JPS61170803A - Sequence control method - Google Patents

Abstract

PURPOSE:To control a sequence at a high speed by dividing the operating state of a driven process into operating elements and executing only a necessary logical operation in accordance with the state of the divided operating elements. CONSTITUTION:A read-only-memory (ROM)4, a random access memory (RAM)5, etc. are connected to an arithmetic circuit 1 through a bus 10 to control a servo motor 8 and a contact circuit 9 through a servo I/O circuit 6 and a sequence I/O circuit 7 respectively. Since the logical operation of only a necessary part is executed during parallel processing flow, an execution table 2 and an execution end table 3 are formed, an logical operation part to be executed out of logical operations alpha-gamma or the like is discriminated and the discriminated part is registered in respective tables 2, 3. The logical operations including the positional command operation of a servo motor 8, e.g. starting of the servo motor 8, are executed in the order of registration. Consequently, sequence control can be attained at a high speed without operating all the logical operations.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to sequence control using a programmable controller, and particularly to a sequence control system that also uses continuous control based on instructions for sequence control. Regarding control method.

[Background of the invention]

An example of how to run a program on a programmable controller (hereinafter abbreviated as PC) is to scan the entire sequence control program as described in the April 1980 issue of the Journal of the Institute of Electrical Engineers of Japan, page 278. It is normal to run it while As PCs have come to be applied to various fields, they have come to handle continuous control such as analog control with feedback control based on commands while executing sequence control.

At this time, if a continuous system (servo motor positioning control, etc.) 'kPC'Jk that responds in a shorter time than the scanning time of the PC or scan time is used for control, continuous system calculations can also be performed as sequence calculations. If you try to execute it on the same flow as , continuous type calculations are more complex than sequence calculations and take longer to calculate, so there is a problem that the time for one scan including sequence calculations becomes longer.

Furthermore, as a result of the scanning time, that is, the sampling time becoming longer from the perspective of a continuous system, a problem arises in that a continuous system that responds in a shorter time cannot stably control the system.

[Purpose of the invention]

The present invention has been made to address the above-mentioned drawbacks, and its purpose is to provide a sequence control method that can control a continuous system at high speed and stably, and can also process sequence control at high speed.

[Summary of the invention]

The feature of the present invention is that the operating state of the controlled object is grasped, and logical operations for sequence control, including continuous system control, are executed only according to the operating state. be.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention.

FIG. 1 shows an example of driving a contact circuit consisting of relays and switches and a servo motor.

In FIG. 1, an arithmetic circuit 1 connects an execution table 2, an execution completion table 3, and a read-only memory 4 via a bus 1 (l).
, random access memory 5, servo input/output circuit 6,
It is connected to the sequence input/output circuit 7. As the arithmetic circuit 1, a microprocessor is used. The arithmetic circuit 1 operates according to instructions stored in the read-only memory 4, and is connected to the servo motor 8 and the contact circuit 9 via the servo input/output circuit 6 and the sequence input/output circuit 7t, respectively.
t-control. As will be described later, the execution table 2 and the execution completion table 3 are storage means for storing respective states on sequence control, and a part of the address of the random access memory 5 can be assigned to these. The read-only memory 4 stores instructions for operating the arithmetic circuit 1. Random access memory 5 temporarily stores data necessary for the operation of arithmetic circuit 1 according to its operation. The servo input/output circuit 6 operates in response to signals from the arithmetic circuit 1. That is, the servo input/output circuit 6 drives an amplifier (not shown) provided within the input/output circuit 6 in accordance with the deviation between the position command and the actual position of the servo motor 8. The output of the amplifier of the input/output circuit 6 is connected to the servo motor 8, and the rotational position of the motor 8 is controlled. On the other hand, the sequence input/output circuit -7 operates according to the signal from the arithmetic circuit 1. The input/output circuit 7 includes an output circuit that operates the contact circuit 9 and an input circuit that receives a signal from the contact circuit 9.

The output signal of the sequence input/output circuit 7 is connected to a contact circuit 9. The contact circuit 9 operates in response to a signal from the arithmetic circuit 1 or serves to send a signal to the arithmetic circuit 1. The configuration shown in FIG. 1 is characterized by having an execution table 2 and an execution completion table 3.

Next, the operation shown in FIG. 1 will be explained using FIGS. 2 to 4.

In a machine operated by a control device such as the one shown in FIG. 1, several operation elements are related to each other to form a flow, and these are usually processed by logical operations. FIG. 2 is a sequence processing flow showing this example. logic α
, β... and servo motor activation represent each operating element. Logic α.

β... is a calculation that executes logic such as starting a pump or starting a conveyor and stopping it after a predetermined time, and servo starting is, for example, starting a servo motor from Xl 25- to
This shows numerical operations such as rotation to l. In this operation, when a sequence instruction starts, logical α and β operations are executed in parallel. When the logical operation β is established, this logical operation is performed, and when the logical operation is established, the Wl award is performed at the logical η and θ. On the other hand, when the logical operation α is established, the activation of the servo motor and the logical operation r are further executed in parallel. If the logic r is established, then the logic δ is calculated. Then, when positioning by the servo motor is completed and logic a is established, a logic operation - is executed next.

Conventionally, sequence control with such logic is represented by a ladder diagram, and executed by running all the steps. In this case, the servo start calculation, that is, the 9 position command is calculated according to the time from the servo start at that time, but since the calculation execution time is relatively long, one sequence calculation is required. The execution time becomes longer. FIG. 3 shows the flow of a control method according to the present invention to avoid this. The feature is that control is executed while grasping the sequence control status using the execution table 2 and execution completion table 3 shown in FIG. That is, in order to execute only the necessary logical operations in the parallel processing flow shown in Figure 2, an execution table and an execution end table are provided, and it is determined which logical operations α, β, r, etc. should be executed. do. For this purpose, logical operations that may be executed are registered in the execution table 2. Furthermore, in order to determine which part of the operation has completed (logic is established) and whether it is okay to execute the next step instruction,
The logic whose operation has been completed is registered in the execution completion table 3.

FIG. 4 is a diagram illustrating the flow of FIG. 3.

Now, consider a case where the operation shown in FIG. 2 is processed. Assume that instructions for performing logical operations α and β are registered in the execution table 2 as shown in FIG. 4(a). First, according to the flowchart in FIG. 3, an instruction to perform a logical operation α is taken out from the execution table 2, α is deleted from this table 2, and it is determined from the execution completion table 3 whether or not the instruction has finished executing. be done. In this case, since the execution has not ended, the logical operation α is executed [FIG. 4(b)]. This calculation is performed by the calculation circuit 1, but the information necessary for the calculation is obtained from the contact circuit 8 through the memory 5 and the sequence input/output circuit 7, and the results of the calculation are output to the memory 5 and the contact circuit 8. Next, if logical α holds, logical operation α
The command to perform this is registered in the execution completion table 3 [FIG. 4(C)]. In the next step, since logic α is established, it is determined whether the instruction in the next step can be executed. In other words, if we look at starting the servo motor, which is one of the instructions for the next step after operation α, for example, if the positioning of the servo motor has not been completed, the previous work is still being performed. The command to start the servo motor cannot be executed. If the instruction of the next step can be executed, the instruction to perform the operation α is deleted from the execution completion table 3, and the instruction to start the servo and perform the logical operation rft of the next step is registered in the execution table 2 [Fig. d)].

Then, the process returns to the beginning of the flowchart in FIG. 3, and processing according to the state is executed. That is, the execution table 27, bea, s~5°7.2-1.ゎ7. It is deleted from the J execution table 2, it is determined that the execution of this instruction has ended, and the operation β is executed [FIG. 4(e)]. Next, it is determined whether the logical operation β holds true, and if it does not hold, the instruction for performing the calculation β is registered in the execution table 2 again. Next, when the command to complete the servo start is retrieved from the execution table 2, this command is deleted from the execution table and the servo start is executed in the same way as before [Fig. 4 (illustration)]. The final target position is calculated and sent to the servo input/output circuit 6.

The servo input/output circuit 6 controls the position of the servo motor 8 in accordance with this position command p*. The input/output circuit 6 uses the current position p of the motor 8 measured by a counter etc., and calculates the deviation p''
-p operates the amplifier and moves the servo motor 8. Position control is not completed immediately. That is, it is determined in the servo activation command whether the deviation p''-p is zero.

As a result, if the deviation p"-p is not zero, it means that the positioning has not finished, and the servo start command is registered in the execution table 2 again [Fig. 4 Φ)]. Next, the execution table The logical operation r registered in 2 is executed [Figure 4 (i)]. In this way, - life C 2 - + - nlf hole and 2 shi 1^1 mm crystal t lrp k are executed, and the operation 70- progresses.At this time, 1 is activated like a servo activation.
The processing is completed after one operation, and the command is executed repeatedly. As described above, the process is executed and positioning is finally completed. At this time, if the logic δ is also established and registered in the execution completion table 3 [Fig. 4 (J) 1, the logic δ and The servo start command is registered in the execution end table 3 (CJIE4 diagram QC)]. Next, it is determined whether the next step instruction can be executed based on the information in the execution completion table 3, and if the next step is to proceed, the logical instruction to be executed there is registered in the execution table. Figure 4 (a)].

In this way, an instruction whose processing cannot be completed in one operation will be executed repeatedly, making it suitable for processing in a continuous system such as a servo system. At this time, the calculation of servo activation is not performed by calculating the final goal as explained above, but is performed every time servo activation is performed according to the elapsed time t since the servo activation was first performed. The target position at that time may be calculated. That is, the time interval at which the position command should change is set to 1. Then, time 1p is (n-1)t+<tp(
nt, : (n is an integer), the position command at time 1 may be calculated as the target value at (n 1)t+. When a position command is issued using this calculation, continuous and smooth position control can be performed.

As described above, if logical operations including servo motor position command operations such as servo start are executed in the order registered in the execution table 2, all logical judgments (the first Since only necessary logical decisions are made based on the flow of the system's operation without performing the logical operations α to θ shown in FIG. 2, servo activation, etc., high-speed logical operations can be performed. For this reason, continuous systems such as servo systems are also activated in short cycles, allowing stable control of high-speed continuous systems. In addition, the execution table of FIG.

In the execution end table, instructions for performing each logical operation are registered, but since this table only needs to show which part of the operation flow shown in Figure 2, It is also possible to attach a symbol, register the symbol in a table, determine which logic should be executed, and then calculate the logic to be actually executed from the symbol to execute each logical operation.

Furthermore, the operation of the process may not only be represented using a flowchart as shown in FIG. 2, but also other methods may be used. For example, a method applying the IJ net graph may be used. FIG. 5 shows an example. The illustrated display method is characterized in that it is easy to grasp the status of operations including parallel processing.

Next, in the above example, a continuous command value, that is, a position command, is calculated in accordance with the time at each servo activation. However, if the period in which the servo activation command is executed is close to the response time constant of the servo system, the position command calculation may be performed as follows. That is, in the servo start command, only the conditions for calculating the servo motor position command may be calculated, and the position command value depending on time may be calculated at regular intervals.

FIG. 6 shows an example of a flow for performing this calculation.

FIG. 6(a) shows the flow of servo activation, and FIG. 6(b) shows the flow of position control activated at regular intervals. The position control calculation at a fixed period can be executed by the calculation circuit 1 as an interrupt calculation. As explained in FIG. 4, the servo activation shown in FIG. 6(a) is an operation executed at the same level as other logical operations, and is performed as follows. First, after starting the servo, if there is a change in the conditions for command value calculation according to the other machine's or its own logical calculation (including changes in the target value as a function of time), find this and store it in memory. This is used for position control, which will be described later. Next, the current position pt of the servo motor determined by the position control calculation is read out, and it is determined whether the final target position has been reached, and this routine ends. On the other hand, the position control flow shown in FIG. 6(b) is processed as an interrupt signal in the arithmetic circuit 1 at regular intervals. First, the conditions for the position command calculation calculated according to the flow shown in FIG. The actual position is calculated based on the signal from the position detector. As an actual example, when a pulse encoder is used as a position detector, the pulse signals from the encoder are counted by a counter and the current position signal p is used. The signal p is received from the input/output circuit 6. Then, the position signal pt is stored in the memory. Next, the positional deviation p"-pt
A signal corresponding to the calculation is output to the servo input/output circuit 6. Then this routine ends. In addition, in the input/output circuit 6, the power amplifier is operated with a signal corresponding to the deviation p''-pK, and the servo motor 8 is driven by the signal.
control. As is well known, in this control method, the amplifier may be driven directly according to p''-p, or the speed control system of a minor loop may be operated according to p''-p. Then, the position deviation p''-p'! However, the calculation circuit 1 calculates only the position command pm, and the calculation of the position deviation p"-p is performed by the input/output circuit 6.
You may also do this using Furthermore, in the above example, the continuous system to be handled is one of l systems, but it goes without saying that a plurality of systems of l or more systems may be handled. - On the other hand, as a continuous system, not only the positioning of the servo motor but also the speed control that controls the rotation precision to a specified level may be used. Similarly, torque control may be used. Moreover, it goes without saying that the continuous system is not limited to a system related to a servo motor, but may be any other continuous system.

〔Effect of the invention〕

As explained above, according to the present invention, the operating state of a driven process is divided into operating elements, the operating elements are upgraded, and the operating state is grasped, and only the necessary logical operations are performed according to the state. This enables high-speed and stable continuous system control, and even higher-speed sequence control. This allows continuous system control and sequence control to be configured in any proportion on the same arithmetic unit, and these controls can be executed, which not only allows the entire device to be compact and economical, but also allows for
It is possible to provide a flexible control device that is not controlled by the controlled object.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of the operation of a process to which the present invention is applied, FIG. 3 is a control flowchart of the present invention, and FIG. 4 is a diagram according to the present invention. FIG. 5 is a process operation description example, and FIG. 6 is a flowchart showing another implementation method of the present invention. 1... Arithmetic circuit, 2... Execution table, 3... Execution end table, 4, 5... Memory, 6... Servo input/output circuit, 7... Sequence input/output circuit, 8・
...Servo motor, 9...Contact circuit.

Claims (1)

[Claims] 1. In a system that decomposes the motion of a controlled object into motion elements and combines them to perform motions in a predetermined order, select one of the motion elements to be operated. A sequence characterized in that only the operations of the operation elements to be operated are sequentially executed, such that after taking out the operation element and performing a logical operation or numerical operation on the operation element, the next element to be operated is extracted and the above operation is performed. Control method.