Hollow shaft position sensing device for torque feedback

Abstract

A position sensing device for use in connection with torque feedback devices and force feedback devices. The positioning sensing device having magnetic position sensors radially positioned outward from a shaft centerline. The position sensing device optionally providing a central passageway through the torque feedback devices and force feedback devices.

Description

HOLLOW SHAFT POSITION SENSING DEVICE FOR TORQUE FEEDBACKCROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Application No. 63 / 603,720 filed on November 29, 2023, which is incorporated herein.BACKGROUND

[0002] Torque feedback devices (TFD), also known as tactile feedback devices, are commonly used on steering shafts and other rotatable shafts to provide torsional resistance and position measurement of the shaft. Torsional resistance in a TFD is provided by a brake, which can have a fixed torque (e.g., friction) or a controllable torque (e.g., magnetorheological controlled torque and / or or motor). A TFD with torsional resistance provided by both a magnetorheological torque and a motor is also known as a Force Feedback Device (FFD). Currently available torque feedback devices (TFD) commonly use a magnet and sensor on the shaft centerline to monitor changes in shaft rotational position. In the current systems, the TFD must be placed at the opposite end of the shaft from the torque input end. In current systems, the magnet is placed inside an electronics enclosure with sensors placed directly over the magnet. Unfortunately, this configuration limits application of the TFD and also limits the overall design of the system as bearings used to support the shaft must also accommodate the TFD. In particular, the current design precludes use of current TFD’s in applications that require through- shaft configurations.SUMMARY

[0003] In one embodiment the present disclosure provides a rotary position sensing device for use in a torque feedback device. The position sensing device comprising: a stationary frame having a first central opening, a printed circuit board supported by the stationary frame, the printed circuit board having a second central opening; a die configured to monitor changes in a magnetic field, the sensor located on the printed circuit board; a housing secured to the stationary frame, the housing having a lower end with a third central opening;a rotatable shaft rotatably secured within the housing, the rotatable shaft supports a ring magnet supported by the rotatable shaft.

[0004] In another embodiment, the present disclosure provides a rotary position sensing device. The rotary position sensing device includes a stationary frame, a magnetic position sensor secured directly or indirectly to the stationary frame, a rotatable shaft passing through the stationary frame and a magnet supported by the rotatable shaft. The location of the magnet having been selected to ensure that the magnetic flux produced by the magnet intersects the magnetic position sensor. The disclosed rotary position sensing device is suitable for use in force feedback

[0005] In another embodiment, the rotatable shaft of the position sensing device has a passageway extending from a first open end to a second open end. Thus, the passageway of the rotatable shaft and the first central opening, the second central opening, ring magnet and the third central opening define a central passageway passing through the position sensing device.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 depicts one embodiment of a Position Sensing Device (PSD) installed in a Torque Feedback Device (TFD) according to the present disclosure.

[0007] FIG. 2 is a sectional view of the TFD and PSD of FIG. 1.

[0008] FIG. 3 is a perspective view of the printed circuit board used within the PSD of FIG.1.

[0009] FIG. 4 is a partial exploded view of one embodiment of the disclosed PSD with hollow shaft installed in a TFD.

[0010] FIG. 5 is a graph depicting the variation in tangential and vertical orthogonal magnetic field strength due to rotation of a ring magnet within the PSD of FIG. 1.

[0011] FIG. 6 is a graph depicting the linearity error of the sensor(s) used within the PSD of FIG. 1 prior to the application of a calibration process.

[0012] FIG. 7 is a graph depicting the linearity error of the sensor(s) used within the PSD of FIG. 1 after application of a calibration process.

[0013] FIGS. 8A, 8B and 8C depicts the north and south poles of various magnet options suitable for use in the PSD disclosed herein.

[0014] FIG. 9 depicts the use of the PSD in an FFD.

[0015] FIGS. 10A and 10B depict the lines of magnetic flux and the position of the magnetic position sensor.

[0016] FIG. 11 depicts lines of magnetic flux produced by the brake portion of the TFD.

[0017] FIG. 12 demonstrates the benefit of a magnetic shield positioned between the brake portion of the TFD and the PSD.

[0018] FIG. 13 depicts a simplified example of a configuration for calibrating the PSD.DETAILED DESCRIPTION

[0019] The drawings included with this application illustrate certain aspects of the embodiments described herein. However, the drawings should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, as will occur to those skilled in the art with the benefit of this disclosure.

