Vehicle control device, vehicle control method, and vehicle control program

Abstract

A control device (80, 90) is configured to execute a towing information acquisition process and a towing time process. The towing information acquisition process is for acquiring information about whether a tractor is towing a trailer. The towing time process is a process in which, in a state in which the trailer is being towed, an operation target is operated in accordance with the values of operation input variables that are set to mitigate a yaw response of the vehicle to a turning instruction operation, as compared to a state in which the trailer is not being towed. The operation target is at least one among a steering system, a drive system, and a braking system, and the operation input variables are variables for determining input signals to the operation target.

Description

Vehicle control device, vehicle control method, and vehicle control program

[0001] The present disclosure relates to a vehicle control device, a vehicle control method, and a vehicle control program.

[0002] Japanese Patent Application Laid-Open No. 2003-144992 discloses a control device for dealing with the so-called sway phenomenon, in which the trailer of a coupled vehicle sways. This control device reduces the sway of the trailer by controlling the brakes when the sway phenomenon occurs.

[0003] US Patent Application Publication No. 2019 / 0001944

[0004] In articulated vehicles, it is more desirable to prevent the sway phenomenon from occurring in the first place than to reduce the sway of the trailer after the sway phenomenon has occurred.

[0005] One aspect of the present disclosure provides a vehicle control device. A control object of the control device is a vehicle equipped with a tractor. The control device is configured to execute a towing information acquisition process and a towing process. The towing information acquisition process is a process for acquiring information regarding whether the tractor is towing a trailer. The towing process is a process for operating an operation object in accordance with a value of an operation input variable that is set to slow down the yaw response of the vehicle to a turn instruction operation when the tractor is towing a trailer compared to when the tractor is not towing. The operation object is at least one of a steering system, a drive system, and a braking system, and the operation input variable is a variable that determines an input signal to the operation object.

[0006] Another aspect of the present disclosure provides a vehicle control method. A control object of this control method is a vehicle equipped with a tractor. The control method includes executing a towing information acquisition process and a towing process. The towing information acquisition process is a process for acquiring information regarding whether the tractor is towing a trailer. The towing process is a process for operating an operation object in accordance with a value of an operation input variable that is set to slow down the yaw response of the vehicle to a turn command operation when the tractor is towing a trailer compared to when the tractor is not towing. The operation object is at least one of a steering system, a drive system, and a braking system, and the operation input variable is a variable that determines an input signal to the operation object.

[0007] Another aspect of the present disclosure provides a vehicle control program. A control object of the control program is a vehicle equipped with a tractor. The control program includes instructions to cause a computer to execute a towing information acquisition process and a towing process. The towing information acquisition process is a process for acquiring information regarding whether the tractor is towing a trailer. The towing process is a process for operating an operation object in accordance with a value of an operation input variable that is set to slow down the yaw response of the vehicle to a turn command operation when the tractor is towing a trailer compared to when the tractor is not towing. The operation object is at least one of a steering system, a drive system, and a braking system, and the operation input variable is a variable that sets an input signal to the operation object.

[0008] FIG. 1 is a perspective view showing the configuration of an articulated vehicle according to a first embodiment. FIG. 2 is a diagram showing the configuration of a control system according to the same embodiment. FIG. 3 is a flowchart showing the procedure of processing executed by the control system according to the same embodiment. FIG. 4 is a flowchart showing the procedure of processing executed by a steering ECU according to the same embodiment. FIG. 5 is a flowchart showing the procedure of processing executed by a steering ECU according to the same embodiment. FIG. 6 is a flowchart showing the procedure of processing executed by a steering ECU according to a second embodiment. FIG. 7 is a flowchart showing the procedure of processing executed by an ADASECU according to a third embodiment. FIG. 8 is a diagram showing the configuration of a control system according to a fourth embodiment. FIG. 9 is a flowchart showing the procedure of processing executed by a steering ECU according to the same embodiment.

[0009] <First embodiment> A first embodiment will be described below with reference to the drawings. "Configuration of articulated vehicle" As shown in Figure 1, articulated vehicle 10 includes a tractor 20 and a trailer 30. Tractor 20 includes front wheels 22 and rear wheels 24. The front wheels 22 include two wheels, a right front wheel and a left front wheel, and rear wheels 24 include two wheels, a right rear wheel and a left rear wheel. Figure 1 also shows an example of a box-shaped trailer as trailer 30. Trailer 30 has wheels 32. The wheels 32 include two wheels, a right wheel and a left wheel.

[0010] The trailer 30 is connected to the rear of the tractor 20 via a ball joint 40. The ball joint 40 is a member that connects the trailer 30 to the tractor 20 so that the trailer 30 can rotate about an axis 42. The axis 42 extends along the height direction of the tractor 20.

[0011] Figure 2 shows some of the components provided in the tractor 20. As shown in Figure 2, a reaction force is applied to a steering wheel 52 in a steering system 50 provided in the combination vehicle 10 by a reaction motor 54. The reaction force is a torque with an opposite sign to the torque applied to the steering wheel 52 by the driver. The output voltage of an inverter 56 is applied to the terminals of the reaction motor 54.

[0012] The steering system 50 also includes a front wheel actuator Af and a rear wheel actuator Ar. In the front wheel actuator Af, power is applied to the front wheels 22 included in the steering system 50 from a front wheel steering motor 60. The output voltage of an inverter 62 is applied to terminals of the front wheel steering motor 60. In the rear wheel actuator Ar, power is applied to the rear wheels 24 included in the steering system 50 from a rear wheel steering motor 64. The output voltage of an inverter 66 is applied to terminals of the rear wheel steering motor 64.

[0013] The steering ECU 80 controls the torque of the reaction force motor 54 to control the control amount of the steering wheel 52, which is the control object. Here, the control amount is the reaction force. The steering ECU 80 also controls the torque of the front wheel steering motor 60 to control the control amount of the front wheels 22, which are the control object. Here, the control amount is the steering angle of the front wheels 22. The steering angle is the turning angle of the tires of the front wheels 22. The steering ECU 80 controls the torque of the rear wheel steering motor 64 to control the control amount of the rear wheels 24, which are the control object. Here, the control amount is the steering angle of the rear wheels 24.

[0014] To control the control amount, the steering ECU 80 refers to the steering torque Th detected by the torque sensor 85. The steering torque Th is the torque input to the steering wheel 52. To control the control amount, the steering ECU 80 also refers to the steering angle θh detected by the steering angle sensor 86. To control the control amount, the steering ECU 80 also refers to the rotation angle θmf of the front wheel steering motor 60 detected by the rotation angle sensor 87. To control the control amount, the steering ECU 80 also refers to the rotation angle θmr of the rear wheel steering motor 64 detected by the rotation angle sensor 88.

[0015] The steering ECU 80 includes a PU 82 and a storage device 84. The PU 82 is a software processing device including at least one of a CPU, a GPU, a TPU, etc. The storage device 84 stores a steering control program 84a.

[0016] The tractor 20 includes a drivetrain 100. The drivetrain 100 includes at least one of an internal combustion engine and a rotating electric machine as a vehicle thrust generating device. The tractor 20 includes a braking system 102. The braking system 102 includes at least one of a device that slows down the rotation of the wheels by frictional force and a device that slows down the rotation of the wheels by converting the power of the wheels into electrical energy. Note that the device that slows down the rotation of the wheels by converting into electrical energy may be shared with the rotating electric machine of the drivetrain.

[0017] The tractor 20 is equipped with an ADASECU 90. The ADASECU 90 operates the steering system 50, drive system 100, and braking system 102 to control the control variables of the combination vehicle 10, which is the control target. The control variables include vehicle speed, driving direction, etc. The drive system 100 may include a drive control device that controls an internal combustion engine and a rotating electric machine. In this case, "the ADASECU 90 operates the drive system 100" means that the ADASECU 90 outputs a command signal to the drive control device. The braking system 102 may include a braking control device that controls a device that slows down the rotation of the wheels. In this case, "the ADASECU 90 operates the braking system 102" means that the ADASECU 90 outputs a command signal to the braking control device. Furthermore, "the ADASECU 90 operates the steering system 50" means that the ADASECU 90 outputs a command signal to the steering ECU 80.

[0018] The ADASECU 90 refers to the vehicle speed V detected by the vehicle speed sensor 112. The ADASECU 90 also refers to the tractor yaw rate rt detected by the tractor-side yaw rate sensor 114 in order to control the control variable. The ADASECU 90 is capable of communicating with a user interface 116. The user interface 116 is an interface into which information from the driver is input. Here, the input of information from the driver includes input of the driver's intention. The input of the driver's intention includes input of whether automatic steering or manual steering is desired. The input of information from the driver also includes input of information about the trailer 30, etc.

[0019] The ADASECU 90 includes a PU 92 and a storage device 94. The PU 92 is a software processing device including at least one of a CPU, a GPU, a TPU, etc. An assist program 94a is stored in the storage device 94. The assist program 94a defines commands for executing automatic steering processing, etc.

[0020] "Processing for Understanding Trailer Status" Figure 3 shows the procedure for processing for understanding the status of the trailer. The processing shown in Figure 3 is executed while the ADASECU 90 and the steering ECU 80 communicate with each other. In detail, the processing on the left side of Figure 3 is realized by the PU 92 of the ADASECU 90 repeatedly executing an assist program 94a, for example, at a predetermined cycle. Also, the processing on the right side of Figure 3 is realized by the PU 82 of the steering ECU 80 repeatedly executing a steering control program 84a, for example, at a predetermined cycle. Note that, hereinafter, the step numbers of each processing are represented by numbers preceded by "S."

[0021] In the series of processes shown in Figure 3, the PU 92 first determines whether an input operation has been performed via the user interface 116 to input information regarding whether the trailer 30 is coupled to the tractor (S10). If the PU 92 determines that an input operation has been performed (S10: YES), the PU 92 determines whether information indicating that the trailer 30 is coupled has been input (S12). If the PU 92 determines that information indicating that the trailer 30 is coupled has been input (S12: YES), the PU 92 sets the traveling mode to the trailer towing mode (S14). On the other hand, if the PU 92 determines that information indicating that the trailer 30 is not coupled has been input (S12: NO), the PU 92 sets the traveling mode to the tractor-only mode (S16). After completing the processes of S14 and S16, the PU 92 outputs data indicating the traveling mode to the steering ECU 80 (S18).

[0022] The PU 92 also determines whether trailer information has been input via the user interface 116 (S20). The trailer information includes information on at least one of the following three items: the weight of the trailer 30, the position of the center of gravity of the trailer 30, and the length of the trailer 30. If the PU 92 determines that trailer information has been input (S20: YES), it outputs the trailer information to the steering ECU 80 (S22).

[0023] The PU 92 temporarily terminates the series of processes shown on the left side of Fig. 3 when it completes the process of S22 or when it makes a negative determination in the processes of S10 and S20. Meanwhile, the PU 82 of the steering ECU 80 determines whether it has received the data related to the driving mode output by the process of S18 or the data related to the trailer information output by the process of S22 (S30). If it determines that it has received the data (S30: YES), the PU 82 stores the received data in the storage device 84 (S32).

[0024] When the PU 82 completes the process of S32 or when a negative determination is made in the process of S30, the PU 82 temporarily terminates the series of processes shown on the right side of Fig. 3. Incidentally, the processes of S10 to S12 correspond to the towing information acquisition process, and the process of S20 corresponds to the trailer information acquisition process.

[0025] "Countermeasures against sway phenomenon" Fig. 4 shows a procedure for a process aimed at suppressing the occurrence of sway phenomenon. The series of processes shown in Fig. 4 is realized by the PU 82 repeatedly executing the steering control program 84a, for example, at a predetermined interval.

[0026] In the series of processes shown in Fig. 4, the PU 82 first determines whether the vehicle is in the manual steering mode (S40). If the PU 82 determines that the vehicle is in the manual steering mode (S40: YES), the PU 82 acquires the steering angle θh detected by the steering angle sensor 86 and the vehicle speed V detected by the vehicle speed sensor 112 (S42). The PU 82 calculates the target front wheel steering angle base value θfb* based on the steering angle θh (S44). The target front wheel steering angle base value θfb* is a base value for the target value of the steering angle of the front wheels 22. The PU 82 sets the target front wheel steering angle base value θfb* to a value that has a positive correlation with the steering angle θh.

[0027] Next, the PU 82 determines whether the vehicle is in trailer towing mode (S46). If the PU 82 determines that the vehicle is in trailer towing mode (S46: YES), it acquires the tractor yaw rate rt (S48). Next, the PU 82 selects map data that determines the coefficient Ka based on the trailer information (S50). The map data is data in which the vehicle speed V is an input variable and the coefficient Ka is an output variable.

[0028] The PU 52 inputs the tractor yaw rate rt to the following phase lead compensation filter, which is defined by a coefficient Ka, to obtain a correction amount Δθf as an output (S52): (1+Ka·s·T) / (1+s·T) Note that the above equation uses a Laplace operator s and a time constant T. The coefficient Ka in the above equation is calculated by the PU 82 using a map in accordance with the vehicle speed V.

[0029] Note that map data is a set of data consisting of discrete values ​​of input variables and values ​​of output variables corresponding to each of the input variable values. Furthermore, map calculation may be a process in which, when the value of an input variable matches one of the input variable values ​​in the map data, the value of the corresponding output variable in the map data is the calculation result. Furthermore, map calculation may be a process in which, when the value of an input variable does not match any of the input variable values ​​in the map data, the calculation result is a value obtained by interpolating the values ​​of multiple output variables included in the map data. Alternatively, map calculation may be a process in which, when the value of an input variable does not match any of the input variable values ​​in the map data, the calculation result is the value of the output variable in the map data that corresponds to the closest value of the multiple input variables included in the map data.

[0030] The PU 82 then subtracts the correction amount Δθf from the target front wheel steering angle base value θfb* and assigns the result to the target front wheel steering angle θf* (S54). On the other hand, if the PU 82 determines that the mode is the tractor-only mode (S46: NO), it assigns the target front wheel steering angle base value θfb* to the target front wheel steering angle θf* (S56).

[0031] When the processing of S54 and S56 is completed, the PU 82 acquires the front wheel steering angle θf (S58). The front wheel steering angle θf is calculated by the PU 82 based on the rotation angle θmf. The PU 82 calculates a feedback control manipulated variable in which the front wheel steering angle θf is the controlled variable and the target front wheel steering angle θf* is the controlled variable's target value, and substitutes this manipulated variable for the target front wheel torque Tf* (S60). The PU 82 then operates the inverter 62 by outputting an operation signal MSf corresponding to the target front wheel torque Tf* to the inverter 62 (S62). Here, if the target front wheel torque Tf* is an amount converted into the torque of the front wheel steering motor 60, the operation signal MSf becomes a signal for bringing the torque of the front wheel steering motor 60 closer to the target front wheel torque Tf*.

[0032] The PU 82 temporarily terminates the series of processes shown in FIG. 4 when it completes the process of S62 or when a negative determination is made in the process of S40. The processes of S46 to S54 and S58 to S62 correspond to the towing process. The process of S44 corresponds to the base target value setting process. The process of S48 corresponds to the yaw rate acquisition process. The process of S52 corresponds to the phase lead compensation process.

[0033] Figure 5 shows a processing procedure aimed at suppressing the occurrence of the sway phenomenon. The series of processing shown in Figure 5 is realized by the PU 82 repeatedly executing the steering control program 84a, for example, at a predetermined interval. For convenience, the same step numbers are assigned to processes in Figure 5 that correspond to those shown in Figure 4.

[0034] In the series of processes shown in Figure 5, the PU 82 first determines whether the automatic steering mode is in effect (S40a). If the PU 82 determines that the automatic steering mode is in effect (S40a: YES), the PU 82 acquires the target front wheel steering angle base value θfb* and the vehicle speed V (S42a). The target front wheel steering angle base value θfb* is a value set by the ADASECU 90. The PU 92 of the ADASECU 90 executes the assist program 94a to set a travel trajectory for the tractor 20, and then substitutes, for the target front wheel steering angle base value θfb*, a steering angle of the front wheels 22 that is appropriate for traveling the tractor 20 along the trajectory. Here, "appropriate for traveling the tractor 20 along the trajectory" means that the steering angle is appropriate when the travel mode is the tractor-only mode.

[0035] When the process of S42a is completed, the PU 82 executes the processes of S46 to S62. The processes of S46 to S54 and S58 to S62 correspond to the towing process. The process of S42a corresponds to the base target value setting process.

[0036] "Functions and Effects of the Present Embodiment" In manual steering mode, the PU 82 sets the target front wheel steering angle base value θfb* in accordance with the steering angle θh. In tractor-only mode, the PU 82 substitutes the target front wheel steering angle base value θfb* for the target front wheel steering angle θf*. On the other hand, in trailer towing mode, the PU 82 substitutes the value obtained by subtracting the correction amount Δθf from the target front wheel steering angle base value θfb* for the target front wheel steering angle θf*. The correction amount Δθf is the output value of a phase-lead compensation filter to which the tractor yaw rate rt is input, and therefore has a positive correlation with the tractor yaw rate rt. Therefore, the target front wheel steering angle θf* in trailer towing mode is set to a value that reduces the magnitude of the absolute value of the tractor yaw rate rt more than the target front wheel steering angle base value θfb*.

[0037] Generally, when the tractor 20 is towing the trailer 30, the absolute value of the yaw rate is more likely to increase even during the same turning operation compared to when the tractor is not towing the trailer 30. In other words, even if the steering wheel 52 is operated in the same way in trailer towing mode and tractor-only mode, the yaw response of the articulated vehicle 10 is more likely to be greater in trailer towing mode. This increase in the absolute value of the yaw rate can cause the sway phenomenon.

[0038] In contrast, the correction amount Δθf prevents the yaw response in the trailer towing mode from becoming larger when the steering wheel 52 is operated equally in the pair of modes.

[0039] In addition, in the automatic steering mode, if the curvature of the target travel path of the tractor 20 is the same in the pair of modes, the correction amount Δθf prevents the yaw response in the trailer towing mode from becoming larger.

[0040] According to the present embodiment described above, the following further actions and effects can be obtained: (1-1) The correction amount Δθf is calculated using a phase-lead compensation filter. Therefore, a correction amount that functions equivalent to the damping correction amount obtained by multiplying the time differential value of the tractor yaw rate rt by a gain can be obtained without using a differential operation.

[0041] (1-2) The likelihood of sway occurring varies depending on vehicle speed V. Therefore, PU 82 sets coefficient Ka according to vehicle speed V. This makes it possible to set target front-wheel steering angle θf* to a value appropriate for suppressing sway, while minimizing the difference between target front-wheel steering angle base value θfb* and target front-wheel steering angle θf*.

[0042] (1-3) The likelihood of sway occurring varies depending on the specifications and state of the trailer 30. Therefore, the PU 82 sets the coefficient Ka in accordance with the trailer information. This makes it possible to set the target front wheel steering angle θf* to a value appropriate for suppressing sway, while minimizing the difference between the target front wheel steering angle base value θfb* and the target front wheel steering angle θf*.

[0043] Second Embodiment A second embodiment will be described below with reference to the drawings, focusing on differences from the first embodiment.

[0044] Figure 6 shows the procedure of the process aimed at suppressing the occurrence of the sway phenomenon according to this embodiment. The series of processes shown in Figure 6 are realized by the PU 82 repeatedly executing the steering control program 84a, for example, at a predetermined interval. For convenience, the same step numbers are assigned to processes in Figure 6 that correspond to the processes shown in Figure 4.

[0045] 6, when the PU 82 completes the process of S42, it calculates the target front wheel steering angle θf* based on the steering angle θh (S44a). Next, the PU 82 determines whether the vehicle is in the trailer towing mode (S46). When the PU 82 determines that the vehicle is in the tractor-only mode (S46: NO), it executes the processes of S58 to S62.

[0046] On the other hand, if the PU 82 determines that the vehicle is in the trailer towing mode (YES at S46), it selects map data for setting a gain G (described later) in accordance with the trailer information (S70). The map data is data in which the vehicle speed V is an input variable and the gain G is an output variable.

[0047] The PU 82 multiplies the target front wheel steering angle θf* by the gain G and assigns the result to the target rear wheel steering angle θr* (S74). The target rear wheel steering angle θr* is a target value for the steering angle of the rear wheels 24 of the tractor 20. The gain G is calculated by the PU 82 using the map data described above. The gain G is set to a value that makes the sideslip angle β of the tractor 20 zero. The gain G may also be calculated by setting the sideslip angle β to zero in a vehicle model such as a two-wheel model.

[0048] The PU 82 calculates the front wheel steering angle θf and the rear wheel steering angle θr (S76). The rear wheel steering angle θr is calculated by the PU 82 using the rotation angle θmr. The PU 82 calculates the target front wheel torque Tf* and the target rear wheel torque Tr* (S78). Here, the PU 82 calculates the target front wheel torque Tf* by the processing described above. The PU 82 also calculates the manipulated variable of feedback control, in which the rear wheel steering angle θr is the controlled variable and the target rear wheel steering angle θr* is the target value of the controlled variable, and substitutes this manipulated variable for the target rear wheel torque Tr*.

[0049] Then, PU 82 outputs an operation signal MSf to inverter 62 and outputs an operation signal MSr to inverter 66 (S80). Here, if the target rear wheel torque Tr* is an amount converted into the torque of rear wheel steering motor 64, operation signal MSr becomes a signal for bringing the torque of rear wheel steering motor 64 closer to target rear wheel torque Tr*.

[0050] When the PU 82 completes the processes of S62 and S80 or when a negative determination is made in the process of S40, the PU 82 temporarily ends the series of processes shown in Fig. 6. Incidentally, the processes of S70 to S80 correspond to the towing process.

[0051] Incidentally, in the automatic steering mode, the PU 82 executes the process of FIG. 6 in which the processes of S42 and S44a are replaced with the process of S42a. "Actions and Effects of the Present Embodiment" The PU 82 sets the target rear wheel steering angle θr* in accordance with the target front wheel steering angle θf*. The target rear wheel steering angle θr* is the manipulated variable of open-loop control for controlling the sideslip angle β to zero. Therefore, in the manual steering mode, if the operation of the steering wheel 52 is the same whether the trailer towing mode is on or off, an increase in the yaw response in the trailer towing mode is suppressed. Furthermore, in the automatic steering mode, if the curvature of the target driving trajectory of the tractor 20 is the same whether the trailer towing mode is on or off, an increase in the yaw response in the trailer towing mode is suppressed.

[0052] Third Embodiment Hereinafter, a third embodiment will be described with reference to the drawings, focusing on differences from the first embodiment.

[0053] In this embodiment, in the trailer towing mode, the yaw response is slowed down by utilizing the drive system 100 and the braking system 102. Figure 7 shows the processing steps aimed at suppressing the occurrence of the sway phenomenon according to this embodiment. The series of processing steps shown in Figure 7 is realized by the PU 92 repeatedly executing the assist program 94a, for example, at a predetermined interval.

[0054] In the series of processes shown in Figure 7, the PU 92 first determines whether the vehicle is in trailer towing mode (S46). If the PU 92 determines that the vehicle is in trailer towing mode (S46: YES), the PU 92 selects map data for setting the threshold value ωhth in accordance with trailer information (S90). The map data is data in which the vehicle speed V is an input variable and the threshold value ωhth is an output variable. The PU 92 also acquires the vehicle speed V (S92).

[0055] The PU 92 then determines whether the absolute value of the steering speed ωh is equal to or greater than a threshold value ωhth (S94). This process determines whether a condition for executing a process to slow down the yaw response is met. The threshold value ωhth is set to the lower limit of the absolute value of the steering speed ωh at which a sway phenomenon is likely to occur. The PU 92 changes the threshold value ωhth in accordance with the vehicle speed V under the condition that the threshold value ωhth when the vehicle speed V is high is equal to or less than the threshold value ωhth when the vehicle speed V is low. Specifically, the threshold value ωhth is calculated using the map data selected by the PU 92 in the process of S90.

[0056] In the description "changing B according to A while satisfying the condition that when A is large, B is equal to or smaller than B when A is small," the case where A is large and the case where A is small refer to the relative relationship of magnitude when comparing the two. For example, "when A is large" corresponds to the case where "A is a first value," and "when A is small" corresponds to the case where "A is a second value smaller than the first value." This means that, depending on the settings of the first and second values, B when A is the first value may be smaller than B when A is the second value.

[0057] If the PU 92 determines that the difference is equal to or greater than the threshold value ωhth (YES in S94), it sets a difference in driving force between the inner wheel and the outer wheel (S96). This process is for reducing yaw response by applying a yaw moment in the opposite direction to the turning direction during turning. This process reduces the magnitude of the driving force of the outer wheel relative to the driving force of the inner wheel.

[0058] The PU 92 operates the drivetrain 100 and the braking system 102 to generate the driving force difference set by the processing of S96 (S98). For example, the PU 92 operates the braking system 102 to apply braking force to the outer wheels, and operates the drivetrain 100 to compensate for the output reduction caused by the braking force. However, as long as the drivetrain 100 can change the distribution of driving force to each wheel, the role of the drivetrain 100 is not limited to compensating for the total output reduction. For example, the PU 92 may execute a process to apply braking force to the outer wheels by the braking system 102, and also a process to reduce the driving force of the outer wheels relative to the driving force of the inner wheels by the drivetrain 100.

[0059] The process of S96 does not mean that the driving force of the outer wheels is made smaller than the driving force of the inner wheels, but rather that the process of S96 is made smaller than the value in the tractor-only mode, relative to the driving force of the inner wheels.

[0060] The PU 92 temporarily terminates the series of processes shown in FIG. 7 when it completes the process of S98 or when a negative determination is made in the processes of S46 and S94. "Actions and Effects of the Present Embodiment" When the absolute value of the steering speed ωh is equal to or greater than the threshold value ωhth in the trailer towing mode, the PU 92 operates the drive system 100 and the braking system 102 to superimpose a yaw moment in the direction opposite to the turning direction. In other words, the PU 92 controls the value obtained by subtracting the yaw moment in the trailer towing mode from the yaw moment in the tractor-only mode to be the opposite amount to the yaw moment in the tractor-only mode. This prevents the yaw response in the trailer towing mode from becoming too large when the turning instructions are the same in the trailer towing mode and the tractor-only mode.

[0061] Fourth Embodiment Hereinafter, a fourth embodiment will be described with reference to the drawings, focusing on differences from the first embodiment.

[0062] "Configuration of Articulated Vehicle" Figure 8 shows some of the members provided on the tractor 20. In Figure 8, members corresponding to those shown in Figure 2 are denoted by the same reference numerals for convenience.

[0063] As shown in Figure 8, the steering wheel 52 of the steering system 50 is capable of transmitting power to the front wheels 22 via a steering shaft 58. Torque from an assist motor 54a is applied to the steering shaft 58. The output voltage of an inverter 56a is applied to each terminal of the assist motor 54a. The inverter 56a is operated by a steering ECU 80. The steering ECU 80 refers to the rotation angle θm of the assist motor 54a detected by a rotation angle sensor 83a.

[0064] "Countermeasures against sway phenomenon" Fig. 9 shows a procedure for a process aimed at suppressing the occurrence of sway phenomenon. The series of processes shown in Fig. 9 is realized by the PU 82 repeatedly executing the steering control program 84a, for example, at a predetermined interval.

[0065] 9, the PU 82 first acquires the vehicle speed V, the steering angle θh, and the steering torque Th (S100). The steering angle θh is calculated based on the rotation angle θm by the PU 82. Next, the PU 82 acquires the previous value of the axial force Taf, which is calculated by the processing of S116 described later (S102).

[0066] Next, the PU 82 calculates the target steering torque base value Thb* in accordance with the previous value of the axial force Taf and the vehicle speed V (S104). For example, the PU 82 may change the target steering torque base value Thb* in accordance with the axial force Taf on the condition that the target steering torque base value Thb* when the axial force Taf is large is equal to or greater than the target steering torque base value Thb* when the axial force Taf is small. The PU 82 may also change the target steering torque base value Thb* in accordance with the vehicle speed V on the condition that the target steering torque base value Thb* when the vehicle speed V is large is equal to or greater than the target steering torque base value Thb* when the vehicle speed V is small.

[0067] Specifically, in a state where map data is stored in advance, the PU 82 may perform map calculations to determine the target steering torque base value Thb* in accordance with the axial force Taf and the vehicle speed V. Here, the map data is data in which the axial force Taf and the vehicle speed V are input variables and the target steering torque base value Thb* is an output variable.

[0068] Next, the PU 82 determines whether the vehicle is in the trailer towing mode (S106). If the PU 82 determines that the vehicle is in the trailer towing mode (S106: YES), the PU 82 selects map data that determines the gain Kt based on the trailer information (S108). This map data is data in which the vehicle speed V is an input variable and the gain Kt is an output variable.

[0069] Next, the PU 82 multiplies the target steering torque base value Thb* by a gain Kt and assigns the resulting value to the target steering torque Th* (S110). The gain Kt is a value greater than 1. The PU 82 changes the gain Kt in accordance with the vehicle speed V under the condition that the gain Kt when the vehicle speed V is high is equal to or greater than the gain Kt when the vehicle speed V is low. The gain Kt is calculated by the PU 82 using the map data. On the other hand, when the PU 82 determines that the tractor is in the tractor-only mode (S106: NO), it assigns the target steering torque base value Thb* to the target steering torque Th* (S112).

[0070] When the PU 82 completes the processing of S110 and S112, it calculates a manipulated variable Ts of feedback control in which the steering torque Th is the controlled variable and the target steering torque Th* is the target value of the controlled variable (S114). Here, the feedback control may be, for example, the sum of the output value of a proportional element, the input of which is the value obtained by subtracting the target steering torque Th* from the steering torque Th, and the output value of a derivative element, the input of which is the value obtained by the subtraction. Note that the manipulated variable Ts may include a manipulated variable of open-loop control in which the steering torque Th is the controlled variable.

[0071] Next, the PU 82 assigns the value obtained by adding the steering torque Th to the operation amount Ts to the axial force Taf (S116). Next, the PU 82 calculates the assist torque Ta by the assist motor 54a based on the axial force Taf (S118). Specifically, the PU 82 may calculate a target value for the steering angle θh from the axial force Taf based on a reference model, and then calculate the assist torque Ta as an operation amount for feedback control in which the steering angle θh is the control amount. The PU 82 then operates the inverter 56a by outputting an operation signal MSa based on the assist torque Ta to the inverter 56a (S120). Here, if the assist torque Ta is an amount converted into the torque of the front wheels 22, the operation signal MSa serves as a signal for adjusting the torque of the assist motor 54a to approach the assist torque Ta. Note that, when the target steering torque base value Thb* is the same in the tractor-only mode and the trailer towing mode, the absolute value of the assist torque Ta is smaller in the trailer towing mode.

[0072] When the PU 82 completes the processing of S120, it temporarily terminates the series of processing shown in FIG. 9 . Note that the processing of S108 to S120 corresponds to the towing processing. "Functions and Effects of the Present Embodiment" In the trailer towing mode, the PU 82 multiplies the target steering torque base value Thb* by the gain Kt and assigns this value to the target steering torque Th*. As a result, the PU 82 increases the torque required to turn the steering wheel 52 in the trailer towing mode. On the other hand, when the steering wheel 52 is rotated equally in the trailer towing mode and the tractor-only mode, the yaw response is higher in the trailer towing mode than in the tractor-only mode. Therefore, in this embodiment, when the steering torque Th is the same in the trailer towing mode and the tractor-only mode, the yaw response is prevented from being higher in the trailer towing mode than in the tractor-only mode.

[0073] <Other Embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0074] "Regarding the Towing Information Acquisition Process" The towing information acquisition process is not limited to the process of acquiring information input via the user interface 116. For example, a camera may be provided at the rear of the tractor 20, and the presence or absence of a trailer may be determined from an image captured by the camera.

[0075] 4 and 5, the PU 82 sets the coefficient Ka in accordance with the trailer information, but this is not limited to this. For example, the PU 82 may set the time constant T in accordance with the trailer information. Also, for example, the PU 82 may use a value obtained by multiplying the output value of the phase lead compensation process by a gain as the correction amount Δθf, and set the gain in accordance with the trailer information.

[0076] 6, the PU 82 sets a map for setting the gain G in accordance with the trailer information, but this is not limiting. For example, the PU 82 may set the second gain G2 in accordance with the trailer information, and may substitute a value obtained by multiplying the target front wheel steering angle θf* by the gain G and the gain G2 for the target rear wheel steering angle θr*. Also, for example, the PU 82 may perform map calculations for the gain G using map data in which the vehicle speed V and the trailer information are input variables and the gain G is an output variable.

[0077] 9, the PU 82 sets map data for determining the gain Kt in accordance with the trailer information, but this is not limiting. For example, the PU 82 may set the second gain Kt2 in accordance with the trailer information and substitute a value obtained by multiplying the target steering torque base value Thb* by the gain Kt and the gain Kt2 for the target steering torque Th*.

[0078] 4 and 5, the PU 82 sets the coefficient Ka according to the vehicle speed V, but this is not limitative. For example, the coefficient Ka may be a value that is set according to the trailer information and that is not dependent on the vehicle speed V.

[0079] The process in which the tractor yaw rate rt is input and the corrected target front wheel steering angle base value θfb* is output is not limited to the process using phase lead compensation. For example, the process may be a process in which the target front wheel steering angle base value θfb* is corrected by a value obtained by multiplying the time differential value of the tractor yaw rate rt by a proportional gain. In this case, the PU 82 may set the proportional gain based on at least one of the vehicle speed V and trailer information.

[0080] In the process of FIG. 6, the PU 82 sets the gain G in accordance with the vehicle speed V, but this is not limitative. For example, the gain G may be set in accordance with the trailer information and may be a value that is set independently of the vehicle speed V.

[0081] The process in which the yaw rate is input and the corrected value of the target front wheel steering angle base value θfb* is output is not limited to a process in which only the tractor yaw rate rt is input. For example, the process may be a process in which the yaw rate of the trailer 30 is input. Also, for example, the process may be a process in which both the tractor yaw rate rt and the yaw rate of the trailer 30 are input.

[0082] In the process shown in Fig. 9, the PU 82 sets the gain Kt in accordance with the vehicle speed V, but this is not limitative. For example, the gain Kt may be a value that is set in accordance with the trailer information and is not dependent on the vehicle speed V.

[0083] The process of operating the steering system in accordance with the value of an operation input variable that is determined so as to increase the force required for the driver to operate the steering wheel 52 is not limited to a process that uses feedback control of the steering torque Th. The process of operating the steering system in accordance with the value of the operation input variable may be a process that uses the following process. This process executes a process in which the steering torque Th is the input and the assist torque Ta, which is the operation amount of open-loop control, is the output, and operates the inverter 56a in accordance with the assist torque Ta. In this case, the process of operating the steering system in accordance with the value of an operation input variable that is determined so as to increase the force required for the driver to operate the steering wheel 52 may be a process that reduces or corrects the absolute value of the assist torque Ta.

[0084] The process of operating the steering system in accordance with the value of the operation input variable that is determined so as to increase the force required for the driver to operate the steering wheel 52 does not assume a configuration in which the steering wheel 52 and the steered wheels are connected. That is, for example, in the configuration illustrated in FIG. 2, the absolute value of the target steering torque Th* may be corrected to increase.

[0085] The towing process, which includes the process of setting the target rear wheel steering angle θr*, which is the value of the rear wheel steering angle variable, in accordance with the target front wheel steering angle θf*, which is the value of the front wheel steering angle variable, is not limited to the process shown in Fig. 6. For example, the process may include the process of setting the target steering angle of the trailer in addition to the target rear wheel steering angle θr* in accordance with the target front wheel steering angle θf*. In this case, however, the trailer 30 is provided with an actuator that steers the wheels 32.

[0086] The towing process including the process of reducing the relative magnitude of the driving force of the outer wheels of the tractor 20 to the driving force of the inner wheels of the tractor 20 compared to when the trailer 30 is not towed is not limited to the process described above. For example, the towing process including the process described above may be a process of manipulating only the driving torque of the drivetrain 100. This process can be achieved by changing the power distribution of the drivetrain 100 between the inner wheels and the outer wheels. Furthermore, the towing process including the process described above may be a process of manipulating only the braking force of the braking system 102.

[0087] The process of FIG. 4 or FIG. 5, the process of FIG. 6, the process of FIG. 7, and the process of FIG. 9 do not necessarily have to be executed exclusively. For example, any two of the four processes of FIG. 4, the process of FIG. 6, the process of FIG. 7, and the process of FIG. 9 may be executed. For example, any three of the four processes of FIG. 4, the process of FIG. 6, the process of FIG. 7, and the process of FIG. 9 may be executed. For example, all of the processes of FIG. 4, the process of FIG. 6, the process of FIG. 7, and the process of FIG. 9 may be executed. For example, any two of the three processes of FIG. 5, the process of FIG. 6, and the process of FIG. 7 may be executed. For example, all of the processes of FIG. 5, the process of FIG. 6, and the process of FIG. 7 may be executed. Note that in the above, the process of FIG. 4 or FIG. 5, the process of FIG. 6, the process of FIG. 7, and the process of FIG. 9 may each be replaced with a corresponding modified example.

[0088] 7, the PU 82 sets the threshold value ωhth in accordance with the vehicle speed V and the trailer information, but this is not limiting. For example, the PU 82 may set the threshold value ωhth in accordance with only the trailer information.

[0089] Regarding the Input Unit: The input unit through which the driver inputs his / her steering intention is not limited to the steering wheel 52. For example, it may be a joystick.

[0090] Regarding the Control Device: In the above embodiment, part of the processing executed by the steering ECU 80 may be executed by the ADASECU 90.

[0091] The ADASECU 90 and the steering ECU 80 may be integrated. The control device is not limited to one that executes software processing. For example, a dedicated hardware circuit, such as an ASIC, that executes at least part of the processing executed in the above embodiment may be included. That is, the control device may include a processing circuit having any of the following configurations (a) to (c): (a) A processing circuit that includes a processing device that executes all of the above processing in accordance with a program and a program storage device, such as a memory device, that stores the program. (b) A processing circuit that includes a processing device and program storage device that executes part of the above processing in accordance with a program, and a dedicated hardware circuit that executes the remaining processing. (c) A processing circuit that includes a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software execution devices that include a processing device and a program storage device. Also, there may be multiple dedicated hardware circuits.

[0092] Regarding the Control Body: For example, part of the above process may be executed by the driver's mobile terminal. That is, for example, the process executed by ADASECU 90 in FIG. 3 and the processes of S48 to S52 may be executed by the mobile terminal.

[0093] Others: For example, in the first, second and fourth embodiments, the tractor 20 does not have to include the rear wheel actuator Ar.

Claims

1. A control device for controlling a vehicle equipped with a tractor, It is configured to perform towing information acquisition processing and towing processing, The towing information acquisition process is a process for acquiring information regarding whether or not the tractor is in a state of towing a trailer. The towing process, when the trailer is being towed, is a process that operates the target of the operation according to the value of an operation input variable that is set to slow down the yaw response of the vehicle to the turning instruction operation compared to when the trailer is not being towed. The object of the operation is at least one of the three systems: the steering system, the drive system, and the braking system. The aforementioned operation input variable is a variable that defines the input signal to the object being operated on, It is configured to execute a trailer information acquisition process to acquire trailer information, The trailer information includes at least two of the following three pieces of information: the position of the trailer's center of gravity, the total weight of the trailer, and the length of the trailer. The towing process is a vehicle control device that operates the target of the operation according to the value of the operation input variable determined according to the trailer information.

2. The vehicle control device according to claim 1, wherein the towing process is a process in which, in a manual driving mode in which the tractor is steered in response to steering input by the driver, the control device for a vehicle operates according to a value of the operation input variable that is set to slow down the yaw response to the steering input.

3. It is configured to perform automatic steering operations. The vehicle control device according to claim 1, wherein the towing process is a process in which, when the automatic steering process is executed, the control device operates the target of operation according to the value of the operation input variable which is set to slow down the yaw response during turning with the same curvature as when the trailer is not being towed compared to when the trailer is not being towed.

4. The vehicle control device according to claim 1, wherein the towing process includes a process for correcting the value of the operation input variable.

5. It is configured to perform a base target value setting process to set a base target value, and a yaw rate acquisition process to obtain the yaw rate. The base target value is the base value for the target steering angle of the steering wheels. The vehicle control device according to claim 4, wherein the towing process includes a process in which the yaw rate is an input and a process in which the steering system is operated according to the operation input variable which is the corrected base target value.

6. The vehicle control device according to claim 5, wherein the towing process includes a phase lead compensation process in which the yaw rate is the input, and a process in which the steering system is operated according to the base target value corrected according to the output value of the phase lead compensation process.

7. The towing process includes, when the trailer is being towed, a process to operate the steering system according to the value of the operation input variable, which is determined to be greater than the force required by the driver to operate the input unit when the trailer is not being towed. The vehicle control device according to claim 4, wherein the input unit is an interface for inputting the driver's intention to steer.

8. The steering system is a system in which the input unit and the steering wheel are mechanically connected, and includes a motor that assists in steering the steering wheel. The vehicle control device according to claim 7, wherein the towing process includes, when the trailer is being towed, a process to control the absolute value of the motor's torque to a smaller value compared to when the trailer is not being towed.

9. The steering system includes a rear wheel actuator that steers the steering wheels of the tractor's rear wheels, The towing process includes setting the value of the rear wheel steering angle variable according to the value of the front wheel steering angle variable, and operating the rear wheel actuator according to the value of the rear wheel steering angle variable. The aforementioned front wheel steering angle variable is a variable that indicates a target value for the steering angle of the tractor's front wheels. The vehicle control device according to claim 4, wherein the rear wheel steering angle variable is the operation input variable and a variable indicating a target value for the rear wheel steering angle.

10. The vehicle control device according to claim 1, wherein the towing process includes a process of operating at least one of the braking system and the drive system to reduce the relative magnitude of the driving force of the outer wheels of the tractor to the driving force of the inner wheels of the tractor when the tractor is turning, compared to the state when the trailer is not being towed.

11. A control method for controlling a vehicle equipped with a tractor, This includes the execution of towing information acquisition processing and towing processing, The towing information acquisition process is a process for acquiring information regarding whether or not the tractor is in a state of towing a trailer. The towing process, when the trailer is being towed, is a process that operates the target of the operation according to the value of an operation input variable that is set to slow down the yaw response of the vehicle to the turning instruction operation compared to when the trailer is not being towed. The object of the operation is at least one of the three systems: the steering system, the drive system, and the braking system. A vehicle control method in which the operation input variable is a variable that determines the input signal to the object being operated.

12. A control program that controls a vehicle equipped with a tractor, It has a command to cause the computer to perform towing information acquisition processing and towing processing, The towing information acquisition process is a process for acquiring information regarding whether or not the tractor is in a state of towing a trailer. The towing process, when the trailer is being towed, is a process that operates the target of the operation according to the value of an operation input variable that is set to slow down the yaw response of the vehicle to the turning instruction operation compared to when the trailer is not being towed. The object of the operation is at least one of the three systems: the steering system, the drive system, and the braking system. The aforementioned operation input variable is a control program for a vehicle, which is a variable that defines the input signal to the object being operated on.