FR2523330A1 - Optical guidance and control system for transportation carriage - contains decoder and microprocessor to read synchronisation and signalling pattern painted adjacent to track - Google Patents

Abstract

The self powered carriage (1) has two rear wheels (2) on an axle and is steered and driven by a front wheel (10) on a rotatable turret (3). The turret carries a UV emitter (6) whose beam covers the width of a track (5) painted on the ground and also triangular signalling patterns (8). A sensor unit (4) on the turret contains photodetectors positioned to the right and left of the track in an inner (DI,GI) and outer (DE,GE) configuration. The signalling patterns are sensed by photocells (7) located to provide synchronism (5) and to read (L) the pattern. The track following photodetectors provide inputs to electronic guidance circuits (GUI) for selection and application to a servo circuit to steer and drive the front wheel. A decoder (DEC) containing a microprocessor receives signalling sensor outputs to provide control signals for the carriage.

Description

 The present invention relates to an installation of self-propelled carriages with optical guidance, of the type comprising a colored guide track, signaling means affixed to the ground in the vicinity of said track and at least one self-propelled carriage supporting guidance means co-operating with the track colored to ensure its guidance along said track and control means cooperating with the signaling means to trigger the execution of instructions previously programmed.

 The use of self-propelled carriages with automatic guidance has recently taken on an important extension, and these carts are used in particular in large-area premises, for example in factories for the distribution and transport of parts or the like, between the various workstations. work, as well as in other storage rooms to ensure the transport and distribution of various items, as well as the connection between the different processing buddies.

 Various solutions are therefore already known for ensuring on the one hand the guiding of the carriages, and on the other hand triggering the execution of the various maneuvers or other operations at determined points of the journey made.

 These functions are ensured according to a first known solution, by means of a buried mental wire, which generates a field captured by means provided on the carriage, by means of which the various commands are ensured. However, this technique requires a relatively complex installation including in particular arcs containing the various necessary fittings.

 Another known solution consists in using a colored track for negating a contrast, this contrast etar.t detected by reading cells carried by the carriage and the orders being dor.nes to the latter either by interruptions provided in said track, or by means of metal plates fixed in the ground.

 These known solutions have various drawbacks. With regard to guidance by buried metal wire, the installation of the installation is only really possible without difficulty when it is provided during the construction of the premises for which it is intended. In addition, subsequent network transformations are difficult and costly.

 On the other hand, with the technique of guidance by colored track, it is possible, if need be, to trace said track on the floor of already existing premises. However, some systems still require work in the ground for fixing the metal plates ensuring the control of the carriage. In addition, in all the systems known up to now, the guide track remains visible, which makes it particularly inappropriate in certain premises for aesthetic reasons.

 The main object of the present invention is therefore to remedy these drawbacks by providing an installation of self-propelled carriages which can be easily installed in already existing premises, on most of the floors thereof, which does not use any complex or expensive equipment. , and whose network can be changed at will in a simple way.

 To this end, the purpose of the description is an installation of the aforementioned type which is essentially characterized in that the signaling means are constituted by a set of signs traced on the ground by means of a colored material similar to that constituting the guide track, and in that the control means carried by the carriage comprise a detection assembly capable of detecting said signs.

 Preferably, the guide track and the signaling means are traced on the ground by means of a material sensitive to ultraviolet rays, the trolley being equipped with a source of ultraviolet radiation capable of covering both said track. and said signaling means.

 Where appropriate, said material sensitive to ultraviolet rays may be formed by a paint which is nnraaicment invisible to white light.

 It is easily understood that thanks to the use of a paint sensitive to ultra-violet rays, the track and the signaling means according to the invention can be affixed to the floor of already existing premises and have the additional advantage, by compared to the tracks known by contrasting bands, of strength: used on floors of very varied natures without change of adjustment of the electronic circuits of the trolley. This allows in particular the use of paints invisible to the eye in certain rooms, on the carpet offices by exepie, and visible paintings in the adjacent premises containing a sul of a different nature, which was not possible until now with the> striped tracks for reasons of aesthetics.

