Control device for articulated vehicles, control method for articulated vehicles, and control program for articulated vehicles

Abstract

A trailer is provided with an operating unit (52) mechanically connected to a steered wheel (22), and an actuator (60) for steering the steered wheel. An articulated vehicle control device (80) is configured to execute acquisition processing and steering control processing. The acquisition processing is processing for acquiring a vehicle speed and an angle detected value. The angle detected value is a detected value, obtained by a sensor, of a value of an angle variable related to steering of the articulated vehicle. The steering control processing includes vehicle speed dependent processing, which is processing for operating the actuator on the basis of the angle detected value, serving as an input variable. The vehicle speed dependent processing is processing whereby the responsiveness of the actuator operating amount with respect to a change in the angle detected value is reduced for a case in which the vehicle speed is low compared to a case in which the vehicle speed is high.

Description

[Technical Field]

[0001] The present disclosure relates to a control device for articulated vehicles, a control method for articulated vehicles, and a control program for articulated vehicles. [Background technology]

[0002] For example, Patent Document 1 listed below describes a device that uses a hitch angle sensor to control the running of an articulated vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 10,421,490 Summary of the Invention [Problem to be solved by the invention]

[0004] However, noise is superimposed on the detection value of a sensor that detects the steering angle of an articulated vehicle. When the influence of the noise is reflected in the control, vibrations are superimposed on the control of the steered wheels. Therefore, when an operating unit operated by a driver to steer the vehicle and the steered wheels are mechanically connected, vibrations that the user can sense are generated in the operating unit. [Means for solving the problem]

[0005] One aspect of the present disclosure provides a control device for a combination vehicle in which a tractor and a trailer are coupled together. The trailer includes an operating unit mechanically coupled to steerable wheels, and an actuator that steers the steerable wheels. The control device for the combination vehicle is configured to execute an acquisition process and a steering control process. The acquisition process is a process for acquiring vehicle speed and a detected angle value. The detected angle value is a value detected by a sensor of an angle variable related to the steering of the combination vehicle. The steering control process is a process for operating an actuator based on the detected angle value as an input variable, and includes a vehicle speed-dependent process. The vehicle speed-dependent process is a process for reducing the responsiveness of the actuator's operation amount to changes in the detected angle value when the vehicle speed is low compared to when the vehicle speed is high.

[0006] Another aspect of the present disclosure provides a method for controlling a combination vehicle in which a tractor and a trailer are coupled together. The trailer includes an operating unit mechanically coupled to steerable wheels, and an actuator that steers the steerable wheels. The control method for the combination vehicle includes executing an acquisition process and a steering control process. The acquisition process is a process for acquiring vehicle speed and a detected angle value. The detected angle value is a value detected by a sensor of an angle variable related to steering of the combination vehicle. The steering control process is a process for operating an actuator based on the detected angle value as an input variable, and includes a vehicle speed-dependent process. The vehicle speed-dependent process is a process for reducing the responsiveness of the actuator operation amount to changes in the detected angle value when the vehicle speed is low compared to when the vehicle speed is high.

[0007] Another aspect of the present disclosure provides a control program for a combination vehicle in which a tractor and a trailer are coupled together. The trailer includes an operating unit mechanically coupled to the steerable wheels, and an actuator that steers the steerable wheels. The control program for the combination vehicle includes instructions to cause a computer to execute an acquisition process and a steering control process. The acquisition process is a process for acquiring vehicle speed and a detected angle value. The detected angle value is a value detected by a sensor of an angle variable related to the steering of the combination vehicle. The steering control process is a process for operating an actuator based on the detected angle value as an input variable, and includes a vehicle speed-dependent process. The vehicle speed-dependent process is a process for reducing the responsiveness of the actuator's operation amount to changes in the detected angle value when the vehicle speed is low compared to when the vehicle speed is high. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an articulated vehicle according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of a control system according to the embodiment. [Figure 3] 3 is a flowchart showing a procedure of a process executed by a control device according to the embodiment. [Figure 4] FIG. 2 is a diagram showing a model of an articulated vehicle according to the embodiment. [Figure 5] 4 is a time chart illustrating time series data of detected values ​​of the sensor according to the embodiment; [Figure 6] FIG. 4 is a diagram showing the relationship between the vehicle speed and the steering speed required for control according to the embodiment. [Figure 7] 10 is a flowchart showing a procedure of a process executed by a control device according to a second embodiment. [Figure 8] 4 is a time chart showing the effect of the embodiment. [Figure 9] 10 is a flowchart showing a procedure of a process executed by a control device according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

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

[0011] FIG. 2 shows some of the members provided on the tractor 20. As shown in FIG. 2, a steering wheel 52 in a steering system 50 provided in the tractor 20 rotates integrally with a steering shaft 54. The steering wheel 52 corresponds to an operating unit mechanically connected to the steered wheels. The rotational power of the steering wheel 52 is converted into a steering force for the front wheels 22 via a steering shaft 54 ​​and a rack shaft 56. A steering actuator 60 is mechanically connected to the steering shaft 54. The steering actuator 60 converts the power of a motor 62 into rotational power for the steering shaft 54. The output voltage of an inverter 64 is applied to the terminals of the motor 62.

[0012] The controller 66 controls the torque of the motor 62 to control the control amount of the front wheels 22, which are the control target. Here, the control amount is the steering angle. The steering angle is the turning angle of the tires of the front wheels 22. To control the control amount, the controller 66 refers to the rotation angle θm of the motor 62 detected by the rotation angle sensor 68.

[0013] The tractor 20 is equipped with a drivetrain 70. The drivetrain 70 includes at least one of an internal combustion engine and a rotating electric machine as a vehicle thrust generating device. The tractor 20 is equipped with a braking system 72. The braking system 72 includes at least one of a device that slows down the rotation of the wheels by frictional force and a device that slows down the rotation of the wheels by converting the power of the wheels into electrical energy. Note that the device that slows down the rotation of the wheels by converting into electrical energy may be shared with the rotating electric machine of the drivetrain.

[0014] The tractor 20 is equipped with an ADASECU 80. The ADASECU 80 operates the steering system 50, drive system 70, and braking system 72 to control the control variables of the combined vehicle 10, which is the control target. The control variables include vehicle speed, driving direction, and hitch angle. The hitch angle is the angle between the fore-and-aft direction of the tractor 20 and the fore-and-aft direction of the trailer 30. The drive system 70 may include a drive control device that controls an internal combustion engine and a rotating electric machine. In this case, "the ADASECU 80 operates the drive system 70" means that the ADASECU 80 outputs a command signal to the drive control device. Furthermore, the braking system 72 may include a braking control device that controls a device that slows down the rotation of the wheels. In this case, "the ADASECU 90 operates the braking system 82" means that the ADASECU 80 outputs a command signal to the braking control device. Furthermore, "the ADASECU 80 operates the steering system 50" means that the ADASECU 80 outputs a command signal to the controller 66.

[0015] To control the control variable, the ADASECU80 references the hitch angle β detected by the hitch angle sensor 90. The hitch angle β can be either positive or negative depending on the angle between the direction in which the tractor 20 moves forward and the direction in which the trailer 30 moves forward. For example, the sign of the hitch angle β may be positive when the direction in which the trailer 30 moves forward is offset counterclockwise by less than 180 degrees from the direction in which the tractor 20 moves forward. The ADASECU80 also references wheel speeds ωw1 to ωw4 detected by the wheel speed sensor 92. The wheel speeds ωw1 and ωw2 are the rotational speeds of the right front wheel 22 and the left front wheel 22, respectively. The wheel speeds ωw3 and ωw4 are the rotational speeds of the right rear wheel 24 and the left rear wheel 24, respectively.

[0016] The ADASECU80 sets the control of the control amount according to the operation state of the user interface 94. The user interface 94 is used to communicate the user's intention to the ADASECU80, such as selecting either automatic driving or manual driving.

[0017] The ADASECU 80 comprises a PU 82 and a storage device 84. The PU 82 is a software processing device comprising at least one of a CPU, a GPU, a TPU, etc. A reverse assist program 84a is stored in the storage device 84. The reverse assist program 84a is a program that prescribes commands for causing the PU 82 to execute reverse assist processing. The reverse assist processing is processing that automatically performs steering processing of the steered wheels when the combination vehicle 10 is traveling in reverse. The reverse assist program 84a is a program that reduces the burden on the driver when driving in reverse.

[0018] In other words, when the combination vehicle 10 is traveling in reverse, even if the steering angle of the tractor 20 is the same, the behavior of the trailer 30 changes depending on the hitch angle β. For this reason, high driving skill is required for reverse control. The reverse assist process by the reverse assist program 84a is a process that assists the driver by controlling the steering angle of the tractor 20. However, the reverse assist process leaves instructions regarding steering of the trailer 30 to the driver.

