JPH01128104A - Positioning method for actuator - Google Patents

Abstract

PURPOSE:To obtain the prescribed restoring force when the position of an actuator gets close to its target position and to improve the positioning accuracy of the actuator by defining the value between central values as the control target value in addition to the central value between partial sections respectively and performing the control so that the coincidence is secured between the control position of the actuator shown by the central value between partial sections and the target position. CONSTITUTION:The target positions of a motor (actuator) 1 moving within a section A divided into plural continuous partial sections A0, A1... are set at the middles (0.5), (1.5)... between the central values 0, 1... of the sections A0, A1.... Then the moving section A of the motor 1 is fractionated by means of a rotary plate 2 and a fixed plate 3 of an incremental rotary encoder E and those sections A0, A1... are discretely detected through rotations of a rotary position 2. Based on this detection, the control is performed so that the coincidence is obtained between the position of the motor 1 and the control target value. Thus the prescribed restoring force is secured even when the motor 1 gets close to its target position. As a result, the positioning accuracy of the motor 1 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an actuator positioning method for discretely detecting the position of an actuator such as a motor and positioning the actuator, and particularly relates to measures for improving positioning accuracy. .

(Prior Art) Conventionally, in the field of digital control, there has been an actuator positioning method in which the position of an actuator such as a motor is discretely detected using, for example, an encoder, and the detected value is used to position the actuator. In that case, the following methods are generally known.

That is, to explain the positioning method using the incremental rotary encoder (E) shown in FIG. The rotary plate (2) is a disc-shaped rotary plate attached to the rotary plate (2), and slits (2A) formed by subdividing the circumferential direction at regular intervals are provided near the outer circumferential portion of the rotary plate (2). Further, (3) is a fixed plate provided in contact with the rotary plate, and the upper outer edge of the fixed plate (3) is formed in a partial circular shape that follows the outer shape of the rotary plate, and the outer edge of the fixed plate (3) is Slit (2A) of rotating plate (2)
Two first and second slits (3A), (3A) having the same spacing and width as the slit (2A)
B) are provided on the left and right sides of the fixed plate (3). The two slits (3A) and (3B) are 1/4 pitch from each other with respect to the slit (2A) of the rotary plate (2), that is, 90
They are located so that they have a phase difference of . Here, each of the slits (2A), (3A), and (3B) has a shape in which the slit width and the slit interval are equal. Moreover, (4A) to (4C) are each slit (3A) from the front of the fixing plate (3).

(3B) three light emitting diodes for inputting light;
(5A) to (5C) are photodiodes for receiving optical signals from the light emitting diodes (4A) to (4C) at the rear of the rotating plate (2). In addition, (2C) and (3C) in the figure
) are zero slits formed on the rotating plate (2) and the fixed plate (3), respectively.

When the rotary plate (2) of the incremental rotary encoder (E) rotates, its slit (2A) and the two slits (3A) and (3B) of the fixed plate (3) rotate.
Due to the change in the positional relationship between the two photodiodes (5A) and (5B), two input signals as shown in FIG. 4 (+) and () are obtained from the slit (3A). Rectangular pulse signal (Fig. 4 (i)
A pulse signal of the same shape (see FIG. 4(n)) having a phase difference of 90° with respect to the pulse signal (see FIG. 4(n)) is obtained.

By changing the section every time the signal value of the combination of the above two pulse signals changes, the movement section (A) of the motor (1) is subdivided into a plurality of sections as shown in FIG. Section... (Ao).

(AI), (A2), . . . are obtained. Then, the encoder (E) determines the rotational position of the rotary plate (2) in each partial section... (Ao), (AI), (
A2), median value of..., rOJ, rN, r2J
.

... is detected discretely (see Figure 4 (to))
.

That is, the partial interval from the zero signal slit (2C) -,
By integrating the numbers (Ao), (AI), (A2), -, the position of the motor (1) can be detected with a resolution of 1/4 pitch of the slit (2A). .

When positioning the motor (1) using the incremental rotary encoder (E) with the above structure, in the conventional method, as shown in FIG. ), (AI)+(A2)
The median value of l..., for example, rOJ, rlJ, is set as the control target value θR, and the rotation angle position θ of the motor (actuator) (1) detected by the encoder (E) is set as the control target value θR.
is controlled so that it matches the control target value θR.

FIG. 3 shows an example of a control system for a motor positioning device using the above-mentioned incremental rotary encoder (E).

In the figure, (7) is the first addition point that calculates the algebraic difference between the control target value θR of the motor position input from a target position calculator (not shown) and the actual motor position θ, and (8) is the position loop gain element that multiplies the calculation result θR-〇 of the first addition point (7) by the position loop gain Kp, and (9) is the multiplication result Kp (θR - θ) of the position loop gain element (8). = θR9 or less, referred to as target angular velocity) and the motor angular velocity θ. (10) is a second addition point that calculates the algebraic difference between the motor angular velocity θ and the motor angular velocity θ. This is a speed loop gain element for outputting a control current i that multiplies and controls the motor (1). Further, (F) is a dynamics of a controlled object, such as a joint of a robot, and the dynamics (F) is a first integral element (
11), and a second integral element (12) that integrates the angular velocity θ of the first integral element (11) to obtain the motor angle θ. Note that the angle feedback path and the angular velocity feedback path include an encoder (E) and a tachogenerator (E) for detecting the angle and angular velocity of the motor (1), respectively.
13) are arranged.

