Patent Description:
Fasteners, such as screws, bolts, and studs, are used to form joints between objects. The objects are held together by tension created within the fastener. If the tension is released (e.g., if a nut on a stud loosens) the objects may separate and joint failure may result. In commercial trucking, for example, studs are used to join wheels, which include a wheel rim and one or more tires, to wheel hubs. Specifically, a wheel is positioned onto the studs of a hub, lug nuts are engaged with the studs, and the lug nuts are torqued down to secure the wheel to the hub. The process of applying torque to the nuts tensions the studs and causes the shanks or bodies of the studs to elongate slightly.

The torque applied to the lug nuts of a commercial truck, and the resulting tension in the studs, is important to providing a durable construct of the wheel and hub. If the tension is too low, the wheel may disconnect or progressive failures may occur such as wear of mating surfaces, wear of pilots of the hub, and/or stud fatigue. If the tension is too high, the studs of the hub may yield and/or break. Further, excessive stud tension may result in undesirable stress in the hub.

The tension in the studs of a commercial vehicle hub may be too high or too low due to the initial torque applied when installing the wheel onto the hub. In other situations, the tension in the studs may change over time despite the lug nuts tightened down with the appropriate amount of torque. There are numerous environmental factors that may cause the tension in the studs to release over time including, for example, vibration, impact, and temperature change.

Stud tension indicating systems are available that permit a driver fleet operator to monitor stud tension. For example, in the case of heavy-duty truck wheel-ends, some systems include nut rotation indicators that permit a driver to visually identify changes in the rotational orientation of the nuts of a wheel hub which would indicate a loss of stud tension. More specifically, if any of the nuts on the wheel loosens, the nut rotation indicator will become noticeably out of alignment with the other nut rotation indictors on the wheel. The driver is thereby alerted to a potential loss in tension in the stud due to the loosened nut on the stud. However, these nut rotation indicators are unable to provide a driver or fleet operator with real-time tension information during operation of the vehicle. These nut rotation indicators do not indicate a specific value of tension. Further, these nut rotation indicators are unable to alert a driver if a stud of the wheel hub has yielded and has begun to deform plastically, which may occur due to over-tightening of the associated nut. <CIT> discloses a lug stud and lug nut monitoring system, method, and components therefor. <CIT> discloses a wheel bolt with a reporting function. <CIT> discloses a nut, in particular a wheel or axle nut, washer, and a control device for wheel or axle nuts in vehicles and a vehicle provided therewith. <CIT> discloses a wheel hub. <CIT> discloses a load sensing system including RFID tagged fasteners. <CIT> discloses load indicating fastener systems, methods and apparatus. <CIT> discloses a smart stud-nut assembly.

In accordance with one aspect of the present invention, there is provided a wheel end monitoring apparatus for a vehicle as recited in claim <NUM>. The wheel end monitoring apparatus may facilitate real-time monitoring of the clamped wheel hub and the wheel rim by an in-vehicle system and/or a remote cloud-based computing system while the wheel hub and wheel rim are at rest or rotating during operation of the vehicle.

Further, the external device may include a gateway of the vehicle. The wireless communication from the communication circuitry to the external device may be a short-range wireless communication that requires a limited power consumption. The gateway may be connected to an electrical system of the vehicle and utilize electrical power from the vehicle to power a long-range wireless communication to a wide area wireless network, such as a cellular phone network. The gateway thereby permits the power provided by the power source to be minimized by receiving the data from the communication circuitry via a short-range wireless signal and transmitting the data to the wide area wireless network using power from the vehicle.

In one embodiment, the power source is configured to harvest power from rotation of the wheel hub. For example, the vehicle spindle may have magnets mounted thereto and the power source includes a coil mounted on the wheel hub that rotates through magnetic fields of the magnets as the wheel hub rotates around the vehicle spindle. The changing magnetic fields acting on the coil induces electrical energy to flow in the coil. The power source may include a battery for storing harvested electrical energy and a power supply circuit that supplies power to the sensor and communication circuitry. The power source thereby provides a source of electrical power on-board the wheel hub for use by the at least one sensor and the communication circuitry.

