Patent ID: 12203822

DETAILED DESCRIPTION

Referring toFIG.1, a heterogeneous sensor system10for sensing a target14includes a magnetic field sensor20and an inductive sensor40. The magnetic field sensor (or simply magnetic sensor)20includes one or more magnetic field sensing elements30responsive to a magnetic field affected by the target14and configured to generate one or more magnetic field sensor output signals36indicative of a position and/or motion of the target, such as target angle in an example embodiment.

The inductive sensor40includes an oscillator with a driver42configured to generate an oscillation signal, a primary coil44coupled to receive the oscillation signal, and one or more secondary coils (here two secondary coils46,48) electromagnetically coupled to the primary coil as a function of the position (e.g., angle) of the target14. In other words, secondary coils46,48as can be referred to as pick-up coils, are electromagnetically coupled to the primary coil44and mechanically coupled to target14such that movement of the target causes position information to be encoded in secondary signals from coils46,48by amplitude modulation. The inductive sensor40is configured to generate one or more inductive sensor output signals56indicative of a position and/or motion of the target, such as target angle in the example embodiment. Elements of the inductive sensor40other than the transmit and receive coils44,46, and48can be referred to as inductive interface circuitry.

More particularly, primary coil44induces eddy currents in the target14, which eddy currents in turn induce a signal in the secondary coils46,48. As the target14moves (e.g., rotates), coupling between the primary winding44and the secondary windings46,48changes, so as to thereby encode target position information by way of amplitude modulation of the secondary signals generated in the secondary windings46,48. It will be appreciated that various mechanical configurations for the target14and primary and secondary coils44,46,48are possible.

A checker circuit or simply checker50is configured to receive one or more signals38based on magnetic field signal processing from a signal processor34and one or more signals78based on inductive signal processing from a signal processor74and determine whether a fault or error has occurred based on a comparison of the received signals. The received signals38,78can be intermediate signals (e.g., angle values calculated by respective signal processors34,74) and/or can be the magnetic field sensor output signals36and the inductive sensor output signals56that have been formatted in a desired protocol for communication to external circuits and systems. For simplicity of explanation, signals38,78, like respective signals36,56, can be referred to as magnetic field sensor output signals and inductive sensor output signals, respectively; however, it will be appreciated by those of ordinary skill in the art that such signals38,78can be identical to the formatted sensor output signals36,56or can represent information that has not been put into a particular output protocol format (e.g., SPI, PWM, SENT, etc.).

A high level of safety standard compliance can be achieved by using two unique (i.e., heterogeneous) sensors20,40and a checker circuit50to compare signals38,78from the two sensors in order to thereby implement heterogeneous redundancy. In the context of the disclosure, heterogeneous sensors20,40differ from each other in sensing methodology; namely, magnetic field sensor20senses a magnetic field affected by target movement and/or position and inductive sensor40senses signals that are amplitude modulated based on target movement and/or position.

Heterogeneous magnetic field and inductive sensors20,40are described herein in the context of angle sensing system10with which an angle of the target14is sensed. However, it will be appreciated by those of ordinary skill in the art that the described heterogeneous sensing methodologies and the advantages of incorporating such heterogeneous sensing in a single sensor system are applicable to other sensing applications. For example, in addition to or instead of angle sensing, other target parameters that can be sensed include, but are not limited to target speed and/or direction of motion. Further, other sensing applications for the described heterogeneous sensor systems include a magnetic sensor that senses position or proximity of a target, a movement detector or sensor such as a rotation detector or linear movement position sensor, a magnetic field sensor that senses a magnetic field density, and/or the magnetic field direction of a magnetic field.

The magnetic field sensor20and the inductive sensor40can be implemented in a single package assembly or package66or in multiple packages. Such a single package assembly66can include a single printed circuit board (PCB) for supporting elements of the system10other than the target14or can include multiple PCBs. In other implementations, the magnetic field sensor20and interface circuitry of the inductive sensor40(i.e., the portion of the inductive sensor40other than the transmit and receive coils44,46, and48) can be implemented in the form of one or more integrated circuits (IC s) including one or more semiconductor die or other substrates in one or more packages. The example sensor system10illustrates both the magnetic field sensor20and the inductive sensor interface circuitry integrated in a single IC60. It will be understood that the present disclosure is not limited to any specific integration of the magnetic field sensor20and inductive sensor40.

Target14can take various forms suitable for inductive and magnetic field sensing. In the context of the example angle sensing embodiment, target14can be rotatable about an axis of rotation. For example, target14can take the form of a gear fixedly coupled to a rotating shaft.

In some embodiments, the same conductive target or target portion can be sensed by both the magnetic field sensor20and the inductive sensor40(e.g.,FIGS.3,3A,4,4A,4B,4C, and5,6and7). In some embodiments, target14can have different portions (or can include more than one target) independently optimized for sensing by magnetic field sensor20and inductive sensor40(e.g.,FIGS.8,9,9A,10,10A).

In general, target14includes at least a portion comprised of a conductive material to enable inductive sensing. For this purpose, the conductive material of target14can be selected from a variety of materials, including but not limited to aluminum, copper, and steel and can be ferromagnetic or non-ferromagnetic.

In embodiments in which the same target or target portion is designed for sensing by both the magnetic field sensor20and the inductive sensor40, the conductive material of the target is ferromagnetic to enable magnetic field sensing by sensor20(e.g.,FIGS.3,3A,4,4A,4B,4C,5,6and7).

In embodiments in which the target includes different portions optimized for sensing by the magnetic field sensor20and the inductive sensor40, the conductive material of the target14can be optimized for inductive sensing in which case the material can be non-ferromagnetic with a high conductivity to provide a larger signal, thereby permitting a larger airgap and better resolution for inductive sensing (e.g.,FIGS.8,9,9A,10,10A). Although aluminum and copper are electrically well-suited for inductive sensing, steel can be more advantageous due to its more suitable mechanical properties such as hardness and strength.

In embodiments with different target portions or targets optimized for sensing by the magnetic field sensor20and the inductive sensor40, the target portion optimized for magnetic field sensing can be selected based on whether or not the magnetic field sensor20operates in a back bias fashion (i.e., with a proximate back bias magnet configured to generate the magnetic field that is affected by target movement). In such back bias embodiments, the target portion optimized for magnetic field sensing is ferromagnetic, preferably with a relative permeability greater than 10. Alternatively, the target portion optimized for magnetic field sensing can take the form of a ring magnet having alternating magnetic domains (i.e., pole pairs) with which the magnetic field is generated without a back bias magnet, in which case the sensing target portion can be ferromagnetic or non-ferromagnetic.

Magnetic field sensing elements30generate magnetic field signals indicative of a sensed magnetic field associated with the target14. Magnetic field sensing elements30can take the form of various transducer types configured to generate magnetic field signals32indicative of the sensed magnetic field. As used herein, the term “magnetic field sensing element” is used to describe a variety of electronic elements that can sense a magnetic field. The magnetic field sensing element can be, but is not limited to, a Hall effect element, a magnetoresistance element, or a magnetotransistor. As is known, there are different types of Hall effect elements, for example, a planar Hall element, a vertical Hall element, and a Circular Vertical Hall (CVH) element. As is also known, there are different types of magnetoresistance elements, for example, a semiconductor magnetoresistance element such as Indium Antimonide (InSb), a giant magnetoresistance (GMR) element, for example, a spin valve, an anisotropic magnetoresistance element (AMR), a tunneling magnetoresistance (TMR) element, and a magnetic tunnel junction (MTJ). The magnetic field sensing element may be a single element or, alternatively, may include two or more magnetic field sensing elements arranged in various configurations, e.g., a half bridge or full (Wheatstone) bridge. Depending on the device type and other application requirements, the magnetic field sensing element may be a device made of a type IV semiconductor material such as Silicon (Si) or Germanium (Ge), or a type III-V semiconductor material like Gallium-Arsenide (GaAs) or an Indium compound, e.g., Indium-Antimonide (InSb).

As is known, some of the above-described magnetic field sensing elements tend to have an axis of maximum sensitivity parallel to a substrate or in the plane of the substrate that supports the magnetic field sensing element, and others of the above-described magnetic field sensing elements tend to have an axis of maximum sensitivity perpendicular to a substrate that supports the magnetic field sensing element. In particular, planar Hall effect elements tend to have axes of maximum sensitivity perpendicular to a substrate, while metal based or metallic magnetoresistance elements (e.g., GMR, TMR, AMR) and vertical Hall effect elements tend to have axes of maximum sensitivity parallel to a substrate.

As used herein, the term “magnetic field signal” is used to describe any signal that results from a magnetic field experienced by a magnetic field sensing element.

In an example angle sensor, magnetic field sensing elements30include at least two elements, each of which generates a magnetic field signal32indicative of a sensed magnetic field affected by target14. The magnetic field signals32and their respective processing paths can be referred to as “channels.” In some embodiments, signals32include at least two signals that are orthogonal to one another, or in quadrature (i.e., a sinusoidal signal and a cosinusoidal signal) as can be useful in angle and direction detection. Generating such quadrature channel signals32can be accomplished by adjusting features of the target14, the positioning of the sensor IC60with respect to the target, the airgap between the target and the IC and/or the distance between sensing elements30. In some embodiments, sensing elements30can include fewer than two sensing elements or can include three or more sensing elements. In the case of three or more sensing elements30, the magnetic field sensor20can include three channels that are 60° phase shifted sinusoidal signals and the target angle can be derived from these three signals. It will be understood that the present disclosure is not limited to any specific number of magnetic field sensing elements30.

A signal processor34can operate on one or more magnetic field signals32in order to generate one or more magnetic field sensor output signals36. The magnetic field sensor output signals36can be indicative of speed, direction, and/or angle associated with the target14in example embodiments. For example, processor34can perform a speed calculation whereby a speed of motion (e.g., rotation) of the target14can be determined by comparing one or more magnetic field signals32to a threshold signal.

Direction calculation can be performed in various ways. For example, a direction of rotation of the target14can be determined by the phase relationship between magnetic field channel signals32, whereby a first direction of rotation can correspond to a first channel signal leading a second channel signal and a second, opposite direction of rotation can correspond to the first channel signal lagging the second channel signal. It will be understood that the present disclosure is not limited to any specific methodology for target speed and/or direction calculation.

An angular position of target14also can be determined in various ways, for example, by performing CORDIC processing on signals32. It will be understood that the present disclosure is not limited to any specific methodology for angle calculation.

Processor34can operate in the digital domain to generate magnetic field sensor output signals36for coupling to circuits and systems external to the IC60in order to thereby provide an indication of the sensed target parameter. Additional processing can be implemented by processor34including, but not limited to, gain and offset correction and/or harmonic correction as examples.

Magnetic field sensor output signals36can have a variety of formats to suit a particular application. For example, output signals36can be provided as quadrature differential analog signals (SINP, SINN, COSP, COSN) or an angle position signal provided in a Serial Peripheral Interface (SPI) format. The output signal format can be selected based on user-programmable parameters stored in EEPROM. It will be appreciated that other output signal information such as speed and direction and other output signal formats are possible, including but not limited to Pulse Width Modulation (PWM) format, Single Edge Nibble Transmission (SENT) format, Local Interconnect Network (LIN) format, CAN (Controller Area Network) format, and/or an Inter-Integrated Circuit (I2C) format to name a few. In some implementations, target speed, angle and/or direction computations are implemented by other circuits and systems (not shown) external to the IC60.

As used herein, the term “processor” or “controller” is used to describe an electronic circuit that performs a function, an operation, or a sequence of operations. The function, operation, or sequence of operations can be hard coded into the electronic circuit or soft coded by way of instructions held in a memory device. A “processor” can perform the function, operation, or sequence of operations using digital values or using analog signals. In some embodiments, the “processor” can be embodied in an application specific integrated circuit (ASIC), which can be an analog ASIC or a digital ASIC. In some embodiments, the “processor” can be embodied in a microprocessor with associated program memory. In some embodiments, the “processor” can be embodied in a discrete electronic circuit, which can be an analog or digital. A processor can contain internal processors or internal modules that perform portions of the function, operation, or sequence of operations of the processor. Similarly, a module can contain internal processors or internal modules that perform portions of the function, operation, or sequence of operations of the module.