[0019] "Steering during reverse assist processing" The procedure for the reverse assist process is shown in Figure 3. The process shown in Figure 3 is realized by the PU 82 repeatedly executing the reverse assist program 84a, for example, at a predetermined interval. Note that, below, the step numbers of each process are represented by numbers preceded by "S."

[0020] 3, the PU 82 first determines whether the vehicle is in the reverse assist mode (S10). If the PU 82 determines that the vehicle is in the reverse assist mode (S10: YES), the PU 82 acquires the hitch angle β detected by the hitch angle sensor 90 (S12). The PU 82 also acquires the turning angle α1 detected by the steering system 50 (S14). Specifically, the turning angle α1 is a value calculated by the controller 66 using the rotation angle θm.

[0021] Then, the PU 82 calculates a virtual steering angle α2 using the steering angle α1 and the hitch angle β as inputs (S16). The virtual steering angle α2 is a variable that indicates the traveling direction of the connection point between the trailer 30 and the tractor 20. In other words, it is a variable that indicates the traveling direction of the shaft 42 shown in Figure 1. In this embodiment, as an example, the virtual steering angle α2 is defined by the angle that the traveling direction of the ball joint 40 makes with respect to the fore-and-aft direction of the trailer 30.

[0022] Here, the reason why the virtual steering angle α2 is calculated from the turning angle α1 and the hitch angle β will be explained with reference to FIG. FIG. 4 shows a model of the articulated vehicle 10 used in this embodiment. In the model shown in FIG. 4, the pair of front wheels 22 of the tractor 20 are regarded as a single front wheel C0, and the pair of rear wheels 24 of the tractor 20 are regarded as a single rear wheel B1. In other words, a two-wheel model is used for the tractor 20. The pair of wheels 32 of the trailer 30 are regarded as a single wheel B2. The angle between the line defined by the front wheel C0 and hitch point C1 and the line defined by the hitch point C1 and wheel B2 is the hitch angle β. The hitch point C1 corresponds to the axle 42 in FIG. 1. The front wheel speed VC0, which is the speed of the front wheel C0, is a vector that moves in the direction of the steering angle α1. The steering angle α1 is quantified as the angle between the direction of travel of the front wheel C0 and the line defined by the front wheel C0 and hitch point C1. The direction of vehicle speed V is parallel to the line defined by the front wheel C0 and hitch point C1. The angle between the direction of vehicle speed V and the x direction in FIG. 4 is θ1. The angle between the line connecting wheel B2 and hitch point C1 and the x direction is θ2. Distance l1 is the length between the front wheel C0 and rear wheel B1. Distance h1 is the length between the rear wheel B1 and hitch point C1. Distance l2 is the length between the hitch point C1 and wheel B2.

[0023] According to the above definition, the direction of the velocity VC1 of the hitch point C1 relative to the direction of travel from wheel B2 to hitch point C1 is the virtual steering angle α2. Using the angle γ1 formed by the direction of the velocity VC1 of the hitch point C1 relative to the direction of travel from hitch point C1 to front wheel C0, the virtual steering angle α2 is expressed as "-(β-γ1)".

[0024] In the model shown in FIG. 4, the following equations (c1) to (c3) are established using the coordinates (xc0, yc0) of the front wheel C0, the coordinates (xb1, yb1) of the rear wheel B1, and the coordinates (xc1, yc1) of the hitch point C1.

[0025] VC0·cosα1=V …(c1) xc0=xb1+l1·cosθ1 …(c2) xc1=xb1-h1·cosθ1 …(c3) By differentiating both sides of the above equations (c2) and (c3) and using equation (c1), we obtain the following equation (c4).

[0026] h1·tanα1+l1·tanγ1=0 …(c4) According to the above formula (c4), the angle γ1 can be expressed by the steering angle α1. Therefore, the virtual steering angle α2 is expressed by the following formula (c5).

[0027] α2=-β-arctan{(h1 / l1)·tan(α1)} …(c5) That is, the virtual steering angle α2 can be calculated from the hitch angle β and the steering angle α1. The process of S16 shown in Fig. 3 may be a process using the above equation (c5). Alternatively, the process of S16 may be a process in which the PU 82 calculates the virtual steering angle α2 using a map by storing map data in the storage device 84. The map data is data in which the hitch angle β and the steering angle α1 are input variables and the virtual steering angle α2 is an output variable.