 Generally, the carriage guide network includes a certain number of switches intended to ensure the transfer of the carriage from one track to another. In this case, the installation according to the invention is characterized in that the guide means carried by the carriage comprise four photo-sensitive cells arranged in line transversely to the track, the two in the middle serving for normal guidance of the carriage along the track, while the two on the right or the two on the left are respectively selected according to the indications provided by the signaling means in order to ensure the guidance of the carriage along a turn curve located on the right or to the left of the track, said turn curve consisting of two sections of parallel colored tracks whose spacing corresponds to that of the two cells on the right or on the left.

 In a particular embodiment of the invention, the four photo-sensitive cells are connected to an electronic guiding circuit comprising an adjustable gain amplifier to which the outputs of the four cells are applied and whose four outputs are connected to the four inputs d '' a subtracting amplifier whose four outputs are connected to a selector circuit which is itself connected to a microprocessor selecting the two cells on the right, the two in the middle or the two on the left according to a program of said microprocessor and according to the information provided by signaling means, the outputs of the selector circuit being each connected to a subtractor and to a summing device, the output of the subtractor being applied to a comparator controlling a guide presence relay, while the output of the summing device is applied to a circuit servo control the direction of the carriage.

 According to another characteristic of the invention, the detection assembly comprises two photo-sensitive cells arranged so as to scan said signs, provided with identical shape and surface, but oriented in two opposite directions relative to the guide track, so as to constitute binary coding elements for said cells.

 Preferably, said signs consist of equal isosceles triangles, the base of which is arranged parallel to the guide track.

 Furthermore, the two cells of the detection assembly are connected to an electronic decoding circuit comprising means sensitive to rising edge signals and means sensitive to falling edge signals, arranged so that the outputs of said cells indicate, for each triangle, the position relative to the track of the vertex opposite the base, so as to attribute to the sign thus detected the binary value UN or ZERO according to its position.

An embodiment of the invention is described below by way of example, with reference to the accompanying drawings in which
- Figure 1 is a schematic view of a self-propelled carriage according to the invention and a portion of the guide track for said carriage, with a switch and signaling means
- Figure 2 is a block diagram of the electronic circuit for guiding the carriage
- Figure 3 is a block diagram of the electronic decoding circuit of the signaling means; and
- Figure 4 is a schematic view on a larger scale showing the two basic elements doemoyens signaling according to the invention.

By first referring to FIG. 1, one can see a self-propelled carriage 1 able to move in the direction indicated by the arrow F along a straight guide track 5. This carriage is of conventional design and comprises a rear axle with two idle wheels 2 and a pivoting front turret 3 carrying a wheel 10 which is both driving and steering thanks to two motors not shown. At the front of the carriage is mounted a sensor 4 comprising four photo-sensitive cells, preferably of the photo-resistant type, arranged in line, transversely with respect to the guide track and at the same distance from each other For this purpose , the sensor 4 can moreover advantageously be fixed on the pivoting turret 3, so as to be always perpendicular to the track followed by the carriage. The four photoresist cells are designated respectively by DE, DI, GI, GE, and correspond respectively to the Right Outside, Right Inside positions,
Left Inside and Left Outside.

 The turret 3 furthermore comprises a device emitting ultra-violet rays 6 making it possible to cover the runway 5 over a sufficient width on either side thereof, as well as signaling means 8 affixed to the ground in the vicinity of said track and which will be described in more detail below.

 To detect these signaling means, the carriage 1 is equipped with a detection assembly 7 secured to the sensor 4, comprising a first photo-sensitive cell S called synchronism and a second photosensitive cell L called reading. The two cells are arranged on one side of the carriage, perpendicular to its longitudinal axis and at a distance from this axis which is equal to the distal separating the signaling means 8 from the axis of track 5.

 As can be seen very clearly in FIG. 1, the track 5 crosses at another right angle another straight track 9 at a point C. Upstream of this crossing and on the right side are drawn two curved auxiliary tracks 11 and 12 constituting a switch allowing the carriage 1 to pass directly from track 5 onto track 9. The radius of these two auxiliary tracks is of course greater than or equal to the turning radius of the carriage.

The auxiliary track it extends over approximately a quarter of a circle and its ends are parallel to the tracks 5 and 9. It is distant from these and the auxiliary track 12 of a width equal to the spacing of two adjacent cells of the sensor 4. The track 12 is concentric with the track 11 and its radius is defined by the distance between the center of the circular arc formed by the track 11 and the main tracks 5 and 9.

