JP6921168B2 - How to run in a platoon based on wheel pulse signals - Google Patents

Description

The present invention relates to a platooning method in which a vehicle position, a speed, and an inter-vehicle distance calculated from a wheel pulse signal are shared by inter-vehicle communication, and a preceding vehicle (a vehicle in front of the own vehicle including the leading vehicle) is tracked by a following vehicle.

In platooning, a system in which the following vehicle recognizes the rear part of the preceding vehicle, the lane, etc. and tracks the preceding vehicle (Patent Document 1), or the following vehicle acquires the front vehicle position information by GPS by vehicle-to-vehicle communication and owns itself. A system is being developed (Japanese Patent Application No. 2018-161142) that matches and tracks the GPS position information of a car.

In the GPS system, an error called multipath occurs due to the influence of obstacles (buildings, trees, electric wires, etc.). When this multipath occurs, the position cannot be specified with high accuracy. In addition, since reception is not possible in the tunnel, when the GPS reception intensity decreases, automatic driving is switched to manual driving (Patent Document 2), or a digital map is provided to display a road unsuitable for automatic driving and deal with it (Patent Document 3). ) Etc., but it is not original.
It is desired to develop a system that can perform the original platooning without requiring GPS or by redundantly adapting to the decrease in GPS intensity.

To drive in an environment where GPS position information cannot be used, use a visual device such as a camera or laser to recognize the self-position by illuminating a white line on the road or a mark such as a structure, and use a magnetic marker embedded in the road surface. A method of detecting self-position recognition, a method of measuring inertia to calculate a trajectory from the starting point, and a method of calculating a trajectory from the starting point using a vehicle motion model (inertial navigation) can be considered. At first glance, it seems that each of these functions independently, but there is a need for a technique (all) to trace between "mark to mark" or "magnetic marker to magnetic marker", and there is a technique to prepare for. Inertial navigation.

From the current mark to the next mark, and from the current magnetic marker to the next magnetic marker, it is reached by inertial navigation. Patent Document 4 discloses a technique for navigating (inertial) under Newton's second law regardless of whether or not a model for calculating a trajectory is used.

The current position of the vehicle can be confirmed by comparing it with the map. The Ministry of Land, Infrastructure, Transport and Tourism provides a road reference point guidance system (Non-Patent Document 1). Latitude, longitude, and altitude are displayed by kilometer posts (KP: point markers every 1 km) installed on the road.

Japanese Patent No. 6109998 JP-A-2018-077771 Special Table 2017-530045 Japanese Patent No. 6202700

www.road-refpoint.jp/ Road reference point guidance system

According to the inertial navigation system, the original platooning can be performed without the need for GPS or by redundantly adapting to the decrease in GPS intensity. However, in order to apply inertial navigation to platooning, it is necessary not only to be able to identify the position of the own vehicle, but also to track the vehicle in front and to know the distance from other vehicles in the platoon accurately.

The above-mentioned prior art does not solve the problems unique to platooning, assuming that individual vehicles travel by automatic driving.

The present inventor has created an automatic driving method that is not based on GPS (information from the outside) based on the idea that time and space are shared only by platooning vehicles in platooning.
That is, the current time in platooning is the current time from the starting point to the destination, and the space is the current location (current lane). If you think about it like that, you can move away from the world time / world map and run in a platoon with the same indicator in the common time of the vehicle in front and the tracking vehicle, and in the common lane (space) of the vehicle in front and the tracking vehicle. Become. As a ruler, the present inventor has selected a wheel pulse.
The distance and speed from the starting point can be known from the wheel pulse. As a result, tracking running based on the wheel pulse signal that can be acquired within the shared space / shared time becomes possible without relying on guidance such as GPS coming from outside the shared space.

That is, in the platooning method according to the first invention, each vehicle forming the platoon detects the position / speed information of its own vehicle based on the pulse signal from the wheel pulse signal oscillator provided by each vehicle, and the following vehicle communicates between vehicles. Receives the position / speed information of the vehicle ahead of the own vehicle, calculates the inter-vehicle distance from the own vehicle from the received position / speed information and the position / speed information of the own vehicle, and the following vehicle is ahead. The lateral deviation in the traveling lane detected by the detection means such as a camera provided in the vehicle is received by inter-vehicle communication, the lateral deviation of the own vehicle is matched with the lateral deviation of the vehicle in front, and the traveling locus with the position of the vehicle in front as the target position is obtained. Ask.

