Control device and turning device

A control device includes a processor. The processor is configured to perform a route acquisition process for acquiring route information indicating a target route of a vehicle. The processor is configured to perform a behavior optimization process for correcting, based on at least one of a plurality of state quantities indicating a behavior of the vehicle during traveling, each of a left turning command value and a right turning command value such that the behavior of the vehicle becomes a target behavior. The processor is configured to perform a locus stabilization process for correcting, based on at least one of the state quantities indicating the behavior of the vehicle during traveling, a steering command value such that the vehicle travels on the target route.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2019-111943 filed on Jun. 17, 2019, incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a control device and a turning device for independently turning steered wheels disposed on the right and left of a vehicle.

2. Description of Related Art

There is a turning device for a vehicle in which a steering wheel and a turning mechanism are mechanically disconnected from each other. The turning device independently controls steered angles of steered wheels. For example, Japanese Unexamined Patent Application Publication No. 2009-208492 (JP 2009-208492 A) describes a technique that controls, when a driver's steering operation exceeds a limit, a driving force and the steered angles of the steered wheels to turn the vehicle in accordance with a driver's intention while maintaining a stable vehicle posture. In addition, Japanese Unexamined Patent Application Publication No. 2008-254630 (JP 2008-254630 A) describes a technique that, in a vehicle in which four wheels can be turned independently, changes a turning state depending on the vehicle speed to improve the stability of the vehicle and reduce load applied on the turning mechanism.

SUMMARY

However, when the steered angles of the right and left steered wheels are individually corrected when the vehicle is traveling on a curve for purposes such as to improve the marginal performance of the vehicle behavior and to suppress the energy loss of the steered wheels, the total sum of the tire lateral force changes. The inventors have found that the above effect causes fluctuation in the turning state of the vehicle, and the vehicle may thus deviate from a desired travel route while traveling.

The present disclosure provides a control device and a turning device that can individually correct steered angles of right and left steered wheels when a vehicle is traveling on a curve to adjust a behavior of the vehicle and cause the vehicle to travel in accordance with a target route.

A control device according to a first aspect of the present disclosure is configured to independently control a steered angle of each of a left steered wheel disposed on the left with respect to a traveling direction of a vehicle and a right steered wheel disposed on the right with respect to the traveling direction of the vehicle. The control device includes a processor. The processor is configured to perform a steered angle determination process for determining, based on a steering command value indicating a steering direction of the vehicle, a left turning command value indicating the steered angle of the left steered wheel and a right turning command value indicating the steered angle of the right steered wheel. The processor is configured to perform a route acquisition process for acquiring route information indicating a target route of the vehicle. The processor is configured to perform a behavior optimization process for correcting, based on at least one of a plurality of state quantities indicating a behavior of the vehicle during traveling, each of the left turning command value and the right turning command value such that the behavior of the vehicle becomes a target behavior. The processor is configured to perform a locus stabilization process for correcting, based on at least one of the state quantities indicating the behavior of the vehicle during traveling, the steering command value such that the vehicle travels on the target route.

In the control device according to the first aspect of the present disclosure, the processor may be configured to acquire the route information based on the steering command value. In the control device according to the first aspect of the present disclosure, the processor may be configured to acquire the route information from a traveling control device that is configured to control or assist travel of the vehicle. In the control device according to the first aspect of the present disclosure, the processor may be configured to perform, when the processor determines that the vehicle is in a predetermined state based on at least one of the state quantities indicating the behavior of the vehicle during traveling, a priority adjustment process that changes a control priority of the locus stabilization process with respect to a control priority of the behavior optimization process from the control priority of the locus stabilization process with respect to the control priority of the behavior optimization process when the vehicle is not in the predetermined state.

A turning device according to a second aspect of the present disclosure includes a left turning mechanism, a right turning mechanism, and a control device. The left turning mechanism has a left actuator configured to turn a left steered wheel disposed on the left with respect to a traveling direction of a vehicle. The right turning mechanism has a right actuator configured to turn a right steered wheel disposed on the right with respect to the traveling direction of the vehicle. The control device is configured to independently control a steered angle of each of the left steered wheel and the right steered wheel. The control device includes a processor. The processor is configured to perform a steered angle determination process for determining, based on a steering command value indicating a steering direction of the vehicle, a left turning command value indicating the steered angle of the left steered wheel and a right turning command value indicating the steered angle of the right steered wheel. The processor is configured to perform a route acquisition process for acquiring route information indicating a target route of the vehicle. The processor is configured to perform a behavior optimization process for correcting, based on at least one of a plurality of state quantities indicating a behavior of the vehicle during traveling, each of the left turning command value and the right turning command value such that the behavior of the vehicle becomes a target behavior. The processor is configured to perform a locus stabilization process for correcting, based on at least one of the state quantities indicating the behavior of the vehicle during traveling, the steering command value such that the vehicle travels on the target route.

According to the present disclosure, it is possible to independently control the right and left steered wheels to optimize the behavior of the vehicle, and to steer the vehicle such that the vehicle travels in accordance with the target route.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of a control device and a turning device according to the present disclosure will be described below with reference to the drawings. Numerical values, shapes, materials, components, positional relationships and connections of components, steps, order of steps, and the like described in the following embodiments are merely examples and are not intended to limit the applicable embodiment. A plurality of applicable embodiments may be described below as one embodiment. Components not described in the claims are described as optional components with respect to the present disclosure according to the corresponding claims. The drawings are schematic diagrams in which emphasis, omission, and scale adjustment are made as appropriate to illustrate the present disclosure, and may differ from actual shapes, positional relationships, and scales.

First, an overall configuration of a turning device100for a vehicle101according to the embodiment of the present disclosure will be described.FIG.1is a block diagram illustrating an overall configuration of a turning device according to the embodiment. The turning device100is a device that can independently turn a left steered wheel110and a right steered wheel120that are mounted on the vehicle101such as a passenger vehicle and that are not connected to each other by a mechanical element such as a link. In the present embodiment, the turning device100constitutes a linkless steer-by-wire system that can turn right and left steered wheels based on a signal output by steering a steering member103. The turning device100includes the steering member103serving as a steering member operated by a driver for steering, the left steered wheel110and the right steered wheel120disposed on the front side of the vehicle101in a traveling direction, a left turning mechanism111for individually turning the left steered wheel110, and a right turning mechanism121for individually turning the right steered wheel120.

The left turning mechanism111and the right turning mechanism121respectively include a left actuator112and a right actuator122that are controlled in accordance with a rotation operation of the steering member103. In the present embodiment, the left actuator112and the right actuator122are electric motors.

The left turning mechanism111has a left turning structure113for turning the left steered wheel110. The right turning mechanism121has a right turning structure123for turning the right steered wheel120. The left turning structure113and the right turning structure123are supported by a suspension with respect to the vehicle body. The left turning structure113turns the left steered wheel110with a rotational driving force received from the left actuator112. The right turning structure123turns the right steered wheel120with a rotational driving force received from the right actuator122.

The turning device100further includes a steering angle sensor131that detects a steering angle of the steering member103. Here, the steering angle sensor131detects a rotation angle and an angular velocity of a rotation shaft of the steering member103and outputs the detected rotation angle and angular velocity as a steering command value S. The turning device100includes a left sensor114that detects a steered angle of the left steered wheel110and a right sensor124that detects a steered angle of the right steered wheel120.

The vehicle101is further provided with a vehicle speed sensor132for detecting a speed V of the vehicle101and an inertial measurement device133. The inertial measurement device133includes, for example, a gyro sensor, an acceleration sensor, a geomagnetic sensor, and the like. The inertial measurement device133detects the acceleration, angular velocity, and the like of the vehicle101in three axial directions. Examples of the three axial directions regarding the angular velocity are a yawing direction, a pitching direction, and a rolling direction. The inertial measurement device133detects, for example, the angular velocity in the yawing direction (also referred to as “yaw rate”). The inertial measurement device133may also detect the angular velocity in the pitching direction and the rolling direction.

The vehicle speed sensor132, the inertial measurement device133, and the like are connected to a state quantity processing unit130. The state quantity processing unit130outputs information received from various sensors to a control device140as state quantities Q. The state quantity processing unit130may generate the state quantities Q indicating a behavior of the vehicle101by calculating information received from the various sensors and output the generated state quantities Q to the control device140.

The turning device100includes the control device140and a storage device105. The storage device105may be provided separately from the control device140, may be electrically connected to the control device140, or may be included in the control device140. The left turning mechanism111includes a left electronic control unit (ECU)115, and the right turning mechanism121includes a right ECU125. The control device140is electrically connected to the left ECU115, the right ECU125, the steering angle sensor131, the vehicle speed sensor132, and the inertial measurement device133. The left ECU115is electrically connected to the control device140, the left sensor114, the left actuator112, and the right ECU125. The right ECU125is electrically connected to the control device140, the right sensor124, the right actuator122, and the left ECU115. Communication between the control device140, the left ECU115, the right ECU125, the left actuator112, the right actuator122, the state quantity processing unit130, and each sensor may be performed via an on-vehicle network such as controller area network (CAN).

The control device140performs feedback control based on information acquired from the steering angle sensor131, the vehicle speed sensor132, the inertial measurement device133, the left ECU115, and the right ECU125, and outputs an appropriate left turning command value θLto the left ECU115and an appropriate right turning command value θRto the right ECU125.

The storage device105can store various types of information, and can also retrieve and output the stored information. The storage device105is implemented by a storage unit such as a hard disk drive, a solid state drive (SSD), and a semiconductor memory such as a read-only memory (ROM), a random access memory (RAM), and a flash memory.

The control device140, the left ECU115, and the right ECU125may be constituted by a microcomputer including a processor such as a central processing unit (CPU) or a digital signal processor (DSP), and a memory. The memory may be a volatile memory such as the RAM, a non-volatile memory such as the ROM, or the storage device105. Some or all of the functions of the control device140, the state quantity processing unit130, the left ECU115, and the right ECU125may be implemented by the CPU that executes a program stored in the ROM using the RAM as a working memory.

Next, details of the control device140will be described.FIG.2is a block diagram illustrating a functional configuration of the control device140. The control device140is a device that independently controls the steered angles of the right steered wheel120and the left steered wheel110disposed on the right and left with respect to the traveling direction of the vehicle101. The control device140includes a steered angle determination unit141for executing a steered angle determination process, a route acquisition unit142for executing a route acquisition process, a behavior optimization unit143for executing a behavior optimization process, and a locus stabilization unit144for executing a locus stabilization process. In the present embodiment, the control device140includes a priority adjustment unit145for executing a priority adjustment process. Vehicle speed control of the vehicle101is executed by a drive control unit135that controls an engine, a motor, and the like based on information from a depression sensor134attached to an accelerator pedal and the like for detecting a depression amount of the pedal.

The steered angle determination unit141calculates a left turning command value indicating a steered angle of the left steered wheel110and a right turning command value indicating a steered angle of the right steered wheel120based on the steering command value indicating the steering direction of the vehicle101. In the present embodiment, the steered angle determination unit141acquires the rotation angle of the rotating shaft of the steering member103from the steering angle sensor131as the steering command value S1, and performs calculation using an inner wheel steered angle and an outer wheel steered angle based on a so-called overall steering gear ratio that is a predetermined ratio and the Ackermann-Jeantaud theory, and outputs a left turning command value θL1and a right turning command value θR1.

The left ECU115drives the left actuator112in accordance with the acquired left turning command value θL1to turn the left steered wheel110. The right ECU125drives the right actuator122in accordance with the acquired right turning command value θR1to turn the right steered wheel120.

The route acquisition unit142acquires route information indicating a target route of the vehicle101. In the present embodiment, since the vehicle101is steered based only on the driver's steering operation of the steering member103, the route acquisition unit142acquires information from the steering angle sensor131as the route information. The route acquisition unit142may generate route information by performing calculations based on the information from the steering angle sensor131, for example, the rotation angle and angular velocity of the steering member103. Also in this case, the generated route information is included in the acquired route information. Further, the route information may be acquired by adding the vehicle speed.

The behavior optimization unit143corrects the left turning command value θL1and the right turning command value θR1so that the behavior of the vehicle101becomes a target behavior based on at least one of the plurality of state quantities Q indicating the behavior of the vehicle101during traveling. The target behavior of the behavior optimization unit143is not particularly limited. For example, the target may be set to improve the driver's sense of security and occupants' comfort by slightly correcting the right and left steered angles depending on whether the vehicle101is traveling at a low speed or the vehicle101is traveling at a high speed. Alternatively, the target may be set to suppress the energy loss caused by the steered wheels as much as possible to improve the fuel efficiency of the vehicle101as a whole, or the target may be set to improve the marginal performances of the vehicle101regarding slip angles and turning control by controlling the tire lateral force using the steered angles of the steered wheels.

The state quantity Q used by the behavior optimization unit143for the calculation is information acquired from the state quantity processing unit130, and is, for example, the yaw rate, the vehicle speed, the acceleration in the traveling direction, the acceleration in the right and left direction, the actual steered angle of the left steered wheel110, the actual steered angle of the right steered wheel120and the like that are acquired from the vehicle speed sensor132, the inertial measurement device133, the left sensor114, and the right sensor124of the vehicle101and the like. The behavior optimization unit143may acquire the state quantity Q generated by the state quantity processing unit130based on information acquired from various sensors through calculations based on a known theory or the like. For example, the state quantity processing unit130may estimate the state quantity Q such as a vehicle body slip angle, a tire slip angle, and a tire vertical load, and the behavior optimization unit143may correct the right and left turning command values based on the estimated state quantity Q.

The locus stabilization unit144corrects the steering command value S1based on at least one of the state quantities Q indicating the behavior of the vehicle101during traveling so that the vehicle101travels on the target route acquired by the route acquisition unit142. With the right and left turning command values corrected by the behavior optimization unit143, the steered angles of the right and left steered wheels change individually. Since the total sum of the generated tire lateral force changes due to this change and the traveling locus (turning locus) of the vehicle101on the curve fluctuates, the locus stabilization unit144corrects the steering command value S1. For example, the locus stabilization unit144derives a target yaw rate from the target route and the state quantity Q acquired from the state quantity processing unit130, and corrects the steering command value S1so as to maintain the target yaw rate. Further, the locus stabilization unit144derives a target curvature at the time of turning (a reciprocal of the turning radius) from the target route and the state quantity Q, and corrects the steering command value S1so as to maintain the target curvature.

When the priority adjustment unit145determines that the vehicle101is in a predetermined state based on at least one of the state quantities Q indicating the behavior of the vehicle101during traveling, the priority adjustment unit145changes the control priority of the locus stabilization unit144with respect to the control priority of the behavior optimization unit143from that when the vehicle101is not in the predetermined state. Thus, the priority adjustment unit145adjusts control priorities of the behavior optimization unit143that individually performs feedback correction on the left turning command value θL1and the right turning command value θR1based on the state quantity Q acquired from the state quantity processing unit130and the locus stabilization unit144that performs feedback correction on the steering command value S1for generating the left turning command value θL1and the right turning command value θR1based on the same state quantity Q acquired from the state quantity processing unit130, to implement smooth control without causing vibration or the like.

The priority adjustment of the priority adjustment unit145is performed by, for example, changing each time constant of the behavior optimization unit143and the locus stabilization unit144. Specifically, for example, the priority adjustment unit145can make the time constant different by adjusting at least one of the control cycle and the control gain of the behavior optimization unit143and the locus stabilization unit144.

In the present embodiment, the predetermined state is assumed to be a limit state of the vehicle101. When the priority adjustment unit145determines that the vehicle101is in the limit state based on the yaw rate, the vehicle speed, and the like, the priority adjustment unit145shortens the control cycle of the behavior optimization unit143from that during normal traveling to increase the control priority of the behavior optimization unit143, and lengthens the control cycle of the locus stabilization unit144from that during normal traveling to reduce the control priority of the locus stabilization unit144. Specifically, for example, the priority adjustment unit145changes the lengths of the control cycles of the behavior optimization unit143and the locus stabilization unit144so that the ratio of the control cycle of the locus stabilization unit144with respect to the control cycle of the behavior optimization unit143during normal traveling is reversed when the vehicle101is in the limit state. Alternatively, the priority adjustment unit145may set the control cycle of the behavior optimization unit143shorter than that during normal traveling and set the control cycle of the locus stabilization unit144longer than that during normal traveling, so that the ratio of the control cycle of the locus stabilization unit144with respect to the control cycle of the behavior optimization unit143during normal traveling is not reversed even in the limit state. Note that the control gain (for example, at least one of the gains in proportional-integral-derivative (PID) control) may be adjusted instead of the control cycle.

In the present embodiment, the following two types of feedback control are executed independently: individual correction of the right and left turning command values instructing the right and left steered angles based on the state quantities Q that represent the behavior of the vehicle101such as the tire lateral force; and correction of the steering command value S1used for determining the right and left steering command values based on the state quantities Q. Therefore, for example, it is possible to steer the vehicle101with a so-called on-rails feeling such that the vehicle101is steered in accordance with the travel route in response to the steering operation of the steering member103while maintaining the behavior of the vehicle101to have a small energy loss.

Further, when the vehicle101is in a limit state such as when the state of the road surface suddenly changes, the vehicle101can be controlled smoothly without exceeding the limit state by adjusting the control priorities of the behavior optimization unit143and the locus stabilization unit144.

The applicable embodiment is not limited to the above embodiment. For example, other embodiments implemented by combining components described in the specification as desired or by eliminating one or more of the components may be used as the embodiment of the present disclosure. Modifications of the embodiments obtained by making various modifications that may occur to those skilled in the art without departing from the scope of the present disclosure, that is, the scope defined by the wording of the claims, are also encompassed in the present disclosure.

For example, vehicle101may have functions such as an assist mode that allows the steering operation of the vehicle101via the steering member103to be assisted, and an automated driving mode that allows automated driving without using the steering member103. In this case, as shown inFIG.3, the vehicle101includes a traveling sensor162that enables functions such as automated driving, and a traveling control device106that controls or assists traveling of the vehicle101based on information from the traveling sensor162.

The traveling sensor162is a sensor that acquires information necessary for automated traveling of the vehicle101. The traveling sensor162is not particularly limited, and may include a plurality of types of sensors. Examples of the traveling sensor162include a camera that acquires information for generating a travel route such as a positions of marks including a white line provided on a road surface, a sensor that acquires the position of the vehicle101in map information, and a radar for detecting an obstacle in front of the vehicle101.

The traveling control device106controls the traveling of the vehicle101based on information from the traveling sensor162and the like. The traveling control device106determines a target vehicle speed of the vehicle101and outputs a vehicle speed command value VCcorresponding to the target vehicle speed to the drive control unit135. The traveling control device106further includes a route generation unit161. The route generation unit161generates a route on which the vehicle101should travel based on the map information and the information from the traveling sensor162, and outputs the route as route information. The traveling control device106outputs a steering command value S2based on the current position of the vehicle101, the route information generated by the route generation unit161and the like.

In the assist mode and the automated driving mode and the like, the steered angle determination unit141of the control device140generates a left turning command value θL2and a right turning command value θR2based on the steering command value S2output from the traveling control device106. The behavior optimization unit143corrects the left turning command value θL2and the right turning command value θR2based on the state quantity Q regardless of whether the vehicle101is in the assist mode or the automated driving mode. The route acquisition unit142adds the vehicle speed command value VCoutput from the traveling control device106to the route information acquired from the route generation unit161, and outputs the route information. The locus stabilization unit144corrects the steering command value S2based on the acquired route information.

InFIG.3, there is no priority adjustment unit145that relatively adjusts the control priorities of the locus stabilization unit144and the behavior optimization unit143. In such a case, at least one of the locus stabilization unit144and the behavior optimization unit143may adjust the control priorities based on the state quantities Q.

The technique of the present disclosure may be implemented by a storage medium such as a system, an apparatus, a method, an integrated circuit, a computer program, and a computer-readable storage disk, and may be implemented by a desired combination of the system, the apparatus, the method, the integrated circuit, the computer program, and the storage medium.

For example, each processing unit included in the above embodiments is typically implemented by a large-scale integration (LSI) circuit that is an integrated circuit. The processing units may be individually integrated into one chip, or may be integrated into one chip that includes some or all of the processing units.

The integrated circuit is not limited to the LSI circuit, and may be implemented by a dedicated circuit or a general-purpose processor. A field-programmable gate array (FPGA) that can be programmed after manufacture of the LSI circuit, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells inside the LSI circuit may be used.

In the above embodiments, each component may be constituted by a dedicated hardware, or may be implemented by executing a software program suitable for each component. Each component may be implemented by a program execution unit of a processor or the like such as a CPU that reads and executes a software program stored in a storage medium such as a hard disk or a semiconductor memory.

A part or all of the above components may be constituted by a removable integrated circuit (IC) card or a single module. The IC card or the module is a computer system constituted by a microprocessor, a ROM, a RAM, and the like. The IC card or the module may include the above-described LSI circuit or a system LSI circuit. The IC card or the module implements its functions by a microprocessor that operates in accordance with a computer program. The IC card and the module may have tamper resistance.

The technique related to the present disclosure is useful for a turning device in which a mechanism for turning each steered wheel is independently provided.