Control device, control method, and control program

Abstract

To prevent occurrence of meander and divergence while cancelling effects of a dead zone.SOLUTION: A control device (1) comprises: a steering angle calculation part (11) which calculates a steering angle of a vehicle as a control value for controlling a direction of travel of the vehicle; and a dead zone compensation part (12) which starts dead zone compensation in prescribed dead zone width when a steering angle changes from increasing to decreasing or from decreasing to increasing, and sets the dead zone width to zero until the steering angle next changes from decreasing to increasing or from increasing to decreasing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device and the like for autonomously driving a vehicle.

Background Art

[0002] Techniques for autonomously driving a work vehicle such as a tractor have been conventionally known. For example, Patent Document 1 below discloses an automatic driving system that controls the automatic driving of a tractor by an automatic driving control unit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although this is not limited to work vehicles, in vehicles that control the traveling direction by operating a steering wheel, there is a range where the wheels do not move and the steering angle does not change even when the steering wheel is operated. For this reason, when turning the vehicle by controlling the steering wheel as in Patent Document 1, the timing of turning may be delayed and the vehicle may travel in a zigzag manner. Among the range of control values of the steering angle input for steering wheel operation, which is considered to be the cause of such zigzag travel, the range where the angle of the wheels does not change is called the dead zone.

[0005] Dead zone compensation is known as a method for suppressing the influence of the dead zone. When performing dead zone compensation in the control of the steering angle, a predetermined dead zone width may be added to the control value of the steering angle. Thereby, the angle change of the wheels can be started at a predetermined timing, and it is possible to prevent the timing of turning from being delayed.

[0006] [[ID=4,2]] However, when a dead zone width is added, the amplitude of the rudder angle control value increases by the amount of the dead zone width added, which can cause meandering or divergence. One aspect of the present invention aims to provide a control device that can cancel the effect of the dead zone while preventing meandering or divergence caused by an excessively large amplitude of the rudder angle control value. [Means for solving the problem]

[0007] To solve the above problems, a control device according to one aspect of the present invention includes a steering angle calculation unit that calculates the steering angle of the vehicle as a control value for controlling the direction of travel of the vehicle, and a dead zone compensation unit that starts dead zone compensation with a predetermined dead zone width when the steering angle changes from an increase to a decrease or from a decrease to an increase, and then sets the dead zone width to zero before the steering angle changes from a decrease to an increase or from an increase to a decrease.

[0008] To solve the above problems, a control method according to one aspect of the present invention is a vehicle control method executed by one or more information processing devices, comprising: a steering angle calculation step of calculating the steering angle of the vehicle as a control value for controlling the direction of travel of the vehicle; and a dead zone compensation step of starting dead zone compensation with a predetermined dead zone width when the steering angle changes from increasing to decreasing or from decreasing to increasing, and then setting the dead zone width to zero before the steering angle changes from decreasing to increasing or from increasing to decreasing again. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to cancel the effects of the dead zone while preventing meandering and divergence caused by excessively large amplitudes in the control value of the rudder angle. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram showing an example of the main components of a control device according to one embodiment of the present invention. [Figure 2] This diagram illustrates the tractor's driving control using the control device described above. [Figure 3]This figure shows an example of dead zone compensation. [Figure 4] This flowchart shows an example of the processing performed by the dead zone compensation unit. [Figure 5] This flowchart shows an example of a process for adjusting the dead zone width. [Figure 6] This figure shows another example of dead zone compensation. [Figure 7] This figure shows yet another example of dead zone compensation. [Modes for carrying out the invention]

[0011] [Control device configuration] The configuration of the control device 1 according to this embodiment will be described with reference to Figure 1. Figure 1 is a block diagram showing an example of the main components of the control device 1. Figure 1 also shows a tractor TR1 as an example of a vehicle controlled by the control device 1. Although not shown in the diagram, the tractor TR1 is equipped with various devices necessary for the automatic operation of the tractor TR1, such as a position detection device for detecting the position of the tractor TR1 and a speed sensor for detecting the speed of the tractor TR1, and these devices are connected to the control device 1.

[0012] The control device 1 is a device that controls the operation of the tractor TR1. The control device 1 may be built into the tractor TR1 or attached to the tractor TR1 externally. As shown in the figure, the control device 1 includes a steering angle calculation unit 11 and a dead zone compensation unit 12, as well as a storage unit 13 that stores various data used by the control device 1.

[0013] The steering angle calculation unit 11 acquires position information of the tractor TR1 detected by a position detection device attached to the tractor TR1, and information indicating the azimuth angle that indicates the direction in front of the tractor TR1, and uses this information to calculate the steering angle of the tractor TR1. This steering angle is a control value that controls the direction of travel of the tractor TR1. The method of calculating the steering angle by the steering angle calculation unit 11 will be explained later in the "Driving Control" section.

[0014] The dead zone compensation unit 12 performs dead zone compensation on the steering angle output by the steering angle calculation unit 11 and outputs the steering angle after dead zone compensation as the command steering angle to the tractor TR1. More specifically, the dead zone compensation unit 12 starts dead zone compensation with a predetermined dead zone width when the steering angle output by the steering angle calculation unit 11 changes from increasing to decreasing or from decreasing to increasing. The dead zone compensation unit 12 then sets the dead zone width to zero until the steering angle output by the steering angle calculation unit 11 next changes from decreasing to increasing or from increasing to decreasing.

