Patent Grant
11279127
The present invention relates to an electric apparatus and a control method therefor, and particularly to, for example, a technique of controlling driving of a moving object such as the carriage of a serial type printing apparatus.
As for driving of a carriage that reciprocally moves by a motor in a serial type printer, feedback control such as PID control using an encoder is common practice. In a serial type inkjet printer, a driving unit that scans a carriage mounted with a printhead for discharging ink emphasizes a velocity vibration at the time of scanning the carriage to stabilize an ink landing position. Thus, it is required to implement control for stabilizing a velocity vibration of the carriage.
In a printing apparatus and a gain correction method described in Japanese Patent Laid-Open No. 2011-102012, a constant (gain) for PID control is corrected in accordance with a correction ratio based on a velocity vibration quantity for a predetermined period during which a specific control target is operated. According to Japanese Patent Laid-Open No. 2011-102012, as the velocity vibration quantity is larger, the correction ratio for PID control can be made smaller. As a result, an excessive vibration is suppressed, thereby making it possible to implement convergence of the velocity vibration of the control target.
In the printing apparatus and the gain correction method described in Japanese Patent Laid-Open No. 2011-102012, to converge the velocity vibration of the control target, the control gain of the control target is decreased resultantly. Therefore, although it is possible to suppress an excessive vibration of a control target, the responsiveness of the control target is spoiled. That is, compatibility between traceability and vibration suppression in a change in state of the control target becomes an issue.
Accordingly, the present invention is conceived as a response to the above-described disadvantages of the conventional art.
For example, an electric apparatus and a control method therefor according to this invention are capable of achieving compatibility between traceability of feedback control and vibration suppression of a control target.
According to one aspect of the present invention, there is provided an electric apparatus for controlling movement of an object, comprising: a detection unit configured to detect the movement of the object; a first estimation unit configured to estimate, based on a detection signal output from the detection unit, a control quantity for performing first feedback control for the object at a first period; a timing signal generation unit configured to generate, based on the detection signal output from the detection unit, a timing signal for estimating a state quantity of the object in order to perform second feedback control for the object at a second period shorter than the first period; a second estimation unit configured to estimate the state quantity based on the timing signal generated by the timing signal generation unit; a first generation unit configured to generate, based on the control quantity estimated by the first estimation unit, a first operation quantity for the first feedback control; a second generation unit configured to generate, based on the state quantity estimated by the second estimation unit, a second operation quantity for the second feedback control; and a synthesizing unit configured to generate an operation quantity of the object from the first operation quantity and the second operation quantity.
According to another aspect of the present invention, there is provided a control method for an electric apparatus for controlling movement of an object, comprising: detecting the movement of the object; estimating, based on a detection signal output in the detecting, a control quantity for performing first feedback control for the object at a first period; generating, based on the detection signal output in the detecting, a timing signal for estimating a state quantity of the object in order to perform second feedback control for the object at a second period shorter than the first period; estimating the state quantity based on the generated timing signal; generating, based on the estimated control quantity, a first operation quantity for the first feedback control; generating, based on the estimated state quantity, a second operation quantity for the second feedback control; and generating an operation quantity of the object from the first operation quantity and the second operation quantity.
The invention is particularly advantageous since it is possible to achieve compatibility between traceability of feedback control and vibration suppression of a control target.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Exemplary embodiments of the present invention will now be described in detail in accordance with the accompanying drawings. It should be noted that the following embodiments are not intended to limit the scope of the appended claims. A plurality of features are described in the embodiments. Not all the plurality of features are necessarily essential to the present invention, and the plurality of features may arbitrarily be combined. In addition, the same reference numerals denote the same or similar parts throughout the accompanying drawings, and a repetitive description will be omitted.
In the following description, control of driving of a motor that moves a carriage of a serial type printing apparatus as an exemplary example of an electric apparatus will be exemplified. However, the present invention is not limited to the carriage of the printing apparatus, and motor control according to the present invention is applicable to any unit that moves an object by driving a motor. For example, in the printing apparatus, motor control is applicable to control of driving of a conveyance motor used to convey a print medium such as a print sheet. The present invention also includes a scanner apparatus that optically reads an image of an original while moving a CCD line scanner or CIS by driving a motor.