In the above control system, the algebraic difference between the control target value θR and the motor angle θ detected by the encoder (E) is calculated at the first summing point (7), and the position loop gain element (8
), the target angle θR is calculated. Then, at the second summing point (9), the algebraic difference between the target angular velocity θR and the motor angular velocity θ detected by the tachogenerator (13) is calculated, and the algebraic difference between the target angular velocity θR and the motor angular velocity θ detected by the tacho generator (13) is calculated, and then the motor (1
) flows to the motor (1). As described above, the motor angle θ is controlled to match the control target value θR.

(Problem to be solved by the invention) However, in the above conventional method, the encoder (E)
When the actual movement position (rotation angle) θ of the actuator (motor) (1) detected by a position detection device such as When set as the target value, the motor (1
) falls within the subsection (A3) 1, almost no control current i flows through the motor (1), and the rotational position of the motor (A2) or (A4) exceeds the subsection (A3).
A predetermined control current i for restoring the motor angle θ to the control target value θR flows only after the motor angle θ is moved to . That is, as shown in the upper diagram of Fig. 9, each partial section...
1 of (Ao), (A+), (A2),...
Assuming that the gain for each unit is 1, and the signal amount that produces a restoring force that tries to make the control current i input to the motor (1), that is, the motor angle θ, match the control target value θR, is the relative feedback amount ■, then the relative Changes in the feedback zI with respect to the motor angle θ become a step-like function with a negative slope, and when the rotational position of the motor (1) is in the partial section (A3), the relative feedback amount I becomes zero. As a result, due to rotational inertia, the partial interval (A3)
It will oscillate between the upper and lower limit values of , or in some cases, over the upper and lower partial sections (A2) and (A4) (see Figure 9 below), especially in cases where high accuracy is required. There is a problem that accurate positioning cannot be performed.

The present invention has been made in view of the above, and its purpose is to narrow the convergence range of the actuator by ensuring that a predetermined restoring force is obtained even when the actuator approaches the control target value. The purpose is to improve positioning accuracy.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention includes a plurality of continuous partial sections..., (Ao), (A+).

The position of the actuator (1) moving within the movement section (A) consisting of (A2), ... is defined as the median of the partial sections -, (Ao), (A+), (A2), - in which it is located. Discretely detect the actuator (1
), and the control target position of actuator (1) is assumed to be an actuator positioning method in which the movement position is controlled based on the deviation between the position of the actuator (1) and the control target position of the actuator (1). , (A2), . . . is set to an intermediate value between the median values.

(Function) By the above method, in the present invention, the actuator (1)
moves within the moving section (A) for each partial section...

(Ao), (A+), (A2), ...
If you move over the area, the movement position will be in each subsection...
, (Ao).

It is detected discretely as the median value of (A+), (A2), . . .

And each of the above partial intervals..., (Ao), (
The intermediate value between the median values of A+), (A2)l... is set as the control target value, and each partial interval..., (Ao),
(A+).

(A2) Since the movement position of the actuator (1), which is expressed by the median value of , is controlled to match the control target value, when the movement position of the actuator (1) approaches the control target value, Also, if a slight displacement occurs in the moving position with respect to the control target value, a predetermined restoring force will be obtained against the minute displacement, and the movement will converge in the vicinity, thus improving the positioning accuracy. be able to.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

2, 3, and 4 respectively show the schematic configuration of the incremental rotary encoder (E), the signal transmission path of the control system, and the position detection characteristics of the incremental rotary encoder (E) according to the embodiment of the present invention. , the contents of which have already been explained, so the explanation will be omitted here.

Here, as a feature of the present invention, as shown in FIG. ,・
The boundary value of..., that is, each median value..., rob.

Intermediate value between rN, r2J, . . ., rO, 5J.

I am trying to set it to rl, 5J, r2.5J, . That is, each partial interval..., (Ao).

(A+), (A2), ... median rNJ (
The control target value is set by adding 0.5 to N (N is an integer). Then, the motor angle θ is the control target value/
..., rO, 5J, rl, 5J, r2゜5''.

It is controlled by the control system shown in Fig. 3 so as to match...

Therefore, in the above embodiment, when r3.5J is set as the control target value, for example, the change in the relative feedback amount I with respect to the motor angle θ is as shown in the upper diagram of FIG. 5, with respect to the motor angle θ. It becomes a step-like function with a negative slope, and does not become zero even in the partial interval (A3). That is, the control target value is r3.
5J, the partial interval (A3) is 0. 5. Relative feedback amount of -0,5 in partial interval (A4)■
is obtained, and when the motor angle θ is smaller than the control target value "3°5" (partial interval (A3)), θ increases, and when the motor angle θ is larger than the control target value r3.5J A predetermined restoring force acts on (partial section (Aa)) in the direction in which θ decreases.

