Handwheel actuator assembly

Abstract

A handwheel actuator assembly (600) for a steer-by-wire system in a vehicle is disclosed. The assembly (600) includes a steering wheel (601) and a feedback torque generator. The steering wheel (601) has at least one handgrip portion rotatable about a rotation axis of the steering wheel (601) and capable of being gripped by a driver; and a hub (602) supporting the handgrip portion. The feedback torque generator includes an electric motor having a stator (609) and a rotor (610). The rotor (610) is directly or indirectly fixed to the hub of the steering wheel (601) and rotates with the hub, while the stator (609) is fastened to a fixed portion of the vehicle body such that the stator cannot rotate relative to the vehicle body. The motor includes a brushless permanent magnet vernier motor.

Description

[0001] This invention relates to a handwheel actuator assembly for a vehicle steer-by-wire system.

[0002] In traditional steering systems, the steering wheel rotates the steering shaft, which in turn connects to a steering gear. The steering gear converts the rotation of the steering wheel into left and right movements of a steering rack mechanically connected to the wheels. In contrast, in a steer-on-wire system, there is no direct mechanical connection between the steering wheel and the wheels.

[0003] In a steering-by-wire assembly, the steering shaft is omitted, or at least the steering wheel is not mechanically connected to the steering gear. Instead, one or more electric motors are used to steer the travel wheels in response to control signals, which in turn respond to the movement of the steering wheel. The motors apply torque to a portion of the steering assembly in response to control signals that depend on the position or movement of the steering wheel, which forms part of an assembly known as the handwheel actuator assembly.

[0004] To improve the user experience, and especially to provide the driver with appropriate tactile feedback regarding the forces at the tire-road interface, force feedback to the vehicle driver is known by applying torque to the steering wheel of the handwheel actuator assembly. This feedback torque can be applied in various ways, such as through an electric motor, or through the arrangement of springs, shock absorbers, and brakes. This feedback torque can be used to allow the driver to feel the wheels hitting stones or potholes, or to reduce the steering wheel feel when the tires are traveling on low-friction surfaces, such as wet or icy surfaces.

[0005] In this specification, the term "steering wheel" should be interpreted broadly to encompass both a conventional wheel with a generally circular, continuous or discontinuous edge, supported by a hub and which the driver can grip, and a steering handle, such as a pair of opposing handgrips supported by a hub that can rotate around a circular path, similar to the arrangement of a joystick commonly used in aircraft. The handgrips and hub can be configured, for example, in a W, M, or U shape. In their respective cases, typically, feedback torque is applied to the portion gripped by the driver via the hub by connecting the hub to a feedback torque generator.

[0006] According to a first aspect, the present invention provides a handwheel actuator assembly for a steer-by-wire system of a vehicle, the assembly comprising:

[0007] A steering wheel having at least one handgrip rotatable about a rotation axis of the steering wheel and capable of being gripped by a driver, the steering wheel having a hub supporting the handgrip; and

[0008] A feedback torque generator includes an electric motor having a stator and a rotor, wherein the rotor is directly or indirectly fixed to the hub of the steering wheel and rotates with the hub, and the stator is fastened to a fixed part of the vehicle body such that the stator cannot rotate relative to the vehicle body.

[0009] The feature is that the motor includes a brushless permanent magnet vernier motor.

[0010] The vernier motor may include a radial motor, and most preferably an inverted motor, wherein the rotor has a larger diameter than the stator. The rotor and stator share a common axis of rotation and face each other across a circumferential air gap. The stator may include a plurality of radially outwardly extending slots in which stator windings are placed. This is advantageous compared to non-inverted motors because the slots of an inverted motor are easier to wind. The use of a radially outer rotor is also advantageous because the individual poles are larger in the circumferential direction compared to a non-inverted motor, which simplifies manufacturing.

[0011] The motor and steering wheel share a common axis of rotation.

