JPS6326891B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle running control system that controls acceleration and deceleration of a following vehicle so that the distance between two vehicles running one after the other is maintained at a substantially constant value.

Systems are being developed in which vehicles are operated unmanned to transport people or cargo from station to station. In order to increase the transport efficiency of the system, it is preferable to run a large number of vehicles at the same time with as small a distance as possible between them. However, when the distance between vehicles is reduced and the number of vehicles operating simultaneously is increased, if all these vehicles are centrally controlled at a center, a huge amount of data must be processed in a short period of time, and the control processing unit The problem is that as the size of the equipment increases, equipment costs and maintenance costs increase. Therefore, we decided to run a large number of vehicles as one formation without physically linking them, control the running of only the leading vehicle of each formation at the center, and maintain a nearly constant distance from the preceding vehicle for the following vehicles. It has been considered to control the traveling speed of each vehicle independently to reduce the burden on the control device at the center.

In such a travel control system, it is necessary to accurately and continuously measure the inter-vehicle distance. The sing-around method is a method for accurately and continuously measuring the distance between vehicles. The sing-around method involves constantly repeating the transmission and reception of ultrasonic waves between two vehicles in front of each other, and measures the inter-vehicle distance based on the time from transmission to reception of the ultrasonic waves.

If such a method of measuring the distance between vehicles using ultrasound is adopted, there is a possibility that the ultrasound waves will not be received due to fluctuations in the ultrasound waves or attenuation of the ultrasound waves as the distance between vehicles increases. . If ultrasonic waves are not received for a long time, inter-vehicle distance measurement data cannot be obtained, or even if it is obtained, the inter-vehicle distance measurement result will be incorrect, indicating that the inter-vehicle distance is large. The above-mentioned speed control system operates to keep the following distance almost constant, so if the following distance measurement data is not obtained, it may become impossible to control the driving of the following vehicle, or the measurement result may indicate that the following distance is large. In such a case, speed control is performed to shorten the distance between vehicles, and there is a risk that the preceding vehicle and the following vehicle will collide.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle running control system that can prevent vehicle collisions and the like even when ultrasonic waves transmitted and received between two vehicles are not received.

Embodiments of the present invention will be described in detail below with reference to the drawings.

Figure 1 shows a transportation system in which a large number of vehicles are run as one formation without being physically connected, the leading vehicle of each formation is controlled at a center, and the following vehicles are kept at a constant distance from the preceding vehicle. The figure shows the case where each vehicle is independently controlled while maintaining the same. The first vehicle 61h among the vehicles in one formation receives a command signal from a center (not shown),
A communication device 62 that transmits necessary data such as traveling speed and position to the center, and a vehicle control device 63 that controls the running of the leading vehicle based on commands from the center are mounted. In addition, all other vehicles 61 and 61e other than the leading vehicle 61h are equipped with acceleration/deceleration control devices 6 that control the running of the vehicles so as to maintain a constant inter-vehicle distance from the preceding vehicle.
5 is listed. And all vehicles 61
Inter-vehicle distance measuring circuits 64a, 64b are provided in pairs for each of the preceding and following vehicles. First and last vehicles 61h, 61
e includes one inter-vehicle distance measuring circuit 64a or 6
4b is not necessarily required.

The inter-vehicle distance measuring circuits 64a and 64b measure the inter-vehicle distance between successive vehicles using ultrasonic waves, and as shown in FIG. , 71, respectively. Transmission/reception circuits 66, 70
includes transmitters 68 and 73 that transmit ultrasonic waves toward opposing vehicles 61b and 61a, and receivers 69 and 72 that receive ultrasonic waves sent from opposing vehicles 61b and 61a, respectively. ing. Also,
The measuring circuit 64b is provided with an inter-vehicle distance display device 81. These measuring circuits 64a and 64b form a pair to constitute an inter-vehicle distance measuring device.

An ultrasonic wave having a frequency f1 (for example, 25 KHz) is transmitted from the transmitter 68 of one vehicle, for example, the following vehicle 61a, toward the preceding vehicle 61b. When this ultrasonic wave is received by the receiver 72 of the preceding vehicle 61b, the transmitting/receiving circuit 70 immediately transmits the frequency f2.
(for example, 20 KHz) is transmitted from the transmitter 73 toward the following vehicle 61a. This frequency f2
When the ultrasonic wave is received by the receiver 69 of the following vehicle 61a, the transmitting/receiving circuit 66 similarly immediately transmits the ultrasonic wave of frequency f1. In this way, the ultrasonic waves of frequencies f1 and f2 are transmitted to both vehicles 61a,
It constantly goes back and forth between 61b and 61b.

