JPS61278912A - Method for guiding unmanned moving machine by spot following system - Google Patents

Abstract

PURPOSE:To attain again a guiding control at a target spot and at the current position of an unmanned moving machine with the next spot of a dot string as a new target instead of a current target spot when a distance is below a certain distance or becomes longer slowly. CONSTITUTION:The current position Tt of a vehicle is measured, and a distance at between the measured current position and the target spot P is calculated. Then it is discriminated to be smaller than the preset prescribed radius R or not. Where at<R, it it considered to reach the target spot P, and the next spot of the dot string is set to a new target spot. Where at>=R, the at is discrimi nated to be larger than a at-1, that is, one unit before or not. Where at>at-1, the vehicle is far away from the target spot P, and therefore the spot is judged to be the point when the target spot P is passed to set the next spot of the dot string to the new target spot. Where at<=at-1, the vehicle is approaching the target spot P, and therefore, the operation advances. Here a rudder angle command is calculated, and it is outputted to a steering device according to said command.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for guiding an unmanned mobile machine using a point tracking method.

[Conventional technology]

In the conventional guidance method of this type, the planned travel route is set at points A, B, C, and D, as shown in FIG.

E is set by teaching E, and when traveling on a route connecting these points, for example, on route AB,
There is a system that calculates the current position of a mobile vehicle using a geomagnetic sensor and then controls the wheels so that they always face point B (Special Japanese Patent No. 59-26032).

In addition, as another guidance method of this kind, each point on the planned travel route is taught in the same manner as above, and these given points are approximated with a spline curve used in the CAD field. There is a system in which the vehicle is replaced with a continuous curve on a two-dimensional plane, and the vehicle body is steered so as to trace the curve. “Trajectory Design”).

[Problem that the invention seeks to solve]

However, in the former guidance method, the direction of the wheels is simply
It depends on the speed of the moving vehicle and the steering delay factor, but the distance between each point must be adjusted to at least correct the steering delay. The distance it takes for the wheels to point toward the target point is required.

If this distance between points is long, there will be a delay in steering which is practically useless when turning around a corner, and conversely, if it is short, it will not be possible to correct the delay in steering and it will be difficult to pass the target point. Can not. %, if the target point cannot be passed due to the above reasons, or if the target point cannot be passed due to disturbances such as unevenness of the road surface, the time to determine the next target point will be missed, and the O control will be hindered thereafter. There are problems such as:

However, since the calculation formula for the latter guidance method is complicated, if the calculation is performed using an inexpensive micro combinator that can be economically mounted on a car, it will take several times to calculate the tracking of one point to point. It takes seconds.

Note that a new calculation result is required within 0.1 seconds in order to control the steering of the vehicle without delay.

Therefore, this guidance method is insufficient to be controlled by an economically practical microcomputer, and even if such a microcomputer were installed in a vehicle, there would be a significant steering delay, making it useless for practical use.

The present invention has been made in view of the above-mentioned circumstances, and is an unmanned mobile machine using a point following method that can travel on a scheduled route given by a point following method including a complicated curved route without causing a delay in turning the steering wheel. The purpose is to provide a guidance method for

[Means and operations for solving the problem] According to the present invention, the distance between the current target point and the current position of the unmanned mobile machine is sequentially calculated from among the points taught as a series of points in the point tracking method. However, when the distance becomes less than a certain distance or when the distance gradually increases, the next point in the series of points is set as a new target point instead of the current target point, and unmanned movement The guidance and control of the unmanned mobile machine is performed again based on the current position of the machine.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First, we applied a front-wheel steering four-wheel vehicle as an unmanned mobile machine,
An example of a method for determining the current position of the four-wheeled vehicle will be explained.

This four-wheeled vehicle is equipped with an odometer that measures the distance traveled by counting the number of pulses output from pulse encoders attached to the wheels, and a marine gyro compass that measures the direction of travel of the vehicle. Equipped with

Based on the outputs of the odometer and gyro compass, the current position of the vehicle can be determined by the following equation, if the driving area is expressed in xy coordinates. Here, °CΔS indicates the distance traveled per one sampling time, α indicates the inclination (progressing direction) of the vehicle body with respect to the X-axis, and (!o*3'o) indicates the coordinates of the starting point of the vehicle.

In addition to the above-mentioned gyro compass, means for measuring the direction of travel of the vehicle include a geomagnetic sensor, a rate gyro, a dual species gyro, a vibration gyro, a laser gyro, or a device that determines the direction based on the difference in the rotation speed of the left and right wheels. etc. are possible. Further, the current position of the vehicle may be directly measured using radio wave surveying or the like.

Next, consideration will be given to the intervals between points, etc. when one planned travel route is taught as a sequence of points on the planned travel route.

In a certain vehicle, at a vehicle speed of 1 m/s@e, the minimum turning radius at which the vehicle body does not skid is 4.1 m, but as the vehicle speed increases, the minimum turning radius also increases.

When determining the optimal spacing between each of the above, the minimum turning radius should be 115° to 4°, based on the above minimum turning radius.
The spacing will be double that. This is 16m, which is four times the minimum turning radius.
If this is done above, there will be a delay in steering which is practically useless when cornering, and conversely, "/so
This range was determined because if it were doubled to 8 mm or less, it would take too much time to calculate the current position, resulting in a delay in steering.

Further, the point sequence of each point at a predetermined interval determined as described above is determined such that the radius of curvature of a circle determined by three adjacent points in the point sequence is at least larger than the above-mentioned minimum turning radius. It is preferable. Note that the minimum turning radius at which the vehicle can turn without skidding increases as the speed increases, so the intervals between each point during high-speed driving need to be longer than when driving at low speeds; The radius of curvature of the circle defined by three adjacent points at the time also needs to be larger than during low-speed operation.

As shown in 51C1 above, it is assumed that the current position and traveling direction of the vehicle can be measured in real time, and when the planned travel route of the vehicle is taught as a target point sequence, the point tracking method follows the given point sequence. The steering is controlled by giving the steering angle command as follows.

Here, the above-mentioned steering angle command will be explained using a widely used expression method (Fig. 1) in which a four-wheeled vehicle is represented by an equivalent two-wheeled vehicle.

Now, the coordinates of the steering wheels of the vehicle are T (zt, yt)
, the coordinates of the target point are P (sp, yp), then the angle α between the X axis and the line segment PT is K as shown in the following equation.

Therefore, if the direction of travel of the vehicle is ψt, the steering angle command θ can be expressed by the following equation: θ=α−ψ.

Therefore, the current position (st, yt) of the vehicle and the traveling direction ψt
Observe the target point P (xpe
It is possible to obtain the necessary steering angle command θ that follows yp ).

However, in reality, due to steering characteristics, external disturbances, and other factors, the vehicle may not be able to reach the target point, or even if it does reach it, it will meander. Therefore, in order to solve this problem, the following two methods are used.

First, a certain range is given to the target point, and when a vehicle enters this range, it is assumed that the target point has been reached, and the next point is set as a new target point. Specifically, the second
As shown in Figure 5, the range of target points is set within a circle of radius ratio with target point P as the center, and the distance a between target point P and the current position T of the vehicle is calculated. Also small
If so, it is assumed that the target point has been reached.

2nd K: If the vehicle passes through the target point without reaching the range in which it is considered to have reached the target point, the next point from the time of passing the target point is set as a new target point. Here, the determination of when the vehicle passes the target point is as follows.

As shown in FIG. 3, the distance 'trat-s to the target point P at each vehicle position is calculated by setting the vehicle's current position Tt and the position a unit time ago as Tt-H, and then calculating the distance 'trat-s' to the target point P for each vehicle position, and using the following equation, at >at-r ・The time point when ◆+(4) is established is determined as the time point when the target point is passed.

Above 1. By determining a new target point using the second method, for example, even if the steering wheel is taken off due to an uneven road surface or the driver has detoured from the predetermined route due to an obstacle, the user can return to the planned travel route. It is possible to do so.

Next, the above method will be explained using the flowchart shown in FIG.

First, step 10) measures the current position Tt of the vehicle.
The distance at between the measured current position Tt and the target point P is calculated (step 11).

Next, it is determined whether the distance at calculated above is smaller than a predetermined radius R (step 12).

When a t < H, it is assumed that the target point PK has been reached, and the process moves to step 13. In step 13, the next point in the sequence of points given as the planned travel route is set as a new target point, and the process returns to step 10. When at≧normal, K has not reached the target point P, so the process moves to step 14.

Step 14 determines whether at is greater than at-1 a unit time ago. a t) a i1 when t-1
Since the vehicle is moving away from the target point P, this point is determined to be the point in time when the vehicle has passed the target point P, and the process moves to step 13. When at≦at-, the vehicle is approaching the target point P, so the process moves to step 15. Note that when the distance at is calculated for the first time after setting a new target point, there is no at before the unit time, so step 14 is skipped.

Step 15 is a steering angle command θ based on the above equation (3).
is calculated, and step 16 outputs a steering angle command to the steering device.

Then, rewrite at to at-1 (step 17),
After the unit time Δt has elapsed, the process returns to step 10.

FIG. 5 is a graph showing the results of applying this control method to a four-wheeled vehicle and actually driving the vehicle. In the figure, the actual driving route shown by the solid line represents the locus of the center point of the line segment connecting the left and right front wheels. In addition, the planned travel route was set as a straight line and a circular arc with a radius of 6 m, and the interval between target points was 59 cm. In addition, to make the drawing easier to read, the target point is set to 2.
Displayed at m intervals.

The vehicle is a four-wheel electric vehicle with front wheel steering and rear wheel drive, with a wheelbase of 2.13 m. A gyro compass is used to detect the direction of the vehicle, and the current position of the vehicle is obtained from the travel distance obtained from pulse encoders attached to the wheels and the direction of travel of the vehicle. Further, the maximum turning angle of the steering wheels is 30°. The driving experiment was conducted on an asphalt road surface, and the vehicle speed was 4 km/h.

Although the sampling time was controlled every 130 m sec according to the response of the steering system, sufficient guidance accuracy could be obtained as shown in the figure.

The calculation time can be realized in assembler in 10m5ec. Therefore, the remaining 120 m5ec can be used for other control operations, such as obstacle sensor control, self-diagnosis function, or man-machine interface function.

The method of the present invention is applicable not only to four-wheeled vehicles, but also to tricycles, two-wheeled vehicles, crawler vehicles, omnidirectional vehicles, six-wheeled vehicles, bipedal walking machines, multi-legged walking machines, and any other unmanned moving machines. It can also be applied to things.

〔Effect of the invention〕

As explained above, according to the present invention, when a planned travel route is taught as a sequence of points, updating of a target point from a point in the sequence of points to the next point is performed extremely smoothly,
Never lose sight of your target location. Conversely, even if the unmanned guidance machine does not reach the target point accurately due to steering delays or disturbances, the target point will be updated reliably.
The degree of freedom in assigning target points increases. For example, when accurately following a planned travel route that includes a curved route, it is preferable that the interval between target points be as short as possible within the range that can be processed, but if this interval is too short, the unmanned mobile machine will be delayed in its steering. Even if you cannot reach the target point due to reasons such as this, you will not lose sight of the target point.

[Brief explanation of the drawing]

Figure 1 is a diagram used to explain how to obtain a steering angle command in the point tracking method, Figures 2 and 3 are diagrams used to explain the method of the present invention, and Figure 4 is a diagram used to explain the method of the present invention. FIG. 5 is a flowchart showing an example of the processing procedure of the method, FIG. 5 is a graph showing the contents of an experiment using the method of the present invention, and FIG. 6 is a diagram used to explain the conventional point tracking method. Hibiki+1 Applicant's agent Takahisa Kimura ・i, -,
+ Figure 1 Figure 2 Figure 3 Figure 4

Claims (4)

[Claims] (1) Teach the unmanned mobile machine a planned travel route as a series of points on the planned travel route, and while measuring the current position of the unmanned mobile machine, the unmanned mobile machine moves to each of the taught points. In the method of guiding the unmanned mobile machine to follow the unmanned mobile machine sequentially, the distance between the current target point and the current position of the unmanned mobile machine is calculated one after another among the points taught as the point sequence, and the distance is calculated. A method for guiding an unmanned mobile machine using a point following method, characterized in that when the distance becomes less than a certain distance or when the distance gradually increases, the next point in the series of points is set as a new target point. (2) The interval between the points at each point is 1/5 of the minimum turning radius at which no sideslip occurs, depending on the speed at which the unmanned mobile machine travels through each point on the planned travel route.
A method for guiding an unmanned mobile machine using a point tracking system according to claim (1), wherein the length is 0 to 4 times longer. (3) The point sequence at each point is such that the radius of the circle determined by three adjacent points in the point sequence is the minimum turning point at which sideslip will not occur depending on the speed at which the unmanned mobile machine travels through the point. A method for guiding an unmanned mobile machine using a point tracking method according to claim (1), wherein the point tracking method is taught to be larger than the radius. (4) The method for guiding an unmanned mobile machine using a point following method according to claim (1), wherein the certain distance is a distance at which the unmanned mobile machine can be considered to have reached the current target point.