[0012] Alternatively, a vernier motor may include an axial motor in which the rotor and stator are not concentric but have substantially the same radius, and the rotor and stator are arranged side by side, spaced apart from each other along a common axis of rotation, so as to define an air gap between the rotor and stator.

[0013] Whether the rotor is directly or indirectly fixed to the hub, the connection between the rotor and the hub provides a direct 1:1 transmission ratio between the two, so the hub rotates at the same speed as the motor's rotor.

[0014] The stator of the vernier motor may include an annular assembly with a hollow center defining a space within the stator, through which additional components of the handwheel actuator assembly pass, or within the space.

[0015] The additional components may include a wiring harness connected to a driver information display that shows information to the driver during use. This information may be about vehicle status, such as speed and location, or infotainment information, such as the music track being played or the title of the radio station being broadcast.

[0016] The driver information display may include a housing and an electronic display located within the housing. The driver information display may be located within a space defined by at least one of the following: a steering wheel, a gap between the steering wheel and the motor, and a space within an annular stator.

[0017] The stator can be secured to a stator support portion, which can be fastened to a fixed portion of the vehicle body during use. The stator support portion may include a housing for the motor, which can be fastened to a vehicle bulkhead or crossbeam during use, the crossbeam extending across the vehicle between the driver and the bulkhead, typically behind the vehicle's dashboard.

[0018] The motor in the handwheel actuator incorporated into the first aspect of the invention includes a permanent magnet vernier motor. Those skilled in the art will understand how a motor, unlike a conventional motor, can be identified as a vernier motor based on the number of stator teeth and rotor pole pairs, and their topological arrangement. A. Toba and TA Lipo provided an excellent summary of the main characteristics of vernier motors in their paper entitled “A Novel Dual-Excited Permanent Magnet Vernier Motor” (Conference Proceedings, 34th IAS Annual Meeting, 1999, pp. 2539-2544). Further description of vernier motors, relating to vernier motors without permanent magnets, was given in an earlier paper entitled “Vernier Motors and Their Design” (IEEE Trans. On Power Apparatus and Systems, Vol. 82, No. 66, 1906, pp. 343-349).

[0019] The rotor of a permanent magnet motor typically comprises multiple magnets, which are positioned such that... p r A magnetic field is formed within the air gap between the rotor and stator, with each pole pair. The stator has multiple radially facing teeth and a corresponding number of slots. N s In a permanent magnet vernier motor, the number of rotor pole pairs... p r and the number of stator slots Ns Related to equation (1), where p s It is the number of pole pairs generated by the stator winding when energized.

[0020] p r = N s ± p s (1)

[0021] In a preferred arrangement, the motor includes a stator with six teeth and a rotor with five pole pairs. The stator windings are arranged such that the magnetic field they generate has one north pole and one south pole, i.e., one pole pair, and therefore... p s = 1.

[0022] In another preferred arrangement, the motor includes a rotor with 11 pole pairs and a single pole pair magnetic field generated by a stator with 12 teeth.

[0023] A motor can have three phases, but it can also have fewer or more phases.

[0024] The rotor or stator may be skewed or not.

[0025] The reader will realize that the torque feedback actuator of the present invention shares a common axis of rotation with the steering wheel, so that the two move together about this axis at the same speed.

[0026] The hub can be fastened to the rotor via a short shaft, the axis of rotation of which lies on the axis of rotation of both the hub and the rotor. The short shaft can pass through the space defined by the center of the stator or extend only partially into that space.

[0027] The steering wheel hub may include a bushing fitted to the end of a short shaft. Splines on the short shaft may engage with complementary splines on the bushing to prevent relative rotation between the short shaft and the steering wheel.

[0028] The motor can be offset axially from the steering wheel.

[0029] The short shaft can be supported by at least one, and preferably two, bearing assemblies. The bearing assembly can be located on the side of the motor closest to the driver or on the side furthest from the motor. A single bearing assembly can be located on each side of the motor.

[0030] In cases where two or more bearing assemblies are located on the side of the motor closest to the driver, a shield supporting one or more column switches and / or a rotary (“airbag”) connector to the steering wheel can surround the short shaft.

