EP0352565A2 - Position-measuring device for crane conveying and telpher lines - Google Patents

Abstract

The device contains a code carrier (11) which carries multi-valued code marks (17) along its longitudinal extent. A code reading device (12) interacts with the code carrier (11) and sits on the cat or the undercarriage (4) of the crane or the monorail. To ensure that there are no incorrect reading results when the chassis (4) and the code reading device (12) are tilted or skewed compared to the code carrier (11) and the requirements for the positional accuracy of the code carrier (11) are as small as possible, the code marks (17) are on the Code carrier (11) arranged in a single track one behind the other and formed in such a way that the code marks (17) forming a code word, which are each directly adjacent to one another, are unique along the entire code carrier (11).

Description

The invention relates to a device for position measurement in crane and electric monorails, according to the features of the preamble of claim 1.

From DE-OS 34 45 830 a positioning device for a conveyor system is known, in which two lasers are arranged on a gantry crane, which scan reference elements attached to the floor. The reference elements consist of two marking areas arranged at a certain distance from one another and in a certain direction. One of the marking areas has an elongated strip-like shape and is scanned by a laser beam, while the other marking area has a very small area and is detected by the second laser beam. Both marking areas are arranged in such a way that only when a desired position is reached both can be detected by the respective laser beams.

With this arrangement, only certain positions defined by the marking areas in the working area of the conveyor system can be controlled. Otherwise, the floor under the crane would be completely covered by the marking areas and this space would be lost for placing loads. In addition, with the known positioning device it is only possible to move to end positions.

Coded position sensors are known from "Controls and Regulations in Mechanical Engineering" 3rd edition, Verlag Europa-Lehrmittel, Wuppertal, with which distances can be measured absolutely. A code reading device is moved along a code carrier and the code marks located on the code carrier are scanned by reading heads. Several code marks form a code word on the code carrier, which is a direct measure of the distance traveled by the code reading device from a fixed reference point.

In this known device, the code marks of a code word are divided into several tracks which lie alongside one another along the code carrier. For this reason, care must be taken to ensure that the tracks lie next to each other with the exact clock and, moreover, the read heads, which are lined up next to one another transversely to the direction of movement, must have no offset with respect to the clock tracks. If such an offset occurs, for example due to skewing, a so-called skew error occurs and mixed code marks are read from adjacent code words, which leads to corresponding errors. Such a measuring system is therefore preferably limited to applications in which the spatial dimensions are small and one careful guidance of the reading heads towards the code carrier can be achieved. Large tolerances must be used in crane construction, which makes the use of such a measuring device impossible.

The object of the invention is therefore to provide a device for position measurement with which a distance can be determined with a high degree of measurement accuracy and which is insensitive to tilting or tilting of the code reading device with respect to the code carrier.

This object is achieved according to the invention by the device with the features of claim 1.

Since in the new device there is only a single code track on the code carrier, the arrangement is largely insensitive to tilting or slanting between the reading device and the code carrier, because regardless of the slanting position, the same code word is always read out by the reading device, provided that the sloping position is not so extreme that the reading device reads next to the code carrier. Also, a height offset of the code carrier is practically irrelevant, which considerably simplifies the attachment of the code carrier to the running rail, since there are no such high demands on the positional accuracy.

As a result of the use of code words which occur only once along the code carrier, it is immediately possible to determine where the relevant chassis or the corresponding cat is located, even without a movement of the trolley or the chassis, even after a system failure. This is particularly important when used in high-bay warehouses because there an error about the true location of the undercarriage can cause considerable damage. Also, in a high-bay warehouse, it is practically not possible to first carry out travel movements to determine the location of the undercarriage because this can already cause damage.

Code mark sequences that have the above-mentioned property of being unique along the code carrier are easiest to generate according to the theory of primitive polynomials with the aid of feedback shift registers. In this way, the uniqueness of each code word is guaranteed, as the number theory shows.

In order to be able to determine the position as quickly as possible and without any movements, the code reading device contains a reading head for each position of the code word, i.e. in the case of a ten-digit code word, ten read heads are arranged next to one another, their relative distance being equal to the length of a code mark on the code carrier.

In order to be able to determine without additional mechanical means whether the code word supplied by the read heads is a true code word or is falsified by the fact that one or more of the read heads are already in the next code mark, while other read heads are still reading previous code marks, are three sets of Read heads are provided, which are nested. Two immediately adjacent sets of read heads are used to generate the code word, while the third set provides the decision-making aid as to which of the two sets of read heads may have an error and which reads without errors.

Since the code words read from the code carrier are in no way lexicographically arranged when the cat is continuously driving, if the code words are interpreted as a binary number, it is expedient to convert the code word into a binary number which corresponds to the number of the code word within the generating code sequence table. After the conversion, the determination of the cat position is then the product of the code mark length with the number of the code word read, based on the start of the table, which corresponds to the start of the code carrier.

In addition to the above-mentioned purely electronic monitoring of the reading heads for possible reading errors, electromechanical solutions are also conceivable, in which one of the rollers delivers a clock signal that determines when the information supplied by the reading heads is correct information and when the reading heads are unfavorably above code mark boundaries .