[0015] As described above, the control device 1 includes a steering angle calculation unit 11 that calculates the steering angle of the tractor TR1 as a control value for controlling the direction of travel of the tractor TR1, and a dead zone compensation unit 12 that starts dead zone compensation with a predetermined dead zone width when the steering angle changes from increasing to decreasing or from decreasing to increasing, and then sets the dead zone width to zero until the next time the steering angle changes from decreasing to increasing or from increasing to decreasing.

[0016] According to the above configuration, dead zone compensation is initiated when the steering angle changes from increasing to decreasing or decreasing to increasing, that is, when the direction of travel of the tractor TR1 changes, thus canceling the effect of the dead zone when the direction of travel of the tractor TR1 changes. Furthermore, according to the above configuration, the dead zone width is reduced to zero until the next time the steering angle changes from decreasing to increasing or increasing to decreasing, that is, until the next time the direction of travel of the tractor TR1 changes. Therefore, it is possible to prevent the amplitude of the steering angle control value from becoming too large, thereby preventing meandering and divergence. Here, "reducing the dead zone width to zero" means reducing the dead zone width to a sufficiently small value that prevents the amplitude of the steering angle control value from becoming too large, thereby preventing meandering and divergence. In other words, the category of "reducing the dead zone width to zero" includes not only configurations that completely reduce the dead zone width to zero, but also configurations that substantially reduce the dead zone width to zero. The same applies in the following explanation. In addition, the control device 1 is not limited to the tractor TR1, but can be used for the driving control of any vehicle. Therefore, "Tractor TR1" in the following explanation can be replaced with any "vehicle".

[0017] [Driving control] The running control of the tractor TR1 by the control device 1 will be described based on FIG. 2. FIG. 2 is a diagram for explaining the running control of the tractor TR1 by the control device 1. In FIG. 2, it is assumed that the tractor TR1 travels along a path connecting the target path start point WPs and the target path end point WPe. In FIG. 2, the positive direction of the Y-axis is north, and the positive direction of the X-axis is east. Also, in FIG. 2, the azimuth angle θp indicating the front direction of the tractor TR1 is represented based on the true north direction (Y-axis direction). That is, the azimuth angle θp when the tractor TR1 faces true north is 0°, and the azimuth angle θp when the tractor TR1 faces due east is 90°.

[0018] In the state shown in FIG. 2, the tractor TR1 to which the control device 1 is attached is at a position deviated from the path connecting the target path start point WPs and the target path end point WPe. The distance (lateral deviation) from this path to the center-of-gravity position P of the tractor TR1 is Δd. In FIG. 2, a point on the path separated from the center-of-gravity position P by a distance Δd is designated as M.

[0019] In this case, the control device 1 performs control to move the tractor TR1 onto the path based on the position information output by the position detection device attached to the tractor TR1. Specifically, the steering angle calculation unit 11 provided in the control device 1 sets a virtual target point T at a position that advances the above-mentioned path by a predetermined forward viewing distance L from the above-mentioned point M. Subsequently, the steering angle calculation unit 11 sets the angle formed by the line segment connecting the center-of-gravity position P and the virtual target point T and the reference direction (true north) as the target azimuth angle θt. Then, the steering angle calculation unit 11 calculates the difference between the set target azimuth angle θt and the azimuth angle θp of the tractor TR1 as the azimuth deviation Δθ (path azimuth deviation Δθc), and calculates the steering angle δ for turning the tractor TR1 by the calculated azimuth deviation Δθ.

[0020] For example, the rudder angle calculation unit 11 may calculate the rudder angle δ based on the azimuth element δa of the rudder angle, which is calculated by inputting the azimuth deviation Δθ into a proportional controller for azimuth, and the lateral element δs of the rudder angle, which is calculated by inputting the distance Δd into a proportional-integral controller for lateral direction. The above-mentioned proportional controller and proportional-integral controller may be provided as components of the rudder angle calculation unit 11.

[0021] The dead zone compensation unit 12 performs dead zone compensation on the steering angle δ calculated in this way, and outputs the steering angle after dead zone compensation as a command steering angle to the tractor TR1, causing the steering wheel of the tractor TR1 to rotate by the amount of the command steering angle. This process is repeated while continuously updating the center of gravity position P until Δd and the azimuth deviation Δθ become zero.

[0022] [Dead zone compensation] This section explains an example of dead zone compensation based on Figure 3. Figure 3 is a diagram illustrating an example of dead zone compensation. Figure 3 shows graphs G1 to G4. Graph G1 shows an example of the time-series change of the rudder angle calculated by the rudder angle calculation unit 11. In the example in Figure 3, the rudder angle calculated by the rudder angle calculation unit 11 increases and decreases periodically with a predetermined amplitude.

[0023] Furthermore, graph G2 shows the time-series change of the derivative of the azimuth deviation (Δθ in Figure 2), which indicates the forward direction of the tractor TR1, when the steering angle is changed as in graph G1. The derivative of the azimuth angle or azimuth deviation represents the rate of change in the direction of travel of the tractor TR1. The derivative of the azimuth deviation increases and decreases with the same period as the steering angle, but the graph of the steering angle G1 and the graph of the derivative of the azimuth deviation G2 are out of phase. That is, the derivative is zero when the steering angle is at its peak, and the steering angle is zero when the derivative is at its peak. This is because the steering angle peaks just before the direction in which the steering wheel of the tractor TR1 is turned reverses, and at this timing, the direction of travel of the tractor TR1 does not change.

[0024] Graph G3 shows a comparative example of dead zone compensation, and graph G4 shows an example of dead zone compensation by the dead zone compensation unit 12. In graphs G3 and G4, the dashed lines show the time-series change of the rudder angle calculated by the rudder angle calculation unit 11 (the same as shown in graph G1), and the solid lines show the time-series change of the rudder angle after dead zone compensation.

[0025] In the example shown in graph G3, dead zone compensation is performed by increasing or decreasing the rudder angle by a predetermined dead zone width just before the rudder angle calculated by the rudder angle calculation unit 11 reaches its peak. For example, near time t1, when the rudder angle peaks with a positive value, negative dead zone compensation is performed to decrease the rudder angle. Then, just before time t3, when the rudder angle peaks with a negative value, negative dead zone compensation is terminated, and immediately thereafter positive dead zone compensation is performed to increase the rudder angle.

[0026] By performing dead zone compensation in this manner, it is possible to suppress the effects of the dead zone. However, in the example shown in graph G3, the amplitude of the rudder angle after dead zone compensation is larger than before dead zone compensation by the amount of the dead zone width. Such an increase in amplitude is undesirable because it can cause meandering and divergence.

[0027] Therefore, the dead zone compensation unit 12 starts dead zone compensation with a predetermined dead zone width when the rudder angle changes from increasing to decreasing or from decreasing to increasing, and then sets the dead zone width to zero before the rudder angle changes from decreasing to increasing or from increasing to decreasing again.

[0028] For example, in the example shown in graph G4, the dead zone compensation unit 12 starts dead zone compensation from time t1, when the rudder angle changes from increasing to decreasing. Then, the dead zone compensation unit 12 starts decreasing the dead zone width from time t2, and reduces the dead zone width to zero by time t3, when the rudder angle changes from decreasing to increasing again after time t1. This prevents the amplitude from becoming too large and prevents meandering and divergence from occurring.

[0029] Furthermore, the dead zone compensation unit 12 may begin reducing the dead zone width when the differential value of the azimuth deviation, i.e., the rate of change in the direction of travel of the tractor TR1, reaches its peak. For example, in the example of graph G4, the differential value of the azimuth deviation peaks as a negative value just before time t2, and the dead zone compensation unit 12 begins reducing the dead zone width in response to this.

[0030] Here, it can be assumed that the effect of the dead zone immediately preceding the point where the change in the direction of travel of tractor TR1 reaches its peak has been canceled out. For example, in the example in graph G4, it can be assumed that the effect of the dead zone during the steering wheel reversal at time t1 has been canceled out around time t2.

[0031] Furthermore, once the rate of change in the direction of travel of the tractor TR1 reaches its peak, this rate of change begins to decrease. Therefore, with the above configuration, which starts to reduce the dead zone width when the rate of change in the direction of travel of the tractor TR1 reaches its peak, it becomes possible to achieve smooth steering while reliably canceling the effects of the dead zone.

[0032] [Adjusting the dead zone width] Furthermore, in the example shown in graph G4, the dead zone compensation unit 12 reduces the dead zone width in conjunction with the derivative of the azimuth deviation, i.e., the rate of change in the direction of travel of the tractor TR1. For example, during the period from time t2 to time t3, the rate of decrease in the dead zone width is reduced as the derivative of the azimuth deviation approaches zero.

[0033] Generally, when changing the direction of travel of a vehicle, the speed at which the direction of travel changes increases over time, reaches a peak, and then decreases over time until it becomes zero. Therefore, the above configuration, which reduces the dead zone width in conjunction with the speed at which the direction of travel of the tractor TR1 changes, can reduce the dead zone width in conjunction with the speed at which the direction of travel of the tractor TR1 decreases over time. This prevents abrupt changes in the steering angle after dead zone compensation, thereby achieving smooth steering.

[0034] When reducing the dead zone width in conjunction with the derivative of the azimuth deviation, the dead zone compensation unit 12 may adjust the dead zone width using, for example, the following formula (1).

[0035]

number

[0036] In the above formula (1), δ'deadzone is the adjusted dead zone width, and δdeadzone is the initial value of the dead zone width.

[0037]

number

[0038] This is the derivative of the azimuth deviation,

[0039]

number

[0040] This is the peak value of the derivative mentioned above.

[0041] When adjusting the dead zone width using the above formula (1), the adjusted dead zone width becomes half of the initial value when the derivative of the azimuth deviation is equal to the peak value. As the ratio of the derivative of the azimuth deviation to the peak value decreases, the adjusted dead zone width also decreases, and when the derivative of the azimuth deviation becomes zero, the adjusted dead zone width becomes zero. Therefore, by adjusting the dead zone width using formula (1), the dead zone compensation unit 12 can gradually reduce the dead zone width during the period from when the derivative of the azimuth deviation reaches its peak until it becomes zero, that is, it can reduce the dead zone width in conjunction with the derivative of the azimuth deviation.

[0042] [Adjustment of dead zone width when the differential value of azimuth deviation is small] Incidentally, when the derivative of the azimuth deviation remains small, it can be said that the change in steering angle remains small. For example, when tractor TR1 is moving in a straight line along its path, both the change in steering angle and the derivative of the azimuth deviation will be small. In such a state, if dead zone compensation is performed with the same dead zone width as during turning, it is conceivable that the commanded steering angle will become oscillating, which may impair straight-line driving.

[0043] Therefore, for example, the dead zone compensation unit 12 may adjust the dead zone width using the following formula (2) when the differential value of the azimuth deviation is less than or equal to a predetermined threshold φ.

[0044]

number

[0045] The dead zone compensation unit 12 can adjust the dead zone width using the above formula (2) to reduce the dead zone width at the start of dead zone compensation when the derivative of the azimuth deviation is small. Furthermore, when adjusting the dead zone width using the above formula (2), the dead zone width can be gradually reduced as the derivative of the azimuth deviation decreases.

[0046] Thus, the dead zone compensation unit 12 may determine the dead zone width at the start of dead zone compensation according to the rate of change in the direction of travel of the tractor TR1. As described above, if dead zone compensation with a large dead zone width is performed when the direction of travel of the tractor TR1 has not changed significantly, meandering may occur, but with this configuration, it is possible to avoid dead zone compensation being performed with an unnecessarily large dead zone width.

[0047] The dead zone compensation unit 12 may, after determining the dead zone width at the start of dead zone compensation using formula (2) above, reduce the dead zone width by other means. For example, the dead zone compensation unit 12 may, after determining the dead zone width using formula (2) above, reduce the dead zone width using formula (1) above, or reduce the dead zone width by a method such as that shown in Figure 6 or Figure 7, which will be described later.

[0048] [Processing flow] The processes performed by the dead zone compensation unit 12 will be explained with reference to Figure 4. Figure 4 is a flowchart showing an example of the processes performed by the dead zone compensation unit 12. During the period in which the processes in Figure 4 and Figure 5 (described later) are performed, the steering angle calculation unit 11 repeatedly performs a process to calculate the steering angle as a control value for controlling the direction of travel of the tractor TR1 (steering angle calculation step) at predetermined intervals, and the calculated steering angle is stored in the storage unit 13.

[0049] In S1, the dead zone compensation unit 12 determines whether the input has increased, that is, whether the latest rudder angle calculated by the rudder angle calculation unit 11 has increased compared to the rudder angle calculated immediately before. If the result in S1 is YES, the process proceeds to S2; if the result in S1 is NO, the process proceeds to S3.

[0050] In S2, the dead zone compensation unit 12 sets a parameter representing the increase or decrease in input to 1. In other words, a parameter representing the increase or decrease in input being 1 indicates that the input to the dead zone compensation unit 12 is increasing. After S2, the process proceeds to S21-S26.

[0051] On the other hand, in S3, the dead zone compensation unit 12 sets the parameter representing the increase or decrease in input to -1. In other words, a parameter representing the increase or decrease in input being -1 indicates that the input to the dead zone compensation unit 12 is decreasing. After S3, the process proceeds to S31 to S36.

[0052] In S21, the dead zone compensation unit 12 determines whether the input has increased. If the process transitions in the order of S1, S2, and S21, the result of the determination in S21 is YES. If the process transitions from S23 or S36 (described later) to S21, it is determined whether the latest rudder angle calculated by the rudder angle calculation unit 11 has increased compared to the rudder angle calculated immediately before. If the result in S21 is YES, the process proceeds to S22; if the result in S21 is NO, the process proceeds to S23.

[0053] In S22, the dead zone compensation unit 12 updates the peak value of the rudder angle calculated by the rudder angle calculation unit 11. When the S22 process is executed for the first time, the peak value is recorded in the storage unit 13, and when the S22 process is executed for the second time or later, the peak value recorded in the storage unit 13 is updated. After this, the process returns to S21.

[0054] In S23, the dead zone compensation unit 12 determines whether the difference between the input, i.e., the latest rudder angle calculated by the rudder angle calculation unit 11, and the peak value recorded or updated in S22 is less than or equal to a threshold. This threshold is set to prevent dead zone compensation from starting or ending due to minute fluctuations in the rudder angle calculated by the rudder angle calculation unit 11. If the result in S23 is YES, the process returns to S21; if the result in S23 is NO, the process proceeds to S24.

[0055] Furthermore, when the parameter representing increase or decrease is 1, a decrease in input (NO in S21) and the difference between the peak value and the input becoming greater than the threshold (NO in S23) means that the rudder angle has changed from increasing to decreasing. In other words, S21 and S23 determine whether or not the rudder angle has changed from increasing to decreasing.

[0056] In S24, the dead zone compensation unit 12 determines whether or not positive dead zone compensation is being performed. Positive dead zone compensation means adding a predetermined dead zone width to the rudder angle calculated by the rudder angle calculation unit 11. If the result in S24 is YES, the process proceeds to S25; if the result in S24 is NO, the process proceeds to S26.

