VEHICLE SENSING SYSTEM WITH AT LEAST TWO SENSORS

A sensing system for a vehicle includes an electrical sensing circuit that has a first sensor and a second sensor. The sensing circuit is configured to provide a composite output signal that includes data from both the first sensor and second sensor.

TECHNICAL FIELD

The present disclosure relates generally to a vehicle sensing system that provides signal data from at least two sensors.

BACKGROUND

Vehicle electronic control modules (ECMs) can communicate vehicle sensor data to one another via a number of interfaces. For example, a communication bus may couple two or more ECMs, and each ECM may transmit addressed packets of sensor data onto the bus which can travel the bus allowing another ECM to identify the packet having its address. Another example of an ECM-to-ECM interface is a cable harness having connectors at opposing ends. For example, two ECMs may be coupled to one another via the cable harness connectors. The harness may have a plurality of discrete wires connected to each of the connectors for transmitting different types of sensor data. However, both communication buses and cable harnesses require relatively large spatial requirements. In implementations where spatial constraints are relatively small, these interfaces may not be feasible. Thus, there is a need for a smaller interface that is capable of transmitting signal data from multiple sensors.

SUMMARY

In at least some implementations, a sensing system for a vehicle includes an electrical sensing circuit that has a first sensor and a second sensor. The sensing circuit is configured to provide a composite output signal that includes data from both the first sensor and second sensor.

In other implementations, a sensing system for a vehicle includes an electrical sensing circuit that includes a speed circuit having a speed sensor and a temperature circuit having a temperature sensor. The sensing circuit is configured to provide a composite output signal that includes superimposed data received from the speed and temperature circuits.

DETAILED DESCRIPTION

Referring in more detail to the drawings,FIG. 1illustrates a schematic diagram of a drive train assembly10for an all-wheel drive (AWD) vehicle. The assembly10includes an engine12, a transmission14coupled to the engine12, a front differential assembly18coupled to the transmission14, a power transfer unit (PTU)20coupled to both the front differential assembly18and a proximal end of a propshaft24, and a rear differential assembly26coupled to a distal end of the propshaft24. Front drive shafts30,32couple respectively the front differential assembly18to front wheels34,36; similarly, rear drive shafts38,40couple respectively the rear differential assembly26to rear wheels42,44. In AWD vehicles, the PTU20selectively may transfer torque to the rear wheels42,44via the propshaft24(e.g., automatically or in response to a user selection). And when torque is not being transferred to the rear wheels42,44, the propshaft24is disconnected or otherwise not actively coupled or being driven. This torque transfer may occur via a gearing system46(shown inFIG. 2and which is described in more detail below). In at least one embodiment, it is desirable to measure the rotational speed and/or temperature of at least one component of the gearing system46.

FIG. 2schematically illustrates a few components of an exemplary PTU gearing system46. For example, the illustrated PTU includes a primary gear50coaxially coupled to the drive shaft32, a transfer shaft52carrying a secondary gear54that is engaged with the primary gear50and a ring and pinion assembly56that is coupled to the propshaft24. More particularly, the assembly56comprises a ring gear58coupled to the transfer shaft52and a pinion gear60coupled to the propshaft24. In the illustrated embodiment, the drive shaft32spans through the PTU20and engages the front differential assembly18.

In operation, torque is transmitted through the engine12into the transmission14. Then, torque is transmitted from the transmission14into the front differential assembly18, and then the torque is split between the front drive shafts30,32. The torque transmitted to drive shaft32rotates the primary gear50which in turn rotates and drives the transfer shaft52via secondary gear54(e.g., at a different angular speed). The driven transfer shaft52drives the ring gear58, which in turn, drives the pinion gear60—causing the propshaft24to rotate, thereby transferring power to the rear differential assembly26(shown inFIG. 1).

Returning toFIG. 1, the illustrated PTU20further includes a fluid reservoir70(e.g., a sump or pan). And in at least one implementation, it is desirable to measure the temperature of the PTU reservoir70or the fluid therein—e.g., in addition to measuring a rotational speed associated with the gearing system46.

