sensor assembly for the drum brake system of  FIG. 18 . 
         FIG. 20A  is a perspective view of a drum brake system in accordance with the subject technology. 
         FIG. 20B  illustrates two end views of a drum brake system with the brakes in disengaged and engaged states for comparison in accordance with the subject technology. 
         FIGS. 20C-E  are schematic views of exemplary positioning of an s-cam and cam followers for the drum brake system of  FIG. 20A  in various positions of brake shoe life from new to end of life. 
         FIG. 20F  is a graph mapping cam follower displacement at various s-cam rotations for the drum brake system of  FIG. 20A . 
         FIG. 20G  is a graph plotting cam follower displacement at various s-cam rotations for the drum brake system of  FIG. 20A . 
         FIG. 21  is a schematic view of a vehicle having a vehicle area network with integrated brake sensor assemblies in accordance with the subject technology. 
         FIG. 22A  is an exemplary graph of brake pad temperature over driving time for a braking system in accordance with the subject technology. 
         FIG. 22B  is an exemplary graph comparing brake pad temperature and wheel end temperature over driving time for a braking system in accordance with the subject technology. 
     
    
    
     DETAILED DESCRIPTION 
     The subject technology overcomes many of the prior art problems associated with vehicle sensor systems for connecting sensors to vehicle brakes and processing sensor data. The advantages, and other features of the systems and methods disclosed herein, will become more readily apparent to those having ordinary skill in the art from the following detailed description of certain preferred embodiments taken in conjunction with the drawings which set forth representative embodiments of the present invention. Like reference numerals are used herein to denote like parts. Further, words denoting orientation such as “upper”, “lower”, “distal”, and “proximate” are merely used to help describe the location of components with respect to one another. For example, an “upper” surface of a part is merely meant to describe a surface that is separate from the “lower” surface of that same part. No words denoting orientation are used to describe an absolute orientation (i.e. where an “upper” part must always be at a higher elevation). 
     Referring now to  FIG. 1 , an exemplary vehicle  100  is shown utilizing a vehicle area network (VAN)  101  in accordance with the subject technology. The vehicle  100  has a tractor  102  for pulling two trailers  104   a ,  104   b . The tractor  102  may haul just a single trailer or multiple trailers, and as many as five. It is typically the responsibility of the truck driver to not only ensure the safe and proper operation of the vehicle  100  but to also connect and disconnect the trailers  104   a ,  104   b . The tractor  102  also includes a cabin  103  having a dashboard (not explicitly shown) for presenting information related to the trailers  104   a ,  104   b . The tractor  102  has front wheels  105   a , which can be steered to control direction of the tractor  102 . The tractor  102  also has rear wheels  105   b . A dolly  106  facilitates mechanical connection of the first and second trailers  104   a ,  104   b . The trailers  104   a ,  104   b  and dolly  106  also include wheels  107 . 
     The trailers  104   a ,  104   b  and dolly  106  are equipped with a plurality of sensors for monitoring position, speed, temperature, pressure, weight and the like for various purposes. In  FIG. 1 , the components of the VAN  101  such as sensors  110   a - c  are shown schematically to illustrate possible locations and configurations. The driver is provided with a pairing device  275  for making wireless connections between the VAN  101  and the sensors  110 . The pairing device  275  also can monitor the status of the trailers  104   a ,  104   b  as well as connect to the devices of the VAN  101 . The pairing device  275  may be a tablet, smart phone, or specialized controller and the like. 
     The VAN  101  establishes communication between numerous components of the vehicle  100 . Individual components can be connected wirelessly, wired and combinations thereof. The connections may utilize various communication protocols, as will be discussed in more detail herein. The VAN  101  can utilize WiFi to establish a high bandwidth backbone, in effect a first level of the VAN  101 . The VAN  101  may include any number of sub-networks, in effect second levels of the VAN  101 . For example as shown in  FIG. 1 , the VAN  101  includes a tractor subnetwork  112  and a trailer subnetwork  114 . Each subnetwork  112 ,  114  includes one or more wireless hubs  130   a - d . The first trailer  104   a  includes the wireless hub  130   b , the dolly  106  includes the wireless hub  130   c  and the second trailer  104   b  includes wireless hub  130   d . As the tractor  102 , trailers  104   a ,  104  and dolly  106  are often reconfigured with other trailers and dollies, quick and easy pairing to establish the subsequent vehicle area network is beneficial. 
     The VAN  101  also includes a first telematics module  116   a  on the tractor  102  and in communication the tractor hub  130   a  as well as a second telematics module  116   b  on the first trailer  104  and in communication with the first trailer hub  130   b . The telematics modules  116   a ,  116   b  also communicate with external networks  118  having external devices  120 . The telematics modules  116   a ,  116   b  communicate with the external networks  118  via cell towers  122 . Preferably, the tractor  102  has a chassis CAN bus  124  over which the tractor hub  130   a  and the telematics module  116   a  communicate. The trailers  104   a ,  104   b  may be substantially identical or quite differently configured not just in terms of hardware but software. However, the VAN  101  can automatically integrate components so that the driver is needed for little pairing activity with the smart device  275  if any at all. Telematics modules and services are available commercially from numerous suppliers, such as CalAmp of Irvine, Calif. 
     The wireless hubs  130   a - d  are powered by a wired power line communication (PLC) cable, typically connected by the driver when mechanically coupling the trailer  104   a ,  104   b  to the tractor  102 . The wireless hubs  130   a - d  communicate using WiFi with a 802.15.4 thread network protocol and/or over the CAN bus  124 . The wireless hubs  130   a - d  can also communicate by common lower power friendly means such as Bluetooth or 433 Mhz technology. The wireless hubs  130   a - d  can also use near-field communication as well as with any other wireless communication protocol now known or later developed. 
     The hubs  130   a - d  can be connected to one or more components or each other using a wired connection. For example, the tractor hub  130   a  can be connected to the front trailer hub  130   b  with a wired cable connection. The wired cable connection can optionally provide power from the tractor hub  130   a  to the trailer hub  130   b  while simultaneously allowing communication through PLC techniques. The wired connection can allow the tractor hub  130   a  and the first trailer hub  130   b  to automatically pair upon making the physical connection. During pairing, the hubs  130   a ,  130   b  communicatively connect utilizing the PLC connection to share credentials of the VAN  101  in accordance with out of band pairing techniques. Similarly, the hubs  130   c ,  13   d  can also be hard wired and automatically integrated into the VAN  101 . 
     Each wireless hub  130   a - d  acts as central communication or access point for devices within the respective local area or subnetwork  112 ,  114  of the vehicle  100 . To that end, the tractor wireless hub  130   a  creates the tractor subnetwork  112  for all devices in and around the tractor  102  of the vehicle  100 . Similarly, the first trailer hub  130   b  creates the trailer subnetwork  114  for all devices in and around the first trailer  104   a . Further, a wireless hub  130   c  on the dolly  106  is part of the first trailer subnetwork  114  but could even form another subnetwork. Other subnetworks may also be included, for example, for other additional trailers, dollies, and/or areas of the truck. 
     Still referring to  FIG. 1 , the tractor wireless hub  130   a  establishes communication to the tractor telematics module  116   a , the pairing device  275  and the first trailer wireless hub  130   b  to establish the tractor subnetwork  112 . The tractor hub  130   a  can communicate with the first trailer hub  130   b  by PLC and/or WiFi, with the pairing device  275  by WiFi, and over the CAN bus  124  with the telematics module  116   a . In one embodiment, the tractor hub  130   a  uses Thread networking communication technology based on the IEEE 802.15.4 radio standard for low power consumption and latency. The communication protocol may include AES 128 encryption with a media access control (MAC) layer network key. 
     The tractor  102  also includes a plurality of sensors  110   a . For simplicity in  FIG. 1 , only one sensor  110   a  is shown schematically, but represents any kind of sensor in any location. In order to facilitate communication between the tractor hub  130   a  and the sensor  110   a , the tractor subnetwork  112  can include a range extender transmitter/receiver  170   a  paired with the sensor  110   a . Depending upon the sensor configuration, the sensor  110   a  may also communicate directly with the tractor hub  130   a . The transmitter/receiver  170   a  and sensor  110   a  may utilize Thread networking communication technology among others. 
     For example, communication between the transmitter/receiver  170   a  and sensor  110   a  may be via Bluetooth communication. The transmitter/receiver  170   a  acts as a range extender for the sensor  110   a . However, Bluetooth is susceptible to eavesdropping so that out of band (OOB) pairing is needed. The pairing device  275  is used to accomplish the OOB pairing. The pairing device  275  can use near-field communication (NFC) with the hubs  130   a - d , sensors  110   a - d  and transmitter/receivers  170   a - d.    
     Pairing the components  110   a - d ,  130   a - d ,  170   a - d  can use multiple technologies and techniques in any combination. The example given here is based on the normal commissioning/pairing process for a Thread device. The pairing device  275  can use WiFi or even read a barcode to link to the hub  130   a . Once linked to the hub  130   a , the pairing device  275  can use RFID technology such as an NFC tag to establish the OOB (Out of Band) pairing connection to the transmitter/receiver  170   a  and sensor  110   a . NFC technology is desirable because the pairing device  275  could simply be a smart phone running an application and held in proximity to the transmitter/receiver  170   a  or sensor  110   a . The OOB pairing link can use datagram transport layer security (DTLS), which is a communications protocol that provides security by allowing communication in a way that is designed to prevent eavesdropping, tampering, and message forgery. Additionally, access can be protected by using a pre-shared key (PSK) generated by an algorithm such a J-PAKE. 
     Once the pairing device  275  establishes communication between the hub  130   a , sensor  110   a  and transmitter/receiver  170   a , the tractor subnetwork  112  is established. In a similar manner, the trailer subnetwork  114  can be established. The first trailer hub  130   b  establishes the first trailer subnet  114  that also includes a plurality of sensors  110   b . Again for simplicity, only a single sensor  110   b  is shown schematically representing, for example, a TPMS. A transmitter/receiver  170   b  is paired with the sensor  110   b . The first trailer  104   a  also includes a telematics module  116   b  and beacon  200 , both of which are part of the first trailer subnetwork  114 . The telematics module  116   b  communicates with external networks  118  via a cell tower  122  as well. The beacon  200  may also communicate directly, whether wired or wirelessly, with the tractor hub  130   a.    
     The tractor hub  130   a  is also paired to the trailer hub  130   b  so that the respective subnetworks  112 ,  114  are in secure communication. To pair the hubs  130   a ,  130   b , the OOB pairing link can use a physical connection with ISO 11992, which is a CAN based vehicle bus standard in the heavy-duty truck industry for communication between the tractor and one or more trailers. The pairing of the hubs  130   a ,  130   b  can share a unique data key such as a key generated by AES-128 encryption. 
     The beacon  200  provides a separate means of transmitting information wirelessly. In particular, the beacon  200  can be configured to act as a GPS, transmitting location data for the first trailer, allowing a remote user to locate the trailer. The beacon  200  is particularly useful for tractor drivers who are picking up a trailer from a large lot of many trailers. For example, certain lots tend to store an enormous number of trailers and are not well organized or marked, requiring drivers to search to locate a particular trailer. Typically, the driver is tasked with seeking out the trailer through a particular identifier on the trailer, such as a license plate. This inefficiently requires the driver to look individually at the license plate of each trailer on the lot to determine whether it is the correct trailer. Further, license plates can be difficult to read accurately from a distance, requiring the driver to approach each license plate within a reasonable distance or even get out of the tractor. As such, the beacon  200  improves the manual searching process by providing a GPS signal to the external networks  118  which ultimately is received by telematics module  116   a  in the tractor  102 . Thus, the beacon GPS signal can be used by the driver to quickly and easily locate the trailer  104   a  within the lot. It is envisioned that the dashboard of the tractor  102  may display not only the location of the beacon  200  but assist with directions on how to drive to the beacon  200 . The beacon  200  can also include a clear visual identifier, such as a blinking light of a specified color or a display showing an identifier, to alert the driver when the driver is close to the correct trailer  104   a . The beacon  200  eliminates the need for the driver to carefully search the entire lot and allows the driver to quickly and easily identify and connect to the proper trailer. 
     Still referring to  FIG. 1 , the dolly  106  and second trailer  104   b  also include respective hubs  130   c ,  130   d  that become part of the VAN  101 . The hubs  130   c ,  130   d  similarly communicate with a plurality of sensors  110   c ,  110   d  and any transmitter/receiver  170   c ,  170   d  paired with the sensors  110   c ,  110   d . Depending upon the configuration, the hubs  130   c ,  130   d  may form subnetworks or simply communicate with the first trailer hub  130   b , which relays the information to the tractor hub  130   a . The second trailer  104   b  can include a telematics module, beacon and other hardware as needed. 
     Generally, a transmitter/receiver  170   a - d  is positioned proximate a respective sensor, which may be pressure, temperature, speed, position, or other sensors. The transmitter/receiver  170   a - d  receives measured data from one or more sensors and reports that data to the local hub wirelessly. The transmitter/receiver  170   a - d  may also use the 433 MHz frequency band for communication. In other cases, the sensors  110   a - d  are wired directly to the local hub  130   a - d , or are connected wirelessly directly to the local hub  130   a - d.    
     It is envisioned that the subnetworks  112 ,  114  can be established in advance. In other words, for the trailer subnetwork, pairing the sensor  110   b , transmitter/receiver  170   b  and hub  130   b  can be accomplished during assembly by a technician using a pairing device  275 . As noted above, the pairing may be very automatic, and to the extent needed, performed by the driver upon connection of the trailer  104   a . Many sensors and such devices can be difficult to physically access so that pairing upon installation is advantageous. A sensor, for example, might be located on an axle of the vehicle or within a vehicle braking system. The driver or technician&#39;s pairing device  275  may be able to read a code from the sensor, such as a QR code or NFC tag. The technician&#39;s pairing device  275  will be trusted by the VAN  101  (e.g. having passcode credentials for the network, or the like) and/or can be manually connected to the VAN  101 , whether wired or wirelessly. The pairing device  275  can then pair the sensor  110   b  to the hub  130   b  using the code from the sensor  110   b , thereby connecting the sensor  110   b  to the subnetwork  114  and, ultimately, to the VAN  101 . 
     Once the transmitter/receivers  170   a - d  are paired for wireless communication to corresponding wireless hubs  130   a - d , information can then be transmitted from multiple devices across the VAN  101 . The data can be processed and provided to a central location of the vehicle  100 , such as within the tractor  102  where the driver can see alerts, or other feedback related to the readings of the sensors  110   a - d.    
     In some cases, one or more of the tractor  102  and trailers  104   a ,  104   b  can include a 3rd party, on-board telematics device  116   a ,  116   b . In the example shown, the tractor hub  130   a  is in communication with a first telematics device  116   a  and the first trailer hub  130   b  is in communication with a second telematics device  116   b  in the first trailer  104   a . Each telematics device  116   a ,  116   b  transmits data to a third party source. In the example given, the data is transmitted to an external cloud platform where the data can then be obtained by external devices  120 , such as computers, smartphones or the like (e.g., the pairing device  275 ). The data can then be relied upon for fleet and asset management functions, such as checking health of various components of the truck. In other cases, the telematics devices  116   a ,  116   b  can transmit to mediums other than a cloud network, such as a wide area network or directly to third party devices. 
     Once information from the VAN  101  is transmitted out of the vehicle  100  to the external networks  118  and devices  120 , additional data review, analysis and insight can be ascertained. The analysis and insight can then be sent back to the trailer  102  for review by the driver. A suite of warning strategy functionality can be general or specific to particular needs. The algorithm that develops the warnings is optimized by ongoing data analysis. For example, the vehicle behavior is characterized so that particularly identified parameters can be measured. Some parameters are tire pressure with reference temperature, spare tire pressure, system temperature, system pressure, and gross vehicle weight (GVW). The external device  120  may have specific data such as a range or maximum allowable limit. Since the maintenance of these parameters is ongoing, if the GVW is over limit or out of range, or a tire is under low pressure or unsafe to drive on, a warning message can be sent to the driver for investigation and corrective action. For another example, a fast pressure loss in a tire would generate an alert to the driver. 
     The subnetworks  112 ,  114  for the vehicle  100  are part of and in local communication within the broader VAN  101 , with one wireless gateway hub acting as an access point for the VAN  101 . In some cases, the access point for the VAN  101  can change to a different gateway depending on the number of trailers  104  attached to the tractor  102  such that the access point is in a central location of the vehicle  100 . To centralize the access point, the tractor hub  130   a  searches down the length of the vehicle  100  for additional hubs  130  to determine a centrally located hub  130 . Since the hubs  130  will be somewhere along the length of the vehicle  100 , the VAN  101  can determine hub locations through a linear search, rather than by searching a broad surrounding radius. 
     If, for example, only a single trailer  104   a  is provided, the access point can be the wireless hub  130  in the center of the one trailer, which all devices (e.g., transmitter/receivers, sensors and the like) in the trailer  104   a  or tractor  102  can wirelessly reach. If the second trailer  104   b  is included, the access point could still be located within the first trailer  104   a  at a location central to the vehicle  100  or, alternatively at the dolly hub  130   c  which is also centrally located. If additional trailers are added (e.g. a third and fourth trailer), the access point can be changed to a new hub at a central location of the vehicle  100 , or can use multiple interconnect access points to leap frog wireless signals through the entire length of the vehicle  100 . Alternatively, a full WiFi mesh system could be used to connect many hubs at locations across the vehicle  100 . Having wireless hubs  130   a - d  which control the central communication at each area of vehicle  100  allows many devices to quickly and easily communicate over the VAN  101 , even when devices within the VAN  101  may be changed (e.g., sensor repair), or new or additional trailers and dollies may be added to the vehicle  100 . In each case, each new device need only be paired and connected to one wireless hub, and data from all devices can be shared across the VAN  101 . From the above, it should be understood that the exact number and arrangement of the components shown in  FIG. 1  are exemplary only, and should not be construed as limiting. 
     Autonomous Vehicles 
     As vehicles become self-driving, the subject technology wills seamlessly integrate with the suite of autonomous technology. For example, the data analysis from monitoring the sensors can be used to control speed or even redirect the autonomous vehicle to a service station or rest stop to attend to repairs. The data analysis may also require the autonomous vehicle to enter an emergency mode where the vehicle may be pulled over for towing or control ceded to a remote operator. 
     In one embodiment, the tractor and the trailer are merged as one. As would be expected, the integration of sensors on the trailer portion into the vehicle area network on the merged tractor-trailer is only required initially. The merged tractor-trailer can still connect and carry additional trailers. 
     Wireless Hubs 
     As used herein, a micro controller, computer or smart device is one or more digital data processing devices. Such a device generally can be a personal computer, computer workstation (e.g., Sun, HP), laptop computer, a tablet computer, server computer, mainframe computer, handheld device (e.g., personal digital assistant, Pocket PC, cellular telephone, etc.), information appliance, printed circuit board with components or any other type of generic or special-purpose, processor-controlled device, with or without application specific integrated circuits (ASICs), capable of receiving, processing, displaying, and/or transmitting digital data. A controller includes random access memory (RAM), mechanisms and structures for performing input/output operations, a storage medium such as a magnetic hard disk drive(s), and an operating system (e.g., software) for execution on a central processing unit (CPU). The controller also has input and output devices such as a display screen, a keyboard and mouse and the like. 
     A CPU generally is logic circuitry that responds to and processes instructions that drive a controller and can include, without limitation, a central processing unit, an arithmetic logic unit, an application specific integrated circuit, a task engine, and/or any combinations, arrangements, or multiples thereof. Software or code generally refers to computer instructions which, when executed on one or more digital data processing devices, cause interactions with operating parameters, sequence data/parameters, database entries, network connection parameters/data, variables, constants, software libraries, and/or any other elements needed for the proper execution of the instructions, within an execution environment in memory of the digital data processing device(s). 
     A module is a functional aspect, which may include software and/or hardware. Typically, a module encompasses the necessary components to accomplish a task. It is envisioned that the same hardware could implement a plurality of modules and portions of such hardware being available as needed to accomplish the task. Those of ordinary skill will recognize that the software and various processes discussed herein are merely exemplary of the functionality performed by the disclosed technology and thus such processes and/or their equivalents may be implemented in commercial embodiments in various combinations without materially affecting the operation of the disclosed technology. 
     Referring now to  FIG. 2A , an exploded view of a wireless hub  130  is shown. Each hub  130   a - d  may be differently configured, but in  FIG. 2A  an exemplary hub  130  is shown. The wireless hub  130  includes an enclosure  131  with a removable lid  132  that connects to form a protected interior  133 . The enclosure  131  forms opposing recesses  134  for compression limiters  135  to maintain the joint integrity of the plastic enclosure  131 . The hub  130  includes a printed circuit board (PCB)  136  having electronics, such as a processor and memory (not explicitly shown) required to create modules to carry out the functions of the wireless hub  130 , including data processing, storage, and transmission. 
     The wireless hub  130  has an antenna (not shown explicitly) connected to the PCB  136  for wireless transmission. Additional antennas may be included as needed to allow the hub  130  to transmit and receive data with other devices as described herein. For wired connections, the hub  130  includes connecting pins  138 . The hub  130  may be powered by a battery and/or from a wired connection. In one embodiment, the hub  130  is connected to a +12/24V supply  144  (see  FIG. 2B ). The wireless hub  130  is configured to withstand large temperature changes in the range of −40° C. to +85° C. The hub  130  mounts external to the tractor cabin such as on the chassis rail. 
     Referring now to  FIG. 2B , a schematic diagram of a micro controller  140  suitable for use as a portion of the wireless hub  130  is shown. Typically, the micro controller  140  is part of the PCB  136  of  FIG. 2A . The PCB  136  includes additional separate peripheral modules  141 ,  142 ,  143 ,  144 ,  145  and such may be incorporated into the micro controller  140 . The micro controller  140  and modules  141 ,  142 ,  143 ,  144 ,  145  may include one or more standardly available components or be fabricated as one or more ASICs. 
     The hubs  130   a - d  can transmit and/or receive data between other hubs and/or range extenders  170   a - d  using a WiFi module  141  with a 2.4 GHz frequency band. The WiFi module  141  creates tractor-to-trailer transparent IP-based data communication. A second 802.15.4 thread network protocol communication module  142  can send and receive additional sensor content and range extension. A third communication module  143  can use sub-GHz (e.g., a 433 MHz frequency band) with on-board decode and polling functionality for low power modes. The third communication module  143  is particularly well-suited for data from nearby sensors that are battery powered and, thus, low power. 
     The micro controller  140  can also be connected for communication to a CAN bus  145 , which is typically located in the tractor  102 . The micro controller  140  can also be directly connected to another wireless hub  130  so that the hub  130  can act as a radio frequency (RF) to CAN gateway. The PCB  136  also includes a 12/24 V power supply  144  with surge protection to power and protect the micro controller  140  and other components from electrical damage. 
     When the micro controller  140  is operating, hardware  147  creates a runtime environment (RTE)  146  so that the stored programs are running (e.g., instructions are being executed). The hardware  147  includes a processor  148  coupled to memory  149  along with other components not explicitly shown. Programs are stored in the memory  149  and accessed by the processor  148 . A boot loader module  150  allows programming to the memory  148 . An operating system module  151  allows the user to interface with the hardware  147 . An ECU abstraction layer module  152  facilitates uniform access to the micro controller functions performed by peripherals and application program interfaces (APIs). A MCAL micro controller abstraction layer module  153  facilitates direct access to the devices on the PCB  136 . A complex device drive module  154  includes various sub-modules  155   a - c  to implement drivers for the communication devices  141 ,  142 ,  143  as needed. The boot-loader module  150  can run the micro controller  140  for programming and writing information to the memory  149 . 
     As can be seen, the micro controller  140  is specifically designed for use in the VAN  101 . The micro controller  140  also includes a power manager module  156  and a Truck to Trailer network link software module  157 . The micro controller  140  includes a TPMS module  158  and onboard weight motor vehicle unit module  159  to accomplish TPMS and MVU weight measurements in the VAN  101 . The micro controller  140  also includes a RF network management module  160  and a third party software component module  161  to facilitate use of RF network components and third party software. Other modules may be present in the micro controller  140  to accomplish any desired features in the VAN  101 . Further, the micro controller  140  features may be expanded by having hardware and software ready to host additional software and support other components (e.g., additional sensors, hubs, subnetworks). 
     Transmitters/Receivers 
     Referring now to  FIGS. 3A and 3B , an exploded view and a schematic view of an exemplary transceiver/receiver  170  are shown, respectively. The transmitter/receiver  170  includes an enclosure  171  forming a cavity  172  that is sealed with a lid  173  for protection of a printed circuit board (PCB)  174 . Again, one or more compression limiters  175  fit in the enclosure  171  to maintain the joint integrity of the plastic enclosure  171 . The PCB  174  includes the electronics to carry out all the functions of the transmitter/receiver  170  including sending/receiving data, data processing, and storage. The PCB  174  may include a processor, memory, an antenna and other components (not explicitly shown). 
     For wired connections, the transmitter/receiver  170  includes a connector  176 . The transmitter/receiver  170  may be powered by a battery and/or from a wired connection. In one embodiment, the hub  130  is connected to a +12/24V supply  183 . The transmitter/receiver  170  is also configured to withstand large temperature changes in the range of −40° C. to +85° C. Preferably, the transmitter/receiver  170  can mount in any suitable location but outside the chassis rail is preferred. 
     Typically, most, if not all functional modules, are created by components of the PCB  174  but one or more peripheral components  181 ,  182 ,  184  could also be utilized. The PCB  174  may include one or more standardly available components or be fabricated as one or more application specific integrated circuits (ASICs). The components of the PCB  174  work together to form a central processing unit  180 . 
     The transmitter/receiver  170  can transmit and/or receive data to hubs and/or other transmitter/receiver  170  using a 802.15.4 thread network protocol communication module  181  as well as send and receive additional sensor content. Thus, the transmitter/receiver  170  can be used to enlarge the size of the VAN  101 . A sensor communication module  182  uses sub-GHz (e.g., a 433 MHz frequency band) for low power modes to efficiently work with nearby sensors that are battery powered. 
     When the transmitter/receiver  170  is operating, a runtime environment (RTE)  183  is created so that the stored programs are running (e.g., instructions are being executed). The PCB  174  may include a processor coupled to memory along with other components not explicitly shown. The programs are stored in the memory and accessed by the processor. One program is an operating system module  184  that allows the user to interface with the hardware  147 , typically using the pairing device  275 . 
     A hardware abstraction layer module  185  facilitates uniform access to the range extender functions. A supplier software development kit (SDK) module  186  facilitates creation of applications with advanced features specific to the transmitter/receiver  170  and operating system module  184 . The PCB  174  includes a communications stack module  187  to support the 802.15.4 thread network protocol communication module  182 . 
     As can be seen, the transmitter/receiver  170  is specifically designed for use in the VAN  101 . The transmitter/receiver  170  includes a power manager module  188  and a packet forwarder module  189  for assisting with data conversion. The transmitter/receiver  170  also includes a diagnostic and commissioning module  190  that provides a user interface via the smart device  275  for start-up and troubleshooting purposes. Other modules may be present in the transmitter/receiver  170  to accomplish any desired features in the VAN  101 . Further, the transmitter/receiver  170  features may be expanded by having hardware and software ready to host additional software and support other components. 
     The transmitter/receiver  170  is particularly beneficial when retrofitting technology on to an existing trailer or tractor for future incorporation into a vehicle area network. The transmitter/receiver  170  may connect to various sensors, wired or wirelessly, then pass along the data to a wireless hub. In effect, the transmitter/receiver  170  is the additional hardware to bridge communications with existing hardware to the new networked components. 
     Tire Pressure Monitor System 
     Further, the sensors may also be retrofit. For example, see U.S. patent application Ser. No. 16/119,109 filed on Aug. 31, 2018 entitled TIRE PRESSURE MONITOR WITH VARIABLE ANGLE MOUNTING, which is incorporated herein by reference. In addition to sensors indicating the tire pressure, the sensors may auto-locate or be programmed to indicate wheel position. As such, when the VAN  101  identifies a pressure reading, the pressure reading is associated with a specific tire. The tire-related data can include temperature data as well, which is also an indication of proper and improper performance. 
     It is envisioned that the smart device  275  can be used to assist in refilling tire pressure alleviating the need for a tire pressure gauge by having the pressure reading on the smart device  275  or other indicia, such as beeping the horn/flashing the lights, to indicate that the pressure is within specification. If the tire is equipped with automatic tire fill, the VAN  101  can trigger refill and stop at the desired pressure. The sensors can also provide an indication that the lift axle is lowered but the tire is not turning. In this instance, a tire lock warning could be generated and/or acted upon such as in an autonomous vehicle. Similarly, a tire blow out can be detected quickly after the burst event to send a warning indicating the blow out and location. In the self-driving vehicle, the tire burst warning generates a reaction for safety and control. Preferably, the sensors are battery powered with efficient power usage for long life. 
     Beacons 
     Referring now to  FIGS. 4A and 4B , a perspective and a bottom exploded view of a beacon  200  in accordance with the subject technology is shown. The beacon  200  may mount to the trailer  104   a  magnetically, with a bracket or by any other fastener. A bottom plate  202  forms two recesses  204 . Screws  206  hold magnets  208  in the recesses  204  so that the beacon  200  can simply be placed against the trailer  104   a  for mounting and easily removed without tools for wireless charging, relocation, repair and the like. The bottom plate  202  has an indicia arrow  210 . 
     The beacon  200  also includes a rechargeable battery  212  for a power source. A printed circuit board (PCB)  214  has an LED  216  (shown in dashed lines) that illuminates to show such information as the status of the trailer  104   a  (e.g., connected to the VAN  101  (e.g., solid light) or in process of being connected (e.g., flashing light)). The PCB  214  also has components to wirelessly communicate with the hubs  130   a - d  and or transmitter/receivers  170   a - d . The PCB  214  is also equipped to interface with a smart device  218  that can use near-field communication (NCF). The PCB  214  also has a GPS module  220  (shown in dashed lines) so that the VAN  101  can locate the beacon  200 , and in turn the trailer  104   a  at a great distance as described above. The beacon  200  also has a PCB top plate  222  for protecting the PCB  214 . The PCB top plate  222  has a translucent window  224  aligned with the LED  216 . A top cover  226  couples to the bottom plate  202  to seal the battery  212 , PCB  214  and PCB top plate  222  within an oval housing  228 . Preferably, the top cover  226 , bottom plate  202 , PCB  214 , PCB top plate  222  and oval housing  228  have features  230  for screwing together. The PCB top plate  222  and top cover  226  also have a plurality of aligned holes  232 . 
     Multi-Trailer Ordering 
     Referring now to  FIG. 5 , another exemplary vehicle area network (VAN)  301  for a tractor-trailer vehicle  300  is shown. The components and functionality of the VAN  301  and tractor-trailer vehicle  300  can be similar to the vehicle  100  and VAN  101  described above, except as otherwise indicated herein. Thus, like reference numerals in the “3” series represent similar components. For clarity, several components are not shown. 
     The vehicle  300  includes a tractor  302  with three trailers  304   a - c  and two dollies  306 , all including components similar to those discussed with respect to  FIG. 1 . The VAN  301  allows for communication between all of the components of the vehicle  300 , such as wireless hubs  330   a - d , sensors  310   a - f  (e.g., TPMS, pressure sensors, temperature sensors and the like), beacons  200 , and the like, as discussed above. The tractor  302  and each trailer  304   a - c  have a corresponding subnetwork  314   a - c  within the VAN  301  which connects the components proximate the respective trailer  304   a - c . Although not shown, it is envisioned that the VAN  301  includes transmitter/receivers and other components as desirable for robust performance. Each trailer  304   a - c  also includes a beacon  200  for assisting the driver in assembling the vehicle  300 . 
     It is advantageous for the VAN  301  to be informed of the relative location of the trailers  304   a - c  and/or subnets  314   a - c  established on the vehicle  300 . The VAN  301  having the relative location helps to identify where various sensors, and other components such as the tires, are located. In some cases, it can be a challenge for the VAN  301  to identify the exact ordering of the trailers  304   a - c . Further, even if this is manually calibrated, trailers are often dropped off, and new trailers picked up and attached to the truck, requiring the new trailers to be ordered within the VAN  301 . Therefore, it is advantageous for the VAN  301  to be capable of connecting to and establishing communication with trailers automatically and determining an order of the trailers. 
     Referring now to  FIGS. 6A-6D , a flowchart  600  of a method for automatically recognizing the order of three trailers  304   a - c  on the vehicle  300  is shown. The method relies on data, including signal strength and time of flight (ToF) to continuously monitor and update the status of the vehicle  300 . The flowchart herein illustrates the structure or the logic of the present technology, possibly as embodied in computer program software for execution on by the hardware described herein. Those skilled in the art will appreciate that the flowchart illustrates the structures of the computer program code elements, including logic circuits on printed circuit boards having integrated circuits that function according to the present technology. As such, the present technology may be practiced by a machine component that renders the program code elements in a form that instructs a digital processing apparatus (e.g., micro controller or computer) to perform a sequence of function step(s) corresponding to those shown in the flowchart. 
     At step  602 , the method starts with the micro controller of each hub  330   a - d  being powered up and in normal operation to form the respective subnetworks  312 ,  314   a - c  but, at this time, the trailer order is unknown and the trailers  304   a - c  can be in any order. At step  604 , each subnetwork  312 ,  314   a - c  monitors received signal strength indicators (RSSI) and ToF data from all other subnetworks  312 ,  314   a - c . If other hubs were not present, the same data could come from range extenders or even directly from sensors. 
     At steps  606  and  608 , the tractor hub  330   a  identifies a trailer subnetwork  314   a  with the highest RSSI and the shortest ToF. The trailer subnetwork  314   a  with the highest RSSI and shortest ToF should be the lead trailer  304   a  physically closest to the tractor  302 . At step  610 , the tractor hub  330   a  compares the subnetwork  314   a  identified with the highest RSSI to the subnetwork  314   a  with the shortest ToF. If the subnetworks of steps  606  and  608  do not match, meaning the subnetwork with the highest RSSI is different from the subnetwork with the shortest ToF, the method restarts at step  602 . At step  612 , if there is a match by both being subnetwork  314   a , subnetwork  314   a  is identified as being on the first trailer  314   a  (e.g., the lead trailer). Further, if at step  610 , there is only an RSSI and ToF from the same subnetwork  314   a , then the tractor subnetwork  312  can identify the associated trailer  304   a  as the one and only trailer present. 
     After the lead trailer  304   a  is identified successfully, the lead trailer wireless hub  330   b  identifies the subnetwork  314   b  with the highest RSSI and the shortest ToF with respect thereto, excluding the tractor subnetwork  312  in both cases at steps  614  and  616 . At step  618 , if there is a match, then the respective subnetwork  314   b  is identified as the second trailer  304   b  immediately after the lead trailer  304   a  at step  620  as shown on  FIG. 6 b   . If there is no match at step  618 , the method restarts at step  602 . In another embodiment, the method restarts at step  612  by using the previously established lead trailer identification. If at steps  614  and  616 , there are only an RSSI and ToF from two subnetworks  314   a ,  314   b , then the tractor subnetwork  312  can identify and order the associated two trailers  304   a ,  304   b . In one embodiment, the process end after successful identification at step  620 . 
     Once the second trailer  304   b  is identified, any of the hubs  330   a ,  330   b  or the trailer wireless hub  330   c  of the second trailer  304   b  can identify the third trailer  304   c . To that end, in the following description the second trailer wireless hub  330   c  is used. At steps  622  and  624 , the hub  330   c  identifies the subnetwork  314   c  with the highest RSSI and the shortest ToF excluding the tractor subnetwork  312  and the lead trailer subnetwork  314   a  in both cases. At step  626 , if there is a match, it is assumed the identified subnetwork  314   c  corresponds to the third trailer  304   c  (i.e. the trailer  304   c  immediately after the second trailer  304   b ). The third trailer  304   c  is identified at step  628  based on the third trailer subnetwork  314   c , as shown on  FIG. 6 b   . If there is no match at step  626 , the entire process is restarted at step  602  but may alternatively return to step  620 . 
     The steps to identify the next trailer in a line of trailers can be repeated for additional trailers, as would be understood by one of skill in the art. Assuming the vehicle  300  has three trailers  304   a - c , as in the example of  FIG. 5 , the first results ordering the three trailers  304   a - c  have then be determined at step  630 , which indicate an initial order of all the trailers  304   a - c . If at steps  622  and  624 , there are only an RSSI and ToF from three subnetworks  314   a - c , then the tractor subnetwork  312  can identify and order the associated three trailers  304   a ,  304   b  and end the method or proceed with a double check as follows. For more trailers, the method may continue. 
     After step  630  to double check, the process of determining the order of the trailers  304   a - c  is then substantially repeated, in reverse order, to get a second set of results for comparison to determine whether the initial ordering was accurate. In more detail, referring now to  FIG. 6 c   , the method continues to monitor RSSI and ToF data from all other subnetworks  314   a - c  at step  632 . At steps  634  and  636 , starting with the identified third trailer  304   c , the third trailer subnetwork  314   c  identifies the subnetwork  314   b  with the highest RSSI and the shortest ToF by comparing data from all of the identified subnetworks  312 ,  314   a - b . At step  638 , subnetwork(s) with the highest RSSI and the shortest ToF are compared. If the identified subnetworks with the highest RSSI and the shortest ToF are different, the method restarts to step  632 , but if there is a match, then the identified subnetwork  314   b  is determined to correspond to the second trailer  304   b . The identification of location of the second trailer  304   b  is saved as part of the second set of results at step  640 . 
     At steps  642  and  644 , the newly identified second trailer subnetwork  314   b  then identifies the highest RSSI and the shortest ToF excluding the third trailer subnetwork in both cases. At step  646 , the second trailer subnetwork  314   b  compares the identified subnetworks, typically subnetwork  314   a  for each criteria. If there is a match, then the identified subnetwork (e.g., subnetwork  314   a ) is determined to correspond to the lead trailer  304   a  and saved as part of the second set of results at step  648 . If the identified subnetworks are different at step  646 , the method restarts at step  632 . 
     Referring now to  FIG. 6 d   , the identified lead trailer subnetwork  314   a  then identifies the subnetwork with the highest RSSI and with the shortest ToF excluding the second and third trailer subnetworks  314   b - c , in both cases at steps  650  and  652 . At step  654 , the lead trailer subnetwork  314   a  compares the identified subnetworks. If there is a match, properly being the tractor subnetwork  312 , then the method proceeds to step  640  where the identified tractor subnetwork  312  is determined to correspond to the tractor  302 . The method gathers and saves the information related to the three properly located subnetworks  312 ,  314   a - b  as part of the second set of results at step  658 . 
     At step  660 , with the subnetworks  312 ,  314   a - b  identified and ordered a second time, the first and second set of results are then compared. If the ordering determined in the first set of results is consistent with the ordering determined in the second set of results, then it is verified that order of the VAN subnetworks  312 ,  314   a - c  have been correctly determined and the method ends at step  662 . Otherwise, if the order determined in the first and second set of results is different, then the method starts over at step  602  so a verified order can be determined. 
     In this way, the VAN  301  is able to automatically determine an order of the trailers  304   a - c  based on the order of the subnetworks  330   b - d  with no input from the user. The order of the trailers  304   a - c  can then be relied upon to determine where various sensors are located, and to easily take action based on a sensor readings and/or alert. For example, if a tire pressure monitoring sensor reports data that triggers a low pressure alert, it is advantageous for the user to be able to narrow down the potential tire(s) corresponding to that alert. A given sensor&#39;s subnet can be used to determine which trailer (or tractor) the sensor is a part of, based on the ordering of the trailers with no additional input needed from the user. Thus, if the pressure sensor reporting the alert is in the third trailer subnetwork  314   c , the user can be alerted that a tire of the third trailer  304   c  has low pressure. This avoids the need for the user to spend time checking the tires for the tractor  302  or the other trailers  304   a - b . This can be similarly used for readings and alerts for other known sensors as are known in the art. 
     It is also envisioned that the dollies  306  can have wireless hubs that form separate subnetworks rather than part of the trailer subnetworks  314   b - c , respectively. In this instance, the dolly subnetworks would be similarly identified and ordered in the method of ordering the subnetworks. The process described herein can use shared specifications for standardized information. The shared specifications allow the process of linking trailers to the VAN  101 ,  301  and ordering the trailers to be easily carried out across multiple truck and trailer brands. Preferably, no secondary user action is required to determine the ordering of the trailers  104 ,  304 . For example, the method for ordering the trailers  104 ,  304  can be activated upon making the electrical and/or pneumatic connections between the tractor  102 ,  302  and the trailers  104 ,  304 , as well as between the trailers  104 ,  304 . The method can also be triggered by using the smart device  275 . 