[0028] Here, map data is a set of data consisting of discrete values ​​of input variables and values ​​of output variables corresponding to each of the input variable values. Furthermore, map calculation may be a process in which, when the value of an input variable matches one of the input variable values ​​in the map data, the value of the corresponding output variable in the map data is the calculation result. Furthermore, map calculation may be a process in which, when the value of an input variable does not match any of the input variable values ​​in the map data, the calculation result is a value obtained by interpolating the values ​​of multiple output variables included in the map data. Alternatively, map calculation may be a process in which, when the value of an input variable does not match any of the input variable values ​​in the map data, the calculation result is the value of the output variable in the map data that corresponds to the closest value of the multiple input variables included in the map data.

[0029] Returning to FIG. 3, the PU 82 acquires the target virtual steering angle α2* input to the user interface 94 (S18). The target virtual steering angle α2* is a target value of the virtual steering angle α2. The target virtual steering angle α2* is a variable indicating the driver's instruction regarding the steering of the trailer 30.

[0030] Next, PU82 calculates target steering angle α1* as a manipulated variable for feedback control in which virtual steering angle α2 is the controlled variable and target virtual steering angle α2* is the controlled variable target value (S20). Here, feedback control may be, for example, processing in which the output value of a proportional element, to which the difference between target virtual steering angle α2* and virtual steering angle α2 is input, is the target steering angle α1*. Alternatively, for example, feedback control may be processing in which the target steering angle α1* is the sum of the output value of a proportional element and the output value of an integral element, to which a value corresponding to the difference between target virtual steering angle α2* and virtual steering angle α2 is input. Alternatively, for example, feedback control may be processing in which the target steering angle α1* is the sum of the output value of a proportional element and the output value of a derivative element, to which a value corresponding to the difference between target virtual steering angle α2* and virtual steering angle α2 is input. For example, the feedback control may be a process in which the sum of the output value of a proportional element, the output value of a differential element, and the output value of an integral element, whose input is a value corresponding to the difference between the target virtual steering angle α2* and the virtual steering angle α2, is the target steering angle α1*.

[0031] Next, the PU 82 acquires the vehicle speed V (S22). The vehicle speed V is calculated by the PU 82 using at least one of the four wheel speeds ωw1 to ωw4. The processes of S12, S14, and S22 correspond to the acquisition process. The detected angle values ​​correspond to the hitch angle β and the steering angle α1. The PU 82 then calculates a guard value Δα1th of the magnitude of the rate of change of the target steering angle α1* in accordance with the vehicle speed V (S24). Specifically, the PU 82 variably sets the guard value Δα1th in accordance with the vehicle speed V, on the condition that the guard value Δα1th when the vehicle speed V is high is equal to or greater than the guard value Δα1th when the vehicle speed V is low. This process may be, for example, a process in which the PU 82 calculates the guard value Δα1th using a map while map data is stored in the storage device 84. Here, the map data is data in which the vehicle speed V is an input variable and the guard value Δα1th is an output variable. This map data includes different values ​​for the guard value Δα1th.

[0032] In the description "changing B according to A on the condition that B when A is large is equal to or larger than B when A is small," the case where A is large and the case where A is small refer to the relative relationship of magnitude when comparing the two. For example, "when A is large" corresponds to the case where "A is a first value," and "when A is small" corresponds to the case where "A is a second value smaller than the first value." The above description also means that, depending on the settings of the first and second values, B when A is the first value may be larger than B when A is the second value. The above description also means that B is changed according to A so that A when B is large is larger than A when B is small.

[0033] Next, the PU 82 determines whether the absolute value of the difference between the current value "α1*(n)" of the target steering angle α1* and the previous value "α1*(n-1)" is greater than the guard value Δα1th (S26). If the PU 82 determines that the absolute value is greater than the guard value Δα1th (S26: YES), the PU 82 sets the target steering angle α1* to a value that has a change from the previous value that is equal to the guard value Δα1th and is closest to the value calculated by the processing of S20 (S28). Then, the PU 82 outputs the target steering angle α1* to the controller 66 (S30). That is, the PU 82 operates the steering system 50 so that the steering angle α1 approaches the target steering angle α1*.