[0020] The present disclosure may be understood more readily by reference to these detailed descriptions. For simplicity and clarity of illustration, where appropriate, reference numerals may be repeated among the different figures to indicate corresponding or analogous elements. The following description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts may have been exaggerated to better illustrate details and features of the present disclosure. Also, the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting except where indicated as such.

[0021] Throughout this disclosure, the terms “about”, “approximate”, and variations thereof, are used to indicate that a value includes the inherent variation or error for the device, system, or measuring method being employed as recognized by those skilled in the art.

[0022] For the purposes of this disclosure the improved rotary position sensing system will be described in the application of a TFD; however, the improved position sensing configuration described herein will be equally useful in a force feedback device (FFD). As known to those skilled in the art, the primary difference between a TFD and a FFD is the incorporation of an electric motor into the FFD. One exemplary embodiment of the position sensing system positioned within an FFD is depicted in FIG. 9.

[0023] The improvement, as depicted in FIGS. 1-4, is configured for incorporation into a steering or control shaft, not shown, commonly found on vehicles. In most instances, aTFD provides resistive input to rotation of a shaft such as a steering shaft. When incorporated into a steering shaft, the TFD simulates the feel of a traditional mechanical steering system. TFD 10 includes a brake 50, located within housing 22 but not shown in detail, to provide resistive torque. TFD 10 also includes a position sensing device (PSD) 30 to sense the rotational position of shaft 32. The configuration of prior art TFDs do not permit incorporation of the TFD at all desired locations on the associated steering shaft and limits the selection of bearings which may be used to support the steering shaft and the TFD. Further, current TFDs do not allow for passage of wiring through the TFD. The various embodiments of PSD 30 disclosed herein overcome the deficiencies of currently available TFDs.

[0024] As depicted in FIGS. 1, 2 and 4, the position sensing device (PSD) 30 is an off- center position sensor that is positioned a distance away from the shaft centerline. In some embodiments, PSD 30 has an optional central passageway 40 extending through the entirety of TFD 10. The presence of central passageway 40 permits use of TFD 10 anywhere a through shaft application is desired or in applications requiring passage of electrical connections through a shaft. Thus, in these embodiments PSD 30 includes a hollow rotatable shaft 32. FIG. 9 provides one example where rotatable shaft 32 is a solid rod.

[0025] With reference to FIGS. 2-4, one embodiment of TFD 10 includes a housing 22, and a PSD 30. Located within housing 22 is brake 50. Stationary frame 20 is a housing which at the upper surface thereof has first end 42 of central passageway 40. Stationary frame 20 supports PSD 30 which includes a printed circuit board (PCB) 24 having a central opening 48. Stationary frame 20 and housing 22 are supported in fixed non-movable manner by a component of the vehicle or device in which TFD 10 is installed. Housing 22 has a lower opening 36 also referred to as a second open end 36. While described herein as separate components stationary frame 20 and housing 22 may be an integrated unit.

[0026] PSD 30 also includes rotatable shaft 32, a magnet 34, electrical connector 27, PCB 24, magnetic position sensor 26 in the form of an integrated circuit (IC) with die or dice 28, an electric connector 27, first end 42, optional central opening 40 and second open end 36. Thus, in most embodiments, magnetic position sensor 26 takes the form of integrated circuit 26 which supports die 28. Rotatable shaft 32 may be a single continuous shaft or multiple separate components supported within housing 22. As will be discussed in more detail below, PSD 30includes rotatable components in the form of magnet 34 supported by rotatable shaft 32 and stationary components such as PCB 24, magnetic position sensor 26 and die / dice 28 supported by stationary frame 20. As depicted in FIG. 8A, one suitable magnet is a ring magnet. In some embodiments, rotatable shaft 32 will include central passageway 40. Thus, as depicted in FIG. 2, magnetic position sensor 26 is positioned radially outward from magnet 34. As such, the configuration of magnetic position sensor 26 and magnet 34 do not interfere with the mounting of rotatable shaft 32 within bearings or other structural support components, not shown.

[0027] PCB 24 carries at least one magnetic position sensor 26 in the form of an integrated circuit (IC) 26. Each magnetic position sensor 26 contains at least one discrete integrated circuit, referred to herein as “die” 28. Each die 28 is suitable for monitoring flux changes of a magnetic field. One example of a suitable die 28 is a multi-axis magnetic position sensor. Typically, PCB 24 will carry multiple magnetic position sensors 26 with each magnetic position sensor 26 carrying at least one die 28. When the magnetic position sensor 26 carries more than one die 28, the term dice 28 will be used. Each magnetic position sensor 26 is placed an identical radial distance from central axis 44 of PCB 24. Thus, each package’s arrangement of sensor dice 28 will also be supported an identical distance from central axis 44. Central axis 44 also defines the central axis 44 of shaft 32 and when present central axis 44 of central passageway 40. Multiple position sensors can be used for redundancy and functional safety. For example, when 2 sensor dice 28 are placed on the same magnetic position sensor 26, then the computer processor can compare the 2 sensor outputs and stop or fault the outputs if the outputs are mismatched. If there are 4 sensor dice, then the computer processor can cross compare the sensor outputs and remain operational if one or 2 sensor dice have failed. Electrical connector 27, carried by PCB 24, provides for data communication between die 28 or dice 28 and a computer processor or similar device, not shown, responsible for managing operations of the device utilizing PSD 30. For example, the computer processor may be a vehicle’s computer processor or electronic control module responsible for multiple functions of the vehicle’s various systems. One suitable electrical connector 27 is an integrated 10 pin receptacle 27 as depicted in FIGS. 1 and 2.

[0028] The radial distance between sensor dice 28 and magnet 34 will vary with the magnetic field strength, size, and shape of the selected magnet and the sensitivity range of the sensor dice 28. The typical magnetic field strength range for the sensitivity of sensor 26 will be about 20 to 70 milliTesla (mT).

[0029] Rotatable shaft 32 is supported by and passes through stationary frame 20 and housing 22 in a manner which permits free rotation as required by the structure on which PSD 30 is used. As noted above, rotatable shaft 32 typically supports a ring magnet 34, also known as a doughnut shaped magnet. Ring magnet 34 is radially polarized. Thus, with reference to FIG. 8A, one radial half of the outer diameter of magnet 34 is deemed to be north 34a and the other radial half of the outer diameter is south 34b. The ring magnet geometry in Figure 8A can be used when measurement, i.e. position identification, over a full 360 degrees of rotation is required.

[0030] Further, some embodiments may not require a full 360° rotational range of rotatable shaft 32. In these embodiments, ring magnet 34 may have alternating north and south regions that are less than 180° in range as shown in FIG 8B. Alternatively, when the range of motion, i.e. position identification, monitored by PSD 30 is less than 360°, ring magnet 34 may be replaced by an arc magnet that covers the range of rotational motion and is divided into two or more north / south sections as shown in FIG 8C.

[0031] In FIGS. 10A and 10B, lines 38 represent the magnetic flux field produced by magnet 34 intersecting with magnetic position sensor 26. With reference to FIG. 10B, the configuration of magnetic position sensor 26 and magnet 34 ensure that the orthogonal components of the magnetic field vectors are substantially equal as they intersect magnetic position sensor 26 as shown in FIG. 5. The magnet sensor magnetic position sensor 26 is positioned to measure magnet field strength in the directions aligned with the shaft centerline (Z direction) and radially outward from the shaft centerline (X direction). The X and Z directions are orthogonal. Alternately, the magnetic position sensor 26 can measure in the XY plane (which is perpendicular to the shaft centerline (Z-direction). The X and Y directions are also orthogonal. The XZ and XY measurement axes for the magnetic sensor 26 are possible because the sinusoidal shapes of the magnetic field amplitudes between the sensed axes for these two options are phase shifted from each other by 90 degrees. In FIGS. 10A and 10B, substantially equal magnetic field strength in the X and Z directions is accomplished by positioning the magnetic position sensor 26 so that the magnetic flux as represented by lines 38 created by the ring magnet 34 is at an angle of approximately 45 degrees with respect to the shaft centerline combined with a field normalization performed during calibration. Closer to equal magnitudes for the two orthogonal magnetic fields used to determine magnet position will reduce the amount ofnormalization adjustment required to make the two measurements of equal magnitude. Less normalization adjustment means better signal to noise ratio, which leads to a lower linearity error before calibration. Lower linearity error before calibration typically translates to lower linearity error after calibration. Measuring in the XZ axes for the magnetic position sensor 26 axes may be preferred over the XY axes in some applications if the magnetic field amplitudes prior to calibration field normalization are closer to equal.

[0032] In some embodiments, magnet 34 will be positioned in the same plane as the ‘sensitive spot’ element(s) within magnetic position sensor 26 and die 28 or dice 28. However, in other embodiments magnet 34 centerline will be located slightly above or below the plane of the ‘sensitive spot’ elements within magnetic position sensor 26 and die 28 or dice 28. As known to those skilled in the art, each die 28 has a sensitive spot which detects the magnet flux field. This spot is generally above magnetic position sensor 26. The distance above or below is that amount which keeps the ratio of the orthogonal fields approximately equal. The positioning of the sensor depends upon the application magnet, and whether the position sensing will be based upon the X and Y, or X and Z orthogonal field pairs.

[0033] FIG. 5 graphically depicts the sinusoidally varying orthogonal raw horizontal and vertical magnetic fields at the magnetic position sensor 26. During calibration, the magnitudes of these two fields are normalized so that the maximum field strengths are equal for both axes, and the resultant field ratios are used to calculate the rotational angle of the magnet using an ATAN2 function. Following the field strength adjustment, the computer processor calculates the absolute position of the north and south poles of magnet 34 according to the formula where:Angle=ATAN2(Bl, B2) where: Bl is the magnetic field strength in one orthogonal axis; and, B2 is the magnetic field strength in the second orthogonal axis.For clarity the function ATAN2 is the two-argument arctangent of two numbers. Since the magnet is fixed to the shaft, the absolute rotary position of the shaft is determined from the magnet position measurement at the magnetic position sensor 26. The position sensor provides an absolute rotary position signal over an angle of up to 360 degrees, referenced to a preset ‘0°’ position that is set during calibration. This is in contrast to an incremental / relative position sensor, which is only able to provide a position signal relative to the position at which it was initiated. If power is removed and rotatable shaft 32 is not moved, the absolute position sensorwill return the same position output, i.e. the same position previously identified, when power is re-applied. In contrast, an incremental / relative position sensor lacks the ability to return to the previously identified position as the incremental / relative position sensor lacks a fixed reference point. Therefore, upon re-application of power, the incremental / relative position sensor will only identify the position corresponding to the last application of power. In other words, the incremental / relative position sensor will provide only a new zero reference for the sensor. However, for the absolute position sensor, if the shaft is moved between power cycles, the absolute position sensor will show the new shaft position relative to the fixed initial 0° location. Thus, PSD 30 provides the ability to determine an absolute rotary position. As used herein, the term absolute rotary position means the current location relative to the preset or predetermined zero position.

[0034] Calibration for each sensor die 28 within each magnetic position sensor 26 may be performed using a calibration rig prior to installation of PSD 30 by using an electric motor 74 to rotate shaft 32 and with the temporary addition of an external, high linearity reference position sensor 72. See FIG. 13 for a simplified arrangement for calibration. The calibration process includes linearizing the raw data with reference to external, high linearity reference position sensor 72. The calibration of die 28 or dice 28 includes the step of applying a multi-point linearization (calibration) to the angle of magnet 34 relative to each die 28 as measured by die 28 or dice 28 with respect to external, high linearity position sensor 72. The linearization (calibration) step adjusts the slope of the angle between each increment of each die 28 relative to magnet 34 to minimize linearity error. For the purposes of interpreting sensor data, one die 28 is designated as Sensor 1. Sensor 1 identifies the calibration reference point for magnet 34. The calibration reference point defines the preset 0° position for the absolute position reference. This calibration reference point is programmed into the device as part of the initial setup of the magnetic position sensor 26. Using the calibration reference point, an offset adjustment derived from external high linearity reference position sensor 72 ensures that the angular offset from the designated Sensor 1 to the other die 28 or dice 28 is correct after calibration. The difference between pre-calibration of die 28 or dice 28 compared to post-calibration is depicted in FIGS. 6 and 7. As depicted in FIG. 7, without calibration the linearity of die 28 or dice 28 is approximately + / - 8°; however, post-calibration, the linearity of die 28 or dice 28 is approximately + / - 1° over the full 360° absolute rotational range as depicted in FIG. 6.

