Vehicle reverse drive mode

A vehicle includes an electric machine that generates torque to move wheels of the vehicle, and a controller. The controller operates the electric machine to limit a maximum speed at which the vehicle is driven in reverse such that the maximum speed depends on a number of detected objects behind the vehicle.

TECHNICAL FIELD

The present disclosure relates to a method for operating a vehicle in reverse.

BACKGROUND

Many electric vehicles (EVs) use a single speed transmission coupled between an electric motor and wheels. The EVs may drive forward (i.e. in drive mode) when the electric motor rotates in one direction, and drive backward (i.e. in reverse mode) when the electric motor rotates in the other direction. Although the EVs may theoretically drive in reverse at a high rate of speed, many EVs are equipped with a reverse speed limiter.

SUMMARY

A vehicle includes an electric machine that generates torque to move wheels of the vehicle, and a controller that operates the electric machine to limit a maximum speed at which the vehicle is driven in reverse such that the maximum speed depends on a number of detected objects behind the vehicle.

A method includes operating an electric machine to drive a vehicle in reverse, and limiting a maximum speed of the vehicle while being driven in reverse according to a location of the vehicle.

A drivetrain for a vehicle includes a controller that limits a maximum speed at which the vehicle is driven in reverse such that the maximum speed is greater when a siren is on than when the siren is off.

DETAILED DESCRIPTION

The present disclosure, among other things, proposes a method for operating an electric vehicle in reverse.

FIG.1depicts an electrified vehicle112that may be referred to as a plug-in hybrid-electric vehicle (PHEV), a battery electric vehicle (BEV), a mild hybrid-electric vehicle (MHEV), and/or a full hybrid electric vehicle (FHEV). A plug-in hybrid-electric vehicle112may comprise one or more electric machines114mechanically coupled to a hybrid transmission116. The electric machines114may be capable of operating as a motor or a generator. In addition, the hybrid transmission116is mechanically coupled to an engine118. The hybrid transmission116is also mechanically coupled to a drive shaft120that is mechanically coupled to the wheels122. The hybrid transmission may be switchable between one or more forward gear and a reverse gear to allow the vehicle112to switch driving direction. In case that the vehicle112is a BEV without the engine118, the transmission116may be a single speed transmission mechanically coupled between the electric machines114and the drive shaft120. The vehicle112may switch the driving direction by changing the rotation direction of the electric machine114. In other words, the vehicle112may drive in a forward direction when the electric machine114rotates in one direction, and drive in reverse direction when the electric machine114rotates in another direction. The electric machines114can provide propulsion and braking capability when the engine118is turned on or off. The electric machines114may also act as generators and can provide fuel economy benefits by recovering energy that would normally be lost as heat in a friction braking system. The electric machines114may also reduce vehicle emissions by allowing the engine118to operate at more efficient speeds and allowing the hybrid-electric vehicle112to be operated in electric mode with the engine118off under certain conditions.

A traction battery or battery pack124may store energy that can be used by the electric machines114. The vehicle battery pack124may provide a high voltage direct current (DC) output. The traction battery124may be electrically coupled to one or more power electronics modules126(such as a traction inverter). One or more contactors125may isolate the traction battery124from other components when opened and connect the traction battery124to other components when closed. The power electronics module126is also electrically coupled to the electric machines114and provides the ability to bi-directionally transfer energy between the traction battery124and the electric machines114. For example, a traction battery124may provide a DC voltage while the electric machines114may operate with a three-phase alternating current (AC) to function. The power electronics module126may convert the DC voltage to a three-phase AC current to operate the electric machines114. In a regenerative mode, the power electronics module126may convert the three-phase AC current from the electric machines114acting as generators to DC voltage compatible with the traction battery124.

The vehicle112may include a variable-voltage converter (VVC) (not shown) electrically coupled between the traction battery124and the power electronics module126. The VVC may be a DC/DC boost converter configured to increase or boost the voltage provided by the traction battery124. By increasing the voltage, current requirements may be decreased leading to a reduction in wiring size for the power electronics module126and the electric machines114. Further, the electric machines114may be operated with better efficiency and lower losses.

In addition to providing energy for propulsion, the traction battery124may provide energy for other vehicle electrical systems. The vehicle112may include a DC/DC converter module128that converts the high voltage DC output of the traction battery124to a low voltage DC supply that is compatible with low-voltage vehicle loads. An output of the DC/DC converter module128may be electrically coupled to an auxiliary battery130(e.g., 12V battery) for charging the auxiliary battery130. The low-voltage systems having one or more low-voltage loads131that may be electrically coupled to the auxiliary battery130. One or more electrical loads132may be coupled to the high-voltage bus/rail. The electrical loads132may have an associated controller that operates and controls the electrical loads146when appropriate. Examples of electrical loads132may be a fan, an electric heating element, and/or an air-conditioning compressor.

The electrified vehicle112may be configured to recharge the traction battery124from an external power source134. The external power source134may be a connection to an electrical outlet. The external power source134may be electrically coupled to a charger or electric vehicle supply equipment (EVSE)136. The external power source134may be an electrical power distribution network or grid as provided by an electric utility company. The EVSE136may provide circuitry and controls to regulate and manage the transfer of energy between the power source134and the vehicle112. The external power source134may provide DC or AC electric power to the EVSE136. The EVSE136may have a charge connector138for plugging into a charge port140of the vehicle112. The charge port140may be any type of port configured to transfer power from the EVSE136to the vehicle112. The charge port140may be electrically coupled to a charger or on-board power conversion module142. The power conversion module142may condition the power supplied from the EVSE136to provide the proper voltage and current levels to the traction battery124. The power conversion module142may interface with the EVSE136to coordinate the delivery of power to the vehicle112. The EVSE connector138may have pins that mate with corresponding recesses of the charge port140. Alternatively, various components described as being electrically coupled or connected may transfer power using a wireless inductive coupling.

The vehicle112may be provided with various sensors148to perform various measurements. As a few non-limiting examples, the sensors148may include a radar (e.g. ultrasonic sensor) or Lidar sensor configured to detect a surrounding environment near the vehicle. The sensors148may further include one or more cameras configured to capture images from the vehicle112. The cameras148may include a front view camera configured to a front view image of the vehicle112and rear view camera configured to capture a review image of the vehicle112. The cameras148may further include a surrounding view camera system configured to capture a surrounding view image of the vehicle112. Signals from the sensors148may be used by the vehicle112to enable driving assistant features such as lane keep assist, parking assist or the like. The sensor data may be transmitted to a computing platform150and/or one or more electronic control units (ECUs)152for processing and analysis (to be discussed in detail below).

Referring toFIG.2, an example block topology of a vehicle system200of one embodiment of the present disclosure is illustrated. As an example, the system200may include the SYNC system manufactured by The Ford Motor Company of Dearborn, Michigan. It should be noted that the illustrated system200is merely an example, and more, fewer, and/or differently located elements may be used.

As illustrated inFIG.2, the computing platform150may include one or more processors206configured to perform instructions, commands, and other routines in support of the processes described herein. For instance, the computing platform150may be configured to execute instructions of vehicle applications208to provide features such as navigation, remote controls, and wireless communications. Such instructions and other data may be maintained in a non-volatile manner using a variety of types of computer-readable storage medium210. The computer-readable medium210(also referred to as a processor-readable medium or storage) includes any non-transitory medium (e.g., tangible medium) that participates in providing instructions or other data that may be read by the processor206of the computing platform150. Computer-executable instructions may be compiled or interpreted from computer programs created using a variety of programming languages and/or technologies, including, without limitation, and either alone or in combination, Java, C, C++, C#, Objective C, Fortran, Pascal, Java Script, Python, Perl, and PL/SQL.

The computing platform150may be provided with various features allowing the vehicle occupants/users to interface with the computing platform150. For example, the computing platform150may receive input from HMI controls212configured to provide for occupant interaction with the vehicle112. As an example, the computing platform150may interface with one or more buttons, switches, knobs, or other HMI controls configured to invoke functions on the computing platform150(e.g., steering wheel buttons, a push-to-talk button, instrument panel controls, etc.).

The computing platform150may also drive or otherwise communicate with one or more displays214configured to provide visual output to vehicle occupants by way of a video controller216. In some cases, the display214may be a touch screen further configured to receive user touch input via the video controller216, while in other cases the display214may be a display only, without touch input capabilities. As a few non-limiting examples, the display214may be implemented as a liquid crystal display (LCD) screen mounted on the dashboard inside the vehicle112. The computing platform150may also drive or otherwise communicate with one or more speakers218configured to provide audio output and input to vehicle occupants by way of an audio controller220.

The computing platform150may also be provided with navigation and route planning features through a navigation controller222configured to calculate navigation routes responsive to user input via, for example, the HMI controls212, and output planned routes and instructions via the speaker218and the display214. Location data that is needed for navigation may be collected from a global navigation satellite system (GNSS) controller224configured to communicate with multiple satellites and calculate the location of the vehicle112. The GNSS controller224may be configured to support various current and/or future global or regional location systems such as global positioning system (GPS), Galileo, Beidou, Global Navigation Satellite System (GLONASS) and the like. Map data used for route planning may be stored in the storage210as a part of the vehicle data226. Navigation software may be stored in the storage210as one of the vehicle applications208.

The computing platform150may be further configured to communicate with various components of the vehicle112via one or more in-vehicle networks228. The in-vehicle network228may include, but is not limited to, one or more of a controller area network (CAN), an Ethernet network, and a media-oriented system transport (MOST), as some examples. Furthermore, the in-vehicle network228, or portions of the in-vehicle network228, may be a wireless network accomplished via Bluetooth low-energy (BLE), Wi-Fi, UWB, or the like.

The computing platform150may be configured to communicate with various electronic control units (ECUs)152of the vehicle112configured to perform various operations. For instance, the ECUs152may include a telematics control unit (TCU)230configured to control telecommunication between vehicle112and a communication network232through a wireless connection234using a modem236. The wireless connection234may be in the form of various communication networks, for example, a cellular network. Through the communication network232, the vehicle may access one or more servers238to access various content for various purposes. It is noted that the terms communication network and server are used as general terms in the present disclosure and may include any computing network involving carriers, routers, computers, controllers, circuitry or the like configured to store data and perform data processing functions and facilitate communication between various entities.

The ECUs152may further include a powertrain control module (PCM)240configured to operate the drivetrain of the vehicle112. In the driving mode, the PCM240may monitor vehicle status data such as the speed and operate the engine118, electric machine116and vehicle transmission114to adapt to various driving needs. In the regenerative mode, the PCM240may operate the electric machine114operating as a generator to convert the AC current generated by the vehicle motion to DC voltage compatible with the traction battery124. The PCM240may be further configured to impose a reverse speed limiter to the drivetrain to limit a maximum speed the vehicle112may operate in reverse (e.g. 20 mph). The reverse speed limiter operated by the PCM240may be temporarily disabled or lessened responsive to a user input via the HMI controls212(to be discussed in detail below). The ECUs152may further include an autonomous driving controller (ADC)242configured to monitor and operate autonomous driving and driving assistant features of the vehicle112. For instance, the ADC242may be configured to operate a lane keep assist feature in reverse using sensor data from the sensors148. The lane keep assist feature in reverse may be particularly useful when the reverse speed limiter is disabled or lessened and the vehicle112travels in a backward direction at a high rate of speed.

