FR2584197A1 - System for location and automatic guidance by optically targeting coded transmitting beacons - Google Patents

Abstract

The invention relates to an electro-optical system which enables a vehicle to track preprogrammed trajectories automatically at a preprogrammed speed in a given region. The system consists of electronic equipment on the vehicle and of several beacons (at least 3) placed around it so as to define a region of activity. Each beacon comprises light-emitting diodes in the infra-red spectrum which transmit a coded signal specific to the beacon. The vehicle comprises an analysing head made from a parabolic reflector rotating at a constant speed and thus sweeps over the whole field around it so as to target the various beacons successively. The light signal from the beacons is focused by the reflector onto a photosensitive detector and then converted into an electrical signal; it is processed in decoders which, by counting on a clock, give binary values proportional to the angles at which the beacons are sighted. From the known orientation of the vehicle and from a comparison of the angles with those contained in a memory, the system produces, on the one hand, a guidance instruction which is edited and applied to the steering servocontrol and, on the other hand, a speed instruction.

Description

DESCRIPTION
The present invention relates to a system for automatically locating and guiding mobile vehicles.

It is based on electronic and optical techniques and mainly uses existing components available on the market.

Existing systems are rather based either on radar techniques (distance measurement) or on systems for detecting buried wires or bands glued to the ground, or on systems with inertial units, or even on distance measurements by measurement of travel time of radio pulses synchronized at the start by very precise clocks.

The principle of the present invention is based on measurements of angles by successive sightings, from the mobile, of fixed beacons.

The system consists of fixed beacons (at least 3) and equipment mounted on the vehicle to be guided.

The principle of localization is highlighted in Figure 1/6.

Or a vehicle (4) oriented according to # and 3 fixed beacons (1), (2) and (3) permanently emitting a modulated light signal. From successive views of these tags, the vehicle determines
- its orientation: angle (5) made by its axis by
report to the direction of one of the tags,
- the 2 angles b (6) and c (7); the vehicle is therefore
on the circle C b (8); place of the points from which we see
tags 1 and 2 under angle b. (6).

on the circle C c (9), place of the points from which we see
the tags 2 and 3 scus I angle c (7) figure 1/6) a at the intersection of the 2 circles C b and C c single point The angles are stretched out by counting clock pulses between the shots made by a. analysis head which rotates at a given constant speed.

The development of the direction guidance order is done from a comparison of angles to those of a memory.

The value of the angle b (6) (time between aiming beacon 1 and aiming beacon 2) gives position information in a direction perpendicular to a line connecting beacons 1 and 2. This angle is called angle of advance.

If the vehicle is on the correct trajectory, at each angle b (6) corresponds. on the one hand an ideal angle c (7) called "set point" c 'and on the other hand an orientation a (5) set point a'.

Programming a trajectory for the vehicle consists in calculating for each angle b a setpoint angle, c 'and a setpoint angle a', then saving a table of all the corresponding values c 'and a'.

The guidance order is of the form
G = m (c '- c) + n (a' - a) + prm, n and p being constants and r a term proportional to the orientation of the wheels relative to the axis of the vehicle
Each beacon is portable, autonomous. As shown in FIG. 2/6, it comprises a battery (10) with possibly its charger, an electronic device for generating the modulation signal, a series of light-emitting diodes (I1), a polarizing filter (12) and a radio receiver (13 ) optional. The electronics consists of a clock generator (14) at around 100 KHz, a code generator (15) (adjustable) from 4 to 8 bits and amplifier circuits (16)
The radio receiver (13) of very simple design, tuned to a single frequency is intended to trigger the emission of the code by the light-emitting diodes for 10 seconds after reception of a radio pulse on the right frequency, this for the purpose of 'save the battery (10) when the vehicle (s) is at rest.

The diodes are amplitude modulated with a code which sc repeats at around 10 KHz.

On the vehicle to be guided is equipment comprising
an analysis head with its cover (transparent to
light signals).

. a motor with its control electronics,
processing and processing electronics
orders with his memory,
servos acting on the direction and on
vehicle speed
The analysis head is composed of an optical device which rotates at constant speed using a stepping motor, and a photosensitive detector followed by a preamplifier and a shaping circuit.

The sensitive face of the detector is arranged horizontally.

The optical device which rotates around a vertical axis passing through the center of the detector can be produced according to one of the solutions below 1st Solution (see figure 3/6)
Parabolic reflector (17) reflecting the rays
parallels from infinity along the line of sight towards
a 45 ° mirror (18) placed below the detector (19)
so that the focus of the parabola is the image (20)
of the detector in relation to the mirror. The motor (21) in
drags the disc (22) on which the reflector is fixed
(17) and the mirror (18) at 45 ".

