JPH05284768A - Learning servo motor controller - Google Patents

Abstract

PURPOSE:To obtain excellent control characteristics by providing a load- magnitude detecting means outside a servo loop, and calculating appropriate initial values by the result of its detection and converging optimim control parameter values. CONSTITUTION:In the case of a serial printer, the working speed of a controlled system 5 is detected with a speed detecting means 6 such as an encorder etc., and converted into a speed data. Then its speed data is sent to a data keeping means 7 and a speed subtractor 9 and subtracted from a speed directing data, and a speed error Ve is calculated and sent to a PID control means 1. Besides, a load detecting means 10 judges which cartridge of four colors is mounted and which not, and initial values of control parameters are calculated with an initial value calculating means 11 on the basis of this judgment. Then, the initial values are sent to a control parameter calculating means 8, and the values of PID control parameters are calculated on the basis of data from the data keeping means 7 and the initial values from the initial value calculating means 11, and set in the PID control means 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo motor control device having appropriately defined control parameters (described later), which obtains appropriate control parameters for each operation of the motor, and gradually obtains optimum control parameters. The present invention relates to a control device for a learning servo motor that converges on a control parameter, and is most suitable for a control device for a motor used in a printer or a facsimile.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to a motor used in a printer.

In a conventional serial printer, a DC motor and its controller are used as a drive source for scanning a carriage carrying a printing means (for example, dot impact type, ink jet type, thermal transfer type, etc.). When a general serial printer receives print data from an external computer or the like, the motor rotation is started to drive the carriage, and printing is started when a certain speed is reached. When the data for one line is printed, the motor is stopped and the paper for one line is fed. If there is more print data, the above operation is repeated to continue printing. Here, the operation of the carriage drive motor (hereinafter, referred to as a CR motor) will be described in detail.

First, when a print start command is sent from the computer, the printer controller activates the CR motor via the motor control device. For example, as shown in FIG. 7, immediately after startup, the vehicle is gradually accelerated so that noise or vibration does not occur or overcurrent does not flow to the motor. Then, printing is performed by performing constant speed control at a predetermined speed. After printing, it decelerates and stops immediately. I.e. acceleration,
In deceleration, control is performed so that noise or the like does not occur due to rapid speed change, and printing accuracy is not disturbed at constant speed.

Speed control of such a CR motor is generally performed by a servo system having a PID control loop as shown in the block diagram of FIG. 5, and finally the voltage applied to the motor or the duty of PWM is applied. Is done by changing.

Here, description will be made assuming that the PWM duty is controlled to control the motor speed. First, the speed error Ve is calculated by subtracting the moving speed of the controlled object (carriage in this case) or the rotation speed of the motor detected by a speed detection mechanism such as an encoder from the externally instructed speed. Next, for example, the manipulated variable (here, the duty of PWM) is calculated according to the following equation.

PWM = Kp × Ve + Ki × ∫Vedt + Kd × (dVe / dt) where Kp is a proportional control constant Ki is an integral control constant Kd is a differential control constant. The duty of PWM applied to the motor driver is changed according to the calculated value to control the speed of the carriage. These Kp, Ki and Kd are control parameters.

The above description is based on the control parameters Kp, Ki,
Although Kd is fixed, a so-called learning servo system in which it is dynamically changed may be adopted. FIG. 6 is a block diagram of this. This method has a means for holding all or a part of the detected speed data, and calculates and sets more optimal control parameters from these data. In addition, the carriage is reciprocated several times to gradually converge to the optimum value. In this case, good control characteristics are often obtained even with relatively large load fluctuations.

In recent years, microprocessors (hereinafter referred to as MP
(Referred to as U) is remarkably improved in performance, and the above control is performed by digital control using an MPU. In this case, the initial values of the above Kp, Ki, and Kd parameters are stored in the ROM, and the calculated set values are stored in the RAM.

[0010]

Normally, a color printer has heads of four colors of yellow, magenta, cyan, and black, and by mixing these colors on the paper surface, red,
Expresses green and blue colors. Of course, it is also possible to express many colors in a pseudo manner by using an area gradation method such as a dither method. When a carriage is equipped with four-color heads and four-color ink tanks to configure this color printer, (1) ink is consumed and the carriage weight changes as printing is performed.

In the case of a color printer having four color inks, the change is particularly large.

(2) For example, when printing only a single color such as black, it may be possible to remove other heads or ink tanks, and the weight of the carriage is significantly different from the case where four color head tanks are loaded. .. If there is a significant change in the load applied to the motor based on changes in the weight of the control target, such as changes in the weight of the carriage, changes in the number of carriage heads, and ink tanks, schedule the load. Since it is difficult to set the control parameter to an appropriate value, an incorrect initial value may be set.Furthermore, even if the learning servo is performed by reciprocating the carriage, the control parameter calculation is not possible. Even if it diverges or converges, there is a practical problem that it requires a large number of carriage reciprocating operations.

[0013]

According to the present invention, the means for detecting the magnitude of the load is provided outside the servo loop, and an appropriate initial value of the control parameter is calculated from the result of the detection. Since it is possible to set the value, the optimum control parameter value can be promptly converged after the operation is started. for that reason,
Good control characteristics can be obtained.

Further, in the case of a learning servomotor control device for controlling the drive of the print head, generally the carriage of the print scan for scanning the carriage carrying a plurality of print heads, the print head becomes an important factor of the load. Alternatively, it is convenient to detect the number of ink tanks, which is also as simple as possible, so that an appropriate initial value of the control parameter can be calculated.

[0015]

[Embodiment 1] A carriage control of an ink jet type serial color printer will be described below as an example with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention. The operating speed of the controlled object 5 is detected by speed detecting means 6 such as an encoder. For example, when speed detection is performed by an encoder, the intervals between consecutive encoder pulses are counted based on a clock from a clock generator (not shown) as shown in FIG. 8, and the count value and clock frequency are converted into speed data. To do. The speed data is sent to the data means 7 and the speed subtractor 9. The data sent to the speed subtractor 9 is subtracted from the speed instruction data input from the outside, the speed error Ve is calculated, and the PID is calculated.
It is sent to the control means 1. The speed data sent to the data holding means 7 holds a necessary amount of data at a designated timing by a signal given from a data holding timing generating means (not shown). The held data is sent to the control parameter calculation means 8. The load detecting means 10 is composed of, for example, a mechanical switch for detecting the presence or absence of an ink cartridge (print head + ink tank) as shown in FIG. In this example, when the cartridge is mounted, the switch 12 is turned on, and for example, the input port of the one-chip microcomputer detects "L", and if not mounted, detects "H". With this configuration, it can be determined which of the four colors is not loaded. Based on this, the initial value calculation means 11 calculates the initial value of the control parameter. This can also be done by writing the initial value data obtained by experiments in a ROM or the like and referring to it. The obtained initial values of the control parameters are sent to the control parameter calculation means 8. The control parameter calculation means 8 calculates the values of the PID control parameters Kp, Ki, Kd based on the data from the data holding means 7 and the initial value from the initial value calculation means 11 and sets them in the PID control means 1. The PID control means 1 calculates the PWM duty to be applied to the motor driver 3 by the calculation formula PWM = Kp × Ve + Ki × ∫Vedt + Kd × (dVe / dt) as described in the section of the related art. The carriage is driven with the PWM value calculated in this way, and the control parameters are recalculated based on the speed data. By repeating this, the value approaches the optimum value. [Second Embodiment] FIG. 3 is a diagram for explaining a second embodiment of the load detecting means 10 of the present invention. When the head or the ink cartridge 13 is provided with an electric contact for detection as shown in FIG. 3, "L" is detected at the input port if the head or the cartridge 13 is not present, and "H" is detected if there is. This allows the number of mounted cartridges to be determined. Other operations are the same as those in the first embodiment. [Embodiment 3] FIG. 4 is a view for explaining a third embodiment of the load detecting means 10 of the present invention. Among the inkjet printers, a system called thermal inkjet ejects ink by heat generated by energizing a heating element. In this case, a head is often equipped with a temperature detecting element to prevent heating. (Thermistor 16 in Fig. 4)
At this time, the thermistor 16 can be set to a value outside the normal temperature detection range by the A / D conversion means 14 by adjusting the value of the voltage dividing resistance when the head or the ink cartridge is not present. This makes it possible to determine the number of mounted heads or cartridges. Other operations are the same as those in the first embodiment.

[0017]

As described in detail above, according to the present invention, a means for detecting the magnitude of the load is provided outside the servo loop, and an appropriate initial value of the control parameter is calculated from the data, so that the speed can be increased. Can be converged to an optimum value, good control characteristics can be obtained, and the effect is very large.

When the load occupies most of the load can be represented by several kinds of integer values, the initial values of the control parameters can be easily determined if the numbers can be counted by a simple method, which is convenient. Is. In the case of a printing apparatus that scans and prints on a carriage equipped with a print head, the load is usually determined by counting the number of print heads and ink tanks, so the initial value of the control parameter is determined by that number.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating an embodiment of motor control by learning servo of the present invention.

FIG. 2 is a diagram for explaining load detection means according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating load detection means according to a second embodiment of the present invention.

FIG. 4 is a diagram for explaining load detection means according to a third embodiment of the present invention.

FIG. 5 is a block diagram illustrating motor control by conventional PID control.

FIG. 6 is a block diagram illustrating motor control by a conventional learning servo.

FIG. 7 is a diagram illustrating an example of carriage speed control.

FIG. 8 is a diagram illustrating one means of obtaining a velocity signal from an encoder pulse.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 PID control means 2 PWM control means 3 Motor driver 4 Motor 5 Control object 6 Speed detection means 7 Data holding means 8 Proportional control means calculation means 9 Speed subtraction means 10 Load detection means 11 Initial value calculation means 12 Mechanical switch 13 Ink cartridge 14 A / D conversion means 15 CPU 16 thermistor

Claims (2)

[Claims] 1. A means for setting an initial value of a control parameter, further comprising means for detecting an operating speed of a controlled object, and a current control parameter value and a control parameter to be corrected from the detected operating speed value. In the learning servo motor control device having a means for calculating a value and a means for correcting the set value of the control parameter according to the result of the calculation and having a servo loop for converging to the optimum control parameter for each operation, the load of the controlled object A learning servomotor control device, characterized in that it has a means for detecting a value outside the servo loop and sets an initial value of a control parameter according to a result of detection of the load. 2. A learning servomotor control device for controlling driving of a carriage of a printing device for scanning by printing a carriage carrying a print head, the number of print heads or ink tanks mounted on the carriage, or both of them. 2. The learning servomotor control device according to claim 1, wherein the initial value of the control parameter is set according to a result of the detection.