[0031] The short shaft can be fixed to a connector, which in turn is fixed to the rotor. In this arrangement, the steering wheel is indirectly connected to the rotor via the short shaft and then via the housing. The short shaft can be fixed to the bracket using an interference fit or by welding the housing to the short shaft, or by using adhesives, nails, riveting, screws, etc. Those skilled in the art will recognize that this is not an exhaustive list. The splines on the short shaft can connect to the splines on the bracket. Alternatively, the bracket can be integral with the short shaft.

[0032] The bearing supporting the short shaft can be shafted to a housing, which includes a first cylindrical can-shaped member extending axially along a portion of the short shaft.

[0033] The housing may include radial end walls that connect a first cylindrical can to a larger second cylindrical can surrounding the outer periphery of the rotor. The larger can may be connected to another radial end wall on the side of the motor opposite to the first radial end wall of the housing.

[0034] The first cylindrical can-shaped component can be located on the side where the motor bearing is located.

[0035] The housing may surround both the motor and the bracket that secures the motor to the short shaft.

[0036] The component may include a travel limiter comprising a first portion fixed relative to the vehicle body, the first portion engaging with a second portion fixed to the rotor when the rotor of the motor reaches a predetermined end of its rotational stroke during use. Thus, in this arrangement, the rotor, and therefore the steering wheel, can be limited to rotation less than 360 degrees.

[0037] The first part may include a radially inwardly projecting lug on the inner side of the outer wall of the housing, the lug engaging with a corresponding stop on the rotor.

[0038] The stop may include a radially protruding portion of the rotor, or an end face of a circumferential groove in which the lug of the first portion is located, extending partially around the circumference of the rotor.

[0039] In an alternative arrangement, the short shaft can be omitted. Alternatively, the steering wheel hub can be directly mounted to the motor rotor, or it can be mounted to the motor rotor via a mounting bracket.

[0040] The rotor may be supported by one or more bearing assemblies, which are shafted to the motor housing. A bearing assembly may be located on each side of the motor, i.e., on the side facing away from the steering wheel and the side facing the steering wheel.

[0041] The rotor may include portions that project downwards on each side of the rotor to engage with bearing assemblies. One of these portions may be connected to the mounting bracket of the steering wheel.

[0042] The motor housing can surround the outer periphery and sides of the motor, and two bearing assemblies can be pivotally connected to the housing. The housing provides the connection between the handwheel actuator assembly and the vehicle's fixed parts.

[0043] The arrangement without a short shaft leaves space through the center of the motor to allow for wiring to be connected to any additional components located on the driver-side side of the motor, within the space defined by the steering wheel grips and hub.

[0044] The mounting bracket can be attached to the end of the hollow space. The mounting bracket can be attached after the handwheel is attached to the motor. The mounting bracket can support components located at the center of the handwheel that do not rotate when the steering wheel is turned. These components may include one or more components selected from the following list: driver's airbag, control switches, and driver's display.

[0045] The applicant envisions that the additional components may include or contain a display. The support will not move relative to the motor, but the entire motor / handwheel actuator assembly may be mounted on the support to allow it to retract away from the driver.

[0046] It is conceivable that handwheel devices could be used in vehicles with an autonomous driving mode. In this mode, the vehicle could drive itself (steering, accelerating, and braking) without any driver input.

[0047] An angle sensor can be installed, which outputs an angle signal indicating the angular position of the steering wheel.

[0048] With a short shaft in place, the angle sensor can be fixed to the end of the short shaft furthest from the steering wheel. The angle sensor may, for example, include a target magnet fixed to the short shaft or steering wheel and at least one sensing element capable of determining the element's position; however, other sensors can be used. A Hall effect sensor can be used as a suitable sensing element.

[0049] Without a short axis, the angle sensor may include a magnetic element ring fastened to the rotor or steering shaft, or another part that rotates together with at least one sensing element that detects the movement of the magnetic ring.