[0035] The calibration process is performed as a final end-of line test during manufacturing and prior to field use of the completed PSD 30. In summary, the calibration process includes the following steps for each die 28 within each magnetic position sensor 26 within the PSD 30, the order of which may vary:(1) Place the PSD 30 on a calibration rig with a high accuracy, high linearity rotary position reference sensor 72 (hereafter referred to as the reference sensor).(2) Change the magnetic field at the magnetic position sensor(s) 26 by moving the magnet 34 by rotating shaft 32 through its rotational range. Then, using the magnetic position sensor(s) 26 measure the maximum and minimum magnetic field strengths of each axis over the rotational measurement range.(3) Apply a normalization multiplier to one of the axes to change the two field strengths (We'll refer to them as Bl and B2) to have close to equal maximum magnitudes.(4) Set the zero angle (0°) position used for absolute position measurement in the magnetic position sensor(s) 26 with respect to the calibration reference point on the reference sensor.(5) For the following steps, the magnetic position sensor(s) 26 will apply the function ATAN2(B1 / B2) to convert the field strengths in the two orthogonal directions to an absolute angle position which changes as the device is rotated.(5) Rotate the shaft of the device while recording the rotary positions reported by the magnetic position sensor(s) 26 under calibration and the reference sensor.(6) Compare the position measurements from the reference sensor and the magnetic position sensor(s) 26 and use this information to calculate compensation parameters to program into the device(s) to 'linearize' the device sensor(s) so that its(their) output(s) closely match(es) the reference sensor.(7) Store the position calibration parameters from the field strength normalization (step 3), the 0° (zero angle) absolute position reference (step 4), and linearization (step 6) in non-volatile memory in the magnetic position sensor 26.

[0036] The position sensor signal output can be provided directly from the die 28 or dice 28 to the associated computer processor as either a pulse width modulated (PWM) digital signal, or a ratiometric analog voltage signal. Alternatively, data produced by die 28 or dice 28 can be read using an internal serial digital interface into a computer processor, e g. an internal serialperipheral digital interface (SPI), then the position can be calculated and provided via an output interface such as a controller area network (CAN) serial communications interface, a Local Interconnect Network (LIN), a Single Edge Nibble Transmission (SENT), RS422, or any other suitable output interface. Thus, the radial position of magnet 34 relative to die 28 or dice 28 can be coordinated with torque applied by TFD 10 or FFD 60 to the steering shaft to ensure TFD 10 or FFD 60 generates the desired feedback or resistance to rotation of shaft 32 supporting PSD 30.

[0037] FIG. 9 depicts use of PSD 30 in an exemplary force feedback device (FFD) 60. FFD 60 includes a motor housing 62 with an electric motor 64 positioned within housing 62. Similar to brake 50, electric motor 64 engages shaft 32 to provide resistive force to rotational movement of shaft 32. Although FIG. 9 depicts electric motor 64 below electric brake 50, the positions may be reversed. Additionally, housings 22 and 62 may be separate housings secured to one another or a single housing containing both brake 50 and electric motor 64. Likewise, FIGS. 1, 2, 4 and 9 depict separate housings for PSD 30, brake 50 and electric motor 64; however, these housing may also be integrated. The final form of the housings being determined by the assembly process of PSD 30, TFD 10 and FFD 60. In most cases, PSD 30 will have a discrete stationary frame 20 secured to TFD body 22 or FFD housing 62. This arrangement allows for easier assembly and servicing of components.

[0038] In another embodiment, a magnetic flux field shield 25 may be associated with PSD 30. FIGS. 11 and 12 demonstrate the improvement provided by the addition of magnetic flux field shield 25. FIG. 11 demonstrates the potential for the flux field, represented by lines 39, produced by brake 50 or electric motor 64 to interfere with magnetic position sensor 26. As depicted in FIG. 12, shield 25 improves the accuracy of sensor outputs produced by dice 28 by blocking the flux field associated with brake 50 or electric motor 64 from reaching dice 28 carried by magnetic position sensor 26.

[0039] Embodiments using rotatable shaft 32 with central passageway 40, i.e. a hollow shaft, are suitable for applications requiring support of pass-through cables with connectors, not shown. For example, incorporation of rotatable shaft 32 having central passageway 40 into a steering shaft or other hollow shaft used on vehicle will improve connectivity of electrical components by permitting passage of wiring through the steering shaft and through PSD 30. Housing 22 also includes components suitable for applying resistive torque to hollow rotatable shaft 32. Such components may include a brake 50 actuated by electrical current, i.e. an electromagnetic brake.As known to those skilled in the art, brake 50 commonly includes an electromagnetic coil 52. However, for the purposes of this disclosure, the torque application components are not disclosed in detail herein and will not be further discussed.

[0040] PSD 30 will be installed on or incorporated into a shaft, e.g. a steering column of a vehicle, in a manner such that rotatable shaft 32 will rotate with the turning of the supporting shaft, not shown. Frequently, PSD 30 will be incorporated as part of a TFD 10 incorporated into a steering shaft in a “steer-by-wire” system. In such instances, rotatable shaft 32 will be hollow and as hollow rotatable shaft 32 rotates, stationary frame 20 retains die 28 or dice 28 in a fixed location(s) while hollow rotatable shaft 32 supporting ring magnet 34 rotates relative to die 28 or dice 28. Thus, rotation of hollow rotatable shaft 32 shifts the poles of magnet 34 relative to die 28 or dice 28. The resulting movement of the magnetic field produced by ring magnet 34 generates sinusoidally varying orthogonal horizontal and vertical magnetic fields.

[0041] As discussed above central opening of ring magnet 34 is axially aligned with central opening 36 of housing 22, central opening 42 of stationary frame 20 and PCB central opening 48. Additionally, hollow rotatable shaft 32 shares the same axial alignment as the foregoing components. Thus, in TFD 10 or FFD 60, which includes PSD 30, hollow rotatable shaft 32 defines an open central passageway 40 passing continuously from stationary frame central opening 42 to opening 36 of housing 22. Open central passageway 40 permits installation of PSD 30 as part of a hollow steering shaft or control yoke on a vehicle or other operator controlled system while allowing for passage of wires through the hollow steering shaft and TFD 10 which incorporates PSD 30. Thus, the configuration of PSD 30 enables the use of external bearings having greater load ratings to support the steering or control shaft 32. In prior installations, the bearing rating or size was dictated by the TFD or FFD. Thus, use of PSD 30 within hollow rotatable shaft 32 removes this limitation on bearing size from TFD 10 and FFD 60.

[0042] For embodiments utilizing rotatable shaft 32 with central passageway 40, the improvement provided by PSD 30 is the ability to pass a steering shaft or other control shaft as well as electrical connections through central passageway 40. Additionally, this configuration permits the selection of steering or control shaft bearings solely on the needs of the steering or control shaft. Further, this configuration allows for placement of PSD 30 at any convenientlocation along the length of the steering or control shaft. This configuration will be equally applicable to force feedback or torque feedback devices installed on hollow shaft controls.

[0043] Other embodiments of the present invention will be apparent to one skilled in the art. As such, the foregoing description merely enables and describes the general uses and methods of the present invention. Accordingly, the following claims define the true scope of the present invention.

Claims

What is claimed Is:

1. A position sensing device comprising: a stationary frame (20); a magnetic position sensor (26) fixedly secured within the stationary frame; a rotatable shaft (32) passing through the stationary frame; a magnet (34) supported by the rotatable shaft, the position of the magnet selected to ensure that magnetic flux produced by the magnet intersects the magnetic position sensor.

2. The position sensing device of claim 1, wherein the rotatable shaft defines an axis and wherein the magnetic position sensor is in a plane perpendicular to the axis defined by the rotatable shaft and wherein at least a portion of the magnet is in the same plane as the magnetic position sensor.

3. The position sensing device of claim 1, wherein the rotatable shaft defines an axis and wherein the magnet is positioned such that the magnetic position sensor experiences a magnetic field strength of about 20 milliTeslas to about 70 milliTeslas.

4. The position sensing device of claim 1, wherein the magnet produces a magnetic field having magnetic field vectors with orthogonal components and wherein the position of the magnetic position sensor ensures that the orthogonal components are substantially equal upon intersecting with the magnetic position sensor.

5. The position sensing device of claim 4, wherein a first orthogonal component and a second orthogonal component are phase shifted by approximately 90 degrees from each other.

6. The position sensing device of claim 1, wherein the rotatable shaft has a central passageway extending from a first open end of the rotatable shaft to a second open end of the rotatable shaft.

7. The position sensing device of claim 1, wherein the configuration of the magnet and the magnetic position sensor provides position sensing range of 360 degrees.

8. The position sensing device of claim 7, wherein the magnet is a ring magnet having alternating north and south regions with each north and south region being 180 degrees and wherein the configuration of the ring magnet and the magnetic position sensor provides position a sensing range of 360 degrees.

9. The position sensing device of claim 7, wherein the magnet is a ring magnet having alternating north and south regions with each north and south region being less than 180 degreesand wherein the configuration of the ring magnet and the magnetic position sensor provides position a sensing range less than 360 degrees.

10. The position sensing device of claim 1, wherein the magnet is an arc magnet having alternating north and south regions and the arc magnet has at least one north and at least one south section.

11. The position sensing device of claim 1, wherein the magnetic position sensor is an integrated circuit positioned a radial distance from the central axis.

12. The position sensing device of claim 1, wherein the magnetic position sensor is an integrated circuit and the integrated circuit carries at least one die suitable for monitoring changes of a magnetic field.

13. The position sensing device of claim 1, wherein the magnetic position sensor is an integrated circuit capable of sensing flux changes of a magnetic field in two orthogonal directions.

14. The position sensing device of claim 1, where the magnetic position sensor provides an absolute rotary position of the shaft with respect to a reference point.

15. A method of calibrating a position sensing device, the method comprising: providing a position sensing device, wherein the position sensing device comprises: a stationary frame (20); a magnetic position sensor (26) fixedly secured within the stationary frame; a rotatable shaft (32) passing through the stationary frame; a magnet (34) supported by the rotatable shaft, the position of the magnet selected to ensure that magnetic flux produced by the magnet intersects the magnetic position sensor as the magnet moves past the magnetic position sensor; providing an external, high linearity reference position sensor; using the high linearity reference position sensor, identify a calibration reference point and absolute position relative to the magnet; rotating the rotatable shaft through different angles thereby changing the shaft rotary position and strength of the magnet flux intersecting the magnetic position sensor; setting the zero angle position for the magnetic position sensor with respect to the calibration reference point;performing a linearization by comparing the magnetic position sensor with the external, high linearity reference position sensor; saving the zero angle position and linearization calibration values in non-volatile memory of the magnetic position sensor.

16. The method of calibrating a position sensing device of claim 15, the method further comprising: a magnetic position sensor with two orthogonal axes; performing a field strength normalization calibration of the two orthogonal measurement axes within the magnetic position sensor; saving the field strength normalization calibration values in non-volatile memory of the magnetic position sensor.

17. A torque feedback device (10) comprising: a stationary housing 22, the stationary housing having a lower opening(36); an electromagnetic brake positioned within the housing the electromagnetic brake having a central passageway (40); a position sensing device, the position sensing device comprising: a stationary frame (20) having an upper opening (42); a magnetic position sensor (26) fixedly secured within the stationary frame; a rotatable shaft (32) passing through the stationary frame the rotatable shaft defining a central axis, the rotatable shaft extending outward through the upper opening and the lower opening; a magnet (34) supported by the rotatable shaft, the position of the magnet selected to ensure that magnetic flux produced by the magnet intersects the magnetic position sensor.

18. The torque feedback device of claim 17, wherein the rotatable shaft defines an axis and wherein the magnetic position sensor is in a plane perpendicular to the axis defined by the rotatable shaft and wherein at least a portion of the magnet is in the same plane as the magnetic position sensor.

19. The torque feedback device of claim 17, wherein the rotatable shaft defines an axis and wherein the magnet is positioned such that the magnetic position sensor experiences a magnetic field strength of about 20 milliTeslas to about 70 milliTeslas.

20. The torque feedback device of claim 17, wherein the magnet produces a magnetic field having magnetic field vectors with orthogonal components and wherein the position of the magnetic position sensor ensures that the orthogonal components are substantially equal upon intersecting with the magnetic position sensor.

21. The torque feedback device of claim 20, wherein a first orthogonal component and a second orthogonal component are phase shifted by approximately 90 degrees from each other.

22. The torque feedback device of claim 17, wherein the rotatable shaft has a central passageway extending from a first open end of the rotatable shaft to a second open end of the rotatable shaft.

23. The torque feedback device of claim 17, wherein the configuration of the magnet and the magnetic position sensor provides position sensing range of 360 degrees.

24. The torque feedback device of claim 23, wherein the magnet is a ring magnet having alternating north and south regions with each north and south region being 180 degrees and wherein the configuration of the ring magnet and the magnetic position sensor provides position a sensing range of 360 degrees.

25. The torque feedback device of claim 23, wherein the magnet is a ring magnet having alternating north and south regions with each north and south region being less than 180 degrees and wherein the configuration of the ring magnet and the magnetic position sensor provides position a sensing range less than 360 degrees.

