System and method for holding steering wheel in steer-by-wire system

Abstract

Steer-by-wire includes a steering wheel retention system. The emulator controller receives vehicle data from a vehicle system and determines whether the vehicle is in one of a driving mode and a non-driving mode. When the vehicle is in a driving mode, the emulator controller transmits a command to the emulator switching system to electrically couple a phase of the emulator motor to the power source to enable the emulator motor to implement a steer-by-wire operation, placing the steering wheel in a non-hold mode. When the vehicle is in a non-driving mode, the emulator controller transmits a command to the emulator switching system to electrically couple the phase of the emulator motor to ground, to short the phase of the emulator motor to ground, to generate a resistance torque to resist rotational movement of a steering wheel of the vehicle, placing the steering wheel in a hold mode.

Description

TECHNICAL FIELD

[0001] The technical field is generally related to vehicles, and more specifically to systems and methods for holding a steering wheel in a steer-by-wire system. BACKGROUND

[0002] Steer-by-wire systems eliminate intermediate shafts between a steering wheel of a vehicle and a steering rack. When the vehicle is stationary and powered off, the steering wheel can be freely rotated without causing any corresponding movement on the steering rack. In many instances, a driver can inadvertently rotate the steering wheel during entry and exit from the vehicle using the steering wheel for support. This can cause the steering wheel to become out of sync with the steering rack. Synchronization between the steering wheel and the steering rack can not be effectively achieved before the driver begins driving the vehicle. Additionally, automatically moving the steering rack during a synchronization process without input from the driver can be disruptive to the driver.

[0003] Accordingly, it is desirable to provide systems and methods for holding a steering wheel in a steer-by-wire system when the vehicle is stationary and powered off. Other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background. SUMMARY

[0004] A steer-by-wire system including a steering wheel holding system includes a steering wheel, an emulator motor, an emulator switch system, and an emulator controller. The emulator motor is electrically coupled to the steering wheel and includes a plurality of phases. The emulator switch system is configured to electrically couple each of the plurality of phases of the emulator motor to one of a power source and a ground. The emulator controller is electrically coupled to the emulator motor and the emulator switch system. The emulator controller is configured to: receive vehicle data from at least one vehicle system of the vehicle; determine whether the vehicle is in one of a drive mode and a non-drive mode based on the vehicle data; when the vehicle is determined to be in the drive mode, communicate a first command to the emulator switch system to electrically couple each of the plurality of phases of the emulator motor to the power source to place the steering wheel in a non-holding mode to enable the emulator motor to perform steer-by-wire operations; and when the vehicle is determined to be in the non-drive mode, communicate a second command to the emulator switch system to electrically couple each of the plurality of phases of the emulator motor to the ground to short the plurality of phases of the emulator motor to the ground to cause the emulator motor to generate a resistive torque to resist rotational movement of the steering wheel to place the steering wheel in a holding mode.

[0005] In at least one embodiment, the vehicle data includes: an ignition state from an ignition system of the vehicle, the ignition state being one of an ignition on state and an ignition off state; vehicle movement data from a vehicle dynamics sensor system; and a vehicle drive mode of a drivetrain system of the vehicle.

[0006] In at least one embodiment, the emulator controller is further configured to determine that the vehicle is in the non-driving mode in response to receipt of an ignition off state from an ignition system, receipt of vehicle movement data associated with a stationary vehicle, and receipt of a vehicle drive mode from a drive system that is a park drive mode.

[0007] In at least one embodiment, the emulator controller is further configured to receive a third command from a body control module of the vehicle to enter a sleep mode when the vehicle is in the non-driving mode.

[0008] In at least one embodiment, the system includes a current detection system including a plurality of current detectors, wherein each of the plurality of current detectors is electrically coupled to one of a plurality of phases of the emulator motor and to ground to detect a current flow from each of the plurality of phases of the emulator motor to ground when the vehicle is in the non-driving mode, and configured to generate a trigger signal for transmission to the emulator controller in response to detecting the current flow from each of the plurality of phases of the emulator motor to ground; and the emulator controller is further configured to transition from the sleep mode to the wake-up mode in response to the trigger signal, transmit a second command to the emulator switching system to maintain electrical coupling of each of the plurality of phases of the emulator motor to ground in response to receipt of an ignition off state from an ignition system of the vehicle indicating that the vehicle is in the non-driving mode, and transmit a first command to the emulator switching system to electrically couple each of the plurality of phases of the emulator motor to the power source in response to receipt of an ignition on state from the ignition system of the vehicle indicating that the vehicle has transitioned to the driving mode.

[0009] In at least one embodiment, the system includes a current detection system including a plurality of current detectors, wherein each of the plurality of current detectors is electrically coupled to one of a plurality of phases of the emulator motor and to ground to detect a current flow from each of the plurality of phases of the emulator motor to ground when the vehicle is in the non-driving mode, and configured to generate a trigger signal for transmission to the emulator controller in response to detecting the current flow from each of the plurality of phases of the emulator motor to ground; and the emulator controller is further configured to transition from the sleep mode to the wake-up mode in response to the trigger signal, receive steering wheel positioning data from a steering wheel sensor, identify a rotational angle change of the steering wheel based on the steering wheel positioning data, and transmit the rotational angle change of the steering wheel to a steering rack controller of a steering rack of the vehicle when the vehicle transitions from the non-driving mode to the driving mode.

[0010] In at least one embodiment, the simulator switching system includes a plurality of single-pole double-throw (SPDT) relays, each of the plurality of SPDT relays configured to electrically couple an associated one of the plurality of phases of the simulator motor to one of a power source and ground.