• Fig. 1 eine Krananordnung mit einem Positionsmeßsystem gemäß der Erfindung in einer perspektivischen Darstellung,
• Fig. 2 einen Ausschnitt aus der Laufschiene des Krans nach Fig. 1 unter Veranschaulichung des Code­trägers und der damit zusammenwirkenden Code­lesevorrichtung,
• Fig. 3 ein fünfstelliges rückgekoppeltes Schieberegister zur Erzeugung einer Pseudozufallszahlenfolge, bei der innerhalb der Folge jede Zahl nur einmal auftritt,
• Fig. 4 die mit dem Schieberegister nach Fig. 3 nach­einander zu erzeugenden Codeworte oder -zahlen mit der zugehörigen Nummer,
• Fig. 5 eine Tabelle möglicher Primitivpolynome für längere oder kürzere Schieberegister zum Erzeugen von Pseudozufallszahlen,
• Fig. 6 das Blockschaltbild einer Schaltungsanord­nung zur Umwandlung des gelesenen Codewortes in die Nummer des Codewortes mit Hilfe eines Schieberegisters nach Fig. 3 sowie eines Bi­närzählers,
• Fig. 7 das Blockschaltbild einer Konvertierungsschal­tung zur Umwandlung eines gelesenen Codewor­tes in dessen Nummer mit Hilfe eines ROM-­Speichers,
• Fig. 8 das Blockschaltbild einer beispielhaften Aus­wahlschaltung zur Ermittlung desjenigen Satzes von Leseköpfen, der eine eindeutige Lage ge­genüber dem Codeträger aufweist und ein wahres Codewort liest,
• Fig. 9 ein dreistellig rückgekoppeltes Schieberegister zur Erzeugung einer Pseudozufallszahlenfolge, mit einem dreiwertigen Code, wobei innerhalb der Folge jede Zahl nur einmal auftritt,
• Fig.10 die mit dem Schieberegister nach Fig. 9 nach­einander zu erzeugenden Codeworte oder -zahlen mit zugehörigen Nummern,
• Fig.11 einen Codemarkenträger, bei dem ein dreiwerti­ger Code durch Grauwerte verschlüsselt ist,
• Fig.12 in Blockschaltbild für eine Codelesevorrich­tung zum Lesen des Codeträgers nach Fig. 11,
• Fig.13 einen Codeträger mit farbiger Verschlüsselung der Codemarkenwerte und
• Fig.14 ein Blockschaltbild für eine Codelesevorrich­tung mit farbiger Verschlüsselung der Werte der Codemarken.

In the drawing, an embodiment of the object of the invention is shown. Show it:

• 1 is a perspective view of a crane arrangement with a position measuring system according to the invention,
• 2 shows a section of the running rail of the crane according to FIG. 1, illustrating the code carrier and the code reading device interacting therewith,
• 3 shows a five-digit feedback shift register for generating a pseudo-random number sequence in which each number occurs only once within the sequence,
• 4 the code words or numbers to be generated in succession with the shift register according to FIG. 3 with the associated number,
• 5 shows a table of possible primitive polynomials for longer or shorter shift registers for generating pseudo random numbers,
• 6 shows the block diagram of a circuit arrangement for converting the read code word into the number of the code word with the aid of a shift register according to FIG. 3 and a binary counter,
• 7 shows the block diagram of a conversion circuit for converting a read code word into its number with the aid of a ROM memory,
• 8 shows the block diagram of an exemplary selection circuit for determining that set of reading heads which has an unambiguous position relative to the code carrier and reads a true code word,
• 9 shows a three-digit feedback shift register for generating a pseudo-random number sequence, with a three-value code, each number occurring only once within the sequence,
• 10 the code words or numbers to be generated in succession with the shift register according to FIG. 9, with associated numbers,
• 11 shows a code mark carrier in which a three-value code is encrypted by gray values,
• 12 is a block diagram for a code reading device for reading the code carrier according to FIG. 11,
• 13 shows a code carrier with color coding of the code mark values and
• 14 shows a block diagram for a code reading device with color coding of the values of the code marks.

In Fig. 1, a crane designated 1 with a boom 2 is illustrated, which has a horizontally extending guide rail 2 in the form of an I-profile, which projects at one end from a wall 3, not shown. A conveyor element designed as a trolley 4 can run along the running rail 2 and can be moved longitudinally in the longitudinal direction of the running rail 2 by means of rollers 5, at least one of which can be driven by a drive device which cannot be identified. The trolley 4 is provided for lifting and lowering loads 6 with a conventional lifting device 7, on the traction means 8 of which the load 6 is to be attached.

A code carrier 11 is attached to the web 9 of the I-shaped running rail 2 and extends over the entire length of the shortened running rail 2. A code reading device 12 cooperates with this code carrier 11, which is located on the trolley 4 and thus runs past the code carrier 11 when the trolley 4 moves along the running rail 2. The code reading device 12 is connected via a line 13 to evaluation electronics 14, which forward the determined data to a central control circuit 15 via sliding contacts and busbars which are attached on the opposite side of the web 9. The control circuit 15 shuts down or starts the drive device of the trolley 4 according to the position reached. The busbars for the drive device are also located on the back of the web 9 and are therefore again not recognizable.

In Fig. 2, a piece of the web 9 is shown in an enlarged and highly schematic section. According to this, the code carrier 11 consists of an elongated strip 10 which is fastened on the web 9 and passes over the entire length of the running rail 2. In the case of greater lengths of the running rail 2, the code carrier 11 is formed from a plurality of strips 10 which abut one another without a gap. On this bar 10, rectangular fields 16 of equal size can be seen, which symbolize the individual code marks 17. These fields 16, like the field 16 ', are either opaque or, like the field 16 das, transparent, with two different values zero and one can be represented. For example, the value zero is assigned to the opaque field 16 'and the value one to the transparent field 16˝.