The reason why ultrasonic waves having different frequencies f1 and f2 are used is to prevent mutual interference.

If we ignore the time delay from receiving ultrasonic waves to transmitting them by the transmitting/receiving circuits 66, 70, the ultrasonic transmission period TS by these transmitting/receiving circuits 66, 70 is:
This is equal to the time required for the ultrasonic waves to travel back and forth between the vehicles 61a and 61b. Therefore, the preceding vehicle 61b
The inter-vehicle distance L between the following vehicle 61a and the following vehicle 61a is the wave transmission period.
Using TS, it is expressed as L=TS/2・W (1). Here, W is the speed of sound. Arithmetic circuits 67 and 71 measure the wave transmission period TS and calculate inter-vehicle distance L based on the above equation. Both vehicles 61a,
The inter-vehicle distance can be accurately measured by the measuring device, even when vehicle 61b or one of the vehicles is stopped, or when both vehicles 61a and 61b are running.

In addition, when the ultrasonic wave is received by the receiver 69 of the measurement circuit 64a, the ultrasonic wave is not immediately transmitted from the transmitter 68, but the ultrasonic wave is transmitted by the transmitter/receiver circuit 66 at a constant cycle. It's okay. Also,
The measuring circuit 64b does not necessarily need to be provided with the arithmetic circuit 71. The distance may be measured by receiving reflected waves of ultrasonic waves transmitted toward the vehicle in front.

Furthermore, in FIG. 2, the acceleration/deceleration control station 65 includes a central processing unit (hereinafter referred to as CPU) 74. This CPU 74 has an interface 78 as input devices including an inter-vehicle distance measuring circuit 64a and a vehicle speed detector 75 for measuring the traveling speed of the vehicle.
Further, as output devices, an acceleration/deceleration drive device 80, a vehicle speed display device 82, an inter-vehicle distance display device 83, and an acceleration/deceleration display device 84 are connected via an interface 79. CPU7
4 executes processing to be described in detail later based on input signals from the inter-vehicle distance measurement circuit 64a and the vehicle speed detector 75, and outputs an acceleration signal, deceleration signal, neutral signal or emergency stop signal, and a drive motor control signal. Outputs control voltage signal. Acceleration/deceleration drive device 8
0 drives a travel drive motor (not shown) in response to these acceleration, deceleration signals, neutral signals, emergency stop signals, and control voltage signals. Also CPU74
is equipped with a ROM 76 that stores execution programs and a RAM 77 for various data. In this embodiment, acceleration, deceleration, or speed maintenance is determined by the acceleration signal, deceleration signal, and neutral signal.
Acceleration, deceleration, or speed maintenance may be determined by using one main line and outputting control voltages divided into positive and negative voltages.

Now, the preceding vehicle and the following vehicle have a predetermined distance between them.
The conditions for maintaining LO and not colliding with each other are expressed by the following equation.

[V2]=V1+K・LD=V2+VD+K・LD ……(2) VD=V1−V2 ……(3) LD=L−LO ……(4) Here, [V2]; Target speed of the following vehicle V1; Leading vehicle Vehicle speed V2; Speed L of the following vehicle; Actual inter-vehicle distance LO; Inter-vehicle distance to be maintained (for example, 2 to 5 m) K: Constant From equations (2), (3) and (4), the target speed of the following vehicle It can be seen that [V2] is determined by the speed (V2), relative speed (VD), and relative inter-vehicle distance (LD) of the following vehicle. Here, the speed of the preceding vehicle (V1)
If it is assumed that is constant (V1 = V2), there is no need to consider relative velocity (VD). In this embodiment, acceleration/deceleration control of the following vehicle is performed based on the relative inter-vehicle distance (LD).

Incidentally, the acceleration/deceleration (α) of the vehicle is related to the traction force (F) and running resistance (R) acting on the vehicle, and the traction force (F) depends on the rotational torque (T) of the running drive motor. If the inertial weight of the vehicle is (M), the acceleration/deceleration (α) is expressed by the following equation.

α=F−R/M=a・T−R/M……(5) Therefore, the torque (T) is T=b・α+cR...(6) becomes. Here (a), (b), and (c) are constants.