[0011] In at least one embodiment, the simulator switching system includes a plurality of metal-oxide-semiconductor field-effect transistors (MOSFETs), each of the plurality of MOSFETs configured to electrically couple an associated one of the plurality of phases of the simulator motor to one of a power source and ground.

[0012] In at least one embodiment, a gear ratio between the simulator motor and the steering wheel is eleven to one.

[0013] A vehicle including a steer-by-wire system including a steering wheel retention system includes a steering wheel, a simulator motor, a simulator switching system, and a simulator controller. The simulator motor is electrically coupled to the steering wheel and includes a plurality of phases. The simulator switching system is configured to electrically couple each of the plurality of phases of the simulator motor to one of a power source and ground. The simulator controller is electrically coupled to the simulator motor and the simulator switching system. The simulator controller is configured to: receive vehicle data from at least one vehicle system of the vehicle; determine whether the vehicle is in one of a drive mode and a non-drive mode based on the vehicle data; when the vehicle is determined to be in the drive mode, transmit a first command to the simulator switching system to electrically couple each of the plurality of phases of the simulator motor to the power source to place the steering wheel in a non-retained mode to enable steer-by-wire operation of the simulator motor; and when the vehicle is determined to be in the non-drive mode, transmit a second command to the simulator switching system to electrically couple each of the plurality of phases of the simulator motor to the ground to short the plurality of phases of the simulator motor to the ground to cause the simulator motor to generate a resistive torque to resist rotational movement of the steering wheel to place the steering wheel in a retained mode.

[0014] In at least one embodiment, the vehicle data includes: an ignition state from an ignition system of the vehicle, the ignition state being one of an ignition on state and an ignition off state; vehicle movement data from a vehicle dynamics sensor system; and a vehicle drive mode of a drive train system of the vehicle.

[0015] In at least one embodiment, the simulator controller is further configured to determine that the vehicle is in the non-drive mode in response to receipt of the ignition off state from the ignition system, receipt of the vehicle movement data associated with a stationary vehicle, and receipt of the vehicle drive mode from the drive train system as a park drive mode.

[0016] In at least one embodiment, the emulator controller is configured to receive a third command from a body control module of the vehicle to enter a sleep mode when the vehicle is in the non-driving mode.

[0017] In at least one embodiment, the vehicle includes a current detection system including a plurality of current detectors, wherein each of the plurality of current detectors is electrically coupled to one of a plurality of phases of the emulator motor and to ground to detect a current flow from each of the plurality of phases of the emulator motor to ground when the vehicle is in the non-driving mode, and is configured to generate a trigger signal for transmission to the emulator controller in response to detecting the current flow from each of the plurality of phases of the emulator motor to ground; and the emulator controller is further configured to transition from the sleep mode to a wake-up mode in response to the trigger signal, transmit a second command to the emulator switching system to maintain each of the plurality of phases of the emulator motor electrically coupled to ground in response to receipt of an ignition off state from an ignition system of the vehicle indicating that the vehicle is in the non-driving mode, and transmit a first command to the emulator switching system to electrically couple each of the plurality of phases of the emulator motor to the power source in response to receipt of an ignition on state from the ignition system of the vehicle indicating that the vehicle has transitioned to the driving mode.

[0018] In at least one embodiment, the vehicle includes a current detection system including a plurality of current detectors, wherein each of the plurality of current detectors is electrically coupled to one of a plurality of phases of the emulator motor and to ground to detect a current flow from each of the plurality of phases of the emulator motor to ground when the vehicle is in the non-driving mode, and is configured to generate a trigger signal for transmission to the emulator controller in response to detecting the current flow from each of the plurality of phases of the emulator motor to ground; and the emulator controller is further configured to transition from the sleep mode to a wake-up mode in response to the trigger signal, receive steering wheel positioning data from a steering wheel sensor, identify a rotational angle change of the steering wheel based on the steering wheel positioning data, and transmit the rotational angle change of the steering wheel to a steering rack controller of a steering rack of the vehicle when the vehicle transitions from the non-driving mode to the driving mode.

[0019] In at least one embodiment, the emulator switching system includes a plurality of single-pole double-throw (SPDT) relays, each of the plurality of SPDT relays is configured to electrically couple an associated one of the plurality of phases of the emulator motor to one of the power source and ground.

[0020] In at least one embodiment, the emulator switching system includes a plurality of metal-oxide-semiconductor field-effect transistors (MOSFETs), each of the plurality of MOSFETs is configured to electrically couple an associated one of the plurality of phases of the emulator motor to one of the power source and ground.

[0021] In at least one embodiment, the gear ratio between the emulator motor and the steering wheel is eleven to one.

[0022] A method for holding a steering wheel in a steer-by-wire system includes receiving vehicle data from at least one vehicle system of a vehicle; determining whether the vehicle is in one of a drive mode and a non-drive mode based on the vehicle data; when the vehicle is determined to be in the drive mode, communicating a first command to an emulator switching system to electrically couple each of a plurality of phases of an emulator motor to a power source to place the steering wheel in a non-hold mode to enable the emulator motor to implement steer-by-wire operation; and when the vehicle is determined to be in the non-drive mode, communicating a second command to the emulator switching system to electrically couple each of the plurality of phases of the emulator motor to a ground to short the plurality of phases of the emulator motor to the ground to cause the emulator motor to generate a resistive torque to resist rotational movement of the steering wheel to place the steering wheel in a hold mode.