[0057] In S25, the dead zone compensation unit 12 completes the positive dead zone compensation and returns to the process in S21. Meanwhile, in S26, the dead zone compensation unit 12 updates the parameter representing the increase or decrease in input to a value of -1, indicating that the input is decreasing, and starts the process of negative dead zone compensation, that is, subtracting a predetermined dead zone width from the rudder angle calculated by the rudder angle calculation unit 11. After this, the process proceeds to S31.

[0058] In S31, the dead zone compensation unit 12 determines whether the input has decreased. If the process transitions in the order of S1, S3, and S31, the result of the determination in S31 is YES if the change in input is not zero. If the process transitions from S26 or S33 to S31, it is determined whether the latest rudder angle calculated by the rudder angle calculation unit 11 has decreased compared to the rudder angle calculated immediately before. If the result in S31 is YES, the process proceeds to S32; if the result in S31 is NO, the process proceeds to S33.

[0059] In S32, the dead zone compensation unit 12 updates the input peak value, i.e., the peak value of the rudder angle calculated by the rudder angle calculation unit 11. When the S32 process is executed for the first time, the peak value is recorded in the storage unit 13, and when the S32 process is executed for the second time or later, the peak value recorded in the storage unit 13 is updated. After this, the process returns to S31.

[0060] In S33, the dead zone compensation unit 12 determines whether the difference between the input, i.e., the latest rudder angle calculated by the rudder angle calculation unit 11, and the peak value recorded or updated in S32 is less than or equal to a threshold. If the result in S33 is YES, the process returns to S31; if the result in S33 is NO, the process proceeds to S34.

[0061] Furthermore, when the parameter representing increase or decrease is -1, an increase in input (NO in S31) and the difference between the peak value and the input becomes greater than the threshold (NO in S33) means that the rudder angle has changed from decreasing to increasing. In other words, S31 and S33 determine whether or not the rudder angle has changed from decreasing to increasing.

[0062] In S34, the dead zone compensation unit 12 determines whether or not negative dead zone compensation is being performed. Negative dead zone compensation means subtracting a predetermined dead zone width from the rudder angle calculated by the rudder angle calculation unit 11. If the result in S34 is YES, the process proceeds to S35; if the result in S34 is NO, the process proceeds to S36.

[0063] In S35, the dead zone compensation unit 12 finishes negative dead zone compensation and returns to the process in S31. Meanwhile, in S36, the dead zone compensation unit 12 updates the parameter representing the increase or decrease in input to a value of 1, indicating that the input is increasing, and starts positive dead zone compensation, that is, the process of adding a predetermined dead zone width to the rudder angle calculated by the rudder angle calculation unit 11. This post-processing returns to S21.

[0064] [Processing flow: Adjustment of dead zone width] The process performed by the dead zone compensation unit 12 to adjust the dead zone width will be explained with reference to Figure 5. Figure 5 is a flowchart showing an example of the process for adjusting the dead zone width. The process in Figure 5 is performed in parallel with the process in Figure 4.

[0065] In S5, the dead zone compensation unit 12 smooths the derivative of the azimuth angle (θp in Figure 2) indicating the forward direction of the tractor TR1, or the derivative of the azimuth deviation (Δθ in Figure 2). Smoothing is performed to suppress the effects of noise and other factors and to appropriately grasp the pattern of variation in the derivative value. The content of the smoothing process is not particularly limited; for example, the dead zone compensation unit 12 may use the average of a predetermined number of recent derivative values ​​(for example, the derivative values ​​of the five most recent points) as the derivative value after smoothing. The process in S5 is performed each time the latest information indicating the azimuth angle is acquired, and the smoothed derivative value is stored in the storage unit 13.

[0066] In S6, the dead zone compensation unit 12 determines whether or not dead zone compensation is being performed. The process in S6 is repeated periodically until it is determined to be YES, and if it is determined to be YES in S6, the process proceeds to S7. Note that the process in Figure 5 may be performed immediately after the process in S26 or S36 in Figure 4, in which case the process in S6 may be omitted.

[0067] In S7, the dead zone compensation unit 12 determines whether or not dead zone compensation in the positive direction is being performed. If it is determined to be YES in S7, the process proceeds to S81; if it is determined to be NO in S7, the process proceeds to S91. The following steps S81-S85 and S91-S95 are dead zone compensation steps that reduce the dead zone width to zero before the next time the rudder angle changes from decreasing to increasing or from increasing to decreasing, in dead zone compensation initiated in S26 or S36 in Figure 4, triggered by the determination that the rudder angle has changed from increasing to decreasing or from decreasing to increasing.

[0068] In S81, the dead zone compensation unit 12 determines whether the differential value of the azimuth deviation has increased. This determination is made by referring to the time-series differential value stored in the memory unit 13. If the result in S81 is YES, the process proceeds to S82; if the result in S81 is NO, the process proceeds to S83.

[0069] In S82, the dead zone compensation unit 12 updates the peak value of the derivative of the azimuth deviation. When the S82 process is executed for the first time, the peak value is recorded in the storage unit 13, and when the S82 process is executed for the second time or later, the peak value recorded in the storage unit 13 is updated. After this, the process returns to S81.

[0070] In S83, the dead zone compensation unit 12 determines whether the derivative of the azimuth deviation (smoothed in S5) is zero or less. If the derivative of the azimuth deviation becomes zero or less during the execution of dead zone compensation in the positive direction, it means that the rudder angle has changed from increasing to decreasing. In other words, S83 determines whether the rudder angle has changed from increasing to decreasing. If the result in S83 is YES, the process proceeds to S84; if the result in S83 is NO, the process proceeds to S85. In S85, the dead zone compensation unit 12 sets the dead zone width to zero and returns to the process in S7.

[0071] On the other hand, in S84, the dead zone compensation unit 12 adjusts the dead zone width. For example, the dead zone compensation unit 12 may adjust the dead zone width using the following formula (3). Note that the derivative value in formula (3) is the derivative value of the azimuth deviation (smoothed in S5), and the peak value is the latest peak value updated in S82, that is, the maximum value of the above derivative value.

[0072] δ'deadzone = δdeadzone × (derivative value) / (peak value) ... (3) The dead zone compensation unit 12 may also adjust the dead zone width using the above formula (1) or (2). After adjusting the dead zone width, the process returns to S81.

[0073] In S91, the dead zone compensation unit 12 determines whether the differential value of the azimuth deviation has decreased. This determination is made by referring to the time-series differential value stored in the memory unit 13. If the result in S91 is YES, the process proceeds to S92; if the result in S91 is NO, the process proceeds to S93.

[0074] In S92, the dead zone compensation unit 12 updates the peak value of the derivative of the azimuth deviation. When the S92 process is executed for the first time, the peak value is recorded in the memory unit 13, and when the S92 process is executed for the second time or later, the peak value recorded in the memory unit 13 is updated. After this, the process returns to S91.

[0075] In S93, the dead zone compensation unit 12 determines whether the derivative of the azimuth deviation (smoothed in S5) is greater than or equal to zero. Note that if the derivative of the azimuth deviation becomes greater than or equal to zero during the execution of dead zone compensation in the negative direction, it means that the rudder angle has changed from decreasing to increasing. In other words, S93 determines whether or not the rudder angle has changed from decreasing to increasing. If the result in S93 is YES, the process proceeds to S94; if the result in S93 is NO, the process proceeds to S95.

[0076] In S95, the dead zone compensation unit 12 sets the dead zone width to zero and returns to the process in S7. On the other hand, in S94, the dead zone compensation unit 12 adjusts the dead zone width. The same method as in S84 can be applied for adjustment. After adjusting the dead zone width, the process returns to the process in S91.

[0077] As described above, the vehicle control method executed by the control device 1 includes a steering angle calculation step of calculating the steering angle of the tractor TR1 as a control value for controlling the direction of travel of the tractor TR1, and a dead zone compensation step (S81-S85 or S91-S95 in Figure 5) in which dead zone compensation is started with a predetermined dead zone width when the steering angle changes from increasing to decreasing or from decreasing to increasing (S26 or S36 in Figure 4), and then the dead zone width is reduced to zero until the steering angle changes from decreasing to increasing or from increasing to decreasing again. With this configuration, it is possible to prevent the amplitude of the steering angle control value from becoming too large and to prevent meandering and divergence.

[0078] [Other examples of dead zone compensation] Other examples of dead zone compensation are explained based on Figure 6. Figure 6 shows other examples of dead zone compensation. Figure 6 shows graphs G1, G2, and G5. Graphs G1 and G2 are the same as those shown in Figure 3 and show the time series change of the rudder angle calculated by the rudder angle calculation unit 11 and the derivative of the bearing deviation, respectively.

[0079] Graph G5 shows an example of dead zone compensation performed by the dead zone compensation unit 12. In Graph G5, the dashed line shows the time series change of the rudder angle calculated by the rudder angle calculation unit 11 (the same as shown in Graph G1), and the solid line shows the time series change of the rudder angle after dead zone compensation.

[0080] In the example of graph G5, dead zone compensation is performed only during a predetermined period immediately after the rudder angle changes from increasing to decreasing or from decreasing to increasing. Specifically, in the example of graph G5, similar to the example of graph G4 in Figure 3, dead zone compensation starts from time t1 when the rudder angle changes from increasing to decreasing, but the timing of ending the dead zone compensation is different from the example in Figure 3. That is, in the example of graph G5, the dead zone compensation unit 12 starts to decrease the dead zone width from time t2' and sets the dead zone width to zero at time t3'.

[0081] The dead zone compensation unit 12 can determine the time t2' at which it begins to reduce the dead zone width based on at least one of the timing at which dead zone compensation was initiated and the rudder angle at which dead zone compensation was initiated. For example, the dead zone compensation unit 12 may set the time t2' at which it begins to reduce the dead zone width to a predetermined time after the time t1 at which dead zone compensation was initiated. Alternatively, the dead zone compensation unit 12 may set the time t2' at which it begins to reduce the dead zone width to a predetermined time after the rudder angle has changed by a predetermined angle since the start of dead zone compensation.

[0082] Thus, the dead zone compensation unit 12 may determine the timing at which it begins to reduce the dead zone width based on at least one of the timing at which dead zone compensation is initiated and the rudder angle at the time dead zone compensation is initiated.

