JP2006252081A - Belt-positioning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt-positioning device that can stop at accurate target position, in a short time. <P>SOLUTION: An integral value is calculated, and the accuracy of control is improved by the active use of the integral value. A code S in Figure, showing an example of an FB controller of a continuous system, is a Laplacian operator, and codes TI11, TI12, T11, T12 are the constants of the controller. Because performing calculation by a microcomputer in actuality, the controller becomes a discrete system controller. For example, a block diagram of the continuous system is deformed to take out an integration term, and is made to be a discrete system. The difference e, between a target position instruction and a control target position, is inputted to the FB controller and is calculated, so that a control amount Ical2 is found. By having a Reset signal enter an integrator, integration amount is adjusted. Although a belt overreaches a stop position or stops before the stop position, when a value of the integration amount is different from a value required in time of the stop, stop control is more accurately executed by adjusting the integration amount. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a belt positioning apparatus, for example, a belt positioning apparatus that can stop at a target position accurately in a shorter time.

  Conventionally, a belt positioning apparatus is generally applied and used in many apparatuses such as a copying machine, a facsimile apparatus, and a printer apparatus.

Specifically, the position control is performed with high accuracy by using a belt positioning device such as a copying machine or a printer (see Patent Document 1 and Patent Document 2). More specifically, an attempt is made to easily obtain the transfer function of the state from the axis of the rotary drive source to the surface of the rotating body (Patent Document 1). In addition, it is intended to obtain a control device that can be controlled at high speed and with high accuracy without being affected by disturbance such as lost motion that occurs when the rotation of the motor is transmitted to the partially mounted head by the belt (Patent Document). 2).
JP 2001-306149 A Japanese Patent Laid-Open No. 11-272335

However, in the case of the prior art, there is a limit in achieving image formation with higher accuracy and higher definition. Therefore, the appearance of a belt positioning device with higher accuracy is desired.
An object of the present invention is to provide a belt positioning device that enables belt position control with high accuracy.

  The first object of the present invention is to adjust the integration amount of the integrator in response to the problem that the belt does not stop at the stop position in a short time due to the influence of the integrator of the feedback controller when the belt is stopped following the target position. By this, it is providing the belt positioning device which can stop at a target position correctly in a short time.

  The second object of the invention is to stop at the target position accurately in a short time, since the error can be absorbed in the constant speed section even if there is a follow-up error when the belt is started, so that the acceleration is increased, and the follow-up error is generated when decelerating and stopping. If there is, there will be a situation where it is impossible to stop at the target position accurately. For this phenomenon, it is to provide a belt positioning device that can stop at a target position accurately in a short time by decelerating over time.

  The third object of the present invention is to cancel the calculation delay due to feedback and to follow the target position during acceleration / deceleration because the feedforward calculation unit is present, and to accurately stop at the target position by the feedback calculation unit. A belt positioning device is provided.

  The fourth object of the invention is that the acceleration and speed at start-up are “0”, the acceleration when reaching constant speed is “0”, the acceleration at the start of deceleration is “0”, and the acceleration at stop is Since the speed is “0”, it is a smooth trajectory and does not vibrate. Accordingly, it is an object of the present invention to provide a belt positioning device that can accurately stop at a target position in a short time by making a curve of an acceleration / deceleration profile that can accurately follow the target position.

  The fifth object of the invention is to make the target position trajectory and the position of the belt positioning device coincide with each other only by the feedforward calculation unit. Accordingly, it is an object of the present invention to provide a belt positioning device that can ignore the delay of the feedback system and can accurately stop at the target position.

  The sixth object of the present invention is to reduce the steady-state deviation by making the low band of the open loop transfer function have an inclination of at least −60 DB / DEC. For this reason, it is providing the belt positioning device which can stop to a target position correctly.

  The seventh object of the present invention is to use the current corresponding to the friction force of the belt positioning device as the feedforward value, thereby eliminating the influence of the friction force and determining the feedforward value by the speed value in the vicinity of the belt stop position. Therefore, the present invention provides a belt positioning device that can accurately stop at a target position.

  An eighth object of the present invention is to provide a belt positioning apparatus that can eliminate a delay in calculation by tabulating the feedforward value, and can thereby accurately stop at the target position.

  The ninth object of the invention is to use a belt marker signal having a low position detection resolution and a rotary encoder angle signal having a high position detection resolution as a belt position signal. Therefore, a high resolution belt position signal can be obtained and the belt position can be directly set. It is an object of the present invention to provide a belt positioning device that can measure and accurately stop at a target position.

  A tenth object of the present invention is to provide an ink jet image forming apparatus capable of obtaining a belt moving device capable of stopping at a target position with high accuracy and at high speed when the ink jet image forming apparatus is used in a paper conveying belt device, and suppressing color misregistration. It is to be.

  The invention according to claim 1 is a belt positioning apparatus comprising a belt, a roller for moving / stopping the belt, a motor for rotating the roller, and a position detecting means for detecting the position of the belt. Means for adjusting an integral amount of a detection value from the position detection means when a predetermined point approaches a stop position as a target position, and calculating the integral value based on the calculated integral value; And position control means for executing position control for stopping at the target position.

  According to a second aspect of the present invention, in the first aspect of the present invention, the target position is a position obtained by changing a trajectory when the belt is started and when the belt is decelerated and stopped.

  According to a third aspect of the present invention, in the first aspect of the invention, the position control means includes a feedback calculation unit that calculates a feedback value corresponding to the calculation of the target position, and a feedforward calculation unit that calculates a feedforward value. It is characterized by the following.

The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the transfer function for creating the target position is:
Refc (s) = 1 / (da3 * dsigma ³・ s ³ + da2 * dsigma ²・ s ² + da1 * dsigma ・ s + 1)
When
At startup and constant speed, Refst (s) = Refc (s) / s ² ,
During deceleration stop, Refsp (s) = Refc (s) / s,
It is characterized by being.

  According to a fifth aspect of the present invention, in the invention according to the third or fourth aspect, the feedforward calculation unit is configured such that “Refc (s)” as a part of a transfer function for calculating the target position is the belt positioning device. It is a reciprocal of the transfer function P (s).

  The invention according to claim 6 is the invention according to claim 3, characterized in that the low-frequency range of the open loop transfer function has a slope of at least −60 DB / DEC.

  The invention according to claim 7 is characterized in that, in the invention according to claim 1, the feedforward value is changed by the value of the frictional force obtained from the speed near the stop position of the belt and the current value at constant speed. To do.

  The invention according to claim 8 is the invention according to claim 7, characterized in that the feedforward value is tabulated.

  According to a ninth aspect of the invention, in the first aspect of the invention, the belt position is detected by a detection sensor A that reads a marker provided on the surface of the belt and a rotary attached to a shaft that drives the belt. The position of the belt is detected by position detection means comprising a detection sensor B for detecting the angle of a rotary encoder attached to the encoder or the motor shaft.

  According to a tenth aspect of the present invention, in the invention according to any one of the first to ninth aspects, the belt moving device is a paper conveying belt, and is used in an ink jet image forming apparatus.

  According to the belt positioning device of the first aspect of the invention, when the belt is stopped following the target position, the integration amount of the integrator is adjusted when the belt does not stop at the stop position due to the influence of the integrator of the feedback controller. By doing so, it is possible to stop at the target position accurately in a short time.

  According to the belt positioning apparatus of the second aspect of the present invention, in order to stop at the target position accurately in a short time, when the belt is started, the error can be absorbed in the constant speed section even if there is a tracking error, so that the acceleration is increased. However, when there is a follow-up error at the time of deceleration stop, it becomes impossible to stop at the target position accurately. Therefore, it is possible to stop at the target position accurately in a short time by decelerating over time.

  According to the belt positioning apparatus of the third aspect of the invention, since there is a feed-forward calculation unit at the time of acceleration / deceleration, the calculation delay due to feedback can be canceled and the target position can be followed quickly, and the feedback calculation unit This makes it possible to stop at the target position accurately.

  According to the belt positioning device of the fourth aspect of the invention, the acceleration and speed at start-up are “0”, the acceleration when reaching the constant speed is “0”, and the acceleration at the start of deceleration is “0”. The acceleration and speed at the time of stop become “0”. For this reason, by making the profile a curve, it is possible to follow a smooth acceleration / deceleration locus without vibration and to stop at the target position accurately in a short time.

  According to the belt positioning device of the fifth aspect of the invention, the target position trajectory and the position detection of the belt positioning device are calculated only by the feedforward calculation unit, so that the delay of the feedback system can be ignored. As a result, it is possible to accurately stop at the target position.

  According to the belt positioning device of the sixth aspect, the low band of the open loop transfer function has an inclination of at least −60 DB / DEC. As a result, the steady-state deviation can be reduced, so that it is possible to accurately stop at the target position.

  In the invention according to claim 7, the current corresponding to the frictional force of the belt positioning device is used as the feedforward value. As a result, the influence of the frictional force is eliminated, and the feedforward value is determined based on the speed value in the vicinity of the belt stop position, so that the target position can be accurately stopped.

  According to the belt positioning apparatus of the eighth aspect of the invention, the calculation delay can be eliminated by making the feedforward value into a table. As a result, it is possible to accurately stop at the target position.

  According to the belt positioning apparatus of the ninth aspect, the belt marker signal having a low position detection resolution and the angle signal of the rotary encoder having a high position detection resolution are used as the belt position signal. As a result, a high-resolution belt position signal can be obtained and the belt position can be directly measured, so that it is possible to accurately stop at the target position.

  According to the belt positioning apparatus of the tenth aspect of the present invention, when used in the paper conveying belt apparatus of the ink jet image forming apparatus, it is configured as a belt moving apparatus capable of stopping at the target position with high accuracy and at high speed. For this reason, the inkjet image forming apparatus which suppressed color shift can be provided.

  Next, an embodiment of a belt positioning device according to the present invention will be described in detail with reference to the accompanying drawings. Referring to FIGS. 1-12, an embodiment of the belt positioning device of the present invention is shown.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The FB controller will be described with reference to FIGS. FIG. 1 shows a continuous FB controller. Symbol S is a Laplace operator, and TI11, TI12, T11, and T12 are controller constants. Actually, since the operation is performed by a microcomputer, the discrete value system controller shown in FIG. 2 is obtained. In FIG. 2, the block diagram of the continuous diameter is modified to extract the integral term, and then the discrete value system is obtained. The part indicated by the symbol “T / Z-1” is a discrete value system integrator. Symbol T is a sampling time. In the block diagram of FIG. 3, the reset (Reset) code indicates that the current position of the belt (In1 in the figure) is compared with the vicinity of the stop position (Constant 4). Refflg).

  A difference e between the target position command and the position to be controlled enters the FB controller and is calculated to obtain a control amount Ical2. The integration amount is adjusted by the reset signal (Reset) entering the integrator. If the value of the integration amount is different from the value required at the time of stopping, the belt will go past the stop position or stop in front, but it can be stopped accurately by adjusting the integration amount.

  FIG. 4 is an overall block diagram showing a control system of the belt positioning device. The control target includes a belt, a roller that stops moving the belt, a motor that rotates the roller, and position detection that detects the position of the belt. The target position command and the control target position are compared, and a control amount is given to the control target by the FB controller. When the belt approaches the vicinity of the stop position, it is determined whether or not reset (Reset) is necessary, and a Reset signal is given to the FB controller. Further, the FF controller gives a control amount that makes both the target position and the control target position equal. This compensates for the delay of the FB controller.

  FIG. 5 is a profile of the target position locus and the speed at that time. When starting up, start up as soon as possible. Even if the target value cannot be followed, there is a constant velocity section next, so that the target value can be followed. When decelerating and stopping, in order to stop accurately at the stop position, a slow target position trajectory is set so as not to go too far.

  FIG. 6 is a diagram showing a control system of the position control means, and includes a feedback calculation unit (FB controller) and a feedforward calculation unit (FF controller).

FIG. 7 is a block diagram of target position switching. The connection between the ramp function and one of the step functions is selectively switched. The function formula is expressed below.
Refc (s) = 1 / (da3 * dsigma ³・ s ³ + da2 * dsigma ²・ s ² + da1 * dsigma ・ s + 1)
Here, the symbols da3, da2, da1, and dsigma in the above formula are constants, and by changing these values, a fast response or a slow response can be arbitrarily created. The symbol S is a Laplace operator. The ramp function 1 / S2 is selected during startup and constant speed, and the step function 1 / S is selected during deceleration stop.

FIG. 11 is a target position trajectory, and represents the relationship between the target position and the speed profile at the time of activation and constant speed. The total moving distance ytotal is ytotal = yst + ydec.
The deceleration switching point is a point at which the differential speed profile is “0”, that is, the acceleration is “0”. It has a gentler profile when decelerating than when accelerating.

Further, as shown in FIG. 6, since “output Y” and “refp” are equal only by the feedforward operation unit, the feedback delay can be compensated by feedforward, and the tracking error can be eliminated.
The symbol u is deleted from the following simultaneous equations.
u = 1 / P (s) ・ Refc (s) ・ r + FB (s) (Refc (s) ・ rY)
Y = P (s) ・ u
If the symbol u is deleted, Y = Refc (s) · r, and the influence of FB (s) can be eliminated.
Here, FB (s) indicates an FB controller.

  FIG. 8 is a block diagram of the open loop transfer function, and is a Bode diagram of the open loop transfer function from the feedback controller of FIG. 4 to the controlled object. Since the low band has an inclination of −60 DB / DEC, the deviation between the target position and the measurement position can be set to “0”, and the belt positioning device can be accurately stopped at the target position.

A distance Xsp from the belt stop position, a speed Vsp at that time, and a current value Isp at a constant speed are used. The friction torque Tf, the friction force F, the belt drive shaft radius r, the inertia moment J of the drive unit, and the motor torque constant Kt are used.
In order to set the speed Vstop at the stop position to “0”, the time from the speed Vsp to Vstop is tstop and the acceleration is adec.
Vstop = Vsp + adec · tstop = 0
tstop = -Vsp / adec

Also,
Xsp = Vsp · tstop + 1/2 · adec · (tstop) ²
= Vsp · (−Vsp / adec) + ½ · a · (−Vsp / adec) ²
= -Vsp ² / adec
become.

When the acceleration adec is considered as adec = −Vsp ² / Xsp and the angular acceleration is dω / dt, it can be expressed by the following equation.
dω / dt = adec / r

The equation of motion between the motor generated torque Tm and the friction torque Tf is as follows.
Tm = J · dω / dt + Tf
If the motor current Im is
Tm = Kt · Im
Im = (J · dω / dt) / Kt + Tf / Kt
= (J · dω / dt) / Kt + Isp
What is necessary is just to give the signal represented by said code | symbol Im to a motor as Tstop time feedforward electric current.

  FIGS. 9 (1) and 9 (2) are configuration diagrams of the belt moving device of the first invention. FIG. 9 (1) is a configuration in which the rotary encoder is provided coaxially with the drive roller. An example is shown. On the other hand, FIG. 9B shows a configuration example in the case where the rotary encoder is provided on a separate axis from the drive roller. In the configuration example (1) and the configuration example (2), the detection sensor A11 that reads a marker (not shown) provided on the front or back surface of the belt by a pickup A (not shown) and the slit of the wheel of the rotary encoder are read. And detection sensor B12.

In these configuration examples, FIGS. 9A and 9B, the belt 16 is moved by a rotational force by a motor (not shown) attached to the drive roller 13. The belt 16 is rotationally driven by a motor and rotates via a driving roller 13, a driven roller 14, and a tension roller 15.
In the case of (1), the rotation of the drive roller 13 is detected by the detection sensor B12 with the rotation of the rotary encoder wheel 17 directly connected to the rotation shaft of the drive roller 13. In the case of (2), the detection sensor B12 detects the rotation of the timing pulley 18 directly connected to the rotation shaft of the drive roller 13 and the rotary encoder wheel 17 connected via the timing belt 19. .

FIG. 10 shows an example of a paper conveyance belt feeding mechanism of the inkjet image forming apparatus, FIG. 11 shows the relationship between the target position and speed profile at startup and constant speed, and FIG. 12 shows the relationship between the target position and speed profile at deceleration. Represents.
10 and 11, a rotary encoder pulse and a belt marker signal when the belt moving device is driven. The rotary encoder pulse is counted by a counter (not shown), and a rising signal of the belt marker signal is received. The angle of the rotary encoder is reset by resetting the counter. By interpolating the surface position signal with the rotary encoder pulse, the position resolution is improved, so that precise positioning is possible.

  FIG. 10 shows an example of a paper conveyance belt feeding mechanism of the inkjet image forming apparatus. Paper enters from the transport direction. A conveyance roller is rotated by a motor (not shown). The conveying belt is charged with static electricity by the charging roller. The paper is electrostatically attracted and stops at the position of the carriage where the inkjet head (not shown) is located. Read the marker on the back of the transport roller with a reflective encoder. A rotary encoder including a code wheel and a transmission encoder is attached to the rotation shaft of the transport roller. A position signal from the position detection sensor is fed back, and a control calculation is performed by the CPU, and a current command value is given to the motor amplifier. By this control, the motor stops rotating. The conveying belt is neutralized by a neutralizing brush.

It is a schematic diagram which shows the continuous FB controller of embodiment of this invention. It is a figure showing an example of composition of a discrete value system controller of an embodiment of the present invention. It is a block diagram for demonstrating the control system corresponding to FIG. 1 and FIG. 1 shows an overall block of an embodiment of the present invention. A target position locus in relation to a target position and a target speed is shown. It is a block diagram showing the control system of the position control means. It is a block diagram showing the control system of the target position switching means. It is the block diagram and control characteristic figure showing the open loop transfer function system. It is a conceptual diagram for demonstrating control of a belt drive system. It is a conceptual diagram for demonstrating the whole control system. It is the profile showing the relationship between the target position and speed at the time of starting and constant speed. It is the profile showing the relationship between the target position and speed at the time of deceleration.

Explanation of symbols

11 Detection sensor A
12 Detection sensor B
13 Driving Roller 14 Followed Roller 15 Tension Roller 16 Belt 17 Rotary Encoder Wheel 18 Timing Pulley 19 Timing Belt

Claims (10)

In a belt positioning device comprising a belt, a roller for moving / stopping the belt, a motor for rotating the roller, and a position detecting means for detecting the position of the belt,
Means for adjusting an integration amount of a detection value from the position detection means to calculate an integral value when the predetermined point of the belt approaches a stop position as a target position;
A belt positioning apparatus comprising: position control means for performing position control for stopping the belt at the target position based on the calculated integral value.   2. The belt positioning apparatus according to claim 1, wherein the target position is a position obtained by changing a trajectory when the belt is started and when the belt is decelerated and stopped.   2. The belt positioning apparatus according to claim 1, wherein the position control unit includes a feedback calculation unit that calculates a feedback value corresponding to the calculation of the target position, and a feedforward calculation unit that calculates a feedforward value. . The transfer function that creates the target position is:
Refc (s) = 1 / (da3 * dsigma ³・ s ³ + da2 * dsigma ²・ s ² + da1 * dsigma ・ s + 1)
When
At startup and constant speed, Refst (s) = Refc (s) / s ² ,
During deceleration stop, Refsp (s) = Refc (s) / s,
The belt positioning device according to claim 1, wherein the belt positioning device is a belt positioning device.   The feedforward calculation unit is characterized in that “Refc (s)”, which is a part of a transfer function for calculating the target position, is an inverse of the transfer function P (s) of the belt positioning device. Item 5. A belt positioning device according to item 3 or 4.   4. The belt positioning device according to claim 3, wherein the feedback calculation unit has a low band of an open loop transfer function having an inclination of at least −60 DB / DEC.   2. The belt positioning apparatus according to claim 1, wherein the feedforward value is changed according to a frictional force value obtained from a speed near the belt stop position and a current value at a constant speed.   8. The belt positioning apparatus according to claim 7, wherein the feedforward value is tabulated.   The belt position detection is performed by detecting an angle of a detection sensor A that reads a marker provided on the surface of the belt and a rotary encoder attached to a shaft that drives the belt or a rotary encoder attached to a motor shaft. 2. The belt positioning apparatus according to claim 1, wherein the position of the belt is detected by position detection means comprising a sensor B.   The belt positioning device according to claim 1, wherein the belt moving device is a paper conveyance belt, and is used in an ink jet type image forming apparatus.

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