[0023] In at least one embodiment, the method further includes determining that the vehicle is in the non-drive mode in response to receiving an ignition off state from an ignition system of the vehicle, receiving vehicle movement data associated with a stationary vehicle from a vehicle dynamics sensor, and receiving a vehicle drive mode from a drive system of the vehicle that is a park drive mode. BRIEF DESCRIPTION OF DRAWINGS

[0024] Example embodiments will be described below with reference to the following drawings, in which like numerals indicate like elements, and in which:

[0025] Figure 1 is a functional block diagram of a vehicle including a steer-by-wire system including a steering wheel hold system in accordance with at least one embodiment;

[0026] Figure 2 is a functional block diagram of a steering wheel hold system in accordance with at least one embodiment;

[0027] Figure 3 is a functional block diagram of a portion of an emulator motor phase of a steering wheel hold system including an emulator motor in accordance with at least one embodiment;

[0028] Figure 4 is a circuit diagram of an example current detector in accordance with at least one embodiment;

[0029] Figure 5 is a flowchart representation of an example method for holding a steering wheel in a steer-by-wire system in accordance with at least one embodiment; and

[0030] Figure 6is an exemplary graphical representation of the variation of steering wheel rotational speed with resistance torque applied by the simulator motor, in accordance with at least one embodiment. DETAILED DESCRIPTION

[0031] The following detailed description is merely exemplary in nature and is not intended to limit the application and use. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, summary or the following detailed description. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the described functionality.

[0032] Embodiments of the present disclosure can be described herein in terms of functional and / or logical block components and various processing steps. It should be appreciated that such block components can be realized by any number of hardware, software, and / or firmware components configured to perform the specified functions. For example, an embodiment of the present disclosure can employ various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, look-up tables, and the like, which can carry out a variety of functions under the control of one or more microprocessors or other control devices. In addition, those skilled in the art will appreciate that embodiments of the present disclosure can be practiced with one or more systems including a variety of

[0033] For the sake of brevity, conventional techniques related to signal processing, data transmission, signaling, control, and other functional aspects of the systems (and the individual operating components of the systems) can not be described in detail herein. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent example functional relationships and / or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections can be present in an embodiment of the present disclosure.

[0034] Reference Figure 1 FIG. 1 shows a functional block diagram of a vehicle containing a steer-by-wire system 24 including a steering wheel retention system 200, in accordance with at least one embodiment. The vehicle 10 generally includes a chassis 12, a body 14, front wheels 16, and rear wheels 18. Although the vehicle 10 is described as a passenger car in the illustrated embodiment, the vehicle 10 can be other types of vehicles, including trucks, sport utility vehicles (SUVs), and recreational vehicles (RVs).

[0035] In various embodiments, the body 14 is disposed on the chassis 12 and substantially encloses the components of the vehicle 10. The body 14 and the chassis 12 can collectively form a frame. The wheels 16-18 are each rotationally coupled to the chassis 12 near a respective corner of the body 14.

[0036] In various embodiments, vehicle 10 is an automatically controlled autonomous or semi-autonomous vehicle for transporting passengers and / or goods from one place to another. For example, in an exemplary embodiment, vehicle 10 is a so-called Level 2, Level 3, Level 4, or Level 5 automation system. Level 2 automation means that the vehicle assists the driver in various driving tasks under the supervision of the driver. Level 3 automation means that the vehicle can take over all driving functions in certain situations. All major functions are automatic, including braking, steering, and acceleration. At this level, the driver can completely let go until the vehicle otherwise informs the driver. A Level 4 system indicates “high automation,” referring to the performance of the automated driving system in specific driving modes for all aspects of a dynamic driving task, even if the human driver does not respond appropriately to intervention requests. A Level 5 system indicates “full automation,” referring to the full-time performance of the automated driving system for all aspects of a dynamic driving task under all road and environmental conditions that can be managed by a human driver.

[0037] As shown in the figure, vehicle 10 typically includes a propulsion system 20, a transmission system 22, a steering system 24, a braking system 26, a sensor system 28, an actuator system 30, at least one data storage device 32, at least one controller 34, and a communication system 36. The controller 34 is configured to implement an automated driving system (ADS). The propulsion system 20 is configured to generate power to propel the vehicle. In various embodiments, the propulsion system 20 may include an internal combustion engine, an electric motor such as a traction motor, a fuel cell propulsion system, and / or any other type of propulsion configuration. The transmission system 22 is configured to transmit power from the propulsion system 20 to the wheels 16-18 according to a selectable speed ratio. According to various embodiments, the transmission system 22 may include a step-ratio automatic transmission, a continuously variable transmission (CVT), or other suitable transmission. The braking system 26 is configured to provide braking torque to the wheels 16-18. In various embodiments, the braking system 26 may include friction brakes, brake-by-wire brakes, regenerative braking systems such as electric motors, and / or other suitable braking systems.

[0038] The steering system 24 is configured to affect positioning of the wheels 16. Although depicted as including a steering wheel and steering column for illustrative purposes, the steering system 24 can not include a steering wheel and / or steering column in certain embodiments contemplated within the scope of the present disclosure. The steering system 24 includes a steering column that is coupled to the axles 50 associated with the front wheels 16 by, for example, a rack and pinion or other mechanism (not shown). Alternatively, the steering system 24 can include a steer-by-wire system that includes an actuator associated with each of the front wheels 16. The steer-by-wire system 24 includes a steering wheel retention system 200 in accordance with at least one embodiment.

