Device, method, and program for controlling combination vehicle

Abstract

To provide a device for controlling a combination vehicle, which can grasp a behavior of a trailer to be taken from the current state of the combination vehicle.SOLUTION: A PU 52 receives a target value of an advancing direction in a connection part of a trailer and a tractor through a user interface 80 operated by a driver. The PU 52 operates a steering system 60 so as to bring the advancing direction close to the target value, and controls the steering angle of the steering wheel of the tractor. The PU 52 calculates a predicted track of the trailer in accordance with the steering angle or the like. The PU 52 displays the predicted track on a display device 82.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] For example, Patent Document 1 below describes a control device that displays the time until the hitch angle returns to zero in a coupled vehicle.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] With the above control device, it is difficult for the driver to sequentially grasp the behavior of the trailer.

Means for Solving the Problems

[0005] Hereinafter, means for solving the above problems and their effects will be described. 1. A control device for a coupled vehicle applied to a coupled vehicle including a tractor and a trailer towed by the tractor, configured to execute a state quantity acquisition process, a predicted trajectory information calculation process, and a display process, wherein the state quantity acquisition process is a process of acquiring the state quantity of the coupled vehicle, the predicted trajectory information calculation process is a process of calculating the predicted trajectory information of the trailer according to the state quantity, and the display process is a process of displaying the predicted trajectory information by operating a display device.

[0006] In the above configuration, information regarding the predicted trajectory of the trailer, based on the state variables, is displayed. Therefore, the driver can understand the possible behavior of the trailer based on the current state of the coupled vehicle.

[0007] 2. The control device for the connected vehicle described in 1 above is provided with an interface for the driver to specify a target virtual steering angle, the target virtual steering angle being a target value for the virtual steering angle, the virtual steering angle being a variable indicating the direction of travel at the connection point between the trailer and the tractor, and configured to perform a target virtual steering angle acquisition process and a steering process, the target virtual steering angle acquisition process being a process to acquire the target virtual steering angle in response to an input operation to the interface by the driver, the predicted trajectory information calculation process being a process to calculate the predicted trajectory of the trailer when the actual virtual steering angle is brought as close as possible to the target virtual steering angle within a range where the magnitude of the steering angle of the tractor is less than or equal to an upper limit, by taking the virtual steering angle as input, the display process being a process to display the predicted trajectory, and the steering process being a process to control the steering angle of the tractor so that the virtual steering angle is brought closer to the target virtual steering angle.

[0008] In the above configuration, the control unit controls the tractor's steering angle, but the target virtual steering angle is specified by the driver. Therefore, the demands on the control unit can be reduced compared to a system where the control unit performs all operations, including setting the target virtual steering angle. Here, although the virtual steering angle can be controlled by the tractor's steering, the range of possible virtual steering angles is limited by the range of possible steering angles. Therefore, in the above configuration, the predicted trajectory of the trailer is calculated when the actual virtual steering angle is brought as close as possible to the target virtual steering angle within the range where the magnitude of the steering angle is below the upper limit. This makes the predicted trajectory a feasible trajectory for the trailer.

[0009] 3. The control device for the articulated vehicle described in 2 above is configured to perform a target trajectory calculation process, the target trajectory calculation process taking the target virtual steering angle as input and calculating the target trajectory which is the trajectory of the trailer when the virtual steering angle is set to the target virtual steering angle, and the display process includes a process of displaying the target trajectory in addition to the predicted trajectory.

[0010] In articulated vehicles, when the hitch angle is large enough, the trailer's behavior tends to remain largely unchanged regardless of how the steering angle is set. In such cases, even if the driver significantly changes the target virtual steering angle, the displayed predicted trajectory hardly changes. In this situation, there is a concern that the driver may be confused by the fact that the predicted trajectory does not change despite the change in the target virtual steering angle. In response to this, the above configuration displays a target trajectory that is determined regardless of the range of possible steering angles. The target trajectory changes significantly in response to changes in the target virtual steering angle, even in situations where the trailer's behavior hardly changes regardless of how the steering angle is set. Therefore, the discrepancy between the predicted trajectory and the target trajectory can inform the driver that the trailer's behavior hardly changes regardless of how the steering angle is set.

[0011] 4. The control device for a coupled vehicle as described in 2 above, wherein the state quantity acquisition process includes a process for acquiring the hitch angle, the hitch angle being the angle between the longitudinal direction of the tractor and the longitudinal direction of the trailer, the predicted trajectory information calculation process includes a target steering angle calculation process, an upper limit guard process, and a displacement prediction process, the target steering angle calculation process includes a process for calculating a target steering angle which is the target value of the steering angle of the tractor, taking the target virtual steering angle and the hitch angle as inputs, the upper limit guard process is a process for setting the size of the target steering angle to the upper limit value when the size of the target steering angle exceeds the upper limit value, the displacement prediction process includes a process for predicting the displacement of the trailer, taking the target steering angle after the upper limit guard process has been applied as input, and the steering process includes a process for bringing the virtual steering angle closer to the target virtual steering angle by bringing the steering angle closer to the target steering angle.

[0012] In the above configuration, the target steering angle can be set to a value that maximizes the target virtual steering angle under the condition that its magnitude is below the upper limit. 5. A control device for a coupled vehicle as described in 4 above, configured to perform a hitch angle prediction process, wherein the hitch angle prediction process is a process that predicts a future value of the hitch angle using the target steering angle with the upper limit guard process applied as input, and is configured to perform three processes multiple times: a target steering angle calculation process using the predicted hitch angle as input, a hitch angle prediction process using the target steering angle with the upper limit guard process applied as input, and a displacement prediction process using the predicted hitch angle and the target steering angle with the upper limit guard process applied as input.

[0013] There is a predetermined correlation between the virtual steering angle, the hitch angle, and the steering angle. Therefore, when the hitch angle changes, the target steering angle required to achieve the target virtual steering angle changes. Thus, in the above configuration, by executing the three processes of target steering angle calculation, hitch angle prediction, and displacement prediction multiple times, it is possible to calculate a predicted trajectory with high accuracy over a relatively long period of time.

[0014] 6. A control device for a coupled vehicle according to any one of 2 to 5 above, configured to perform a determination process, wherein the determination process is a process that determines whether or not it is in reverse assist mode, the reverse assist mode is a process that realizes the reverse process of the coupled vehicle by the steering process, and the display process is configured to be performed in the reverse assist mode.

[0015] Controlling the reverse movement of a trailer requires advanced driving skills. In this configuration, the steering process is performed in reverse assist mode, reducing the burden on the driver in steering the tractor. Furthermore, the display process provides useful information to the driver when indicating the trailer's direction of travel.

[0016] 7. The control device for the coupled vehicle described in 6 above, which is configured to continue the display process even when the coupled vehicle switches from reverse to forward in the reverse assist mode.

[0017] If the trailer's behavior is inappropriate during reverse control of a coupled vehicle, the driver may restart the reverse control by moving the coupled vehicle forward. In this case, by continuing the display processing, the driver can understand how far forward the trailer needs to move to achieve the desired behavior.

[0018] 8. The control device for the coupled vehicle described in 7 above, which is configured to perform a cancellation process, wherein the cancellation process cancels the reverse assist mode when the forward speed of the coupled vehicle exceeds a threshold.

[0019] When the forward speed is high, the driver may not want reverse control and may want to move the coupled vehicle. Therefore, in the above configuration, if the forward speed exceeds a threshold, the reverse assist mode is canceled, thus saving the driver the trouble of manually canceling the reverse assist mode.

[0020] 9. The display process is a control device for a coupled vehicle according to any one of 1 to 8 above, which includes a process of superimposing the predicted trajectory information onto an image of the outside of the coupled vehicle taken by a camera. In the above configuration, predictive trajectory information is superimposed on the camera image, making it easier to accurately understand the trailer's behavior.

[0021] 10. The display process is a control device for a coupled vehicle according to any one of 1 to 8 above, which includes a process of superimposing the predicted trajectory information onto a bird's-eye view of the vicinity of the coupled vehicle. In the above configuration, the trailer's behavior can be viewed from above by superimposing predicted trajectory information onto the bird's-eye view.

[0022] 11. A control method for articulated vehicles, comprising the step of performing each of the processes described in any one of items 1 to 10 above. 12. A control program for a articulated vehicle that causes a computer to execute each of the above processes according to any one of 1 to 10 above.

Brief Description of the Drawings

[0023] [Figure 1] It is a perspective view showing the configuration of an articulated vehicle according to an 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 diagram illustrating the reverse control of the articulated vehicle 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 flowchart showing the procedure of the process executed by the control device according to the same embodiment. [Figure 6] It is a flowchart showing the procedure of the process executed by the control device according to the same embodiment. [Figure 7] (a) and (b) are diagrams showing a display method of a predicted trajectory. [Figure 8] (a) and (b) are diagrams showing display examples according to the same embodiment. [Figure 9] (a) and (b) are diagrams showing display examples according to the same embodiment. [Figure 10] (a) and (b) are diagrams showing display examples according to the same embodiment. [Figure 11] (a) and (b) are time charts illustrating the control of a virtual steering angle according to the same embodiment. [Figure 12] (a) and (b) are diagrams showing display examples according to a modification of the above embodiment. [Figure 13] (a) and (b) are diagrams showing display examples according to a modification of the above embodiment. [Figure 14] (a) and (b) are diagrams showing display examples according to a modification of the above embodiment.

Modes for Carrying Out the Invention

[0024] The following describes one embodiment 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. The tractor 20 has front wheels 22 and rear wheels 24. The front wheels 22 include two wheels, a right front wheel and a left front wheel, and the rear wheels 24 include two wheels, a right rear wheel and a left rear wheel. Also in Figure 1, a box-shaped trailer is illustrated as the trailer 30. The trailer 30 has wheels 32. The wheels 32 include two wheels, a right wheel and a left wheel.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] The control device 50 refers to the steering angle α1 of the steering wheel detected by the steering angle sensor 70 in order to control the control amount. The steering angle α1 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 α1 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.

[0031] The control device 50 also refers to the hitch angle β detected by the hitch angle sensor 72. The hitch angle β can have either a positive or negative sign, depending on the angle between the direction of travel from rear to front of the tractor 20 and the direction of travel from rear to front of the trailer 30. For example, the sign of the hitch angle β may be positive when the direction of travel from rear to front of the trailer 30 is less than 180° counterclockwise relative to the direction of travel from rear to front of the tractor 20. The control device 50 also refers to the wheel speeds ωw1 to ωw4 detected by the wheel speed sensor 74. Wheel speeds ωw1 and ωw2 are the rotational speeds of the right front wheel 22 and the left front wheel 22, respectively. Wheel speeds ωw3 and ωw4 are the rotational speeds of the right rear wheel 24 and the left rear wheel 24, respectively. The control device 50 also refers to image data Dp showing the image of the rear of the tractor 20 captured by the rearview camera 76.

[0032] The control device 50 sets the control of the controlled quantity according to the operating state of the user interface 80. The user interface 80 is used to communicate the user's intentions to the control device 50, such as selecting either automatic driving or manual driving.

[0033] The control device 50 includes a PU 52 and a storage device 54. The PU 52 is a software processing device that includes at least one of a CPU, GPU, and TPU. The storage device 54 stores a reverse assist program 54a. The reverse assist program 54a is a program that defines a command to the PU 52 to execute the reverse assist process. The reverse assist process is a process that automatically performs the steering process of the steering wheels when the coupled vehicle 10 is driving in reverse. The reverse assist program 54a is a program that reduces the burden on the driver when driving in reverse.

[0034] In other words, as shown in Figure 3, when the linked vehicle 10 is moving in reverse, even if the steering angle of the tractor 20 is the same, the behavior of the trailer 30 changes according to the hitch angle β. Therefore, high driving skill is required for reverse control. The reverse assist process by the reverse assist program 54a assists the driver by controlling the steering angle α1 of the tractor 20. However, accelerator and brake operations are left to the driver. Furthermore, the reverse assist process leaves instructions for steering the trailer 30 to the driver. This is because if the control device 50 also sets the steering of the trailer 30, the demands on the control device 50 will increase. By leaving some instructions to the driver, it becomes possible to assist reverse control with a relatively simple process.

[0035] "Model used by reverse assist processing" Figure 4 shows a model of the articulated vehicle 10 used by the reverse assist function. 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 adopted 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 α1. The steering angle α1 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 vehicle speed Vb1 is parallel to the line defined by the front wheels C0 and the hitch point C1. In the following, the sign of the vehicle speed Vb1 when the tractor 20 is moving forward will be considered positive. The angle between the direction of vehicle speed Vb1 and the x-direction in Figure 4 is angle θ1. The angle between the line connecting wheel B2 and hitch point C1 and the x-direction is angle θ2. 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.

[0036] In this embodiment, the virtual steering angle α2, which quantifies the steering of the trailer 30, is defined as shown in Figure 4. That is, it is defined as the angle between the direction of the moving speed at the hitch point C1 and the longitudinal direction of the trailer 30.

[0037] "Reverse assist processing" Figures 5 and 6 show the procedure for the reverse assist process. The process shown in Figures 5 and 6 is achieved by the PU 52 repeatedly executing the reverse assist program 54a, for example, at a predetermined cycle. In the following, the step number of each process is represented by a number preceded by "S".

[0038] In the series of processes shown in Figures 5 and 6, PU52 first determines whether the reverse assist flag F is "1" (S10). If the reverse assist flag F is "1", it indicates that the system is in reverse assist mode and will execute the reverse assist process. On the other hand, if the reverse assist flag F is "0", it indicates that the system is not in reverse assist mode. If PU52 determines that the reverse assist flag F is "0" (S10: NO), it determines whether the system is in reverse assist mode (S12). PU52 determines that the system is in reverse assist mode when the reverse assist process is instructed by an input operation to the user interface 80. If PU52 determines that the system is in reverse assist mode (S12: YES), it assigns "1" to the reverse assist flag F (S14).

[0039] On the other hand, if PU52 determines that the reverse assist flag F is "1" (S10:YES), it determines whether the logical OR of the following conditions (A) and (B) is true (S16).

[0040] Condition (A): This condition indicates that the reverse assist mode has been deactivated by an input operation to the user interface 80. Condition (B): This condition indicates that the vehicle speed Vb1 is greater than or equal to the threshold Vth. In other words, this condition indicates that the forward speed of the tractor 20 is greater than or equal to the threshold Vth. This process is based on the assumption that the driver has stopped controlling the coupled vehicle 10 in reverse and is moving the coupled vehicle 10 a large distance.

[0041] If PU52 determines that the above logical OR is true (S16: YES), it assigns "0" to the reverse assist flag F (S18). On the other hand, if PU52 determines that the above logical OR is false (S16: NO), or if it completes the processing in S14, it obtains a target virtual steering angle α2* corresponding to the input operation to the user interface 80 (S20). The target virtual steering angle α2* is the target value of the virtual steering angle α2. In this embodiment, the target virtual steering angle α2* is instructed by the driver. Specifically, for example, the input operation may be realized by providing a dial on the user interface 80 that has a positive correlation with the virtual steering angle α2. Here, it is not essential that the rotation angle of the dial and the target virtual steering angle α2* are proportional.

[0042] Next, PU52 calculates the target trajectory Trt of the trailer 30 using the target virtual steering angle α2* as input (S22). Here, PU52 can calculate the target trajectory Trt using a two-wheel model in which the front wheel (the steering wheel) is at the hitch point C1 and the rear wheel B1 is the rear wheel. More specifically, PU52 can calculate the target trajectory Trt by calculating the curvature of the target trajectory Trt according to the target virtual steering angle α2* and the distance l2. The target trajectory Trt can be the trajectory of a representative point of the trailer 30. Here, the representative point may be, for example, the center point of the rear wheel B1. Alternatively, the representative point may be, for example, the center of gravity of the trailer 30.

[0043] Next, PU52 acquires the hitch angle β and vehicle speed Vb1 (S24). The hitch angle β is the most recent value detected by the hitch angle sensor 72. The vehicle speed Vb1 is calculated by PU52 according to the wheel speeds ωw3 and ωw4. The vehicle speed Vb1 may be, for example, a simple average of the wheel speeds ωw3 and ωw4.

[0044] Next, PU52 calculates the speed Vb2 of wheel B2 (S25). Specifically, PU52 calculates it from the geometric relationship between the hitch angle β and the vehicle speed Vb1. Next, PU52 initializes the angle θ1 (S26). Here, PU52 sets the angle θ1 to "90°". This is a setting to make the longitudinal direction of the tractor 20 the y-direction of the coordinate system shown in Figure 4.

[0045] Next, PU52 calculates the target steering angle α1*, which is the steering angle required to achieve the target virtual steering angle α2* (S28). The process in S28 takes the target virtual steering angle α2* and the hitch angle β as inputs and outputs the target steering angle α1*. That is, according to the model shown in Figure 4, the following equation (c1) holds between the steering angle α1 and the virtual steering angle α2.

[0046] α1=arctan{(l1 / h1)·tan(-α2-β)} …(c1) By replacing the virtual steering angle α2 on the right-hand side of equation (c1) with the target virtual steering angle α2*, the left-hand side becomes the target steering angle α1*.

[0047] PU52 may calculate the target steering angle α1* based on the formula corresponding to the above formula (c1). Alternatively, PU52 may perform a map calculation on the target steering angle α1*. This can be achieved by pre-storing map data in the storage device 54. Here, the map data is data that takes the target virtual steering angle α2* and the hitch angle β as input variables and the target steering angle α1* as the output variable. Note that the map data is a set of data consisting of discrete values ​​of the input variables and the values ​​of the output variables corresponding to each of the input variable values. Furthermore, the map calculation may be performed by taking the value of the corresponding output variable of the map data as the calculation result if the value of the input variable matches any of the input variable values ​​of the map data. Furthermore, if the value of the input variable does not match any of the input variable values ​​of the map data, the map calculation may be performed by taking the value obtained by interpolation of the values ​​of multiple output variables included in the map data as the calculation result. Alternatively, the map operation may be performed by taking the value of the output variable of the map data that corresponds to the closest value among the multiple input variables included in the map data, if the value of the input variable does not match any of the values ​​of the input variables in the map data, as the calculation result.

[0048] Next, PU52 determines whether the magnitude of the target steering angle α1* is greater than the upper limit α1th (S30). The upper limit α1th is the maximum possible magnitude of the steering angle α1. This process determines whether the steering angle α1 that realizes the target virtual steering angle α2* can actually be realized. If PU52 determines that it is greater than the upper limit α1th (S30: YES), it reduces the magnitude of the target steering angle α1* to the upper limit α1th (S32).

[0049] When PU52 completes the process in S32, or when it makes a negative determination in the process of S30, it controls the steering system 60 so that the steering angle α1 approaches the target steering angle α1* by operating it (S34).

[0050] Moving on to Figure 6, PU52 predicts the future hitch angle β for a predetermined time τ (S36). According to the model shown in Figure 4, the change in the hitch angle β over a predetermined time τ, Δβ, is expressed by the following equation (c2).

[0051] Δβ = -(Vb1 / l2)·sinβ·τ -{Vb1 / (l1·l2)}·(l2+h1·cosβ)·(tanα1*)·τ …(c2) In the process of S36, PU52 may calculate a predicted value of the hitch angle β by adding the change amount Δβ calculated by the above equation (c2) to the hitch angle β. Alternatively, the process of S36 may be configured to include a process in which PU52 calculates the change amount Δβ by map calculation with map data already stored. Here, the map data is data in which the vehicle speed Vb1, hitch angle β, and target steering angle α1* are input variables and the change amount Δβ of the hitch angle β is the output variable.

[0052] Next, PU52 calculates the future angle θ1 for a predetermined time τ (S38). Here, the amount of change Δθ1 in the angle θ1 during the predetermined time τ is expressed by the following equation (c3). Δθ1=(Vb1 / l1)·tan(α1*) …(c3) In the process of S36, PU52 may calculate a predicted value of angle θ1 by adding the change amount Δθ1 calculated by the above equation (c3) to angle θ1. Alternatively, in the process of S36, the change amount Δθ1 may be calculated by PU52 using map calculation with map data already stored. Here, the map data is data in which the vehicle speed Vb1 and target steering angle α1* are input variables and the change amount Δθ1 is the output variable.

[0053] Next, PU52 substitutes the sum of the hitch angle β calculated in process S36 and the angle θ1 calculated in process S38 into the future angle θ2 for a predetermined time τ (S40). Next, PU52 takes the vehicle speed Vb1 and angle θ1 as input and calculates the future tractor position coordinates (xb1, yb1) for a predetermined time τ (S44). Here, the change in the x component xb1 of the tractor position coordinates over the predetermined time τ is "Vb1·cosθ1". Also, the change in the y component yb1 of the tractor position coordinates over the predetermined time τ is "Vb1·sinθ1".

[0054] Next, PU52 takes the velocity Vb2 and angle θ2 as input and calculates the future trailer position coordinates (xb2, yb2) for a predetermined time τ (S46). Here, the change in the x component xb2 of the trailer position coordinates over the predetermined time τ is "Vb2·cosθ2". Also, the change in the y component yb2 of the trailer position coordinates over the predetermined time τ is "Vb2·sinθ2".

[0055] Next, PU52 temporarily stores the values ​​calculated by the processes in S28-S32 and S36-S46 in the memory device 54 (S48). Specifically, PU52 temporarily stores the tractor position coordinates (xb1, yb1), trailer position coordinates (xb2, yb2), angles θ1, θ2, target steering angle α1*, and hitch angle β in the memory device 54.

[0056] The PU52 then determines whether the predicted section has ended (S50). The predicted section is the section over which the coupled vehicle 10 travels for a predetermined time. The predetermined time may be, for example, a few seconds. The predicted section may have a positive correlation with the absolute value of the vehicle speed Vb1, but it may also be independent of the vehicle speed Vb1.

[0057] If PU52 determines that the prediction interval has not ended (S50: NO), it returns to the process in S28. Conversely, if PU52 determines that the prediction interval has been completed (S50: YES), it displays the predicted trajectory Trp and the target trajectory Trt on the display device 82 shown in Figure 1 (S52).

[0058] At the point when it is determined that the prediction interval has ended, the memory device 54 stores N hitch angles β that are further in the future than the hitch angle β obtained by the processing in S24. Here, N is an integer of 2 or more. These are predicted values ​​for timings separated from each other by a predetermined time τ. The memory device 54 also stores the tractor position coordinates (xb1, yb1), trailer position coordinates (xb2, yb2), angles θ1, θ2, and target steering angle α1* at timings synchronized with the N hitch angles β.

[0059] Here, the N trailer position coordinates (xb2, yb2) represent the predicted positions of representative points of the trailers 30 separated from each other by a predetermined time τ. Therefore, by connecting them, the predicted trajectory Trp can be obtained.

[0060] The process in S52 may be a process of transmitting N trailer position coordinates (xb2, yb2) to the display device 82. Alternatively, the process in S52 may be a process of finding a curve that fits the N trailer position coordinates (xb2, yb2) and transmitting parameters that identify the curve to the display device 82. In that case, the communication load can be reduced. Furthermore, by making the display device 82 merely a display function, the PU52 may generate the image to be displayed by the display device 82.

[0061] The display device 82 displays the predicted trajectory Trp and the target trajectory Trt superimposed on the image captured by the rear camera 76. Figure 7(a) shows the predicted trajectory Trp obtained by connecting the trailer position coordinates (xb2, yb2) and the target trajectory Trt. According to the processing in S26, the trailer position coordinates (xb2, yb2) are the coordinate components of a coordinate system in which the y-axis is parallel to the front-rear direction of the tractor 20. However, in order to match the image of the rear camera 76, PU52 displays point cloud data etc. obtained by projective transformation of the trailer position coordinates (xb2, yb2) as shown in Figure 7(b).

[0062] Figure 8 shows an example of an image displayed on the display screen 82a of the display device 82. More specifically, Figure 8(a) shows the state of the coupled vehicle 10, and Figure 8(b) shows an example of the display on the display screen 82a. In Figure 8, the predicted trajectory Trp is shown with a solid line and the target trajectory Trt is shown with a dashed line. However, in the actual display screen 82a, the predicted trajectory Trp and the target trajectory Trt may be distinguishable by changing their colors. The example shown in Figure 8 shows the case where the vehicle wants to turn right while reversing.

[0063] Figure 9 shows another example of an image displayed on the display screen 82a of the display device 82. Note that Figures 9(a) and 9(b) correspond to Figures 8(a) and 8(b). The example shown in Figure 9 illustrates the transition from a state of reversing and turning right to a state of moving straight.

[0064] Figure 10 shows another example of an image displayed on the display screen 82a of the display device 82. Note that Figures 10(a) and 10(b) correspond to Figures 8(a) and 8(b). The example shown in Figure 10 shows a case where the vehicle is to transition from a right turn to a left turn while reversing. In the display example shown in Figure 10, the predicted trajectory Trp is far from the target trajectory Trt. This is due to the processing in S30-S32, where the predicted trajectory Trp does not change even when the target virtual steering angle α2* is manipulated by input operations to the user interface 80. The situation in which the predicted trajectory Trp does not change is likely to occur when the hitch angle β is large, as shown in Figure 11.

[0065] Figure 11(a) shows the case where the target virtual steering angle α2* is turned back when the hitch angle β is small. Figure 11(b) also shows the case where the target virtual steering angle α2* is turned back when the hitch angle β is small.

[0066] As shown in Figure 11, when the hitch angle β is large, if the target virtual steering angle α2* is corrected, the virtual steering angle α2 cannot keep up with the target virtual steering angle α2*. Thus, if the predicted trajectory Trp does not change even when the target virtual steering angle α2* is manipulated, there is a concern that the driver may become confused as to why the predicted trajectory Trp does not change. In response to this, in this embodiment, by also displaying the target trajectory Trt, it is possible to inform the driver that if the difference between the target trajectory Trt and the predicted trajectory Trp is large, it is not possible to set the virtual steering angle α2 to the desired angle by steering the tractor 20.

[0067] According to the embodiment described above, the following effects and benefits can be obtained. (1) PU52 sets one of the axes of the coordinate system that defines the trailer coordinate components to be parallel to the front-to-rear direction of the tractor 20 each time. This makes it easy to align the trailer coordinate components with the image of the rearview camera 76.

[0068] (2) PU52 applied a projection transformation to the trailer coordinate components. This allows the trailer coordinate components to be properly aligned with the image from the rear camera 76. <Correspondence> The correspondence between the matters in the above embodiment and the matters described in the "Means for Solving the Problems" section is as follows. Below, the correspondence is shown for each number of the solution means described in the "Means for Solving the Problems" section. [1,11,12] The state quantity acquisition process corresponds to the processes in S20, S24, and S25. The predicted trajectory information calculation process corresponds to the processes in S26-S32 and S36-S50. The display process corresponds to the process in S52. The display device corresponds to the display device 82. [2] The target virtual steering angle acquisition process corresponds to the process in S20. The virtual steering angle corresponds to the virtual steering angle α2. The upper limit value corresponds to the upper limit value α1th. The steering process corresponds to the process in S34. The connection point corresponds to the ball joint 40 or the hitch point C1. [3] The target trajectory calculation process corresponds to the process in S22. [4] The target steering angle calculation process corresponds to the process in S28. The upper limit guard process corresponds to the processes in S30 and S32. [5] The displacement prediction process corresponds to the processes in S36 to S46. [6] The hitch angle prediction process corresponds to the process in S36. [7] The judgment process corresponds to the process in S12. [8] This corresponds to the condition (B) in S16. [9] This corresponds to the process of moving to S18 if an affirmative judgment is made in the process of S16.

[10] This corresponds to Figures 8 to 10, 12.

[11] This corresponds to Figures 13, 14.

[0069] <Other Embodiments> Furthermore, 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.

[0070] "Regarding the process of acquiring state variables" • In the S24 process, the hitch angle β detected by the hitch angle sensor 72 was obtained, but this is not the only method. For example, an estimated value of the hitch angle β may be obtained. This can be achieved, for example, by estimating the hitch angle β to zero when straight-line driving continues for a predetermined distance, and then sequentially updating the hitch angle β using the change amount Δβ obtained from equation (c2) above. Note that the change amount Δβ here is an estimated value of the change amount, not a predicted value of the future change amount of the hitch angle β.

[0071] "Regarding virtual steering angle" The virtual steering angle, which is a variable used to quantify the steering of the trailer, is not limited to the definition exemplified in the above embodiment. For example, the virtual steering angle may be defined as the angle between the longitudinal direction of the tractor 20 and the direction of travel of the hitch point C1.

[0072] "Regarding the calculation process for predicted trajectory information" The processes in S30, S32, etc. are not essential for calculating the predicted trajectory of the trailer 30 when the actual virtual steering angle α2 is brought as close as possible to the target virtual steering angle α2* while keeping the magnitude of the steering angle α1 below the upper limit α1th. For example, the process may include converting the upper limit α1th to the upper limit of the magnitude of the virtual steering angle α2 based on the equation (c1) above, which is solved in reverse. In that case, PU52 should apply an upper limit guard to the target virtual steering angle α2* using the upper limit of the magnitude of the virtual steering angle α2. Then, PU52 should execute the processes from S34 onward using the value obtained by converting the target virtual steering angle α2*, which has undergone upper limit guard processing, to the target steering angle α1* using the equation (c1) above.

[0073] • It is not mandatory to set the initial value of angle θ1 to "90°" in trajectory prediction. For example, by comparing map data with the longitudinal direction of the tractor 20, the angle between a predetermined axis in a coordinate system arbitrarily defined on the map data and the longitudinal direction of the tractor 20 may be used as the initial value of angle θ1 in the predicted trajectory information calculation process.

[0074] "Regarding steering maneuvers" The steering process, which controls the steering angle α1 so that the virtual steering angle α2 approaches the target virtual steering angle α2*, is not limited to the process performed in reverse assist mode. For example, it may be a process that automatically steers the tractor 20 when the coupled vehicle 10 is moving forward.

[0075] "Conditions for releasing the steering input" In the above embodiment, the condition for releasing the reverse assist mode, which is the condition for releasing the steering process, is exemplified as the logical OR of condition (A) and condition (B) being true, but it is not limited to this. For example, instead of condition (B), the condition that the coupled vehicle 10 has moved forward may be used. Alternatively, for example, only condition (A) may be used.

[0076] "Regarding display processing" It is not mandatory to display the target trajectory Trt in addition to the predicted trajectory Trp of the trailer 30. If only the predicted trajectory Trp is displayed, the area in which the trailer 30 can travel may also be displayed. In that case, if the travel path of the trailer 30 does not change much even when the steering angle α1 is changed, the width of the above area will be narrowed. Therefore, the driver can be informed that it is difficult to change the travel trajectory of the trailer 30 even if the virtual steering angle α2 is changed. Alternatively, for example, instead of displaying the above area, the driver may be informed that it is difficult to change the trajectory of the trailer 30 by manipulating the target virtual steering angle α2* when the width of the area is below a predetermined value. This may be done by displaying visual information, or by notifying by voice.

[0077] For example, as illustrated in Figures 8 and 9, if the difference between the predicted trajectory Trp and the target trajectory Trt is less than or equal to a predetermined value, only the predicted trajectory Trp may be displayed. That is, PU72 sequentially determines whether the difference between the predicted trajectory Trp and the target trajectory Trt is less than or equal to a predetermined value, and if it determines that it is less than or equal to the predetermined value, it does not need to display the target trajectory Trt. Here, the difference between the predicted trajectory Trp and the target trajectory Trt being less than or equal to a predetermined value may mean, for example, that the average value of the difference between the positions of the predicted trajectory Trp and the target trajectory Trt at the same time is less than or equal to a predetermined value. Alternatively, for example, it may mean that there are no positions where the difference between the positions of the predicted trajectory Trp and the target trajectory Trt at the same time exceeds a predetermined value.

[0078] The predicted trajectory information to be displayed is not limited to the predicted trajectory Trp. For example, as illustrated in Figure 12, the predicted trajectory Trp may have a width. Note that Figures 12(a) and 12(b) correspond to Figures 8(a) and 8(b). In Figure 12, the area determined by the boundaries TrpL and TrpR of a pair of predicted trajectories is shown as dots. In addition, the area determined by the boundaries TrtL and TrtR of a pair of target trajectories is shown as hatching. However, in the actual display screen 82a, these two areas may be distinguished by different colors.

[0079] The process of adding a range to the predicted trajectory Trp can be implemented, for example, depending on whether or not a negative determination is made in the S30 process, as follows: If the S30 process determines that a negative determination is made, PU52 should execute the S36-S46 processes using the target steering angle α1* calculated in the S28 process, with "α1*+δ" and "α1*-δ" respectively. Alternatively, if the S30 process determines that a negative determination is made, PU52 should execute the S36-S46 processes using the target steering angle α1* calculated in the S32 process and a value whose absolute value is smaller by a predetermined amount, respectively.

[0080] The process of adding width to the target trajectory Trt can be performed by calculating the boundaries TrtL and TrtR as follows: that is, the process in S22 can be performed using "α2*+δ" and "α2*-δ", which are determined by the target virtual steering angle α2* obtained by the process in S20.

[0081] Note that when applying a range to the predicted trajectory Trp, it is not mandatory to apply a range to the target trajectory Trt. For example, the target trajectory Trt may be displayed as a single trajectory. Also, when applying a range to the predicted trajectory Trp, it is not necessary to display any visual information related to the target trajectory Trt.

[0082] For example, as described in the section on "Steering Processing," when automatically controlling the steering of the coupled vehicle 10 while it is moving forward, the predicted trajectory Trp of the tractor 20 can be superimposed on the image of the front of the tractor 20.

[0083] The process of displaying the predicted trajectory Trp is not limited to superimposing the predicted trajectory Trp onto the image of the surroundings of the coupled vehicle 10 captured by the camera. For example, a bird's-eye view may be used, as illustrated in Figure 13. Figures 13(a) and 13(b) correspond to Figures 8(a) and 8(b). This is particularly effective in the process of assisting the rearward movement of a coupled vehicle 10 with a predetermined trailer 30, such as a camper van. That is, as shown by the dashed line in Figure 1, if the trailer 30 is tall, the rear of the trailer 30 cannot be captured in the image taken by the rearview camera 76.

[0084] Furthermore, the predicted trajectory information superimposed on the bird's-eye view is not limited to the predicted trajectory Trp. For example, as mentioned above, the region obtained by giving width to the predicted trajectory Trp may also be superimposed and displayed on the bird's-eye view.

[0085] In addition to displaying the predicted trajectory information of the trailer 30, the predicted trajectory information of the tractor 20 may also be displayed. In Figure 14, the predicted trajectory Trp and target trajectory Trt are superimposed on a bird's-eye view, and the predicted trajectory Tr1L at the left end and the predicted trajectory Tr1R at the right end of the tractor 20 are also displayed. Figures 14(a) and 14(b) correspond to Figures 8(a) and 8(b). Note that the method for displaying the predicted trajectory of the tractor 20 is not limited to displaying both the predicted trajectory Tr1L at the left end and the predicted trajectory Tr1R at the right end. For example, a method for displaying a single predicted trajectory, such as the predicted trajectory of the center of gravity of the tractor 20, may be used. Alternatively, a region with a width may be displayed, such as by marking the area between the predicted trajectory Tr1L at the left end and the predicted trajectory Tr1R at the right end.

[0086] Furthermore, using a bird's-eye view is not essential for the method of displaying the predicted trajectory information of the tractor 20 along with the predicted trajectory information of the trailer 30. For example, it could be superimposed on an image of the exterior of the articulated vehicle 10. Also, it is not essential to display the target trajectory information of the trailer 30 together.