1. Explanation of Feedback Control
First, the general feedback control arrangement will be described with reference to
As shown in
To stably operate the control target, it is necessary to set various parameters while ensuring an allowance in terms of control in consideration of the characteristic of the control target. If the allowance is insufficient, a vibration occurs, and an oscillation phenomenon may lead to an uncontrollable state. On the other hand, if the allowance is too large, the traceability performance of the control target deteriorates but it is unavoidable to impose a restriction on the traceability performance for vibration suppression.
Next, the feedback control arrangement used in this embodiment will be described with reference to
As shown in
On the other hand, the detection signal that detects the state of the control target 21 is also input to a calculation timing generation unit 50 for generating a calculation timing to calculate the second operation quantity. Here, the calculation timing according to the state of the control target 21 is generated, and a state quantity estimation unit 25 estimates the first and second state quantities in accordance with the calculation timing.
The second state quantity is obtained by the time differentiation of the first state quantity. More specifically, the first and second state quantities are values formed from a combination of a position and a velocity or a combination of a velocity and an acceleration. These values are output to a second control unit 24. The second control unit 24 calculates the second operation quantity. Next, the second control unit 24 outputs the second operation quantity, and the synthesizing unit 26 synthesizes the first and second operation quantities, and outputs a synthesizing result to the control target 21. The second feedback loop “control target 21→calculation timing generation unit 50→state quantity estimation unit 25→second control unit 24→synthesizing unit 26→control target 21” is thus formed.
Since the first and second state quantities have the relationship between, for example, the position (x) and velocity (v) of the carriage or between the velocity (v) and acceleration (a) of the carriage, the relationship between the two state quantities (two variables) can be represented by a two-dimensional space.
As shown in
As shown in
The first and second operation quantities are updated asynchronously. The synthesizing unit 26 adds the quantities while adjusting the update timings, and outputs an added value as the third operation quantity to the control target 21.
Next, an example in which the feedback control shown in
2. Explanation of Application Example of Feedback Control
A serial type printing apparatus to which control of forming the two feedback loops explained with reference to
<Explanation of Printing Apparatus (
A carriage (moving object) 3 mounted with a printhead 2 is supported slidably by a guide shaft 4, and reciprocally moves above a print medium (sheet) 1. A carriage motor (DC motor) 5 with a pulley is arranged at one end of the moving range of the carriage 3, an idle pulley 6 is arranged at the other end, and a timing belt 7 is looped between the carriage motor 5 and the idle pulley 6, thereby connecting the carriage 3 to the timing belt 7.
To prevent the carriage 3 from rotating about the guide shaft 4, a support member 8 installed to extend in parallel to the guide shaft 4 is installed, and the carriage 3 is also supported slidably by the support member 8. In the printhead 2, a number of print elements are provided and an FFC (Flexible Flat Cable) 11 for supplying the driving signals of the print elements from the main body portion of the printing apparatus to the printhead 2 is arranged. The FFC 11 has a long thin film shape, a conductive pattern for transmitting a driving signal is formed in the inside or surface of the FFC 11, and the FFC 11 has flexibility so that it bends along with the movement of the carriage 3 to move the central position of bending.
Furthermore, an ink tank (not shown) is arranged outside the carriage 3, and a tube 12 that supplies, to the printhead 2, ink contained in the ink tank is provided. The tube 12 has flexibility so that it bends along with the movement of the carriage 3 to move the central position of bending. A connecting member 10 formed from the FFC 11 and the tube 12 is connected between the carriage 3 and a fixing portion 9 of the main body of the printing apparatus.