Referring toFIG.3, an example flow diagram of process300for the special reverse drive mode is illustrated. With continuing reference toFIGS.1and2, process300may be implemented via the computing platform150in combination with other components of the vehicle112. In general, the special reverse drive mode allows the user to temporarily disable or lessen the involvement of the reverse speed limiter such that the vehicle112may operate in reverse at a high rate of speed. At operation302, responsive to predicting the special reverse drive mode is to be used, the process proceeds to operation304and the computing platform150verifies if the special reverse drive mode is available based on the location of the vehicle112. The prediction of the special reverse drive mode may be triggered responsive to a user input to the vehicle112. For instance, in case that the vehicle112is an emergency vehicle (e.g. a police vehicle),302may be triggered by a user input activating the emergency light and/or siren. Responsive to the trigger, the computing platform150obtains a current vehicle location via the GNSS controller224and verifies the location against a database stored in the storage210as a part of the vehicle data226to determine if the special reverse drive mode is available/permitted at the current location. The special reverse drive mode (i.e. disabling or lessening the reverse speed limiter) may be prohibited or restricted within certain geofences such as school zone, busy business district or the like. Since the vehicle may be in motion when the prediction is triggered at operation302, the computing platform150may be further configured to predict a location at which the special reverse drive mode will be activated via the navigation controller222and determine the availability of the special reverse drive mode using the predicted location. Additionally or alternatively, the computing platform150may use a remote database located at the cloud server238to verify if the special reverse drive mode is available in addition to or in lieu of the database226stored in the storage210.

If the computing platform150determines that the special reverse drive mode is not permitted based on the vehicle location, the process returns to operation302. Otherwise, if the computing platform150verifies that the special reverse drive mode is permitted, the process proceeds to operation308and the computing platform150further determines a first maximum speed in reverse at the vehicle location (current or predicted) via the database at the storage210and/or the cloud server238. The first maximum speed may be a general speed limit in reverse imposed on the vehicle112based on geofence. For instance, a 60 mph maximum speed in reverse may be imposed on the vehicle112in the city whereas there is no maximum speed in reverse in the countryside. The first general maximum speed may be further dependent on traffic condition, weather and real-time events received from the server238. For instance, the computing platform150may reduce the first general maximum speed in the city from 60 mph to 40 mph responsive to detecting a temporary construction work zone and/or detecting a raining weather condition in the area. At operation310, the computing platform150activates sensors148and starts to measure a surrounding condition near the vehicle112, and determines a second maximum speed in reverse specific to the condition near the vehicle112. While the first general maximum speed based on the geofence may reflect the general conditions for the vehicle location, the second maximum speed determined by the vehicle using sensor data may reflect more specific conditions near the vehicle112such that the vehicle112may operate in reverse in a safely manner. As an example, the sensors (e.g. camera, lidar or the like)148may measure and detect objects behind the vehicle112and adjust the maximum speed accordingly. As an example, the computing platform150may determine the second specific maximum speed in reverse is 80 mph on a widely open road with few objects detected near the vehicle (e.g., a rural area) as compared to 30 mph in a narrow street with multiple objects behind the vehicle being detected (e.g., a city). The final speed limit in reverse will be determined as the lower of the first and second maximum speeds discussed above. At operation312, responsive to detecting user input activating the special reverse drive mode, the process proceeds to operation314and the PCM240disables or lessens the reverse speed limiter and operates the vehicle in reverse within the speed limit assisted by safety features operated by the ADC242. The vehicle112may be configured to enter the special reverse drive mode responsive to receiving a predefined user input such as pressing a button after shifting to reverse gear. The computing platform150may provide visual and/or audio feedback confirming the activation of the special reverse drive mode. The computing platform150may further output the speed limit in reverse to the drive via the HMI controller212. While operating in the special reverse drive mode, the ADC242may provide autonomous driving assistance to the driving such that the vehicle112may drive in reverse at high rate of speed. For instance, the ACD242may activate a reverse lane keep assist feature using data captured via the sensors148while in the special reverse drive mode. The ADC242may further apply automatic braking responsive to detecting an object behind the vehicle to avoid colliding with the object. The ADC242may further apply automatic steering such that the vehicle112may maneuver around objects in an autonomous driving manner.

While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure.