Controls and Steering

Abstract

The present invention provides a control device and a steering device, wherein the control device includes a processor (140). The processor (140) is configured to perform a route acquisition process for acquiring route information indicating a target route of a vehicle. The processor (140) is configured to perform a behavior optimization process for correcting each of a left steering command value and a right steering command value based on at least one state quantity among a plurality of state quantities indicating the behavior of the vehicle during driving, so that the behavior of the vehicle becomes a target behavior. The processor (140) is configured to perform a trajectory stabilization process for correcting a steering command value based on at least one state quantity among a plurality of state quantities indicating the behavior of the vehicle during driving, so that the vehicle drives on the target route.

Description

Technical Field

[0001] The present invention relates to a control device and a steering device for independently steering steering wheels arranged on the right and left sides of a vehicle. Background Art

[0002] There is a steering device for a vehicle in which a steering wheel and a steering mechanism are mechanically disconnected from each other. The steering device independently controls the steering angle of the steering wheel. For example, Japanese Unexamined Patent Application Publication No. 2009-208492 (JP 2009-208492 A) describes a technology as follows: when the driver's steering operation exceeds a limit, the driving force and the steering angle of the steering wheel are controlled so that the vehicle is steered according to the driver's intention and at the same time a stable vehicle posture is maintained. In addition, Japanese Unexamined Patent Application Publication No. 2008-254630 (JP 2008-254630 A) describes a technology as follows: in a vehicle in which four wheels can be steered independently, the steering state is changed according to the vehicle speed to improve the stability of the vehicle and reduce the load applied to the steering mechanism. Summary of the invention

[0003] However, when the vehicle is traveling on a curve, when the steering angles of the right and left steering wheels are individually corrected for purposes such as improving marginal performance of vehicle behavior and suppressing energy loss of the steering wheels, the sum of the tire lateral forces changes. The inventors of the present invention have found that the above effect causes fluctuations in the vehicle's steering state, and the vehicle may therefore deviate from a desired driving route while traveling.

[0004] The present invention provides a control device and a steering device, which can individually correct the steering angles of a right steering wheel and a left steering wheel when a vehicle travels on a curve to adjust the behavior of the vehicle and make the vehicle travel according to a target route.

[0005] The control device according to the first aspect of the present invention is configured to independently control the steering angle of each of the left steering wheel arranged on the left side relative to the driving direction of the vehicle and the right steering wheel arranged on the right side relative to the driving direction of the vehicle. The control device includes a processor. The processor is configured to perform a steering angle determination process for determining a left steering command value indicating the steering angle of the left steering wheel and a right steering command value indicating the steering angle of the right steering wheel based on a steering command value indicating the steering direction of the vehicle. 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 each of the left steering command value and the right steering command value based on at least one state quantity of a plurality of state quantities indicating the behavior of the vehicle during driving, so that the behavior of the vehicle becomes a target behavior. The processor is configured to perform a trajectory stabilization process for correcting the steering command value based on at least one state quantity of the state quantities indicating the behavior of the vehicle during driving, so that the vehicle travels on the target route.

[0006] In a control device according to the first aspect of the present invention, the processor may be configured to obtain route information based on a steering command value. In a control device according to the first aspect of the present invention, the processor may be configured to obtain route information from a travel control device configured to control or assist the travel of a vehicle. In a control device according to the first aspect of the present invention, the processor may be configured to perform a priority adjustment process 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 driving, the priority adjustment process changes the control priority of the trajectory stabilization process relative to the control priority of the behavior optimization process when the vehicle is not in the predetermined state to the control priority of the trajectory stabilization process relative to the control priority of the behavior optimization process.

[0007] In a control device according to the first aspect of the present invention, the control device can be arranged in a steering device including a left steering mechanism and a right steering mechanism, wherein the left steering mechanism has a left actuator configured to steer a left steering wheel, and the right steering mechanism has a right actuator configured to steer a right steering wheel.

[0008] According to the present invention, the right steering wheel and the left steering wheel can be independently controlled to optimize the behavior of the vehicle and steer the vehicle so that the vehicle travels according to a target route. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0010] Figure 1is a diagram showing an overall configuration of a steering device according to an embodiment;

[0011] Figure 2 is a block diagram showing a functional configuration of a control device and respective components of a vehicle according to an embodiment; and

[0012] Figure 3 is a block diagram showing a functional configuration of a control device and respective components of a vehicle according to another example. DETAILED DESCRIPTION

[0013] The following will describe embodiments of a control device and a steering device according to the present invention with reference to the accompanying drawings. The numerical values, shapes, materials, components, positional relationships and connection relationships of components, steps, the order of steps, etc. described in the following embodiments are only examples and are not intended to limit the present invention. Multiple inventions may be described below as one embodiment. Component descriptions not described in the claims are described as optional components with respect to the invention according to the corresponding claims. The accompanying drawings are schematic diagrams in which emphasis, omissions, and proportional adjustments are appropriately made to illustrate the present invention and may differ from actual shapes, positional relationships, and proportions.

[0014] First, the overall configuration of a steering device 100 for a vehicle 101 according to an embodiment of the present invention will be described. Figure 1 1 is a block diagram showing the overall configuration of a steering device according to an embodiment. The steering device 100 is a device that can independently steer a left steering wheel 110 and a right steering wheel 120 that are mounted on a vehicle 101, such as a passenger vehicle, and are not connected to each other by a mechanical element, such as a connecting rod. In the present embodiment, the steering device 100 constitutes a linkless wire control steering system that can steer the right steering wheel and the left steering wheel based on a signal output by steering a steering member 103. The steering device 100 includes a steering member 103, a left steering mechanism 111, and a right steering mechanism 121, wherein the steering member 103 is used as a driver-operated device for steering the left steering wheel 110 and the right steering wheel 120 arranged on the front side of the vehicle 101 in the direction of travel, the left steering mechanism 111 is used to steer the left steering wheel 110 alone, and the right steering mechanism 121 is used to steer the right steering wheel 120 alone.

[0015] The left steering mechanism 111 and the right steering mechanism 121 include a left actuator 112 and a right actuator 122 , respectively. The left actuator 112 and the right actuator 122 are controlled according to the rotation operation of the steering member 103 . In the present embodiment, the left actuator 112 and the right actuator 122 are electric motors.

[0016] The left steering mechanism 111 has a left steering structure 113 for steering the left steering wheel 110. The right steering mechanism 121 has a right steering structure 123 for steering the right steering wheel 120. The left steering structure 113 and the right steering structure 123 are supported by a suspension relative to the vehicle body. The left steering structure 113 steers the left steering wheel 110 by the rotational driving force received from the left actuator 112. The right steering structure 123 steers the right steering wheel 120 by the rotational driving force received from the right actuator 122.

[0017] The steering device 100 further includes a steering angle sensor 131 that detects a steering angle of the steering member 103. Here, the steering angle sensor 131 detects a rotation angle and an angular velocity of a rotation shaft of the steering member 103 and outputs the detected rotation angle and angular velocity as a steering command value S. The steering device 100 includes a left sensor 114 that detects a steering angle of a left steering wheel 110 and a right sensor 124 that detects a steering angle of a right steering wheel 120.

[0018] The vehicle 101 is also provided with a vehicle speed sensor 132 for detecting a speed V of the vehicle 101 and an inertial measurement device 133. The inertial measurement device 133 includes, for example, a gyro sensor, an acceleration sensor, a geomagnetic sensor, and the like. The inertial measurement device 133 detects acceleration, angular velocity, and the like of the vehicle 101 in three axial directions. An example of three axial directions of angular velocity is a yaw direction, a pitch direction, and a roll direction. The inertial measurement device 133 detects, for example, an angular velocity in the yaw direction (also referred to as a "yaw rate"). The inertial measurement device 133 can also detect angular velocities in the pitch direction and the roll direction.

[0019] The vehicle speed sensor 132, the inertial measurement device 133, and the like are connected to the state quantity processing unit 130. The state quantity processing unit 130 outputs the information received from the various sensors as the state quantity Q to the control device 140. The state quantity processing unit 130 can generate the state quantity Q indicating the behavior of the vehicle 101 by calculating the information received from the various sensors and output the generated state quantity Q to the control device 140.

[0020] The steering device 100 includes a control device 140 and a storage device 105. The storage device 105 may be provided separately from the control device 140, the storage device 105 may be electrically connected to the control device 140, or may be included in the control device 140. The left steering mechanism 111 includes a left electronic control unit (ECU) 115, and the right steering mechanism 121 includes a right ECU 125. The control device 140 is electrically connected to the left ECU 115, the right ECU 125, the steering angle sensor 131, the vehicle speed sensor 132, and the inertial measurement device 133. The left ECU 115 is electrically connected to the control device 140, the left sensor 114, the left actuator 112, and the right ECU 125. The right ECU 125 is electrically connected to the control device 140, the right sensor 124, the right actuator 122, and the left ECU 115. Communication among the control device 140, the left ECU 115, the right ECU 125, the left actuator 112, the right actuator 122, the state quantity processing unit 130, and each sensor may be performed via an in-vehicle network such as a controller area network (CAN).

[0021] The control device 140 performs feedback control based on information acquired from the steering angle sensor 131, the vehicle speed sensor 132, the inertial measurement device 133, the left ECU 115, and the right ECU 125, and outputs an appropriate left steering command value θ to the left ECU 115. L and outputs an appropriate right steering command value θ to the right ECU 125 R .

[0022] The storage device 105 can store various types of information, and can also retrieve and output the stored information. The storage device 105 is 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.

[0023] The control device 140, the left ECU 115, and the right ECU 125 may 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 a RAM, a nonvolatile memory such as a ROM, or a storage device 105. Some or all of the functions of the control device 140, the state quantity processing unit 130, the left ECU 115, and the right ECU 125 may be implemented by the CPU, which executes a program stored in the ROM using the RAM as a working memory.

[0024] Next, the details of the control device 140 will be described. Figure 2is a block diagram showing the functional configuration of the control device 140. The control device 140 is a device that independently controls the steering angles of the right steering wheel 120 and the left steering wheel 110 arranged on the right and left sides relative to the driving direction of the vehicle 101. The control device 140 includes a steering angle determination unit 141 for performing a steering angle determination process, a route acquisition unit 142 for performing a route acquisition process, a behavior optimization unit 143 for performing a behavior optimization process, and a trajectory stabilization unit 144 for performing a trajectory stabilization process. In the present embodiment, the control device 140 includes a priority adjustment unit 145 for performing a priority adjustment process. The vehicle speed control of the vehicle 101 is performed by a drive control unit 135, which controls the engine, the motor, etc. based on information from a pedal sensor 134, wherein the pedal sensor 134 is attached to an accelerator pedal, etc. for detecting the pedal depression amount.

[0025] The steering angle determination unit 141 calculates a left steering command value indicating the steering angle of the left steering wheel 110 and a right steering command value indicating the steering angle of the right steering wheel 120 based on the steering command value indicating the steering direction of the vehicle 101. In the present embodiment, the steering angle determination unit 141 acquires the rotation angle of the rotation shaft of the steering member 103 from the steering angle sensor 131 as the steering command value S1, performs calculation using the inner wheel steering angle and the outer wheel steering angle based on the so-called total steering gear ratio, i.e., a predetermined ratio and the Ackermann-Jeantaud theory, and outputs a left steering command value θ. L1 and the right steering command value θ R1 .

[0026] The left ECU 115 controls the left steering command value θ according to the acquired left steering command value θ. L1 The left actuator 112 is driven to steer the left steering wheel 110. The right ECU 125 controls the left steering wheel 110 according to the acquired right steering command value θ. R1 The right actuator 122 is driven to steer the right steering wheel 120 .

[0027] The route acquisition unit 142 acquires route information indicating a target route of the vehicle 101. In the present embodiment, since the vehicle 101 is turned only based on the driver's steering operation of the steering member 103, the route acquisition unit 142 acquires information from the steering angle sensor 131 as route information. The route acquisition unit 142 can generate route information by performing calculations based on information from the steering angle sensor 131, such as the rotation angle and angular velocity of the steering member 103. In this case as well, the generated route information is also included in the acquired route information. In addition, the route information can be acquired by adding the vehicle speed.

[0028] The behavior optimization unit 143 optimizes the left turning command value θ based on at least one state quantity among a plurality of state quantities Q indicating the behavior of the vehicle 101 during traveling. L1 and the right steering command value θ R1 Correction is performed so that the behavior of the vehicle 101 becomes the target behavior. The target behavior of the behavior optimization unit 143 is not particularly limited. For example, the target may be set to improve the driver's sense of safety and the comfort of the occupants by slightly correcting the right steering angle and the left steering angle depending on whether the vehicle 101 is traveling at a low speed or the vehicle 101 is traveling at a high speed. Alternatively, the target may be set to suppress the energy loss caused by the steering wheel as much as possible to improve the fuel efficiency of the vehicle 101 as a whole, or the target may be set to improve the marginal performance of the vehicle 101 regarding the deviation angle and steering control by controlling the tire lateral force using the steering angle of the steering wheel.

[0029] The state quantity Q used for calculation by the behavior optimization unit 143 is information acquired from the state quantity processing unit 130, and is acquired from the vehicle speed sensor 132, the inertial measurement device 133, the left sensor 114, the right sensor 124, etc. of the vehicle 101, such as the yaw rate, the vehicle speed, the acceleration in the traveling direction, the acceleration in the left and right directions, the actual steering angle of the left steering wheel 110, the actual steering angle of the right steering wheel 120, etc. The behavior optimization unit 143 can acquire the state quantity Q generated by the state quantity processing unit 130 based on the information acquired from the various sensors, through calculation based on a known theory, etc. For example, the state quantity processing unit 130 can estimate the state quantity Q, such as the vehicle body deviation angle, the tire deviation angle, and the tire vertical load, and the behavior optimization unit 143 can correct the right steering command value and the left steering command value based on the estimated state quantity Q.

[0030] The trajectory stabilization unit 144 corrects the steering command value S1 based on at least one of the state quantities Q indicating the behavior of the vehicle 101 during driving, so that the vehicle 101 travels on the target route acquired by the route acquisition unit 142. The steering angle of the right steering wheel and the steering angle of the left steering wheel are changed individually by the right steering command value and the left steering command value corrected by the behavior optimization unit 143. Since the sum of the generated tire lateral forces changes due to the change and the driving trajectory (steering trajectory) of the vehicle 101 on the curve fluctuates, the trajectory stabilization unit 144 corrects the steering command value S1. For example, the trajectory stabilization unit 144 derives a target yaw rate from the target route and the state quantity Q acquired from the state quantity processing unit 130, and corrects the steering command value S1 to maintain the target yaw rate. In addition, the trajectory stabilization unit 144 derives a target curvature (the inverse of the turning radius) when turning from the target route and the state quantity Q, and corrects the steering command value S1 to maintain the target curvature.

[0031] When the priority adjustment unit 145 determines that the vehicle 101 is in a predetermined state based on at least one of the state quantities Q indicating the behavior of the vehicle 101 during driving, the priority adjustment unit 145 changes the control priority of the trajectory stabilization unit 144 relative to the control priority of the behavior optimization unit 143 from the control priority of the trajectory stabilization unit 144 relative to the control priority of the behavior optimization unit 143 when the vehicle 101 is not in the predetermined state. Therefore, the priority adjustment unit 145 adjusts the control priority of the left steering command value θ separately based on the state quantity Q acquired from the state quantity processing unit 130. L1 and the right steering command value θ R1 The control priority of the behavior optimization unit 143 that performs feedback correction and performs feedback correction on the steering command value S1 to generate the left steering command value θ based on the same state quantity Q obtained from the state quantity processing unit 130. L1 and the right steering command value θ R1 The control priority of the trajectory stabilization unit 144 is set to achieve smooth control without causing vibration, etc.

[0032] The priority adjustment of the priority adjustment unit 145 is performed by, for example, changing the respective time constants of the behavior optimization unit 143 and the trajectory stabilization unit 144. Specifically, for example, the priority adjustment unit 145 can make the time constants different by adjusting at least one of the control period and the control gain of the behavior optimization unit 143 and the trajectory stabilization unit 144.

[0033] In the present embodiment, the predetermined state is assumed to be the limit state of the vehicle 101. When the priority adjustment unit 145 determines that the vehicle 101 is in the limit state based on the yaw rate, the vehicle speed, etc., the priority adjustment unit 145 shortens the control cycle of the behavior optimization unit 143 from the control cycle during normal driving of the optimization unit 143 to increase the control priority of the behavior optimization unit 143, and lengthens the control cycle of the trajectory stabilization unit 144 from the control cycle during normal driving of the trajectory stabilization unit 144 to reduce the control priority of the trajectory stabilization unit 144. Specifically, for example, the priority adjustment unit 145 changes the lengths of the control cycle of the behavior optimization unit 143 and the control cycle of the trajectory stabilization unit 144 so that the ratio of the control cycle of the trajectory stabilization unit 144 during normal driving to the control cycle of the behavior optimization unit 143 is reversed when the vehicle 101 is in the limit state. Alternatively, the priority adjustment unit 145 may set the control cycle of the behavior optimization unit 143 to be shorter than the control cycle during normal driving, and set the control cycle of the trajectory stabilization unit 144 to be longer than the control cycle during normal driving, so that the ratio of the control cycle of the trajectory stabilization unit 144 during normal driving to the control cycle of the behavior optimization unit 143 is not reversed even in the extreme state. It should be noted that instead of adjusting the control cycle, the control gain (e.g., at least one of a plurality of gains in proportional integral derivative (PID) control) may be adjusted.

[0034] In the present embodiment, the following two types of feedback control are independently performed: individual corrections of the right steering command value and the left steering command value indicating the right steering angle and the left steering angle based on the state quantity Q representing the behavior of the vehicle 101, such as the tire lateral force; and corrections of the steering command value S1 for determining the right steering command value and the left steering command value based on the state quantity Q. Thus, for example, the vehicle 101 can be steered with a so-called on-track feel, so that the vehicle 101 is steered in response to the steering operation of the steering member 103 according to the travel route while maintaining the behavior of the vehicle 101 with a small energy loss.

[0035] In addition, when the vehicle 101 is in a limit state, such as when the state of the road surface suddenly changes, by adjusting the control priority of the behavior optimization unit 143 and the trajectory stabilization unit 144, the vehicle 101 can be smoothly controlled without exceeding the limit state.

[0036] The present invention is not limited to the above embodiments. For example, other embodiments realized by combining the components described in the specification as desired or by removing one or more components may be used as embodiments of the present invention. Without departing from the scope of the present invention, i.e., the scope defined by the wording of the claims, modifications of the embodiments obtained by making various modifications that can be thought of by those skilled in the art are also included in the present invention.

[0037] For example, the vehicle 101 may have functions such as an assist mode that allows the steering operation of the vehicle 101 to be assisted via the steering member 103, and an automatic driving mode that allows automatic driving without using the steering member 103. Figure 3 As shown in , the vehicle 101 includes a driving sensor 162 that enables functions such as automatic driving and a driving control device 106 that controls or assists the driving of the vehicle 101 based on information from the driving sensor 162 .

[0038] The driving sensor 162 is a sensor that acquires information required for the automatic driving of the vehicle 101. The driving sensor 162 is not particularly limited, and may include various types of sensors. Examples of the driving sensor 162 include a camera that acquires information such as the positions of marks including white lines arranged on the road surface to generate a driving route, a sensor that acquires the position of the vehicle 101 in map information, and a radar for detecting obstacles in front of the vehicle 101.

[0039] The travel control device 106 controls the travel of the vehicle 101 based on information from the travel sensor 162 and the like. The travel control device 106 determines a target vehicle speed of the vehicle 101 and sets a vehicle speed command value V corresponding to the target vehicle speed. C Output to the drive control unit 135. The travel control device 106 also includes a route generation unit 161. The route generation unit 161 generates a route on which the vehicle 101 should travel based on the map information and the information from the travel sensor 162, and outputs the route as route information. The travel control device 106 outputs the steering command value S2 based on the current position of the vehicle 101, the route information generated by the route generation unit 161, and the like.

[0040] In the assist mode and the automatic driving mode, etc., the steering angle determination unit 141 of the control device 140 generates a left steering command value θ based on the steering command value S2 output from the travel control device 106. L2 and the right steering command value θ R2 Regardless of whether the vehicle 101 is in the assist mode or the automatic driving mode, the behavior optimization unit 143 corrects the left turning command value θ based on the state quantity Q. L2 and the right steering command value θ R2The route acquisition unit 142 obtains the vehicle speed command value V output from the travel control device 106 C The route information acquired from the route generation unit 161 is added and output. The trajectory stabilization unit 144 corrects the steering command value S2 based on the acquired route information.

[0041] exist Figure 3 In the example, there is no priority adjustment unit 145 that relatively adjusts the control priorities of the trajectory stabilization unit 144 and the behavior optimization unit 143. In this case, at least one of the trajectory stabilization unit 144 and the behavior optimization unit 143 may adjust the control priority based on the state quantity Q.

[0042] The technology of the present invention can be implemented through storage media such as systems, devices, methods, integrated circuits, computer programs, and computer-readable storage disks, and can be implemented through desired combinations of systems, devices, methods, integrated circuits, computer programs, and storage media.

[0043] For example, each processing unit included in the above embodiments is generally implemented by a large-scale integration (LSI) circuit as an integrated circuit. The processing units may be individually integrated into one chip, or may be integrated into one chip including some or all of the processing units.

[0044] The integrated circuit is not limited to the LSI circuit and can be implemented by a dedicated circuit or a general-purpose processor. A field programmable gate array (FPGA) that can be programmed after the LSI circuit is manufactured, or a reconfigurable processor that can reconfigure the connection and setting of the circuit unit inside the LSI circuit can be used.

[0045] In the above embodiments, each component may be composed of 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 such as a processor of a CPU, which reads and executes a software program stored in a storage medium such as a hard disk or a semiconductor memory.

[0046] Some or all of the above components can be made of a removable integrated circuit (IC) card or a single module. An IC card or module is a computer system consisting of a microprocessor, ROM, RAM, etc. An IC card or module may include the above-mentioned LSI circuit or system LSI circuit. An IC card or module implements the function of an IC card or module by a microprocessor that operates according to a computer program. IC cards and modules may have tamper resistance.

[0047] The technology related to the present invention is useful for a steering device in which a mechanism for steering each steering wheel is individually provided.

Claims

1. A control device, the control device being configured to independently control the steering angle of each of a left steering wheel arranged on the left side relative to a driving direction of a vehicle and a right steering wheel arranged on the right side relative to the driving direction of the vehicle, the control device being characterized by comprising a processor (140), the processor (140) being configured to execute: a route acquisition process for acquiring route information indicating a target route of the vehicle; a trajectory stabilization process for correcting a steering command value indicating a steering direction of the vehicle based on at least one state quantity among a plurality of state quantities indicating a behavior of the vehicle during travel so that the vehicle travels on the target route; a steering angle determination process for determining a left steering command value indicating the steering angle of the left steering wheel and a right steering command value indicating the steering angle of the right steering wheel based on the corrected steering command value indicating the steering direction of the vehicle; as well as Behavior optimization processing for correcting each of the left turn command value and the right turn command value based on at least one state quantity among the multiple state quantities indicating the behavior of the vehicle during driving, so that the behavior of the vehicle becomes a target behavior.

2. The control device according to claim 1, characterized in that: The processor (140) is configured to obtain the route information based on the steering command value.

3. The control device according to claim 1, characterized in that: The processor (140) is configured to obtain the route information from a travel control device, wherein the travel control device is configured to control or assist travel of the vehicle.

4. The control device according to any one of claims 1 to 3, characterized in that: The processor (140) is configured to perform a priority adjustment process when the processor (140) 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 driving, and the priority adjustment process changes the control priority of the trajectory stabilization process relative to the control priority of the behavior optimization process when the vehicle is not in the predetermined state.

5. A steering device, characterized in that: The invention comprises a control device according to any one of claims 1 to 3, a left steering mechanism (111) and a right steering mechanism (121), wherein the left steering mechanism (111) has a left actuator configured to steer the left steering wheel, and the right steering mechanism (121) has a right actuator configured to steer the right steering wheel.

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