JPH04299711A - Automatic carrier truck - Google Patents

Abstract

PURPOSE:To improve the running stability of an automatic carrier truck and also to prevent the easy derailment even at the curve parts by providing the sensors at the front and rear parts of the truck. CONSTITUTION:The sensors 3A and 3B are provided on the center position of the front and rear parts of a four-wheel, carrier truck 2 respectively. Thus the front wheels 4 are steered by the signals of the sensor 3A, and the rear wheels 5 are steered by the signals of the sensor 3B respectively. In this case, the steering value of the wheels 5 is set smaller then that of the wheels 4. Therefore the independent steering control is attained to both wheels 4 and 5 along the path of an optical reflecting tape 1 with high accuracy especially in such a case where the straight lines and curves are mixed together. Owing to this individual steering control of both wheels, the attitude of the attitude of the truck 2 much more than the wheels 4. In this respect, the steering value of the wheels 5 is reduced. So that, the running stability of the vehicle 2 is improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic transport vehicle, and more particularly to a travel path control mechanism thereof.

0002

2. Description of the Related Art FIGS. 5 and 6 show an automatic transport vehicle that uses a light-reflecting tape or magnetic tape attached to the floor surface as a travel route and automatically travels while detecting this with a sensor attached to the vehicle. In the figure, 1 is a light reflective tape, 2 is a car body,
3 is a sensor for detecting light reflective tape, 4 is a front wheel,
5 is the rear wheel. In such a device, the position of the optical reflective tape 1 is detected by the sensor 3, and the vehicle runs while steering the front wheels 4 based on this detection signal.

0003

SUMMARY OF THE INVENTION The above-mentioned prior art has the following problems. 1. There is only one sensor at the center of the truck, and the inclination of the vehicle body (parallelism between the truck and the light-reflecting tape) is unknown. 2. Because the front wheels are steered by a sensor located at the center of the bogie, the bogie meanderes significantly, and especially on curved sections, the bogie can deviate significantly from the light-reflecting tape, making it easy to derail.

SUMMARY OF THE INVENTION An object of the present invention is to provide a self-propelled carrier that has good stability during running and is less likely to derail even on curved sections.

[0005]

[Means for Solving the Problems] As shown in Fig. 1, sensors are installed at the front and rear centers of a four-wheeled vehicle, and the front wheels are controlled by the signals from the front sensors, and the rear wheels are controlled by the signals from the rear sensors. Steering at each signal. Further, at this time, the steering amount (steering angle) of the rear wheels based on the signal from the rear sensor is set to be smaller than the steering amount of the front wheels.

[0006] The truck can move forward and backward, and when moving backward, the above relationship is reversed and the steering is controlled.

[0007]

[Effect] 1. By providing sensors at the front and rear of the vehicle body, it is possible to control the steering of the front wheels and rear wheels separately. In particular, when straight lines and curved lines coexist as shown in FIG. 1, each wheel is accurately steered along the route tape. 2. By separately controlling the steering of the front wheels and rear wheels, each wheel steering changes the attitude of the truck. In particular, the steering on the rear wheel side has a large effect on the bogie attitude. Therefore, the stability during running is improved by reducing the amount of steering on the rear wheel side.

[0008]

[Embodiment] An embodiment of the present invention will be described with reference to FIG. 1
is light reflective tape, 2 is the vehicle body, 3A is the front wheel sensor, 3B
is a rear wheel sensor, 4 is a front wheel, and 5 is a rear wheel. Although this diagram shows the vehicle moving forward, it is of course possible for the trolley to move backward as well. Although not shown, a 24V battery is used to control the drive of the bogie, a DC motor provides driving force to the front and rear wheels, and separate DC motors are used to steer the front and rear wheels. As the sensors 3A and 3B, for example, a photoelectric trace sensor unit in which six reflective sensors using commercially available infrared light emitting diodes are arranged in a straight line is used. Specific examples of the amount of deviation from the light reflective tape 1, the sensor signal at that time, and the amount of steering based thereon are shown in FIG. 2 and Table 1.

In FIG. 2 and Table 1, Ph・0R, Ph
・1R, Ph・2R, Ph・0L, Ph・1L, Ph・
2L indicates a sensor, and the interval between each sensor is 30 mm pitch.

0010

[Table 1] In Table 1, 0 and 1 indicate on and off states of the sensor based on reflective tape detection, where 1 indicates on and 0 indicates off. The amount of deviation indicates the amount of deviation of the truck with respect to the reflective tape, and when the amount of deviation is small, the steering amount is small and the running speed is set to be high.

[0011] Here, α1 = 1°, α2 = 2°, α3
= 3°, α3 = 4°, α5 = 6°, and the steering amount is 20 m/min at high speed and 10 m/min at medium speed.
The vehicle was automatically run at a speed of m/min along a travel route that included both straight lines and curves with a radius of 5 m. The situation is shown in FIGS. 3 and 4. First, in Fig. 3, when the front wheels 4 are steered by the signal from the front wheel sensor 3A and the rear wheels 5 are driven in a free state, even when traveling on a straight section, the center of gravity is not in the center due to the loading position etc. A phenomenon occurred in which the ring side gradually shifted from the center position of the reflective tape. In addition, a particularly large deviation occurred in curved sections.

Next, when the front wheels 4 are steered by the signal from the front wheel sensor 3A, and the rear wheels 5 are steered by the signal from the rear wheel sensor 3B, the light reflective tape 1 is constantly detected and controlled in both straight and curved sections. Despite this, I was able to run pretty well. However, in this case, the bogie meandered, particularly due to the influence of rear wheel steering. Next, in the above-mentioned method of steering the front and rear wheels separately, if the steering amount of the rear wheels is set to about 1/2 of that of the front wheels, the bogie will run smoothly with little meandering on both straight and curved sections. I was disappointed.

Further, although this embodiment has been mainly described with respect to forward movement, good running can be achieved even in the case of reverse movement by reversing the control.

[0014]

Effects of the Invention The present invention provides an automatic transport vehicle that travels and steers on four wheels, in which sensors for detecting the travel path are installed at the front and rear of the vehicle body, and the front wheels are steered using detection signals from the front sensors. By doing so and steering the rear wheels using the detection signal from the rear sensor, the following effects can be achieved.

[0015] Since the front and rear wheels of the four-wheeled bogie are steered using separate sensor signals, the bogie can always travel precisely along the route, even if the route is a mixture of straight lines and curves. By installing sensors for controlling the steering of the front wheels and the rear wheels under the center of each wheel, it is possible to control the steering of the wheels with high precision.

By making the amount of steering of the rear wheels smaller than the amount of steering of the front wheels, the influence on the front wheels when steering the rear wheels is reduced, and the vehicle can travel along the route with high precision.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the configuration of an embodiment of the present invention.

FIG. 2 is a plan view showing the relationship between the amount of deviation detected by a sensor and the amount of steering of a wheel.

FIG. 3 is a plan view showing a state in which the truck according to the present invention transitions from a straight path to a curved path;

FIG. 4 is a plan view showing the truck according to the present invention in a curved path;

FIG. 5 is a plan view of a conventional device.

FIG. 6 is a side view of FIG. 5;

[Explanation of symbols]

1. Light reflective tape 2 Vehicle body 3A sensor 3B sensor 4 Front wheel 5 Rear wheel

Claims (2)

[Claims] Claim 1: In an automatic transport vehicle that runs and steers on four wheels, sensors for detecting the travel route are installed at the front and rear of the vehicle body, and the front wheels are steered based on the detection signal from the front sensor, and the rear An automatic transport vehicle that is characterized by steering its rear wheels based on signals detected by sensors. [Claim 2] In an automatic transport vehicle that runs and steers on four wheels, sensors for detecting the travel route are installed at the front and rear of the vehicle body, and the front wheels are steered based on the detection signal from the front sensor, and the rear An automatic transport vehicle characterized in that the rear wheels are steered using a detection signal from a sensor, and the amount of steering by the rear wheels is smaller than the amount of steering by the front wheels.