JPH0726729Y2 - Position control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a position control device for controlling the position of a moving body with high accuracy.

(Prior Art) For example, when controlling the axis of a robot arm, the head position of a CD (compact disc) player, a video disc player, a hard disk memory, and the like, extremely precise and stable position control is required. Become. High-speed and highly accurate position control is also required for axis control of a glass master automatic transfer robot in a compact disk cutting machine. Techniques for such position control include, for example, automation (November 1985 vol.30,
No. 13, p. 92). A position control device as shown in FIG. 3 is introduced here for simplification.

In FIG. 3, this device includes an actuator 21 for conveying and driving a moving body, a speed detector 22 for detecting the moving speed of the moving body, and a position detector 23 for detecting the current position of the moving body.
And are provided. The detection output of the speed detector 22 is
The input is connected to the speed servo circuit 24, and the speed servo circuit 24 controls the actuator 21 so as to drive the moving body at the set speed.

On the other hand, the output signal of the position detector 23 is the current position counter 28
Wired to enter. Also, the current position counter
The output of 28 is input to the deviation counter 26 together with the output signal of the destination position information 25. The deviation counter 26 receives the current position information output from the current position counter 28 and the movement destination position information 25 corresponding to the target movement destination position of the moving body, and takes the difference between them to obtain the D / A converter 27. The digital signal is output toward. The deviation converted into an analog signal in the D / A converter 27 is input to the speed servo circuit 24 to obtain a movement control signal and sent to the actuator 21. That is, in this device, the deviation counter 26 finds the difference between the current position and the destination position, and supplies the deviation to the speed servo control circuit 24 through the D / A converter 27 so that the deviation is always zero. To drive the actuator 21. As a result, the actuator 21 accurately moves the moving body (not shown) to the target position.

By incorporating a so-called speed servo loop, which is composed of the speed detector 22 and the speed servo circuit 24, into the loop for this position control, the reaching speed when reaching the target position or the target position is reached. In this case, vibration and the like are suppressed, and quick position control is performed. This is also a well-known technique in the past.

(Problems to be solved by the device) By the way, in the above device, the speed servo circuit is used.
At 24, temperature drift and DC offset may occur due to the temperature characteristics of the circuit and the influence of various other unique circuit constants.

In both cases, for example, the amplification factor changes,
Also, the preset zero level will fluctuate. In this case, the output of the deviation counter 26 decreases as it approaches the target position, but if the output becomes less than a certain value, the voltage generated by the drift or offset and the movement control signal voltage are balanced, and Although there is an output from the deviation counter 26 in order to further approach the target position, the speed servo circuit 24 itself does not drive the actuator 21.

As a result, there is a problem that the moving body cannot reach the target position.

In the above circuit, the output of the deviation counter 26 becomes smaller as the moving body approaches the target position, and the D / A
Since the output of the converter 27 is also small, the speed servo circuit
In 24, a circuit with a large amplification factor is required to obtain the sufficient gain. However, this has a disadvantage that it is disadvantageous when considering temperature drift and DC offset.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a position control device capable of accurately moving a moving body to a target position even when a temperature drift or a DC offset occurs. It is intended.

(Means for Solving Problems) A position control device of the present invention comprises a moving body driving means for driving a moving body, a position detecting means for detecting current position information of the moving body, and a moving destination of the moving body. A movement control unit that compares the position information and the current position information, and repeats an operation of controlling the moving body driving unit so as to reduce the difference between the two, and the destination position used in the operation that is continuous with each other. When a state where the information and the current position information are invariant occurs, a counter that counts the number of times the state continues is provided, and the movement control means has a count value of the counter exceeding a predetermined value and the state is When continuing, the operation is executed by adding a predetermined offset correction value to the destination position information.

(Operation) In the above device, when the difference between the current position information of the moving object and the destination position information is reduced, and the position control becomes impossible due to the influence of temperature drift or DC offset, A predetermined offset correction value is detected and added to the destination position information to forcibly move the moving body. As a result, it becomes possible to escape from the uncontrollable state and perform the position control of the moving body with higher accuracy.

(Embodiment of the Invention) FIG. 1 is a block diagram of a position control device showing an embodiment of the present invention.

This apparatus includes a moving body 1, a moving body driving means 2 for carrying and driving the moving body 1, a position detecting means 3 for detecting the current position of the moving body, and a current position output from the position detecting means 3. And a movement control means 6 for processing the information 4. In addition to the current position information 4, the destination position information 5 is also input to the movement control means 6.

Further, there is provided a counter 7 which receives a predetermined signal from the movement control means 6 and performs a predetermined process when the current position information 4 and the destination position information 5 are updated. The output of the counter 7 is connected to be input to the movement control means 6. The movement control means 6 outputs the position control signal 9 accordingly. The output of the movement control means 6 is input to the moving body drive means 2 via the D / A converter 8. Further, the moving speed of the moving body 1 is the speed detector 10
And the speed servo signal 11 is detected by the moving body driving means 2
Is configured to enter.

Here, the moving body 1 includes a linear motor that is linearly driven, a servo motor that rotationally drives an arm such as a motor, and the like. The position detecting means 3 is composed of a well-known position detecting sensor such as a linear scale if it is linear and a rotary encoder if it is rotational. For example, as a rotary encoder, one that optically reads the rotation angle of its axis is well known.