[0039] The sensor system 28 includes one or more sensing devices 40a-40n that sense observable conditions of the external and / or internal environment of the vehicle 10. The sensing devices 40a-40n can include, without limitation, radar, lidar, global positioning systems, optical cameras, thermal cameras, ultrasonic sensors, steering wheel sensors, and / or other sensors.

[0040] The vehicle dynamics sensors provide vehicle dynamics data including longitudinal velocity, yaw rate, lateral acceleration, longitudinal acceleration, etc. The vehicle dynamics sensors can include wheel sensors that measure information related to one or more wheels of the vehicle 10. In one embodiment, the wheel sensors include wheel speed sensors coupled to each of the wheels 16-18 of the vehicle 10. Additionally, the vehicle dynamics sensors can include one or more accelerometers (provided as part of an inertial measurement unit (IMU)) that measure information related to acceleration of the vehicle 10. In various embodiments, the accelerometers measure one or more acceleration values of the vehicle 10, including lateral and longitudinal acceleration and yaw rate. In at least one embodiment, the vehicle dynamics sensors provide vehicle movement data.

[0041] The actuator system 30 includes one or more actuator devices 42a-42n that control one or more vehicle features, such as, but not limited to, one or more wheels 16-18, the propulsion system 20, the drivetrain 22, the steering system 24, and the braking system 26. In various embodiments, the vehicle features can also include internal and / or external vehicle features, such as, but not limited to, doors, trunk, and cabin features (not numbered) such as air, music, lighting, etc.

[0042] The communication system 36 is configured to wirelessly communicate information to and from other entities, such as but not limited to other vehicles ("V2V" communications), infrastructure ("V2I" communications), remote systems, and / or personal devices. In an exemplary embodiment, the communication system 36 is a wireless communication system configured to communicate via a wireless local area network (WLAN) using the IEEE 802.11 standard or through the use of cellular data communication. However, additional or alternative communication methods, such as a dedicated short-range communications (DSRC) channel, are also considered to be within the scope of the present disclosure. A DSRC channel refers to a one-way or two-way short-to-medium range wireless communication channel designed specifically for automotive use, as well as a corresponding set of protocols and standards.

[0043] The data storage device 32 stores data for use in the ADS of the vehicle 10. In various embodiments, the data storage device 32 stores a defined map of a navigable environment. In various embodiments, the defined map can be predefined by a remote system and obtained from the remote system. For example, the defined map can be assembled by the remote system and communicated to the vehicle 10 (wirelessly and / or in a wired manner) and stored in the data storage device 32. It can be appreciated that the data storage device 32 can be part of the controller 34, separate from the controller 34, or part of both the controller 34 and a separate system.

[0044] The controller 34 includes at least one processor 44 and a computer- readable storage device or media 46. The processor 44 can be any custom made or commercially available processor, a central processing unit (CPU), a graphics processing unit (GPU), a co-processor associated with the controller 34, a semiconductor-based microprocessor (in the form of a microchip or chip set), a macroprocessor, any combination thereof, or generally any device for executing instructions. The computer-readable storage device or media 46 can include volatile and nonvolatile storage in, for example, read-only memory (ROM), random access memory (RAM), and keep-alive memory (KAM). KAM is a persistent or non-volatile memory that can be used to store various operating variables at power down of the processor 44. The computer-readable storage device or media 46 can be implemented using any of a number of known memory devices, such as PROM (programmable read-only memory), EPROM (erasable PROM), EEPROM (electrically erasable PROM), flash memory, or any other electric, magnetic, optical, or combination memory device capable of storing data, some of which represent executable instructions that are executed by the controller 34 to control the vehicle 10.

[0045] The instructions, which can comprise one or more separate programs, each of which comprises an ordered listing of executable instructions for implementing logical functions. The instructions receive and process signals from the sensor system 28, perform logical, computational, and / or algorithmic functions for automatically controlling components of the vehicle 10, and generate control signals to the actuator system 30 to automatically control components of the vehicle 10 based on the logical, computational, and / or algorithmic functions when executed by the processor 44. Although only one controller 34 is shown in Figure 1 FIG. 1, embodiments of the vehicle 10 can include any number of controllers 34 that communicate over any suitable communication medium or combination of communication mediums and cooperate to process sensor signals, perform logical, computational, and / or algorithmic functions, and generate control signals to automatically control features of the vehicle 10. In various embodiments, the controller(s) 34 are configured to implement an ADS.

[0046] Referring to Figure 2 FIG. 1, a functional block diagram of a steering wheel hold system 200 is shown, in accordance with at least one embodiment. The steer-by-wire system 24 includes the steering wheel hold system 200. The steering wheel hold system 200 includes an emulator controller 202, an emulator switching system 204, a current detection system 206, and an emulator motor 208. The steering wheel hold system 200 includes one or more components of the steer-by-wire system 24. The steering wheel hold system 200 is configured to place the steering wheel 216 of the vehicle 10 in a non-hold mode when the vehicle 10 is in a drive mode and to place the steering wheel 216 of the vehicle 10 in a hold mode when the vehicle 10 is in a non-drive mode.

[0047] The emulator controller 202 is similar to the controller 34 described with reference to Figure 1 The emulator controller 202 includes at least one processor and at least one memory. The at least one processor is a programmable device that includes one or more instructions stored in or associated with the at least one memory. The at least one memory includes instructions that the at least one processor is configured to execute to implement operations associated with the steering wheel hold system 200.

[0048] The emulator switching system 204 includes a plurality of switches. In at least one embodiment, the plurality of switches are single-pole double-throw (SPDT) relays. In at least one embodiment, the plurality of switches are metal-oxide-semiconductor field-effect transistors (MOSFETs). The current detection system 206 includes a plurality of current detectors. The emulator motor 208 is a multi-phase motor that includes a plurality of phases. In at least one embodiment, the emulator motor 208 is a three-phase motor. In at least one embodiment, the emulator motor 208 is a multiple stacked motor.

[0049] Vehicle 10 includes a steer-by-wire system 24 comprising a steering wheel holding system 200. The steering wheel holding system 200 is configured to communicatively couple to multiple vehicle systems 210, 212, 214, 216, 218, and 220. In various embodiments, the vehicle systems include an ignition system 210, a vehicle dynamics sensor system 212, a transmission system 214, a steering wheel 216, a steering wheel sensor 218, and a steering rack controller 220. The steering wheel holding system 200 is configured to receive vehicle data from the ignition system 210, the vehicle dynamics sensor system 212, and the transmission system 214. Examples of vehicle data include, but are not limited to, ignition status, vehicle movement data, and vehicle drive mode.

[0050] The steering wheel holding system 200 is configured to receive the ignition state of the ignition system 210. The ignition state of the ignition device is one of an ignition-on state and an ignition-off state. In at least one embodiment, the steering wheel holding system 200 is configured to receive the ignition state directly from the ignition system 210. In at least one embodiment, a controller 34 in the vehicle 10 can track the state of the ignition system, and the steering wheel holding system 200 is configured to receive the ignition state from the controller 34.

[0051] The steering wheel holding system 200 is configured to receive vehicle movement data from the vehicle dynamics sensor system 212. The vehicle movement data indicates whether the vehicle 10 is in motion or stationary. In at least one embodiment, the steering wheel holding system 200 is configured to receive vehicle movement data directly from the vehicle dynamics sensor system 212. In at least one embodiment, a controller 34 in the vehicle 10 collects vehicle movement data from the vehicle dynamics sensor system 212, and the steering wheel holding system 200 is configured to receive vehicle movement data from the controller 34.

[0052] The steering wheel holding system 200 is configured to receive the vehicle drive mode from the vehicle's drivetrain 214. The drivetrain 214 is similar to the reference... Figure 1 The described drivetrain 22. In at least one embodiment, the vehicle drivetrain modes include, but are not limited to, a drive mode, a neutral mode, a parking mode, and a reverse mode. In at least one embodiment, the steering wheel holding system 200 is configured to receive the vehicle drivetrain mode directly from the drivetrain 214. In at least one embodiment, a controller 34 in the vehicle 10 receives the vehicle drivetrain mode from the drivetrain 214, and the steering wheel holding system 200 is configured to receive the vehicle drivetrain mode from the controller 34.

[0053] The steering wheel hold system 200 is mechanically coupled to a steering wheel 216 of the vehicle 10. The vehicle 10 operates in one of a drive mode and a non-drive mode. The simulator controller 202 determines whether the vehicle 10 is in the drive mode or the non-drive mode based on vehicle data. The simulator motor 208 is mechanically coupled to the steering wheel 216. The simulator switch system 204 is configured to electrically couple a phase of the simulator motor 208 to a power source when the vehicle 10 is in the drive mode and the steering wheel 216 is in a non-hold mode. When the phase of the simulator motor 208 is electrically coupled to the power source, the simulator motor 208 is configured to mechanically implement a steer-by-wire operation.

[0054] The simulator switch system 204 is configured to electrically couple the phase of the simulator motor 208 to a ground to short the phase of the simulator motor 208 to the ground when the vehicle 10 is in the non-drive mode. When the phase of the simulator motor 208 is electrically coupled shorted to the ground, the simulator motor 208 is configured to mechanically implement a steering wheel hold operation. When the phase of the simulator motor 208 is simultaneously disconnected from the power source and shorted to the ground, the simulator motor 208 operates as a generator and generates a resistive torque to the steering wheel 216 to resist rotational movement of the steering wheel 216 and place the steering wheel 216 in a hold mode.

[0055] The steering wheel hold system 200 is configured to receive steering wheel positioning data from a steering wheel sensor 218. The simulator controller 202 is configured to track positioning of the steering wheel based on the steering wheel positioning data. When the vehicle 10 is in the drive mode, the simulator controller 202 is configured to communicate the positioning of the steering wheel to a steering rack controller 220 to implement the steer-by-wire operation. The simulator controller 202 is configured to receive steering rack data from the steering rack controller 220 and issue commands to the simulator motor 208 to adjust the positioning of the steering wheel according to the steering rack data to implement the steer-by-wire operation. When the vehicle 10 is in the non-drive mode, the simulator controller 202 is configured to implement the steering wheel hold operation. The steering wheel hold operation will be described in more detail below.

[0056] Referring to Figure 3 FIG. 3 shows a functional block diagram of a portion of a simulator motor phase 300 of the steering wheel hold system 200 including the simulator motor 208, in accordance with at least one embodiment.

[0057] The simulator motor 208 includes a plurality of simulator motor phases 300. The simulator switch system 204 includes a plurality of switch pairs 308, 310. The current detection system 206 includes a plurality of current detectors 306.

[0058] The simulator controller 202 manages the opening and closing of each of the switches in the switch pair 308, 310. When the simulator controller 202 determines that the vehicle 10 is in the drive mode based on the vehicle data received from the vehicle systems 210, 212, 214 of the vehicle 10, the simulator controller 202 issues a command to close the switch 308, thereby electrically coupling the simulator motor phase 300 to the power source 302, and to open the switch 310, thereby breaking the electrical coupling between the simulator motor phase 300 and the ground 304. Electrically coupling each of the simulator motor phases 300 to the power source 302 while breaking the electrical coupling between each of the simulator motor phases 300 and the ground 304 places the steering wheel 216 in the non-hold mode. Placing the steering wheel 216 in the non-hold mode enables steer-by-wire operation by the steer-by-wire system 24 of the vehicle 10. The switches 308, 310 are exclusively opened. Only one of the switches 308, 310 can be opened at a time. Both switches 308, 310 cannot be opened at the same time. When the switch 308 is opened, the switch 310 is closed, and when the switch 310 is opened, the switch 308 is closed.

[0059] When the simulator controller 202 determines that the vehicle 10 is in the non-drive mode based on the vehicle data received from the vehicle systems 210, 212, 214 of the vehicle 10, the simulator controller 202 issues a command to open the switch 308, thereby breaking the electrical coupling between the simulator motor phase 300 and the power source 302, and to close the switch 310, thereby electrically coupling the simulator motor phase 300 to the ground 304 at the same time. Electrically coupling the simulator motor phases 300 to the ground 304 shorts the simulator motor phases 300 to the ground. Shorting the simulator motor phases 300 of the simulator motor 208 to the ground causes the simulator motor 208 to operate as a generator. The simulator motor 208 generates a resistive torque for application to the steering wheel 216, thereby placing the steering wheel 216 in the hold mode. When the steering wheel 216 is in the hold mode, the steering wheel resists rotational movement. The simulator controller 202 enters a sleep mode after issuing the command to the simulator switch system 204 to place the steering wheel 216 in the hold mode.

[0060] When the steering wheel 216 is in the hold mode, the steering wheel 216 resists rotational movement. However, when a rotational force applied to the steering wheel exceeds the rotational force threshold, the rotational force overcomes the resistive torque applied to the steering wheel 216 by the simulator motor 208, causing angular rotation of the steering wheel 216. When the switch 310 is closed, the current detector 306 is electrically coupled to the simulator motor phase 300 and ground 304. When the rotational force exceeds the rotational force threshold and the rotational force causes angular rotation of the steering wheel 216, there is a current flow from the simulator motor phase 300 to ground 304. The current flow is detected by the current detector 306. Upon detection of the current flow, the current detector 306 generates a trigger signal for transmission to the simulator controller 202. The simulator controller 202 transitions from the sleep mode to the wake-up mode in response to the trigger signal.

[0061] The simulator controller 202 stores the positioning of the steering wheel 216 at the time the simulator controller 202 enters the sleep mode. In the wake-up mode, the simulator controller 202 receives steering wheel positioning data from the steering wheel sensor 218. The simulator controller 202 identifies a change in the angle of rotation of the steering wheel caused by the application of a rotational force that exceeds the rotational force threshold based on the steering wheel data. The simulator controller 202 stores the change in the angle of rotation. In at least one embodiment, the simulator controller 202 returns to the sleep mode after storing the change in the angle of rotation.

[0062] When the vehicle 10 transitions from the non-driving mode to the driving mode, the simulator controller 202 enters the wake-up mode and communicates the change in the angle of rotation to the steering rack controller 220 to effect synchronization of the positioning of the steering wheel between the simulator controller 202 and the steering rack controller 220 in order to effectively implement steer-by-wire operation.

[0063] Referring to Figure 4 , a circuit diagram of an example current detector 306 is shown in accordance with at least one embodiment. In at least one embodiment, the current detector 306 is an operational amplifier (op amp) circuit. The op amp circuit includes a current sense resistor 400. When there is a current flow from the simulator motor phase 300 to ground 304, a current sense voltage is generated across the current sense resistor 400. The current sense voltage is amplified by the op amp circuit and generated as a trigger signal at the output of the op amp circuit. The output of the op amp circuit is electrically coupled to the simulator controller 202. The trigger signal generated by the op amp in response to the current flow from the simulator motor phase 300 to ground 304 is communicated to the simulator controller 202. In response to receipt of the trigger signal, the simulator controller 202 transitions from the sleep mode to the wake-up mode. While one example of a current detector 306 has been described, other types of current detectors 306 can be used in alternative embodiments.

[0064] Referring Figure 5 FIG. 5 shows a flowchart representation of an exemplary method 500 for maintaining a steering wheel in a steer-by-wire system, in accordance with at least one embodiment. The method 500 will be described with reference to an exemplary implementation of an embodiment of the steer-by-wire system 24 including the steering wheel maintenance system 200. As can be appreciated in light of this disclosure, the order of operations within the method 500 is not limited to the sequential execution as shown in FIG. 5, but can be performed in one or more different orders as applicable and in accordance with this disclosure. Figure 5

[0065] At 502, the emulator controller 202 determines whether the vehicle 10 is in a non- driving mode. In at least one embodiment, the emulator controller 202 receives vehicle data generated by several vehicle systems 210, 212, 214 of the vehicle. The vehicle systems include, but are not limited to, an ignition system 210, a vehicle dynamics sensor system 212, and a driveline system 214. The vehicle data includes, but is not limited to, an ignition state of the ignition system 210, vehicle movement data generated by the vehicle dynamics sensor system 212, and a vehicle driveline mode of the driveline system 214. The ignition state of the ignition system 210 can be one of an ignition on state and an ignition off state. The vehicle movement data indicates whether the vehicle 10 is in motion or stationary. The vehicle driveline mode can be one of a drive driveline mode, a neutral driveline mode, a park driveline mode, and a reverse driveline mode.

[0066] If the ignition state of the ignition system 210 is the ignition off state, the vehicle movement data indicates that the vehicle 10 is a stationary vehicle, and the driveline mode is the park driveline mode, the emulator controller 202 determines that the vehicle 10 is in the non-driving mode. In all other combinations of the conditions associated with the ignition system 210, the vehicle movement data, and the driveline system 214, the emulator controller 202 determines that the vehicle 10 is in the driving mode.

[0067] If the emulator controller determines that the vehicle 10 is in the driving mode, the emulator switching system 204 maintains each of the emulator motor phases 300 of the emulator motor 208 electrically coupled to the power source 302. Maintaining each of the emulator motor phases 300 of the emulator motor 208 electrically coupled to the power source 302 maintains the steering wheel 216 in the non-maintenance mode, thereby enabling the emulator motor 208 to implement the steer-by-wire operation. The method 500 repeats at 502.

[0068] ​If the simulator controller 202 determines that the vehicle 10 is in the non-driving mode, the simulator motor phase 300 of the simulator motor 208 is shorted to ground, thereby placing the steering wheel 216 in the hold mode. The simulator controller 202 issues a command to the simulator switch system 204 to simultaneously disconnect the power source 302 from the simulator motor phase 300 of the simulator motor 208, while electrically coupling the simulator motor phase 300 of the simulator motor 208 to ground to place the steering wheel 216 in the hold mode. This causes the simulator motor 208 to operate as a generator and generate a resistive torque for application to the steering wheel 216 to resist rotational movement.

[0069] At 506, the simulator controller 202 enters the sleep mode from the wake mode. In at least one embodiment, the host control module of the vehicle 10 communicates a sleep mode command to the simulator controller 202 when the vehicle 10 enters the non-driving mode. The simulator controller 202 enters the sleep mode in response to the sleep command.

[0070] At 508, the current detection system 206 determines whether there is a current flow from the simulator motor phase 300 of the simulator motor 208 to the ground 304. The current detection system 206 includes a plurality of current detectors 306. Each of the current detectors 306 is configured to detect a current flow from the associated simulator motor phase 300 to ground when the vehicle 10 is in the non-driving mode and the simulator motor 208 is shorted to the ground 304.

[0071] When the steering wheel 216 is in the hold mode, the steering wheel 216 resists rotational movement. However, when a rotational force is applied to the steering wheel 216 that exceeds a rotational force threshold, the rotational force overcomes the resistive torque applied to the steering wheel 216 by the simulator motor 208, thereby causing an angular rotation of the steering wheel 216. The angular rotation of the steering wheel 216 causes a current flow from the simulator motor phase 300 to the ground 304. For example, a rotational force can be applied to the steering wheel 216 when a driver grasps the steering wheel 216 for support while exiting or entering the vehicle 10.

[0072] If the current detection system 206 does not detect a current flow from the simulator motor phase 300 of the simulator motor 208 to the ground 304, there is no angular rotation of the steering wheel, and the method repeats 508.

[0073] If the current detection system 206 does detect a flow of current from the simulator motor phase 300 of the simulator motor 208 to ground 304, there is an angular rotation of the steering wheel 216. Upon detecting a flow of current from the simulator motor phase 300 of the simulator motor 208 to ground 304, the current detector 306 generates a trigger signal for transmission to the simulator controller 202. At 510, the simulator controller 202 transitions from the sleep mode to the wake-up mode in response to the trigger signal.

[0074] At 512, the simulator controller 202 identifies a rotational angle change in the positioning of the steering wheel 216 caused by the application of rotational force by the driver to overcome the resistive torque applied to the steering wheel 216 by the simulator motor 208. The simulator controller 202 stores the positioning of the steering wheel 216 at the time the simulator controller 202 entered the sleep mode. In the wake-up mode, the simulator controller 202 receives steering wheel positioning data from the steering wheel sensor 218. The simulator controller 202 identifies the rotational angle change in the steering wheel 216. The simulator controller 202 stores the rotational angle change at the simulator controller 202.

[0075] At 514, the simulator controller 202 determines whether the vehicle 10 is in the drive mode. If the simulator controller 202 determines that the vehicle 10 has not transitioned from the non-drive mode to the drive mode, the method returns to 506 and the simulator controller 202 transitions from the wake-up mode to the sleep mode. If the simulator controller 202 determines that the vehicle 10 has transitioned from the non-drive mode to the drive mode, the simulator controller 202 issues a command to the simulator switching system 204 to electrically decouple the simulator motor phase 300 of the simulator motor 208 from ground 304 and electrically couple the simulator motor phase 300 of the simulator motor 208 to the power source 302, thereby placing the steering wheel in the non-hold mode and enabling the simulator motor 208 to implement steer-by-wire operation at 516. At 518, the simulator controller 202 communicates the rotational angle change to the steering rack controller 220 to effect synchronization of the positioning of the steering wheel between the simulator controller 202 and the steering rack controller 220 in order to effectively implement steer-by-wire operation.

[0076] Reference Figure 6FIG. 6, shows an exemplary graphical representation 600 of steering wheel rotational velocity versus changes in resistive torque applied by the simulator motor 208, in accordance with at least one embodiment. When the vehicle 10 is in the non-driving mode and the steering wheel 216 is in the hold mode, the simulator motor 208 applies a resistive torque to the steering wheel 216 such that the steering wheel 216 moves against rotation. In at least one embodiment, as the rotational velocity of the rotational force applied to the steering wheel 216 increases, the simulator motor 208 increases the amount of resistive torque applied to the steering wheel 216. The graph 600 represents an example of the relationship between the rotational velocity of the rotational force applied to the steering wheel 216 and the resistive torque applied to the steering wheel 216 by the simulator motor 208.

[0077] While at least one example embodiment has been presented in the foregoing detailed description, it should be appreciated that a multitude of modifications can be made. It should also be appreciated that the example embodiment or embodiments are only examples and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an example embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof.

Claims

1. A steer-by-wire system comprising a steering wheel retention system, comprising: a steering wheel; an emulator motor electrically coupled to the steering wheel, the emulator motor comprising a plurality of phases; an emulator switching system configured to electrically couple each of the plurality of phases of the emulator motor to one of a power source and ground; and an emulator controller electrically coupled to the emulator motor and the emulator switching system, the emulator controller configured to: receive vehicle data from at least one vehicle system of a vehicle; determine whether the vehicle is in one of a drive mode and a non-drive mode based on the vehicle data; when the vehicle is determined to be in the drive mode, transmit a first command to the emulator switching system to electrically couple each of the plurality of phases of the emulator motor to the power source to place the steering wheel in a non-retention mode, enabling the emulator motor to implement steer-by-wire operation; and when the vehicle is determined to be in the non-drive mode, transmit a second command to the emulator switching system to electrically couple each of the plurality of phases of the emulator motor to ground to short the plurality of phases of the emulator motor to ground, causing the emulator motor to generate a resistive torque to resist rotational movement of the steering wheel, placing the steering wheel in a retention mode.

2. The system of claim 1, wherein the vehicle data comprises: an ignition state from an ignition system of the vehicle, the ignition state being one of an ignition on state and an ignition off state; vehicle movement data from a vehicle dynamics sensor system; and a vehicle drive mode of a drive train system of the vehicle.

3. The system of claim 2, wherein the emulator controller is further configured to determine the vehicle is in the non-drive mode in response to receipt of the ignition off state from the ignition system, receipt of vehicle movement data associated with a stationary vehicle, and receipt of the vehicle drive mode from the drive train system comprising a park drive mode.

4. The system of claim 1, wherein when the vehicle is in the non-drive mode, the emulator controller is configured to receive a third command from a body control module of the vehicle to enter a sleep mode.

5. The system of claim 4, further comprising a current detection system comprising a plurality of current detectors, wherein when the vehicle is in a non-drive mode, each of the plurality of current detectors is electrically coupled to one of the plurality of phases of the emulator motor and ground to detect a current flow from each of the plurality of phases of the emulator motor to ground, and configured to generate a trigger signal for transmission to the emulator controller in response to detecting the current flow from each of the plurality of phases of the emulator motor to ground; and the emulator controller is further configured to: transition from the sleep mode to a wake mode in response to the trigger signal; in response to receipt of an indication from an ignition system of the vehicle that the vehicle is in an ignition off state of the non-drive mode, transmitting the second command to the emulator switching system to maintain each of the plurality of phases of the emulator motor electrically coupled to ground; and in response to receipt of an indication from the ignition system of the vehicle that the vehicle has transitioned to an ignition on state of the drive mode, transmitting the first command to the emulator switching system to electrically couple each of the plurality of phases of the emulator motor to the power source.

6. The system of claim 4, further comprising a current detection system including a plurality of current detectors, wherein each of the plurality of current detectors is electrically coupled to one of the plurality of phases of the emulator motor and to ground when the vehicle is in the non-drive mode to detect a current flow from each of the plurality of phases of the emulator motor to ground and is configured to generate a trigger signal for transmission to the emulator controller in response to detecting the current flow from each of the plurality of phases of the emulator motor to ground; and the emulator controller is further configured to: transition from the sleep mode to a wake-up mode in response to the trigger signal; receive steering wheel positioning data from a steering wheel sensor; identify a change in a rotational angle of the steering wheel based on the steering wheel positioning data; and transmit the change in the rotational angle of the steering wheel to a rack control of a steering rack of the vehicle when the vehicle transitions from the non-drive mode to the drive mode.

7. The system of claim 1, wherein the emulator switching system includes a plurality of single-pole double-throw (SPDT) relays, each of the plurality of SPDT relays configured to electrically couple an associated one of the plurality of phases of the emulator motor to one of the power source and ground.

8. The system of claim 1, wherein emulator switching system includes a plurality of metal-oxide-semiconductor field-effect transistors (MOSFETs), each of the plurality of MOSFETs configured to electrically couple an associated one of the plurality of phases of the emulator motor to one of the power source and ground.

9. A method for holding a steering wheel in a steer-by-wire system, comprising: receiving vehicle data from at least one vehicle system of a vehicle; determining whether the vehicle is in one of a drive mode and a non-drive mode based on the vehicle data; when the vehicle is determined to be in the drive mode, transmitting a first command to an emulator switching system to electrically couple each of a plurality of phases of an emulator motor to a power source to place the steering wheel in a non-hold mode to enable steer-by-wire operation of the emulator motor; and when it is determined that the vehicle is in the non-driving mode, transmitting a second command to the emulator switching system to electrically couple each of the plurality of phases of the emulator motor to ground to short the plurality of phases of the emulator motor to ground, thereby causing the emulator motor to generate a resistive torque to resist rotational movement of the steering wheel, placing the steering wheel in a hold mode.

10. The method of claim 9, further comprising determining that the vehicle is in the non-driving mode in response to receiving an ignition off state from an ignition system of the vehicle, receiving vehicle movement data from a vehicle dynamics sensor associated with a stationary vehicle, and receiving a vehicle drive mode from a drive system of the vehicle including a park drive mode.

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