As a result, the motor angle θ is adjusted in three partial intervals (A2) to 3 in the set partial interval (A3) as in the conventional case.
(A4) As shown in the lower figure of Fig. 7, the two partial sections CAg),
(A4) converges very close to the boundary value "3°5", and the positioning accuracy of the motor (1) is improved as much as possible.

Next, an experimental example of the present invention will be explained. 7 and 8 show the experimental results of positioning the motor (1) using the incremental rotary encoder (E).
The figures show experimental data from conventional positioning methods, with time plotted on the horizontal axis and positional fluctuations plotted on the vertical axis, with the same magnification. A comparison of these two figures shows that the conventional method does not cause uncertain fluctuations in the range from the subsection (A2) that exceeds the lower limit of the subsection (A3) to one side of the subsection (A3). However, in the method of the present invention, the boundary value r3.5J of subintervals (A3) and (A4)
It can be seen that it converges to a position extremely close to .

Note that the detection device applied to the present invention is not limited to the above-mentioned incremental rotary encoder (E), but is, for example, a fixed encoder in which a large number of slits are provided on a rotating plate provided with a fixed pattern of voids. A so-called absolute rotary encoder detects the absolute rotation angle of an actuator such as a motor connected to a rotary plate from the light transmission pattern of both plates by arranging a rotor in a two-phase stator. The rotational position of the actuator connected to the rotor can be determined with an accuracy of 1/4 wavelength from the wave peak of the secondary voltage that is shifted by a certain rotation angle generated on the rotor by two applied sine wave and cosine wave voltages. The so-called resolver used for detection is a scale base in which a large number of minute magnetic poles are continuously embedded, and two magnetic heads are placed at positions 90° out of phase with respect to the pitch of the magnetic poles. By combining the magnetic field change patterns, the relative position change between the scale base and the magnetic head can be reduced to 1/4.
The present invention can be applied to a device that discretely detects the moving position of an actuator, such as a so-called magnetic scale that detects with pitch accuracy, and can exhibit the same effects as the above embodiment.

Further, the actuator is not limited to the motor (1) of the above embodiment, and it goes without saying that various types such as hydraulic pistons, pneumatic pistons, etc. can be used.

(Effects of the Invention) As explained above, according to the actuator positioning method of the present invention, the median value of each partial section within the movement section in which the actuator moves is discretely detected, and the detected value is used to move the actuator. When performing positioning, in addition to the median value of each partial interval, the intermediate value between the respective median values is set as the control target value, and the actuator movement position represented by the median value of each partial interval is set to the control target value. Since the control is performed so that the movement position of the actuator approaches the control target value, a predetermined restoring force can be obtained even when the actuator movement position approaches the control target value, and the control can be converged near the control target value. Therefore, positioning accuracy can be improved. It is possible to improve the

[Brief explanation of the drawing]

1 to 5 show embodiments of the present invention, FIG. 1 is an explanatory diagram of a control target value setting method, FIG. 2 is an exploded perspective view showing a schematic configuration of an incremental rotary encoder, and FIG. 3 is a control A block diagram showing the system configuration. Figures 4 (+) to (to) show the position detection characteristics of the incremental rotary encoder. Figure 4 (+) shows the received signal from the first slit, and Figure 4 (n) shows the position detection characteristics of the incremental rotary encoder. is a received signal from the second slit, FIG. 4 is a diagram showing a partial section of the movement section obtained by combining the signals from both slits, and FIG. 5 is a relative feedback amount characteristic diagram with respect to a change in motor angle. Figures 6 and 7 show experimental examples of the variation characteristics of the motor position with respect to time,
FIG. 6 is a diagram showing the results of an experiment according to the method of the present invention, and FIG. 7 is a diagram showing the results of an experiment according to the conventional method. FIG. 8 is an explanatory diagram of a control target value setting method using a conventional method, and FIG. 9 is a relative feedback amount characteristic diagram for changes in motor angle using a conventional method. (1)...Motor (actuator), (E)...
Incremental rotary encoder, (A)...moving section, (Ao), (AI), (A2) partial section. Fig. 2 Fig. 4 1---Ao AI A2 A3---Heer'' Fig. 1 Fig. 8

Claims (1)

[Claims] (1) Multiple consecutive partial sections..., (A_0), (
A moving section (A) consisting of A_1), (A_2), ...
The position of the actuator (1) that moves within the partial section where it is located..., (A_0), (A_1), (A_
2) In the actuator positioning method, the movement position is controlled based on the deviation between the position of the actuator (1) and the control target position of the actuator (1) by discretely detecting the median value of Set the target value to each of the above partial intervals..., (A_0), (A_1), (A_
2) An actuator positioning method characterized by setting an intermediate value between the median values of .