The code carrier 11 is scanned or read by means of the code reading device 12, which carries lamps 18 opposite the top of the code carrier 11 and reading stations 19 opposite the bottom. Both the reading stations 19 and the lamps 18 are mounted on a common frame 20 which is connected to the trolley 4 and is moved along parallel to the code carrier 11 when the trolley 4 is traveling. Each of the reading stations 19 - in the exemplary embodiment shown there are five - is connected via connection lines 21 to the evaluation circuit 14, which reports its data to the central controller 15 via conductor lines 22.

The code carrier 11 shown is a so-called transmissive code carrier which, depending on the value of the code mark, transmits more or less light from the illumination device to the reading station. Instead of the transmissive code carrier 11, a reflective code carrier can also be used, in which case the lighting device and the reading stations are located on the same side of the code carrier 11 and the reading station evaluates the light reflected by the reflective code carrier in order, depending on the reflection conditions, at the corresponding mark to generate digital zero or a digital one.

It is essential in the new arrangement that the code marks 16 are arranged in a track or line one behind the other along the travel rail 2 without gaps, so that canting and inclination of the reading stations 19 arranged in a row next to one another in the longitudinal direction of the code carrier 11 cannot lead to reading errors.

A five-digit binary number can be read with five reading stations 19; their largest value is 31, so that a total of 32 different numerical values can be distinguished. Generally speaking, N = x ^m different numbers can be represented, where x is the value of a number and m is the number of numbers. The largest number that can be represented is N = x ^m -1. Thus, the greater the number of reading stations 18, the more different numbers and thus positions of the trolley 4 can be distinguished from one another or the longer the running rail 2 can be if the resolving power of the positioning accuracy of the trolley 4 does not ver should be deteriorated. The resolving power of the positioning accuracy results essentially from the extension of a code mark 17 in the longitudinal direction of the running rail 2, since the reading station 19 can be positioned as desired within a code mark without the number read changing.

It is understood that for this reason a much higher number of reading stations 19 is used in practice in order to be able to achieve a positioning accuracy of, for example, 1 cm with the lengths of running rails 2 which occur in practice. The number of reading stations 19 shown is therefore only an example and is therefore so low that the understanding is not unnecessarily complicated.

In order to be able to clearly read the position of the trolley 4 along the running rail 2 with the code marks 17 arranged one behind the other, of which five immediately adjacent ones are read simultaneously, any group of five adjacent code marks 17 must be unique along the running rail 2 , ie this group may only appear once along track 2. In the following, the term code word is used for a group of five adjacent code marks.

Sequences of numbers that meet the above condition that each number occurs only once in the sequence are so-called pseudo-random numbers. According to the theory of "primitive polynomials", they can be generated with the aid of a linear feedback shift register, the number of digits of which corresponds to the number of digits in the binary code word.

3 shows the shift register which is generated for a five-digit code. It contains a total of five D flip-flops 23a ... 23e, the clock inputs 24 of which are connected in parallel, so that they change their state at the same time. Which state they take after the clock pulse depends on the state of the Q output of the previous flip-flop 23a ... 23e, because the D input of flip-flop 23a is connected to the Q output of flip-flop 23b, the D input of flip-flop 23b is connected to the Q output of flip-flop 23c etc., up to flip-flop 23e . At its D input there is a modulo-2 adder 25 with three inputs 26, one of which is connected to the Q output of flip-flop 23d and the other to the Q output of flip-flop 23a, while in the third one is permanently connected binary one is fed. A modulo-2 adder 25 has the property that its output is a logic one only if and when an odd number of its input connections are in the logic one state.

If all D flip-flops 23a ... 23e are now reset before the input of the first clock pulse, ie there is an L signal at their Q output, then two of the inputs 26 of the modulo-2 adder 25 are also L while the third input receives an H signal, so that the output of the modulo-2 adder 25 also has an H level, which is fed to the D input of the flip-flop 23e. After the disappearance of the clock pulse, the flip-flop 23e is therefore in state one, while the remaining flip-flops are still in state zero. After the second clock pulse, the two flip-flops 23e and 23d are in the on state, while the remaining flip-flops are still in the zero state. Now that the modulo-2 Adder 25 receives an H signal at two of its inputs 26, its output changes to L, ie with the next clock pulse the shift register pulls in a zero and the flip-flop 23e is in the zero state. The two flip-flops 23c and 23d are in the state one, while finally the flip-flops 23a and 23b in turn have the state zero. The further states that the flip-flops 23a ... 23e can assume in the further successive clock cycles are shown in the table from FIG. 4. Obviously, each five-digit binary number occurs only once within a period of a total of 31 numbers. If you now, starting from the binary number zero with five consecutive binary zeros, extend the last result to the left by the binary digit that occurs in succession at the Q output of the flip-flop 23e, you finally get a sequence of 35 binary digits, whereby each form five consecutive binary digits of one of the code words or binary numbers from the table in FIG. 4. This makes it possible to unambiguously recognize, based on the code word emerging from the binary string generated in this way, how many code words from the table according to FIG. 4 are involved, or how many steps are necessary to get from code word "O" to the respective code word .

If the sequence of binary ones and zeros generated according to the above description is applied to the code carrier 11 as code marks 16 in the form of a light / dark marking, as shown in FIG. 2 from left to right, that is to say as a mirror image of the table according to FIG. 4 has happened, can be clearly determined on the basis of the code word read, where the trolley 4 is located along the running rail 2. The code word read can be used determine how many code words from the table according to FIG. 4 it is, ie how many steps or code word changes were necessary to arrive at the relevant code word. The stride length corresponds to the length of a code mark; thus the distance of the trolley 4 from the beginning of the code carrier 11 is equal to the length of a code mark 17 multiplied by the position of the code word in the table.

FIG. 5 contains a table which indicates the length of the shift register according to FIG. 3 and how the individual outputs of the shift register must be linked in the modulo-2 operation in order to determine the binary digit which is fed into the least significant D flip-flop will. Depending on the selected slide register length, which corresponds to the number of reading stations 19 on the trolley 4, a corresponding number of code words and thus increments can be distinguished, which the trolley 4 can measure on the running rail 2 from the beginning of the running rail 2 without having to measure the position the trolley 4 along the running rail 2 ambiguities occur.

As can be seen from the above, the length of each individual code mark 17, which are of equal length to one another, defines the step length after which the reading stations 19 of the reading device 12 read a new code word when they are exceeded. Based on its position within the table according to FIG. 4, the read code word defines how many steps are necessary to get from the code word zero to the read code word.

Since the number of steps is easier to process than the read pseudo-random code word for the further control of the trolley 4, the Evaluation circuit 14 converts the read code word into a binary number, which indicates the number of steps passed since the beginning of code carrier 11. A suitable conversion circuit 28 is shown in FIG. 6. It contains a binary comparator 29 with two sets of inputs 31 and 32, which have an input connection for each digit of a multi-digit binary word, in order to be able to check two multi-digit binary words for identity in bit parallel. Depending on the result of this comparison, the level at an output 33 is H or L. In detail, the state is H if the two binary words are different and L if the two binary words are identical.

With the aid of the comparator 29, the binary word supplied by the reading stations 19, which is fed into the input 31 via the lines 21, is compared with a binary word that a shift register 34 generates at its binary output 35. This shift register 34 has the structure explained in detail in FIG. 3 and also its mode of operation. For each binary position in the binary word, the output 35 has a connection which is correspondingly connected to an associated connection of the input 32 on the comparator.

The signal of the output 33 controls on the one hand a start / stop oscillator 36 at its inhibit input 37 and on the other hand a non-retriggerable monoflop 38 at its trigger input 39. The two inputs 37 and 39 are connected to the output 33 via a corresponding line.

The start-stop oscillator 36 contains a clock output 41, which is connected to a clock input 42 of the shift register 34 and a clock input 43 of a binary counter 44 via corresponding lines. For resetting, both the shift register 34 and the binary counter 44 each have a reset input 45 or 46, both of which are connected to an output 47 of the monoflop 39 via lines.

The binary counter 44 has a bit-parallel output 48, i.e. a separate output connection for each binary position and is connected to a data input 49 of an output register 51 via parallel data lines. Its bit-parallel output 52 is connected to the conductor lines 22. The output register 51 is to be controlled via a load input 53, specifically the binary word at the input 49 is taken over to the output when an L level is present at the input 53.

The circuit described so far works as follows: as long as the binary word, which is supplied by the reading stations 19 to the input 31, matches the binary word which the shift register 34 feeds into the input 32, the output 33 has an L level. This L level blocks the start / stop oscillator 36 at the inhibit input 37 and also ensures that the output register 51 outputs the same binary word that is fed in at the input 49. If the trolley 4 now travels a distance, namely more than one code mark 17 on the code carrier 11, the code word read by the reading stations 19 changes, which consequently differs from the code generated in the shift register 34 word differs. The output 33 of the comparator 29 therefore changes from L to H, whereby on the one hand the start-stop oscillator 36 is released at its inhibit input 37 and on the other hand the monoflop 38 is triggered by the positive edge going to H. The monoflop 38 then delivers a short reset pulse to both the counter 44 and the shift register 34, both of which are then brought to the 00000 state. At the same time, the output 52 in the output register 51 is separated from the input 49, so that during the subsequent counting process the old binary number at output 52 is retained.

As soon as the reset pulse of the monoflop 38 has subsided, the clock pulses from the start / stop oscillator 36 both start to clock the shift register 34 and at the same time count up the counter 44. The shift register 34 generates with each fed clock, starting from the code word 00000, each subsequent code word from the table according to FIG. 4, until the generated code word finally matches the code word that the five reading stations 19 deliver. When this state is reached, the output 33 switches from H to L, which stops the start / stop oscillator 36 and releases the load input 53 of the output register 51. The binary number that the binary counter will then appear at the output 52 of the output register 51 44 has reached until there is identity between the two code words, namely the one read by the reading stations 19 and the code word generated by the shift register 34. As can be seen from the above description, this binary number is one Number of steps that the trolley 4 would have to pass through in order to get from the beginning of the code carrier 11 to the detected position.

This number of steps is supplied to the central controller 15 via the conductor lines 22.

Since this counting process takes place in a much shorter time than that which the trolley 4 needs to cover the distance of the code mark length, i.e. to complete a distinguishable step, the current step numbers are reported to the central controller 15 via the conductor line 22.

Another possibility for converting the respectively read code word into the step number is shown in FIG. 7. Here, the conversion circuit 28 contains a ROM memory 55, into whose address inputs 56 the code word supplied by the reading stations 19 is fed via the lines 21. The ROM memory 55 then generates a binary number at its data outputs 57, which indicates the position of the code word in the table according to FIG. 4 and thus the step number at which the trolley 4 is located. The distance of the trolley 4 from the beginning of the code carrier 11 is thus equal to the code mark length multiplied by the step number.

For the sake of simplicity, the previous functional description of the new arrangement assumed that all of the reading stations 19 suddenly change the reading state at exactly the same time, that is to say synchronously, and do not slightly advance one reading station from another. In practice, this will be because of the division error of the code carrier 11 and the different response characteristics of the individual reading stations 19 cannot be achieved. If only one of the reading stations 19 switches spatially later than the others when passing the code carrier 11, an erroneous code word arises. Since the code words are neither lexicographically ordered nor contain redundancy, it cannot be decided based on the code word read whether an admissible code word is read or not. In order to bring about the decidability, each reading station 19 therefore contains three equidistantly arranged reading heads 58a, 58b and 58c, which are each formed by a photodiode or a phototransistor in the optically operating reading device 12. The reading heads 58a to 58c are arranged equidistantly and since the reading stations 19a to 19e from FIG. 8 are also distributed equidistantly, the distance between immediately adjacent reading heads 58 of adjacent reading stations 19a to 19e is equal to the distance between the reading heads 58 within a reading station 19a to 19e. The sets of read heads 58a .. 58c are nested one inside the other, ie all read heads with the reference symbol a belong to the left, those with the reference symbol b to the middle and those with the reference symbol c to the right sentence.

In order to distinguish which group of reading heads 58a to 58c is right in front of the code marks 17 and which happens to be unfavorably above a code mark boundary, the selection circuit 61 shown in FIG. 8 is provided. The selection circuit 61 contains three conversion circuits 28a to 28c, each of which has the structure shown in FIG. 6 and accordingly each of which also has an input 31a to 31c with five connections each. For example, all the read heads 58a of the adjacent reading stations 19a to 19e are connected to the conversion circuit 28a at the input 31a thereof. This means Tet that every third read head of the total of fifteen read heads, starting with the one on the far left, is connected to the conversion circuit 28a. Analogously, the heads 58b of the reading stations 19a to 19e are connected to the conversion circuit 28b, and finally all reading heads 58c of the reading stations 19a to 19e are connected to the input 31c of the conversion circuit 28c. In this way, three interlocking groups of reading heads are created, the code word of which is read, in each case being converted into a binary word independently of the other code words read in the conversion circuit 28a to 28c. Since the reading heads 58 are each at a distance from one another which is equal to a third of the length of a code mark 17, six cases can be distinguished from one another when reading five successive code marks 17. First assume that the read heads 58 are above the code marks 17, as shown in FIG. 8, then all three conversion circuits 28a to 28c deliver the same binary word at their outputs 52a to 52c. If, starting from this situation, the code carrier 11 has moved a little to the right, so that the boundaries between adjacent code marks 17 are at the reading heads 58a of the reading stations 19a to 19e, then this is the binary word obtained with these reading heads, that is to say the conversion circuit 28a uncertain, while the two groups of read heads, which contain the read heads 58b and 58c, read the same information and consequently their evaluation circuits 28b and 28c output identical binary numbers. The binary number supplied to the conversion circuit 28a can either be the next lowest if the code carrier is to the right is wandering or an arbitrarily different one.

The state that the two conversion circuits 28b and 28c supply the same binary number continues until the code carrier 11 has reached a position in relation to the reading station 12 at which boundaries between adjacent code marks 17 reach the group of reading heads 58 which consists of the reading heads 58b is composed. In this case, all three conversion circuits 28a to 28c may provide different binary numbers, but of which, as a simple geometric consideration shows, both the binary number that the circuit 28a supplies and the one that the circuit 28c generates is a correct binary number.

When the code carrier 11 is shifted further to the right, the boundaries between adjacent code marks 17 will finally pass between the reading heads 58b and 58c of each reading station 19a to 19e, so that the conversion circuits 28a and 28b output identical binary numbers at their outputs 52a and 52b.

On the basis of this case distinction, it can be seen which group of read heads 58a or 58b or 58c delivers correct results and which group produces an invalid result in otherwise error-free operation. If at least two binary numbers which are present at the outputs 52 are identical, this binary number reflects the true position of the reading device 12 or the trolley 4. If, however, all three binary numbers differ from one another, both the output 52a and the output 52c provide one true binary number, which differ from each other by one step, since one group of read heads, either 58a or 58c, is already reading the new code word completely, while the other group, i.e. 58c or 58a, still recognizes the old code word completely and without errors . It is therefore a matter of convention whether in this situation the binary number of the conversion circuit 28a or that of the conversion circuit 28c is passed on to the central control unit 15.

The selection circuit 61 therefore has two independently operating binary comparators 62 and 63 with the inputs 64, 65, 66 and 67, each of which can process five bits in parallel in this exemplary embodiment. Specifically, output 52a is connected to input 64, output 52b to input 65 and input 66, and finally output 52c to input 67. Furthermore, a multiplexer 68 is provided, which has two inputs 69 and 71, each five bits long, and comprises a five bit output 72. The multiplexer 68 is controlled at its two selection inputs 73 and 74, which receive their signal from comparison outputs 75 and 76 of the two binary comparators 62 and 63. In detail, the two inputs 69 and 71 are connected to the outputs 52a and 52b, as shown, while the selection input 73 is connected to the comparison output 75 and the selection input 74 to the comparison output 76.

Now, as explained in detail above, if the case occurs that the two conversion circuits 28a and 28b supply the same binary number as the conversion tion circuit 28c, both comparison outputs 75 and 76 are in the H state, which is why the multiplexer 68 switches the input 71 through to the output 72. As soon as, as in the example mentioned above, the code carrier 11 has migrated so far that only the two conversion circuits 28c and 28b now provide the same binary number, the output 75 changes to L, while the output 76 remains high. In this case too, the multiplexer 68 switches the input 71 through to the output 72. Only when the two conversion circuits 28a and 28b deliver the same binary number and the binary number of the conversion circuit 28c deviates after reaching the next state, does the binary comparator 62 generate an H signal at its output 75, while the output 76 goes to L. As a result, the multiplexer 68 is reversed and it now switches the input 69 through to the output 72. If, in the intermediate state, the boundary between adjacent code marks 17 is in front of the read heads 58b, all three binary numbers which are supplied by the conversion circuits 28a to 28c are different from one another, ie both binary comparators 62 and 63 supply an L signal at their output. In this case, the multiplexer 68 switches the input 69 through to the output 72, which corresponds to the state which is also switched on when the two conversion circuits 28a and 28b generate the same binary number.

The comparison circuit 61 is provided with two comparators 62 and 63 only because of the simpler understanding, because when setting up the truth table for switching the multiplexer 68 it is not difficult to see that the actuation of the multiplexer 68 is solely dependent on the signal on the Input 74 and thus the binary comparator 63 is dependent. In the case of an optimized circuit, the binary comparator 62 can therefore be omitted and the comparator is only controlled via a single selection input, namely the input 74.

It is thus possible, using three reading heads per reading station, to clearly recognize the position of the reading device 12 relative to the code carrier 11. The circuit shown for deciding which code word read is a correct code word is only an example and other circuits are also possible. Likewise, the use of optically working reading heads is only one example of conceivable reading heads. It is also possible to use read heads based on pneumatic or magnetic interference, for example pressure sensors or magnetic field probes, instead of photodiodes or phototransistors which interact with lamps.

Finally, it is possible to connect the conversion circuit 28 to the output of the multiplexer 68 and instead to compare the code words of the three sets supplied by the read heads 58a to 58c directly by means of a binary comparator, in order, for example, if the one read from the middle set is identical Pass the code word with the code word read from the right sentence, the code word read by the middle set of read heads and, if the code words of the middle sentence and the right sentence are unequal, to use the code word from the left sentence of read heads. The conversion takes place only after decoding the true code word.

The binary code shown for the code mark sequence has the advantage of particularly reliable readability. From the representation of the new arrangement, however, it is also easy to see that, instead of binary code marks, higher-value code marks, for example ternary or quaternary, can be used in the same way.

In order to be able to address a line length of 655.35 meters when using a binary code, 11 code words with 16 digits are required with a bit length of 1 cm on the code carrier. Accordingly, the entire reading head of the code reading device 12 has a length of at least 16 cm. If, on the other hand, a three-value code was used for addressing instead of a two-value code, a distance of 1771.46 m could be continuously addressed with an 11-digit code word length. At the same time, the read head would only have a length of approx. 11 cm, i.e. would have about two thirds the length of the read head for a 16-digit code with which only a third of the length of the line can be read or addressed.

As shown below, the aforementioned system can also be transferred to a three-valued code. For this purpose, the shift register when using a three-value code has the structure shown in FIG. 9 if three-digit code marks are used for reasons of a simplified representation. The circuit according to FIG. 9 contains a first modulo-3 adder 79 with two inputs, one of which is constantly supplied with a "1". With its output, the modulo-3 adder 79 is connected to a further modulo-3 adder 81 connected downstream, also with two inputs and one output, which ver with an input of a memory 82 is bound, the content of which corresponds to the position Q1 from the code word. The output of the memory 82 is on the one hand via a feedback line 83 at the second input of the modulo-3 adder 81 and also at an input of a downstream memory 84, the output of which is connected to the input of a third memory 85. This output of the memory 85 represents the output of the circuit for generating a pseudo random sequence with a three-value code. It is also connected to an input of a modulo-3 multiplier 86, the other input of which is constantly supplied with a "2". This modulo-3 multiplier 86 has the property of multiplying the number present at the output of the memory of the memory 85 by two and of making a number falling within the numerical range of the code. This means that if a "0" is present at the output of the memory 85, the modulo-3 multiplier 86 also supplies a "0" at its output, which is fed via a feedback line 87 into the second input of the modulo-3 adder 79 . If the output of the memory 85 delivers a "1", the modulo-3 multiplier 86 generates a "2" at its output and if the last option the memory 85 contains a "2", the modulo-3 multiplier 86 generates a "1"".

It is understood that each of the connecting lines shown between the modulo-3 adders 79, 81, the memories 82, 84, 85 and the modulo-3 multiplier 86 are multiple lines in order to transfer the numerical values from one circuit to the next. The passing on of the numbers from one memory to the next occurs with every cycle of a clock generator, not shown.

When the circuit shown in FIG. 9 is cycled, starting from the state 000 in the memories 82, 84, 85, the number combinations shown in FIG. 10 are successively obtained in the said memories 82, 84, 85. This table corresponds analogously to the table from FIG. 4.

11 shows how a three-value code can be represented on the code carrier 11. When using a transmissive scanning method, the code carrier 11, on which a "0" is to be displayed, is transparent, as shown at 88. The "2", that is the most significant digit from the set of characters, is read at those points at which the code carrier 11, as in 89, is designed to be opaque. The value "1" between the values "0" and "2", as shown at 91, acquires a lattice structure and transmits an amount of light that corresponds between the full shadowing by a code mark corresponding to a "2" and the full transmission of a code mark representing the "0". Otherwise, as before, all code marks are of the same length.

The section of the code carrier 11 shown in FIG. 11 thus contains the code marks corresponding to the number sequence 120020101. If one compares this number pattern with the table according to FIG. 10, it is not difficult to see that when the reading head reads the left three numbers, it reads a number 9, which can be obtained with the circuit according to FIG. 9 after the fourth cycle (it should be taken into account that the table can be read from left to right and the numbers on code carrier 11 from right to left). If the read head in FIG. 11 is moved, it detects the number sequence 200, which corresponds to the fifth code word number of the table speaks; etc.

A possible evaluation electronics for detecting the code marks on the code carrier 11 is shown in a highly schematic manner in a block diagram in FIG. The transmissive code carrier 11 extends between a group of light-emitting diodes 92 and a group of photodiodes or phototransistors 93. The number of light-emitting diodes 92 for lighting and the number of photodiodes 93 is selected in accordance with the exemplary embodiment explained with reference to FIG. 8 and is 3- times the number of digits that a code word contains. Since a three-digit code is selected in the present case, the number of photodiodes and light-emitting diodes is 9. These semiconductor components 92, 93 are acted upon or read out sequentially via multiplexers 94, 95. The two multiplexers 94 and 95 are shown schematically as mechanical switches, but, as is common today, they are electronic digital switches. The two multiplexers 94 and 95 are controlled via a control line 96 by a central evaluation and control electronics 97.

The input of the multiplexer 94 is connected to the supply voltage U and allows one of the light-emitting diodes 92 to be lit optionally by switching on the supply voltage. The output of the multiplexer 95, on the other hand, is connected via a line 98 to the input of an analog-digital converter 99, which has the task of converting the analog signal supplied on line 98 from the respective photodiode 93 into a digital signal, which, depending on the illuminance of the respective photodiode 93 corresponds to one of the three possible numerical values "0", "1" or "2". Analog-digital converters suitable for this are known and therefore no detailed description needs to be given. At its output 101, the analog-digital converter supplies the digital number corresponding to the number read to the central control and evaluation electronics 97 via a line 102.

The operation of the circuit explained so far is as follows: The two multiplexers 94 and 95 are actuated synchronously by the central control and evaluation circuit 97 via the control line 96. This activates a pair of light emitting diodes 92 and photodiodes 93 which are opposite each other with respect to the code carrier 11, in the sense that the light diode in question lights up due to the connection to the supply voltage U, while on the other hand the one belonging to this light emitting diode 92 and behind the code carrier 11 located photodiode 93 is switched to the analog-digital converter 99. The digital number read in this way is transferred to the central control and evaluation electronics 97, which in turn contains a linear memory which has a memory location for each photodiode 93, which can store numbers between "0" and "2".

As soon as all the photodiodes 93 have been connected to the analog-digital converter 99 once, after the two multiplexers 94 and 95 have been switched through, the central control and evaluation electronics 97 contain a complete pattern of the piece of code carrier read. Since, as mentioned, the photodiodes 93 are distributed in the same way as in the exemplary embodiment according to FIG. 8, there are three nested numerical values in the associated memory of the control and evaluation electronics, which now correspond, as in connection with FIG. 8 can be described, evaluated and implemented in the corresponding clock pattern. There is also the possibility of first converting the nested numbers obtained into the code word number or measure number and then carrying out the comparison as described in FIG. 8. For example, a precedence condition can be provided, insofar as the actual position of the cat 4 is the position that results when two code word numbers are the same or it is the lower of two code word numbers when two decrypted numbers in the code word number are " 1 "differentiate.

Instead of encoding the numerical values between "0" and "2" by gray values, as has been done in FIGS. 11 and 12, the numerical values can also be color-coded. Color coding allows even higher-quality codes in a simple manner. For example, in the exemplary embodiment according to FIG. 13, a four-value code is shown on the code carrier, the digits of which are encoded via the colors yellow, green, red and blue.

The circuit arrangement shown in the block diagram in FIG. 14 for reading a color-coded code carrier 11 contains illuminating devices 103 that emit punctiform light and emit white light as possible. The number of these lighting devices is again selected in accordance with the teachings in the exemplary embodiment according to FIG. 8 and the distance between the lighting devices is also such that the distance between adjacent lighting devices 103 corresponds to one third of the code mark length. The lighting devices 103 are on the input side of the multiplexer 94, which they one after the other with the supply voltage U and thereby lights up. On the other side of the code carrier 11 there is an optical system 104 which images all code marks lying within a code word length on a photodetector 105. The photodetector 105 consists, for example, of three photodiodes provided with corresponding color filters, so that only that photodiode generates a maximum output signal whose filter color matches the respective color of the code mark. It is also possible to use only three spectral colors red, green and blue as filter colors, the signal then being recognized correspondingly yellow if the photodiode for green light and that for red light deliver approximately the same signal amplitudes.

The photodetector 105 is connected to a color detector 107 via a plurality of lines 106, and each is connected to the color detector 107 by means of a suitable filter for a photodiode of the photodetector 105 which is sensitized to one of the spectral colors. In the selected example, these are three lines, because the color yellow is determined based on the signals on the lines for red and for green.

The color detector 107 provides at its output 108 a digital number which belongs to the color read on the code carrier 11 in accordance with the respectively selected table. The control and evaluation electronics 97 processes these digital numbers, as explained in connection with FIG. 12.

Because only one of the punctiform light sources 103 is activated in each case, the control and evaluation electronics 97 can recognize which “read head” is active, although only one common photo detector 103 is provided for all read heads. The photodetector 105 forms, as it were, with one of the light sources 103 a reading head corresponding to the reading heads 58 from FIG. 8.

Claims (18)

1.Device for position measurement in vehicles running along fixed tracks, preferably in crane and monorail overhead conveyors which have at least one running track along which a crane or trolley runs, with a code carrier (11) which carries code marks (17) along its longitudinal extent and with a code reading device (12), which sits on a trolley (4) or a trolley of the crane or the overhead conveyor, characterized in that the code carrier (11) is arranged along a running rail (2) of the crane or overhead conveyor that the code marks (17) on the code carrier (11) are arranged one behind the other in such a way that the code marks (17) are arranged according to a code mark sequence along the code carrier (11), each m consecutive code marks forming a code word, and that the code mark sequence is chosen such that an arbitrary sequence of m successive code marks (17) forming a code word each only appears once on the code carrier (11). 2. Device according to claim 1, characterized in that the code mark sequence has a period length of N = x ^m -1, where N is the number of code marks (17), x the value of a code mark (17) and m is a positive integer, which indicates how many code marks (17) form a code word. 3. Apparatus according to claim 1, characterized in that the successive code marks (17) of the code mark sequence are formed according to a pseudo random sequence, the value of the individual successive code marks (17) after an output signal of a linearly feedback m-digit shift register (Fig. 3) determined and according to a generating polynomial of the pseudo-random sequence output signals at the outputs (Q₁, Q₂, Q₃, Q₄, Q₅,) of the shift register (Fig. 3) logically linked and the result obtained is fed back to the input (D₁) of the shift register (Fig. 3). 4. The device according to claim 1, characterized in that the code marks (17) have a binary value. 5. The device according to claim 1, characterized in that the code reading device (12) has at least one set of reading heads (58), the number of which is at least as large as the number of digits of a code word and which is distributed equidistantly along the code carrier on the code reading device (11) are arranged, and that the center distance of adjacent read heads (58) belonging to the set is equal to the length of a code mark on the code carrier (11). 6. The device according to claim 1, characterized in that the code marks (17) on the code carrier (11) are gapless, such that adjacent code marks (17) directly adjoin each other without a space. 7. The device according to claim 5, characterized in that in addition to the first set of reading heads (58 a) at least two further sets of Read heads (58b, 58c) are provided on the code reading device (12), the relative distances within each further set of read heads (58b, 58c) being selected in the same way as in the first set of read heads (58a), and that these three sets of reading heads are nested one inside the other on the code reading device, such that there is at least one position between the code reading device and the code mark carrier (11) in which three immediately adjacent reading heads (58a, 58b, 58c) belonging to the three sets one and the other Scan the same code mark (17). 8. The device according to claim 7, characterized in that the three sets of read heads (58a, 58b, 58c) are connected to a selection circuit (61), the true code word from the signals output by the read heads (58a, 58b, 58c) determined and which forwards the true code word or a binary word derived therefrom to a signal output (72). 9. The device according to claim 8, characterized in that the selection circuit (61) has at least one digital comparator (63) with two sets of inputs (66, 67) and a control output (76), the one set of inputs (66 ) all read heads (58b) belonging to the middle set of read heads (58b) and to the other set of inputs (67) which are connected to one of the two adjacent sets of read heads (58a, 58c) read heads (58a, 58c), that the selection circuit (61) has at least one with its control Gang (74) to the control output (76) of the digital comparator (63) connected multiplexer with two sets of inputs (69, 71) and one set of outputs (72), that at the one set of inputs (71) all read heads (58b) belonging to the middle set of read heads (58b) are connected, and that the set of read heads (58a, 58c) which is not connected to the digital comparator (63) is connected to the other set of inputs (69) that the multiplexer (68) is switched such that, if the signals on the digital comparator (63) are identical, the middle set of reading heads (58b) to the output (72) and otherwise the set not connected to the digital comparator (63) is read through by read heads (58a, 58c) to the output (72), and that the sets of inputs (66, 67, 69, 71) and outputs (72) have a connection for each position of the code word. 10. The device according to claim 1, characterized in that it contains a conversion circuit (28 ... 28c) which converts the code word read from the code carrier (11) into a binary number, the value of which corresponds to the number of the code word within the code mark sequence which on the code carrier (11) is applied. 11. The device according to claim 10, characterized in that the conversion circuit (28 ... 28c) contains a shift register (34) which is fed back in the same manner as the shift register forming the code mark sequence (Fig. 3) that with the Shift register a start / stop counter (36), the clock signals of which are fed into a binary counter (44), that a digital comparator (29) is provided, which compares the code word read from the code carrier (11) by means of reading stations (19) with the code word from the shift register (34). compares the supplied code word and that the start / stop counter (36) is activated by a control circuit (39) if the read code word and the code word generated by the shift register (34) are not identical, both the shift register and the binary counter are reset, which increments the counter (44) and the shift register (34) successively generates the successive code words until the code word emitted by the shift register (34) matches the code word read by the reading stations (19), in order then to Stop counter. 12. The apparatus according to claim 10, characterized in that the conversion circuit contains a ROM memory (55) in which the number of the code word is stored under the address of the binary word, read by the reading stations (19). 13. The apparatus according to claim 1, characterized in that the code marks (17) have a higher than a binary value. 14. The apparatus according to claim 13, characterized in that the numerical values of the code used are shown as gray values on the code carrier (11). 15. The apparatus according to claim 13, characterized in that the numerical values of the code used on the code carrier (11) are shown as color values. 16. The apparatus according to claim 5, characterized in that each reading head contains a light source (92) and an associated light receiver (93), each forming a pair, and that within the code reading device (12) each have only one pair consisting of light source ( 92) and light receiver (93) is activated. 17. The apparatus according to claim 5, characterized in that each reading head contains its own light source (103), and that for all light sources (103) a common light receiver (105) is provided, such that a reading head (58) from its own light source (103) and the common light receiver (105) is formed. 18. The apparatus according to claim 5, characterized in that all read heads (58) of at least one set are activated simultaneously.

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