A fastener is also provided, as recited in claim <NUM>, that includes a fastener housing having a head and a body. The body of the fastener housing elongates upon tension of the body. The fastener housing has an internal compartment and a displacement member in the internal compartment. The displacement member shifts upon tensioning of the body. The fastener further includes a capacitive sensor in the internal compartment configured to detect a capacitance between the capacitive sensor and the displacement member. The capacitance changes as the displacement member shifts with tensioning of the body. The fastener further includes communication circuitry operably coupled to the capacitive sensor and configured to communicate data associated with the capacitance to a remote device. The fastener may be used in a variety of applications, such as a stud of a wheel hub, a fastener used to secure a brake rotor to a wheel hub, or a fastener used to connect a drive axle to a wheel hub.

In accordance with one aspect of the present invention, a fastener monitoring apparatus is provided that allows for the digital determination of one or more properties of one or more fasteners of a joint between, for example, a wheel hub and a wheel, as well as the ability to deliver data regarding the one or more fastener properties wirelessly to a user. The one or more fastener properties may include, for example, tension, strain, torque, and/or length. The fastener monitoring apparatus may simplify pre-trip inspections as well as installation quality verification.

The fastener monitoring apparatus may utilize the one or more properties of the one or more fasteners to determine, or facilitate a determination by a remote computer, a current or predicted failure mechanism of the construct of the wheel and the wheel hub. For example, the fastener monitoring apparatus may detect a yielded stud failure mode wherein the material of a stud has yielded due to the stud stretching too far. As another example, the fastener monitoring apparatus may detect an under-tensioned or over-tensioned stud and provide an early warning system for wheel-offs, progressive failures of the fasteners, broken fasteners, and high hub stress. The fastener monitoring apparatus permits determination of one or more properties of the fastener at the associated vehicle or remotely, including during operation of the vehicle, thus improving maintenance planning and helping to avoid unplanned downtime.

In one embodiment, the fastener monitoring apparatus includes a stud with embedded electronics designed to measure the tension on the stud. Such measurements may be communicated wirelessly to a local device, such as a handheld device or vehicle electronic control unit (ECU), or to a remote computer. This communication may be direct, indirectly via a local mesh network, and/or indirectly over a wide area network as some examples.

In one embodiment, the fastener monitoring apparatus includes a plurality of studs of a wheel hub of a commercial truck and may communicate with the vehicle driver and/or the fleet manager through one or more other devices. For example, the studs may replace traditional wheel studs in class <NUM> vehicles, or in any private or fleet truck. In other embodiments, the fastener monitoring apparatus may be utilized in place of traditional fasteners in a variety of applications. For example, the fastener monitoring apparatus may be utilized with heavy equipment, power generation and distribution equipment, wind turbine equipment, and/or mining equipment. The fastener monitoring apparatus may also be utilized in different components of a commercial vehicle, such as studs used to connect a brake rotor to a wheel hub and/or studs used to connect a drive axle to a wheel hub.

In one method of utilizing the fastener monitoring apparatus, a driver receives an alert if the tension of any monitored fastener of the vehicle is beyond a specified threshold. For example, the tension in a stud may be beyond a lower threshold when a nut of the stud has loosened. As another example, the tension in the stud may be beyond an upper threshold when the tension approaches a tension that may cause the stud to yield. The driver may then take action to correct the problem, e.g. using a wrench to apply torque to the nut associated with the stud. Alternatively, the fasteners of a vehicle may be queried on-demand to provide tension data as requested by an external system, a driver and/or a fleet mechanic.

In one embodiment, the fastener monitoring apparatus includes a wheel stud that measures, digitizes, and transmits data regarding elongation of a body of the stud. The stud includes a displacement pin within the stud body and having a lower end portion fixed to the stud body. Prior to wheel installation, the displacement pin is at a predetermined depth in the stud. For example, the displacement pin may be in direct contact with or adjacent to a printed circuit board located in a head of the stud. The stud body includes threads onto which a nut is threaded. In one embodiment, a flange of a wheel hub and a portion of the wheel rim are clamped between the stud head and a nut threadingly engaged with the stud body.

As the nut is torqued onto the stud body, the stud body stretches elastically until the nut reaches a predetermined torque and the stud is subjected to an associated tension. This tension elongates the stud body based on the elastic modulus of the material of the stud body. Because the lower end portion of the displacement pin is fixed to the stud body, the elongation of the stud body shifts the displacement pin within the stud body away from the printed circuit board a distance proportional to the applied torque. This separation creates or enlarges a gap between an upper capacitor plate portion of the printed circuit board and a lower capacitor plate portion of the displacement pin. The capacitance C between the upper capacitor plate portion and the lower capacitor plate portion may be estimated using the general parallel plate capacitance equation:
<MAT>.

Wherein ε is the permittivity of the dielectric between the two plates, A is the area of the upper and lower capacitor plate portions, and d is the distance between the upper and lower capacitor plate portions. Air is one medium that may be used for capacitance measurement. Other mediums may include other dielectrics or combinations of dielectrics.

The change in capacitance corresponding to the change in air gap is used to determine the change in distance between the upper and lower capacitor plate portions. This change of distance corresponds to an elongation or change in length of the stud body. A processor, which may be a component of or external to the stud, may thereby determine the strain in the stud by dividing the change in length of the stud body by the length of the stud body. The processor may further determine the tension in the stud using the determined strain, Young's modulus of the stud material, and cross-sectional area of the stud. As one example, the processor may utilize a look-up table containing experimentally derived strain values for different materials and sizes of studs as well as associated capacitance values. Thus, for a given type of stud and detected capacitance, the processor may look up and/or interpolate the strain from the table.

As another example, the following general capacitance equation may be used to convert detected capacitance to a tension value:
<MAT>.

The general capacitance equation (<NUM>) may be rearranged to solve for the distance between the plates:
<MAT>.

The Young's modulus of the stud material, E is defined as,
<MAT>
<MAT>
where,.

The change in length of the stud produces a change in gap at the capacitor plates. Assuming zero initial gap, Δl = d. Substituting and re-arranging the Young's modulus equation results in:
<MAT>.

The tension in the stud is given by:
<MAT>.

Substituting for d from the general capacitance equation (<NUM>) above, the tension (F) in the stud may be determined using the following equation:
<MAT>.

Rearranging the equation results in the following equation that may be used to obtain a tension value from the detected capacitance:
<MAT>.

The term in brackets in equation (<NUM>) may be a constant for a given application. Thus, the tension value in the stud may be determined based on a detected capacitance and the physical characteristics of the stud.

In one embodiment, the printed circuit board is configured to detect and digitize the change in capacitance across the air gap (or other dielectric(s) between the upper and lower capacitor plate portions) generated by stud stretch. Changes in the stud tension and the resultant air gap between capacitor plate portions of the printed circuit board and displacement pin are captured as changes in electronic capacitance. This data reading can then be transmitted from the stud to a client, cloud, or end user via communication circuitry of the stud.

With reference to <FIG>, a wheel hub <NUM> is illustrated and includes components for connecting a wheel rim to a spindle of a vehicle. The wheel hub <NUM> may include a wheel hub body 100A, studs <NUM>, a spindle nut 100B, roller bearing assemblies 100C, and a spacer 100D. The roller bearing assemblies 100C may each include an inner race, an outer race, and roller bearings that roll along the inner and outer races with rotation of the wheel hub <NUM>.

The wheel hub <NUM> is configured to receive a wheel and join the wheel to the wheel hub using studs <NUM>. The studs <NUM> each have a head portion, such as head <NUM> and a shank or body portion, such as stud body <NUM>. A wheel is placed onto the studs <NUM> and fastened in place by screwing a nut onto each of the stud bodies <NUM> until the wheel is secured tightly in place between the nut and a front surface <NUM> of a mounting portion, such as a flange <NUM>, of the wheel hub <NUM>.

<FIG> illustrates one such stud <NUM>. The stud <NUM> has a stud housing <NUM> including the head <NUM> and the stud body <NUM>. When a nut <NUM> is tightened onto the body <NUM> of the stud <NUM>, the body <NUM> has a deformable portion <NUM> that extends along an axis <NUM> between the head <NUM> and the nut <NUM>. The stud <NUM> includes a sensor <NUM> configured to detect one or more properties of the stud <NUM>, such as stress, strain, torque, and/or length. The sensor <NUM> may include a variety of transducers, such as at least one of a capacitive sensor, a strain gauge, an inductive sensor, a hall effect sensor, an electrical transducer, and an optical sensor. All of the studs <NUM> may include sensors <NUM>, or fewer than all of the studs <NUM> may include sensors <NUM>.

For example, the sensor <NUM> may detect the distance that the stud <NUM>, and in particular the stud body <NUM> thereof, elongates by measuring the capacitance associated with an air gap <NUM> (see <FIG>) that is caused by elongation of the study body <NUM>. The stud <NUM> further includes a printed circuit board <NUM> and a displacement member, such as a displacement pin <NUM>, to measure how far the stud <NUM> has stretched. The displacement pin <NUM> has a distal or lower end portion <NUM> fixed to the stud body <NUM>. The axial size of the air gap <NUM> between the printed circuit board <NUM> and the displacement pin <NUM> is measured to determine the axial elongation of the stud body <NUM>. The displacement pin <NUM> includes a proximal, upper head portion <NUM> with a lower capacitor plate portion <NUM> adjacent the printed circuit board <NUM> that interacts with a capacitor plate portion (e.g. capacitor plate portion <NUM> in <FIG>) of the printed circuit board <NUM> to form a capacitor <NUM>. Thus, as the stud body <NUM> of the stud <NUM> stretches, the displacement pin <NUM> shifts axially away from the printed circuit board <NUM> and the axial length of the air gap <NUM> is increased. When no tension is applied to the stud <NUM>, the displacement pin <NUM> may be configured to touch or be closely adjacent to the printed circuit board <NUM>. The displacement pin <NUM> may be made of, for example, mild steel, the stud <NUM> may be made of, for example, cold rolled steel, and the nut <NUM> may be made of, for example, forged steel. It should be appreciated that other materials may be used to form the displacement pin <NUM>, the stud <NUM>, and the nut <NUM>. Nothing is this disclosure should be taken to limit these structures to only the materials discussed above.

As illustrated in <FIG>, the printed circuit board <NUM> may be embodied as the printed circuit board <NUM> or the printed circuit board <NUM>. The printed circuit board <NUM> includes, for example, a processor <NUM> coupled to a memory <NUM>, a capacitive sensor <NUM>, and communication circuitry <NUM>. One or more of the aforementioned components are also coupled to the battery <NUM>. The capacitive sensor <NUM> may, for example, convert a measured capacitance to a corresponding electric voltage level indicative of the distance between the displacement pin <NUM> and the capacitive sensor <NUM>. The capacitive sensor <NUM> may then communicate the voltage level to at least one of the processor <NUM> and the communication circuitry <NUM>. As will be described in more detail below, the processor <NUM> may further process the received voltage level and/or store the voltage level in the memory <NUM>. After processing the voltage level, the processor <NUM> may transmit voltage level data such as the voltage level itself and/or information based on the voltage level (e.g., strain, stress, and/or alerts) via the communication circuitry <NUM>. The communication circuitry <NUM> may be configured to send and receive data based on one or more communication protocols such as Bluetooth®, Zigbee, Z-wave, 6LowPAN, Thread, WiFi, and/or LoRaWAN as some examples.

The electrical circuit of the printed circuit board <NUM> may be completed entirely within the printed circuit board <NUM>. This approach may reduce electrical interference for the stud <NUM>. In another embodiment, the electrical circuit of the printed circuit board <NUM> may include the head <NUM> and/or body <NUM> of the stud <NUM>.

The printed circuit board <NUM> includes, for example, a capacitive sensor <NUM> coupled to a memory <NUM> and communication circuitry <NUM>. One or more of the aforementioned components are also coupled to the battery <NUM>. The printed circuit board <NUM> is similar to the printed circuit board <NUM> except there is no separate processor on the printed circuit board <NUM> and the capacitive sensor <NUM> includes an integrated processor for processing the voltage level data.

Regarding <FIG>, the printed circuit boards <NUM>, <NUM>, <NUM> may each have one of the configurations of printed circuit boards <NUM>, <NUM>, <NUM>. In <FIG>, the printed circuit board <NUM> includes a ground plane <NUM>, a power plane <NUM>, and an upper capacitor plate portion <NUM>. The capacitor sensor <NUM> and the other circuitry <NUM>, which includes, for example, communication circuitry <NUM> and processor <NUM>, may be mounted to the printed circuit board <NUM>. The capacitive sensor <NUM> and the other circuitry <NUM> may be connected to both the ground plane <NUM> and the power plane <NUM>. The battery <NUM> may couple between the power and ground planes <NUM>, <NUM>. The battery <NUM> may also connect directly to the upper capacitor plate portion <NUM> of the capacitive sensor <NUM> directly, or indirectly through the power plane <NUM>. In one embodiment, the capacitive sensor <NUM> includes a connector <NUM> that connects the upper capacitor plate portion <NUM> to one or more other components of the capacitor sensor <NUM> to allow the capacitive sensor <NUM> to measure the capacitance between the upper capacitor plate portion <NUM> and the lower capacitor plate portion <NUM>.

Regarding <FIG>, the lower capacitor plate portion <NUM> of the displacement pin <NUM> forms a lower capacitor plate that interacts with the upper capacitor plate portion <NUM>. The surface of the lower capacitor plate portion <NUM> may be generally circular. The displacement pin <NUM> tapers down to a cylindrical shaft <NUM> that includes the end portion <NUM> embedded in the stud body <NUM>. The end portion <NUM> of the displacement pin <NUM> may be attached to the stud body <NUM> via a press fit engagement, a weld, adhesive, and/or fastener (e.g., a transverse pin) in an inner compartment <NUM> of the stud <NUM>. In one embodiment, the inner compartment <NUM> includes a blind bore formed in the stud <NUM>. The head <NUM> and the body <NUM> of the stud may be two components that are joined together, such as by welding, or may have a unitary, one-piece construction. The head <NUM> may include a head portion <NUM> of the inner compartment <NUM> and the body <NUM> may include a body portion <NUM> of the inner compartment <NUM>. The head portion <NUM> may have a larger inner diameter than the inner diameter of body portion <NUM>. The head <NUM> may include a tapered surface, such as a frustoconical surface <NUM>, that provides clearance for the underside of the displacement pin head portion <NUM> as the displacement pin head portion <NUM> shifts axially away from the printed circuit board <NUM> with elongation of the stud body <NUM>. In another embodiment, the displacement pin <NUM> includes a uniform width throughout and does not include the head portion <NUM>.

Turning to <FIG>, the printed circuit board <NUM> is similar to printed circuit board <NUM> except that the printed circuit board <NUM> includes a battery <NUM> and a battery <NUM>. The battery <NUM> and the other circuitry <NUM> are connected to the power plane <NUM> of the printed circuit board <NUM>. The upper capacitor plate portion <NUM> of the capacitor sensor <NUM> is connected to the battery <NUM>. The capacitor sensor <NUM> including the connector <NUM> and upper capacitor plate portion <NUM> therefore receive electrical power from a different battery (battery <NUM>) than the other circuitry <NUM> (battery <NUM>). These parallel power sources may reduce noise in the capacitive measurement.

Turning to <FIG>, like numbered structures in printed circuit board <NUM> are identical to the structures described with respect to <FIG>. Specifically, the printed circuit board <NUM> includes a capacitive sensor <NUM>, other circuitry <NUM>, power plane <NUM>, connector <NUM>, and upper capacitor plate portion <NUM>. The printed circuit board <NUM> may connect to batteries in either of the approaches described with respect to <FIG> further includes an electrical isolation plane <NUM> to isolate the components above the isolation plane <NUM> from any noise created by the components below the isolation plane and vice versa. The connector <NUM> extends through the isolation plane <NUM>.

In some embodiments, the upper capacitor plate portion <NUM>, <NUM>, <NUM> is formed on the bottom surface of the printed circuit board <NUM>, <NUM>, <NUM> near the associated displacement pin <NUM>. The shape of the upper capacitor plate <NUM>, <NUM>, <NUM> corresponds to the shape of the lower capacitor plate portion <NUM> of the displacement pin <NUM> near the printed circuit board <NUM>, <NUM>, <NUM>. For example, the upper capacitor plate portion <NUM>, <NUM>, <NUM> and the lower capacitor plate portion <NUM> may each have planar confronting surfaces, or the confronting surfaces may be concave/convex.

Regarding <FIG>, a system <NUM> is provided implementing studs <NUM>. Each of the wheels 910A, 910B, and 910C have a wheel rim <NUM> with one or more tires <NUM>. The wheel rim <NUM> is joined to a wheel hub of the tractor <NUM> using studs <NUM> of the wheel hub. The studs <NUM> may communicate with an external device such as a gateway <NUM>. The gateway may include a processor <NUM> and communication circuitry <NUM>. In one embodiment, the gateway <NUM> includes a local server and computer <NUM> of the tractor <NUM>. The studs <NUM> may communicate either directly or indirectly, such as via one or more of the other studs <NUM> or other ECUs of the tractor <NUM>. For example, the communication may take place according to a mesh network topology.

The studs <NUM> may rotate with the wheel hubs of the tractor <NUM> and wirelessly transmit data to the gateway <NUM> which is stationary relative to the tractor <NUM>. The communication circuitry of the studs <NUM> may utilize short-range communication protocols, such as Bluetooth, Bluetooth Low Energy, and Zigbee, to communicate with the gateway <NUM> while minimizing energy consumption. The gateway <NUM> may communicate with a cloud-based computing network via a wide area network such as cellular (e,g. , <NUM>, <NUM>, <NUM> LTE, <NUM>), WiMax, or LoRaWAN networks as some examples. The gateway <NUM> may receive electrical power from the electrical system of the tractor <NUM> so that the long-range communications from the gateway <NUM> to the network may be performed continuously and/or intermittently as needed for a particular situation. The use of gateway <NUM> to perform long-range communications preserves the battery life of the studs <NUM> or, if the studs <NUM> utilize an inductive energy charging system, reduce the energy requirements of the studs <NUM>.

The local server and communication computer <NUM> may be configured to receive one or samples or other data such as a warning from the studs <NUM>. The local server and communication computer <NUM> may display or otherwise notify the user of one or more properties of the studs <NUM>, such as tension, of any of the studs <NUM>. For example, the local server and communication computer <NUM> may be coupled to a human-machine interface (HMI) <NUM> and provide stud tension information via a GUI and/or speaker.

Records related to one or more of the studs <NUM> may be stored in a local maintenance database <NUM>. The local server and communication computer <NUM> may also communicate any or all of the data from the studs <NUM> to a remote server computer <NUM> via network <NUM> where the data may be processed or stored in a remote maintenance database <NUM>. The remote server computer <NUM> may include a processor <NUM> and a communication interface <NUM>. The network <NUM> may include, for example, a cellular network and the internet. The remote server computer <NUM> may transmit data such as current tension and/or a warning regarding any of the studs <NUM>, to the local server and communication computer <NUM>. The local server and communication computer <NUM> may notify a user, including, for example, the driver, about a condition or status of any of the studs <NUM>. Though this exemplary system illustrates the tractor <NUM> as an example, it should be appreciated that this system may be implemented in any class of vehicle or in any machine where monitoring of fastener tension is desired.

The studs <NUM> may include a processor, such as processor <NUM>, or a capacitive sensor, such as capacitive sensors <NUM>, <NUM>, operable to sample one or more properties of the stud body <NUM> via a capacitive sensing module and transmit the sampled data (e.g. tension, distance, strain) via a communication interface, such as communication circuitry <NUM>, <NUM>, at regular intervals. The capacitance detected by the capacitive sensor may be determined according to, for example, a parallel plate equation. The sampling interval and the transmission interval need not be the same. For example, the sampling interval may be more frequent than the transmission interval and, during a given transmission, multiple samples may be sent as a batch. In other embodiments, the processor may average or otherwise statistically process the samples prior to sending the processed data during a given transmission to reduce the size of the data being transmitted and reduce power usage.

The studs <NUM> may include a processor, such as processor <NUM>, or a capacitive sensor, such as capacitive sensors <NUM>, <NUM>, operable to increase inspection frequency for increased immediate and short-term accuracy. For example, if the detected tension in the stud <NUM> is changing rapidly or goes above/below an upper/lower threshold, then the processor <NUM> may increase the rate at which the processor <NUM> samples the capacitance between the printed circuit board <NUM> and the displacement pin <NUM>. In such cases, the stud <NUM> may also increase the rate at which data is transmitted via the communication circuitry <NUM>. If the tension in the stud <NUM> beings changing less rapidly, the stud <NUM> may decrease the sampling and transmission intervals. Furthermore, if the tension in the stud <NUM> varies within a given range centered on the ideal tension for a given application, the stud <NUM> may ignore (i.e., not change the sampling interval) these changes in tension because the processor <NUM> recognizes that variation are normal for a given application. For example, if the samples are normally distributed and all of the samples of within an acceptable statistically variance from the mean, the changes in tension may not cause the processor to adjust the sampling rate.

The stud <NUM> may be programmed to transmit an indication that an appropriate tension has been achieved. For example, when a processor determines that the appropriate tension has achieved, the communication circuitry of the stud <NUM> may transmit a notification to an external device that the appropriate tension has been achieved. For example, the stud <NUM> may communicate a "proper torque achieved" message to a maintenance worker's portable electronic device when the maintenance worker has torqued a nut on the stud <NUM> to the correct torque. In some embodiments, the stud <NUM> may be configured to automatically pair with a tool for creating tension (e.g. by applying torque to nut <NUM>) and send a communication to the tool when the appropriate tension is achieved. That communication may cause the tool to stop applying torque to the nut <NUM>.

The sampling and transmission rates of the stud <NUM> may be controlled by external devices via the communication circuitry of the stud <NUM>. For example, an external device may wirelessly couple to the studs <NUM> and cause the studs <NUM> to sample the tension on the studs <NUM>. The studs <NUM> may then report measurements to the external device individually, through a mesh network topography, or through a combination of the two based on power constraints. For example, in the case of a pre-trip inspection, the user of an external device, such as a smartphone, tablet computer, laptop computer, or desktop computer may initiate a pre-trip inspection of vehicle. The external device may cause a signal to be generated that when received by the studs <NUM> causes the studs <NUM> to sample the tension thereof. This reporting saves time during pre-trip inspection and reduces delay.

In the event a sampled tension in the stud <NUM> crosses an emergency threshold, an emergency report may be sent to a user indicating that immediate action is needed. The stud <NUM> may first attempt communication using its lowest power mode of communication. The stud <NUM> will increase the power level of communications to the maximum capability thereof until receipt of the emergency communication is acknowledged. The stud <NUM> may, for example, wait for acknowledgement of receipt of the emergency communication by the local server and communication computer <NUM> before the stud <NUM> stops transmitting the emergency communication.

The stud <NUM> may normally operate in a low-power mode unless the tension in the stud <NUM> crosses the emergency threshold. For example, the processor <NUM> may include a primary processor and a secondary processor. The secondary processor determines tension in the stud <NUM> at predetermined or random intervals. If the tension crosses the emergency threshold, the secondary processor wakes up the primary processor and the primary processor operates the communication circuitry <NUM> to send the emergency communication.

Regarding <FIG> and <FIG>, another stud <NUM> is provided that is similar in many respects to the stud <NUM> discussed above. The stud <NUM> includes a stud housing <NUM> having a head <NUM> and a stud body <NUM>. The stud housing <NUM> includes an inner compartment <NUM> that receives a displacement pin <NUM> and circuitry <NUM>. The head <NUM> has an upper opening <NUM> (see <FIG>) and a closure member, such as a cap <NUM>, secured to the head <NUM> to close the upper opening <NUM>. In one embodiment, the cap <NUM> is an overmold made of epoxy or another material selected to form a suitable seal.

The circuitry <NUM> includes a sensor circuit board <NUM> having a capacitive sensor that interacts with a head <NUM> of the displacement pin <NUM>. When the stud <NUM> is not under tension, the head <NUM> may contact a dielectric-coated electrode of the sensor circuit board <NUM>. When the stud <NUM> is placed in tension, the head <NUM> may shift away from the electrode of the sensor circuit board <NUM>.

The circuitry <NUM> further includes a power source, such as a battery <NUM>. In one embodiment, the battery <NUM> includes one or more coin cells. The circuitry <NUM> further includes a data transfer circuit board <NUM> that includes communication circuitry. The battery <NUM> is sandwiched between the sensor circuit board <NUM> and the data transfer circuit board <NUM>. The sensor circuit board <NUM> and the data transfer circuit board <NUM> have one or more electrical contacts that form a circuit with the battery <NUM> and permit the battery <NUM> to power the sensor circuit board <NUM> and the data transfer circuit board <NUM>. In another embodiment, the power source of the stud <NUM> may include coils configured to receive electrical power from an inductive power source mounted on the associated vehicle hub.

With reference to <FIG>, the displacement pin <NUM> includes a shaft <NUM> having a distal, lower end portion <NUM> secured to the stud housing <NUM> such as via an epoxy or adhesive <NUM>. Regarding <FIG>, with the stud <NUM> assembled, the head <NUM> of the displacement pin <NUM> includes a lower capacitor plate portion <NUM> adjacent an upper capacitor plate portion <NUM><NUM> of the sensor circuit board <NUM>.

