Jackknife restriction device, jackknife restriction method, and jackknife restriction program

Abstract

To provide a jackknife restriction device that can suppress a jackknife state.SOLUTION: A PU 52 predicts a future hitch angle β based on a hitch angle β and a turning angle θt. Then, the PU 52 calculates, based on the future hitch angle β, a turning angle in which jackknife occurs. PU 52 determines, based on the magnitude of a difference between the turning angle in which jackknife occurs and the maximum value of the turning angle θt, whether the risk of developing jackknife is high. When determining the risk is high, PU 52 operates a display device 82 and informs a user that the risk is high.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a jackknife suppression device, a jackknife suppression method, and a jackknife suppression program.

Background Art

[0002] For example, Patent Document 1 below describes a device that detects a jackknife state when the hitch angle exceeds the maximum steering angle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The above device is a device that identifies whether the current state is a jackknife state. Therefore, before falling into a jackknife state, measures to avoid becoming a jackknife state cannot be taken.

Means for Solving the Problems

[0005] Hereinafter, the means for solving the above problems and their effects will be described. 1. The jackknife suppression device is applied to a combined vehicle comprising a tractor and a trailer towed by the tractor, and is configured to perform acquisition processing, prediction processing, determination processing, and countermeasure processing, wherein the acquisition processing is the process of acquiring a hitch angle variable, which is a variable indicating the hitch angle which is the angle between the longitudinal direction of the tractor and the longitudinal direction of the trailer, and a steering angle variable, which is a variable indicating the steering angle of the tractor, the prediction processing is the process of calculating a predicted value of the hitch angle using the hitch angle variable and the steering angle variable as inputs, the determination processing is the process of determining whether or not there is a high risk of jackknife occurring using the predicted value and the steering angle variable as inputs, and the countermeasure processing is the process of operating predetermined hardware to suppress the occurrence of jackknife when it is determined that there is a high risk.

[0006] Based on the hitch angle and steering angle variables, the future trend of the hitch angle can be predicted. Furthermore, based on the future trend of the hitch angle, it is possible to determine whether there is a high risk of a jackknife occurring in the near future. Therefore, the above configuration performs both prediction and determination processes. If the risk of a jackknife occurring is high, countermeasures are executed to suppress the actual occurrence of a jackknife.

[0007] 2. The acquisition process is the jackknife suppression device described in paragraph 1 above, which includes a process to acquire the detected value of the sensor that detects the hitch angle as the hitch angle variable. In the above configuration, by using the detected hitch angle to predict the future hitch angle, the accuracy of the initial value of the hitch angle used in the prediction process can be improved with computationally intensive work.

[0008] 3. The prediction process is a jackknife suppression device as described in paragraph 2 above, which involves performing a process to calculate the future hitch angle using the detected value as input, and then performing a process to calculate an even further future hitch angle based on the calculated future hitch angle one or more times, thereby making the finally calculated future hitch angle the predicted value.

[0009] The relationship between the future hitch angle and the current hitch angle is nonlinear. Therefore, when predicting the future hitch angle from the current hitch angle in one step, the future hitch angle is determined by linear approximation. In contrast, as described above, by using the predicted hitch angle to predict the future even further ahead, the accuracy of the final predicted hitch angle can be improved compared to linear approximation.

[0010] 4. The jackknife suppression device according to any one of 1 to 3 above, wherein the acquisition process includes a process for acquiring the vehicle speed, and the prediction process includes a process for calculating the predicted value when the connected vehicle travels at the acquired vehicle speed for a predetermined period of time if the vehicle speed is equal to or greater than a reference value, and a process for calculating the predicted value when the connected vehicle travels at a vehicle speed greater than a predetermined zero for the predetermined period of time if the vehicle speed is less than the reference value.

[0011] When the vehicle speed is zero, the hitch angle does not change. Therefore, if the vehicle speed is excessively low, the change in the predicted hitch angle may be excessively small. As a result, when the vehicle is moving at very low speeds or is stopped, it becomes difficult to predict whether or not a jackknife will occur immediately after the vehicle accelerates. In the above configuration, when the vehicle speed is below a reference value, the hitch angle is predicted using a vehicle speed greater than zero, which is assumed in advance. This makes it possible to predict whether or not a jackknife will occur when the vehicle accelerates.

[0012] 5. The jackknife suppression device according to any one of 1 to 3 above, which includes a threshold setting process that takes the predicted value as input and sets a threshold value which is the value of the steering angle variable at which the jackknife occurs, and a risk determination process that determines the risk is high when the amount by which the maximum value that the steering angle variable can take exceeds the magnitude of the threshold is less than or equal to a specified value.

[0013] If the maximum steering angle exceeds the magnitude of the steering angle at which a jackknife occurs by a large margin, the hitch angle can be changed to either the left or right by changing the steering angle. This allows the jackknife to be avoided. On the other hand, if the above-mentioned excess amount becomes zero, the direction in which the steering angle can be changed is restricted. Therefore, the direction in which the hitch angle can be changed is also restricted. This may make it impossible to manipulate the steering angle to avoid a jackknife. For this reason, in the above configuration, the risk is determined according to the amount by which the maximum steering angle exceeds the magnitude of the steering angle at which a jackknife occurs.

[0014] 6. The prediction process includes a threshold setting process that takes the predicted value as input and sets a threshold value which is the value of the steering angle variable at which the jackknife occurs, and continues calculating the predicted value until the threshold value becomes a predetermined value, and the determination process includes a risk determination process that determines that the risk is high if the predicted time until the threshold value becomes a predetermined value is less than or equal to a predetermined time, and is the jackknife suppression device according to 3 above.

[0015] If the maximum steering angle significantly exceeds the amount of steering angle at which a jackknife occurs, the hitch angle can be changed to either the left or right by altering the steering angle. This allows the jackknife to be avoided. On the other hand, when the amount of the excess exceeds zero, the direction in which the steering angle can be changed is restricted. This also restricts the direction in which the hitch angle can be changed. Therefore, there is a risk that the steering angle will not be able to be manipulated to avoid a jackknife. For this reason, in the above configuration, the risk is quantified by the time it takes for the threshold to reach a predetermined value.

[0016] 7. A jackknife suppression device according to any one of 1 to 6 above, which performs an acceptance process to receive the user's opinion on the criteria for determining that the risk is high, and a setting process to set the criteria according to the opinion received by the acceptance process.

[0017] Setting strict criteria for determining a high risk of jackknife may restrict driving even in situations where a driver with sufficient skill could avoid jackknife. On the other hand, loosening the criteria may lead to a delayed assessment of the high risk for less skilled drivers, potentially resulting in a jackknife. Therefore, the above configuration incorporates user input regarding the criteria. This allows users to set the criteria according to their own driving skills.

[0018] 8. The countermeasure is a jackknife suppression device according to any one of 1 to 7 above, which includes a notification process that notifies the user of the connected vehicle that there is a high risk. In the above configuration, by informing the user that there is a high risk, the user can recognize that there is a high risk of jackknife. Therefore, in the above configuration, the user can be encouraged to drive in a way that does not cause jackknife.

[0019] 9. The jackknife suppression device is one of the above 1 to 8, which performs an automatic steering process to automatically control the steering angle of the trailer, and the countermeasure process includes a gain increase process to increase the gain of the automatic steering process.

[0020] In the above configuration, if the risk of a jackknife is high, gain increase processing is executed. This improves the responsiveness of the control, thereby suppressing the occurrence of a jackknife.

[0021] 10. The jackknife suppression device according to any one of 1 to 9 above, which performs an automatic steering process to automatically control the steering angle of the trailer, and the countermeasure process includes a trajectory changing process that changes the travel trajectory of the coupled vehicle as a result of the automatic steering process.

[0022] In the above configuration, when the risk of jackknifing is high, the driving trajectory is changed by the automatic steering process. As a result, it is possible to change to a driving trajectory where jackknifing is less likely to occur. Therefore, according to the above configuration, it is possible to suppress the occurrence of jackknifing.

[0023] 11. The countermeasure process includes a process of restricting the vehicle speed to the lower side, and it is the jackknife suppression device according to any one of the above 1 to 10. When the vehicle speed is low, it is easier to secure a time margin for changing to a steering angle at which jackknifing does not occur compared to when the vehicle speed is high. Therefore, in the above configuration, when the risk of jackknifing is high, the vehicle speed is restricted to the lower side. This facilitates the operation of the steering angle necessary to avoid jackknifing.

[0024] 12. A jackknife suppression method having steps of executing each process in the jackknife suppression device according to any one of the above 1 to 11. 13. A jackknife suppression program for causing a computer to execute each process in the jackknife suppression device according to any one of the above 1 to 11.

Brief Explanation of Drawings

[0025] [Figure 1] It is a perspective view showing the configuration of a articulated vehicle according to the first embodiment. [Figure 2] It is a block diagram showing the configuration of the control system according to the same embodiment. [Figure 3] It is a flowchart showing the procedure of the process executed by the control device according to the same embodiment. [Figure 4] It is a diagram showing a model of the articulated vehicle according to the same embodiment. [Figure 5] It is a diagram for explaining the magnitude of the risk according to the same embodiment. [Figure 6] (a) and (b) are diagrams for explaining the operation of the same embodiment. [Figure 7] It is a flowchart showing the procedure of the process executed by the control device according to the second embodiment. [Figure 8] This is a flowchart showing the procedure of processing performed by the control device according to the third embodiment. [Figure 9] This is a flowchart showing the procedure of processing performed by the control device according to the fourth embodiment. [Modes for carrying out the invention]

[0026] <First Embodiment> The first embodiment will be described below with reference to the drawings. "Composition of coupled vehicles" As shown in Figure 1, the articulated vehicle 10 has a tractor 20 and a trailer 30. In Figure 1, the tractor 20 is exemplified as a pickup truck, a type of light commercial vehicle. The tractor 20 has front wheels 22 and rear wheels 24. The front wheels 22 include two wheels, the right front wheel and the left front wheel, and the rear wheels 24 include two wheels, the right rear wheel and the left rear wheel. Also in Figure 1, the trailer 30 is exemplified as a box-shaped trailer. The trailer 30 has wheels 32. The wheels 32 include two wheels, the right wheel and the left wheel.

[0027] The trailer 30 is connected to the rear of the tractor 20 via a ball joint 40. The ball joint 40 is a component that connects the trailer 30 to the tractor 20 so that it can rotate around an axle 42. The axle 42 extends along the height direction of the tractor 20.

[0028] Figure 2 shows some of the components of the tractor 20. As shown in Figure 2, the tractor 20 is equipped with a control device 50. The control device 50 operates the steering system 60, the drive system 62, and the braking system 64 to control the control quantities of the coupled vehicle 10, which is the object of control. The control quantities include vehicle speed, direction of travel, and hitch angle. The hitch angle is the angle between the longitudinal direction of the tractor 20 and the longitudinal direction of the trailer 30.

[0029] The steering system 60 includes a steering actuator that steers the steering wheels. The steering wheels are, for example, the front wheels 22 shown in Figure 1. The steering system 60 may also include a steering control device that operates the steering actuator. In that case, "the control device 50 operates the steering system 60" means that the control device 50 outputs a command signal to the steering control device.

[0030] The drive system 62 includes at least one of two components, an internal combustion engine and a rotating electric machine, which serve as thrust generating devices for the vehicle. The drive system 62 may also include a drive control device that controls the internal combustion engine and the rotating electric machine. In this case, "the control device 50 operates the drive system 62" means that the control device 50 outputs a command signal to the drive control device.

[0031] The braking system 64 includes at least one of two devices: one that slows down the rotation of the wheels by frictional force, and another that slows down the rotation of the wheels by converting the power of the wheels into electrical energy. The device that slows down the rotation of the wheels by converting power into electrical energy may be shared with the rotating electric machine of the drive system. The braking system 64 may also include a braking control device that controls the device that slows down the rotation of the wheels. In that case, "the control device 50 operates the braking system 62" means that the control device 50 outputs a command signal to the braking control device.

[0032] The control device 50 refers to the steering angle θt of the steering wheel detected by the steering angle sensor 70 and the yaw rate yr detected by the yaw rate sensor 72 in order to control the control amount. The steering angle θt is a value in which the sign of either right turn or left turn is positive and the sign of the other is negative. The steering angle θt is the steering angle of the tire. For example, if the steering system 60 is equipped with a rack and pinion mechanism, the steering angle sensor 70 may be a sensor that detects the pinion angle. However, in that case, the control device 50 performs a process to convert the pinion angle to the steering angle of the tire. In the following explanation, for convenience of explanation, even if the steering angle of the tire is obtained by the above conversion process, it will be considered as the value detected by the steering angle sensor 70.

[0033] The control device 50 also refers to the hitch angle β detected by the hitch angle sensor 74 and the wheel speeds ωw1 to ωw4 detected by the wheel speed sensor 76. The hitch angle β can have both positive and negative signs depending on the angle between the direction of movement of the tractor 20 from rear to front and the direction of movement of the trailer 30 from rear to front. For example, the sign of the hitch angle β may be positive when the direction of movement of the trailer 30 from rear to front is shifted by less than 180° counterclockwise relative to the direction of movement of the tractor 20 from rear to front. Wheel speeds ωw1 and ωw2 are the rotational speed of the right front wheel 22 and the left front wheel 22, respectively. Wheel speeds ωw3 and ωw4 are the rotational speed of the right rear wheel 24 and the left rear wheel 24, respectively. The control device 50 sets the control of the control variables according to the operating state of the user interface 80. The user interface 80 is for communicating the user's intentions to the control device 50, such as selecting either automatic driving or manual driving.

[0034] The control device 50 includes a PU 52 and a storage device 54. The PU 52 is a software processing unit comprising at least one of a CPU, GPU, and TPU. The storage device 54 stores a jackknife suppression program 54a and a reverse assist program 54b.

[0035] The jackknife suppression program 54a is a program that specifies a command to the PU 52 to perform a process to suppress jackknife. The reverse assist program 54b is a program that specifies a command to the PU 52 to perform reverse control by automatic driving of the coupled vehicle 10.

[0036] "A process to suppress jackknife operation" Figure 3 shows the procedure for suppressing jackknife behavior. The procedure shown in Figure 3 is achieved by the PU 52 repeatedly executing the jackknife suppression program 54a, for example, at a predetermined interval. In the following, the step number of each procedure is represented by a number preceded by "S".

[0037] In the series of processes shown in Figure 3, PU52 first determines whether or not it is in manual reverse mode (S10). In other words, it determines whether or not it is in a mode in which the user drives the coupled vehicle 10 in reverse without the reverse assist program 54b being executed.

[0038] If PU52 determines that it is in manual reverse mode (S10: YES), it obtains the steering angle θt and hitch angle β (S12). Then, PU52 removes high-frequency components by applying a low-pass filter to the steering angle θt and hitch angle β (S14). Next, PU52 obtains the rear wheel speed VB1 of the coupled vehicle 10 (S16). Here, the rear wheel speed VB1 is the speed of the rear wheel B1 in the model shown in Figure 4, which will be described later. The sign of the rear wheel speed VB1 is positive when the tractor 20 is moving forward and negative when it is moving in reverse. The rear wheel speed VB1 is calculated by PU52 based on at least one of the wheel speeds ωw1 to ωw4. The rear wheel speed VB1 may be, for example, the average value of the wheel speeds ωw3 and ωw4 converted to a translational speed.

[0039] Next, PU52 determines whether the absolute value of the rear wheel speed VB1 is greater than or equal to the reference value VB1b (S18). If PU52 determines that the absolute value is less than the reference value VB1b (S18: NO), it assigns the reference value VB1b to the rear wheel speed VB1 variable used in the prediction process described later (S20). If PU52 completes the process in S20, or if it makes a positive determination in the process in S18, it assigns the hitch angle β obtained in the process in S12 to the predicted hitch angle βe (S22). This process determines the initial value for the hitch angle β prediction process described later.

[0040] Next, PU52 determines whether the variable i is less than or equal to a specified number N (S24). The variable i is a variable that counts the number of times the process described in S26 is executed. The initial value of the variable i is zero. On the other hand, the specified number N is a natural number greater than or equal to "1". If PU52 determines that the variable i is less than or equal to the specified number N (S24: YES), it calculates the predicted hitch angle βe as the future hitch angle for each unit of time (S26). This will be explained below.

[0041] Figure 4 shows the model used to predict the hitch angle β. In the model shown in Figure 4, the pair of front wheels 22 of the tractor 20 are designated as front wheels C0, and the pair of rear wheels 24 of the tractor 20 are designated as rear wheels B1. In other words, a two-wheel model is used for the tractor 20. The pair of wheels 32 of the trailer 30 are designated as wheels B2. The hitch angle β is the angle between the line defined by the front wheels C0 and the hitch point C1 and the line defined by the hitch point C1 and wheels B2. The hitch point C1 corresponds to the axle 42 portion in Figure 1. The front wheel speed VC0, which is the speed of the front wheels C0, is defined as a vector moving in the direction of the steering angle α. The hitch angle β is modeled as the angle between the direction in which the front wheels C0 move and the line defined by the front wheels C0 and the hitch point C1. The direction of the rear wheel speed VB1 is parallel to the line defined by the front wheels C0 and the hitch point C1. Furthermore, the angle between the direction of the rear wheel speed VB1 and the x-direction in Figure 4 is angle θ1. Also, the angle between the line connecting wheel B2 and hitch point C1 and the x-direction is angle θ2. In addition, the distance l1 between the front wheel C0 and rear wheel B1, the distance h1 between rear wheel B1 and hitch point C1, and the distance l2 between hitch point C1 and wheel B2 are defined.

[0042] In the model shown in Figure 4, the time derivative dβ / dt of the hitch angle β is expressed by the following equation (c1). dβ / dt =-(VB1 / l2)·sinβ -{VB1 / (l1·l2)}·(l2+h1·cosβ)·tanα …(c1) In the above equation, by expressing the time derivative dβ / dt as the difference per unit time, the following updated equation for the predicted hitch angle βe is obtained. In the S26 process, PU52 calculates the predicted hitch angle βe using the following updated equation.

[0043] βe ← βe - (VB1 / 12)·sinβe -{VB1 / (l1·l2)}·(l2+h1·cosβe)·tanα Returning to Figure 3, PU52 executes the process in S26, incrementing the variable i by "1" (S28). Then PU52 returns to the process in S24.

[0044] On the other hand, if PU52 determines that the variable i is greater than a specified number N (S24: NO), it calculates the threshold αth, which is the minimum steering angle at which a jackknife occurs (S30). Specifically, PU52 substitutes "arctan{-l1·sinβe / (l2+h1·cosβe)}" for the threshold αth. This process sets the threshold αth to the steering angle at which the time derivative dβ / dt in the above equation (c1) is set to zero. In other words, when a jackknife occurs, the hitch angle β increases regardless of whether the steering is left or right. Therefore, the steering angle α that has the lower limit of magnitude at which a jackknife occurs is the steering angle at which the time derivative dβ / dt in the above equation (c1) is set to zero.

[0045] As shown in Figure 5, when the hitch angle β is "0°", the trailer 30 turns to the right if the steering angle θt is a value on the right-turn side, and turns to the left if the steering angle θt is a value on the left-turn side. On the other hand, when the hitch angle β is "50°", the trailer 30 turns to the left regardless of whether the steering angle θt is a value on the right-turn side or the left-turn side. In other words, it is not possible to control the magnitude of the hitch angle β by manipulating the steering angle θt.

[0046] Returning to Figure 3, PU52 determines whether the amount Δ by which the maximum steering angle θtmax exceeds the absolute value of the threshold αth is less than or equal to a specified value Δth (S32). The maximum steering angle θtmax is the maximum value of the steering angle θt. Here, the specified value Δth is set as the lower limit for determining whether a jackknife is likely to occur.

[0047] Figure 5 shows that when the hitch angle β is "50°", the hitch angular velocity, which is the velocity at the hitch angle β, is greater than or equal to zero. Therefore, the magnitude of the steering angle θt at which the hitch angular velocity becomes zero coincides with the maximum steering angle θtmax. Consequently, when the hitch angle β is "50°", it is no longer possible to avoid a jackknife. In contrast, for example, when the hitch angle β is "0°", the steering angle at which the hitch angular velocity becomes zero is "0°". Therefore, there is a large difference between the absolute value of the threshold αth and the maximum steering angle θtmax. Consequently, there is a margin before a jackknife occurs. Therefore, the smaller the amount Δ by which the maximum steering angle θtmax exceeds the absolute value of the threshold αth, the greater the risk of a jackknife occurring. Thus, the amount Δ is a variable that indicates the degree of risk of a jackknife occurring.

[0048] Returning to Figure 3, if PU52 determines that the value is less than or equal to a specified value Δth (S32: YES), it performs a warning process by operating the display device 82 (S34). Specifically, PU52 flashes an image of a predetermined object displayed on the display device 82. Here, PU52 changes the flashing period of the image according to the magnitude of the excess amount Δ. Specifically, PU52 ensures that the period when the excess amount Δ is large is greater than or equal to the period when the excess amount Δ is small. This process can be achieved, for example, by having the storage device 54 store map data and PU52 perform a map calculation on the period based on the excess amount Δ. Here, map data is data where the excess amount Δ is the input variable and the period is the output variable. Map data is a set of data consisting of discrete values ​​of the input variables and values ​​of the output variables corresponding to each of the input variable values. Furthermore, the map calculation can be performed by taking the value of the corresponding output variable of the map data as the calculation result when the value of the input variable matches any of the input variable values ​​of the map data. Furthermore, if the value of an input variable does not match any of the values ​​of the input variables in the map data, the map operation may be performed by interpolating the values ​​of multiple output variables included in the map data to obtain the result of the operation. Alternatively, if the value of an input variable does not match any of the values ​​of the input variables in the map data, the map operation may be performed by performing the operation on the value of the output variable in the map data that corresponds to the closest value among the multiple output variables included in the map data.

[0049] Furthermore, the PU 52 limits the vehicle speed of the coupled vehicle 10 to a lower limit by operating the drive system 62 and the braking system 64 (S36). In other words, the PU 52 limits the driving force generated by the drive system 62 or applies braking force so that the coupled vehicle 10 does not exceed a predetermined upper speed limit due to the user's accelerator operation, etc.

[0050] Furthermore, when PU52 completes the process in S36, or when it makes a negative determination in the process in S10, it temporarily terminates the series of processes shown in Figure 3. Now, the operation and effects of this embodiment will be described.

[0051] Figure 6 illustrates the displacement of the hitch angle β. Specifically, Figure 6(a) shows the case where the steering angle θt is turned to the right and the hitch angle β is displaced in a direction that decreases in magnitude. In this case, the risk of jackknife is small.

[0052] In contrast, Figure 6(b) shows a situation where the steering angle θt is turned to the leftward side and the hitch angle β is displaced in a direction that increases in magnitude. In this case, the risk of jackknife is high. Therefore, PU52 notifies the user that there is a high possibility of jackknife occurring.

[0053] Specifically, PU52 determines that there is a high probability of a jackknife occurring when the amount Δ, which is the amount by which the maximum steering angle θtmax exceeds the absolute value of the threshold αth, is small. Here, the threshold αth is calculated according to the predicted hitch angle βe. In contrast, Figure 6 also shows the threshold αth0 calculated using the current hitch angle β. As shown in Figure 6(b), the time t1 at which the threshold αth reaches the maximum steering angle θtmax is earlier than the time t2 at which the threshold αth0 reaches the maximum steering angle θtmax. Therefore, according to this embodiment, the risk of a jackknife occurring can be detected and warned about early.

[0054] According to the embodiment described above, the following effects and benefits can be obtained. (1-1) PU52 first calculates a predicted hitch angle βe for each unit of time, taking the hitch angle β as input. Then, it performs a process of calculating a further predicted hitch angle βe for each unit of time based on this result one or more times. Finally, PU52 calculates a threshold αth using the calculated predicted hitch angle βe. This makes it possible to improve the accuracy of the predicted hitch angle βe used to calculate the threshold αth compared to linear approximation.

[0055] (1-2) When the rear wheel speed VB1 is zero, according to equation (c1) above, the hitch angle β does not change. Therefore, if the rear wheel speed VB1 is excessively small, the change in the predicted hitch angle βe may become excessively small. For example, when the coupled vehicle 10 starts moving from a standstill, it becomes difficult to predict whether or not a jackknife will occur immediately afterward. Therefore, when the rear wheel speed VB1 is smaller than the reference value VB1b, PU52 substitutes the reference value VB1b into the rear wheel speed VB1 which is the input for the calculation of the predicted hitch angle βe. This makes it possible to predict whether or not a jackknife will occur when the coupled vehicle 10 accelerates from a very low speed.

[0056] (1-3) When the maximum steering angle θtmax exceeds the steering angle θt that causes a jackknife by a large amount, the hitch angle β can be changed to either the left or right by changing the steering angle θt. This makes it possible to avoid a jackknife. On the other hand, when the amount by which the maximum steering angle θtmax exceeds the steering angle θt that causes a jackknife is zero, the direction in which the steering angle θt can be changed is restricted. This also restricts the direction in which the hitch angle can be changed. Therefore, there is a risk that the steering angle will not be able to be manipulated to avoid a jackknife. Accordingly, PU52 determined that the risk was high when the amount by which the maximum steering angle θtmax exceeds the absolute value of the threshold αth was less than or equal to a predetermined value Δth. This makes it possible to determine whether or not there is a high risk of a jackknife occurring.

[0057] (1-4) PU52 notified the user if there was a high risk of jackknife occurring. This allowed the user to recognize the high risk of jackknife occurring, and thus encouraged the user to drive in a way that would prevent jackknife.

[0058] <Second Embodiment> The second embodiment will be described below, focusing on the differences from the first embodiment, with reference to the drawings.

[0059] In the first embodiment described above, a criterion for determining the likelihood of a jackknife occurring was predetermined. In contrast, in this embodiment, the user is allowed to change the criterion. Figure 7 shows the procedure for processing changes to the criteria. The process shown in Figure 7 is achieved by PU52 repeatedly executing the jackknife suppression program 54a, for example, at a predetermined interval.

[0060] In the series of processes shown in Figure 7, the PU52 first determines whether there is an input operation to the user interface 80 indicating an intention to change the above criteria (S40). If the PU52 determines that there is an input operation (S40: YES), it accepts the input to change the criteria (S42). This process can be carried out as follows. First, the PU52 displays several options on the display device 82 regarding how to change the criteria. Specifically, for example, with respect to the default criteria, it presents options that determine danger earlier and options that do not determine danger as much as possible, depending on the user's perception of their own driving skills. Here, for example, there may be multiple options that determine danger earlier. Also, for example, there may be multiple options that do not determine danger as much as possible.

[0061] Then, PU52 changes the criteria according to the selected option (S44). Here, PU52 sets a default value Δth according to the anxiety about driving skills. Here, the default value Δth when anxiety about driving skills is high is set to be greater than or equal to the default value Δth when anxiety about driving skills is low. Furthermore, if the excess amount Δ is less than or equal to the default value Δth, PU52 sets the flashing period according to the anxiety about driving skills, even if the excess amount Δ is the same. Here, the period when anxiety about driving skills is high is set to be less than or equal to the period when anxiety about driving skills is low.

[0062] Furthermore, PU52 terminates the series of processes shown in Figure 7 when it completes the process in S44 or when it makes a negative determination in the process in S40. According to the embodiment described above, the following actions and effects can be obtained.

[0063] (2-1) If the criteria for determining a high risk of jackknife are set too strictly, it may restrict driving even in situations where it is possible to drive without jackknife depending on the driver's skill. On the other hand, if the criteria are too lenient, it may delay the determination of a high risk when a user with low driving skills is driving, potentially leading to a jackknife. Therefore, PU52 accepts the user's opinion regarding the criteria. This allows users to set the criteria according to their own driving skills.

[0064] (2-2) PU52 sets the flashing period according to the degree of anxiety regarding driving skills, even if the excess amount Δ is the same. This allows the flashing period to be appropriately reduced as the excess amount Δ becomes smaller than the specified value Δth, with the specified value Δth being used as a criterion to notify that the risk is high.

[0065] <Third Embodiment> The third embodiment will be described below, focusing on the differences from the first embodiment, with reference to the drawings.

[0066] In the first embodiment described above, the risk of a jackknife occurring was quantified according to the amount Δ by which the maximum steering angle θtmax exceeds the absolute value of the threshold αth. In contrast, in this embodiment, the risk is quantified according to the time required for the absolute value of the threshold αth, which is the steering angle θt at which a jackknife is determined to occur, to reach the maximum steering angle θtmax.

[0067] Figure 8 shows the procedure for suppressing jackknife behavior according to this embodiment. The process shown in Figure 8 is achieved by the PU 52 repeatedly executing the jackknife suppression program 54a, for example, at a predetermined cycle. In Figure 8, for convenience, the same step numbers are assigned to the processes corresponding to those shown in Figure 3, and their explanations are omitted.

[0068] In the series of processes shown in Figure 8, if PU52 completes the process in S22, it sequentially executes processes S26 and S30. Then, PU52 increments the variable i, which indicates the number of times processes S26 and S30 have been executed, by "1" (S50). The initial value of variable i is "0". Then, PU52 determines whether the absolute value of the threshold αth is greater than or equal to the maximum steering angle θtmax (S52). If PU52 determines that it is less than the maximum steering angle θtmax (S52: NO), it returns to the process in S26. On the other hand, if PU52 determines that it is greater than or equal to the maximum steering angle θtmax (S52: YES), it determines whether variable i is greater than or equal to the threshold ith (S54). The threshold ith is set according to the lower limit value at which the risk of jackknife occurring is judged to be high. Then, if PU52 determines that it is greater than or equal to the threshold ith (S54: YES), it executes processes S34 and S36.

[0069] In addition, PU52 changes the blinking period according to the value of variable i during processing S34. Here, PU52 sets the blinking period when the value of variable i is small to be less than or equal to the blinking period when the value of variable i is large.

[0070] Furthermore, when PU52 determines that the result is negative in processing S10 and S54, or when processing S36 is completed, it temporarily terminates the series of processes shown in Figure 8. <Fourth Embodiment> The fourth embodiment will be described below, focusing on the differences from the first embodiment, with reference to the drawings.

[0071] In this embodiment, when performing reverse control by automatic driving of the coupled vehicle 10, a process is executed to suppress the occurrence of a jackknife. Figure 9 shows the procedure for suppressing jackknife behavior according to this embodiment. The procedure shown in Figure 9 is achieved by the PU 52 repeatedly executing the jackknife suppression program 54a, for example, at a predetermined cycle. In Figure 9, for convenience, the same step numbers are assigned to the procedures corresponding to those shown in Figure 3, and their explanations are omitted.

[0072] In the series of processes shown in Figure 9, PU52 first determines whether or not it is in assist mode (S10a). If PU52 determines that it is in assist mode (S10a: YES), it executes processes S12 to S32.

[0073] If PU52 determines that the value is less than or equal to a specified value Δth (S32: YES), it executes a process to reduce the risk of jackknife (S34a). Here, PU52 changes the trajectory of the coupled vehicle 10 so that its curvature is smaller. This setting is intended to facilitate control of the steering angle θt so that jackknife does not occur. However, if PU52 determines that it is difficult to change the curvature, it increases the control gain. Here, the control gain may be a gain for feedback control of the steering angle θt to a target steering angle. Alternatively, the control gain may be a gain for feedback control of the trajectory to a target trajectory. At this time, PU52 may operate the display device 82 to execute a warning process to inform the user that the risk of jackknife has increased and that it has switched to a process to address this. However, it is desirable that PU52 does not issue a warning if the trajectory is set to a certain extent that the risk of jackknife is intentionally increased. Even when a warning is issued, it may be limited to cases where the risk at the time of issuing the warning is higher than that during manual operation.

[0074] Then, PU52 proceeds to process S36. Furthermore, when PU52 completes the process in S36, or when it makes a negative determination in the processes of S10a and S32, it temporarily terminates the series of processes shown in Figure 9.

[0075] <Correspondence> The correspondence between the matters in the above embodiment and the matters described in the "Means for Solving the Problem" section is as follows. Below, the correspondence is shown for each number of the solution means described in the "Means for Solving the Problem" section. [1,2,12] The acquisition process corresponds to the process in S12. The hitch angle variable corresponds to the hitch angle β. The steering angle variable corresponds to the steering angle θt. The prediction process corresponds to the processes in S18~S28 in Figures 3 and 9, and the processes in S18~S22, S26, S30, S50, and S52 in Figure 8. The determination process corresponds to the processes in S30 and S32 in Figures 3 and 9, and the process in S54 in Figure 8. [3] In the process in S24, this corresponds to the specified number N being "1" or greater. [4] The acquisition process corresponds to the process in S16. The prediction process corresponds to the process using the reference value VB1b set by the process in S20. The predicted value corresponds to the predicted hitch angle βe when a negative judgment is made in the S24 process. [5] The threshold setting process corresponds to the S30 process in Figures 3 and 9. The risk determination process corresponds to the S32 process in Figures 3 and 9. [6] The processes S18 to S22, S26, S30, S50, and S52 in Figure 8 correspond to the predicted value. The predicted value corresponds to the predicted hitch angle βe. The predicted time corresponds to the value of variable i at the time a positive judgment is made in the S52 process. [7] The reception process corresponds to the S42 process. The setting process corresponds to the S44 process. [8] The notification process corresponds to the S34 and S34a processes. [9] The process corresponds to the case where a positive judgment is made by the S10a process. In other words, it corresponds to the process realized by the PU52 executing the reverse assist program. The gain increase process corresponds to the S34a process.

[10] The process corresponds to the case where a positive judgment is made by the S10a process. In other words, it corresponds to the process realized by the PU52 executing the reverse assist program. The trajectory change process corresponds to the process in S34a.

[11] The corrective process corresponds to the process in S36.

[13] The computer corresponds to PU52.

[0076] <Other Embodiments> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0077] "Regarding the acquisition process" In the processing of S12, the steering angle θt detected by the steering angle sensor 70 was obtained as the steering angle variable, but this is not limited to this. For example, the yaw rate detected by the yaw rate sensor and the vehicle speed may be obtained. That is, the set of the detected value of the yaw rate sensor and the vehicle speed may be obtained as the steering angle variable. Alternatively, for example, the speed difference between the left and right wheels, or the set of the respective speeds of the left and right wheels may be obtained as the steering angle variable.

[0078] In the S26 process, the initial value of the hitch angle β was set to the hitch angle β detected by the hitch angle sensor 74, but this is not limited to this. For example, it may be an estimated value. This can be achieved, for example, by considering the hitch angle in the straight-line driving state of the vehicle as zero and estimating the hitch angle β each time using a process similar to that in S26. In other words, the value of the hitch angle variable obtained by the acquisition process is not limited to the detected value.

[0079] "Regarding predictive processing" In the S26 process in Figures 3 and 9, the predicted hitch angle βe was calculated using the current rear wheel speed VB1, but this is not the only method. For example, a predetermined vehicle speed may be used. Also, for example, in the S26 process in Figure 8, the predicted hitch angle βe may be calculated using a predetermined vehicle speed instead of the current rear wheel speed VB1. In other words, the current rear wheel speed VB1 is not essential as input for the prediction process.

[0080] In the processes shown in Figures 3 and 9, N was set to an integer greater than or equal to "1," but it is not limited to this; it may also be set to "0." In that case, it is desirable to set the unit time in process S26 to a large value.

[0081] The process for calculating the predicted hitch angle βe is not limited to the process based on the model exemplified in Figure 4. For example, a pre-trained regression model may be used, which takes the values ​​of the steering angle variable and the hitch angle variable as input and outputs the value of the predicted hitch angle βe. Here, a linear regression model or a neural network model can be used as the regression model.

[0082] "Regarding notification processing" In the above embodiment, the blinking period of the object displayed on the display device 82 was changed according to the magnitude of the risk of a jackknife occurring, but this is not limited to this embodiment.

[0083] In the above embodiment, the flashing of an object displayed on the display device 82 indicated a high risk of jackknife, but this is not limited to this. For example, an alarm sound may be used to indicate a high risk of jackknife. In this case, at least one of the type of alarm sound and the frequency of the alarm sound may be changed depending on the magnitude of the risk of jackknife occurring.

[0084] The process of notifying that there is a high risk of jackknife is not limited to a process that outputs at least one of a visual signal and an auditory signal. For example, it may be a process that increases the reaction force of the steering wheel. Or, for example, it may be a process that applies vibration to the steering wheel.

[0085] "Regarding gain increase processing" In the above embodiment, the gain was increased when it was determined that changing the trajectory was difficult, but this is not limited to this. For example, if the S32 process is positive, the process of increasing the gain may be executed at all times. In this case, the process of changing the trajectory may or may not be included.

[0086] "Regarding the handling procedures" • In the S36 process, the vehicle speed was limited to a predetermined constant speed, but this is not limited to that. For example, the upper limit vehicle speed may be changed according to the amount Δ by which the maximum steering angle θtmax exceeds the absolute value of the threshold αth. In that case, the upper limit when the amount Δ is large should be set to be greater than or equal to the upper limit when the amount Δ is small.

[0087] If the result in S32 is positive, the vehicle may be stopped by operating the drive system 62 and the braking system 64. "Regarding control devices" The control device is not limited to one that includes a PU 52 and a storage device 54 to execute software processing. For example, it may include a dedicated hardware circuit, such as an ASIC, that performs hardware processing on at least a portion of what is processed by software in the above embodiment. In other words, the control device may have any of the following configurations (a) to (c): (a) It includes a processing device that executes all of the above processing according to a program, and a program storage device such as a storage device that stores the program. (b) It includes a processing device and a program storage device that execute a portion of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) It includes a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software execution devices equipped with processing devices and program storage devices, or multiple dedicated hardware circuits.

[0088] "About the vehicle" • The vehicles shown are not limited to those illustrated in Figure 1. [Explanation of Symbols]

[0089] 10... Connected vehicles 20... Tractor 22…Front wheel 24... Rear wheel 30... Trailer 32...Wheel 40... Ball joint 42...axis 50…Control device

Claims

1. The present invention is applied to a combination vehicle including a tractor and a trailer towed by the tractor, configured to perform an acquisition process, a prediction process, a determination process, and a response process; the acquisition process is a process of acquiring a hitch angle variable that is a variable indicating a hitch angle, which is an angle between a front-rear direction of the tractor and a front-rear direction of the trailer, and a steering angle variable that is a variable indicating a steering angle of the tractor, the prediction process is a process of calculating a predicted value of the hitch angle using the hitch angle variable and the steering angle variable as inputs, the determination process is a process of determining whether or not there is a high risk of jackknife occurrence using the predicted value and the steering angle variable as inputs, The countermeasure processing is a process of operating predetermined hardware to prevent the occurrence of the jackknife when it is determined that the risk is high.

2. The jackknife suppression device according to claim 1 , wherein the acquisition process includes a process of acquiring, as the hitch angle variable, a detection value of a sensor that detects the hitch angle.

3. The jackknife suppression device according to claim 2, wherein the prediction process is a process of calculating the future hitch angle using the detected value as input, and then a process of calculating the hitch angle further into the future based on the calculated future hitch angle, and the finally calculated future hitch angle is used as the predicted value.

4. the acquisition process includes a process of acquiring a vehicle speed, 4. A jackknife suppression device according to claim 1, wherein the prediction processing includes processing for calculating the predicted value when the combined vehicle travels for a predetermined period at the acquired vehicle speed when the vehicle speed is equal to or greater than a reference value, and for calculating the predicted value when the combined vehicle travels for the predetermined period at a pre-determined vehicle speed that is greater than zero when the vehicle speed is less than the reference value.

5. The determination process includes: a threshold setting process for setting a threshold, which is a value of the steering angle variable at which the jackknife occurs, using the predicted value as an input; a risk determination process that determines that the risk is high when the amount by which the maximum possible value of the steering angle variable exceeds the magnitude of the threshold value is equal to or less than a specified value.

6. the prediction processing includes a threshold setting processing for setting a threshold, which is a value of the steering angle variable at which the jackknife occurs, using the predicted value as an input, and continuing calculation of the predicted value until the threshold reaches a predetermined value, The jackknife suppression device according to claim 3 , wherein the determination process includes a risk determination process that determines that the risk is high when a predicted time until the threshold value reaches the predetermined value is equal to or shorter than a predetermined time.

7. a receiving process for receiving a user's intention regarding the criteria for determining that the risk is high; 7. The jackknife suppression device according to claim 1, further comprising: a setting process for setting the criteria in accordance with the intention accepted by the acceptance process.

8. 8. The jackknife suppression device according to claim 1, wherein the countermeasure processing includes a notification processing for notifying a user of the combination vehicle that a high risk exists.

9. Execute an automatic steering process to automatically operate the steering angle of the trailer; The jackknife suppression device according to any one of claims 1 to 8, wherein the countermeasure processing includes a gain increase processing for increasing a gain of the automatic steering processing.

10. Execute an automatic steering process to automatically operate the steering angle of the trailer; The jackknife suppression device according to any one of claims 1 to 9, wherein the countermeasure processing includes a trajectory change processing for changing a travel trajectory of the combination vehicle caused by the automatic steering processing.

11. The jackknife suppression device according to any one of claims 1 to 10, wherein the countermeasure processing includes processing for limiting the vehicle speed to a slower speed.

12. A jackknife suppression method comprising steps of executing each process in the jackknife suppression device according to any one of claims 1 to 11.

13. A jackknife suppression program that causes a computer to execute each process in the jackknife suppression device according to any one of claims 1 to 11.

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