 The different tracks 5, 9, 11 and 12 contrast with the natural soil. According to the invention, these tracks as well as the signaling means 8 are drawn on the ground with a fluorescent varnish which is normally transparent or invisible to white light and which is bright red when it is lit by the ultra radiation source. - purple 6.

If necessary, the tracks and the signaling means could also be traced with a visible paint reacting to ultraviolet rays.

 The carriage 1 is completed by a first electronic guiding circuit GUI connected to the four cells of the sensor 4 and by a second electronic decoding circuit DEC connected to the two cells of the detection assembly 7.

The electronic guide circuit GUI is shown in a synoptic manner in FIG. 2 and firstly comprises an amplification circuit 13 with adjustable gain to which the outputs of the four photoresist cells DE, DI, GI and GE are applied. This amplification circuit 13 has four outputs corresponding to four amplification stages in parallel, these four outputs being connected to the four inputs of a subtracting amplifier circuit 14 which also comprises four outputs which are connected to four inputs of an electronic circuit 15 selection of two of the four cells
DE, DI, GI, GE of sensor 4, that is to say of the two middle cells, right or left.

 The selection circuit 15 comprises two outputs which are each connected to a subtractor circuit 16 and to a summing circuit 17. The output of the subtractor circuit 16 is connected to the input of a threshold comparator 18 which controls a presence relay of guidance 19. The output of the summing circuit 17 is connected to a servo circuit 20 which comprises four control outputs of the assembly 21 of the amplifier and the motor for steering the carriage 1.

 The electronic decoding circuit DEC is shown in a synoptic manner in FIG. 3 and firstly comprises a shaping circuit 22 to which the output of the photo-sensitive cell L called reading cell is connected and which transforms the signal emanating from this cell in a right-front pulse. The output of circuit 22 is connected to an input of an exclusive OR gate 23, the output of which is connected to an input of a door Er 24. The output of circuit 22 is also connected to the inputs (D) of four flip-flops 25, 26, 27 and 28.

 The synchronization cell S is connected to a circuit 29 for shaping identical to circuit 22, and the output of which is connected on the one hand to the input of a monostable circuit 30 the output of which is connected to the second input of gate AND 24.

 The output of circuit 29 is also connected to the input of an inverter 31, the output of which is connected to the input of a binary counter 32 having three outputs which are connected on the one hand to a decoder 33 , and on the other hand to the inputs of a data selector circuit 34.

 The decimal binary decoder circuit 33 has four outputs which are respectively connected to the inputs for triggering the recording of flip-flops 25, 26, 27, 28.

 Each flip-flop has two reverse outputs (Q) and (Ç. The outputs (Q) of each flip-flop are connected to the inputs of a card 37 comprising a microprocessor. The outputs (Q) of these flip-flops are connected to the four inputs of the selector circuit 34. The data selector circuit 34 has an output which is connected to the second input of the exclusive OR gate 23.

 The output of the AND gate 24 is connected via a switch 35 normally closed, to the input of an inverter 36 whose output is connected to each of the flip-flops 25, 26, 27 and 28. The input of the inverter 36 is also connected on the one hand to the decimal binary decoder circuit 33 and on the other hand to the binary counter 32.

 The output of the microprocessor card 37 is connected to a control input of the selection circuit 15 forming part of the guide circuit GUI shown in FIG. 2.

 We will now describe the operation of the carriage guidance system, with particular reference to this FIG. 2.

 The guidance is ensured by means of two photoresist cells of the sensor 4 whose spacing is equal to the width of the trace. Each cell is associated with a stage of the amplifier 13, the gain of which, adjustable by means of a potentiometer not shown, makes it possible to adjust the response curves of each of the cells to a standard curve.

 It will be noted that in the embodiment described here, the conductors driving the signals from the cells DE, DI, GI and GE to the circuit GUI of the carriage pass over the motors of the turret 3 which constitute emitters of parasites. It is therefore necessary to pass, for each cell, a wire connected to the ground journaled with the output wire of the amplifier 13, as illustrated in M in FIG. 2, so that they receive all the two the same parasites. In the assembly, these two wires are connected one to the input +, the other to the input - of an operational amplifier of the circuit 14, this amplifier being mounted as a subtractor. The parasites received are thus removed from the signal.