2nd Solution (see figure 4/6)
In this solution, it is the parabolic reflector (17)
which is tilted by about 45, which removes
the mirror at 45.

The light rays (23) coming from infinity are concentrated
directly on the photo-sensitive detector.

3rd Solution
Figure 5j6 shows an analysis head comprising on the
rotating disc (2! an optical objective made of a suc
transfer of lenses (24) followed by a 45Q mirror (18).

For the 3 solutions the disc which includes the optics rotates at around 200 revolutions / minute so as to scan 1 "in 1 ms.

The signal received by the analysis head is processed by electronic circuits which perform the following functions as shown in Figure 6/6.

- Clock generation
. 100 RHz clock (25) for decoding signals
received,
. Clock (26) for counting angles at 800 Hz for
8-bit angle coding (clock at 3.5 z
for coding angles on 12 bits),
- counter a (28) started by the decoder of tag 1
and stopped by an electrical contact which trips
when the line of sight of the head is parallel to the axis
of the vehicle
counter b (29) started by the decoder of tag 1
and stopped by the beacon 2 decoder.

counter c (30) started by the decoder of tag 2
and stopped by the decoder of tag 3.

memory a '(31) addressed by the value of counter b and
containing the angles a '.

memory c '(32) addressed by the value of counter b and
containing the angles c '.

- Adders (33) to obtain
(a '- a) + (c' - c)
- Digital to analog converter (34)
- Control (35) of the steering motor (36) with
potentiometric feedback (37).

speed memory v (38) addressed by the value of
counter b
- Speed control (39)
Three different systems can be used to perform these functions
- Cabal operators, associated with memories and
logic circuits,
- a microprocessor with scs peripheral circuits.

- A microcomputer with an input card / digital output
and analog t memory (eg floppy).

Claims (10)

1) Opto-electronic system intended to locate and guide  a mobile automatically according to a prepro trajectory  the guiding orders being developed from  comparison with stored setpoint values of  angular values measured by successive aiming, using  a rotating directive detector optical head, beacons  transmitting a coded light signal, beacons, to the number  minimum of 3, being arranged so as to delimit the area  moving the mobile. 2) System according to claim 1 characterized in that the  detector optical head rotates at constant speed so that  the time that elapses between the sightings of 2 tags is  proportional to the angle formed by the directions of the 2 ba  read from mobile. 3) System according to claims 1 and 2 characterized in that  that each beacon emits a series of light pulses  (visible or infrared) forming a specific repetitive code  beacon fique. 4) System according to claims 1 and 2 characterized in that  that an electrical contact device gives at each turn  from the detector head an electrical impulse at the moment  or the line of sight of the head is parallel to the axis of the mo  bile which allows to determine the angle of orientation  by measuring the time between this impulse and the aim of a  reference tag. 5) System according to claims 1, 2 and 4, characterized in  what it measures 2 angles between tags, one of these angles  (called feed angle) having the metering rule  memories containing the angle setpoint values  orientation, the other angle between tags (called angle  lateral guidance) and the target speed of the mobile.  6) System according to claims 1, 2, 4 and 5 characterized  in that the direction guidance order is a signal  electric part of which is proportional to the diff  reference between the orientation angle measured and the angle  memorized setpoint orientation and another part  proportional to the difference between the guide angle  measured side and the stored setpoint.  7) System according to claims 1,2, 4, 5 and 6 characterized  by the faculty "learning a trajectory" by the  storage in random access memories, addressed by the angle  in advance, the angle of orientation, the guide angle  lateral and speed during a first course of  this trajectory is "by hand".  8) System according to claims 1. 2 and 3 characterized by  the use of rectilinear polarizing filters arranged with a  go. in front of the emitting part of each tag and other  hand, in front of the detector so that the light signals  emitted by the beacons and directly received by the head of ana  lysis of the mobile are not attenuated by the presence of  filters while the beacon light signals that would  received after thinking about obstacles be mitigated because  of the polarization change due to reflection.  9) System according to claims 1. 2, and 3 characterized in that  that each beacon is autonomous and equipped with a radio receiver  which controls the supply, from the battery, of the diodes  electroluminescent so that they do not emit their  signal that for a predetermined time (e.g. 10  seconds) after receiving a radio signal at the correct frequency. 10) System according to claims 1. 2, 3 and 9 characterized by  the presence and use on the mobile to be guided of a transmitter  radio tor intended to transmit only the beacons  light he needs to guide himself according to his activity  (on or off) and the memory it has of its position.