[0087] The predicted trajectory information of the trailer 30 to be displayed does not necessarily have to be the predicted trajectory Trp or an area with a width over the predicted trajectory Trp. For example, when the articulated vehicle 10 is manually steered, if the direction of travel of the trailer 30 is not straight, the arrows on the right or left indicating the direction of travel of the trailer 30 may be displayed.

[0088] "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.

[0089] "About computers" The computer that executes control programs such as the reverse assist program 54a is not limited to the computer mounted on the articulated vehicle 10. For example, the computer may be composed of both the PU 52 mounted on the articulated vehicle 10 and the driver's mobile terminal. In that case, for example, the mobile terminal may execute the processes S28-S32 and S36-S50.

[0090] "About the vehicle" • The coupled vehicles are not limited to those exemplified in Figure 1. [Explanation of Symbols]

[0091] 10... Connected vehicles 20... Tractor 22…Front wheel 24... Rear wheel 30... Trailer 32...Wheel 40... Ball joint 42...axis 50…Control device 82a…Display screen

Claims

1. The present invention is applied to a combination vehicle including a tractor and a trailer towed by the tractor, configured to execute a state quantity acquisition process, a predicted orbit information calculation process, and a display process; the state quantity acquisition process is a process for acquiring state quantities of the combination vehicles, the predicted trajectory information calculation process is a process of calculating predicted trajectory information of the trailer in accordance with the state quantity, A control device for articulated vehicles, wherein the display processing is processing for displaying the predicted trajectory information by operating a display device.

2. the articulated vehicle is provided with an interface for a driver to specify a target virtual steering angle; the target virtual steering angle is a target value of the virtual steering angle, the virtual steering angle is a variable indicating the traveling direction of a connection point between the trailer and the tractor, configured to execute a target virtual steering angle acquisition process and a steering process, the target virtual steering angle acquisition process is a process of acquiring the target virtual steering angle in response to an input operation by the driver to the interface, the predicted trajectory information calculation process is a process that uses the virtual steering angle as an input to calculate a predicted trajectory of the trailer when the actual virtual steering angle is brought as close as possible to the target virtual steering angle within a range in which the magnitude of the steering angle of the tractor is equal to or less than an upper limit value, the display process is a process of displaying the predicted trajectory, 2. The control device for an articulated vehicle according to claim 1, wherein the steering process controls the steering angle of the tractor so that the virtual steering angle approaches the target virtual steering angle.

3. configured to execute a target trajectory calculation process, the target trajectory calculation process is a process of inputting the target virtual steering angle and calculating a target trajectory, which is a trajectory of the trailer when the virtual steering angle is set to the target virtual steering angle, The control device for articulated vehicles according to claim 2 , wherein the display process includes a process of displaying the target trajectory in addition to the predicted trajectory.

4. the state quantity acquisition process includes a process of acquiring a hitch angle, The hitch angle is an angle between the front-rear direction of the tractor and the front-rear direction of the trailer, the predicted trajectory information calculation process includes a target steering angle calculation process, an upper limit guard process, and a displacement prediction process, the target steering angle calculation process includes a process of calculating a target steering angle that is a target value of the steering angle of the tractor using the target virtual steering angle and the hitch angle as inputs, the upper limit guard process is a process for setting the magnitude of the target steering angle to the upper limit value when the magnitude of the target steering angle exceeds the upper limit value, the displacement prediction process includes a process of predicting a displacement of the trailer using the target steering angle that has been subjected to the upper limit guard process as an input, 3. The control device for articulated vehicles according to claim 2, wherein the steering process includes a process of bringing the virtual steering angle closer to the target virtual steering angle by bringing the steering angle closer to the target steering angle.

5. configured to perform a hitch angle prediction process; the hitch angle prediction process is a process for predicting a future value of the hitch angle using the target steering angle that has been subjected to the upper limit guard process as an input, 5. A control device for articulated vehicles according to claim 4, wherein the three processes of the target steering angle calculation process, which receives the predicted hitch angle as an input, the hitch angle prediction process, which receives the target steering angle after the upper limit guard process as an input, and the displacement prediction process, which receives the predicted hitch angle and the target steering angle after the upper limit guard process as inputs, are executed a plurality of times.

6. configured to perform a determination process; The determination process is a process for determining whether or not the vehicle is in a reverse assist mode, the reverse assist mode is a process for realizing a reverse process of the combination vehicle by the steering process, 3. The control device for articulated vehicles according to claim 2, wherein the display process is executed in the reverse assist mode.

7. 7. The control device for an articulated vehicle according to claim 6, wherein the display process is continued even when the articulated vehicle switches from reverse to forward in the reverse assist mode.

8. configured to perform a cancellation process, 8. The control device for an articulated vehicle according to claim 7, wherein the cancellation process is a process of canceling the reverse assist mode when the forward traveling speed of the articulated vehicle is equal to or greater than a threshold value.

9. The control device for an articulated vehicle according to claim 1 , wherein the display process includes a process of superimposing the predicted trajectory information on an image of the outside of the articulated vehicle captured by a camera.

10. The control device for articulated vehicles according to claim 1 , wherein the display process includes a process of superimposing the predicted trajectory information on a bird's-eye view of the vicinity of the articulated vehicles.

11. A method for controlling an articulated vehicle, comprising the steps of executing each of the processes according to claim 1.

12. A control program for articulated vehicles that causes a computer to execute each of the processes according to claim 1.

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