 The signal produced by a cell, and amplified by amplifier 13 is applied to the input - of amplifier 14 If we want a positive voltage, and to input + if we want a negative input. The right cell DI is assigned a negative voltage, and the left cell GI a positive voltage.

 First of all, it will be assumed that the selection circuit 15 selects the signals N coming from the cells DI and GI, which in fact corresponds to the normal mode of guiding the carriage along a track such as 5.

 The next stage is an amplifier mounted as a summator 17. If the cells DI and GI are each astride the edge of track 5, they emit the same signal in amplitude, but to which a different sign is assigned by circuit 14. The output of the adder 17 therefore remains at zero. When this output becomes positive, it means that the signal from the GI cell is greater in absolute value than the signal from the DI cell, and therefore that the sensor 4 is offset to the right with respect to track 5, and all the more more remote than the signal at the output of the adder 17 is large. This output signal from the adder 17 is called an error signal.

 The signals applied to the adder 17 are also applied to the subtractor 16, which outputs the sum of the absolute values of the signals from the DI and GI cells. The output of the subtractor 16 is connected to the comparator 18 which controls the relay 19 materializing the presence or absence of guidance.

 When the output of the subtractor 16 is less than a limit threshold, that is to say if the cells DI and GI are not above the track, the relay 19 falls, and the carriage stops.

 The error signal output from the summator 17 is applied to the direction control circuit 20. If there is "Guidance Presence", that is to say as long as the carriage is running, this error signal is transformed by circuit 20, on the one hand into a continuous signal "Right" or "Left", d on the other hand in an intermittent signal nRight "or" Left ", the duty cycle of which depends on the amplitude of the error signal. These two signals control the steering amplifier of set 21. The correction is ensured by a turret speed control in one direction or the other.

 In the system envisaged, four cells are necessary to allow the carriage 1 to follow a switch such as that which is shown in FIG. 1 by the auxiliary tracks 11 and 12.

The two cells in the middle GI and DI are used for the normal guidance mode N, as seen above. To follow a switch located on the right or on the left of the track, we switch, at the level of the selection circuit 15, either to the right cells DI and DE, or to the left cells GI and GE, in order to be find respectively in right guidance mode D or left guidance mode G. For simplicity, we will assume that the switch to be followed is located on the right, as in Figure 1. The cell
DI is then common to normal guidance N and to right guidance D. In normal guidance, the right cell DI is of negative sign, while the left cell GI is of positive sign, when switching to D guidance on the cells on the right DI and DE, the one that was on the right DI in N guidance becomes the left one in D guidance, while still being associated with the negative sign.

 It is therefore ultimately necessary that the DE cell is associated with a positive signal and that conversely the left cell GE is associated with a negative signal, so that two cells common to the same guidance mode are associated with an opposite sign . In this case, if the control is provided on a light strip 5, the error signal indicates a displacement relative to this strip 5 to the right when it is to the left, and vice versa.

This is why it is necessary to enslave the carriage 1 in "Negative" when taking a switch, the enslavement in T'Negative "meaning that the two cells DI and DE or CI and GE follow a dark band, between two bands bright such as 11 and 12.

 When the carriage 1 goes straight to the switch shown in Figure 1, and it approaches the point C of crossing tracks 5 and 9, it is in guidance N.

It controls its direction on the DI and GI cells. The two cells cut track 9 almost simultaneously. The disturbance caused by this excess of light is symmetrical on the two cells, and the error signal remains close to zero; even if the turret does not approach point C perfectly perpendicular, the amplitude and the duration of the error signal do not allow movement of the turret.

 We will now describe the operation of the control means of the carriage 1, with particular reference to Figures 3 and 4. These control means essentially comprise the decoding circuit DEC of the signaling means 8 detected by the two photo-sensitive cells S and L.

In the particular embodiment of the invention described here, the signaling means consist of groups of equal isosceles triangles, the base of which is arranged parallel to track 5. These triangles are oriented in two opposite directions relative to the track. , so as to form binary coding elements for said cells. Thus, and as illustrated in FIG. 4, the triangle such as Tg, the base of which is situated on the side of track 5 constitutes a binary element "O", while the triangle such as
T1 whose base is far from the track constitutes a binary element "1".

 The S and L cells, whose spacing is slightly less than the height of the isosceles triangles Tg or T1, send a high or low signal. At each transition between these two levels, there is a rising edge or a falling edge. If the detection assembly 7 approaches a triangle such as T1 representing a binary "1", the signal emitted by the reading cell L enters the shaping circuit 22 so as to transform the rising edge inclined into the rising edge law. The value taken by cell L arrives via the input (1) of the exclusive OR gate 23, and in all the inputs (D) of flip-flops 25, 26, 27 and 28. However, nothing happens as long as the input (CLK) of one of these flip-flops does not receive a falling edge. As long as the synchronism cell S has not arrived on the triangle, it sends a low level signal, which the inverter 31 transforms into a high level signal. The binary counter 32 has its three outputs at the low level, and the decimal binary decoder 33 has all its outputs at the low level, except the output (O) which is at the high level. The input of the monostable circuit 30 is also at the low level and there is no output signal.

 When cell S arrives on the triangle, the shaping circuit 29 straightens the front of the signal. A rising edge is applied to the input of the monostable circuit 30, the output of which remains at the low level, since this circuit is only sensitive to falling edges. A rising edge is also applied to the input of the inverter 31. There is therefore a falling edge at the output of this inverter 31 and at the input of the binary counter 32. The output (20) of the circuit O 32 and the input (2) of the circuit 33 pass to the high level while the other two outputs-inputs of these circuits remain at the low level.

 The output (O) of the decoder 33 then goes to the low level, while the output (1) goes to the high level, the other outputs remaining at the same low level.

We therefore send a falling edge on the input (CLK) of latch 25 and a rising edge on the input (CLK) of latch 26. This input is sensitive to falling edges, and therefore latch 25 records the value taken then by the input (D), that is to say the value that the reading cell L takes.

 The data selector 34, controlled by the inputs (A), (B) and 0 1 2 (C) connected to the outputs (2), (2) and (22) of the binary counter 32, takes out the level recorded in flip-flop 25, value which is therefore found at the input (2) of the exclusive OR gate 23. The other input of this gate 23 is connected to the shaping circuit 22 of the cell L, and displays the level taken by this cell. The output of door 23 is at the high level if its two inputs do not match, and at the low level if they match. This value is found at the input (2) of the AND gate 24.

 When cell S leaves the triangle, it provides a low level signal, and it applies, via the shaping circuit 29, a falling edge on the input of the monostable circuit 30, and a rising edge, by through the inverter 31, on the binary counter 32.

The latter does not react, while the output of circuit 30 provides a high level signal for a time determined by the value of circuit RC. During this time slot, the AND gate 24 therefore has its input (1) at the high level. If we have, on the entry (2) of this same door, an "O", that is to say if at the time of the slot, the value taken by cell L and that recorded by the flip-flop 25 are consistent, the output of the AND gate 24 then always displays "O" and nothing happens as long as the switch 35 is at rest, that is to say is closed. If, on the contrary, the output of the exclusive OR gate 23 is at "1" in this slot, there is a high level on the output of gate 24, which makes a high level pass on the inputs (CLR) of circuits 32 and 33, and passes the inputs (CLR) of flip-flops 25, 26, 27 and 28 at the low level via the inverter 36, which causes these six circuits to be reset. The switch 35 allows manual reset if necessary.

 If there is no reset, when cell S approaches the next triangle, the outputs of binary counter 32 indicate "2" in binary, and it is flip-flop 26 which records the value then taken by cell L.

When the four bits have passed, the four flip-flops 25, 26, 27 and 28 have recorded the successive values of the four bits. These values are applied to the microprocessor card 37 and represent the code materialized on the ground by the triangles Tg and T1 of the signaling means 8.

A system has been described here making it possible to obtain sixteen coding possibilities, which corresponds to four successive isosceles triangles. It goes without saying, however, that one could very easily multiply these coding possibilities by simply adding flip-flops, that is to say by increasing the number of bits.
The microprocessor card 37, comprising in particular the memory circuits o- n- ^ cessdJres po..r interpreting the codes and ordering in source the sele-tionncur l is entirely classical in design and will therefore not be described e et al
Now it will easily be understood that the signs constituted by isosceles triangles such as T0 and T1 are the elements of a binary coding which, in combination with the cells S and L and with the decoding circuit DEC, form a system in which the position of each sign relative to track 5 is detected, thus making it possible to assign its value "1" or "O", regardless of the angle at which the cells approach said triangles and the constant speed or not of the scanning.

 The binary codes thus composed at will constitute a geographic location of the carriage, the reading of which then allows the program previously recorded in the microprocessor card 37 to give the various control circuits the necessary orders, in particular to address the switches or cause the stop of the carriage at determined points on the network.

Claims (8)

 1. Installation of self-propelled trolleys with optical guidance, of the type comprising a colored guide track (5), signaling means (8) affixed to the ground in the vicinity of said track and at least one self-propelled trolley (1) comprising means guide (4, GUI) cooperating with the colored track (5) to ensure its guidance along said track and control means (7, AEC) cooperating with the signaling means (8) to trigger the execution of Instructions previously programmed, characterized in that the signaling means (8) consist of a set of signs (T ,, T1) traced on the ground by means of a colored material similar to that constituting the guide track (5) , and in that the control means carried by the carriage (1) comprise a detection assembly (7) capable of detecting said signs (Tg, T1)  2. Installation according to claim 1, characterized in that the guide track (5) and the signaling means (8) are traced on the ground by means of a material sensitive to ultraviolet rays, the carriage (1) being equipped with a source of ultraviolet radiation (6) capable of covering both said track and said signaling means.  3. Installation according to claim 2, characterized in that said material sensitive to ultraviolet rays consists of a paint which is normally invisible to white light.  4. Installation according to any one of claims 1 to 3, in which the guide track comprises a certain number of switches, characterized in that the guide means (4) carried by the carriage (1) comprise four photo cells -sensitive (DE, DI, GI, GE) arranged in a line transverse to the track (5), the two in the middle (DI, GI) used for normal guidance of the carriage along the track, while the two of right (DE, DI) or the two on the left (GE, GI) are respectively selected according to the indications provided by the signaling means (8) in order to guide the carriage (1) along a curve d 'switch located to the right or left of the track (5), said turn curve consisting of two sections of parallel colored tracks (11, 12) whose spacing corresponds to that of the two cells on the right or left.  5. Installation according to claim 4, characterized in that the four photo-sensitive cells (DE, DI, GI, GE> are connected to an electronic guide circuit & (GUI) comprising an adjustable gain amplifier (13) to which are applied the outputs of the four cells and whose four outputs are connected to the four inputs of a subtracting amplifier (14) whose four outputs are connected to a selector circuit (15) which is itself connected to a microprocessor (37) selecting the two cells on the right (DE, DI), the two in the middle (DI, GI) or the two on the left (GE, GI) according to a program of said microprocessor and according to the information provided by the signaling means (8), the outputs of the selector circuit (15) being each connected to a subtractor (16) and to an adder (17), the output of the subtractor (16) being applied to a comparator (18) controlling a relay (19) for guiding presence, while the scmmator output (17) is applied to a servo circuit (20) controlling the direction (21) of the carriage.  6. Installation according to any one of claims 1 to 5, characterized in that the detection assembly (7) comprises two photo-sensitive cells (S, L) arranged so as to scan said signs (Tn, T1), provided with identical shape and surface, but oriented in two opposite directions with respect to the guide track (5), so as to constitute binary coding elements for said cells.  7. Installation according to claim 6, characterized in that said signs (Tg, T1) are constituted by equal isosceles triangles whose base is arranged parallel to the guide track (5).  8. Installation according to claim 7, characterized in that the two cells (S, L) of the detection assembly (7) are connected to an electronic decoding circuit (DEC) comprising means (31, 32, 33) responsive to rising edge signals and means (30) responsive to falling edge signals, arranged so that the outputs of said cells indicate, for each triangle (Tg, T1), the position relative to the track (5 ) from the vertex opposite the base, so as to assign to the sign thus detected the binary value UN or ZERO according to its position.