Referring to the inductive sensor40, secondary windings46,48can be designed to have a predetermined phase relationship with respect to each other in order to suit a particular application. In the example angle sensor embodiment, secondary windings46,48can be designed to generate respective secondary signals in quadrature (i.e., having a nominal ninety-degree phase shift with respect to each other).

A front end processor70can be coupled to secondary windings46,48to process the received amplitude modulated signals. Example processing can include filtering such as EMI filtering and/or filtering by which analog signals from the secondary windings46,48are converted into digital signals (e.g., sigma delta filtering). Processor70also implements demodulation to generate demodulated position signals72indicative of the position of the target14.

A further signal processor74of the inductive sensor40can operate in the digital domain and implement signal processing functionality such as gain and offset correction and/or harmonic correction. Processor74can also operate on the demodulated position signals72to compute target speed, angle and/or direction for example, and can do so with the same or different methodologies as described above in connection with signal processor34.

Processor74can generate one or more output signals56for communication to circuits and systems external to the IC60in order to thereby provide an indication of the sensed target parameter. More particularly, like the magnetic field sensor output signals36, inductive sensor output signals56can have a variety of formats to suit a particular application. For example, output signals56can be provided as quadrature differential analog signals (SINP, SINN, COSP, COSN) or an angle position signal provided in a Serial Peripheral Interface (SPI) format. The output signal format can be selected based on user-programmable parameters stored in EEPROM. It will be appreciated that other output signal information such as speed and direction and other output signal formats are possible, including but not limited to Pulse Width Modulation (PWM) format, Single Edge Nibble Transmission (SENT) format, Local Interconnect Network (LIN) format, CAN (Controller Area Network) format, and/or an Inter-Integrated Circuit (I2C) format to name a few. In some implementations, target speed, angle and/or direction computations are implemented by other circuits and systems (not shown) external to the IC60.

Checker50is configured to receive one or more signals38from magnetic field signal processor34and one or more signals78from inductive signal processor74and determine whether a fault or error has occurred based on a comparison of the received signals. For example, signal38can represent angle information calculated based on magnetic field sensing and signal78can represent angle information calculated based on inductive sensing and the signals38,78can be compared by checker50. If the difference between the signals38,78is greater than a predetermined threshold, which threshold value depends on application specific safety limits, the checker50can signal a fault to an external system. Checking by checker50based on signals38,78that represent angle information (e.g., as opposed to checking based on formatted output signals36,56of a particular protocol) leaves more flexibility in having different type of output protocols (e.g., analog, SPI, PWM, SENT, etc.). An error can correspond to a result of the comparison being outside of a predetermined range.

Checker50may provide an error, or fault signal54for coupling to external circuits and systems for further processing or action. In some embodiments, the fault signal54is combined with the magnetic field sensor output signals36and/or with the inductive sensor output signals56in order to provide “composite” output signals that not only convey information about the target parameter sensed by the sensor IC60, but also fault information as well.

Various techniques and/or circuitry can be used to implement checker50. In some embodiments, checker50can function to sample one or more magnetic field sensor signals38and one or more inductive sensor output signals78and can include a synchronizer and a window comparator. For example, the synchronizer can provide a clock signal to the sample circuits to synchronize sampling and the synchronized, sampled signals can be coupled to inputs of the window comparator. The clock signal can also be coupled to the window comparator to control the time of comparison of the sampled signals. If implemented in the analog domain, sampling can be achieved with sample and hold circuits including a switch and capacitor whereby charge from the respective input signal is selectively stored on the capacitor when the switch is closed and held on the capacitor when the switch is open. In embodiments in which the checker50is implemented in the digital domain, sampling can be accomplished with digital registers or other suitable digital storage.

The window comparator can compare the sampled signals and generate fault signal54to indicate a fault if the sampled signals differ by more than a predetermined amount. In this configuration, one of the sampled signals provides the comparator threshold voltage and the other sampled signal provides the comparator input. The checker output signal54can be provided in a first logic state when the difference between the first and second sampled signals is less than a predetermined amount, as may be established by a resistor divider within the window comparator, and in a second logic state when the difference between the first and second sampled signals is greater than the predetermined amount.

In embodiments, the predetermined amount may be specified in terms of an absolute acceptable variation between the magnetic and inductive sensor outputs (e.g., in an angle sensor, the predetermined amount may correspond to a magnetic field angle error of 10°). In some embodiments, the predetermined amount can be a percentage difference (e.g., in an angle sensor, the predetermined amount can correspond to the sensor output being within 5% of the actual magnetic field angle). The predetermined amount can also be a programmable or selectable value.

The fault signal54can take various forms, such as a logic signal having a level depending on the difference between the first and second sampled signals, or a flag that is set when the difference between the sampled signals is greater than a predetermined amount and that is not cleared until some system function occurs or until cleared by a system processor, for example.

In an alternative checker configuration, checker50can include a delay element in series with one or both of the sample circuits and a window comparator. The delay element can delay signals38,78before or after sampling in order to thereby ensure synchronization of the compared signals.

As used herein, the term “predetermined,” when referring to a value or signal, is used to refer to a value or signal that is set, or fixed, in the factory at the time of manufacture, or by external means.

It should be understood that a so-called comparator can be comprised of an analog comparator having a two-state output signal indicative of an input signal being above or below a threshold level (or indicative of one input signal being above or below another input signal). However, the comparator can also be comprised of a digital circuit having an output signal with at least two states indicative of an input signal being above or below a threshold level (or indicative of one input signal being above or below another input signal), respectively, or a digital value above or below a digital threshold value (or another digital value), respectively.

While circuitry shown in figures herein may be described and/or shown in the form of analog blocks or digital blocks, it will be understood that the analog blocks can be replaced by digital blocks that perform the same or similar functions and the digital blocks can be replaced by analog blocks that perform the same or similar functions. Analog-to-digital or digital-to-analog conversions may not be explicitly shown in the figures, but should be understood.

Referring also toFIG.2, a sensor system200illustrates an example “on axis” or “end of shaft” configuration of a heterogeneous sensor260positioned proximate to a rotatable target210. Sensor260can be the same as or similar to sensor66ofFIG.1and thus, can include a magnetic field sensor220having magnetic field sensing elements and an inductive sensor240having a primary coil and two or more secondary coils. Target210can be the same as or similar to target14ofFIG.1and thus, can include at least a portion that is conductive for sensing by inductive sensor240.

In some implementations, target210is rotatable about an axis of rotation222as illustrated by arrow212. Example target210can include a rotatable shaft214having a gear or other element216fixedly coupled to the shaft and including features for sensing by sensors220,240. Example target features include cut outs (e.g.,FIG.3) and/or teeth separated by slots or “valleys” (e.g.,FIG.3A).

Target210can have a target plane218in which the target features are located for sensing by sensor260. By “on axis” it is meant that the sensor260has a major surface supporting magnetic field sensing elements (e.g., sensing elements30ofFIG.1) in a sensing plane264that is substantially parallel with respect to the target plane218.

In embodiments in which the same target is used for both magnetic and inductive sensing, target210can be comprised of a conductive ferromagnetic material and, in use, a back bias magnet (not shown) can be positioned proximate to the target and sensor260to generate a magnetic field affected by movement of the target for sensing by the magnetic field sensor220. Elements of system200are not sized to scale, but are illustrative only of the relative placement of the sensor260and target210.

In embodiments in which different targets or target portions are used for magnetic and inductive sensing, only the portion of target element216that is sensed by the inductive sensor240need be conductive and can be non-ferromagnetic.

The primary coil associated of the inductive sensor240can be positioned so that the primary coil generates a magnetic field that induces eddy currents in the conductive portion of target element216. The secondary coils of the inductive sensor240can be positioned so that the magnetic field generated by the eddy currents is sensed by the secondary coils.

Referring also toFIG.3, an example target300that can be used for both magnetic sensing and inductive sensing by an above-described sensor66,260ofFIGS.1and2is shown. To this end, the material of target300is conductive and ferromagnetic. In use, a back bias magnet is positioned proximate to the target300and sensor to generate a magnetic field for sensing by the magnetic field sensor.

Target300has a central axis304(perpendicular to the page) about which the target rotates and radial axes that rotate as the target rotates as illustrated by axes308a,308b,308c. Target300has an outer radius310and an inner radius312and a plurality of features320positioned around the target circumference between the outer radius and the inner radius in a target plane324. In the example target300, features320can be cut outs, or apertures of various shapes. Features320can have a circumferential width illustrated by an angle α. Features320can be repeated after an angle β, that can be equal to or different than α. The number of features320can correspond to the number of periods of the target300.

FIG.3Ashows another example target350that can be used for both magnetic field sensing and inductive sensing by an above-described sensor66,260ofFIGS.1and2. Like target300, target350has a central axis354(perpendicular to the page) about which the target rotates and radial axes as illustrated by axes358a,358b,358c. Target350has an outer radius360and an inner radius362and a plurality of features370positioned around the target circumference between the outer radius and the inner radius in a target plane374. In the example target350, features370can take the form of teeth or protrusions separated by slots or “valleys”, as shown. Features370have a circumferential width illustrated by an angle α that can repeat after an angle β that can be equal to or different than α.

Referring also toFIG.4, an example on axis heterogeneous sensor system400illustrates an arrangement of a magnetic field sensor416and an inductive sensor418relative to a rotating target414that can be the same as or similar to target300ofFIG.3. Thus, target414can have a central axis404(perpendicular to the page) about which the target rotates and radial axes as illustrated by axes408a,408b,408c. Target414has an outer radius410and an inner radius412and a plurality of features420positioned around the target circumference between the outer radius and the inner radius in a target plane424.

Target414can be comprised of a conductive ferromagnetic material and, in use, a back bias magnet (not shown) is positioned proximate to the target and magnetic field sensor416to generate a magnetic field for sensing by the magnetic field sensor.

The magnetic field sensor416can be the same as or similar to magnetic field sensor20ofFIG.1and the inductive sensor418can be the same as or similar to inductive sensor40ofFIG.1. In the arrangement ofFIG.4however, magnetic field sensor416and inductive sensor418are not integrated into a package66or IC60, but rather are shown as separate elements.

Inductive sensor418can be arc-shaped as shown and can include interface circuitry and primary and secondary coils.

In the arrangement ofFIG.4, the magnetic field sensor416and the inductive sensor418are positioned adjacent to each other in a circumferential direction (i.e., the direction of target rotation) illustrated by arrow406with respect to the target axis of rotation404.

FIG.4Ashows an alternative on axis heterogeneous sensor system440including target414(FIG.4) and a plurality of magnetic field sensors446a,446b,446cand inductive sensors448a,448b,448cfor additional redundancy purposes. Each of the magnetic field sensors446a,446b,446ccan be positioned adjacent to a respective inductive sensor448a,448b,448c, as shown.

Target414can be comprised of a conductive ferromagnetic material and, in use, back bias magnets (not shown) are positioned proximate to the target and to each of the sensors446a,446b,446cto generate a magnetic field for sensing by the magnetic field sensors.

Each magnetic field sensor446a,446b,446ccan be the same as or similar to magnetic field sensor20ofFIG.1and each inductive sensor448a,448b,448ccan be the same as or similar to inductive sensor40ofFIG.1. In the arrangement ofFIG.4Ahowever, the magnetic field sensors446a,446b,446cand inductive sensors448a,448b,448care not integrated into a single package66or IC60, but rather are shown as separate elements.

Inductive sensors448a,448b,448ccan be arc-shaped as shown and can include interface circuitry and primary and secondary coils.

In the arrangement ofFIG.4A, the magnetic field sensors446a,446b,446cand the inductive sensors448a,448b,448care positioned adjacent to each other in a circumferential direction (i.e., the direction of target rotation) illustrated by arrow406with respect to the target axis of rotation404.

It will be appreciated that while the system440is shown to include three magnetic sensors446a,446b,446cand three inductive sensors448a,448b,448c, other numbers (fewer or greater than three) can be used to achieve a different level of redundancy.

FIG.4Bshows another on axis heterogeneous sensor system460including a magnetic field sensor466and an inductive sensor468relative to a rotating target472. Target472can have a central axis474(perpendicular to the page) about which the target rotates and radial axes as illustrated by axis464. Features476of the target472are positioned around the target circumference between an outer radius462and an inner radius470in a target plane478. Target472can differ from target414(FIGS.4,4A) in that the features476are larger in the radial direction464than features420of target414.

Target472can be comprised of a conductive ferromagnetic material and, in use, a back bias magnet (not shown) is positioned proximate to the target and magnetic field sensor466to generate a magnetic field for sensing by the magnetic field sensor466.

The magnetic field sensor466can be the same as or similar to magnetic field sensor20ofFIG.1and the inductive sensor468can be the same as or similar to inductive sensor40ofFIG.1. In the arrangement ofFIG.4Bhowever, magnetic field sensor466and inductive sensor468are not integrated into a single package66or IC60, but rather are shown as separate elements.

Inductive sensor468can be arc-shaped as shown and can include interface circuitry and primary and secondary coils.

In the arrangement ofFIG.4B, the magnetic field sensor466and the inductive sensor468are positioned adjacent to each other in a radial direction (i.e., the direction of radial axis464) with respect to the target axis of rotation474. Thus, the magnetic field sensor466and the inductive sensor468are at different radial distances from the center474of the target472. The design of target features476accommodates positioning of the magnetic field sensor466and inductive sensor468in this manner.

It will be appreciated by those of ordinary skill in the art that although the inductive sensor468is shown to be positioned adjacent to the outside edge of the target472, in other implementations, inductive sensor468can be positioned closer to the target center474than the magnetic field sensor466.

FIG.4Cshows yet another on axis heterogeneous sensor system480including a magnetic field sensor486and an inductive sensor488relative to rotating target472(FIG.4B). Thus, target472can have a central axis474(perpendicular to the page) about which the target rotates and radial axes as illustrated by axis464. Features476of the target472are positioned between an outer radius462and an inner radius470in a target plane478.

Target472can be comprised of a conductive ferromagnetic material and, in use, a back bias magnet (not shown) is positioned proximate to the target and magnetic field sensor486to generate a magnetic field for sensing by the magnetic field sensor.

The magnetic field sensor486can be the same as or similar to magnetic field sensor20ofFIG.1and the inductive sensor488can be the same as or similar to inductive sensor40ofFIG.1. In the arrangement ofFIG.4Chowever, magnetic field sensor486and inductive sensor488are not integrated into a single package66or IC60, but rather are shown as separate elements.

Inductive sensor488can have a round, O-ring shape as shown and can include interface circuitry and primary and secondary coils.

In the arrangement ofFIG.4C, the magnetic field sensor486and the inductive sensor488are positioned adjacent to each other in a radial direction (i.e., the direction of radial axis464) with respect to the target axis of rotation474. Thus, the magnetic field sensor486and the inductive sensor488are at different radial distances from the center474of the target472. The design of target features476accommodates positioning of the magnetic field sensor486and inductive sensor488in this manner.

It will be appreciated by those of ordinary skill in the art that although the inductive sensor488is shown to be positioned adjacent to the outside edge of the target472, in other implementations, inductive sensor488can be positioned closer to the target center474than the magnetic field sensor486.

Referring toFIG.5, another on axis heterogeneous sensor system500includes target414(FIG.4) and a sensor PCB510supporting a magnetic field sensor520and inductive sensor540. Thus, target414can have a central axis404(perpendicular to the page) about which the target rotates, an outer radius410, an inner radius412, and a plurality of features420positioned around the target circumference between the outer radius and the inner radius in a target plane424. Target414can be comprised of a conductive ferromagnetic material and, in use, a back bias magnet (not shown) is positioned proximate to the target and magnetic field sensor520to generate a magnetic field for sensing by the magnetic field sensor.

Magnetic field sensor520can be the same as or similar to magnetic field sensor20ofFIG.1and inductive sensor540can be the same as or similar to inductive sensor40ofFIG.1. Thus, inductive sensor540includes primary and secondary coils, here illustrated as an arc-shaped element530, and interface circuitry534.

The magnetic field sensor520and the inductive sensor elements530,534can mounted on the sensor PCB510in various positions, such as the circumferentially adjacent positioning shown. Magnetic field sensor520and inductive interface circuitry534can each take the form of respective ICs. Inductive sensor coils530can be formed on the PCB510. In some embodiments, the coils530can be configured with the primary or transmit coil encompassing the secondary or receive coils, for example on the same layer of a two layer PCB.

Referring also toFIG.6, a sensor system600illustrates an example “off axis” or “side shaft” configuration of a heterogeneous sensor606positioned proximate to a rotatable target610. Sensor606can be the same as or similar to sensor package66ofFIG.1and thus, can include a magnetic field sensor620having magnetic field sensing elements and an inductive sensor640having a primary coil and two or more secondary coils. Target610can be the same as or similar to target14ofFIG.1and thus, can include at least a portion that is conductive for sensing by inductive sensor640. The relative sizes of the elements of system600are not necessarily sized to scale but are illustrative only of the relative placement of the sensor606and target610.

In embodiments in which the same target is used for both magnetic and inductive sensing, target610can be comprised of a conductive ferromagnetic material and, in use, a back bias magnet (not shown) can be positioned proximate to the target and sensor to generate a magnetic field affected by movement of the target for sensing by the magnetic field sensor620. Alternatively, a ring magnet can be attached to a conductive non-ferromagnetic or ferromagnetic target to generate a magnetic field for sensing by the magnetic field sensor620, in which case the back bias magnet can be eliminated.

In some implementations, target610is rotatable about a central axis of rotation622. Target610has features624for sensing by sensors620,640. Features624are positioned around the target circumference between an outer radius614(that can be coincident with an outer radius of the target) and an inner radius616of the target610. The illustrated target610is a gear having teeth624separated by slots or “valleys”.