[0034] When the process of S30 is completed or when a negative determination is made in the process of S10, the PU 82 temporarily ends the series of processes shown in Fig. 3. The processes of S16 to S30 correspond to the steering control process. The processes of S24 to S28 correspond to the vehicle speed dependent process.

[0035] "Actions and Effects of the Present Embodiment" Noise is superimposed on the hitch angle β and the steering angle α1, which are values ​​corresponding to the detected values ​​of the sensors of the angle variables related to the steering of the articulated vehicle 10.

[0036] The time course of the hitch angle β is shown in Figure 5. As shown in Figure 5, noise is superimposed on the hitch angle β, causing the value to fluctuate up and down. Fig. 6 shows the relationship between the steering speed, which is the steering speed required for control, and the vehicle speed V. As shown in Fig. 6, the steering speed Vd required for control increases as the vehicle speed V increases. This is for the following reason.

[0037] That is, the time derivative of the hitch angle β is expressed by the following equation (c6) according to the model equation of FIG. 4: dβ / dt= (V / l2)·sinβ +{V / (l1·l2)}·{l2+h1·cosβ}·tanα1 …(c6) According to equation (c6), the time derivative of the hitch angle β is proportional to the vehicle speed V.

[0038] Furthermore, when both sides of the above equation (c5) are differentiated with respect to time, the time derivative of the virtual steering angle α2 is the sum of a term including the time derivative of the hitch angle β and the time derivative of the steering angle α1. Therefore, the time derivative of the steering angle α1 can be considered to be the sum of a term proportional to the time derivative of the virtual steering angle α2 and a term proportional to the time derivative of the hitch angle. Here, the proportionality coefficient depends on the steering angle α1. Therefore, according to the above equation (c6), the time derivative of the steering angle α1 is also proportional to the vehicle speed V. Furthermore, the term proportional to the time derivative of the virtual steering angle α2 can be considered to be the sum of a term proportional to the time derivative of the steering angle α1 and a term proportional to the time derivative of the hitch angle. Therefore, according to the above equation (c6), the time derivative of the virtual steering angle α2 is also proportional to the vehicle speed V.

[0039] The steering speed depends on the time differential of the steering angle α1, the time differential of the hitch angle β, or the time differential of the virtual steering angle α2. Therefore, the steering speed Vd required for control increases as the vehicle speed V increases.

[0040] FIG. 6 also shows noise NW caused by the detected values ​​of the sensors. As shown in Fig. 6, the steering speed Vd required for control is smaller than the noise NW component until the vehicle speed V reaches the threshold Vth. For convenience, the vertical axis in Fig. 6 represents speed, but more accurately, the higher the vertical axis, the higher the frequency.

[0041] As shown in Figure 6, when vehicle speed V is low, the effect of noise on hitch angle β and steering angle α1 may cause target steering angle α1* calculated by the processing of S20 to change more rapidly than necessary. If target steering angle α1* used for control fluctuates frequently due to the effect of noise, the torque of motor 62, which controls steering angle α1 to target steering angle α1*, fluctuates frequently. High-frequency fluctuations in the torque of motor 62 cause vibrations in steering wheel 52.

[0042] Therefore, PU 52 limits the magnitude of the rate of change of target steering angle α1* used for control to equal to or less than guard value Δα1th. This makes it possible to prevent target steering angle α1* from fluctuating suddenly and frequently due to noise in the detected values ​​of hitch angle β and rotation angle θm. Therefore, it is possible to prevent vibration from occurring in steering wheel 52 when articulated vehicle 10 is being driven at extremely low speeds.

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

[0044] Figure 7 shows the procedure of the reverse assist process according to this embodiment. The process shown in Figure 7 is realized by the PU 82 repeatedly executing the reverse assist program 84a, for example, at a predetermined interval. For convenience, the same step numbers are used in Figure 7 to designate processes corresponding to those shown in Figure 3.

[0045] In the series of processes shown in FIG. 7, when it is determined that the mode is the reverse assist mode (S10: YES), the PU 82 acquires the vehicle speed V (S22). Then, the PU 82 sets the cutoff frequency fc of a low-pass filter (described later) (S40). The PU 82 sets the cutoff frequency fc according to the vehicle speed V under the condition that the cutoff frequency fc when the vehicle speed V is low is equal to or lower than the cutoff frequency fc when the vehicle speed V is high. This may be realized, for example, by having the PU 82 perform map calculations to determine the cutoff frequency fc with map data stored in the storage device 84. The map data is data in which the vehicle speed V is an input variable and the cutoff frequency fc is an output variable. The map data includes values ​​that are different from one another as values ​​of the output variables.