Furthermore, a linear scale 16 that is used to acquire the position information of the carriage 3 is arranged in parallel to the moving direction (main scanning direction) of the carriage, and is configured to be read by an encoder sensor 15 attached to the carriage 3. Ink collection ports 14a and 14b for collecting ink preliminarily discharged by the printhead 2 are provided on both the outsides in the width direction of the print medium 1. The preliminary discharge indicates an operation for discharging, at positions irrelevant to printing, ink adhered to the distal end portions of nozzles immediately before the start of printing or during execution of printing.
With this arrangement, the carriage 3 reciprocally moves in a direction (main scanning direction) of an arrow A. The print medium 1 is conveyed by a conveyance motor (not shown) in a direction (sub-scanning direction) of an arrow B vertically intersecting the moving direction of the carriage 3.
As shown in
The ASIC 603 generates control signals for controlling the carriage motor 5, a conveyance motor 20, and the printhead 2. The RAM 604 is used as a loading area of image data, a work area for executing a program, and the like. The system bus 605 interconnects the MPU 601, the ASIC 603, and the RAM 604 to exchange data. The A/D converter 606 receives an analog signal from a sensor group (to be described below), performs A/D conversion, and supplies a digital signal to the MPU 601.
Referring to
Furthermore, a switch group 620 is formed from a power switch 621, a print switch 622 used to issue a print start instruction or the like, a recovery switch 623, and the like.
A sensor group 630 is formed from the encoder sensor 15, a temperature sensor 632, and the like which are used for detecting an apparatus status.
A carriage motor driver 640 drives the carriage motor 5 for causing the carriage 3 to reciprocally scan in the direction of the arrow A, and a conveyance motor driver 642 drives the conveyance motor 20 for conveying a print medium P.
At the time of print scanning by the printhead, the ASIC 603 transfers data for driving the print elements (heaters for discharge) to the printhead while directly accessing the memory area of the RAM 604. In addition, this printing apparatus includes, as a user interface, an operation panel 18 formed by an LCD or LED. From the viewpoint of apparatus implementation, the switch group 620 may be included in the operation panel 18.
The ASIC 603 operates as a calculation processing unit to perform image processing and actuator control, and executes calculation processing by receiving a command from the MPU 601. Feedback control calculation is partially executed by the ASIC 603, and details thereof will be described later. The MPU 601 is responsible for part of calculation for feedback control of the carriage 3, and executes driving calculation of the carriage motor 5 in accordance with a print sequence. When the host apparatus 610 issues a print command via the interface 611, the carriage 3 reciprocally moves for a print operation.
3. Details of Feedback Control Arrangement for Carriage Control of Printing Apparatus
Application of the feedback control arrangement described with reference to
Accuracy for causing ink to land at a correct position is required for carriage control of the printing apparatus in order to ensure the print quality by the printhead 2. An ink droplet discharge timing from the printhead 2 is calculated from the moving velocity (v) of the carriage 3, and it is important to minimize a velocity vibration. To achieve this, a vibration target to be suppressed in the feedback control according to this embodiment is the velocity of the carriage. Therefore, the first and second state quantities in the feedback control described with reference to
Furthermore, the control target in the feedback control is the carriage 3, and the encoder sensor 15 outputs encoder signals to the control quantity estimation unit 23 and the state quantity estimation unit 25. In general, two A- and B-phase pulse signals whose phases are different from each other by 90° are used as encoder signals. In this embodiment as well, two A- and B-phase pulse signals are used as the encoder signals.
The control quantity estimation unit 23 estimates position information by counting the pulse signal, and estimates velocity information by measuring the pulse width of the pulse signal. This position/velocity information or the like is output as a control quantity to a PID control calculation unit 36 corresponding to the first control unit 22.
A target value calculation unit 35 generates a target profile for moving the carriage 3 to a target position in accordance with a desired acceleration condition and velocity condition, and outputs the target profile as a target value. The PID control calculation unit 36 performs PID control calculation using the target value from the target value calculation unit 35 and the control quantity from the control quantity estimation unit 23, and outputs a calculation result as the first operation quantity.