Target610can have a target plane618orthogonal with respect to the axis of rotation622and the target features624are located on a circumferential edge612of the target (i.e., substantially tangential to the outer radius614of the target610). By “off axis” it is meant that the sensor606has a major surface supporting magnetic field sensing elements (e.g., sensing elements30ofFIG.1) in a sensing plane that faces (i.e., is substantially tangential with respect to) the circumferential edge612of the target. In other words, in off axis embodiments, a sensing plane640aof the inductive sensor640and a sensing plane620aof the magnetic field sensor620face the target edge612, as shown, and sensing planes620a,640aare generally orthogonal with respect to major target surface618.

The inductive sensor640including primary and secondary coils and interface circuitry can be mounted on a flexible, curved printed circuit board.

It will be appreciated that while the side shaft sensor system600is shown to have the magnetic field sensor620separately packaged with respect to the inductive sensor640, in some implementations, the magnetic field sensor620and the inductive sensor640(or at least interface circuitry portions of the inductive sensor) can be provided in the same package, can be mounted on the same PCB, and/or can be integrated into the same IC.

Referring toFIG.7, a heterogeneous sensing system700is shown to include a target714having two sets of features, as may be referred to as so-called tracks, in order to detect the absolute position of the target (i.e., absolute rotational angle). Reference numbers710,712can refer interchangeably to tracks and the features of the tracks. Features710,712can be positioned around the target circumference in a target plane724that is orthogonal with respect to an axis of rotation704(perpendicular to the page) about which the target rotates. More particularly, the target714has an outer radius708, an intermediate radius706, and an inner radius702, and the first track of features710extends from the outer radius to the intermediate radius and the second track of features712extends from the intermediate radius to the inner radius, as shown. Features710,720can take the form of cut-outs or apertures in the target material. However, it will be appreciated that the features710,712can take various forms.

Sensor system700includes a magnetic field sensor and inductive sensor positioned proximate to each track710,712. Magnetic field sensor720and inductive sensor740are positioned to sense features of track710and magnetic field sensor722and inductive sensor742are positioned to sense features of track712. The magnetic field sensors720,722and the inductive sensors740,742can be positioned in a sensing plane that is substantially parallel with respect to the target plane724.

In embodiments in which the same target is used for both magnetic and inductive sensing, target714can be comprised of a conductive ferromagnetic material and, in use, a first back bias magnet (not shown) is positioned proximate to the first magnetic field sensor720to generate a magnetic field for sensing by the magnetic field sensor720and a second back bias magnet (not shown) is positioned proximate to the second magnetic field sensor722to generate a magnetic field for sensing by the magnetic field sensor722.

Tracks710,712can have different numbers of features and can have different spacing between adjacent features. Given that tracks710,712with different numbers of features will have a different number of magnetic poles, it is possible to determine the absolute angular position of the target714using the Nonius principle. Along the tracks710,712, there is a continuing shift of pole alignment between the two tracks. Each track710,712provides position information with the same periodicity as its number of poles. The absolute angular position of the target714can be determined based on the difference in information provided by the two tracks. Stated differently, with this arrangement, it is possible to use the Nonius principle with a track710having N features and another track712having N+1 features to calculate the absolute mechanical angle.

While each magnetic sensor720,722is shown to be circumferentially offset from a respective inductive sensor740,742in some implementations the magnetic field sensors can be closer to (i.e., less circumferentially offset from) or further from (i.e., more circumferentially offset from) the respective inductive sensor than shown. It will also be appreciated that while one magnetic field sensor and inductive sensor are shown to sense each track710,712, in some implementations, more than one magnetic field sensor and inductive sensor can be used to sense each track for additional redundancy.

Referring also toFIG.8, a heterogeneous sensing system800includes a target814having a first target portion816optimized for sensing by a magnetic field sensor820and a second target portion818optimized for sensing by an inductive sensor820. Target814has a central axis804about which the target rotates. Target814has an outer radius812, an intermediate radius808, and an inner radius806. The magnetic sensing target portion816can be positioned between the outer radius812and the intermediate radius808and the inductive sensing target portion818can be positioned between the intermediate radius808and the inner radius806, as shown.

Inductive sensing target portion818is comprised of a conductive material. Features810of inductive sensing target portion818can take the form of cutouts or apertures in the target material spaced around the target circumference, as shown.

Magnetic sensing target portion816can take the form of a ring magnet having alternating magnetized domains around its circumference, two of which are labeled816a,816b. Target portion816can be comprised of a non-ferromagnetic material.

The target portion816and the target portion818can be positioned adjacent to each other in a radial direction and in a target plane824that is orthogonal with respect to the axis of rotation804, as shown. It will be appreciated that while the magnetic target portion816is positioned concentrically outside of the inductive target portion818, the positions of the target portions816,818can be reversed.

The target814can be manufactured by forming the inductive sensing portion818with cutouts810, as shown, such as by machining. A channel or groove can be machined into the target material and the ring magnet816can be separately manufactured and inserted into the channel to form the target814. In this way, the ring magnet816can be embedded in the main target body.

Magnetic field sensor820as may be the same as or similar to sensor20ofFIG.1is positioned proximate to the magnetic sensing target portion816and inductive sensor840as may be the same as or similar to inductive sensor40ofFIG.1is positioned proximate to the inductive sensing target portion818. The magnetic field sensor820and the inductive sensor840are positioned with their respective sensing elements in a sensing plane that is substantially parallel with respect to target plane824.

In use, magnetic field sensing elements of the magnetic field sensor820detect the magnetic field generated by the ring magnet816as features816a,816bpass by the sensor820when the target rotates and inductive pick up coils of the inductive sensor840detect the magnetic field generated by eddy currents in the inductive target portion818as features810pass by the sensor840when the target rotates. The conductive material of the inductive target portion818can be magnetically transparent and in example embodiments, comprises aluminum.

It will be appreciated that the magnetic field sensor820and inductive sensor840can be less or more radially offset from each other than is shown. It will be further appreciated that more than one magnetic field sensor and/or inductive sensor can be used for additional redundancy. Also, more than one inductive sensing target portion818and magnetic sensing portion816with additional magnetic and inductive sensors can be provided to implement absolute angle sensing using the Nonius principle.

Referring also toFIGS.9and9A, an alternative heterogeneous sensing system900includes a target914having a first target portion912optimized for sensing by a magnetic field sensor920and a second target portion918optimized for sensing by an inductive sensor940.FIG.9Ais a cross-sectional side view taken along line9A-9A ofFIG.9.