Regarding <FIG>, a wheel hub <NUM> is provided that includes studs <NUM> similar to the studs <NUM> discussed above. Each stud <NUM> includes a sensor configured to detect, for example, tension in the stud <NUM>. The studs <NUM> receive power from a power source <NUM>, such as a battery, an inductive power source, and/or a solar power source. The wheel hub <NUM> includes communication circuitry <NUM> configured to communicate data from the studs <NUM> to a device external to the wheel hub <NUM> such as a gateway mounted on the vehicle. The communication circuitry <NUM> may include a processor that performs pre-processing on the data before the data is communicated to the external device. In some embodiments, the wheel hub <NUM> includes a processor operably coupled to the communication circuitry <NUM> and the studs <NUM>, the processor performing operations on signals from the studs <NUM> and operating the communication circuitry <NUM>. In some embodiments, the communication circuitry <NUM> may be capable of receiving communications from the gateway.

Regarding <FIG>, a wheel hub <NUM> is provided that includes studs <NUM> each having a sensor 1301A, communication circuitry 1301B, and an integral power source 1301C such as battery. The wheel hub <NUM> further includes conventional studs <NUM>. The wheel hub <NUM> includes a power source <NUM>. In one embodiment, the power source <NUM> includes a non-rechargeable battery. In another embodiment the power source <NUM> that harvests energy from the rotation of the wheel hub <NUM> and provides electrical energy to a battery of the power source <NUM>. The wheel hub <NUM> includes a processor <NUM> in communication with one or more peripheral sensors <NUM> of the wheel hub <NUM> such as a temperature, vibration, speed, and/or acceleration. The wheel hub <NUM> further includes central communication circuitry <NUM> that is operably coupled to the power source <NUM> and the processor <NUM>. The central communication circuitry <NUM> may receive wireless communications from the communication circuitry 1301B of the studs <NUM> and the processor <NUM> controls the communication circuitry <NUM> to communicate data from the studs <NUM> wirelessly to an external device, such as a vehicle gateway. The central communication circuitry <NUM> may thereby operate as a powered repeater that utilizes harvested electrical power such that the signal strength utilized by the communication circuitry 1301B of the studs <NUM> may be minimized to maximize the lifespan of the battery of the power sources 1301C of the studs <NUM>.

Claim 1:
A wheel end monitoring apparatus for a vehicle, the wheel end monitoring apparatus comprising:
a wheel hub (<NUM>, <NUM>, <NUM>) having a mounting portion;
a plurality of studs (<NUM>, <NUM>, <NUM>, <NUM>) of the wheel hub projecting from the mounting portion to mount a wheel rim to the wheel hub;
nuts of the wheel hub configured to threadingly engage the studs (<NUM>, <NUM>, <NUM>, <NUM>) and clamp the wheel rim and wheel hub mounting portion together;
a power source (<NUM>, 1301C, <NUM>) of the wheel hub and rotatable therewith;
sensors of the studs (<NUM>, <NUM>, <NUM>, <NUM>) operably coupled to the power source (<NUM>, 1301C, <NUM>), the sensors configured to detect at least one property of the studs (<NUM>, <NUM>, <NUM>, <NUM>) indicative of the clamping of the wheel rim and wheel hub;
communication circuitry (<NUM>, 1301B, <NUM>) of the wheel hub operably coupled to the power source (<NUM>, 1301C, <NUM>) and sensors, the communication circuitry (<NUM>, 1301B, <NUM>) configured to communicate data associated with the at least one property to an external device;
characterised in that the mounting portion includes a flange (<NUM>);
wherein the studs (<NUM>, <NUM>, <NUM>, <NUM>) include heads (<NUM>) secured to the flange (<NUM>) and bodies projecting from the flange (<NUM>); and
wherein the sensors include capacitive sensors (<NUM>, <NUM>, <NUM>, <NUM>) in the stud heads (<NUM>) and the studs (<NUM>, <NUM>, <NUM>, <NUM>) include displacement members in the stud bodies (<NUM>) that shift relative to the capacitive sensors (<NUM>, <NUM>, <NUM>, <NUM>) upon clamping of the wheel hub mounting portion and the wheel rim, the capacitive sensors (<NUM>, <NUM>, <NUM>, <NUM>) detecting the at least one property based upon capacitance between the capacitive sensors (<NUM>, <NUM>, <NUM>, <NUM>) and the displacement members.