JP2020011537A - Vehicle and automatic steering gear - Google Patents

Abstract

To provide a technique for precisely moving a vehicle to a target position with high precision in automatic drive.SOLUTION: A vehicle 1 includes a wheel 3 having tire wheels 4a, 5a, 6a and 7a and viscoelastic bodies (a tire) 4b, 5b, 6b and 7b provided around the tire wheels 4a, 5a, 6a and 7a and in contact with a road surface. The vehicle 1 autonomously controls tire wheel steering angles θ of the tire wheels 4a, 5a, 6a and 7a to run on a predetermined route. The predetermined route includes curves at least partially and when the vehicle runs on the predetermined route at a first speed, the tire wheel steering angle takes a first steering angle pattern. When the vehicle runs on the predetermined route at a second speed lower than the first speed, the tire wheel steering angle takes a second rudder angle pattern. At a predetermined point on the predetermined route, the tire wheel rudder angle in the second steering angle pattern is larger than the tire wheel steering angle in the first rudder angle pattern.SELECTED DRAWING: Figure 7

Description

  The present disclosure relates to a vehicle and an automatic steering device.

  Conventionally, a target trajectory is created in real time while estimating the vehicle position with respect to a target position (target parking position, etc.) set on the screen, and the vehicle is guided to the target position by controlling the steering angle. A known traveling control device is known.

  Patent Document 1 discloses an automatic guidance system for a vehicle that guides a vehicle to a target position by controlling a steering angle while estimating a vehicle position based on at least a steering angle value. The turning curvature g (Str (p)) estimated on the basis of the change in the moving distance of the vehicle dp is added to the turning curvature g (Str (p)) to calculate the turning curvature y (p) in which the turning curvature delay caused by the tire deformation is compensated. .

JP-A-2015-041276

  Patent Literature 1 aims to estimate a vehicle position with high accuracy by adding a smoothness to a change in a vehicle moving distance to a turning curvature estimated based on a steering angle value. However, Patent Literature 1 and the like do not consider in detail various factors of the delay in the change of the tire angle due to the steering of the steering wheel. In particular, the speed changes during the actual movement of the vehicle, but the conventional technology does not pay attention to such a change in speed, so that there is a limit to the accuracy of movement to the target position.

  The present disclosure relates to a technique for accurately moving a vehicle to a target position in automatic driving.

  The vehicle of the present disclosure includes a wheel including a tire wheel and a viscoelastic body disposed around the tire wheel and in contact with a road surface, autonomously controlling a tire wheel steering angle of the tire wheel, and A vehicle capable of traveling on a route, wherein the predetermined route includes a curve at least in part, and when traveling on the predetermined route at a first speed, the tire wheel steering angle becomes a first steering angle. When the vehicle travels on the predetermined route at a second speed lower than the first speed, the tire wheel steering angle is a second steering angle pattern, and at a predetermined point on the predetermined route. The tire wheel steering angle of the second steering angle pattern is larger than the tire wheel steering angle of the first steering angle pattern.

  The automatic steering device of the present disclosure includes a wheel including a tire wheel and a viscoelastic body disposed around the tire wheel and in contact with a road surface, and autonomously controls a tire wheel steering angle of the tire wheel. An automatic steering device that can be mounted on a vehicle that can travel on a predetermined route, wherein the predetermined route includes a curve at least in part, and when the predetermined route runs at a first speed, The tire wheel steering angle is a first steering angle pattern. When the vehicle travels on the predetermined route at a second speed lower than the first speed, the tire wheel steering angle is a second steering angle pattern. At a predetermined point on the predetermined route, the tire wheel steering angle of the second steering angle pattern is larger than the tire wheel steering angle of the first steering angle pattern.

  According to the present disclosure, since the tire wheel steering angle is controlled in consideration of the speed of the vehicle, the vehicle can be accurately moved to the target position.