[0046] Then, the PU 82 performs filtering processing using a low-pass filter with a cutoff frequency fc on the hitch angle β obtained by the processing of S12 (S42). The PU 82 also performs filtering processing using a low-pass filter with a cutoff frequency fc on the steering angle α1 obtained by the processing of S14 (S44).

[0047] Then, the PU 82 executes the processes of S16 to S20 and S30. Note that the hitch angle β and the steering angle α1 in the process of S16 are values ​​that have been subjected to low-pass filtering in the processes of S42 and S44.

[0048] When the process of S30 is completed or when a negative determination is made in the process of S10, the PU 82 temporarily ends the series of processes shown in Fig. 7. The processes of S40, S42, S44, S16 to S20, and S30 correspond to the steering control process. The processes of S40, S42, and S44 correspond to the vehicle speed dependent process.

[0049] "Actions and Effects of the Present Embodiment" PU82 calculates a virtual steering angle α2 using the low-pass filtered hitch angle β and steering angle α1. Then, it calculates a target steering angle α1* as a manipulated variable for feedback control, in which the virtual steering angle α2 is a control variable and the target virtual steering angle α2* is a target value of the control variable. Here, the hitch angle β and steering angle α1 are subjected to low-pass filtering, so the influence of noise is suppressed. Therefore, the virtual steering angle α2 is suppressed from fluctuating significantly due to noise. Therefore, it is possible to suppress fluctuations in the target steering angle α1* due to the influence of noise.

[0050] In particular, the cutoff frequency fc of the PU 82 is set to be larger as the vehicle speed V is higher. When the vehicle speed V is high, the rate of change of the steering angle α1 required for control also increases. Therefore, according to this embodiment, it is possible to achieve an appropriate compromise between suppressing the influence of noise and improving the responsiveness of the control of the virtual steering angle α2.

[0051] In particular, when low-pass filtering is performed, it is possible to improve the controllability of the virtual steering angle α2 when it is not possible to accurately determine whether the combination vehicle 10 is stopped. In other words, if the accuracy of determining whether the combination vehicle 10 is stopped is low, there is a risk that the combination vehicle 10 will be erroneously determined to be stopped when it is traveling at an extremely low speed. Furthermore, if control is to be stopped when the combination vehicle 10 is stopped, it is not possible to control the virtual steering angle α2.

[0052] The left side of Figure 8 shows the changes in virtual steering angle α2, hitch angle β, steering angle α1, and vehicle speed V when it is erroneously determined that articulated vehicle 10 is stopped and hitch angle β and steering angle α1 are fixed to the values ​​they had immediately before the vehicle stopped. In this case, PU 82 recognizes that virtual steering angle α2, hitch angle β, and steering angle α1 will be maintained at the values ​​they had immediately before the vehicle stopped, and therefore cannot control virtual steering angle α2.

[0053] On the other hand, the case of this embodiment is shown on the right side of Figure 8. In this case, the hitch angle β and the steering angle α1 that have been subjected to low-pass filtering change, and therefore the virtual steering angle α2 also changes. Therefore, control can be achieved to bring the virtual steering angle α2 closer to the target virtual steering angle α2*.

[0054] <Third embodiment> The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0055] Figure 9 shows the procedure of the reverse assist process according to this embodiment. The process shown in Figure 9 is realized by the PU 82 repeatedly executing the reverse assist program 84a, for example, at a predetermined interval. For convenience, the same step numbers are used in Figure 9 to designate processes corresponding to those shown in Figure 3.

[0056] In the series of processes shown in FIG. 9, when the processes of S10 and S22 are completed, the PU 82 determines whether the vehicle speed V is zero (S50). When the PU 82 determines that the vehicle speed V is zero (S50: YES), the PU 82 assigns the previous value "β(n-1)" to the hitch angle β to be used this time (S12a). Furthermore, the PU 82 assigns the previous value "α1(n-1)" to the steering angle α1 to be used this time (S14a). Then, the PU 82 executes the processes of S16 to S20 and S30. The process of S50 corresponds to the determination process. The processes of S12a and S14a correspond to the hold process.