The encoder signal from the encoder sensor 15 is also output to the calculation timing generation unit 50, and a timing signal generated by the calculation timing generation unit 50 is output to the state quantity estimation unit 25. The state quantity estimation unit 25 includes a velocity/acceleration information generation unit, and velocity/acceleration information according to the calculation timing is generated. The state quantity estimation unit 25 also receives a register setting value output from a preprocessing calculation unit 38. The register setting value is a value obtained by replacing, by the preprocessing calculation unit 38, the target value from the target value calculation unit 35 by a value in a unit system used in the state quantity estimation unit. The state quantity estimation unit 25 estimates velocity information and acceleration information from the encoder signal, and calculates an error quantity with respect to the register setting value as an operation target. A velocity error quantity and acceleration error quantity as the error quantity are output, as a combination of state quantities in the velocity dimension and acceleration dimension, to a sliding mode control calculation unit 39 corresponding to the second control unit 24.
The sliding mode control calculation unit 39 forms a two-dimensional plane space formed from two variables of the velocity error quantity and the acceleration error quantity. Region determination of the two-dimensional plane described with reference to
phase switchover line (S)=switchover coefficient×acceleration error quantity+velocity error quantity
For example, if S>0, the current state quantity is located in region 1 as the upper portion with respect to the switchover line. On the other hand, if S<0, the current state quantity is located in region 2 as the lower portion with respect to the switchover line. If S=0, S=0 is defined as S>0 or S<0. The sign of the operation quantity is decided based on the region determination result, and the operation quantity is output as the second operation quantity. Note that the switchover coefficient is updated by the register setting value output from the preprocessing calculation unit 38. As a special case, the phase switchover line may not use both the acceleration error quantity and the velocity error quantity but use only one of them.
The update timings of the first and second operation quantities will now be described.
The first operation quantity is updated every time control calculation by the PID control calculation unit 36 is executed. The carriage motor driving control unit (carriage motor driver) of the printing apparatus to which the feedback control shown in
To implement high-speed calculation derived from a change in pulse of the encoder signal, it is assumed that control calculation by the sliding mode control calculation unit 39 is executed by hardware such as an ASIC.
Referring to
The reason why the MPU 601 and the ASIC 603 share the feedback control is that the update period of the information processed in the portion implemented by the ASIC (hardware) 603 is shorter than that of the information processed in the portion implemented by the MPU 601.
The calculation by the preprocessing calculation unit 38 is also executed every time the target value calculation unit 35 updates the target value, and the latest register setting value is set in the register area of the ASIC 603. The preprocessing calculation unit 38 performs calculation for managing, as parameter values, only during the calculation period of the PID control calculation unit 36, some of variable values that change moment by moment in calculation of the phase switchover line executed by the sliding mode control calculation unit 39 or estimation calculation of the state quantity estimation unit 25. Execution of all the feedback control by the ASIC leads to upsizing of the integrated circuit, and flexibility and versatility of processing lack. Thus, in this embodiment, the calculation accuracy and the circuit scale are compromised, and the preprocessing calculation unit 38 of the MPU executes part of calculation at the update timing.
A control parameter to be used by the sliding mode control calculation unit 39 may be changed in accordance with the operation state of the carriage 3. In this case, based on the target value of the target value calculation unit 35, a section of one of an acceleration state, a constant velocity state, and a deceleration state, in which the carriage 3 is located is determined. By changing, for each section, the switchover coefficient to be used to calculate the phase switchover line, an appropriate switchover line according to a carriage operation condition may be selected to implement rapid convergence.
4. Explanation of Timing Signal Generated by Calculation Timing Generation Unit 50
In
The time area shown in
As shown in
The higher the sampling frequency, the higher the resolution of the counter, and the less the influence of the quantization error, so that the more accurate counting result can be obtained. However, the higher frequency of the device leads to disadvantages such as increased power consumption. Therefore, it is realistic to design the device to operate at an appropriate frequency in recognition that the quantization error is included to some extent.
In the velocity profile shown in each of
According to
Such control is repeated until the control target reaches the calculation thinning end position. More specifically, this control is performed until the movement of the carriage 3 shifts from the constant velocity area to the deceleration area. Here, the state quantity estimation unit 25 holds the sum of the velocity/acceleration information obtained at the A-phase leading edge detection timing immediately before the preceding detection timing and the current velocity/acceleration information. Therefore, the sliding mode control calculation unit 39 executes calculation corresponding to it.
Note that the example shown in
As described above, the calculation timing thinning processing is performed when the velocity of the control target has reached the maximum velocity and enters the constant velocity area on the velocity profile. At this time, in consideration of the influence of the quantization error, the timing of performing the calculation processing of the second feedback loop is desirably acquired from one phase and one edge (for example, the A-phase and the leading edge) of the information obtained from the encoder sensor. In this case, when the calculation timing thinning processing is performed, the influence of the quantization error can be reduced, but the update cycle of the velocity/acceleration information is increased. This leads to a disadvantage that the feedback control traceability deteriorates. To solve this problem, in this embodiment, the calculation timing generation unit 50 uses the information of the encoder signals of both phases, and generates the calculation timing signal such that the update cycle of the velocity/acceleration information is not increased and the feedback control traceability does not deteriorate even if the thinning processing is performed.
According to
However, as shown in
Therefore, according to the embodiment described above, by applying the feedback control arrangement formed from the first and second control units to the carriage driving control of the printing apparatus, it becomes possible to suppress the velocity vibration which cannot be suppressed conventionally. In addition, in the parameter setting of the first control unit, the area for coping with the variation factor of the control target can be reduced, so that deterioration of the feedback control traceability can be minimized. Thus, according to this embodiment, compatibility between vibration suppression and traceability of the carriage as the control target of the feedback control can be achieved, so that it is possible to perform carriage driving control more accurately, thereby implementing high-quality image printing.
In addition, according to the embodiment described above, the velocity information is acquired from the B-phase encoder signal, so that the velocity information of the carriage is updated while the generation operation of the calculation timing signal is thinned out based on the A-phase leading edge. Therefore, the velocity information update frequency is maintained even if the calculation processing is thinned out, so that it is possible to prevent deterioration of the feedback control traceability. Note that when both the A-phase and B-phase are used, the intervals of the update timings become unequal. Accordingly, this may be advantageous with respect to noise of a particular frequency.
Note that
Regarding the timing of performing the calculation thinning, the present invention is not limited to the examples described above. For example, the calculation thinning may be performed over a plurality of detection timings of the encoder signal edges. In this case, the velocity information update timing based on the encoder signal of the phase, which is not used for the calculation timing thinning, may be arbitrarily set.
5. Explanation of Another Application Example of Feedback Control
The present invention is applicable to any control of moving an object by driving the motor, as described above. Therefore, the present invention is applicable to, for example, control of the scanner motor that moves the CCD sensor or the CIS of the scanner apparatus having a single function or the scanner unit of a multi-function printer (MFP).
To ensure the image reading performance, the scanner unit needs to acquire an image signal by matching the movement quantity of the scanner unit and the light source lighting timing of the CCD sensor or the CIS. Since the light source lighting timing generally assumes that the moving velocity of the scanner unit is constant, it is important to suppress the velocity vibration of the scanner unit. Therefore, since the vibration target to be suppressed is the moving velocity of the scanner unit, the combination of the state quantities of the velocity and the acceleration is applied to the above-described second control unit. Basically, control is performed with the same arrangement as the carriage control arrangement described with reference to
This can suppress a micro-vibration at a high-frequency of the scanner unit, which cannot be suppressed by only the conventional control, and improve the feedback control traceability. As a result, high-quality image reading can be achieved.
The present invention is also applicable to conveyance roller driving control of the printing apparatus described with reference to
This can implement more accurate conveyance control.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2019-169579, filed Sep. 18, 2019, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2019-169579 | Sep 2019 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 10913273 | Orihara | Feb 2021 | B2 |
| 20190335055 | Suzuki et al. | Oct 2019 | A1 |
| Number | Date | Country |
|---|---|---|
| 2011-102012 | May 2011 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20210078321 A1 | Mar 2021 | US |