FIG. 1also illustrates a sensing system72capable of measuring the rotational speed and temperature of any suitable gears or gearing system—including, but not limited to, the gearing system46. The sensing system72includes an electronic control unit (ECU)74coupled to a sensing circuit76via a communication link78. The sensing circuit76comprises at least two sensors80,82—e.g., a speed sensor and a temperature sensor. In the embodiments described below, the sensing circuit76receives sensor data (from sensors80,82), configures an electrical signal output that includes both speed and temperature information, and provides that electrical signal output to the ECU74via the communication link78. The ECU74is configured to receive the electrical signal and then extract or otherwise determine the speed and temperature data from the signal. Thereafter, among other things, the ECU74may use this data to control one or more vehicle systems, provide this data to other vehicle systems, alert a vehicle user based on the data, or any combination thereof. It should be appreciated that while the embodiments herein are described with respect to the PTU gearing system46and PTU reservoir70, these are merely examples to illustrate the operation of the sensing system72. Other implementations are possible—e.g., sensors80,82may measure other parameters (non-limiting examples include pressure, acceleration, fluid level or volume, etc.), and the sensing circuit76may provide an electrical signal output that includes information from any suitable combination of sensors80,82(e.g., information from a temperature sensor and a pressure sensor, or information from an acceleration sensor and a fluid level sensor, etc.). Further, while an assembly for an AWD vehicle is shown and described, it should be appreciated that the sensing system72may be used in various components of front-wheel drive only vehicles, rear-wheel drive vehicles, four-wheel drive vehicles, etc.

The ECU74may include one or more memory devices84coupled to one or more processors86. Memory84includes any non-transitory computer usable or computer readable medium, which may include one or more storage devices or articles. Non-transitory computer usable storage devices84may include conventional computer system RAM (random access memory), ROM (read only memory), EPROM (erasable, programmable ROM), EEPROM (electrically erasable, programmable ROM), and magnetic or optical disks or tapes. These of course are merely examples; other non-transitory computer usable storage devices84are possible as well. Memory84may be used to store instructions used to carry out at least a portion of the method described herein. The instructions may be embodied as software, firmware, or the like and may be executable using the processor(s)86. In addition, memory84may be used to store operational and/or temporal data acquired from the sensing circuit76(e.g., speed and/or temperature data).

Processor(s)86can be any type of device capable of processing electronic instructions including microprocessors, microcontrollers, electronic control circuits comprising integrated or discrete components, application specific integrated circuits (ASICs), and the like. The processor(s)86can be a dedicated processor(s)—used only for ECU74—or it can be shared with other vehicle systems (not shown). Processor(s)86can execute programs, process data and/or instructions, and thereby carry out at least part of the method discussed herein.

The communication link78may be any suitable wired or wireless linkage between the ECU74and the sensing circuit76. In at least one embodiment, the link78is wired and includes a single electrical path from the sensing circuit76to the ECU74. One example is a two-wire or twisted pair of wires—a signal (or hot) wire and a return (or ground) wire. In another example, only the signal wire is used and the ground wire is omitted; e.g., commonly referred to as a floating ground. These are merely examples; other implementations are also possible.

Turning toFIG. 3, a block diagram illustrates components of the sensing circuit76. In at least one embodiment, the sensing circuit76includes a speed circuit90that includes speed sensor80and a temperature circuit92that includes temperature sensor82. Other implementations may include circuits or sensors adapted to other functions. In at least some of these implementations, at least one circuit measures a frequency and the other circuit measures an amplitude or magnitude.

FIG. 4illustrates embodiments of both speed and temperature circuits90,92. As shown, the speed circuit90may include a switching element such as transistor T1, a resistor R1coupled between an input voltage V1and the transistor's collector (C), speed sensor80, and a resistor R2coupled between sensor80and the transistor's base (B) or input. While a NPN transistor is illustrated, other transistors or switching elements may be used instead.

The speed sensor80may be any suitable speed sensing circuit or any suitable contact or contactless sensor adapted to sense linear speed, angular speed, reciprocation, or other motion (e.g., in the illustrated embodiment, angular speed of ring gear58). Non-limiting examples of sensor80include a proximity sensor or transducer (e.g., using the Hall Effect), a linear variable differential transformer, an optical encoder, or the like, just to name a few examples. According to one an illustrative embodiment, sensor80is a Hall Effect sensor which is responsive to a magnetic field influenced by a ring gear element93—e.g., which may be located at a periphery of the ring gear58(as shown inFIG. 2). In at least one embodiment, element93is a permanent magnet or other magnetic component oriented and positioned so that its associated magnetic field is detectable by the Hall Effect sensor80as the ring gear58rotates. For example, the Hall Effect sensor80may provide an electrical output voltage or current based on the magnitude of the magnetic field which changes in response to the rotational position of the gear58.

As shown inFIG. 4, the speed circuit90may be coupled in series with the temperature circuit92. The temperature circuit92includes temperature sensor82, node N1, resistor R3, and ground G. More specifically, the transistor's emitter (E) (or switching element output) may be coupled in series with the temperature sensor82and node N1. Resistor R3may be coupled between node N1and ground G.

Temperature sensor82may be any suitable device or circuit for determining a thermal change in or around a vehicle component—e.g., such as the temperature change of the reservoir70(or the fluid therein). In at least one embodiment, temperature sensor82is a thermistor (e.g., having resistance RT1). In one implementation, the thermistor82is configured so that as the temperature of the thermistor rises, the resistance decreases and the corresponding voltage drop across the thermistor82decreases. Other non-limiting examples of temperature sensors82include a resistance thermometer, a bandgap temperature sensor, and the like, just to name a couple examples.

In operation of sensing circuit76, a predetermined voltage is provided at V1so that transistor T1is powered (e.g., when the vehicle is powered). Similarly, voltage V1(or other electrical power) may be provided to Hall Effect sensor80. When the ring gear58rotates, speed sensor80may detect a proximity of the element93carried by the ring gear58. For example, the Hall Effect sensor80may detect the magnetic field of the permanent magnetic element93when rotation of the ring gear58places the element93in relative proximity with the sensor80. Each time the Hall Effect sensor80detects the element93, the sensor80may provide a change in electrical output (e.g., electrical current). And when the Hall Effect sensor80no longer detects the element93, the sensor80may provide little-to-no electrical output (e.g., electrical current).

The alternating ON and OFF of the electrical current may switch the transistor T1ON and OFF, respectively, at the base B. Thus, current may flow through the transistor's emitter E only during intervals when the transistor T1is actuated ON. The switching pattern of the transistor T1is embodied as a square wave—the quantity of pulses per second (the frequency) representing the angular speed of ring gear58. Exemplary square waves are illustrated inFIGS. 5 and 6and will be discussed more below—the illustrated peaks VPand valleys VØof the square waves correspond to when the transistor T1is ON and OFF, respectively.

InFIG. 4, each time the transistor T1is actuated ON, current flows through the temperature circuit92. And the magnitude of the voltage at node N1is indicative of the temperature of sensor82. For example, it should be appreciated that sensor82(thermistor RT1), resistor R3, node N1, and ground G are arranged as a voltage divider. Therefore, the magnitude of the voltage at node N1—when the transistor T1is actuated ON—equals (R3/(R3+RT1))*VE(the voltage at the emitter E), where the value of VEmay be determined based on the value of V1and the electrical properties of the speed sensor80and transistor T1. Thus, the transmitted analog signal at output (O) to the ECU74includes both speed and temperature information.

Therefore, in this embodiment, the processor(s)86may be configured to determine the frequency of the ring gear58based on the frequency or switching of the transistor TRi.e., based on the peaks VPand valleys VØof the output signal. Further, the processor(s)86may be configured to extract from the electrical signal the magnitude of the voltage at node N1when the transistor T1is ON (e.g., at VP). This magnitude may be compared to a look-up table or similar data stored in memory84to determine an associated temperature value at the pan70. In other embodiments, the processor(s)86may be configured to determine an average voltage of the square wave. Based on the determined average value, the processor(s)86may determine the temperature value at the pan70. It should be appreciated that the ECU74may monitor the electrical, analog signal output (O) continuously, periodically, randomly, or intermittently, or the like.

FIGS. 5-6show examples of electrical signals received at the ECU74via output (O) and link78. The independent y-axes plot a normalized temperature amplitude (e.g., between 0-100%), and the dependent t-axes represent time. In each of the figures, the electrical signal includes a square wave having pulses which vary in frequency, where a higher square wave frequency (pulses per unit time) indicates a higher measured frequency at sensor80(e.g., a higher angular or rotational speed of ring gear58). InFIGS. 5 and 6, the magnitude or amplitude of each of the square waves is constant; however, the amplitude of the square wave shown inFIG. 5is greater than the amplitude of the square wave shown inFIG. 6. And the higher amplitude indicates a higher temperature at sensor82.

Thus, inFIG. 5, time duration5A indicates a relatively higher angular speed of ring gear58while the thermistor82is relatively hot. Time duration5B indicates a relatively slower angular speed of ring gear58while the thermistor82remains relatively hot.

And with respect toFIG. 6, time duration6A indicates a relatively higher angular speed of ring gear58while the thermistor82is relatively cool. Time duration6B indicates a relatively slower angular speed of ring gear58while the thermistor82remains relatively cool (e.g., the same temperature as in duration6A).

Collectively,FIGS. 5 and 6illustrate that frequency or speed data and temperature data from two different sensors can be superimposed or combined into a composite electrical signal output (O). As used herein, superimposing electrical signal data from at least two sensors excludes serial combination (e.g., it excludes sending frequency data first and then afterwards separately sending temperature data—or vice-versa). As shown inFIGS. 5-6, the frequency and temperature data can be transmitted simultaneously and a single discrete transmission or communication wire may be used between the ECU74and sensing circuit76. For example, circuit76may provide data from two sensors non-serially to ECU74without communication from ECU74to circuit76—e.g., circuit76may be operable without ECU74requesting the frequency data, requesting the temperature data, or requesting both. It should be appreciated that the graphs shown inFIGS. 5-6do not represent empirical data, but are intended only to illustrate exemplary electrical signals from output (O). Further, it should be appreciated that the illustrated square wave is an ideal signal; in practice, rise and fall times of each pulse are not typically instantaneous.

Other implementations of the sensing circuit shown inFIG. 4also exist. For example, a temperature circuit instead could be located between the speed sensor and the transistor T1—such that the temperature may be determined regardless of whether the ring gear58is rotating. Or for example, the sensing circuit could include two temperature circuits. For example, a first temperature circuit could be coupled between sensor80and the transistor base B, and a second temperature circuit could be coupled to the transistor emitter E (as it is shown inFIG. 4). In these implementations, two electrical outputs may be required (e.g., two voltage dividers).

In yet another implementation of the temperature sensor82and the speed sensor80, the voltage magnitude at node N1could be used at ECU74for calibration purposes. For example, at the ECU74, if the electrical characteristics of speed sensor80drift or vary across an environmental temperature range of the PTU20, then the processor86may use the voltage magnitude at node N1to correct or negate temperature-induced error or drift of sensor80. Again, ECU memory84could store look-up data that corresponds to temperature correction values for sensor80, and processor(s)86may be configured to perform such correction calculations using such data.

Now turning toFIG. 7, another embodiment of a sensing circuit is illustrated (e.g., circuit76′). Here, the sensing circuit76′ includes a speed circuit90′, a temperature circuit92′, and an output or superposition circuit94. Here, the electrical outputs of the speed and temperature circuits90′,92′ may be an input to the superposition circuit94, as described below.

FIG. 8illustrates a circuit diagram of sensing circuit76′—here, like numerals represent similar elements or elements having similar functions to those shown inFIG. 4. Speed circuit90′ is arranged similarly to that shown inFIG. 4; its arrangement and operation will not be re-described here. However, the arrangement of circuit90′ provides the voltage VE′ (at the switching element output) as a first input y1(t) to superposition circuit94.

The temperature circuit92′ includes a voltage divider arrangement similar to that of circuit92(seeFIG. 4), but also includes a voltage-controlled oscillator (VCO)96. Except for two differences, the voltage divider of circuit92′ may be identical to the voltage divider of circuit92. First, the input voltage of the voltage divider may be voltage V1′ or any other suitable voltage when the vehicle is powered (e.g., instead of voltage VE, as it is in circuit92). Second, node N1′ is a voltage input to VCO96(e.g., instead of the electrical signal output (O), as it is in circuit92).

VCO96may be configured to provide a predetermined frequency based on the input voltage at node N1′. For example, in at least one embodiment, when the temperature of sensor82increases, the voltage at node N1′ increases. And when the voltage at node N1′ increases—i.e., when the input voltage to VCO96increases—the frequency of the electrical output of VCO96(at node N2) may increase correspondingly. The relationship between the voltage input and the frequency output of VCO96may vary, depending on the electrical characteristics of VCO96. The relationship may be linear, or more commonly, exponential. As shown inFIG. 8, the output of the VCO96may be a second input y2(t) to the superposition circuit94.

The superposition circuit94may combine the frequencies received from the speed and temperature circuits90′,92′ into a single electrical signal in any suitable manner. In at least one embodiment, the circuit94sums the two frequencies algebraically. For example, the first input may be represented as y1(t)=A1*cos(ω1*t), where A1is the amplitude of the signal and ω1is the angular frequency. And for example, the second input at node N2may be represented as y2(t)=A2*cos(ω2*t), where A2is the amplitude of the signal and ω2is the angular frequency thereof. Then, the resulting composite wave at output (O′) may be expressed as: A1*cos(ω2*t)+A2*cos(ω2*t).