[0057] The PU 82 temporarily terminates the series of processes shown in Fig. 9 when completing the process of S30 or when a negative determination is made in the process of S10. Incidentally, when a negative determination is made in the process of S50, the PU 82 may execute the processes shown in Fig. 3 or 7. The processes of S50, S12a, S14a, S16 to S20, and S30 correspond to the steering control process. Furthermore, the processes of S40, S42, and S44 correspond to the vehicle speed dependent process.

[0058] "Actions and Effects of the Present Embodiment" When PU 82 determines that vehicle speed V is zero, it holds hitch angle β and steering angle α1 at the values ​​they had immediately before vehicle speed V became zero. Therefore, the virtual steering angle α2 used in the processing of S20 is also held at the value they had immediately before vehicle speed V became zero. This prevents target steering angle α1* from fluctuating due to the influence of noise superimposed on hitch angle β and steering angle α1 that are detected each time. Therefore, fluctuations in the torque of motor 62 can be suppressed when combined vehicles 10 are stopped. If the torque applied to steering wheel 52 fluctuates when combined vehicles 10 are stopped, the user is particularly likely to feel uncomfortable. In contrast, this embodiment prevents such problems from occurring.

[0059] <Other embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0060] "About steering control processing" The steering control process is not limited to a process in which the target steering angle α1* is the operation amount of feedback control in which the virtual steering angle α2 is the control amount and the target virtual steering angle α2* is the target value of the control amount. For example, the steering control process may be a process in which the target steering angle α1* is the sum of the operation amount of feedback control in which the virtual steering angle α2 is the control amount and the operation amount of open-loop control in which the virtual steering angle α2 is the control amount.

[0061] The steering control process is not limited to a process in which the virtual steering angle α2 is the control variable and the operation amount of the control is the target steering angle α1*. The steering control process may be a process in which the hitch angle β is the control variable and the operation amount of the control is the target steering angle α1*. Here, the PU 82 may set the target value of the hitch angle β based on the target virtual steering angle α2* and the steering angle α1 according to the above formula (c5).

[0062] For example, ADASECU 80 may be configured to output a command value for the torque of motor 62. In this case, PU 82 may set the manipulated variable of feedback control, in which steering angle α1 is the control variable and target steering angle α1* is the target value of the control variable, as the command value for the torque of motor 62. Also, for example, PU 82 may set the sum of the manipulated variable of feedback control, in which steering angle α1 is the control variable, and the manipulated variable of open-loop control, in which steering angle α1 is the control variable, as the command value for the torque of motor 62.

[0063] "About vehicle speed dependent processing" For example, as described in the section "Regarding steering control processing," when ADASECU80 outputs a torque command value for motor 62, the vehicle speed-dependent processing may be processing that reduces the magnitude of the rate of change of the command value when vehicle speed V is low compared to when vehicle speed V is high.

[0064] For example, as described in the section "Regarding the steering control process," when the manipulated variable of feedback control, in which the steering angle α1 is the control variable, is set as the torque command value, it is desirable to use the output value of the process of S44 for the steering angle α1 as the feedback control variable.

[0065] 7 shows an example in which filtering is performed on both the hitch angle β and the steering angle α1, but this is not limitative. For example, filtering may be performed on only one of the hitch angle β and the steering angle α1.

[0066] "Sensors that detect the value of angular variables" The sensor for detecting the steering angle is not limited to the rotation angle sensor 68. The sensor for detecting the steering angle may be, for example, a steering sensor that detects the rotation angle of the steering shaft 54. Furthermore, the sensor for detecting the steering angle may be, for example, a linear position sensor that detects the amount of axial displacement of the rack shaft 56.

[0067] "About Actuators" The actuator does not necessarily have to be the steering actuator 60. The actuator may be, for example, a coaxial type actuator in which the rotation axis of the motor 62 is arranged parallel to the rack shaft 56.

[0068] "About the control device" The control device is not limited to one equipped with a PU 82 and a storage device 84 and executing software processing. For example, it may be equipped with a dedicated hardware circuit, such as an ASIC, that executes at least part of the processing executed in the above embodiment. That is, the control device may be a processing circuit having any of the following configurations (a) to (c): (a) A processing circuit equipped with a processing device that executes all of the above processing in accordance with a program and a program storage device, such as a storage device, that stores the program. (b) A processing circuit equipped with a processing device and program storage device that executes part of the above processing in accordance with a program, and a dedicated hardware circuit that executes the remaining processing. (c) A processing circuit equipped with a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software execution devices equipped with a processing device and a program storage device, and multiple dedicated hardware circuits.