     Referring now to  FIG. 7A-20E , various brake and sensor arrangements are shown. The sensor arrangements can be incorporated into the VAN  101  of  FIG. 1 , as described above. Referring to  FIGS. 7A and 7B , a sensor arrangement  700  is shown. The sensor arrangement  700  includes a stationary sensor portion  702  and a moving target portion  704 . The portions  702 ,  704  are mounted to the brake assembly with the sensor portion  702  fixed to a casting or other stationary feature whereas the target portion  704  is mounted on a moving feature. Thus, as brakewear occurs and the brakes are engaged, the target portion  704  moves with respect to the sensor portion  702  commensurate with the brakewear and, in turn, the signal from the sensor portion  702  varies to indicate wear. The sensor arrangement  700  can be mounted in preset cast location, retrofit on existing assemblies, integrally fabricated with the braking assembly, and combinations thereof. Generally, the sensor arrangement  700  is not integrated with a consumable portion so that by being battery powered, the sensor arrangement  700  can perform measurements after many other consumable parts (e.g., brake pads) have been replaced many times. It is envisioned that the sensor arrangement  700  may require calibration during replacement of parts. 
     Typically, the range of motion of the target portion  704  is limited so that calibration and proper positioning is required so that a leading edge  706  of the target portion  704  is aligned with a start of travel line  708  with no wear. As maximum brakewear approaches, the leading edge  706  approximately aligns with an end of travel line  710  or less. 
     Referring now to  FIGS. 8A-C , a floating caliper brake system  800  with a sensor assembly  820  is shown. The brake system  800  is on each end  870  of an axle  872 . When the brakes are applied, a floating caliper  802  moves in a linear direction parallel to motion arrow  804  with respect to a fixed carrier  806  to force brake pads against a wheel (not distinctly shown). The sensor assembly  820  (shown in isolation in  FIG. 8C ), includes a fixed sense element  822  and a moveably mounted target portion  824 . The target portion  824  includes a magnet  826  while the sense element  822  includes an anisotropic magnetic resistivity (AMR) sensor on a printed circuit board (PCB)  828  that detects a magnetic field based on the positioning of the magnet  826 . 
     In the example given, the sense element  822  is attached to the carrier  806  while the target  824  is attached to the floating caliper  802 . When the brakes are applied, the floating caliper  802  moves and the target  824 , which is positioned to move parallel to the fixed sense element  822 , such that the target  824  changes position and/or angle with respect to the sense element  822 . The movement of the target  824  is measured by the sense element  822  and reported to a subnetwork, wireless hub and/or VAN. 
     The brake pad thickness and/or wear can then be determined based on the measured movement and the range of motion between the floating caliper  802  and carrier  806 . Measurements from sensors across the vehicle can be matched up with the corresponding location on the vehicle to determine brake pad thickness at various locations. Brake pad thicknesses can be analyzed within the VAN to compute remaining pad thickness and compare that thickness to regulatory allowances. 
     If the thickness of a brake pad falls below an acceptable level, a warning can be generated within the tractor for the driver, thereby identifying a particular brake pad that needs replacing. Further, the data from one or more sensors can be used to verify a new brake pad from the initial offset measured when the brakes are applied or for wheel-to-wheel comparisons. For example, excessive wear on a single wheel may indicate a sticking caliper so that a maintenance check can be scheduled. Measurements can be stored and analyzed to determine a wear rate and overall slope of brake pad wear over time. Based on the data, maintenance reminders and scheduling is done automatically. Changes in wear rate or slope can be indicative of fault conditions with a given brake, correlated to driver behavior, or attributable to a change in primary driving conditions, and corresponding warnings can be issued to the driver and/or the fleet manager. The positioning of the sense element  822  and target portion  824  could also be reversed, with the sense element  822  attached to the floating caliper  802  while the target portion  824  is attached to the carrier  806 . 
     Referring now to  FIGS. 9A-C , another brake system  900  with a sensor assembly  920  is shown. The brake system  900  is shown on an axle  972  in  FIG. 9A . The brake system  900  is a fixed caliper brake system where the brake pad  902  moves with respect to the fixed caliper  906  shown in more detail and isolation in  FIG. 9B . Therefore, the sense element  922  can be attached to the fixed caliper  906  with the target portion  924  attached to the brake pad  902 , or the support structure around the brake pad, to move linearly as the brake pad  902  moves. Alternatively, the sense element  922  could be attached to the brake pad  902  and the target portion  924  attached to the fixed caliper  906 . Again, the signal from the sense element  922  may be wirelessly transmitted. Further, the brake system  900  is separate from consumable components and battery powered so that other than possibly needing recalibration, the brake system  900  may last for the life of the vehicle. The calibration of the brake system  900  is preferably performed automatically or by using a smart device in communication with the vehicle area network. 
     Referring now to  FIGS. 10A-E ,  FIG. 10A  is a perspective semi-exploded view of a disc brake system  1000  in accordance with the subject technology.  FIG. 10B  is a different perspective semi-exploded view of the disc brake system  1000 .  FIGS. 10C-E  are detailed views of a brake sensor assembly  1020 . 
     The disc brake system  1000  includes a stationary mounting plate  1002 . Preferably, the sensor element  1022  can be mounted to an attachment plate  1012  (see  FIG. 10C ), which can in turn be attached to the stationary mounting plate  1002  at location  1003 . The target portion  1024  mounts on a floating portion of the caliper  1110 , thereby moving with the pads as the pads wear during braking. A preferred location for mounting the target portion  1024  is a circular projection  1006 . As can be seen in  FIG. 10C , the sense element  1022  and the target portion  1024  can be retrofit by using brackets  1023 ,  1025 , respectively. Alternatively, in  FIG. 10D , the target element  1024  is integrated into the casting  1027 . For example, the casting  1027  is part of the circular projection  1006 . 
     Referring now to  FIGS. 11-20E , other brake systems and brake sensor assemblies are shown. The systems and sensor assemblies can work as described with respect to systems and sensor assemblies above, except as otherwise described herein. In particular, the brake systems in  FIGS. 11-20E  are drum brake systems, and all sensor assemblies shown therein are configured for use with a drum brake system as described below. 
     Referring now to  FIGS. 11-13 , the vehicle (not shown) includes an axle  1202  having a brake system  1200  on each end  1204 . When the brakes are applied, either by the driver or by command in an autonomous vehicle, an air brake chamber  1212  actuates a push arm or pushrod  1208  along motion arrow  1209 . The movement of the pushrod  1208  rotates a cam shaft  1210  that controls movement of the brake pads. 
     Referring particularly to  FIGS. 12 and 13 , an exemplary sensor assembly  1320  is shown on the drum brake system  1200  and in isolation, respectively. The sensor assembly  1320  includes a sense element  1322  and a target portion  1324 , which can be similar to the other sensors described herein. An air brake chamber  1212  of the brakes actuates the pushrod  1208  when the brakes are applied. A fixed brake chamber bracket  1216  is attached to the brake chamber  1212 , the pushrod  1208  extending through an aperture  1218  in the brake chamber bracket  1216 . The sense element  1322  is attached to the chamber bracket  1216  while the target portion  1324  is attached to the pushrod  1208 . When the brakes are applied, the pushrod  1208  moves, changing the position of the target portion  1324  relative to the sense element  1322 . These relative positions are measured and can be used to first calculate chamber stroke and ultimately calculate brake pad wear by means of algorithms that correlate the stroke of the brake chamber  1216  through the geometry of the slack adjuster, cam shaft/cam, and cam follower. The measured data from the sensor assembly  1320  can then be used as described with respect to other sensors herein. 
     Referring now to  FIGS. 14 and 15 , an exemplary sensor assembly  1520  for a drum brake system  1400  is shown on the brake system  1400  and in isolation, respectively. The sensor assembly  1520  includes a sense element  1522  and an arcuate target element  1524 , which can be similar to the other sensors described herein. The brake system  1400  includes a pushrod  1408  that moves parallel to motion arrow  1409 . The pushrod  1408  is connected to a slack adjuster head assembly  1430  so that when the pushrod  1408  moves, the slack adjuster head assembly  1430  rotates as shown by motion arrow  1431 . The target portion  1524  is mounted on the slack adjuster head assembly  1430  for rotational motion therewith. The brake system  1400  also includes a fixed mounting plate  1420  with the sense element  1522  coupled thereto. 
     When the brakes are applied, the pushrod motion  1409  causes the rotary motion  1431  of the slack adjuster head assembly  1430  and, in turn, similar motion of the target portion  1524 . The sense element  1522  does not move. Thus, when the brakes are actuated, the position of the target portion  1524  relative to the sense element  1522  changes. These relative positions are measured and can be used to calculate brake pad wear by means of algorithms, as are described herein. The measured data from the sensor assembly  1520  can then be used as described with respect to other sensors herein. 
