JPH02290177A - Control of driving of servomotor for serial printer - Google Patents

Abstract

PURPOSE:To prevent the overshoot of a carriage speed due to a load fluctuation and the generation of the overrun error of CPU process by a method wherein the driving of a carriage driving motor is stopped when a limit speed is exceeded during sensor slit offering process from the carriage driving motor. CONSTITUTION:When a carriage speed V has exceeded a limit speed VC, the driving of a motor is cut off. The value of the speed VC is between the station ary speed VT of a carriage and an objective control speed V1 and is higher than the stationary speed VT of the carriage by about 5%. In the condition of V>=VC, a current conducted through the motor follows the ratio a background processing time, occupying in an unit time, to the processing time of an IPT.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to a servo motor drive control system 1'B of a serial printer.
It is about the method.

(Prior Art) Conventionally, in a servo motor drive control method for a serial printer, a servo motor drive IT flow value is determined according to a command value calculated based on the following equation. That is, the current rotation speed of the servo motor is V, the control target value of the servo motor is 1, and the limit value of the rotation speed of the servo motor corresponding to the processing capacity of the control section is V.
c (vc < Vl), and the gain of the servo system is G
When V≦V, K=( V, -V) ・G When Ve≦V<Vl (7), K=0 ■, When ≦V, K=-( V.-V)C ．． (The problem that the invention attempts to solve! is executed with priority over background processing,
If the carriage speed increases due to load fluctuations and overshoots, there is no longer enough time for background processing to be executed, and the above calculation process itself is not executed. As a result, even if the current rotational speed of the servomotor exceeds the limit value of the rotational speed of the servomotor corresponding to the processing capacity of the control unit and vc≦V, the command value K does not become 0. Then, the motor may not be stopped and the speed of the carriage increases, causing problems such as runaway movement. Therefore, it is necessary to provide a margin for the CPυ processing so that the background processing can be executed sufficiently. However, variations in carriage load fluctuations are caused by temperature,
It depends on humidity, accuracy of mti part, etc., and it is difficult to predict accurately at the time of firmware design.
It is necessary to provide a larger margin for IJ processing than necessary. The present invention solves the problems of the conventional servo motor drive control method for serial printers as described above, and when speed control is performed in background processing by firmware processing, the carriage speed overshoots due to load fluctuations and the CPυ processing is Prevents overrun errors from occurring and prevents excessive CP.
The purpose of this invention is to provide a servo motor drive control method for a serial printer that makes it unnecessary to set a U processing margin. (Means for Solving the Problems) For this purpose, the servo motor drive control method for a serial printer of the present invention is a serial printer that controls the drive current supplied to the servo motor to control the rotational speed of the servo motor by a program. In the servo motor drive control method, the current rotation speed of the servo motor is V, the control target value of the servo motor is
vc<vt) and the gain of the servo system is G. When V≦V1, K- (V, -V)C; when V>Vl, K-- (V.-V)G. The drive current value of the servo motor is determined according to the command value calculated based on the command value, and this is executed in background processing. ■When ≥Vc, the drive current value of the servo motor is determined according to the command value calculated based on This is executed by interrupt processing using an interrupt signal generated from the encoder attached to the servo motor. (Function) According to the present invention, as described above, the current rotational speed of the servo motor is set to ■, and the control target value of the servo motor is set to V. When the limit value of the rotational speed of the servo motor corresponding to the processing capacity of the control unit is vc (v.<v1), and the gain of the servo system is G, when ■≦■1, K= (V , -V)G When V>V, the drive current value of the servo motor is determined according to the command value calculated based on K=-(V.-V)G, and this is executed in background processing. , When V≧Vc, the drive current value of the servo motor is determined according to the command value calculated based on K=0, and this is executed by interrupt processing using an interrupt signal generated from the encoder attached to the servo motor. Therefore, even if overshoot occurs due to load fluctuation of the cartridge, the
Firmware processing time limits are not exceeded.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 2 is a schematic structural diagram of a serial dot printer to which the servo motor drive control method for a serial printer of the present invention is applied.

In the figure, a print head 12 is mounted on a central ridge portion 11 of a Syrian dot printer, and is movably attached to a carriage shaft 10. A drive gal 13 is fixed to the shaft of the DC servo motor 8, and a drive belt 9 is stretched between the drive gal 13 and the idle pulley 1715. The carriage body 11 is fixed to the drive belt 9.

At the rear of the DC servo motor 8, an encoder l7 consisting of a slit disk 16 fixed to the motor shaft and a photosensor l4 is attached, and the slit disk l6
A plurality of slits are formed in the.

The Surinoto disc l6 and the photosensor l4 constitute a two-phase encoder, which outputs two pulse signals having a constant phase difference at every constant rotation angle of the DC servo motor 8. This output allows the rotation speed, rotation angle, and rotation direction of the DC servo motor 8 to be detected. FIG. 1 is a block diagram of a control circuit for rotating the DC servo motor 8 and moving the carriage portion l1 according to the servo motor drive control method for a serial printer of the present invention.

This control circuit 111 is an R
It consists of an OM (read only memory) 2, a RAM (random access memory) 3 that stores data processed by a program, a motor drive circuit 5, and a speed detection/interrupt generation circuit 6. The moke drive circuit 5 sends out a drive signal to rotate the DC servo motor 8, and is composed of a circuit as shown in FIG. 3, for example. According to the motor drive circuit 5, the rotation direction of the DC servo motor 8 is set by giving the forward rotation command F〇1 signal and the reverse H rotation command REV signal, and the current flowing to the DC servo motor 8 is controlled by the duty amount setting signal. ? It is possible to set the amount of deity, which will be described later, using IL.

That is, as shown in FIG. 4, when setting the duty amount to 100, the duty amount setting signal is held in the ON state, and the current flowing through the DC servo motor 8 becomes maximum.
Further, when setting the duty amount to 50, the ON state and OFF state of the duty amount setting signal are set to be the same time, and the duty amount setting signal is turned ON and OFF intermittently. At this time, the current flowing through the DC servo motor 8 is the maximum current of 50χ. moreover,
When setting the duty cost to O, the duty amount setting signal is turned OFF and the current flowing through the DC servo moke 8 is set to O. In this way, by intermittently turning ON and OFF the duty setting signal by changing the ON and OFF times, the current flowing through the DC servo motor 8 is changed, and the torque of the OC servo motor 8 can be arbitrarily set. I can do it. Next, FIG. 5 shows the Essihalus generation circuit constituting the speed detection/interrupt generation circuit 6, and FIG. 6 shows a time chart of the edge pulse generation circuit. The edge pulse generation circuit 5l receives two-phase signals φA and φB from the encoder l7 in order to detect the speed of the DC servo motor 8.
This circuit detects the rising and falling edges of , and generates pulses corresponding to each edge.
That is, as shown in FIG. 6, the gate l output is obtained from the rising and falling edges of φA, the gate 2 output is obtained from the rising and falling edges of φB, and the gate 1 and gate 2 outputs are obtained from the gate 3. is input and an edge pulse is output. FIG. 7 is a diagram showing the speed detection circuit, and FIG. 8 is a time chart of the speed detection circuit. In the figure, a speed detection circuit 71 is for measuring the time between edge pulses by counting the interval between edge pulses generated by the edge pulse generating circuit 5l using a constant clock. The measured time is 8
Bit binary counter 72 and 8-bit latch circuit 7
Output via 3. Here, the distance that the carry Fuji moves within the time corresponding to the edge pulses generated based on the signals φA and φB from the slit sensor is expressed as l.
Then, l is a constant determined by the physical size of the sensor slit. Therefore, the moving speed V of the carriage is v-
17(Nx tctw). Here, N: number of counts (number of clocks) between edge pulses tcl
: The time is one clock. Next, FIG. 9 shows the interrupt generation circuit, and FIG. 10 shows the flowchart of the interrupt generation circuit. Interrupt generation circuit 9l
Is this the IP for starting the firmware printing process? It generates a signal, and edge pulses are counted and output according to the printing density. In other words, if you use an encoder that outputs an edge pulse once every 1/480', 120 dots/
If you want to print with inch dot density, IP? It is necessary to output the output at a rate of once every four edge pulses. Therefore, as shown in FIG. 9, the IP? Get a signal.

In the printer configured as described above, the relationship between background processing and IPT processing is shown in FIG. 11, and flowcharts of a program for controlling the speed of the carriage are shown in FIGS. 12 and 13. No.! In Figure 1, background processing is in a loop and is constantly running. On the other hand, the IP↑ process depends on the carriage running speed and print density, as shown in FIG. 10, and interrupts the background process asynchronously. In the above program structure, carriage speed control is performed in background processing. Figure 12 shows a flowchart of speed control during background processing. Step ■ Read the count value N from the speed detector iff71 (see Figure 7). Step ■ Calculate the recarriage speed V from the read count value N. V = j! /(N X tctx) step■
The magnitude relationship between the current carriage speed V and the target vI in carriage speed control is determined. Step■ V≦V. If , the carriage speed has not reached the target speed, so processing is performed to add acceleration torque. That is, the speed difference between the target speed V and the carriage arrival level V is determined, and the magnitude K of the acceleration torque is calculated by multiplying the speed difference by the system gain G. Step ■ If V>V, the carriage speed exceeds the target speed, so a process of adding deceleration torque is performed. That is, the speed difference between the carriage speed V and the target speed v1 is determined and multiplied by the system gain G to calculate the magnitude K of the deceleration torque. Step ■ To generate deceleration torque in the DC servo motor 8, set the rotation direction of the motor in the opposite direction. Step ■ The magnitude K of the acceleration torque or deceleration torque calculated in step ■ or ■ is converted into a current value flowing through the DC servo motor 8, and further converted into a duty amount corresponding to the current value. Step ■ Output the duty amount converted in step ■ to the motor drive circuit 5. By repeating the above process, the carriage speed can be made to follow the target speed. However, the friction between the carriage and the carriage shaft P! Change, l1 by ribbon
! When friction changes occur, the carriage speed may overshoot and the speed may exceed the target speed.
The steady deviation between the steady speed of the carriage and the target speed is usually
Since the target speed is 15x to 20x, the time margin for firmware processing is required to be at least the above-mentioned steady-state deviation so that CPυ does not overrun even if the carriage reaches the target speed.

Additionally, if the load fluctuations become larger than expected at the time of design due to device variations, CPU overruns occur. Therefore, the process according to the flowchart shown in FIG.
Carry out the process using chlorine.

In this process, the carriage speed V is the riminoto speed ■. If the value exceeds 0.005, the motor drive will be cut off. Also, vc
is the steady speed of the carriage.
, and is about 51 times faster than the constant constant speed of the carriage.

Step ■ Read the count value N from the speed detection device 71 (Fig. 7). Step @ Calculate the carriage speed ■ from the read count value N. V = 1/(N x tctw) step @ The magnitude relationship between the carriage speed ■ and the carriage speed limit value vc is determined.

If ■≧■, then the carriage speed V is the limit value■. Since it exceeds , proceed to step 0 and turn off the motor drive.

If vc, proceed to another IPT processing step [phase]. Step O Outputs the duty amount 0 to the motor drive circuit 5,
Drive the mork and proceed to step ■. Step ■ Execute other processing within rPT.

FIG. 14 shows a time chart when other processing is performed within the IPT.

In the figure, (a) is the IP? when V<vc? A time chart of processing, background processing, and motor current is shown. ■〈Since it is VC, the motor current is not cut during IPT processing. Therefore, the motor current is controlled according to the value corresponding to (V-V)G set by speed control performed in background processing. Next, (c) shows the case of V,>V≧Vc. Since V≧Vc, current is cut during IPT processing, and a current corresponding to (V, -V)C is set during background processing. In this case, the motor current flows intermittently as shown in the motor current in FIG. 10(b), reducing the acceleration torque.

When V≧Vc, the current flowing to the motor follows the ratio of the background processing time to the IPT processing time per unit time. As the ratio of IPT processing time increases, ′ζ, DC
The current flowing through the servo motor 8 decreases, and when the background processing time becomes 0, that is, when the firmware processing reaches the limit, the motor current becomes O as shown in (C), and the acceleration torque is applied to the DC servo motor 8. will no longer be added. Here, vc is 5χ than the steady speed V↑ of the carriage.
Since the speed is set to high, the carrying speed usually does not exceed vc. Even if the limit is exceeded due to overshoot due to carriage load fluctuation, the firmware processing time limit will not be exceeded, and overrun of CPυ due to insufficient firmware processing time can be prevented.

In addition, the processing limit of the firmware can be increased by just 5z higher than ■, and the CPU utilization efficiency can be increased.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention. (Effects of the Invention) As described above in detail, according to the present invention, the current rotational speed of the servo motor is V, and the control of the servo motor) 7
Let the J target value be V, and the limit value of the rotational speed of the servo motor corresponding to the processing capacity in the control unit be vc (V
c < V + ), and the gain of the servo system is G. When V≦Vl, K= (V.-V)G When V>V, K=- (V,-V)G The drive current value of the servo motor is determined according to the command value calculated based on this, and this is executed in background processing, and when V≧Vc, the drive current value of the servo motor is determined according to the command value calculated based on K=0. The value is determined and executed during interrupt processing using an interrupt signal generated by the encoder attached to the servo motor, so even if reovershoot occurs due to carriage load fluctuation, Firmware processing time limits are not exceeded. Therefore, if the speed exceeds a certain limit during sensor lift interrupt processing from the serial printer's carriage drive motor, the carriage drive motor is stopped, so the carriage speed is automatically adjusted. This can be kept below the processing limit of the firmware. Furthermore, it is possible to prevent CPυ overruns and reduce the margin of firmware processing time, thereby preventing printer device failures due to CPU overruns and increasing CPU usage efficiency.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a control circuit for rotating a DC servo motor, Fig. 2 is a schematic structural diagram of a serial dot printer to which the servo motor drive control method for a serial printer of the present invention is applied, and Fig. 3 is a servo motor block diagram. 4 is a state diagram when setting the duty amount in the motor drive circuit, 5 is an edge pulse generation circuit diagram, 6 is a time chart of the edge pulse generation circuit, and 7 is a speed detection circuit diagram. , Fig. 8 is a time chart of the speed detection circuit, Fig. 9 is an interrupt generation circuit diagram, Fig. 10 is a time chart of the interrupt generation circuit diagram, and Fig. 11 is a background processing and I
P? Figure 12 is a flowchart of a program that controls the speed of the carriage, and Figure 13 is a diagram showing the relationship between processes.
P? Flowchart of Processing FIG. 14 is a flowchart of speed control during background processing. l...Microprocessor, 5...Motor drive circuit, 6...Speed detection/interrupt generation circuit, 8...DC servo motor.

Claims (1)

[Claims] In a servo motor drive control method for a serial printer, which controls the drive current supplied to the servo motor to control the rotation speed of the servo motor according to a program, (a) the current rotation speed of the servo motor is set to V; , the control target value of the servo motor is V_1, and the limit value of the rotation speed of the servo motor corresponding to the processing capacity of the control unit is V_
c (V_c<V_1) and the gain of the servo system is G. When V≦V_1, K=(V_1-V)G When V>V_1, K=-(V_1-V)G Based on The drive current value of the servo motor is determined according to the calculated command value K, and this is executed in the background processing. (b) When V≧V_c, the servo motor is driven according to the command value calculated based on K=0 1. A servo motor drive control method for a serial printer, characterized in that the drive current value of the servo motor is determined, and this is executed during interrupt processing using an interrupt signal generated from an encoder attached to the servo motor.