JPS6118432B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printer that has a carriage mounted with a print head and that moves in the width direction of paper to perform printing, and particularly relates to a printer that has a carriage that carries a print head and prints by moving in the width direction of paper. Regarding a control device.

The use of this type of servo control system to control the moving speed of a carriage on which a print head is mounted in the paper width direction is known from Japanese Patent Laid-Open No. 52-13730 (Japanese Patent Publication No. 58-53374).

Conventionally, in this type of speed control device, the speed profile is set by a fixed reference signal, that is, a reference signal assuming constant acceleration, so that the speed profile is not affected by the output fluctuation of the speed signal, the motor torque constant, If the effective acceleration for driving the motor fluctuates due to variations in drive current, load, etc., there is a drawback that the rotational speed of the motor becomes unstable in following the set speed profile. Furthermore, in a similar conventional example in which the speed signal is generated by interval differentiation of a periodic position signal, when the position signal fluctuates due to electrical and mechanical fluctuations of the transducer and sense amplifier, the fluctuation is This directly becomes an error in the speed signal, causing the print head moving speed to fluctuate unstably and similarly impairing the ability to follow the speed profile.

The present invention eliminates the above-mentioned drawbacks and provides a print head speed control device for a print printer that can maintain good followability to the speed profile even when the signal level of each part, motor constant, load, etc. change. It is on offer.

According to the present invention, in a printer for printing on a recording medium, means for generating a speed signal proportional to the displacement speed of a print head when moving from one print position to a new print position; means for differentiating and generating an acceleration signal; means for deriving a value proportional to the peak value of the acceleration signal from the acceleration signal as a reference signal; and feeding back this reference signal to a speed profile and comparing it with the speed signal to detect an error. A speed control device is provided comprising means for generating a signal and a servo motor for driving a printhead in response to the error signal.

Next, in order to facilitate comparison with the present invention, a conventional example will be described with reference to FIGS. 1 and 2. Figure 1 is a block diagram showing a servo system in which a tachometer generator detects the speed signal of a carriage that carries a print head and performs printing by reciprocating in the width direction of the printing paper. 2 is a position transducer for converting the print head position information, that is, the position information of the carriage in the printing paper width direction into an electrical position signal; 2 is a sense amplifier for amplifying the output of transducer 1; 3 is a tachometer generator, and 6 is a D/A converter that weights the digital speed profile information from the microprocessor applied through terminal 4 with the reference signal F led from terminal 5 and converts it into an analog speed profile signal. , 7, and 8 are control mode changeover switches; when the servo system is placed in the speed mode, 7 is on and 8 is off; when the servo system is placed in the position mode, 7 is off and 8 is on. 9 is a summing circuit that compares the speed profile signal with the speed signal from the tacho generator 3 and outputs an error signal; 10 is a summing circuit that amplifies the error signal and connects the servo motor 1;
1 is a driving amplifier circuit that drives the motor 1 with a constant current, that is, with constant acceleration at maximum acceleration/deceleration. The tachogenerator 3 and the transducer 1 are JP-A-52-
A servo motor 1 that drives a carriage that is equipped with a print head and is movable in the width direction of printing paper using the mechanism shown in Publication No. 72622.
1 and when the servo system is placed in speed mode, the analog speed profile signal from the D/A converter 6 is compared with the speed signal from the tachometer generator 3 in a summing circuit 9.
Extract the error signal and use it to control the servo motor 1.
1, the print position is controlled. The servo motor 11 controls the horizontal feeding of the print head, and a wire rope, belt, etc. is interposed between a pulley directly connected to the rotating shaft of the servo motor 11, and the wire rope, belt, etc. A fixed print head is moved laterally by rotation of a servo motor 11. Thereby, positioning control of the print position in the lateral direction can be performed.

The conventional example shown in the block diagram of Fig. 2 also uses the same servo system, but uses a sense amplifier 2' that generates two-phase periodic position signals as a sense amplifier, and uses these two position signals as a sense amplifier. This differs from the conventional example shown in Fig. 1 in that, in addition to the speed generation circuit 12, the speed signal is obtained by differentiating the linear portion of each position signal and then combining the outputs of the sections. However, other parts have the same functions. In this conventional example, the two-phase position signals output from the transducer 1 and the sense amplifier 2' are sent to the speed signal generating circuit 1.
However, if the amplitude of the position signal changes due to mechanical or electrical fluctuations of the transducer 1, the speed signal will also change accordingly.

In the conventional examples shown in FIGS. 1 and 2, the speed signal obtained from the tachogenerator 3 directly connected to the rotating shaft of the servo motor 11 or the speed signal obtained from the transducer 1 and the speed generation circuit 12 is Therefore, the reference signal of the D/A converter that outputs the speed profile signal is at the same level regardless of variations in the rotational torque of the servo motor 11, load fluctuations, etc.

Figure 3A shows the state of transition in the control process between the analog stepwise speed profile signal and the speed signal in the two conventional devices described above, with time on the horizontal axis and speed and acceleration on the vertical axis. They are shown below. In this figure, G-
1, C-1 and D-1 show the changes in the speed profile signal, speed signal and acceleration, respectively, and C-2 and D-2 show the changes in speed and acceleration when the slope of the speed becomes gentler. It shows the condition. The slope in acceleration and deceleration of velocity signal C-1 is proportional to the magnitude of the print head acceleration and the amplitude of the position signal. In conventional examples that operate in this way, even if the motor is driven with a constant current by replacing the motor, if the generated acceleration decreases, the slope of the speed signal decreases from C-1 to C-2. It has a defect in that it loses its ability to follow the stepwise changes in the speed profile signal G-1 (seen in 101 to 103) and ends up overshooting the desired target stop position.

FIG. 4 is a block diagram showing an embodiment of the speed control device according to the present invention.
13 is a differentiation circuit that differentiates the speed signal from the speed generation circuit 12 to generate an acceleration signal; 14 is a sample hold that holds the peak value of the acceleration signal output from the differentiation circuit 13 and outputs a reference signal F'. The reference signal F' is applied to the D/A converter 6 to weight input speed profile information. Other elements are
As shown by the same symbols as in the conventional example of FIG. 2, they have the same functions. According to this embodiment, a certain reference signal at the desired acceleration
If the constants of the differentiating circuit 13 and the sample and hold circuit 14 are set so as to output F', the decrease in the slope of the speed signal C will result in the peak value of the acceleration signal D, which is its time derivative, that is, the reference signal F' also decreases proportionally to the desired value by the rate at which the acceleration is reduced. For example, as shown in Figure 3B, the speed profile signal G weighted by the reference signal F'
As seen in C-2, the entire speed profile signal becomes smaller in proportion to the desired function, and as a result, the speed signal C-2 can be tracked with sufficient stability, making it easy to move to the desired stopping position. becomes.

Furthermore, when the amplitudes of the two-phase position signals A and B change due to mechanical and electrical fluctuations of the transducer 1, the speed signal C, which is the differential output of the position signal, changes.
The output changes by the rate at which the amplitude changes. For this reason, conventionally, if the amplitudes of the position signals A and B fluctuate in the direction of decreasing, the speed signal C also decreases in proportion to this change, and the speed signal C is set to a fixed speed profile signal G as a speed tracking target. In the process of C following this, the actual speed of the print head became faster than the desired speed by the percentage that the amplitudes of the position signals A and B decreased, and it finally became impossible to follow when decelerating. . However, according to this embodiment, even if the speed signal C decreases, its slope also decreases in proportion to the decrease, so that the peak value of the acceleration signal D, that is, the reference signal F', also decreases by the same decrease. , and the entire speed profile signal G also becomes proportionally smaller, so there is no relative change between the speed signal C and the speed profile signal G. Therefore,
The desired speed is stably controlled without causing any fluctuation in the actual speed of the print head.

It should be noted that while the reference signal of the D/A converter obtained by the conventional examples shown in FIGS. In the embodiment, since the reference signal of the D/A converter feeds back the acceleration signal obtained by differentiating the actual speed signal of the servo motor 11, variations in the rotational torque of the servo motor 11,
By performing speed control by changing the level of the speed profile signal according to the actual capacity of the servo motor 11 in response to load fluctuations, etc., it is possible to stably perform start-up and stop control to the target stop position.

Furthermore, according to the above embodiment, changes in the speed signal due to mechanical and electrical fluctuations of the transducer 1 can also be fed back to the reference signal of the D/A converter 6, so that the actual displacement of the print head can be Speed control is possible at the level of the speed profile signal corresponding to the speed. As a result, the acceleration signal having the amplitude component of the position signal is fed back to the reference signal of the D/A converter, making it possible to stably control the print head to the target stop position as described above.

As explained above, according to the speed control device of the present invention, by feeding back the acceleration signal to the speed profile signal, instability in tracking a desired speed trajectory caused by fluctuations in actual acceleration or fluctuations in the position signal can be reduced. The effect obtained is significant in that the speed control can be stabilized by eliminating the problem.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one example of the conventional servo system, Fig. 2 is a block diagram showing another example of the conventional servo system, and Fig. 3 A and B show control states of the conventional example and the present invention, respectively. Figure 4 explaining the comparison of
The figure is a block diagram showing one embodiment of the present invention. In the figure, 1 is a position transducer;
2' is a sense amplifier, 6 is a D/A converter, 9
10 is a summing circuit, 10 is a motor drive circuit, 11 is a servo motor, 12 is a speed generation circuit, 13 is a differentiation circuit, and 14 is a sample/hold circuit.

Claims (1)

[Claims] 1. In a printer equipped with a print head that prints on a recording medium and having a carriage that moves in the row direction of the recording medium, the movement of the print head in the row direction when moving from one print position to a new print position. means for generating a velocity signal proportional to the displacement velocity; means for generating an acceleration signal by differentiating the displacement velocity signal; and means for deriving a value proportional to the peak value of the acceleration signal from the acceleration signal as a reference signal. , comprising means for feeding back the reference signal to a speed profile and comparing it with the speed signal to generate an error signal; and a servo motor for driving the print head in the row direction in response to the subsequent error signal. A speed control device featuring: