JPH04265699A - Motor driving method - Google Patents

Abstract

PURPOSE:To suppress vibration of a step motor or a DC motor at the time of starting or stopping. CONSTITUTION:When a motor is started, it is accelerated with a positive increasing acceleration and in the way of acceleration, it is switched to decreasing acceleration. When the motor is stopped, it is decelerated with a negative decreasing acceleration and in the way of deceleration, it is switched to deceleration with increasing acceleration. According to such motor driving method, vibration of motor can be suppressed at the time of starting and stopping.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving motors such as stepping motors and DC servo motors.

0002

[Prior Art] Conventionally, in a stepping motor, if the required motor speed (driving frequency) is small, it can be driven at a predetermined frequency immediately from a stopped state (Fig. 2 (a)
), but if the required frequency is large, the method shown in Figure 2 (
As shown in b), it was driven using a slow-up/slow-down method (trapezoidal drive) that linearly accelerates or decelerates from a low frequency to a high frequency. An example using a stepping motor driven in the sub-scanning direction will be described with reference to FIG. 3.

In FIG. 3, reference numeral 11 denotes a housing, and a shaft 4 and a rail 10 are fixed to the housing 11. Further, 8 is an optical unit equipped with a light source, a mirror, etc. (not shown), and one side of the optical unit 8 is mounted on a bearing 7.
The optical unit 8
is slidable in the Y direction. Furthermore, the optical unit 8
The connecting fitting 6 is pressed against a belt 3 stretched between a motor pulley 2 and a tension pulley 5 of the stepping motor 1. The driving force of the stepping motor 1 is transmitted to the optical unit 8 via a motor pulley 2, a belt 3, and a connecting fitting 6. When driving the optical unit 8 with the stepping motor 1, in the conventional motor driving method, the times t0 and t1 in FIG. 4(a) or the time t1 in FIG.
At times t0, t1, t2, and t3 in a), vibrations occur on the roller 9 side of the optical unit 8. For example, when the motor drive method is trapezoidal drive, the relationship between the optical unit and the document is as shown in FIG. The position of the first optical unit is Y0, the leading edge of the document is Y1, and the trailing edge of the document is Y2. First, while the stepping motor is slowed down, the optical unit moves from Y0 to Y1. Next, Y
The document is read while moving from 1 to Y2. lastly,
It starts slowing down from Y2 and stops at Y3. Here, the time relationship between Y0 and Y3 corresponds to t0 to t3 in FIG. 5(a), respectively. Now, when vibration occurs in the optical unit at t0 and t1, when a document as shown in FIG. 7(a) is read, an image as shown in FIG. 7(b) is obtained.

0004

SUMMARY OF THE INVENTION The present invention aims to reduce the problem of conventional motor drive methods, namely the vibrations that occur when starting and stopping the motor.

[0005]

[Means for solving the problem] When starting the motor, start accelerating with positive acceleration while increasing the acceleration, start accelerating while decreasing the acceleration halfway, and when stopping the motor, start accelerating while increasing the acceleration. is a negative acceleration, starts decelerating while decreasing the acceleration, and then decelerates and stops while increasing the acceleration halfway.

[0006]

[Operation] When starting a motor such as a stepping motor or a DC motor, it starts accelerating with positive acceleration while increasing the acceleration, and then accelerates while decreasing the acceleration midway through, so that it starts smoothly. Furthermore, when stopping the motor, the motor starts to decelerate with a negative acceleration while decreasing the acceleration, and then decelerates while increasing the acceleration midway through, thereby smoothly stopping the motor.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be explained based on the drawings.

FIG. 1 is a characteristic diagram showing a method of driving a stepping motor according to the present invention. FIG. 1(a) is a characteristic diagram showing the rate of change in acceleration, where the vertical axis is the rate of change p in acceleration, the horizontal axis is time t, and the first half of slow-up (t0 to t1).
) is constant at t=k, second half of slow-up (t1-t2)
is constant at p=-k. Figure 1(b) is similar to Figure 1(b).
Acceleration is expressed in a characteristic diagram obtained by integrating a) (rate of change in acceleration) over time (vertical axis is acceleration a, horizontal axis is time t). Figure 1(c) is a characteristic diagram that integrates Figure 1(b) (acceleration) over time and represents the speed (the vertical axis is the speed v, the horizontal axis is the time t).
). The period from t0 to t2 is a slow-up period, the period from t2 to t3 is a period during which the document is read at a constant speed, and the period from t3 to t5 is a slow-down period. here,

[0009]

[Math 1]

[0010] In this example, a stepping motor is used, so when driving the motor with the speed curve shown in Figure 1(c), find the interval between the nth pulse and the n+1th pulse, and create a time table for slowing up. It is necessary to make Note that t2 to t3 are constant speeds, and the slowdown of t3 to t5 is t0 to t3.
Since the slow-up portion of 2 is simply reversed in time, here we will show how to create a timetable for the slow-up portion from t0 to t2.

FIG. 8 is a characteristic diagram showing the rate of change in acceleration during slow-up, and this is integrated twice to create a characteristic diagram representing speed. First, if Figure 8 is expressed as a formula, before and after t1,

0012

[Math 2]

(0≦t<t1) and

[0014]

[Math 3]

(t1≦t<t2). Integrating this over time, we get

[0016]

[Math 4]

[0017] and

[0018]

[Math 5]

It becomes as follows, and represents acceleration. In equation 4, since t=0 and α=0,

[0020]

[Math 6]

(0≦t<t1). Also, t=t1 in Equation 5 corresponds to t=t1 in Equation 6. Therefore, in Equation 5, when t=t1, a=kt1, and by substituting this, β=2kt1. Therefore, the number 5 is

0
022]

[Math 7]

(t1≦t<t2). time t
A characteristic diagram of the acceleration from 0 to t2 is shown in FIG. 9.

Next, in order to find the velocity, Equations 6 and 7 are integrated. Integrating numbers 6 and 7, we get

[0025]

[Math. 8]

[0026] and

[0027]

[Math. 9]

It becomes as follows. In Equation 8, the initial value is v
0 and γ=v0, then

[0029]

[Math. 10]

(0≦t<t1). Also, in equation 9, t=t1 corresponds to t=t1 in equation 10, so δ=-kt12+v0, and substituting this, we get

[
0031

[Math. 11]

(t1≦t<t2). Equations 10 and 11 result in a characteristic diagram as shown in FIG.

[0033] v1 is obtained by substituting t=t1 into equation 10.

00
34]

[Math. 12]

0035. The final velocity v2 is expressed as t in Equation 11.
Substituting =2t1 (=t2)

[0036]

[Math. 13]

0037.

[0038] Equations 10 and 11 assume that k is fixed, but in reality, the speed v0 at the start of slow-up
, the target velocity v2 at the end of the slow-up, and the time t2 required for the slow-up are often determined, and it is necessary to determine k from these. In number 13,

[0039]

[Math. 14]

Therefore, if we transform this with respect to k,

[0041]

[Math. 15]

##EQU1## k is expressed by v0, v2, and t1. Substituting number 15 into number 10 and number 11, we get

0043
]

[Math. 16]

[0044] and

[0045]

[Math. 17]

##EQU1## This represents the velocity v at time t during slow-up.

Now, a time table for starting the stepping motor is created by actually applying numerical values. As an example, v0=200pps (pulse pe
r s econd), v2=1000pps, t1
= 100msec (t2 = 200ms ec), then substitute the numerical values into Equation 16 and Equation 17, respectively.

004
8]

[Math. 18]

[0049] and

[0050]

[Math. 19]

It becomes [0051]. Also, the timetable is

0052
]

[Table 1]

From the left, the pulse number, the time t (msec) for which the pulse is issued, and the motor speed v
(pps), and the time until the next pulse tn (msec). Initially, t=0, so write 0 in the time column and substitute 0 for t in Equation 18. Then, v=200, so enter 200 in the speed column. The interval tn is the reciprocal of the speed, so 1/200=0.005sec=5msec. The second pulse time t is the first pulse time t
The sum of tn and tn is 5 msec. To the number 18 t
When 5 is substituted, v=201pps, and the interval tn is 1
/201≒4.975m sec. The time t of the third pulse is the time t of the second pulse plus the interval tn, 5+4.975=9.975. In this way, time t, speed v, and interval tn are determined in sequence to create a time table. Here, time t is 100 m sec
Until (t1), Equation 18 is used, and when it exceeds 100 msec, it switches to Equation 19. The process ends when it exceeds 200 msec.

[0054] When used in an actual device, this timetable can be calculated in advance on a personal computer or the like and stored in the ROM of the microcomputer in the device, or it can be calculated based on the motor speed and the capacity of the CPU in the device. If so, you can emit pulses while calculating. When emitting pulses, pay attention only to the interval tn in Table 1, and after emitting the nth pulse, tn
A timer or the like may be set so that the (n+1)th pulse is output after msec.

[0055] If you use this timetable in reverse,
It can be used as is when slowing down.

[0056]

[Effects of the Invention] When starting a motor such as a stepping motor or a DC motor, it starts accelerating with positive acceleration while increasing the acceleration, and then accelerates while decreasing the acceleration halfway, resulting in smooth starting operation. I do. When stopping the motor, the motor starts to decelerate with a negative acceleration while decreasing the acceleration, and then decelerates while increasing the acceleration midway through to achieve a smooth stopping operation. Therefore, vibration can be reduced when starting and stopping the motor. Furthermore, the motor drive method according to the present invention can be implemented by simply changing the program, and can shorten the development period and reduce costs.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the method of driving a stepping motor according to the present invention, in which (a) shows the rate of change in acceleration;
) represents acceleration, and (c) represents velocity, respectively.

[Fig. 2] Characteristic diagrams showing motor drive methods according to the prior art, in which (a) shows a method without slow-up and slow-down, and (b) shows a slow-up and slow-down method (trapezoidal drive), respectively. .

FIG. 3 is a schematic diagram of a driving portion in the sub-scanning direction in the image reading device.

FIG. 4 is a characteristic diagram showing a conventional motor driving method (no slow-up, no slow-down), in which (a) represents speed and (b) represents acceleration.

[Figure 5] Motor drive method using conventional technology (trapezoidal drive)
FIG. 3 is a characteristic diagram showing the speed, (b) the acceleration, and (c) the rate of change in the acceleration.

FIG. 6 is a diagram showing the positional relationship between the optical unit of the image reading device and a document in FIG. 3;

7 is an example of a read image when the image reading apparatus shown in FIG. 3 is driven by a motor according to a conventional technique, in which (a) is a document and (b) is a read image; FIG.

FIG. 8 is a characteristic diagram showing the rate of change in acceleration during slow-up of the motor drive method according to the present invention.

FIG. 9 is a characteristic diagram showing acceleration during slow-up of the motor driving method according to the present invention.

FIG. 10 is a characteristic diagram showing the speed during slow-up of the motor driving method according to the present invention.

[Explanation of symbols]

1 Steppign motor 2 Motor pulley 3 Belt 4 Shaft 5 Tension pulley 6 Connection fittings 7 Bearing 8 Optical unit 9 Roller 10 Rail 11 Housing

Claims (1)

[Claims] [Claim 1] In a motor driving method such as a stepping motor or a DC motor, when starting the motor, the motor starts accelerating with positive acceleration while increasing the acceleration, and then starts accelerating while decreasing the acceleration halfway. However, when stopping the motor, the motor starts to decelerate with a negative acceleration while decreasing the acceleration, and then decelerates while increasing the acceleration midway through, and then stops.