JPH0319563B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a programmable controller (sequence controller) using a mark flow graph. Mechanical production systems are often referred to as discontinuous production systems, but the term "discontinuous" means that the workpiece progresses through each stage of the production process in sequence, with operations specific to each stage (processing, transportation, inspection, assembly, etc.). etc.), but in doing so, there is essentially a discontinuity in that each process passes through a gap and moves on to the next process. In such a system, for example, if a process is in progress, this state is interrupted by the occurrence of an event called finishing of processing, and then a new situation of unloading occurs. A system that operates through an alternating connection of situations and events in this way is called a discontinuous system. Many such discontinuous systems exist in the activities of society, but in production systems, the parts in particular that involve sequence control can be said to be discontinuous systems. In other words, in a discontinuous system, there is a flow of control, a flow of data, and a flow of objects, and it can be said that sequence control corresponds to the flow of control. Drum-type sequencers have traditionally been used for sequence control as described above, but they have many problems such as durability and program changes, and they have drawbacks such as being able to only implement pure program control type sequence control. Ta. In addition, pinboard type sequencers have also been widely used, but
There were many redundant hardware parts, the scale of the hardware was large, and it had drawbacks such as being unsuitable for expressing complex logic and internal memory. Furthermore, general-purpose sequence control using computers has also appeared;
The drawbacks are that the program is complex and expensive. Programmable controllers have been proposed in response to this situation. This programmable controller introduces computer technology to realize the generalization of sequence control, which has been a problem in sequence control, and also provides a convenient sequence control device, and is designed to incorporate software and hardware. It has been designed with a lot of innovation so that even people with little computer knowledge can easily use it. Conventional programmable controllers use an interpreter format to facilitate program changes, but have the drawback of slow processing speed due to translation work. Furthermore, when a compiled format is used to speed up processing, there is a drawback that program changes become complicated. Therefore, the purpose of this invention is to solve the above-mentioned problems.
An object of the present invention is to provide a programmable controller without any drawbacks, and the present invention uses a mark flow graph to simplify the controller configuration and program input. This invention will be explained below. First, the mark flow graph on which this invention is based will be explained. In order to design and purposefully control a production system as a discontinuous system, a means or tool to express the system is very important. It must be something that can be expressed. (2) The expression can be applied from the conceptual level to the detailed level. (3) Be effective in exchanging information between the parties. (4) Be effective in system analysis and design. The following conditions are desired. The mark flow graph satisfies these conditions (1) to (4) and is composed of the following elements. That is, boxes as shown in _b1 to _b6 in FIG. 1 are used to represent situations, and transitions as shown in _t1 to _t5 in the same figure are used to represent events. Also, situation b ₁ ~
The first example shows the connection between b ₆ and events t ₁ to _{t 5} .
Directional branches as shown in d ₁ to _{d 12} in the figure are used, and a mark m is used to indicate the currently held situation b. Note that, as shown in FIG. 1, box b and transition t are always connected alternately by directional branches d, and there is no limit to the number of directional branches d that enter and exit box b and transition t. In addition, Figure 2 shows an example of a mark flow graph that includes "conflicts", but "conflicts" involve changes in a certain situation related to multiple events, and differ depending on how early or late these events occur. It means to be in a situation. Next, rules on the mark flow graph corresponding to the occurrence of events (transitions) and changes in situations (boxes) will be explained. If there is no unmarked box on the input side of a transition and no marked box on the output side, that transition is said to be fireable, and the transition that is fireable can be fired externally. If permission is added and suppression of firing is released, firing will occur at that transition. This corresponds to the occurrence of an event. Note that since firing occurs within an infinitesimal time, multiple transitions will not fire at the same time. Further, by firing, marks in all boxes on the input side of the transition disappear, and marks are generated in all boxes on the output side. That is, in FIG. 1, transition t ₁ is currently firing, but after transitions t ₁ and t ₂ are fired in that order, transitions t ₃ and t ₄ are fired independently. There is no order of priority between them. In other words, it shows that parallel operations are performed at transitions t ₃ and t ₄ , and after transitions t ₃ and t ₄ are fired, transition t ₅ can be fired, and even with this firing. Mark m returns to box b ₆ . Further, in FIG. 2, after the firing of the transition _t1 , when the mark m enters the box _b1 , all of the transitions _t2 to _t4 become firing possible. Since the transitions cannot fire at the same time, either transition t ₂ or t ₄ will fire. In this way, transitions in which the firing _of one makes the other non-firing are said to be in conflict with each _other . A box with directional branches is called a conflict box. If multiple transitions among the transitions connected to this conflict box are fireable, only one of the fireable transitions can fire, and if one fires, the others The transition is non-firing. Furthermore, in the mark flow graph, even if a mark transition occurs due to firing, the number of marks in a box is at most one. This shows that the markflow graph is essentially safe, and since the number of marks is "0" or "1", it is advantageous for logical handling. This shows that the markflow graph is effective for sequence control. In actual sequence control, it is necessary to take specific ignition permission and ignition inhibition into account, and this is accomplished by, for example, permitting gates x ₁ and x ₃ and inhibiting gate x ₂ as shown in Figure 3. All you have to do is add .
Signals from outside the controller, ie input signals to the controller or box variables, will be applied to these gates. Furthermore, the box indicates the output to the outside or the internal status of the controller. In this case, the box
Box variable b _i for B _i , transition T _j
The transition variable for tj is represented by _tj , the gate signal of the inhibition gate or permission gate is represented by _xk , and if there is a mark, b _i = “1”, if there is no mark, it is “0”, and if it is fired, it is t Let _i = “1”. According to this, for example, the transition t ₁ in Fig. 3,
The ignition condition indicating the ignition at t ₂ can be expressed as t ₁ = (b ₁・ b ₂・₃ )・x ₁・₂ t ₂ = (b ₃・₄ )・₃ ... (1), It is assumed that ignition occurs when the condition becomes "1". Now, when applying the markflow graph as described above to a programmable controller program that applies the principle of markflow graph,
A mark flow graph as shown in FIG. 4 is described using a connection relation table, a gate condition table, and an arbiter table as shown in Tables 1 to 3 below.

【table】

【table】

【table】

[Table] Here, the connection relationship table (Table 1) focuses on transitions and lists the box numbers connected to the transitions, distinguishing between input and output sides. A positive number indicates that the box is connected to the output side of the transition, and a negative number indicates that the box is connected to the input side. The gate conditions are similarly expressed in the gate condition table (Table 2). This also focuses on transitions and lists the gate branch numbers to those transitions.
However, B for internal gates and E for external gates.
Add in front of the number, and if it is a deterrent gate, add a negative sign. In addition, the conflict box requires adjustment of the arbiter (adjustment function). An arbiter table (Table 3) is created that lists the numbers of transitions to be arbitrated by the arbiter, that is, the numbers of transitions that conflict with each other. If such a format is adopted, it corresponds well to the graph and is easy to understand even when handled by a human, so inputting and changing is easy. The processing operation of a programmable controller that applies the principle of mark flow graph as described above is as follows.
The flowchart will be as shown in Figure 5. That is, first, the firing condition of each transition is tested (step S10), then arbitration is performed by the arbiter (step S30), and finally, the transition with the firing condition of "1" is fired and the mark is set. The transition is executed (step S40). However,
In this invention, in order to perform processing at high speed, internal information is in the following format. In other words, in the connection relationship table and gate condition table, the corresponding latch numbers are stored in the table instead of the box number or external gate number, and the same is true for the arbiter table. Instead, the memory addresses that store information on whether a transition can be fired or not can be used as a table. A detailed explanation will be given below using a specific example. As shown in FIG. 6, the connection table and gate table secure a 48-byte memory area for one transition. The first byte of these indicates whether the transition is used or not, and if it is not used, "0" is written. Thereafter, the latch numbers corresponding to the box numbers and external gate numbers are stored in 2-byte units in the order of input-side box, output-side box, permission gate, and inhibition gate.
In this example, 8 bytes are planned for the input side box, 4 bytes for the output side box, 6 bytes for the enable gate, and 6 bytes for the inhibit gate, and 2 bytes of "0" are written in the delimiter between each block to block. We are trying to identify the In addition, the arbiter table reserves 16 bytes for each arbiter.
The first byte of these is a pointer, which is used to store the number of transitions to be allocated this time. From then on, the memory address storing the transition information is stored 2 bytes at a time, and after the last transition, 2 bytes of "0" are written to indicate the end. This situation is shown in FIG. Furthermore, the transition information storage table shown in FIG. 8 is a table that stores whether a transition (T ₁ to _{T 32} ) is a fireable or non-fireable transition, and each transition has one byte and an address of 1. I try to secure it every few days. However, when the ignition is possible, bit 7 =
"1", and when it is not possible to fire, bit 7 = "0" is stored, and bits 6 to 0 are set to "1". Further, in this invention, in order to speed up processing, the starting address of each transition in the connection table and the starting address of each arbiter in the arbiter table are tabulated. Then, each address is 2 bytes each, T1, T2,
They are arranged in the order of T3, ...T32, A1, A2, ...A16. Note that the table at this first address is placed immediately after the transition information storage table. In addition, (00) ₁₆ is stored at address 0000 to separate the connection table and gate table and to detect the end of the arbiter table, and 1 byte is used to store the maximum value of the transition number used in the mark flow graph. One byte is used to store the maximum value of the number. Prior to testing the ignition conditions, the external gate signal is first latched to prevent malfunctions even if the gate conditions change within one scan. Thereafter, a test is carried out to determine whether the ignition conditions are satisfied using the connection relation table and the gate condition table, the details of which will be explained with reference to FIG. That is, to test the firing conditions of each transition, first determine whether the transition is being used (step S).
11) If it is used, it is determined whether there is an input side box (step S12). Then, if there are input-side boxes, it is determined whether or not there are marks in all the input-side boxes (step S13), and if there are marks in all the input-side boxes, it is determined whether there are output-side boxes (step S13). Step S1
4) If there are output boxes, it is determined whether or not there are no marks in all the output boxes (step S15). If there are no marks in any of the output boxes, it is determined whether or not there is a permission gate (step S16), and if there is a permission gate, it is determined whether or not all the permission gates are "1". (step S17). If all the permission gates are "1", it is determined whether there are any further inhibition gates (step S18), and if there are inhibition gates, all of the inhibition gates are "0".
It is determined whether or not (step S19). If all of the inhibition gates are "0", this transition is ignitable, so the process proceeds to the next transition test (step S20). In addition, in each of the above processing steps, if the enabling conditions are not met, such as when a transition is not used, when there is a box without a mark on the input side, or when there is a box with a mark on the output side, the permission gate is If there is a value other than "1" in the transition gate, or if there is a value other than "0" in the inhibition gate, it is determined that this transition is not ignitable (step S21). Also,
If there is no input box, no output box, no permission gate, or no inhibition gate, the process advances to the next step. If the state of the test of the transition shown in FIG. 9 is shown in more detail, a flowchart as shown in FIG. 10 will be obtained. As mentioned above, once all the firing conditions for each transition have been tested, the next arbiter will move on to the arbitration process.
It is as shown in the figure. That is, it is determined whether or not there are transitions that can be fired among the transitions that conflict with each other (step S31);
If there is a fireable transition, it is determined whether the transition indicated by the pointer is a fireable transition (step S32). If this transition is fireable, transitions other than the transition indicated by the pointer are set as non-fireable (step S34), and the process proceeds to arbitration for the next conflict box. If there is no fireable transition among transitions that conflict with each other, the next conflict box is arbitrated, and if the transition pointed to by the pointer is not a fireable transition, the pointer is moved to the next transition. Proceed to step S3
3) It is determined whether the transition indicated by this pointer is a ignable transition. After all the conflict boxes have been arbitrated by the arbiter in this way, the ignitable transition is fired (step S40).
The details will be explained with reference to FIG. 12. That is, first, it is determined whether or not this transition can be fired (step S41), and if it is, all the marks in the boxes on the input side are erased (step S42), and the marks on the output side are Generate marks in all boxes (step S43),
Proceed to the next transition firing operation. If the corresponding transition is not fireable, the process proceeds to the fireable operation of the next transition. As described above, according to the programmable controller of the present invention, since the connection relationships and gate conditions are listed in the table of addresses corresponding to the boxes and gates, the 8-bit microprocessor M068609 (2M
Hz), the time required to test one condition is 8.0 microseconds, and the time required for a mark to appear or disappear is 9.0 microseconds per box. Furthermore, if even one condition is not met, it is immediately determined that the arc cannot be fired, so all conditions are tested only in the case that the arc can be fired. For this reason,
The processing speed will be further increased. On the other hand, changing the program is extremely easy as all you have to do is rewrite part of the table based on changes in the mark flow graph, and since it has an arbiter function,
There is no malfunction in the conflict box,
Firing rights will also be distributed equally.

[Brief explanation of the drawing]

Figures 1 to 4 are diagrams for explaining the mark flow graph that is the premise of this invention, and Figure 5
The figure is a flowchart showing the processing steps of the present invention, Figures 6 to 8 are diagrams each showing the state of the memory of the invention, and Figures 9 to 12 are detailed processing steps of the flowchart in Figure 5. It is a diagram showing steps. _t1 to _t6 ...transition, _b1 to _b6 ...box, _d1 to _d12 ...direction branch, m...mark.

Claims (1)

[Scope of Claims] 1 (a) A sequence control system that includes a box that expresses a situation, a transition that expresses an event,
It is described using a mark flow graph that uses directional branches that express the connections between the situations and events, and marks that indicate the currently held situations, and (b) there is no box in which no marks can be placed on the input side of the transition. , and there is no box with a mark on the output side, it is defined as a firing possible transition, and if a firing permission is added from the outside to a transition that is a firing possible transition, and the firing suppression is released, the firing is possible. occurs, and the marks in all boxes on the input side of the transition disappear due to the firing, and marks are generated in all boxes on the output side. (c) Connection to the output side of the same box A group of transitions connected to the input side of the same box or a group of transitions connected to the input side of the same box are defined as conflicts with each other. Or, in the output signal memory, "1" and "absence" correspond to "0", and furthermore, the signals for the enable gate and inhibit gate are stored in the input signal temporary memory, or "0" from the memory corresponding to the box. ，
(e) Based on the preconditions in (a) to (c) above, (i) Whether or not a transition is used, and for the transition used, whether or not there is an input box for the transition. , the presence or absence of a mark in the input side box, the presence or absence of an output side box, the presence or absence of a mark in the output side box, the presence or absence of an enable gate and the conditions, and the presence or absence of an inhibition gate and the conditions to determine whether or not each of the above transitions can be fired. (ii) particularly for transitions that are in conflict with each other,
If there is a transition that can be fired, it is determined whether or not the transition indicated by the pointer can be fired, and if it is possible, the transition other than the transition indicated by the pointer is disabled. If it is not possible, the pointer is moved to the next transition that can be fired, and the arbitration function performs the same judgment and processing as to whether or not firing occurs, ( iii) As a result of the above judgment, for all the transitions in which ignition can occur, the marks in all the boxes on the input side are erased and the marks are generated in all the boxes on the output side, (f) Step (a) 1.) A programmable controller characterized in that a sequence control system is programmed according to steps (i) to (iii) and step (d), and equipment is controlled by input/output signal formats according to the processing steps (i) to (iii) and step (d).