Target914has a central axis904about which the target rotates. Target914has an outer radius908and an inner radius906. The magnetic sensing target portion912and the inductive sensing target portion918can have features positioned between the outer radius908and the inner radius906in a target plane924, as shown.

Inductive sensing target portion918is comprised of a conductive material. Features910of inductive sensing target portion918can take the form of cutouts or apertures in the target material spaced around the target circumference, as shown.

Magnetic sensing target portion912can take the form of a ring magnet having alternating magnetized domains around its circumference, two of which are labeled912a,912b. Target portion912can be comprised of a non-ferromagnetic material.

The target portion912and the target portion918can be positioned adjacent to each other in an axial direction that is parallel with respect to the axis of rotation904as can be seen from the cross-sectional side view ofFIG.9A. Various manufacturing techniques for fabricating the target914are possible. For example, ring magnet912and inductive sensing target portion918can be separately manufactured and the ring magnet912can be glued or otherwise secured to the main target body918.

Magnetic field sensor920as may be the same as or similar to sensor20ofFIG.1is positioned proximate to the magnetic sensing target portion912and inductive sensor940as may be the same as or similar to inductive sensor40ofFIG.1is positioned proximate to the features910of the inductive sensing target portion918. The magnetic field sensor920and the inductive sensor940are positioned adjacent to each other in a circumferential direction with respect to the axis of rotation904and in a sensing plane that is substantially parallel with respect to the target plane924.

In use, magnetic field sensing elements of the magnetic field sensor920detect the magnetic field generated by the ring magnet912as features912a,912bpass by the sensor920when the target rotates and inductive pick up coils of the inductive sensor940detect the magnetic field generated by eddy currents induced in the inductive target portion918as features910pass by the sensor940when the target rotates. The conductive material of the inductive target portion918can be magnetically transparent and in example embodiments, comprises aluminum.

It will be appreciated that the magnetic field sensor920and inductive sensor940can be less or more circumferentially offset from each other than is shown. It will be further appreciated that more than one magnetic field sensor and/or inductive sensor can be used for additional redundancy.

Referring also toFIGS.10and10A, a heterogeneous sensing system1000includes a target1014having two portions1026,1028optimized for magnetic sensing and a two portions1034,1038of a target body1016optimized for inductive sensing. The first magnetic sensing target portion1026together with the first inductive target portion1034can establish a first so-called track1030and the second magnetic sensing target portion1028together with the second inductive target portion1038can establish a second so-called track1032. Use of two target tracks1030,1032can facilitate detection of the absolute position of the target1014(i.e., absolute rotational angle).FIG.10Ais a bottom perspective view of the arrangement ofFIG.10.

Target portions1034,1038can be positioned in a target plane1024that is orthogonal with respect to an axis of rotation1004about which the target rotates. More particularly, the target1014has an outer radius1012, an intermediate radius1008, and an inner radius1006. The first track1030is positioned between the outer radius1012and the intermediate radius1008and the second track1032is positioned between the intermediate radius1008to the inner radius1006, as shown.

Magnetic sensing target portions1026,1028can take the form of ring magnets having alternating magnetized domains, two of which for each such target portion are labeled1026a,1026band1028a,1028b(FIG.10A), respectively. Target portions1026,1028can be comprised of a non-ferromagnetic material.

Features of the first and second inductive sensing target portions1034,1038can take the form of cut-outs or apertures in the material of the target body1016. However, it will be appreciated that the features can take various forms.

The magnetic sensing target portions1026,1028can be positioned adjacent to the respective inductive sensing target portion1034,1038in an axial direction that is parallel with respect to the axis of rotation1004as can be seen from the view ofFIG.10A. Various manufacturing techniques are possible for fabricating the target1014. For example, ring magnets1026,1028and inductive sensing target body1016can be separately manufactured and the ring magnets1026,1028can be glued or otherwise secured to the target body1016.

Sensor system1000includes a magnetic field sensor and inductive sensor positioned proximate to each track1030,1032. Magnetic field sensor1020and inductive sensor1040are positioned to sense features of track1030and magnetic field sensor1022and inductive sensor1042are positioned to sense features of track1032. The magnetic field sensors1020,1022and the inductive sensors1040,1042can be positioned in a sensing plane that is substantially parallel with respect to the target plane1024with magnetic field sensor1020adjacent to inductive sensor1040in a circumferential direction and magnetic field sensor1022adjacent to inductive sensor1042in a circumferential direction, as shown. Magnetic field sensors1020,1022can be the same as or similar to sensor20ofFIG.1and inductive sensors1040,1042can be the same as or similar to inductive sensor40ofFIG.1.

Tracks1030,1032can have different numbers of features (e.g., cut outs in the case of inductive sensing target portions1034,1038and magnetized pole pairs1026a,1026band1028a,1028bin the case of magnetic sensing ring magnets1026,1028, respectively) and can have different spacing between features. Given that tracks1030,1032with different numbers of features will have a different number of magnetic poles, it is possible to determine the absolute angular position of the target1014using the Nonius principle. Along the tracks1030,1032, there is a continuing shift of pole alignment between the two tracks. Each track1030,1032provides position information with the same periodicity as its number of poles. The absolute angular position of the target1014can be determined based on the difference in information provided by the two tracks. Stated differently, with this arrangement, it is possible to use the Nonius principle with a track1030having N features and another track1032having N+1 features to calculate the absolute mechanical angle.

While each magnetic sensor1020,1022is shown to be circumferentially offset from a respective inductive sensor1040,1042, in some implementations the magnetic field sensors can be closer to (i.e., less circumferentially offset from) or further from (i.e., more circumferentially offset from) the respective inductive sensor than shown. It will be appreciated that while one magnetic field sensor and inductive sensor are shown to sense each track1030,1032, in some implementations, more than one magnetic field sensor and inductive sensor can be used to sense each track for additional redundancy.