     Referring now to  FIGS. 16 and 17 , another drum brake system  1600  and exemplary sensor assembly  1720  are shown. The sensor assembly  1720  includes a sense element  1722  and a target portion  1724 , which can be similar to the other sensors described herein. The drum brake system  1600  is also similar to the brake system  1200  described above. The drum brake system  1600  includes an adapter plate  1626  coupled to an adjuster arm  1630 . The adapter plate  1626  facilitates coupling the sense element  1722  in a fixed location. The target portion  1724  is attached to the adjacent moving adjuster arm  1630 . Alternatively, the adapter plate  1626  could carry the target portion  1724  and the sense element  1722  could be attached to the adjuster arm  1630 . In either case, the adapter plate  1626  exemplifies a possible retrofit application. 
     When the brakes are applied, the pushrod motion  1609  again causes a rotary motion  1631  of the slack adjuster arm  1630 . In the example given, the target portion  1724  is attached to the moving adjuster arm  1630  and the sense element  1722  is fixed to the stationary adaptor plate  1626 . Therefore, when the brakes are applied, the position of the target portion  1724  relative to the sense element  1722  changes. These relative positions are measured and can be used to calculate brake pad wear by means of algorithms as described herein. The measured data from the sensor can then be used as described with respect to other sensors herein. 
     Referring now to  FIGS. 18 and 19 , yet another drum brake system  1800  with an exemplary sensor assembly  1920  are shown. The sensor assembly  1920  includes a sense element  1922  and a target portion  1924 , which can be similar to the other sensors described herein. The drum brake system  1800  is also similar to drum brake system  1200 . The drum brake system  1800  includes an indicator plate  1840  coupled to a cam shaft  1850 . 
     When the brakes are actuated, the cam shaft  1850  rotates along arrow  1851  to cause the brake pads to contact the drum. The target portion  1924  is attached to the indicator plate  1840  which does not move in response to the brake pads being applied. However, the sense element  1922  is attached to the adjuster arm  1830  which moves when the cam shaft  1850  rotates. Therefore, when the brakes actuate, the position of the target portion  1924  relative to the sense element  1922  changes. These relative positions are measured and can be used to calculate brake pad wear by means of algorithms similar to those described herein. The measured data from the sensor can then be used as described with respect to other sensors herein. 
     Referring now to  FIG. 20A , the end of a drum brake system  1950  which is normally proximate a wheel is shown. The drum brake system  1950  can include the other components of drum brake systems as are described herein, and can be incorporated as part of any other drum brake system described herein. As described above, when the brakes are applied, actuation of the pushrod translates into rotation of a cam shaft (e.g. rotation of shaft  1210  in  FIG. 11 ). This results in rotation of an s-cam  1952  on the end of the cam shaft. The drum brake system  1950  includes opposing brake shoes  1954  which are configured to pivot around anchor pins  1956 . On the end distal from the anchor pins  1956 , each brake shoe  1954  includes a cam follower  1964 . Rotation of the s-cam  1952  engages the cam followers  1964 , forcing the brake shoes  1954  outward along motion line  1966 . When the brake system  1950  is fixed within a wheel during normal operation, the outward movement of the brake shoes  1954  causes the brake linings  1958  to engage the wheel and stop movement of the wheel. 
     Referring now to  FIG. 20B , a comparison is shown of the positioning of the s-cam  1950  with the brakes disengaged in image  1960  and with the brakes engaged in image  1962 . As can be seen, the cam followers  1964  are separated by first distance D 1  when the brakes are disengaged. When the brakes are engaged, cam followers  1964  slide along the rotating s-cam  1955  and reach a final separation distance D 2  as the brakes are fully engaged. To show the rotational movement of the s-cam  1952 , a phantom image of the s-cam  1968  in the original disengaged position with the brakes disengaged is shown in dashed lines superimposed over the final s-cam  1952  position in the example showing the brakes engaged  1962 . In the engaged position in the example shown, the s-cam  1952  has rotated roughly 14 degrees between the disengaged and engaged positions of images  1960 ,  1962 . As the brake pads wear, greater total rotation becomes required to fully engage the brakes. 
     Referring now to  FIGS. 20C-E , examples of typical positions of s-cams and cam followers are shown over life span of the brakes. In particular,  FIG. 20C  represents s-cam and cam follower positioning for a new brake,  FIG. 20D  represents s-cam and cam follower positioning for a brake near the middle of the brake life cycle, and  FIG. 20E  represents s-cam and cam follower positioning for a brake near the end of the brake life. In each  FIG. 20C-E , the s-cam  1970  and cam followers  1972 , in dashed lines, represent the positioning for a disengaged brake system, while the s-cam  1974  and cam followers  1976  represent the positioning for an engaged brake system. The slack adjuster of the braking system includes an adjuster mechanism that automatically compensates for brake pad wear by adjusting the positioning of the s-cam  1970  over the life of the brakes. In the example given, the slack adjuster seeks to keep the s-cam  1970  positioned such that approximately 14 degrees of rotation of the s-cam  1970  occurs between the disengaged s-cam  1970  and the engaged cam  1974 . As the pads wear, the rotation required to fully engage the brakes increases. As can be seen, the s-cam  1970 ,  1974  position varies with wear so that the separation D 1 , D 2 , D 3  between the cams  1972 ,  1976  increases with increased wear, with separation D 3 &gt;D 2 &gt;D 1 . Through this process, the opposing arcuate portions  1975 ,  1977  of the s-cam  1970 ,  1974  continue to interact with cam followers  1972 ,  1976  when the breaks are applied. 
     Referring now to  FIG. 20F , a graph  1978  of cam follower displacement at various s-cam rotations is shown. The concentric circles  1980  are zeroed at the center of the graph  1978  and represent a growing displacement between opposing cam followers in mm as the concentric circles  1980  approach the perimeter of the graph  1978 . The circular perimeter  1982  represents a displacement distance of the s-cam  1979 . The plot points  1984  represent the displacement of the cam followers at s-cam angle increments of 10 degrees. For ease of explanation, the values of the cam follower displacement at each s-cam angle plotted are then consolidated in a table  1986 . 
     Referring now to  FIG. 20G , the table  1986  is plotted in a typical line graph format in graph  1989 . The x-axis represents rotation angle of the s-cam in degrees, while the y-axis represents displacement distance between the cam followers in mm. The plot points  1988  are the values shown in the table  1986 , which are also the plot points  1984  of the graph  1978 . A trend line  1990  can then be formed between the plot points  1984 . An equation  1992  of the trend line  1990  can be calculated. At any given point of the brake life, brake pad thickness can then be calculated using the difference between the current cam follower separation and the initial cam follower separation when the brakes were new. This is done in accordance with the following equation: 
     
       
         
           
             
               
                 
                   Thickness 
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                         t 
                         i 
                       
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                         m 
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                               θ 
                               n 
                             
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                               θ 
                               i 
                             
                           
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                   Eqn 
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                   1 
                 
               
             
           
         
       
     
     In Equation 1, Thickness is the current calculated brake thickness to be determined, t i  is the initial brake pad thickness, m is the slope of the trend line  1990 , θ n  is the current s-cam angle, and θ i  is the initial s-cam angle. For example, if the initial s-cam angle for a brake system was 0 degrees, and the initial brake bad thickness was 22 mm, and assuming a graph slope of 0.1861 as calculated in  FIG. 20G , Equation 1 for a current s-cam angle of 100 degrees would yield the following: Thickness=22 mm−0.1861 (100−0)=3.39 mm. Thus, when the s-cam rotation is at an angle of 100 degrees, the current brake pad thickness is determined to be 3.39 mm. This process can be repeated at different s-cam angles over the brake life to determine a brake pad replacement timing well in advance of brake failure. Notably, initial and current s-cam angles and cam follower displacement should be compared during like braking states (i.e. disengaged or engaged). In general, this process can be employed as an algorithm in connection with the braking systems described herein and used to calculate brake pad wear. As such, various sensors can be employed to gather data related to the s-cam rotational position, including any of the other position sensors described herein. 