1A is a side view illustrating an example of a vehicle according to an embodiment, and FIG. 1B is a schematic diagram illustrating wheel positions. 1 is a system configuration diagram illustrating an embodiment of a vehicle parking assist device (automatic steering device) according to the present disclosure. FIG. 3 is a block diagram illustrating functions of a parking assist ECU. It is a figure which shows an example of the touch panel for target parking position setting on a display monitor. It is a schematic diagram which shows automatic parking of a vehicle. It is a schematic diagram which shows the position of the wheel in a vehicle, (a) The figure which shows the position of the wheel at the time of straight running, (b) The figure which shows the position of the wheel at the time of curve running. FIG. 3 is a schematic diagram showing straight running and curve running of the vehicle, and graphs showing changes in the tire wheel steering angle during low speed running and high speed running corresponding to the schematic diagram. It is a graph which shows a delay time and its dead time. (A) It is a graph which shows the primary delay in the delay time at the time of advance, (b) It is a graph which shows the primary delay in the delay time at the time of reverse.

  Hereinafter, an embodiment (hereinafter, referred to as “the present embodiment”) that specifically discloses a vehicle and an automatic steering device according to the present disclosure will be described in detail with reference to the drawings as appropriate. However, an unnecessary detailed description may be omitted. For example, a detailed description of a well-known item or a redundant description of substantially the same configuration may be omitted. This is to prevent the following description from being unnecessarily redundant and to facilitate understanding by those skilled in the art. The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the claimed subject matter.

  Hereinafter, a preferred embodiment for carrying out the present disclosure will be described in detail with reference to the drawings.

  As shown in FIG. 1, a vehicle 1 of the embodiment includes a vehicle body 2 and wheels 3 that support the vehicle body 2 and move the vehicle 1 in a predetermined direction. The wheels 3 are four wheels in the embodiment, and include a left front wheel 4, a right front wheel 5, a left rear wheel 6, and a right rear wheel 7. The left front wheel 4 includes a tire wheel 4a and a tire 4b arranged around the tire wheel 4a. The right front wheel 5 includes a tire wheel 5a and a tire 5b arranged around the tire wheel 5a. The left rear wheel 6 includes a tire wheel 6a and a tire 6b arranged around the tire wheel 6a. The right rear wheel 7 includes a tire wheel 7a and a tire 7b arranged around the tire wheel 7a.

  The tire wheels 4a, 5a, 6a, and 7a are connected to a steering mechanism or a power source (an internal combustion engine and / or an electric motor). For example, at least part of the tire wheels is made of metal, but the material is not particularly limited. The tires 4b, 5b, 6b, and 7b are made of a viscoelastic body that is in contact with the road surface, and for example, at least a part is made of rubber, but the material is not particularly limited. Generally, the viscoelasticity of the tire wheels 4a, 5a, 6a, 7a is larger than the viscoelasticity of the viscoelastic body constituting the tires 4b, 5b, 6b, 7b.

  FIG. 2 is a system configuration diagram illustrating an embodiment of a parking assist device (automatic steering device) 10 of the vehicle 1 according to the present disclosure. As shown in FIG. 2, the vehicle parking assist device 10 is mainly configured with an electronic control unit 12 (hereinafter, referred to as “parking assist ECU 12”). The parking assist ECU 12 is configured as a microcomputer including a CPU, a ROM, a RAM, and the like connected to each other via a bus (not shown). The ROM stores a program to be executed by the CPU and predetermined values of the vehicle (such as a wheelbase length L).

  The parking assist ECU 12 detects a steering angle sensor 16 for detecting a steering angle of a steering wheel (not shown) via an appropriate bus such as a CAN (Controller Area Network) or a high-speed communication bus, and detects a vehicle speed. Vehicle speed sensor 18 is connected. The vehicle speed sensor 18 may be a wheel speed sensor that is provided for each wheel and generates a pulse signal at a cycle according to the wheel speed.

  A reverse shift switch 50 and a parking switch 52 are connected to the parking assist ECU 12. The reverse shift switch 50 outputs an ON signal when the transmission lever is operated to the reverse position, and maintains the OFF state otherwise. Further, the parking switch 52 is provided in the vehicle compartment, and can be operated by a user. The parking switch 52 is normally kept off and is turned on by a user operation. The parking assist ECU 12 determines whether or not the vehicle is in a reverse state based on the output signal of the reverse shift switch 50, and determines whether or not the user needs parking assistance based on the output signal of the parking switch 52. Determine.