The current position information 4 is a digital signal of several bits that represents the position of the moving body with digital data. The destination position information 5 is a digital signal corresponding to the destination position supplied from a host device (not shown) in order to move the moving body 1 to a predetermined position. The movement control means 6 is a circuit for reading the current position information 4 and the like to perform a calculation and output a movement control signal 9, and is composed of a microprocessor or the like.

The movement control means 6 stores both the current position information 4 and the movement destination position information 5 of the present time and the previous time, respectively, but the counter 7 compares them and
It is a circuit that increments the count value by 1 when a state in which the destination position information and the current position information used in continuous operations are unchanged. Therefore, this circuit is composed of a latch circuit, a comparison circuit, a counter and the like.

The D / A converter 8 is a circuit that converts the digital position control signal 9 output from the movement control means 6 into an analog position control signal and supplies the analog position control signal to the moving body drive means 2. The moving body driving means 2 uses the speed servo signal 11 output from the speed detector 10.
Is a circuit for controlling the position of the moving body 1 based on the position control signal 9 output from the movement control means 6, while forming a speed servo loop for controlling the speed of the moving body 1. This is composed of a voltage and current control circuit using a known phase control element and the like.

The position control device having the above configuration operates as follows. A flowchart for the operation is shown in FIG.

The operation of the device of the present invention will be described with reference to FIGS. 1 and 2.

First, when the operation is started, the movement control means 6 reads the current position information 4 and the movement destination position information 5. Then, the current position information 4 just read is stored in the register for storing the current position information 4 provided in the movement control means 6 (step S1). Next, the current position information 4 is read again (step S2). Next, the counter 7 compares the current position information 4 with the destination position information 5 (step
S3). Here, if the two are equal, position control is not necessary, so the process returns to reading the current address again (step S2).
If the destination position information 5 and the current position information 4 are not equal, it is determined whether or not the current position information 4 is equal to the current position information already read in the register (step S4).
If they are not equal, the count value of the counter 7 is set to 0, and the current position information 4 is written and updated in the register (step S5). Then, the difference between the destination position information 5 and the current position information 4 is taken, this is multiplied by a predetermined present G, and the offset value is added to create the movement control signal 9 (FIG. 1) (step S6). ). By this position control signal 9, the moving body drive means 2 moves the moving body 1 by a predetermined amount. Then, the movement control means 6 finishes one operation. afterwards,
The movement control means 6 again moves to read the current position information (step S2). In this device, such an operation is repeated at a predetermined cycle.

By the way, when the value of the position control signal 9 output from the movement control means 6 becomes extremely small, as described above, the position control may not be possible due to temperature drift, DC offset, or the like. . In this case, in step S4, the current position information 4 currently read and the current position information 4 previously stored in the register are invariable in successive operations. In this case, the counter 7 is incremented by 1 (step S7). Next, it is determined whether or not the count value of the counter is larger than the predetermined value C (step S8). For example, this C is 5 or 10
Or set it to an appropriate constant. When the count value is smaller than the constant C, the counter 7 is simply incremented to read the current position information 4 again (step S2). However, if this count value is a constant C
If it becomes larger than the above, the offset correction value K is further added to the offset added to the output in step S6.
Is added (step S9). In this case, the sign of K is the same as the output of the movement control means 6. That is, the value of K is set so that the moving body is moved forward more when it should be moved forward, and is moved backward more when it should be moved backward.

By the above procedure, when the output of the movement control means 6 is obtained, even when the constantly set calculation cannot drive the moving body 1 against the temperature drift, etc.,
It becomes possible to drive the moving body so as to approach the target position forcibly.

Further, in the device of the present invention, not only the difference between the current position information 4 and the destination position information 5 is taken as the position control signal 9, but also the difference between the two is multiplied by a predetermined gain G and output. There is. Such an arithmetic circuit has a circuit configuration in which the difference between the current position information 4 and the movement destination position information 5 is input to the address of the read-only memory and the data corresponding to the calculation result is output. , Easily obtained.

In the present invention, since the predetermined gain can be set at the stage of digital data in this way, a large amplification factor is not required at the stage of analog processing in the moving body driving means 2, so-called temperature drift, DC offset, etc. Can be controlled more stably.

(Effects of the Invention) The position control device of the present invention described above has a small difference between the current position information and the destination position information, and when the position control of the moving body becomes impossible due to the influence of temperature drift or the like, Since the state is detected and the moving body is moved by giving a larger drive amount, highly accurate position control is possible. Further, since the predetermined gain is set when the position control signal is a digital signal, it is possible to perform strong control against temperature drift or the like in the moving body driving means.

[Brief description of drawings]

FIG. 1 is a block diagram of a position control device showing an embodiment of the present invention, FIG. 2 is a flowchart explaining its operation, and FIG.
FIG. 1 is a block diagram showing an example of a conventional position control device. 1 ... moving body, 2 ... moving body driving means, 3 ... position detecting means, 4 ... current position information, 5 ... movement destination information, 6 ...
Movement control means, 7 ... Counter.

Claims (1)

[Scope of utility model registration request] 1. A moving body driving means for driving a moving body, a position detecting means for detecting current position information of the moving body, and a moving destination position information of the moving body and the current position information, A movement control unit that repeats an operation for controlling the moving body driving unit at a predetermined cycle so as to reduce the difference between them, and a state in which the destination position information and the current position information used in the mutually continuous operation remain unchanged In the case of doing, equipped with a counter that counts the number of consecutive times of that state,
When the count value of the counter exceeds a predetermined value and the state continues, the movement control means adds a predetermined offset correction value to the movement destination position information and executes the operation. Control device.