     Based on the thickness calculations described above, a corresponding alert or message can be displayed for the user, indicating current brake pad thickness, wear, and/or likely miles until failure or recommended maintenance based additionally on the miles traveled to reach the current level of wear and likely level of brake pad failure. For example, assume the brake pad had worn from 20 mm to 10 mm in thickness over the first 100,000 miles traveled, and brake pad failure is assumed to occur at 5 mm. The brake system could include an algorithm to interpolate between the initial brake pad thickness of 20 mm to the expected failure thickness of 5 mm to determine that the brake pads were likely to reach 5 mm, and therefore fail, in another 50,000 miles. The remaining miles until expected brake pad failure could be displayed to the user constantly, or the system could be configured to automatically generate display a warning or alert a certain number of miles in advance of the expected failure point. The system could also factor in more advanced driving variables, such as the effects of city versus highway driving, the vehicle load, or other variables likely to cause non-uniform wear. The system could also aggregate and compare data from all brake sensors, comparing brake pad wear across all wheels to identify outliers which may be indicative of abnormalities and alerting the user of the wheels with potential faults. For example, a dragging brake will likely cause faster brake pad wear than the other brakes. 
     Information from the sensors as discussed above can be used in various contexts. Maintenance planning personnel can rely on the information for scheduling purposes. If the vehicle normally travels longer routes, brake pad replacement can be planned either before, or during a long trip based on the expected miles until brake pad failure. Information can also be provided to a fleet operator, as one of a larger group of indicators related to a trailer&#39;s road readiness. If the brake pads are likely to fail at some point during the expected truck route, the indicator can alert the fleet operator to this fact so that maintenance can be performed beforehand. 
     In should be understood all sensors described herein are configured for use in a VAN and as part of a system as described herein. In other embodiments, the sensor assemblies may utilize other contactless technology to determine the distance, such as optical devices, capacitive sensors, inductive sensors, sonar, radar and the like. Anisotropic magnetoresistance (AMR) and tunnel magnetoresistance (TMR) are also particularly well-suited for the subject technology because these methods consume little power in battery-based sensor assemblies. 
     As can be seen, the subject technology can be initially integrated into the brake structure or retrofit. In either case, the brake sensor is preferably not consumable. The brake sensor may have ample battery life to last for the life of the vehicle. 
     Referring now to  FIG. 21 , a schematic view of a vehicle area network (VAN)  2101  with integrated brake sensor assemblies  2110  is shown. The VAN  2101  is similar to that described above with respect to  FIG. 1  and similar numbers in the “2000s” are used to designate similar components, not all of which are described again in detail. The brake sensor assemblies  2110  are each coupled to a wheel  2111 . The VAN  2101  is in communication with a data repository  2121 . The data repository  2121  may be integral with the tractor  2102  and/or at an external remote device (e.g., a server) as depicted, which the VAN can communicate with through a telematics device or the like. 
     As noted above, the sensors  2110  can remain in use after brake pad replacement. However, upon initial installation or at a change of brake pads, the sensors  2110  will typically require calibration. Calibration establishes the baseline for all subsequent measurements and by which the remaining pad thickness is determined. In one embodiment, the sensors  2110  are capable of measuring a total span of 25 mm. Of that span, about 18 mm to 20 mm is the friction pad thickness. With a new pad, the sensors  2110  are ‘zeroed’ so that relative movement indicating wear can be subtracted from the pad thickness to result in the remaining thickness by the repository  2121 . Absolute position of the target element can be measured but relative position will be computed and recorded. Preferably, when new pads are installed or at the original commissioning, the sensors  2110  read close to zero absolute position to allow for the most useable measurement range over the life of the pad wear. If for example the data repository  2121  determines that the sensor absolute position is not within a predetermined tolerance with a new brake pad, the data repository can generate an out of tolerance ‘zero’ point indicating problems such as an incorrect sensor installation or that brake pads were installed with less than full-life thickness. 
     As the data repository  2121  receives information for the sensors  2110 , the data repository  2121  improves the utilization, performance, and safety of the vehicle. For example, the data repository  2121  can determine a minimum brake pad thickness for comparison to a predetermined threshold. As brake pad wear is typically gradual, warnings can be provided to schedule replacement. The service team can pre-program levels for the warnings and alerts so breaching any legal or manufacturer suggested minimums is avoided. In one embodiment, the tractor dashboard may display a ‘miles remaining’ indicator before brake pad replacement is needed which is based on rate of brake pad wear captured over certain distances over time. The ‘miles remaining’ indicator may also be sent to one or more smart devices (e.g., desktop computers, smart phones and the like). The data repository  2121  aggregates all the brake sensors  2110  to compare the performance of each brake to the others. Thus, abnormal wear can be determined to uncover potential problems like a dragging brake or unbalanced force differential wearing more quickly than others. 
     The data repository  2121  can also include information about the type of routes typically covered by a particular vehicle or company. For example, a 20 mile per trip would not need the same warnings and alerts for ‘miles to service’ as a 1500 mile trip. For a longer trip, a mid-trip service may even be scheduled into the delivery timetable. Although the sensor readings are real-time or near real-time, the measurements may be provided periodically to preserve sensor battery life. With such constant monitoring, the data repository  2121  can beneficially use statistical modeling and use averages to minimize false nuisance alerts. The continuous stream of data allows for an actual status check prior to any trip, which goes beyond just a visual inspection. 
     Additionally, brake wear may be an advanced insight of driver behavior. Expected brake pad compression given the brake pad pressure load or degree to which the brakes were applied (e.g., the brake pads will be expected to compress to different degrees if the user lightly taps the brakes versus if they slam on the brakes for an emergency stop). Notably, this requires some input data regarding the degree to which the brakes were applied during one or more braking events. The second sensor reading can then be compared to an expected second sensor reading and if there is a significant deviation. Whether a particular deviation is significant can be determined on a case by case basis or based on compiled data for past known deviations from that particular vehicle or from a number of vehicles. 
     The sensors  2110  can also include temperature sensors. The temperature sensors may be internal to the brake pad wear sensor and/or a separate probe connected to or near the brake wear sensor. The temperature probe can be wired to the brake wear sensor so that the temperature data can be combined with the brake data for transmission. The data can then be transmitted to the range extenders  2170 , and ultimately to the data repository  2121  and/or the tractor  2101  for display or generating a control command in an autonomous vehicle. 
     Temperature data is particularly insightful for brakes because brakes generate a significant amount of heat when operating properly and even more during heavy duty operation such as during steep downhill descents with a full load. Since brake pads lose some stopping power (coefficient of friction) as temperature rises, the driver can be warned to use the engine to slow the vehicle or the autonomous vehicle can make a similar adjustment. It is also possible for the brake pads to glaze and permanently degrade performance if temperatures are too high. Further, the heat generated by the brakes can result in damage to nearby components (e.g., ABS components) or in a more severe case, wheel end fires. By continuously monitoring temperature, warnings and proper action can be taken to avoid a reduction in braking potential that results in a longer required stopping distance. Still further, the data repository  2121  can generate alerts and/or change in drive control settings to avoid permanent damage to the brake pads and potentially the rotors due to excessive temperature. In the most extreme case, the data repository  2121  can warn of temperatures that could soon result in a wheel end fire due to ignition of the grease/oil or even the tire. In some cases, temperature sensors can also include ambient temperature sensors so that temperature sensor reading of the brake system can be normalized for ambient driving conditions. 
       FIG. 22A  is an exemplary graph  2200  of temperature in Celsius as measured by brake pad temperature sensors over cumulative driving time. When there is a significant spike in brake pad temperature, as indicated within block  2202  a processor, such as the wireless hub within the vehicle, can perform anomaly detection dependency modeling as shown in  FIG. 22B . 
     Referring now to  FIG. 22B , the anomaly detection dependency modeling graph  2204  compares the temperature measured by the brake pad temperature sensors, represented by graph line  2206 , to wheel end temperature tracked by wheel end temperature sensors at the respective wheel, represented by graph line  2208 . If there is a significant discrepancy in the graph lines  2206 ,  2008  that can be indicative of an anomaly, and an alert can be provided to indicate a potential fault condition with the brake pads of the respective wheel. Additionally or alternatively, spikes in brake pad temperature can be compared across different wheels with significant differences also being indicative of fault conditions, as discussed above. 
     All orientations and arrangements of the components shown herein are used by way of example only. Further, it will be appreciated by those of ordinary skill in the pertinent art that the functions of several elements may, in alternative embodiments, be carried out by fewer elements or a single element. Similarly, in some embodiments, any functional element may perform fewer, or different, operations than those described with respect to the illustrated embodiment. Also, functional elements shown as distinct for purposes of illustration may be incorporated within other functional elements in a particular implementation. 
     While the subject technology has been described with respect to preferred embodiments, those skilled in the art will readily appreciate that various changes and/or modifications can be made to the subject technology without departing from the spirit or scope of the subject technology. For example, each claim may depend from any or all claims in a multiple dependent manner even though such has not been originally claimed.