26. The torque feedback device of claim 17, wherein the magnet is an arc magnet having alternating north and south regions and the arc magnet has at least one north and at least one south section.

27. The torque feedback device of claim 17, wherein the magnetic position sensor is an integrated circuit positioned a radial distance from the central axis.

28. The torque feedback device of claim 17, wherein the magnetic position sensor is an integrated circuit and the integrated circuit carries at least one die suitable for monitoring changes of a magnetic field.

29. The torque feedback device of claim 17, wherein the magnetic position sensor is an integrated circuit capable of sensing flux changes of a magnetic field in two orthogonal directions.

30. The torque feedback device of claim 17, where the magnetic position sensor provides an absolute rotary position of the shaft with respect to a reference point.

31. The torque feedback device of claim 17, wherein the rotatable shaft is hollow and wherein the lower opening, the rotatable shaft and the upper opening define a central passageway through the torque feedback device.

32. The torque feedback device of claim 17, further comprising a magnetic shield (25) positioned between the electromagnetic brake and the magnetic sensor.

33. A force feedback device (60) comprising: a stationary housing 22, the stationary housing having a lower opening(36); an electromagnetic brake positioned within the housing the electromagnetic brake having a central passageway (40); an electric motor (64) positioned within the stationary housing, the electric motor having a central passageway (40); a position sensing device, the position sensing device comprising: a stationary frame (20) having an upper opening (42); a magnetic position sensor (26) fixedly secured within the stationary frame; a rotatable shaft (32) passing through the stationary frame the rotatable shaft defining a central axis, the rotatable shaft extending outward through the upper opening and the lower opening; a magnet (34) supported by the rotatable shaft, the position of the magnet selected to ensure that magnetic flux produced by the magnet intersects the magnetic position sensor.

34. The force feedback device of claim 32, wherein the rotatable shaft defines an axis and wherein the magnetic position sensor is in a plane perpendicular to the axis defined by the rotatable shaft and wherein at least a portion of the magnet is in the same plane as the magnetic position sensor.

35. The force feedback device of claim 33, wherein the rotatable shaft defines an axis and wherein the magnet is positioned such that the magnetic position sensor experiences a magnetic field strength of about 20 milliTeslas to about 70 milliTeslas.

36. The force feedback device of claim 33 wherein the magnet produces a magnetic field having magnetic field vectors with orthogonal components and wherein the position of the magnetic position sensor ensures that the orthogonal components are substantially equal upon intersecting with the magnetic position sensor.

37. The force feedback device of claim 36, wherein a first orthogonal component and a second orthogonal component are phase shifted by approximately 90 degrees from each other.

38. The force feedback device of claim 33, wherein the rotatable shaft has a central passageway extending from a first open end of the rotatable shaft to a second open end of the rotatable shaft.

39. The force feedback device of claim 33, wherein the configuration of the magnet and the magnetic position sensor provides position sensing range of 360 degrees.

40. The force feedback device of claim 39, wherein the magnet is a ring magnet having alternating north and south regions with each north and south region being 180 degrees and wherein the configuration of the ring magnet and the magnetic position sensor provides position a sensing range of 360 degrees.

41. The force feedback device of claim 39, wherein the magnet is a ring magnet having alternating north and south regions with each north and south region being less than 180 degrees and wherein the configuration of the ring magnet and the magnetic position sensor provides position a sensing range less than 360 degrees.

42. The force feedback device of claim 33, wherein the magnet is an arc magnet having alternating north and south regions and the arc magnet has at least one north and at least one south section.

43. The force feedback device of claim 33, wherein the magnetic position sensor is an integrated circuit positioned a radial distance from the central axis.

44. The force feedback device of claim 33, wherein the magnetic position sensor is an integrated circuit and the integrated circuit carries at least one die suitable for monitoring changes of a magnetic field.

45. The force feedback device of claim 33, wherein the magnetic position sensor is an integrated circuit capable of sensing flux changes of a magnetic field in two orthogonal directions.

46. The force feedback device of claim 33, where the magnetic position sensor provides an absolute rotary position of the shaft with respect to a reference point.

47. The force feedback device of claim 33, wherein the rotatable shaft is hollow and wherein the lower opening, the rotatable shaft and the upper opening define a central passageway through the torque feedback device.

48. The force feedback device of claim 33, further comprising a magnetic shield (25) positioned between the electromagnetic brake and the magnetic sensor.

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