[0069] "About Computers" The computer is not limited to the PU 82 mounted on the vehicle. For example, the processes of S10 to S22 and S30 shown in Fig. 3 may be executed by the PU 82, and the processes of S24 to S28 may be executed by the user's mobile terminal.

[0070] "About the operation panel" The operation unit is not limited to the steering wheel 52. For example, it may be a joystick.

[0071] "About the vehicle" The articulated vehicles are not limited to the vehicles shown in FIG.

Claims

1. A control device for a combination vehicle in which a tractor and a trailer are combined, The trailer includes an operating unit mechanically connected to steered wheels and an actuator that steers the steered wheels, configured to execute an acquisition process and a steering control process; the acquisition process is a process of acquiring a vehicle speed and an angle detection value, the detected angle value is a value detected by a sensor of an angle variable related to steering of the articulated vehicles, the steering control process is a process of operating the actuator based on the angle detection value as an input variable, and includes a vehicle speed dependent process, A control device for articulated vehicles, wherein the vehicle speed dependent processing is processing for reducing the responsiveness of the operation amount of the actuator to changes in the angle detection value when the vehicle speed is low compared to when the vehicle speed is high.

2. the steering control process is a process of operating the actuator in accordance with an operation amount for controlling a predetermined control amount related to the steering of the combination vehicle to a target value, 2. The control device for articulated vehicles according to claim 1, wherein the vehicle speed dependent processing is processing for limiting the upper limit of the magnitude of the rate of change of the operation amount of the actuator to a value that is smaller when the vehicle speed is low than when the vehicle speed is high.

3. the predetermined control amount is a virtual steering angle, the virtual steering angle is a variable indicating the traveling direction of a connection point between the trailer and the tractor, the steering control process is a process of operating the actuator in accordance with an operation amount of feedback control in which the virtual steering angle is a control amount, configured to execute a virtual steering angle calculation process, 3. The control device for articulated vehicles according to claim 2, wherein the virtual steering angle calculation process calculates the virtual steering angle based on the detected angle value as an input variable.

4. 3. The control device for articulated vehicles according to claim 2, wherein the manipulated variable is a target value for the steering angle of the steered wheels.

5. the steering control process includes filtering and operates the actuator in accordance with an output of the filtering, the filtering process is a process of removing high frequency components from the angle detection value, 2. The control device for articulated vehicles according to claim 1, wherein the vehicle speed dependent processing is processing in which the lower limit value of the frequency components to be removed by the filtering processing is set lower when the vehicle speed is low than when the vehicle speed is high.

6. The vehicle speed dependent processing includes a determination processing and a hold processing, the determination process is a process for determining whether the combination vehicle is in a stopped state, 2. The control device for articulated vehicles according to claim 1, wherein the hold process is a process of setting the detected angle value for determining the amount of operation of the actuator to a hold state when the vehicle is determined to be in the stopped state.

7. A method for controlling a combination vehicle in which a tractor and a trailer are coupled, comprising: The trailer includes an operating unit mechanically connected to steered wheels and an actuator that steers the steered wheels, Executing an acquisition process and executing a steering control process, the acquisition process is a process of acquiring a vehicle speed and an angle detection value, the detected angle value is a value detected by a sensor of an angle variable related to steering of the articulated vehicles, the steering control process is a process of operating the actuator based on the angle detection value as an input variable, and includes a vehicle speed dependent process, The method for controlling an articulated vehicle, wherein the vehicle speed dependent processing is processing for reducing the responsiveness of the operation amount of the actuator to changes in the angle detection value when the vehicle speed is low compared to when the vehicle speed is high.

8. A control program for a combination vehicle in which a tractor and a trailer are combined, The trailer includes an operating unit mechanically connected to steered wheels and an actuator that steers the steered wheels, An instruction to cause a computer to execute an acquisition process and a steering control process, the acquisition process is a process of acquiring a vehicle speed and an angle detection value, the detected angle value is a value detected by a sensor of an angle variable related to steering of the articulated vehicles, the steering control process is a process of operating the actuator based on the angle detection value as an input variable, and includes a vehicle speed dependent process, The vehicle speed dependent processing is a processing for reducing the responsiveness of the operation amount of the actuator to a change in the angle detection value when the vehicle speed is low compared to when the vehicle speed is high.

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