  A back monitor camera 20 disposed in the center of the bumper at the rear of the vehicle and a display monitor 22 provided in the vehicle compartment are connected to the parking assist ECU 12. The back monitor camera 20 is a CCD camera that captures an area behind the vehicle at a predetermined viewing angle, and supplies a video signal representing a captured image to the parking assist ECU 12. The parking assist ECU 12 displays the image captured by the back monitor camera 20 on the display monitor 22 when both the reverse shift switch 50 and the parking switch 52 are on. At this time, the target parking position setting touch panel is displayed on the display monitor 22 together with the captured image, for example, as shown in FIG. Using the target parking position setting touch panel, the user performs an operation on the display monitor 22 to match the target parking frame (indicated by a broken line in the figure) with the actual parking frame (indicated by a solid line in the figure) on the captured image. When the position of the target parking frame is determined on the captured image, the parking assist ECU 12 recognizes a position corresponding to the parking target frame on the captured image as a target parking position.

  A steering control ECU 30 is connected to the parking assist ECU 12 via an appropriate bus. The parking assist ECU 12 uses the travel distance (vehicle travel distance) of the vehicle calculated from the output signal of the vehicle speed sensor 18 and the steering angle position obtained from the steering angle sensor 16 during automatic guidance control, as described later. The position is estimated, a target steering angle corresponding to the deviation of the estimated vehicle position from the target trajectory is calculated, and the target steering angle is transmitted to the steering control ECU 30. The steering control ECU 30 controls the motor 32 so as to realize the target steering angle.

  FIG. 4 is a block diagram illustrating functions of the parking assist ECU 12. The parking assist ECU 12 includes a vehicle position estimation calculation unit 40 and a target trajectory calculation unit 42. The vehicle position estimating calculation unit 40 estimates and calculates the vehicle position and the moving distance of the vehicle during the parking assist execution based on the output signals of the steering angle sensor 16 and the vehicle speed sensor 18 as described in detail below. The target trajectory calculation unit 42 calculates the current target trajectory according to the difference between the previously calculated target trajectory and the vehicle position estimated by the vehicle position estimation calculation unit 40, and performs the above-described estimation based on the target trajectory. Determine the target steering angle at the vehicle position. The steering control ECU 30 controls the motor 32 based on the target steering angle determined in this way. The above-described calculation of the target trajectory by the target trajectory calculation unit 42 may be performed every time the vehicle moves by a predetermined moving distance (for example, 0.5 m). In addition, in order to leave a margin for performing such a trajectory correction, the first target trajectory is generated with a turning curvature somewhat smaller than the maximum turning curvature of the vehicle (for example, a turning curvature up to 90% of the maximum turning curvature). Is used. As a result, smooth steering control without giving the user any discomfort is realized. However, the present disclosure is not particularly limited to the method of calculating the target trajectory. For example, the present disclosure is not limited to the automatic trajectory control for automatically guiding the vehicle to the initially determined target trajectory without recalculating the target trajectory. It is also applicable.

  Here, the vehicle position estimation method by the vehicle position estimation calculation unit 40 will be described. For example, the following equation is used for the estimation calculation of the vehicle position.

In each equation, θ, X, and Y represent a two-dimensional coordinate value of the vehicle angle and the vehicle position with respect to the center of the rear axis, respectively (X ₀ and Y ₀ are initial positions, that is, automatic guidance. The same coordinate value of the vehicle position at the start of control). Further, dp represents a minute moving distance of the vehicle, and is calculated by integrating an output signal (wheel speed pulse) of the vehicle speed sensor 18 in a very short time. Note that the vehicle angle θ is the angle of change in the direction of the vehicle that occurs during turning. G (Str (p)) in Expression (1) is a turning curvature, and is obtained from, for example, a predetermined turning characteristic map using the steering angle position Str (p) obtained from the steering angle sensor 16 as an argument.

  Next, a description will be given of the cause of the phenomenon that the inventor has found that the position of the vehicle deviates from a route assumed in advance in automatic driving. FIG. 5 is a schematic diagram illustrating an example of a case where the vehicle 1 is parked (parked) in a target parking position by automatic parking. In the present embodiment, the automatic parking of the vehicle 1 is not completely automatic, and the parking assist device 10 of the vehicle 1 performs automatic steering, and the driver on the vehicle operates the accelerator pedal to adjust the speed.