[0050] According to a second aspect, the present invention provides a handwheel actuator assembly for a steer-by-wire system of a vehicle, the assembly comprising:

[0051] A steering wheel having at least one handgrip rotatable about a rotation axis of the steering wheel and capable of being gripped by a driver, the steering wheel having a hub supporting the handgrip; and

[0052] A feedback torque generator includes an electric motor having a stator and a rotor, wherein the rotor is directly or indirectly fixed to the hub of the steering wheel and rotates with the hub, and the stator is fastened to a fixed part of the vehicle body such that the stator cannot rotate.

[0053] The motor is characterized in that it comprises a ring motor having a hollow center, and the additional non-rotating component of the handwheel actuator assembly is located within the hollow center of the stator.

[0054] The hollow center of the motor can accommodate additional components, including wiring harnesses. These additional components can be connected to a driver display / switch / airbag located within a space at least partially defined by the interior of the steering wheel. The hub can include one or more concave spokes extending around the exterior of the display to directly or indirectly connect the grip portion to the motor rotor.

[0055] The additional component may include a portion of the connector that passes through the motor.

[0056] The hollow center of the motor, or the space defined by the steering wheel, or both, can accommodate an airbag that does not rotate with the steering wheel. The airbag may be located partly within the hollow center of the motor and partly within the space defined by the steering wheel.

[0057] Additional components may include a fixed hub that supports a display, airbag, or other item within the space defined by the steering wheel.

[0058] The handwheel actuator assembly of the second aspect may include any features previously described with respect to the handwheel actuator assembly of the first aspect of the invention.

[0059] Three embodiments of a handwheel actuator assembly falling within the scope of at least one aspect of the invention will now be described by way of example only.

[0060] Figure 1 This is a side cross-sectional view of a first embodiment of a handwheel actuator assembly according to at least one aspect of the present invention;

[0061] Figure 2 This is a side cross-sectional view of a second embodiment of a handwheel actuator assembly according to at least one aspect of the present invention;

[0062] Figure 3 This is a side cross-sectional view of a third embodiment of a handwheel actuator assembly according to at least one aspect of the present invention;

[0063] Figure 4 This is a cross-sectional view of an inverted radial brushless permanent magnet vernier motor with 6 stator teeth and 5 rotor pole pairs;

[0064] Figure 5 This is a cross-sectional view of an inverted radial brushless permanent magnet vernier motor with 12 stator teeth and 11 rotor pole pairs;

[0065] Figure 6 This is a side cross-sectional view of a support assembly used to mount a handwheel actuator assembly to the vehicle body so that the handwheel actuator assembly can retract in the event of a collision.

[0066] Figure 7This is a side cross-sectional view of a fourth embodiment of a handwheel actuator assembly according to at least one aspect of the present invention, the handwheel actuator assembly including an axial motor; and

[0067] Figures 8 to 10 This is a cross-sectional view of an alternative wiring layout for an inverted radial brushless permanent magnet vernier motor with 12 stator teeth and 11 rotor pole pairs.

[0068] The attached diagram Figures 1 to 3 Several different embodiments of the handwheel actuator assembly according to the invention are illustrated. A common feature of each embodiment is an inverted permanent magnet vernier motor of the annular rotor type, which rotates about a fixed inner stator. Additionally, a common feature of each motor is the use of a hollow annular stator that defines a channel within the stator's boundaries, thereby allowing one or more components to be positioned within the motor's stator or to extend axially through the motor's stator.

[0069] The attached diagram Figure 4 and Figure 5 The paper illustrates two particularly advantageous motor topologies for radial motor arrangements, and Figure 8 , Figure 9 and Figure 10 It shows Figure 4 Various alternative winding arrangements for motors. Figure 4 and Figure 5 The differences between these motors lie in the number of stator teeth and rotor pole pairs, as well as other corresponding variations in the motor windings. In their respective cases, the motors in the examples all feature a three-phase, full-pitch wound stator design. Figure 4 The image shows a motor 100 having a stator 103, six stator teeth 101, and five rotor pole pairs 102. Figure 5 A motor 200 is shown, having a stator 201 and a rotor 202, and having 12 stator teeth 203 and 11 pole rotor pairs 204.

[0070] The motor can be wound in a variety of configurations. Figure 8 An arrangement of the phase windings of motor 300 is shown. The interconnects for one phase (marked with arrows) are shown with solid black lines, while the interconnects for the other two phases are marked with cross lines or dotted lines, respectively. Figure 9 A similar 22-pole, 12-slot vernier motor 400 is shown, but with a double-layer concentrated (single-tooth) winding arrangement. While producing a lower first-harmonic (i.e., one north and one south pole) air-gap magnetic field compared to a full-pitch winding arrangement, the end windings do not overlap. This saves space at the stator ends. It also reduces the likelihood of windings from different phases coming into contact with each other. This contributes to improved reliability and reduces the likelihood of problems caused by phase-to-phase short circuits. Figure 10The diagram illustrates an alternative winding arrangement for the pole-slot combination of a motor 500 containing a first harmonic in its magnetic field: a single-layer winding. Each slot has only one winding. A single-layer winding provides inherent physical spacing between the coils of different phases within the slot. This saves space that would otherwise be occupied by an isolation barrier. Typically, such isolation barriers or physical spacing are desired in motors used in safety-critical applications such as electric power steering. Reducing the number of coils by half compared to a double-layer winding further reduces the number of connections that may be required and allows for easier utilization of a variety of different coil assembly methods.

[0071] Other motor topologies can be used. (See attached diagram.) Figure 7 In another arrangement shown, an axial motor can be used instead of a radial motor.

[0072] The main components of a vernier motor are permanent magnets mounted on the outer peripheral surface of an annular support that defines the rotor; however, the magnets may also be embedded or buried within or beneath the rotor surface. These magnets face radially toward the rotor axis, and therefore toward the stator. The magnets are equidistant from each adjacent magnet around the rotor.

[0073] The stator includes an annular support or guard iron located within the rotor, thus the rotor has a larger radius than the stator. The annular stator support defines a set of stator teeth on which the stator windings are wound. The stator teeth are equidistant from each adjacent stator tooth around the guard iron. An air gap is defined between the stator and the rotor.

[0074] The applicant has recognized that vernier motors are well-suited for handwheel actuator assemblies because they can generate high torque at low speeds, and for a given size and cost, no mechanical transmission between the motor and the steering wheel is required.

[0075] Figure 2 A first embodiment of a handwheel actuator assembly 600 for a steer-by-wire system is shown. The assembly includes a steering wheel 601 having a relatively thin, generally circular rim that defines a handgrip portion rotatable about the steering wheel's axis of rotation. The rim can be gripped by the driver in a conventional manner with one or both hands, and the driver can rotate the steering wheel about a central axis of rotation. Within the scope of the invention, many other forms of handgrip can be provided, where the steering wheel does not need to have a circular rim.

[0076] The steering wheel 601 has a hub 602 or reinforcement comprising a single concave arm or spoke, a first end of which is connected to an edge and a second end to a bushing 603. Multiple spokes may be provided depending on the style of the grips and the required rigidity of the steering wheel, and the invention is not limited to a single spoke. The bushing 603 is located on the axis of rotation of the steering wheel 601 and supports the grip portion. A notch in the bushing 603 has a set of radially inward splines or other positioning features and is conventionally pressed against the end of a short shaft 604 having a set of complementary radially outward splines to secure the steering wheel to the steering axis. The splines ensure that rotation of the steering wheel 601 produces a corresponding rotation of the short shaft 604. A nut 605 prevents the steering wheel hub from being accidentally pulled away from the short shaft by the driver.