FIGS. 9 and 10illustrate exemplary analog waveforms received at the ECU74via output (O′) and link78—e.g., again, this data is not empirical but instead intended to merely provide examples of electrical signal outputs (O′) of sensing circuit76′.FIG. 9illustrates a primary waveform98and a secondary or ripple waveform99at the peaks VPof the pulses of the primary waveform98. The primary waveform98having a voltage ripple at its peaks VPis one example of a superimposed electrical output of the superposition circuit94. And in at least one embodiment, the primary waveform98may be representative of the angular speed of the ring gear58(measured using sensor80), and the ripple waveform99may be representative of the temperature (measured at sensor82). This superimposed output enables the angular frequency data (extractable from waveform98by ECU74) to be provided with or at the same time as the temperature data (extractable from waveform99at ECU74). InFIG. 9, the angular speed of ring gear58during time duration9A is relatively faster (or higher) than during time duration9B, as indicated by the change in frequency of the primary waveform98. InFIG. 9, the frequency of the ripple waveform99is generally constant during both durations9A and9B indicating a generally constant temperature at sensor82. As will be apparent from the discussion below, in at least one embodiment, a higher frequency ripple waveform99can be indicative of a relatively higher temperature, whereas a lower frequency ripple waveform99can be indicative of a relatively lower temperature at sensor82.

FIG. 10illustrates another example of a superimposed electrical output of the superposition circuit94—again, illustrating primary and ripple waveforms98,99. InFIG. 10, the angular frequency of ring gear58during time duration10A is relatively faster (or higher) than during time duration10B, as indicated by the change in frequency of the primary waveform98. Again, the frequency of the ripple waveform99is generally constant during durations10A and10B indicating a generally constant temperature at sensor82. A comparison ofFIGS. 9 and 10reveal that the frequency of the ripple waveform99inFIG. 9is higher than the frequency of the ripple waveform99inFIG. 10; in at least one embodiment, this indicates that the temperature at sensor82was measured to be higher (inFIG. 9, as opposed toFIG. 10). For example, the lower-frequency ripple waveform (inFIG. 10) (lower temperature at sensor82) may be attributable to higher resistance at sensor82(e.g., thermistor RT1), which results in a lower voltage at node N1′, which results in a lower voltage input to VCO96, and which results in a lower frequency output at node N2. And as explained above, a lower frequency output at node N2can result in a smaller or lower frequency ripple at the output (O′) when the y1(t) and y2(t) are superimposed.

FIGS. 9 and 10illustrate another embodiment within which frequency and temperature data from two different sensors can be superimposed or combined into a composite electrical signal output (O′). The circuit76′ also enables frequency and temperature data to be transmitted simultaneously over a single discrete transmission or communication wire between the ECU74and sensing circuit76′.

The embodiments shown inFIGS. 4 and 8—as well as other like implementations—have been discussed with respect to the PTU20. It should be appreciated that other components may be measured similarly, including other gear systems or other driveline components. For example, rear-wheel drive vehicles may not have a PTU20, but instead may have a rear drive module (RDM) (not shown)—e.g., to transfer power from the engine (e.g., in the front of the vehicle) to the rear differential assembly. In such vehicles, the rotational frequency of one or more gears within the RDM could be similarly measured. Other non-limiting examples include a rotating component on a vehicle engine or transmission, a transfer case (e.g., for a 4×4 vehicle), and an electric drive axle.

Other embodiments also exist using sensors which measure any suitable combination of physical properties or characteristics of vehicle devices. Non-limiting examples of physical properties or characteristics include temperature, linear speed, angular speed, acceleration, flow rate, pressure, etc. In other embodiments, at least two properties may be sensed by two different or separate sensors (or measuring circuits). In these embodiments, a sensing circuit may combine or superimpose the electrical signal data (e.g., DC data, AC data, or both) received from sensors into a single composite electrical signal output which may be provided to the ECU74, any other suitable vehicle system or module, or both.

Thus, there has been described a sensing system for a vehicle which includes a sensing circuit having two sensors or transducers. The sensing circuit is configured to superimpose data sensed and received by the sensors into a single electrical signal which may have frequency and/or magnitude characteristics representing at least two sensed data parameters. The electrical signal then may be transmitted to another vehicle device—e.g., which may be located elsewhere in the vehicle. In some implementations, the sensing system can include an electronic control unit which is configured to determine or extract the original sensed data parameters which make up the now-superimposed electrical signal—e.g., the signal data of the first sensor and the signal data of the second sensor.

While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It is not intended herein to mention all the possible equivalent forms or ramifications of the invention. It is understood that the terms used herein are merely descriptive, rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.