In the platooning method according to the second invention, each vehicle forming the platoon detects the position / speed information of its own vehicle based on the pulse signal from the wheel pulse signal oscillator provided by each vehicle, and each vehicle has a steering wheel pulse. The actual steering angle is calculated from the signal and the non-steering wheel pulse signal, the position of the center of gravity of the own vehicle is calculated from this actual steering angle, and the following vehicle is the position and speed of the vehicle ahead of the own vehicle by inter-vehicle communication. The information and the position information of the center of gravity are received, and based on the received position / speed information, the position information of the center of gravity, the position / speed information of the own vehicle, and the position information of the center of gravity, the traveling locus with the position of the center of gravity of the vehicle in front as the target position is obtained.

In the first and second inventions, each vehicle forming the formation detects the position / speed information of the own vehicle based on the pulse signal, and transmits the detected value to the following vehicle by inter-vehicle communication. However, it is also conceivable to directly transmit the pulse signal of the vehicle in front to the following vehicle to detect the position / speed information of the vehicle in front in the following vehicle.

In the second invention, the actual steering angle of the vehicle is calculated from the cosine of the steering wheel pulse and the non-steering wheel pulse by recognizing the vehicle speed from the non-steering wheel pulse. The position of the center of gravity of the vehicle is calculated using the wheel pulses of the steered wheels and the non-steered wheels and the vibration sensor.

Specifically, first, the steering wheel (front wheel) and the non-steering wheel (rear wheel) are provided with a wheel pulsar for detecting the rotation of the wheel, and the steering wheel speed (distance) and the non-steering wheel speed (distance) are detected.
Next, the actual steering angle of the steering wheel is calculated from the ratio of the detected steering wheel speed (distance) and the non-steering wheel speed (distance).
Next, with the calculated sine of the actual steering angle (sin), the turning radius of the actual steering angle is calculated by excluding the wheel base, and the turning center position (that is, the steering wheel rotation center line and the non-steering wheel rotation center line) Find the intersection).
Further, a yaw sensor for detecting the eccentric speed (yaw rate) of the vehicle body is provided, and the radius of gyration of the center of gravity is calculated from the yaw rate detected by the yaw sensor and the above-mentioned non-steering wheel speed.
Next, the intersection of the radius of gyration arc of the center of gravity and the axle line, that is, the position of the center of gravity is obtained from the turning center position.

In the second invention, "the actual steering angle, the position of the center of gravity, and the vehicle speed can be known by equipping the wheel so that the pulse and the yaw rate can be detected, so that the traveling locus can be calculated". That is, inertial navigation can be performed.

On top of that, a visual sensor such as a camera recognizes a mark (landmark) such as a white line, and it is possible to drive by correcting an error with the calculated value of inertial navigation of the own vehicle.

The following vehicle tracks the vehicle in front by determining the steering angle to reach the vehicle in front by comparing the position, direction, and time of the vehicle in front received from the vehicle in front with the position, direction, and time of the vehicle in front. The steering angle to the vehicle in front can be calculated from the equation of state or the stability factor. Details are as described in the drawings.

GPS is not required because the positions (coordinates) and directions of the preceding vehicle and the following vehicle are grasped and the steering control of the following vehicle that tracks the preceding vehicle is executed in correspondence with the time and space shared within the platoon. Alternatively, it is possible to control the tracking of the vehicle ahead by using GPS together.

Explanatory drawing of the concept of tracking control based on a wheel pulse. The figure which showed the relationship between the distance from the starting point and the left-right deviation with respect to the road width (lane width). Explanatory drawing of front wheel actual steering angle and center of gravity position estimated from wheel speed and yaw rate. XY coordinates showing the position of the center of gravity of the vehicle as the front-back / left-right movement distance from the starting point (starting point) It is explanatory drawing of the flow of control parameter acquisition.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. 1 and 2 show explanatory views of the concept of tracking control based on the wheel pulse.
Align the zero point of the wheel pulse count with the starting point at the bottom right of the figure for both the vehicle in front and the vehicle following. The inter-vehicle distance ΔS is known by the difference in the number of pulses, and since the time is shared, the speed can be known and the inter-vehicle time can be known.

The accuracy of distance / speed detection by wheel pulse is determined and verified as an inspection item during regular inspection and maintenance of the vehicle, and at the time of actual operation, a mark (landmark) such as a temporary stop line of the operation route is set and the starting point is set. The distance from the mark to the landmark is grasped with the required accuracy, and the distance detection accuracy by the wheel pulse when passing through the place is collated and verified. If necessary, use it as a marker for zero point alignment.

In platooning, both the preceding vehicle and the following vehicle travel in the same lane (road width). For this reason, the position in the width of the lane is matched with the vehicle in front to reach the position of the vehicle in front by steering control. In the curve, the lateral speed is generated in addition to the front-rear speed, so the vehicle speed is the combined speed with the front-rear, but since the lane is shared in the shared space, it can be tracked only by the front-rear speed (= speed by wheel pulse). You can share the lane and track where you are in the lane width with a camera or the like.

If there is no lane sharing, the present invention will be the second invention, and this embodiment will be described with reference to FIG.
3 and 4 are explanatory views of the front wheel actual steering angle and the position of the center of gravity estimated from the wheel speed and the yaw rate. An example of a four-axle vehicle with two front axles and two rear axles is shown. For the sake of simplicity, a so-called bicycle model in which the left and right wheels are integrated on the center line of the vehicle will be described. Wheel pulsars are provided on the steering wheels and non-steering wheels, and yaw sensors are provided at arbitrary positions on the center line of the vehicle body.

When the wheel speeds vf1, vf2, vr1, vr2 of each wheel are detected from the wheel pulsar and the yaw rate γ is detected from the yaw sensor, the actual steering angle of the front wheels δf1 is obtained from the following equations (1), (2) and (3). , δf2 can be calculated.

Next, the radius of gyration (R) of the center of gravity is calculated from the following equation (5). At this stage, the radius of gyration of the center of gravity is obtained, but the position of the center of gravity is unknown. How to find the position of the center of gravity will be described later.

The Ackermann steering mechanism, which is the basic knowledge of the steering system, is known. According to that mechanism, the center of rotation at extremely low speeds is on the rear axle line. In the case of the rear two-axle drive vehicle in this figure, the rotation center position is the "O" point where the center line between the rear two axles and the extension line of the rotation axis of the steering wheel intersect. Next, when the intersection with the front-rear axis (x-axis) of the vehicle is obtained by drawing an arc centered on the "O" point with the turning radius obtained by the above equation (5), that becomes the center of gravity GC. It will be at the position of _{l r} forward from the center line between the rear two axes. That is, the position is in the following equation (8).

Since the vehicle motion occurs around the center of gravity, the direction of the vehicle speed is the direction of the angle β (lateral slip angle) with respect to the vehicle front-rear axis (x-axis). This side slip angle β becomes the following equations (9) and (10) that change depending on the square of the vehicle speed.

The calculation flow in FIGS. 3 and 4 will be described with reference to the control parameter acquisition flow in FIG. In FIG. 5, the flow is explained in the upper part and the flow is explained in the lower part.

The explanation is from left to right. The wheel base l is a constant. The steering wheel pulse is the front wheel. There are front 1st axis and front 2nd axis, but the rudder angle ratio of the 1st and 2nd axes is determined by the Ackermann steering mechanism, so it is represented by the 1st axis (may be represented by the 2nd axis). ). The non-steering wheel pulse is the rear wheel. There are one rear axle and two rear axles, but any wheel pulse may be used. Both the steering wheel pulse and the non-steering wheel pulse are obtained from the ABS wheel pulsar. You may equip a dedicated pulsar. The yaw rate is obtained from the yaw sensor, which is a must-have for autonomous vehicles.

The wheel pulse is converted to the wheel speed by the formula shown in the middle frame of the figure. The actual steering angle is calculated from the wheel speed by the above equations (1), (2) and (3). Next, the radius of the center of gravity is calculated from the vehicle front-rear speed and the yaw rate by the following equation (4).

The steering wheel turning radius is calculated by the above equation (5) from the wheel base and the actual steering angle of the front wheels.

The non-steering wheel turning radius is calculated from the steering wheel turning radius and the actual steering angle by the following equation (6).

From the radius of gyration of the non-steering wheel and the radius of gyration of the center of gravity, the lateral slip angle β0 in the extremely low speed range is calculated by the following equation (7).

The position of the center of gravity is calculated by the above equation (8) from the radius of gyration of the center of gravity and the lateral slip angle β0 in the extremely low speed region.

When the yaw rate γ is obtained by the yaw sensor and the side slip angle β is obtained by the above equations (9) and (10), the front vehicle can be tracked by the method described in the dotted line frame in the lower part of FIG. That is, when the yaw rate γ is detected from the yaw sensor and the side slip angle β is calculated from the equations (9) and (10), the locus calculation with the latitude and longitude as the coordinate axes can be performed by the following equations (11) and (12).

Here, x is the forward / backward movement distance, y is the lateral movement distance, and if x is the latitude, y corresponds to the longitude. φ is the yaw angle which is the integral value of yaw rate γ. Combining x and y gives a travel path trajectory.

Equations (11) and (12) are functions of time, but the path locus obtained from xy is a distance. Therefore, when viewed on the distance axis, the difference between the distance of the vehicle in front and the distance of the own vehicle is the arc length (arc length (11). ΔS), a fan shape is assumed in which the angle difference between the direction of the vehicle in front and the direction of the own vehicle is the arc angle (θ). From the arc length and the arc angle, the arc radius (R) is given by the following equation (13). The steering angle of the following vehicle that tracks the arc is given by Equation (14).

From the above, it is possible for the following vehicle to follow the vehicle ahead by speed control in which each vehicle in the platoon holds down the inter-vehicle distance on the distance axis by the wheel pulse and speed control in which the lateral deviation in the lane is matched with the vehicle in front by the visual sensor.

Further, the actual steering angle of the steering wheel is obtained from the speed due to the wheel pulse of the steering wheel and the speed due to the wheel pulse of the non-steering wheel, and the turning center position based on the Ackermann-Janto theory is obtained from the obtained actual steering angle and the wheel base. At the same time, the position of the center of gravity is obtained from the yaw rate by the yaw sensor and the speed due to the non-steering wheel pulse, and the side slip angle of the vehicle body as the vehicle speed increases is obtained by the formula of the side slip angle with the side slip coefficient and stability factor as factors. The position and path of the center of gravity are calculated from the anteroposterior movement distance obtained by integrating the cosine of the sum of the yaw angle obtained by integrating the side slip angle and the yaw angle and the lateral movement distance obtained by integrating the sine. Inertial navigation can be performed by verifying the position / route against an external mark by a visual sensor, and the inertial navigation position information can be shared by inter-vehicle communication so that the following vehicle can track the vehicle in front.

Claims (6)

It is a platooning method in which a leading vehicle and a plurality of automatic driving following vehicles following the leading vehicle form a platoon, and each vehicle forming the platoon is itself based on a pulse signal from a wheel pulse signal oscillator provided in each vehicle. The position / speed information of the vehicle is detected, and the following vehicle receives the position / speed information of the vehicle in front of the own vehicle by inter-vehicle communication, and the received position / speed information and the position / speed information of the own vehicle. The distance to the own vehicle is calculated from A platooning method based on a wheel pulse signal, characterized in that a traveling locus with a vehicle position in front as a target position is obtained according to a lateral deviation. It is a platooning method in which a leading vehicle and a plurality of automatic driving following vehicles following the leading vehicle form a platoon, and each vehicle forming the platoon is itself based on a pulse signal from a wheel pulse signal oscillator provided in each vehicle. The position and speed information of the vehicle is detected, and each vehicle calculates the actual steering angle from the steering wheel pulse signal and the non-steering wheel pulse signal, calculates the position of the center of gravity of the own vehicle from this actual steering angle, and the following vehicle The position / speed information and the center of gravity position information of the vehicle ahead of the own vehicle are received by inter-vehicle communication, and based on the received position / speed information and the center of gravity position information and the position / speed information and the center of gravity position information of the own vehicle. A platooning method based on a wheel pulse signal, characterized in that a traveling locus with the center of gravity of the vehicle in front as a target position is obtained. In the platooning method according to claim 2, the wheel pulses of the steering wheels and the non-steering wheels are detected, the vehicle speed is recognized from the non-steering wheel pulses, and the following equation is obtained from the cosine of the steering wheel pulse and the non-steering wheel pulse. A platooning method based on a wheel pulse signal, which comprises calculating the actual steering angle using.

In addition, δ _{f1 and} δ _f2 are the actual steering angles v _f1, v _f2, v _r1, v _{r2, and} the speed of each wheel.
In the platooning method according to claim 2, the platooning based on the wheel pulse signal is characterized in that the position of the center of gravity of the vehicle is calculated from the following formula by using the wheel pulses of the steering wheels and the non-steering wheels and the vibration sensor. Method.

R, R _1, R _y are the arc radius v is the wheel speed γ is the yaw rate l is the wheel base length l _r is the distance to the center of gravity position β ₀ is the side slip angle In the platooning method based on the wheel pulse signal according to any one of claims 1 to 4, in order to verify the detection accuracy of the distance / speed by the wheel pulse, a mark (land) in which the distance from the starting point is known in the operation route. A platooning method based on a wheel pulse signal, which comprises determining a mark), calculating the distance from the starting point to the mark based on the wheel pulse signal, and comparing the calculated value with a known distance. It is a platooning method in which a leading vehicle and a plurality of automatic driving following vehicles following the leading vehicle form a platoon. Each vehicle forming the platoon is equipped with a wheel pulse signal oscillator, and the following vehicle is ahead of the own vehicle. The wheel pulse signal of the vehicle in front of the vehicle is acquired by inter-vehicle communication, the position and speed of the vehicle in front are calculated based on the acquired wheel pulse signal, and the calculated position of the vehicle in front is set as the target position to track the traveling locus of the vehicle in front. A platooning method based on a wheel pulse signal, which is characterized by obtaining a traveling locus.

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