[0077] like Figure 1 As can be seen, the short shaft 604 extends along the axis of rotation of the steering wheel in a direction away from the vehicle driver. This shaft passes through a housing 606 having a cylindrical can-shaped member 606a, which carries a pair of bearing assemblies 607, 608 on its inner wall. These bearing assemblies support the short shaft at axially spaced locations. One end of the cylindrical can-shaped member 606a is connected to a radially extending end wall 606b of the housing, which in turn connects at its outermost periphery to a second cylindrical can-shaped member 606c. The second can-shaped member 606c extends away from the first can-shaped member and defines a portion of the housing containing a feedback torque generator, including a vernier motor. The motor may be... Figure 4 It can be the type shown in 5, or some other configuration of the vernier motor.

[0078] The stator 609 of the motor is fixed to the housing 606, and the rotor 610 of the vernier motor is fixed to the connector 611, which is attached to the short shaft on the side of the motor closest to the steering wheel. When the rotor 610 rotates, the connector 611, and consequently the short shaft 604, rotates, which ultimately causes the steering wheel to rotate. Thus, applying torque to the motor can be used to turn the steering wheel or to apply torque to partially resist the torque applied to the steering wheel by the driver.

[0079] An angle sensor 612 is also shown, which determines the angular position of the steering wheel based on the angle of the short axis 604. The sensor 612 is fixed to the end of the short axis furthest from the steering wheel. A cable carrying the signal output from the sensor passes away from the steering wheel through a hollow motor for connection to circuitry located elsewhere in the vehicle. This circuitry includes a motor controller that controls a motor drive circuit. The motor drive circuitry applies an appropriate drive current to the motor windings, causing the motor to apply the required feedback torque to the steering wheel.

[0080] Figure 1The diagram also shows a travel limiter 613 that limits the angular movement range of the steering wheel 601 to less than one full revolution. This travel limiter includes a lug on the radially inner wall of the second canister 606c that engages with a radially outwardly projecting lug on the rotor.

[0081] Figure 1 The handwheel actuator assembly 600 positions the steering wheel 601 axially at a distance from the motor, and this conveniently provides space within which a cover 614 housing one or more items for the steering column switching device can be positioned. These items may include an indicator switch, a wiper switch, or possibly a gear selector switch. A switch is any user-operable device capable of altering or generating electrical control signals.

[0082] Figure 2 A second embodiment of the handwheel actuator 700 is shown. This second embodiment includes a number of... Figure 1 The same components are used in the first embodiment, and for convenience, the same reference numerals are used for these components. The description of the function of the components in the first embodiment also applies to the second embodiment, and therefore will not be repeated for efficiency.

[0083] The main difference between the second embodiment and the first embodiment is that the short shaft 604 extends through the motor and is supported by two bearing assemblies 607 and 608, which are located on the side of the motor opposite to the steering wheel.

[0084] This change allows the rotor to connect directly to the steering wheel bushing, instead of the short shaft 604. This provides a more compact axial assembly, allowing for minimizing or eliminating the space between the steering wheel and the motor, as shown in the figure. In effect, this allows the motor rotor to connect directly to the steering wheel hub.

[0085] Figure 3 A third embodiment of the handwheel actuator assembly 800 is shown. Similarly, it uses... Figure 1 and Figure 2 The same reference numerals are used to identify the same parts.

[0086] In the third embodiment, the short shaft is not used, and the space at the center of the motor stator 609 is enlarged. The steering wheel 601 is secured to a portion of the motor rotor 610 by a spacer 801 that engages with the connector portion 802. The steering wheel bushing may also be omitted.

[0087] Figure 3The layout leaves an open space enclosed by the steering wheel rim and hub, as well as the interior of the motor where additional components can be positioned. As shown, the additional components include a display housing 804, which houses an electronic driver display. The display in use presents information to the driver, such as vehicle status information. A connector 805 for the display connects to a wiring harness 806 that passes through the center of the motor.