[0083] Of the above configurations, the configuration in which the timing for starting to reduce the dead zone width is determined based on the timing when dead zone compensation is initiated makes it possible to cancel the effects of the dead zone and to set the dead zone width to zero before the amplitude of the rudder angle control value becomes too large. Similarly, when the timing for starting to reduce the dead zone width is determined based on the rudder angle at the time dead zone compensation is initiated, it also makes it possible to cancel the effects of the dead zone and to set the dead zone width to zero before the amplitude of the rudder angle control value becomes too large.

[0084] The method for reducing the dead zone width after time t2' is arbitrary and is not limited to the example in Figure 6. For example, the dead zone compensation unit 12 may reduce the dead zone width in conjunction with the change in the derivative of the azimuth deviation, or in other words, in conjunction with the rate of change in the direction of travel of the tractor TR1. This prevents abrupt changes in the steering angle after time t2' and enables smooth steering.

[0085] [Further examples of dead zone compensation] Further examples of dead zone compensation are illustrated based on Figure 7. Figure 7 shows further examples of dead zone compensation. Figure 7 shows graphs G1, G2, and G6. Graphs G1 and G2 are the same as those shown in Figure 3 and show the time-series changes of the rudder angle calculated by the rudder angle calculation unit 11 and the derivative of the bearing deviation, respectively.

[0086] Graph G6 shows an example of dead zone compensation performed by the dead zone compensation unit 12. In Graph G6, the dashed line shows the time-series change of the rudder angle calculated by the rudder angle calculation unit 11 (the same as shown in Graph G1), and the solid line shows the time-series change of the rudder angle after dead zone compensation.

[0087] In the example of graph G6, dead zone compensation is started when the rudder angle reaches its peak and terminated before the rudder angle reaches its next peak. Specifically, in the example of graph G6, dead zone compensation is started from time t1 when the rudder angle changes from increasing to decreasing, similar to the example of graph G4 in Figure 3, but the timing of the termination of dead zone compensation is different from the example in Figure 3. That is, in the example of graph G6, the dead zone compensation unit 12 starts to decrease the dead zone width from time t2" and sets the dead zone width to zero at time t3"."

[0088] The dead zone compensation unit 12 may determine the time t2'' at which it begins to reduce the dead zone width based on the time t4'' at which the differential value of the azimuth deviation reaches its peak. Note that time t4 is also the time at which the rate of change in the direction of travel of the tractor TR1 reaches its peak.

[0089] Specifically, the dead zone compensation unit 12 should determine the time t2'' and the time t3'' at which the dead zone width is reduced to zero so that dead zone compensation ends before the rudder angle reaches its peak. For example, the dead zone compensation unit 12 may set the time t2'' at a predetermined time after time t4 or at which time t2'' occurs when the rudder angle has changed by a predetermined angle from time t4 as the time to start reducing the dead zone width, and set the period for reducing the dead zone width to zero within a range where the time t3'' at which the dead zone width is reduced to zero does not exceed the peak of the rudder angle.

[0090] As described above, the dead zone compensation unit 12 may set the dead zone width to zero for a predetermined period starting from the point when the change speed in the direction of travel of the tractor TR1 reaches its peak. With this configuration, the effect of the dead zone immediately preceding the point when the change speed in the direction of travel of the tractor TR1 reaches its peak is canceled, and the dead zone width is set to zero for a predetermined period starting from the point just before the change speed in the direction of travel of the tractor TR1 begins to decrease. Therefore, the effect of the dead zone can be canceled, and the dead zone width can be set to zero before the amplitude of the steering angle control value becomes too large.

[0091] The method for reducing the dead zone width after time t2'' is arbitrary and is not limited to the example in Figure 7. For example, the dead zone compensation unit 12 may reduce the dead zone width in conjunction with the change in the derivative of the azimuth deviation, or in other words, in conjunction with the rate of change in the direction of travel of the tractor TR1. This prevents abrupt changes in the steering angle after time t2'' and enables smooth steering.

[0092] [Variation] The entity executing each process described in the above-described embodiment is arbitrary and not limited to the examples given. In other words, the functions of the control device 1 can be realized by multiple information processing devices (which can also be called processors) that can communicate with each other. For example, each process described in the flowcharts of Figures 4 and 5 can be assigned to multiple information processing devices. In other words, the entity executing the control method in the above-described embodiment may be one information processing device (for example, the control device 1) or multiple information processing devices.

[0093] [Reference example] A control device according to one example includes a steering angle calculation unit that calculates the steering angle of the vehicle as a control value for controlling the direction of travel of the vehicle, and a dead zone compensation unit that performs dead zone compensation for the steering angle and determines the dead zone width at the start of the dead zone compensation according to the rate of change in the direction of travel of the vehicle.

[0094] If dead zone compensation with a large dead zone width is performed when the direction of travel of the vehicle has not changed significantly, it may actually cause meandering or other problems. However, with the above configuration, it is possible to avoid dead zone compensation being performed with an unnecessarily large dead zone width.

[0095] The steering angle calculation unit described above can be the same as the steering angle calculation unit 11 described above. In addition, the dead zone compensation unit may, for example, determine the dead zone width using the formula (2) described above when the change in the vehicle's direction of travel is less than or equal to a predetermined threshold φ, and determine the dead zone width using the formula (1) described above when the change in speed is greater than the predetermined threshold φ.

[0096] Furthermore, the dead zone compensation unit provided in the control device according to this reference example may or may not have the same functions as the dead zone compensation unit 12 described above, namely, the function of starting dead zone compensation with a predetermined dead zone width when the rudder angle changes from an increase to a decrease or from a decrease to an increase, and the function of making the dead zone width zero before the rudder angle changes from a decrease to an increase or from an increase to a decrease again.

[0097] [Examples of implementation using software] The function of the control device 1 is a program that causes the computer to function as the device, and can be realized by a control program that causes the computer to function as each control block of the control device 1 (particularly the rudder angle calculation unit 11 and the dead zone compensation unit 12).

[0098] In this case, the control device 1 includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., memory) as hardware for executing the control program. By executing the control program using this control device and storage device, each of the functions described in each of the embodiments above is realized.

[0099] The control program described above may be recorded on one or more computer-readable recording media, rather than temporarily. The control device 1 may or may not have such recording media. In the latter case, the control program may be supplied to the control device 1 via any wired or wireless transmission medium.

[0100] Furthermore, some or all of the functions of each of the above control blocks can also be realized by logic circuits. For example, an integrated circuit in which logic circuits functioning as each of the above control blocks are formed is also included in the scope of the present invention. In addition, it is also possible to realize the functions of each of the above control blocks by, for example, a quantum computer.

[0101] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0102] 1 Control device 11. Rudder angle calculation unit 12 Dead Zone Compensation Section

Claims

1. A steering angle calculation unit calculates the steering angle of the vehicle as a control value for controlling the direction of travel of the vehicle, The system includes a dead zone compensation unit that, when it is determined that the steering angle has changed from increasing to decreasing or from decreasing to increasing, starts dead zone compensation with a predetermined dead zone width, and then, when it is determined that the steering angle has changed from decreasing to increasing or from increasing to decreasing, sets the dead zone width to zero. The dead zone compensation is performed by adding the predetermined dead zone width to the control value of the steering angle of the vehicle, in a control device.

2. A steering angle calculation unit that calculates the steering angle of a vehicle as a control value for controlling the direction of travel of the vehicle, The system includes a dead zone compensation unit that starts dead zone compensation with a predetermined dead zone width when the rudder angle changes from increasing to decreasing or from decreasing to increasing, and then sets the dead zone width to zero when the rudder angle changes from decreasing to increasing or from increasing to decreasing again. The dead zone compensation unit is a control device that reduces the dead zone width in conjunction with the changing speed in the direction of travel of the vehicle.

3. The control device according to claim 2, wherein the dead zone compensation unit begins to reduce the dead zone width when the change in the direction of travel of the vehicle reaches its peak.

4. The control device according to claim 1 or 2, wherein the dead zone compensation unit determines the timing for starting to reduce the dead zone width based on at least one of the timing at which the dead zone compensation is started and the rudder angle at the time the dead zone compensation is started.

5. A steering angle calculation unit that calculates the steering angle of a vehicle as a control value for controlling the direction of travel of the vehicle, The system includes a dead zone compensation unit that starts dead zone compensation with a predetermined dead zone width when the rudder angle changes from increasing to decreasing or from decreasing to increasing, and then sets the dead zone width to zero when the rudder angle changes from decreasing to increasing or from increasing to decreasing again. The dead zone compensation unit is a control device that reduces the dead zone width to zero over a predetermined period of time from the point in time when the change in the direction of travel speed of the vehicle reaches its peak.

6. A steering angle calculation unit that calculates the steering angle of a vehicle as a control value for controlling the direction of travel of the vehicle, The system includes a dead zone compensation unit that starts dead zone compensation with a predetermined dead zone width when the rudder angle changes from increasing to decreasing or from decreasing to increasing, and then sets the dead zone width to zero when the rudder angle changes from decreasing to increasing or from increasing to decreasing again. The dead zone compensation unit is a control device that determines the dead zone width at the start of the dead zone compensation according to the speed of change in the direction of travel of the vehicle.

7. A steering angle calculation unit calculates the steering angle of the vehicle as a control value for controlling the direction of travel of the vehicle, A control device comprising: a dead zone compensation unit that performs dead zone compensation for the steering angle, and which determines the dead zone width at the start of the dead zone compensation according to the speed of change in the direction of travel of the vehicle.

8. A vehicle control method performed by one or more information processing devices, A steering angle calculation step, which calculates the steering angle of the vehicle as a control value for controlling the direction of travel of the vehicle, The system includes a dead zone compensation step in which, when it is determined that the steering angle has changed from an increase to a decrease or from a decrease to an increase, dead zone compensation is started with a predetermined dead zone width, and when it is then determined that the steering angle has changed from a decrease to an increase or from an increase to a decrease, the dead zone compensation step is set to zero. The dead zone compensation is performed by adding the predetermined dead zone width to the control value of the steering angle of the vehicle, in a vehicle control method.

9. A control program for causing a computer to function as the control device described in claim 1, wherein the computer functions as the rudder angle calculation unit and the dead zone compensation unit.

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