JPH0353643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a turning control method for a two-wheel differential drive type unmanned vehicle.

[Conventional technology]

In general, a two-wheel differential drive vehicle is one in which the vehicle is steered by the difference in rotation between two independent drive wheels 1 and 2, as shown in Figure 1, and the two wheels rotate at the same speed but in opposite directions. By doing so, you can perform comfortable turning.

Conventionally, when this type of unmanned vehicle travels along a running route A and transfers to a running route B that intersects this running route A, the center point C of the line segment connecting the two drive wheels 1 and 2 is The vehicle is stopped when it coincides with the intersection O between A and B, and the left and right drive wheels 1 and 2 are rotated in opposite directions at the same speed to perform a turn on the spot.

However, with this method, the vehicle must be stopped accurately when the turning center C of the vehicle coincides with the intersection O, and the turning must be stopped accurately at a set turning angle. Depending on the unevenness of the road surface, the accuracy of the vehicle's brakes, etc., stable turns may not always be possible.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a turning control method for an unmanned vehicle that can perform stable and highly accurate turning.

[Means and actions for solving problems]

According to this invention, the running path A that generates the induced magnetic field
In an unmanned vehicle that turns by rotating drive wheels that rotate forward and reverse independently on the left and right sides in mutually opposite directions when transferring from the running track A to a running track B that generates an induced magnetic field that intersects the running track A at a certain angle, First and second sensors that detect magnetic fields with directionality in the longitudinal direction of the vehicle are arranged at fixed distances in front and rear of the vehicle, respectively, from the center point of the line segment connecting the two drive wheels. When changing from track A to track B while traveling on track A, the output of the first sensor is used as a positive speed command for one drive wheel, and the output of the second sensor is used as a positive speed command for the other drive wheel. By giving this as a negative speed command, it is possible to accurately complete a center turn on the running path B.

〔Example〕

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

In Fig. 2, path A carries an alternating current of i _A = I _A · sinω _A t, and path B carries an alternating current of i _B = I _B · sinω _B
An alternating current of t is flowing through each of them, and each generates an induced magnetic field. Further, the running route A and the running route B intersect at a certain angle (here, 90°).

The unmanned vehicle has left and right drive wheels 1 that rotate forward and reverse independently.
and 2, and by independently controlling the speed of these drive wheels 1 and 2, driving steering and turning are performed.

The sensors 10 and 11 each detect the magnetic field from the running path with directionality in the width direction.
A travel steering command is generated so that the running route (here, running route A) is located in the center of the sensors 10 and 11.
Note that since this type of steering method is commonly used, detailed explanation will be omitted here.

Sensors 12 and 13 each detect the magnetic field from track B with directionality in the longitudinal direction of the vehicle. The sensor 13 is spaced apart from the center point C by a distance l. The sensors 14 and 15 are for phase detection of the signals of the sensors 13 and 12, and are located at a distance l from the center point C, with the sensor 12 and δ (0<δ
<90°). Note that FIG. 3 is a perspective view showing the positional relationship of the sensors 10 to 15.

Next, a case will be described in which an unmanned vehicle uses sensors 10 and 11 to travel along route A, turns to the right near the intersection of routes A and B, and transfers to route B.

Now, as shown in Figure 4, the unmanned vehicle is traveling on route A.
When the sensor 12 detects, based on the magnetic field detection level from the running route B, that the sensor 12 has reached the vicinity of the intersection with the running route B, the sensors 10 and 11
The steering of the vehicle is prohibited, and turning control by the sensors 12 and 13 is started. sensor 1
Filters 2 to 15 are provided so that only the magnetic field having an angular velocity ω _B from the running path B can be detected. Further, the position at which the turning control is started is set such that the distance between the center point C of the vehicle and the intersection at that time is smaller than at least one-half length W of the tread.

Now, when the vehicle reaches the turning control start position, the outputs of the sensors 12 and 13 are phase-detected by the output of the sensor 14, and the detected analog signal of the sensor 12 is the positive speed of the left driving wheel 1. The analog signal from the sensor 13 is used as a negative speed command for the right drive wheel 2.

At this point, the output V _a from the sensor 12 and the output V _b from the sensor 13 have a relationship of V _a > V _b , and the drive wheels 1 and 2 are rotating in opposite directions, so the vehicle is centered at the center of the vehicle body. A right turn is made around the turning center on the line segment connecting point C and drive wheels 2. The drive wheels 1 rotate at high speed and the drive wheels 2 rotate at low speed and in opposite directions, causing the vehicle to turn, causing the sensor 12 to move away from the road B and the sensor 13 to approach the road B (see FIG. 5). Therefore, the rotational speed difference between the drive wheels 1 and 2 gradually decreases, and the turning center of the vehicle body approaches the vehicle body center point C, approaching comfortable turning.

The turning center of the vehicle coincides with the vehicle body center point C when the sensors 12 and 13 are at the same distance from the running road B, and at this time the vehicle body center point C must be on the running road B. . When the vehicle body center point C is on the running track B and both sensors 12 and 13 are on the running track B, the magnetic field from the running track B is
Since it is perpendicular to the direction of sensors 12 and 13,
The output from 3 will be 0. Therefore, this turning operation is converged when the vehicle correctly transfers onto the running path B (see FIG. 6).

In addition, since the sensor 14 is used to detect the phase of the outputs of the sensors 12 and 13, if the sensors 12 and 13 pass through the running path B at the end of the turn, the positive and negative of the output signals will be reversed. , acts to correct excessive turning.

Note that when turning left, the sensor 15 is used to phase-detect the outputs of the sensors 12 and 13, and the output of the sensor 12 is used as a positive speed command for the right drive wheel 2.
The output of the sensor 13 may be used as a negative speed command for the left driving wheel 1.

FIG. 7 is a block diagram of an apparatus for implementing the method of the invention. In the figure, a left/right turn switching signal S indicating whether to turn left or right at the next intersection is applied to an input terminal 20 based on a travel route stored in advance in a central processing unit, external memory, etc. ing. Of course, this also includes going straight at an intersection.

This left/right turning switching signal S is applied to switching circuits 21 and 22, respectively. The switching circuit 21 is
When the switching signal S indicates a right turn, the output of the sensor 14 is selected and outputted to the phase detection circuits 23 and 24 as a reference signal when phase detecting the outputs of the sensors 12 and 13, and the switching signal S indicates a left turn. When the time is indicated, the output of the sensor 15 is selected and outputted to the phase detection circuits 23 and 24.

The phase detection circuit 23 receives the output from the sensor 12,
The phase detection circuit 24 performs phase detection on the output from the sensor 13 using the reference signal from the switching circuit 21, and outputs the detected signal to the switching circuit 22, respectively.

When the input switching signal S indicates right turn, the switching circuit 22 outputs the signal applied from the phase detection circuit 23 to the motor 25 as a positive speed command, and outputs the signal applied from the phase detection circuit 24 to the motor 25 as a negative speed command. 26, and when the input switching signal S indicates a left turn, the signal applied from the phase detection circuit 23 is outputted to the motor 26 as a positive speed command, and the signal applied from the phase detection circuit 24 is outputted as a negative speed command. Output to motor 25.

As a result, drive wheels 1 and 2 are driven by motor 25.
and 26, the motors 25 and 26 rotate in opposite directions, and at a speed corresponding to the magnitude of the speed command input to the motors 25 and 26.

Next, the dynamic characteristics of an unmanned vehicle using the turning control method of the present invention will be considered.

When the current in path B is I and the position of sensor 12 with respect to path B is as shown in FIGS. 8 and 9, the output V of sensor 12 that detects the magnetic field in path B is expressed by the following formula, V∝hI /α ² +h ² cos ……(1) It can be expressed as follows. Now, when the vehicle body is in the position shown in Fig. 10 with respect to tracks A and B, when the magnetic field of the current flowing in track B is detected by the sensors 12 and 13, the outputs V _a and V _b are calculated by the above formula (1). From this, V _a =AIh/(lcos−y) ² +h ² cos ……(2) V _b =AIh/(lcos+y) ² +h ² cos ……(3). However, A is a proportionality constant.

The method of the present invention controls the left and right drive motors of the vehicle body using the outputs obtained from equations (2) and (3) above. In the case of a right turn, control is made so that V _a obtained from equation (2) becomes the speed of the left drive motor, and the negative value of V _b - V _b obtained from equation (3) is the speed of the left drive motor. The speed of the drive motor is controlled so that the speed of the drive motor is as follows.

The speed of the left motor 25 is v _aThe speed of the right motor 26
If v _b , then v _a =V _a v _b =−V _b ...(4). Further, the speed v _c of the center point C of the vehicle is v _c = v _a + v _b /2 (5). As shown in Fig. 10, if the travel path B is the x-axis and the travel path A is the y-axis, d _y /d _t = v _a +v _b /2cos... (6) d _y /d _t = v _a +v _b / 2sin...(7). On the other hand, the turning radius R is R cos = d _y / d...(8) Furthermore, since R is equal to the length between the position where the vehicle's tread 2w is internally divided by the speeds V _a and V _b and the center point C, R=wv _a +v _b /v _a −v _b (9). From equations (6), (8), and (9) above, d=v _a −v _b /2w dt ...(10), and equations (2), (3), (4), and (10) From this, we obtain d/dt=AIh/2wcos[1/lcos−y) ² +h −1/(lcos+y) ² +h ² ]...(11). By analyzing this using the Runge-Kutzta method, it is possible to obtain, and at the same time, x and y can be obtained from equations (6) and (7).

Figure 11 shows the above analysis results, which are 0 seconds, 0.1 seconds, 0.3 seconds, 0.7 seconds from the start of the turn, respectively.
It shows the positions of drive wheels 1 and 2 after 2.0 seconds and 5.0 seconds. Further, L indicates the locus of the vehicle body center point C. The following values were used for the data in the analysis.

[AI = 80, h = 0.1m, w = 1m, l = 1m y = -0.5m = 0 degree However, at the start of the turn] As is clear from Figure 11, the center of the turn is from above the drive wheels 2 to the vehicle body. The vehicle moves to the center point C, and as the vehicle body center point C asymptotically approaches the running path B, the turning angle approaches 90°.

As a result of the analysis, it is found that it is not necessary to satisfy the important condition required for conventional center turning, that is, the condition that the vehicle must be stopped accurately when the ground turning point and the vehicle center point C coincide. In the analysis, the vehicle body center point C at the start of the turn
Although it is 0.5m off from the running path B,
After completing the turn, the vehicle is accurately on track B.

However, in the method of the present invention, since the speed of the driving wheels approaches 0 as the end of the turn approaches, it theoretically takes an infinite amount of time to complete the turn. Therefore, for practical purposes, the following measures are required.

(1) Near the end of the turn, normal steering signals from sensors 10 and 11 are added.

(2) Increase the system gain near the end of the turn. For example, the proportionality constant AI in equation (11) is defined as AI=A ₀ ×t
as a time function.

(3) Keep the speed of drive wheels 1 and 2 constant near the end of the turn.

Further, since the method of the present invention is completely symmetrical with respect to forward and backward movement, forward left and right turns and backward left and right turns can be realized equivalently.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to always perform stable and highly accurate turns regardless of the unevenness of the road surface, the stopping accuracy of the vehicle, etc. Furthermore, since the conventional step of stopping the vehicle accurately when the ground turning point and the center point of the vehicle body coincide, the time required for turning can be expected to be shortened.

[Brief explanation of drawings]

FIG. 1 is a diagram used to explain a conventional turning method for an unmanned vehicle, and FIGS. Figures 4, 5 and 6
The figures are diagrams used to explain the method of the present invention, and are vehicle state diagrams at the start of a turn, in the middle of a turn, and near the end of a turn, respectively. Fig. 7 shows an embodiment of a device for realizing the method of the present invention. The block diagram, FIGS. 8 and 9 are a side view and a plan view, respectively, used to explain the output of the sensor used in the present invention.
Fig. 10 is a diagram showing parameters for analyzing the dynamic characteristics of a vehicle using the method of the present invention, and Fig. 11 is a diagram showing parameters for analyzing the dynamic characteristics of a vehicle using the method of the present invention, and Fig. 11 shows parameters for 0 seconds, 0.1 seconds, 0.3 seconds, and 0.7 seconds from the start of a turn, respectively.
It is a figure which shows the position of a drive wheel after 2.0 seconds, 2.0 seconds, and 5.0 seconds. 1, 2... Drive wheel, 10-15... Sensor, 21,
22...Switching circuit, 23, 24...Phase detection circuit, 2
5, 26...Motor, A, B...Runway.

Claims (1)

[Scope of Claims] 1. When changing from a running path A that generates an induced magnetic field to a running path B that generates an induced magnetic field that intersects the running path A at a certain angle, drive wheels that rotate forward and reverse independently on the left and right sides are moved in opposite directions to each other. A turning control method for an unmanned vehicle that rotates and turns, the method comprising: first and second sensors that detect the magnetic field from the running path B with directionality in the longitudinal direction of the vehicle;
Disposed at a fixed distance from the center point of the line segment connecting the two driving wheels to the front and rear of the vehicle, respectively, and when changing from lane A to lane B while traveling on lane A, the first A turning control method for an unmanned vehicle, characterized in that the output of the sensor is given as a positive speed command for one drive wheel, and the output of the second sensor is given as a negative speed command for the other drive wheel.