[0088] The display housing is secured in place by a bracket 803, which is fixed to the support of the motor stator. The display 804 can be removed from the bracket, and the steering wheel can also be removed from the rotor. The mounting bracket can be easily accessed from the driver-facing side of the motor for removal, allowing the removal of the display and steering wheel while the motor is securely mounted in place on the vehicle. This also allows the steering wheel to be assembled after the motor has been secured to the vehicle, if required during vehicle assembly.

[0089] exist Figure 7 In another embodiment 900 of the handwheel actuator assembly shown, an axial motor can be used instead of a radial motor. In this case, the rotor and stator are not arranged concentrically around a common axis, but are spaced apart along the common axis. It can be seen here that the rotor has two parts 901, 902, which sandwich the stator 903 in the middle.

[0090] For each of the four embodiments, the handwheel actuator assembly can be connected to, as shown below: Figure 6 The illustrated support structure allows for adjustment of the steering wheel's position for easy access and enables it to move away from the driver's seat and towards the front of the vehicle in the event of a frontal collision causing rapid vehicle deceleration. This allows the steering wheel to actively retract away from the driver or move with the driver's body when an unrestrained driver impacts the steering wheel or an inflatable airbag attached to the steering wheel. In each case, as is known in the field of steering wheel assembly design, this movement can help absorb the driver's kinetic energy.

[0091] The support structure includes a yaw support bracket 1000, which is pivotable about a pivot 1001, allowing adjustment of the yaw angle of the steering wheel 600. This yaw support bracket is further connected to a movable telescopic bracket 1002, which is in turn secured to the vehicle body via a mounting bracket 1003. In the context of this specification, when an item is described as a fixed part attached to a vehicle, this refers to any part that does not rotate or otherwise move relative to the vehicle body during normal use of the handwheel actuator.

Claims

1. A handwheel actuator assembly for a steer-by-wire system in a vehicle, the handwheel actuator assembly comprising: A steering wheel having at least one hand grip portion rotatable about the axis of rotation of the steering wheel and capable of being gripped by a driver, the steering wheel having a hub supporting the hand grip portion; case; Short axis; as well as A feedback torque generator includes an electric motor having a stator and a rotor housed in a housing. The rotor is fixed to the hub of the steering wheel via a short shaft and rotates with the hub. The axis of rotation of the short shaft lies on the axis of rotation of the hub and the rotor. The stator is fastened to a fixed portion of the vehicle body such that it cannot rotate relative to the vehicle body. The stator is fixed to a stator support portion, which is fastened to the fixed portion of the vehicle body during use. The stator support portion includes the housing for the electric motor. The electric motor includes a brushless permanent magnet vernier motor. The short shaft partially passes through the housing (606), which has a first cylindrical can (606a) bearing an assembly (607, 608) supporting the short shaft on its inner wall. The first cylindrical can (606a) is connected to a radially extending end wall (606b) of the housing, which is connected to a second cylindrical can (606c) further away from the steering wheel relative to the first cylindrical can. The second cylindrical can defines a portion of the housing containing a feedback torque generator for a vernier motor. The stator of the vernier motor is fixed to the housing, and the rotor of the vernier motor is fixed to a connector, which is fixed to the short shaft on the side of the vernier motor closest to the steering wheel. The stator of the vernier motor includes an annulus with a hollow center. The short shaft passes through the first cylindrical can (606a) of the housing (606), and the end of the short shaft furthest from the steering wheel is within the hollow center. The handwheel actuator assembly further includes: A travel limiter includes a first portion fixed relative to the vehicle body, the first portion engaging with a second portion during use when the rotor of the vernier motor reaches a predetermined end point of its rotational stroke, the second portion being fixed to the rotor, and An angle sensor is fixed to the end of the short shaft furthest from the steering wheel, and a cable carrying the signal output from the angle sensor passes away from the steering wheel through a hollow vernier motor for connection to circuitry located elsewhere in the vehicle.

2. The handwheel actuator assembly according to claim 1, wherein, The vernier motor includes an inverted radial motor, wherein the rotor has a larger diameter than the stator.

