JPH04334992A - How to control servo equipment - Google Patents

Abstract

PURPOSE:To eliminate the lag of the detection time of a speed signal obtained from a discrete pulse signal, and to position load at a target position in a short time. CONSTITUTION:An operating state, in which the detection of speed can be executed accurately, is selected on the basis of a speed command value (VR) or the elapsed time after load is started, and adjustment matching the estimate of an observer 30 with an actual device is conducted. On the other hand, the observer 30 is not adjusted and the predetermined estimate is held under an operating state, in which the detection of speed cannot be executed accurately, and a servo device is driven by using the estimate of the observer 30.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo device, such as a machine tool or an information storage device, which performs precise positioning using a sensor such as a rotary encoder that generates discrete pulse signals.

0002

[Prior Art] As a servo device that positions a load to a target position in a short time, the technology used in the servo device is to configure a state observer (hereinafter referred to as an observer) and generate a continuous speed signal without phase lag. For example, JP-A-63-271
It is disclosed in Japanese Patent No. 728.

0003

[Problem to be Solved by the Invention] An error occurs between the speed estimated by the observer and the speed of the actual device due to uncertain factors. Therefore, the estimated value of the observer is adjusted to match the speed of the actual device. This adjustment of the observer compares the speed estimated by the observer with the speed detected by the actual device,
This is done by giving negative feedback to the error. However, since the speed detected by the actual device is determined based on the pulse period of a discrete pulse signal, detection errors may occur depending on the operating state of the actual device (acceleration state, deceleration state, constant speed state, etc.). are different. On the other hand, since the estimated value of the observer asymptotically converges to the speed of the actual device, there is a problem that the observer cannot be adjusted correctly if the speed detection error is large.

0004

[Means for solving the problem] An index for identifying the operating state of the actual device, such as a speed command value, a detected speed value,
The operating state suitable for the observer adjustment operation is identified from the motor current or the elapsed time after the load is started, and the observer adjustment operation is executed when this operation state is entered. In addition, if it is not appropriate to adjust the observer, you can change the initial setting value without performing the observer adjustment operation.
Alternatively, a method was adopted in which the results adjusted earlier were used.

[0005]

[Operation] In the method of detecting speed based on the pulse period of a discrete pulse signal, the speed detection error is minimized in a constant speed range where there is no change in acceleration, and speed can be detected correctly. This is a suitable operating state for adjusting the observer estimate to match the actual device.

[0006]

EXAMPLES The present invention will be explained in detail below based on specific examples. FIG. 1 is a block diagram showing one embodiment of the present invention. The load 1 may be the illustrated rotating load or may be a direct acting load. The motor 2 that drives the load 1 may be the illustrated rotary motor, or
A direct-acting motor such as a voice coil motor may also be used. The pulse generator 3 that detects the movement of the position of the load 1 or the motor 2 may be a rotary encoder as illustrated, for example, or a linear encoder. The controller 6 is comprised of a digital computer having an arithmetic processor, memory, oscillator, and input/output (I/O) functions. In this embodiment, each process within the controller 6 is shown in a block diagram for easy understanding.

The operation signal (U) of the motor 2 calculated in the controller 6 is output from the input/output (I/O) port 200 to the digital/analog (D/A) converter 5, and is output to the digital/analog (D/A) converter 5.
The signal is further outputted from the A converter 5 to the motor 2 via the power amplifier 4. The pulse generator 3 generates discrete pulse signals (xp
) is generated and a portion is sent to the counter 9. The position detector is composed of a pulse generator 3 and a counter 9. The counter 9 is an up-down counter and counts pulse signals (xp). The position detector of this example is
Position deviation (xR) from the current position to the target position (xR)
-xS), and xR is preset to the counter 9 from the controller 6 via the I/O port 200. Also, xR-xS is sent to register 10,
It is stored in synchronization with the clock signal 190 of the oscillator 19, and its output is sent to the I/O port 200 of the controller 6. Next, the pulse period detector is composed of a counter 16 and an oscillator 19. The counter 16 counts the clock signal 190 of the oscillator 19 and detects the pulse period of xP. Here, xP is used to set and reset counter 16. The detected pulse period is sent to register 17 and stored similarly to register 10. Its output is sent to the I/O port 200 of the controller 6.

Once every sample period, the controller 6
A series of processes for determining the operation signal (U) and a series of processes for determining the estimated speed value (v0) by the state observer (observer) 30 are performed. First, the process of determining the operation signal will be explained. xR-xS is read through the I/O port 200, and if xR-xS is larger than a predetermined value, a seek process 201 that causes the load 1 to reach the target position in a short time;
Perform step 202. In the seek process 201, the speed command value (vR
), vR is stored in memory (not shown) in advance as a function of xR-xS, and xR
-xS is read as the address. The subsequent process 202 is a process of comparing vR and v0 estimated by the observer 30 to determine an operation signal. In the subsequent switch processing 204, an operation signal is selected based on xR-xS. During the seek process, the output determined in the seek processes 201 and 202 is selected as the operation signal. After the seek process,
When xR-xS falls within a predetermined value, processing for positioning the load 1 to the target position is performed. In this case, switch processing 2
In step 04, an operation signal determined based on xR-xS is added in addition to the operation signal determined by the seek process.

Next, a series of processes related to the observer will be explained. First, via the I/O port 200,
The pulse period is read from the register 17, and the pulse period is converted into a detected speed value (vS) in a subsequent conversion process 300. Here, the reciprocal of the pulse period is calculated and a constant C2 is integrated. The constant C2 is a constant specific to the servo device and is stored in advance in a memory (not shown). In the subsequent adjustment process 301, the operation signal (U
) is performed. This is to correct the influence of external forces such as force acting on the actual device. The adjustment value is determined in adjustment processing 307. Subsequent calculation processing 302
is the process of calculating the acceleration of the observer, and the constant C1
is a constant unique to the servo device called mechanism gain. The values are previously stored in memory (not shown). The following adjustment process 303 is a process for adjusting the acceleration of the observer to match the actual device, and the adjustment value is determined in adjustment process 308. The subsequent speed estimation process 304 is a process for determining the estimated value (v0) of the speed, and an integral calculation is performed. The initial value at this time is zero. Continued comparison process 3
05 compares the velocity estimated by the observer (v0) and the actually detected velocity (vS), and calculates the error (v0-
vS). Subsequent adjustment processes 307 and 308 are processes for determining observer adjustment values,
The processing is executed based on the operation timing of the servo device. In FIG. 2, observer adjustment processing 307 and 3
An example of the timing for performing 08 is shown below. (a) shows each speed immediately after starting the load. vR is the speed command value, v is the load speed (which cannot actually be detected), v0
is the speed estimated by the observer, and vS is the detected speed value. When the load is in the acceleration process (same as in the deceleration process),
A relatively large detection error occurs in vS. This is due to the fact that the number of xPs generated by the pulse generator 3 is small and the pulse period is long. FIG. 2B shows the detection error of vS (v-vS), and it can be seen that the detection error decreases as the vehicle enters the constant speed region. The speed (v0) estimated by the observer is a value that approximates the speed (v) of the load, and the observer adjustment process is preferably performed in a state where the detection error (v-vS) of vS is zero or extremely small. For example, since the acceleration characteristics of the load can be predicted in advance, it is preferable to execute the observer adjustment process after a certain period of time T has elapsed after startup. Alternatively, the change state of vS may be checked and the observer adjustment process may be executed while the time change of vS is below a predetermined value (while in the constant speed region). A suitable operating state for adjusting the observer is an operating state in which the velocity detection error is zero or extremely small, and this corresponds to a state in which the acceleration change of the actual device is zero or extremely small. Therefore, the indicator for identifying this operating state may be a motor current or a motor operation signal related to acceleration. Alternatively, it may be a speed command value (vR) that commands the operating state of the device. Furthermore, the positional deviation (xR-xS) to the target position may be used to determine the speed command value.

In adjustment processing 307, an adjustment value is determined by multiplying v0-vS determined in comparison processing 305 by a constant K1. Before the first observer adjustment process is performed, zero is set as the adjustment value, but once the observer adjustment process is executed, the value is determined by the previous adjustment process until the next observer adjustment process is performed. The adjusted value is held and used. Here, the constant K1 is stored in advance in a memory (not shown). Further, in this embodiment, the observer adjustment process is executed after a certain period of time T has elapsed after starting the load. The subsequent adjustment process 308 is also performed in the same manner as the adjustment process 307. Here, the constant K2 is stored in advance in a memory (not shown).

In this embodiment, since the servo device is such that the acceleration characteristics of the load can be predicted in advance, the speed detection error (v
-vS) is extremely small. Therefore, the operating state is suitable for adjusting the observer, the observer can be adjusted with high accuracy, a highly accurate estimated value can be obtained, and the load can be positioned at the target position in a short time.

FIG. 3 is a block diagram showing another embodiment of the present invention. The embodiment shown in FIG. 1 differs in a part of the series of processing that determines the operation signal (U) in the controller 6,
Other configurations are the same. In this embodiment, a new switch process 220 is added in the process of determining the operation signal. This switch process 220 is a process of selecting and switching the speed feedback signal used for determining the operation signal from either v0 or vS based on the operating state of the servo device. In this embodiment, vS is selected in operating conditions where the speed is high and the detected speed value (vS) lags in phase, or the detection error is small and does not affect the characteristics of the servo device, and the phase lags behind vS during acceleration or deceleration. In operating conditions where detection errors occur, the observer's estimated value (v0) is selected. Further, as an index for identifying the operating state, the index used in the embodiment of FIG. 1 can be used. For example, the operating state of the device may be determined from the speed command value (vR) and the speed feedback signals v0 and vS may be switched. In this example, in addition to the observer's estimated value (v0),
Since the detection value (vS) in the actual device is also used, the reliability of the servo device is improved.

Furthermore, if the switching process 220 is performed in stages, the switching of the speed feedback signal can be performed smoothly, which has the effect of further stabilizing the servo device. For example, smoother switching can be realized by using elapsed time as an index of the weighting function to switch in stages. Number 1 is an example.

[0014]

[Math 1]

[0015]

According to the present invention, since the operating state of the servo device in which the speed can be detected more accurately is selected, and the speed is detected and the observer is adjusted, the observer can be adjusted correctly. Furthermore, since the system determines the operation signal for the servo device using both the estimated value and the detected value of the observer, the reliability of the servo device is improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a timing chart of observer adjustment processing.

FIG. 3 is a block diagram of another embodiment of the invention.

[Explanation of symbols]

1... Load, 2... Motor, 3... Pulse generator, 4... Power amplifier, 5... D/A converter, 6... Controller, 9... Counter, 10... Register, 16... Counter, 17... Register, 19... Transmission instrument, 30...observer, 200...I/O
port.

Claims (1)

[Claims] 1. A motor for driving a load, a pulse generator for detecting the amount of movement of the load or the motor, a state observation device for estimating the speed of the load or the motor, and positioning the load at a target position. In the servo device, the servo apparatus includes a control means for generating a motor operation signal for the control means, based on the calculated value in the control means, an operating state in which the change in acceleration of the load or the motor is less than a predetermined value is identified, and the state observation is performed. 1. A control method for a servo device, characterized in that the previously executed adjustment value is used in a state other than the operating state.