At the position of the coordinates (X ₀ , Y ₀ ), the camera mounted on the vehicle 1 captures the parking frame G, which is the target parking position, and displays the parking frame G on the navigation screen. specify. The parking assist device 10 determines a predetermined route from the coordinates (X ₀ , Y ₀ ), which is the position of the starting point, to the coordinates (X _G , Y _G ) of the parking frame G, which is the target position. While the driver operates the accelerator pedal, the vehicle 1 moves to the coordinates (X _M , Y _M ) by automatic steering, pauses, turns off the steering wheel, and moves to the coordinates (X _G , Y _G ) of the parking frame G. Move towards. The speed around the coordinates (X _M , Y _M ) can be low and zero due to the driver's accelerator pedal operation.

  6A and 6B are schematic diagrams showing the positions of the wheels 3 in the vehicle 1. FIG. 6A shows the positions of the wheels 3 when traveling straight ahead, and FIG. 6B shows the positions of the wheels 3 when traveling a curve. FIG. When the driver operates the accelerator pedal, the output of the power source is controlled and the speed of the vehicle 1 is controlled. On the other hand, the parking assist device 10 autonomously controls the tire wheel steering angle θ of the tire wheels, here, the front tire wheels 4a, 5a, so that the vehicle 1 can travel on a predetermined route as shown in FIG. Becomes The tire wheel steering angle θ indicates the angle of the tire wheel direction at that time with reference to the direction of the tire wheel when the vehicle 1 travels straight as shown in FIG. Is a direction orthogonal to the rotation axis of the tire wheel and parallel to the road surface.

  However, from the start of steering of the steering wheel by the parking assist device 10 to the time when the vehicle 1 actually turns (body yaw occurs) via the change in the tire wheel steering angle of the tire wheels 4a and 5a, There is necessarily a predetermined delay time. The delay time is 1) a dead time (a steering delay time) which is a time required from the start of steering wheel turning to a change in the tire wheel steering angle of the tire wheels 4a and 5a, and 2) a tire wheel steering angle. It is known to include a primary delay (a delay time of the turning of the vehicle) which is a time required from the change to the turning of the vehicle 1. Therefore, the turning setting of the tire wheels by the parking assist device 10 is performed in consideration of the delay time assumed in advance for each vehicle type.

Here, when the vehicle 1 continues to move on the predetermined route shown in FIG. 5 at a specific speed assumed in advance, it is known that the positional deviation between the target stop position (target position) and the actual stop position is unlikely to occur. Have been. However, particularly when the driver operates the accelerator pedal, the speed of the vehicle does not move at a specific speed assumed in advance, but rather generally assumes an unexpected speed. Then, it has been found that when an unexpected speed is taken, the vehicle tends to move out of the route including the predetermined curve. In such a case, a position shift occurs between the target position, which is the target coordinates (X _G , Y _G ) in FIG. 5, and the actual position. In particular, in the case where the speed becomes extremely small due to the stationary state around the coordinates (X _M , Y _M ) shown in FIG. 5, this phenomenon becomes remarkable, and it has been found that it is difficult to park properly. .

  The inventor has further studied the above phenomenon while paying particular attention to the primary delay among 1) dead time and 2) primary delay included in the delay time. In particular, the inventor has re-examined that the first-order lag is caused by twisting of the viscoelastic bodies of the tires 4b, 5b disposed around the tire wheels 4a, 5a when the tire wheel steering angle changes.

  The viscoelasticity of the tire wheels 4a, 5a is generally larger than the viscoelasticity of the viscoelastic body constituting the tires 4b, 5b, and the tires 4b, 5b exert a frictional force due to a friction coefficient μ from the road surface during steering. Of resistance. Therefore, the tires 4b and 5b are inevitably twisted, and the turning of the vehicle 1 is delayed due to the twist.

  The inventor paid attention to the fact that the amount of the torsion depends on the speed of the vehicle 1, and when the speed changes, the amount of the torsion changes, and the primary delay also changes. As a result of further study, it is desirable that the inventor controls the tire wheel steering angle θ to be different depending on the speed of the vehicle 1 even when the vehicle travels on the same route including a predetermined curve. I thought. That is, the parking assist device 10 changes the tire wheel steering angle θ in accordance with a change in the first-order lag caused by a change in torsion of the tires 4b and 5b in accordance with the speed of the vehicle 1. Thereby, an appropriate tire wheel steering angle θ can be set according to the actual situation that the speed of the vehicle 1 is different, and as a result, the vehicle 1 can be guided to an appropriate route and target position set in advance.

  FIG. 7 is a graph showing changes in the tire wheel steering angle at the time of low-speed running and at the time of high-speed running, corresponding to the schematic views showing the straight running and the curved running of the vehicle 1, and specifically illustrating the above-described event. is there. The vehicle 1 can travel on a predetermined route including a curve at least partially. In this example, the vehicle 1 travels on a route including a predetermined route AB and a predetermined route BC, and a straight route AB exists before the curved route BC. Point A is the start point of the predetermined route AB, and point B is the start point of the predetermined route BC which is a curve.

  Then, as shown in the lower graph of FIG. 7, the case where the vehicle 1 travels on a predetermined route BC which is a curve at a first high speed, and a second speed lower than the first speed. It is assumed that the vehicle travels in two patterns. That is, even when traveling on the same route, one driver may travel at a high speed, and another driver may travel at a low speed. Naturally, such a difference in speed for each driving driver occurs, and considering the difference in speed is in line with the actual situation.

  Then, the parking assist device 10 of the present disclosure autonomously controls the tire wheel steering angle of the tire wheels according to such a difference in vehicle speed. Substantial control of the parking assist device is realized by a processor, a memory, and the like mounted on the parking assist ECU 12, which is an electronic control unit, and the steering control ECU 30. The parking assist device also stores a program that can autonomously control the tire wheel steering angle. The parking assist device can be realized not only by these members but also by a separately provided control unit or the like, and the mode is not particularly limited.

  When the vehicle 1 travels at a first speed (high speed) as shown in FIG. 7, the parking assist device controls the tire wheel steering angle to take a first steering angle pattern, and the vehicle 1 When traveling at a speed (low speed), control is performed so that the tire wheel steering angle takes the second steering angle pattern.

  As shown in the graph, at the point B which is the starting point of the predetermined route BC, the tire wheel steering angle of the second steering angle pattern is set to be larger than the tire wheel steering angle of the first steering angle pattern. I have. Even when the vehicle 1 travels on the same route as assumed, even when traveling at different speeds, the parking assist device assists the driver by appropriately selecting a steering angle pattern of the tire wheel steering angle according to the speed. However, the vehicle 1 can travel without largely deviating from the predetermined route and reach the target position assumed in advance. From this control, it is understood that the torsion generated in the tires 4b and 5b at a low speed is larger than that at a high speed, so that a large tire wheel steering angle is required at a low speed as shown by the second steering angle pattern. .

  When the speed of the vehicle becomes higher than the predetermined threshold speed, the twist generated in the tires 4b and 5b can be ignored, and the first-order lag is considered to disappear. Therefore, when the second speed is smaller than the predetermined threshold speed, the parking assist device changes the tire wheel steering angle of the second steering angle pattern to the first steering angle pattern at a predetermined point B on the predetermined route BC. May be controlled to be larger than the tire wheel steering angle. That is, when the speed of the vehicle 1 is low, the vehicle tends to deviate from the assumed route. Therefore, only when the (second) speed of the vehicle 1 is lower than the predetermined threshold speed, the parking assist device performs the tire wheel steering shown in FIG. Performs corner control.

  When the second speed is higher than the predetermined threshold speed, the parking assist device determines that the tire wheel steering angle of the second steering angle pattern is the first steering angle pattern at the predetermined point B on the predetermined route BC. May be controlled so as not to be larger than the tire wheel steering angle. That is, when the speed of the vehicle 1 is high, it is difficult to deviate from the assumed route. Therefore, when the (second) speed of the vehicle 1 is higher than the predetermined threshold speed, the parking assist device controls the tire wheel steering angle shown in FIG. Do not do.

  Normally, the wheel for controlling the tire wheel steering angle is the front wheel as shown in FIG. From the viewpoint of the weight balance of the vehicle 1, the traveling direction, and the driving wheels, various settings of the above-described threshold speed can be considered.

  Components that are likely to affect the weight balance of the vehicle are power sources such as internal combustion engines and / or electric motors. When the power source is the power source D1 shown in FIG. 6 and is arranged closer to the front wheels than the rear wheels, and drives the front wheels, the weight of the vehicle 1 is distributed to a large portion of the front portion where the front wheels are located. For this reason, when the vehicle 1 moves backward as compared with the case where the vehicle 1 moves forward, the bending of the vehicle body due to steering tends to increase. Therefore, it may be desirable to set the threshold speed when moving forward to be smaller than the threshold speed when moving backward. The threshold speed is, for example, about 2.0 km / hour for forward travel and about 4.0 km / hour for reverse travel.

  On the other hand, when the power source is the power source D2 shown in FIG. 6 and is arranged closer to the rear wheels than the front wheels and drives the rear wheels, the weight of the vehicle 1 is distributed to a rear portion with the rear wheels at a large rate. Is done. For this reason, when the vehicle 1 moves forward as compared with the case where the vehicle 1 moves backward, the curve of the vehicle body due to steering tends to increase. Therefore, it may be desirable to set the threshold speed when moving forward to be higher than the threshold speed when moving backward. The threshold speed is, for example, about 4.0 km / hour for forward travel and about 2.0 km / hour for reverse travel.

  When only the front wheels are steered wheels to be steered, the rear wheels are fixed wheels to which no steering angle is given. However, the present invention is also applicable to a vehicle in which the rear wheels are all steering wheels (four-wheel steering; 4WS).

  Hereinafter, 1) dead time and 2) first-order lag included in the delay time will be described again together with the result of an experiment in which the delay time of the vehicle is measured. The dead time is one component of the delay time that can always occur with a constant amount regardless of the vehicle speed or the coefficient of friction μ of the road surface. FIG. 8 is a graph showing an experimental result of measuring a delay time according to the speed of the vehicle, and a delay time of about 200 ms (millisecond) occurs in both forward and backward situations of the vehicle regardless of the speed. You can see that.

  From this experimental result, one component of the delay time that always occurs regardless of the speed can be defined as the dead time. It is considered that the dead time is caused by hysteresis (play) of the steering wheel, a mechanism such as a torsion bar and a rubber bush in the system from the steering of the steering wheel to the turning of the wheel.

The steering wheel steering angle θ _a (degree) after t (seconds) accompanying the dead time is expressed by the following equation (1). In the formula (1), θ ₀ is the initial steering wheel steering angle (in degrees), ω is the steering wheel angular velocity (degrees / sec), t k _(s) it is a waste of time.

θ _a = θ ₀ + ω (t−t _k ) (1)
However, if t−t _k <0, t−t _k = 0.

  Next, the first-order lag will be described. The primary delay is one component of the delay time that changes according to the speed of the vehicle. FIG. 9 is a graph showing another experimental result of measuring the delay time according to the speed of the vehicle. FIG. 9A is a graph showing a delay time (first-order delay) when the vehicle 1 moves forward, and FIG. 9B is a graph showing a delay time (first-order delay) when the vehicle 1 moves backward. From this, it is understood that there is a delay time (first-order delay) that changes according to the speed of the vehicle.

  It is considered that a delay occurs from the start of turning of the tire wheel to the occurrence of yaw of the vehicle due to the viscoelasticity of the tire, resulting in a first-order delay. It is considered that the first-order lag due to the viscoelasticity changes depending on the vehicle speed and the friction coefficient μ of the road surface. From the experimental results in FIG. 9, it is understood that the delay time (first-order delay) decreases as the speed of the vehicle increases.

When the horizontal axis (speed) is x and the vertical axis (delay time) is y, as a result of the regression analysis, in FIG. 9A, a linear form of y = −250.49x + 534.97 is obtained. In b), a linear formula of y = −115.03x + 486.92 was obtained. When these are extended until y = 0, that is, the delay time (first-order delay) becomes 0, x ₁ = about 2.1 (km / h) in FIG. 9A, and x ₂ = about 2.1 in FIG. 9B. A value of 4.2 (km / h) is obtained.

Next than this smaller the speed of the vehicle primary delay 0 as a boundary the speed of x ₁ in the case of forward, this speed corresponds to the threshold speed to be whether the boundary primary delay occurs. The parking assist device may control the tire wheel steering angle so as to take the second speed pattern in FIG. Reverse this than the speed of the vehicle is less if the primary delay becomes 0 as a boundary the speed of x ₂ in the case of this speed corresponds to the threshold speed to be whether the boundary primary delay occurs. The parking assist device may control the tire wheel steering angle so as to take the second speed pattern in FIG. The vehicle in this experiment is of a type in which the power source is disposed closer to the front wheels than the rear wheels and drives the front wheels, and the threshold speed when moving forward is lower than the threshold speed when moving backward (x ₁ < x ₂ ).

In _calculating the tire wheel steering angle θ _c (degree) after t (second) due to the first-order delay, first, there is no delay of the steering wheel steering after t (second) expressed by the following equation (2). The angle θ _b is obtained in degrees. Equation (2) indicates that the steering wheel steering angle θ _b without delay after t (second) is represented by a cubic expression of the steering wheel steering angle θ _a after t (second) with dead time. ing. A, B, C, and D are arbitrary constants.

^{_{θ b = A * θ a 3}} + B * θ a 2 + C * θ a + D ··· (2)

Further, the tire wheel steering angle θ _c (degrees) after t (seconds) accompanying the first-order delay is expressed by the following equation (3). In the equation (3), T (second) is a time constant of a first-order lag.

θ _c = (1−exp (−t / T)) θ _b (3)

  The time constant T depends on the twist of the viscoelastic body (rubber component and the like) of the tire, and it is known that the value differs depending on the vehicle speed. It has been found that the time constant T at the vehicle speed v (km / h) is desirably set by the following equation (4). In Equation (4), a and b are arbitrary constants (a <0, b> 0).

  T = a × v + b (4)

  In the above description, the parking assist device 10 that assists the driver when the vehicle is parked has been described. However, the idea of the present disclosure is not limited to application to parking, and other situations in which the vehicle is automatically steered. Is also applicable. Therefore, the present disclosure can be regarded as an automatic steering device that can be applied to a scene wider than the parking assist device.

  Although the embodiments of the vehicle and the automatic steering device according to the present disclosure have been described with reference to the drawings, the present disclosure is not limited to such examples. It is clear that those skilled in the art can conceive various changes, modifications, substitutions, additions, deletions, and equivalents within the scope of the claims. Naturally, it is understood that they belong to the technical scope of the present disclosure.

  INDUSTRIAL APPLICABILITY The vehicle and the automatic steering device according to the present disclosure are useful for performing control for automatically performing steering so as to accurately move a vehicle toward a target position.

1 vehicle 3 wheels 4a, 5a, 6a, 7a tire wheels 4b, 5b, 6b, 7b tires (viscoelastic body)
10 Vehicle parking assist device (automatic steering device)
12 Parking assistance ECU (electronic control unit)
16 steering angle sensor 18 vehicle speed sensor 20 back monitor camera 22 display monitor 30 steering control ECU
32 Motor 40 Vehicle position estimation calculation unit 42 Target trajectory calculation unit 50 Reverse shift switch 52 Parking switch

Claims (28)

Tire wheel, having a wheel comprising a viscoelastic body disposed around the tire wheel and in contact with the road surface,
A vehicle that autonomously controls a tire wheel steering angle of the tire wheel and is capable of traveling on a predetermined route,
The predetermined path includes a curve at least in part,
When traveling on the predetermined route at a first speed, the tire wheel steering angle is a first steering angle pattern,
When the vehicle travels on the predetermined route at a second speed lower than the first speed, the tire wheel steering angle is a second steering angle pattern,
At a predetermined point on the predetermined route, the tire wheel steering angle of the second steering angle pattern is larger than the tire wheel steering angle of the first steering angle pattern.
vehicle. The vehicle according to claim 1,
The predetermined point is at least a starting point of the curve,
vehicle. The vehicle according to claim 1 or claim 2,
The predetermined path includes a straight line before the curve,
vehicle. The vehicle according to any one of claims 1 to 3, wherein
The viscoelasticity of the tire wheel is larger than the viscoelasticity of the viscoelastic body,
vehicle. The vehicle according to claim 4,
At least a part of the tire wheel is made of metal,
vehicle. The vehicle according to claim 4 or claim 5,
At least a part of the viscoelastic body is made of rubber,
vehicle. The vehicle according to any one of claims 1 to 6, wherein
When the second speed is smaller than a threshold speed, the tire wheel steering angle of the second steering angle pattern is the tire wheel steering angle of the first steering angle pattern at the predetermined point on the predetermined route. Greater than,
vehicle. The vehicle according to claim 7,
When the second speed is greater than the threshold speed, at the predetermined point on the predetermined route, the tire wheel steering angle of the second steering angle pattern becomes the tire wheel steering angle of the first steering angle pattern. Not bigger than the corner,
vehicle. The vehicle according to claim 7 or claim 8,
The wheel is a front wheel,
In addition, equipped with rear wheels,
The threshold speed when moving forward is smaller than the threshold speed when moving backward,
vehicle. The vehicle according to claim 9,
Equipped with a power source,
The power source is arranged closer to the front wheel than the rear wheel.
vehicle. The vehicle according to claim 10,
The power source drives the front wheels;
vehicle. The vehicle according to claim 7 or claim 8,
The wheel is a front wheel,
In addition, equipped with rear wheels,
The threshold speed when moving forward is greater than the threshold speed when moving backwards,
vehicle. The vehicle according to claim 12,
Equipped with a power source,
The power source is disposed closer to the rear wheel than the front wheel,
vehicle. The vehicle according to claim 13,
The power source drives the rear wheel;
vehicle. Tire wheel, having a wheel comprising a viscoelastic body disposed around the tire wheel and in contact with the road surface,
An automatic steering device that autonomously controls a tire wheel steering angle of the tire wheel and can be mounted on a vehicle that can travel on a predetermined route,
The predetermined path includes a curve at least in part,
When traveling on the predetermined route at a first speed, the tire wheel steering angle is a first steering angle pattern,
When the vehicle travels on the predetermined route at a second speed lower than the first speed, the tire wheel steering angle is a second steering angle pattern,
At a predetermined point on the predetermined route, the tire wheel steering angle of the second steering angle pattern is larger than the tire wheel steering angle of the first steering angle pattern.
Automatic steering device. The automatic steering device according to claim 15, wherein
The predetermined point is at least a starting point of the curve,
Automatic steering device. The automatic steering device according to claim 15 or claim 16,
The predetermined path includes a straight line before the curve,
Automatic steering device. The automatic steering device according to any one of claims 15 to 17, wherein
The viscoelasticity of the tire wheel is larger than the viscoelasticity of the viscoelastic body,
Automatic steering device. The automatic steering device according to claim 18, wherein
At least a part of the tire wheel is made of metal,
Automatic steering device. The automatic steering device according to claim 18 or claim 19,
At least a part of the viscoelastic body is made of rubber,
Automatic steering device. The automatic steering device according to any one of claims 15 to 20, wherein
When the second speed is smaller than a threshold speed, the tire wheel steering angle of the second steering angle pattern is the tire wheel steering angle of the first steering angle pattern at the predetermined point on the predetermined route. Greater than,
Automatic steering device. The automatic steering device according to claim 21,
When the second speed is greater than the threshold speed, at the predetermined point on the predetermined route, the tire wheel steering angle of the second steering angle pattern becomes the tire wheel steering angle of the first steering angle pattern. Not bigger than the corner,
Automatic steering device. The automatic steering device according to claim 21 or claim 22,
The wheel is a front wheel,
In addition, equipped with rear wheels,
The threshold speed when moving forward is smaller than the threshold speed when moving backward,
Automatic steering device. An automatic steering device according to claim 23,
Equipped with a power source,
The power source is arranged closer to the front wheel than the rear wheel.
Automatic steering device. An automatic steering apparatus according to claim 24,
The power source drives the front wheels;
Automatic steering device. The automatic steering device according to claim 21 or claim 22,
The wheel is a front wheel,
In addition, equipped with rear wheels,
The threshold speed when moving forward is greater than the threshold speed when moving backwards,
Automatic steering device. An automatic steering apparatus according to claim 26,
Equipped with a power source,
The power source is disposed closer to the rear wheel than the front wheel,
Automatic steering device. The automatic steering device according to claim 27,
The power source drives the rear wheel;
Automatic steering device.

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