Based on the above, in this embodiment, the torque (T) of the drive motor of the following vehicle is controlled based on the relative inter-vehicle distance (LD), and the torque (T) is
Assume that it is approximately a straight line as shown in the graph in the figure. Figure 3 shows torque (T) and relative distance between vehicles (LD)
This approximates the relationship between In Fig. 3, when the relative inter-vehicle distance (LD) is L ₄ > LD≧O, the acceleration torque (Ta) increases linearly as the relative inter-vehicle distance (LD) increases, and when LD≧L4 Acceleration torque (Ta) is kept at a constant value (T160). Furthermore, when O>LD≧−L6, the deceleration torque (Td) increases in the negative direction as the relative inter-vehicle distance (LD) decreases (increases in the negative direction),
When -L6>LD, the deceleration torque (Td) increases rapidly due to sudden stop and becomes -T300. The reason why the torque (T) is not O when LD=O is to overcome running resistance.

It should be noted that the values of relative inter-vehicle distance, torque, and acceleration/deceleration voltage (to be described later) are represented by symbols L, T, Va, and Vd with a suffix attached, and the larger the suffix, the larger the value.

In the acceleration/deceleration processing described later, in order to simplify the process of calculating torque (T) from the relative inter-vehicle distance (LD) using Fig. 3, the relative inter-vehicle distance is stored in advance in the RAM 77 as shown in Fig. 5. A (LD)-torque (T) table is provided.
In this table, the relative inter-vehicle distance (LD) is divided into predetermined ranges, and one torque (T) corresponds to each relative inter-vehicle distance (LD) within each of these ranges. It goes without saying that the torque (T) may be determined by direct calculation using the linear equation shown in FIG. 3 instead of the table.

FIG. 4 shows an example of characteristics of a vehicle's travel drive motor. The horizontal axis is the speed of the vehicle (Km/H), and the vertical axis is the generated acceleration torque (Ta) and deceleration torque (Td). The acceleration/deceleration drive device 80 controls the drive motor based on a control voltage and acceleration/deceleration signals, and FIG. 4 shows some typical control voltages (acceleration voltage (Va), deceleration voltage (Va) ) are shown. As is clear from this graph, even if the control voltage is constant, the generated torque changes depending on the speed.
This change is particularly significant in deceleration torque. Therefore, an appropriate speed range (0 to 35 and 35 to 45 km/h for acceleration, 0 to 15, 15 to 45 km/h for deceleration)
25, 25-35 and 35-45Km/H), create a calculation table for acceleration and deceleration voltages (Va) (Vd) necessary to obtain acceleration and deceleration torques (Ta) (Td).
Store it in an appropriate area of RAM77. Acceleration torque (Ta) - acceleration voltage (Va) table is No. 6
In the figure, a deceleration torque (Td)-deceleration voltage (Va) table is shown in FIG. 7, respectively. In these tables, acceleration and deceleration torque (Ta) (Td)
is divided into predetermined ranges, and one acceleration and deceleration voltage (Va) (Vd) corresponds to each torque within these ranges.

Furthermore, as shown in FIG. 8, the RAM 77 has an area (M1) for storing the vehicle speed calculated based on the output of the vehicle speed detector 75, and an area (M1) for storing the current inter-vehicle distance calculated based on the output of the inter-vehicle distance measuring circuit 64a. An area (M2) for storing previous data is provided.

Referring to FIG. 9, the vehicle speed calculation process is performed by the following procedure. Speed detector 75 consists of a rotating transducer mounted on a rotating part of the vehicle and outputs a series of pulse trains at a frequency proportional to the vehicle speed. The CPU 74 counts these pulses for a certain period of time and calculates the vehicle speed based on this counted value (step (1)). The calculated vehicle speed is then stored in the storage area (M1) of the RAM 77 (step (2)) and displayed on the speed display device 82 (step (3)). In the calculation process of step (1),
An average value of two or four times, etc., may be calculated.