Referring toFIG.11, a torque sensing system1100including a magnetic field sensor1120is shown. Two targets1116,1118can be coupled to a rotatable shaft having two portions or shafts1110,1114coupled by an elastic element such as a torsion bar1112, such that detection of a difference between an angle of the first target1116and an angle of the second target1118can indicate torque applied to the first and/or second shaft1110,1114. In other words, when a torque is applied, the angle of shafts1110,1114will be slightly different depending on torque magnitude.

Each target1116,1118can be a ferromagnetic target including features. For simplicity, only two features are labelled for each target as1116a,1116band1118a,1118b. Such features may take the form of gear teeth in some implementations.

The torsion bar1112can be part of the physical connection between the shafts1110,1114and can increase angle signal strength for angle measurements by creating a larger angle of twist (which is easier to measure/detect) for a given applied torque to either shaft1110,1114. The rotatable shafts1110,1114can be parts of a steering column in an example automotive application.

A magnetic field sensor package1120is positioned between the first target1116and the second target1118and includes a first magnetic field sensor1124positioned proximate to the first target1116and that is configured to generate a first magnetic field output signal indicative of an angle of the first target and a second magnetic field sensor1126positioned proximate to the second target1118and that is configured to generate a second magnetic field output signal indicative of an angle of the second target. Magnetic field sensors1124,1126can be the same as or similar to magnetic field sensor20ofFIG.1.

Magnetic field sensors1124,1126share a back bias magnet1130that is positioned between the first and second magnetic field sensors and configured to generate a magnetic field that is affected by rotation of the targets1116,1118. In implementations, each magnetic field sensor1124,1126can be supported by a respective semiconductor die that is mounted to an opposite surface of the back bias magnet1130.

A processing unit, as may be part of the sensor1120or external to the sensor, can be coupled to receive the first and second magnetic field output signals from sensors1124,1126and configured to determine a difference between the angle of the first target1116and the angle of the second target1118based on the first and second magnetic field output signals. A torque applied to the first shaft1110and/or to the second shaft1114can be calculated based on the angle difference.

The sensor1120can be mounted in the system1100in various configurations to meet system requirements. As one non-limiting example, a PCB can be mounted to a stationary sleeve coupled to the rotatable shafts1110,1114and can be provided with an aperture in which the magnetic field sensor package1120is positioned. Mounting of the sensor1120can be achieved to ensure that the airgap (i.e., the distance from the sensing elements to the respective target) is the same for both sensors1124,1126. A concentrator (not shown) can be used to improve performance.

Referring also toFIG.12, an alternative torque sensing system1200includes a heterogeneous sensor1210incorporating magnetic field sensing and inductive sensing. The sensor1210can be mounted in an aperture1238of a PCB1236. The PCB1236can be mounted to a stationary sleeve coupled to rotatable shafts (not shown inFIG.12for simplicity, but which shafts can be the same as or similar to shafts1110,1114ofFIG.11that are coupled to respective rotatable targets1116,1118).

Like sensor1120ofFIG.11, sensor1210can include a first magnetic field sensor1214to be positioned proximate to a first target (e.g., target1116) and that is configured to generate a first magnetic field output signal indicative of an angle of the first target and a second magnetic field sensor1216to be positioned proximate to a second target (e.g., target1118) and that is configured to generate a second magnetic field output signal indicative of an angle of the second target. Magnetic field sensors1214,1216can be the same as or similar to magnetic field sensor20ofFIG.1.

Magnetic field sensors1214,1216share a back bias magnet1230that is positioned between the first and second magnetic field sensors and configured to generate a magnetic field that is affected by rotation of proximate targets. In implementations, each magnetic field sensor1214,1216is supported by a respective semiconductor die that is mounted to an opposite surface of the back bias magnet1230.

Heterogeneous sensing system1200further includes inductive sensors as may be incorporated into an inductive sensor unit1240. A first inductive sensor1242can be positioned to face the first target (e.g., target1116) and a second inductive sensor1244can be positioned to face the second target (e.g., target1118). Inductive sensors1242,1244can be the same as or similar to inductive sensor40ofFIG.1. The inductive sensor interface circuitry can be provided in the inductive sensor unit1240proximate to the respective primary and secondary coils or elsewhere.

In order to meet certain safety requirements, a checker circuit, as may be part of the sensor1200or external to the sensor, can be provided to compare an indication of the first target angle from the first magnetic field sensor1214to an indication of the first target angle from the first inductive sensor1242and also to compare an indication of the second target angle from the second magnetic field sensor1216to an indication of the second target angle from the second inductive sensor1244. An error can be determined to have occurred if the comparison reveals greater than a predetermined deviation in the angle measurements from the magnetic field sensors1214,1216and the inductive sensors1242,1244, respectively.

A processing unit, as may be part of the sensor1200or external to the sensor, can be configured to determine a difference between the angle of the first target (e.g., target1116) and the angle of the second target (e.g., target1118) based on output signals of the magnetic field sensors1214,1216and/or output signals of the inductive sensors1242,1244. A torque applied to a first shaft (e.g., shaft1110) and/or to a second shaft (e.g., shaft1114) can be calculated based on the angle difference.

The sensor package1210can be electrically coupled to the PCB1236by wire bonds1218,1220. For example, the first magnetic field sensor1214can be electrically coupled to PCB1236by one or more wire bonds1218coupled to one or more PCB bond pads1224and the second magnetic field sensor1216can be electrically coupled to PCB1236by one or more wire bonds1220coupled to one or more PCB bond pads1226.

It will be appreciated that while the heterogeneous system1200includes a shared back bias magnet1230for both magnetic sensors1214,1216, in some implementations, the proximate targets (e.g., targets1116,1118) can be of a type to include portions optimized for magnetic sensing and for inductive sensing. For example, in embodiments, targets proximate to the sensors can be of the type shown inFIGS.8and9, in which the back bias magnet1230can be eliminated. In such embodiments, it may be advantageous to provide a ferromagnetic shield between the sensors1214,1216.

All references cited herein are hereby incorporated herein by reference in their entirety.

Having described preferred embodiments, which serve to illustrate various concepts, structures and techniques, which are the subject of this patent, it will now become apparent that other embodiments incorporating these concepts, structures and techniques may be used. Accordingly, it is submitted that the scope of the patent should not be limited to the described embodiments but rather should be limited only by the spirit and scope of the following claims.