3. The handwheel actuator assembly according to claim 1 or 2, wherein, The connection between the rotor and the hub provides a direct 1:1 transmission ratio between them, such that in use, the hub rotates at the same speed as the rotor of the vernier motor.

4. The handwheel actuator assembly according to claim 1 or 2, wherein, The hollow center defines a space within the stator, through which an additional component of the handwheel actuator assembly passes, or within the space.

5. The handwheel actuator assembly according to claim 4, wherein, The additional component includes a wiring harness connected to a driver information display that displays information to the driver during use.

6. The handwheel actuator assembly according to claim 1 or 2, wherein, The vernier motor includes a stator with 6 stator teeth and a rotor with 5 pole pairs.

7. The handwheel actuator assembly according to claim 1 or 2, wherein, The vernier motor includes a stator with 12 stator teeth and a rotor with 11 pole pairs.

8. The handwheel actuator assembly according to claim 1 or 2, wherein, The short shaft is supported by two bearing assemblies.

9. The handwheel actuator assembly according to claim 1 or 2, wherein, The first part includes a radially inwardly projecting lug on the inner side of the outer wall of the housing, the lug engaging with a corresponding stop on the rotor, and the stop including a radially projecting portion of the rotor or an end face of a circumferential groove in which the lug of the first part extends partially around the circumference of the rotor is located.

10. The handwheel actuator assembly according to claim 1 or 2, wherein, The hub of the steering wheel is fixed to the rotor of the vernier motor by a mounting bracket.

11. A handwheel actuator assembly for a steer-by-wire system of a vehicle, the handwheel actuator assembly comprising: A steering wheel having at least one hand grip portion rotatable about the axis of rotation of the steering wheel and capable of being gripped by a driver, the steering wheel having a hub supporting the hand grip portion; case; Short axis; as well as A feedback torque generator includes an electric motor having a stator and a rotor housed in a housing. The rotor is directly or indirectly fixed to the hub of the steering wheel and rotates with the hub. The axis of rotation of a short shaft lies on the axis of rotation of the hub and the rotor. The stator is fastened to a fixed portion of the vehicle body such that the stator cannot rotate relative to the vehicle body. The stator is fixed to a stator support portion, which is fastened to the fixed portion of the vehicle body during use. The stator support portion includes the housing for the electric motor. The electric motor includes an annular stator with a hollow center, and an additional non-rotating component of the handwheel actuator assembly is located within the hollow center of the stator. The short shaft extends through the electric motor, and the housing has a first cylindrical can-shaped member (606a) on its inner wall carrying a bearing assembly (607, 608) supporting the short shaft, the bearing assembly being located on the side of the electric motor opposite to the steering wheel. The first cylindrical can-shaped member (606a) is connected to a radially extending end wall (606b) of the housing, which is connected to a second cylindrical can-shaped member (606c) further closer to the steering wheel relative to the first cylindrical can-shaped member. The second cylindrical can-shaped member defines a portion of the housing including the feedback torque generator of the electric motor, wherein the rotor is directly connected to the bushing of the steering wheel rather than to the short shaft. The handwheel actuator assembly further includes: A travel limiter includes a first portion fixed relative to the vehicle body, the first portion engaging with a second portion during use when the rotor of the electric motor reaches a predetermined end point of its rotational stroke, the second portion being fixed to the rotor, and An angle sensor is fixed to the end of the short shaft furthest from the steering wheel.

12. The handwheel actuator assembly of claim 11, wherein, The first part includes a radially inwardly projecting lug on the inner side of the outer wall of the housing, the lug engaging with a corresponding stop on the rotor, and the stop including a radially projecting portion of the rotor or an end face of a circumferential groove in which the lug of the first part extends partially around the circumference of the rotor is located.

13. The handwheel actuator assembly according to claim 11 or 12, wherein, The interior space of the hollow center can accommodate additional components, including a wiring harness for a display located within the clearance defined by the steering wheel.

14. The handwheel actuator assembly of claim 13, wherein, The hub includes one or more concave spokes extending around the exterior of the display.

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