In the calculation process of the inter-vehicle distance (L), referring to FIG. The time is added and the correction result is set as the inter-vehicle distance (L) (step (11)), and the process proceeds to step (12) to check whether there is any data loss (step (12)). Data loss in this case refers to a case where ultrasound is not received even after a certain period of time has passed after ultrasound transmission.
Since ultrasonic waves are attenuated by absorption and scattering by air, there is a limit to the range that ultrasonic waves can reach. If ultrasonic waves are not received for a time equal to or longer than this limit distance after ultrasonic wave transmission, or if ultrasonic waves are received but more than the above-mentioned time has elapsed, data is lost. If the data is not missing, proceed to step (13), read the previous inter-vehicle distance data from the area (M2), and calculate the difference with the current inter-vehicle distance data calculated in step (11). Then, it is checked whether this difference is smaller than a predetermined value (step (14)). Since the speeds of the two vehicles in succession change continuously, the difference between the previous and current inter-vehicle distance data should not be that large. Therefore, if the above-mentioned difference is greater than a predetermined value, it is assumed that there was an error in the inter-vehicle distance measurement, and the data is determined to be missing. If the data is not missing, the data in the current following distance storage area is transferred to the previous following distance storage area, and the data calculated in step (11) is stored in the current following distance storage area (step (15)). The distance is displayed on the distance display device 83 (step (16)), and the process ends. If data is missing in steps (12) and (14), a deceleration signal and an emergency stop signal are output to prevent the vehicle from running out of control (step (17)).
In the inter-vehicle distance calculation process in step 11, the average value may be calculated multiple times.

The acceleration/deceleration control process is executed according to the procedure shown in FIG. 11 at every sampling time (for example, 0.1 seconds). First, the current following distance (L) is read from the area (M2) (step (21)), and this following distance (L) and the target following distance (LO) previously stored in a predetermined area (not shown) are used. Then, the relative distance between vehicles (LD) is calculated (step (22)).
Then, refer to the LD-T table (Fig. 5) to find the torque (T) (step (23)), read out the vehicle speed from the area (M1) (step (24)), and calculate the torque (T). ). If the torque (T) found in step (23) is positive, it is acceleration torque (Ta), and if negative, it is deceleration torque (Tb).

First, check whether the torque (T) exceeds T20 (step (25)), and if it does, it is necessary to accelerate and move to step (28). If the torque (T) is less than T20, proceed to step (26) and check whether the torque (T) exceeds -T1. If the torque (T) exceeds -T1 and is less than T20, the process proceeds to step (34), and if it is less than -T1, the process proceeds to step (27). In step (27), it is further determined whether the torque (T) exceeds -T130, and if the torque (T) is less than -T130, the process moves to step (45), and if the torque (T) exceeds -T130 and - If it is below T1, move on to step (36).

In step (28), the vehicle speed read in step (24) is used to check whether the vehicle speed is 45 km/h or more. If it is less than 45 km/h, the process proceeds to step (29) to perform acceleration processing. Execute. First, an acceleration signal is output (step (29)), and the vehicle acceleration is judged again (step (30)). If the vehicle speed is less than 35Km/H, Ta-Va corresponds to a large voltage (Va) for a large torque (Ta).
With reference to Table 1 (Figure 6a), the acceleration voltage (Va) is determined from the acceleration torque (T), that is, the acceleration torque (Ta) (step (31)), and the 35Km/
If H or higher, Ta-Va table 2 (Figure 6b)
Find the accelerating voltage (Va) with reference to (step (32)).The reason for using two Ta-Va tables is
As shown in Figure 4, at high speeds, only a low torque can be obtained even if the same voltage (Va) is applied. Next, the obtained acceleration voltage (Va) is output as a control voltage (step (33)) and the process is completed.

If the vehicle speed exceeds 45 km/h, for example, even if the torque (T) exceeds T20, there is no need to accelerate any further (assuming the target speed of the vehicle is 40 km/h), and neutral processing is performed. Move to. At step (26), torque (T) exceeds -T1 and
If the score is T20 or below, it will also be treated as neutral. In these cases, first a neutral signal is output (step (34)), and the control voltage is set to 0 (step (35)).

If the torque (T) exceeds -T130 and is below -T1, deceleration processing is performed, in which a deceleration signal is first output (step (36)), and then the vehicle speed is determined (steps (37) to (39)). )). If the vehicle speed is less than 15Km/H, refer to Td-Vd table 1 (Figure 7a) (step (40)); if the vehicle speed is 15Km/H or more and less than 25Km/H, refer to Td-Vd table 2 (Figure 7a). 7b)) (Step (41), 25Km/H or more 35Km/H
If less than Td-Vd table 3 (Figure 7c)
(Step (42)), and in the case of 35Km/H or more, refer to Td-Vd table 4 (Figure 7d) (Step (43)) to determine the torque (T) for deceleration, that is, the deceleration torque. The deceleration voltage (Vd) is obtained from (Ta), this deceleration voltage (Vd) is output (step (44)), and the process ends.

If the torque (T) is less than -T130, a deceleration and emergency stop signal is output (step (45)).

As described above, the present invention includes an ultrasonic transceiver device that is mounted on each of at least two vehicles in succession and includes an ultrasonic transducer, and a vehicle distance measurement circuit that is mounted on at least one vehicle. The ultrasonic transmitting/receiving device of at least one of the vehicles immediately transmits the ultrasonic waves toward the other vehicle upon receiving the ultrasonic waves transmitted from the other vehicle, and the inter-vehicle distance measuring circuit The distance between two vehicles in succession is measured based on the time it takes for the ultrasonic waves to travel back and forth between the two vehicles, and this measured distance between vehicles is used as basic data for vehicle travel control. In the driving control system, when ultrasonic waves are not received within a certain period of time after ultrasonic waves are transmitted by the ultrasonic transmitter/receiver, and when inter-vehicle distance measurement data is obtained from the inter-vehicle distance measurement circuit, the previous inter-vehicle distance is determined. The difference between the distance measurement data and the current inter-vehicle distance measurement data is a given value corresponding to the allowable amount of change in the inter-vehicle distance that occurs between the two vehicles during the inter-vehicle distance measurement time interval by the above-mentioned inter-vehicle distance measurement circuit. The present invention is characterized by comprising a control device that generates an output that decelerates the vehicle as a data loss when the vehicle exceeds the limit. If ultrasonic waves are not properly transmitted and received between vehicles in front of one another due to attenuation due to absorption and scattering of ultrasonic waves by the air, the vehicle will decelerate, resulting in runaway vehicles, vehicle collisions, etc. can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of the transportation system, Fig. 2 is a configuration diagram of a vehicle distance maintenance device, Fig. 3 is a graph showing the relationship between torque and relative inter-vehicle distance, and Fig. 4 is a graph showing the characteristics of the travel drive motor. Figure 5 shows the LD-T table stored in RAM, Figure 6 shows the Ta-Va table stored in RAM, and Figure 7 shows the Td-T table stored in RAM.
FIG. 8 is a diagram showing the data storage area in the RAM, FIG. 9 is a flow chart showing the procedure for calculating vehicle speed, and FIG. 10 is a flow chart showing the procedure for calculating the inter-vehicle distance. FIG. 11 is a flow chart showing the procedure of acceleration/deceleration control. 61, 61a, 61b, 61h, 61e... Vehicle, 64a, 64b... Inter-vehicle distance measuring circuit, 6
6,70...Ultrasonic transmitting/receiving circuit, 67,71...
Inter-vehicle distance calculation circuit, 68, 73... Transmitter, 6
9, 72...Receiver, 74...CPU, 80...
Acceleration/deceleration drive device.

Claims (1)

[Claims] 1. An ultrasonic transmitter/receiver device including an ultrasonic transducer and mounted on each of at least two vehicles in front and behind each other, and an inter-vehicle distance measuring circuit mounted on at least one vehicle, The ultrasonic transmitting/receiving device of at least one of the vehicles immediately transmits the ultrasonic waves toward the other vehicle upon receiving the ultrasonic waves transmitted from the other vehicle, and the ultrasonic wave is transmitted by the inter-vehicle distance measuring circuit. Vehicle travel control in which the inter-vehicle distance between two vehicles in succession is measured based on the time it takes for the sound waves to travel back and forth between the two vehicles, and the measured inter-vehicle distance is used as basic data for vehicle travel control. In the method, after the ultrasonic wave is transmitted by the ultrasonic transmitter/receiver,
When ultrasonic waves are not received within a certain period of time, and when inter-vehicle distance measurement data is obtained from the inter-vehicle distance measurement circuit, the difference between the previous inter-vehicle distance measurement data and the current inter-vehicle distance measurement data is determined as the above-mentioned inter-vehicle distance. A control device is provided that generates an output to decelerate the vehicle as a data loss when a predetermined value corresponding to a permissible change in the inter-vehicle distance occurring between two vehicles during the inter-vehicle distance measurement time interval by the measurement circuit is exceeded. A vehicle running control system characterized by: