JPH01295688A - Speed control apparatus - Google Patents

Abstract

PURPOSE:To reduce rotational unevenness by computing a speed error and multiplying said error by a gain to obtain a drive signal for driver and by detecting harmonic components included in two or more past detected speeds and the like. CONSTITUTION:A speed control apparatus C is equipped with a motor M for moving body, a pole position detector PS for detecting the rotor position of said motor, and a speed detector FG; and its principal part is composed of a microcomputer MC, an automatic current regulator circuit ARC, a driver(inverter) INV, and a speed detector circuit COUNT. Said apparatus is further provided with a harmonic component detector means. Said detector means computes arbitrary frequency(harmonic) components inherent in detected speeds from two or more past detected speed values and more subtracts said computed frequency components from said detected speeds to remove arbitrary frequencies. Thus, it is possible to remove, for example, frequency components of an error included in FG.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a speed control device for a moving body, and in particular, it is possible to reduce rotational unevenness even if a speed detection means has a detection error component of a constant harmonic component. The present invention relates to a speed control device for a moving object.

[Conventional technology]

It is desired that the speed of a drive motor for a VTR (video tape recorder) be constant. If there is speed fluctuation (uneven rotation, speed ripple, torque ripple), the image will be distorted and the reliability of the VTR will be affected.

Dignity will be severely damaged.

In order to keep the speed constant, a highly accurate speed sensor is required. For example, a sensor based on a rotating magnet and an FG pattern is used as a speed sensor for a cylinder motor of a VTR. This method has high accuracy because it is configured as an all-round integral type, but due to installation accuracy errors, I P P R (Pul
(se Per Revolution) component error is included in the sensor.

[Problem to be solved by the invention] If the sensor contains an error as described above and the control is high-performance, the apparent speed detected by the speed sensor will be constant, but the actual speed will vary. There is a drawback that rotational unevenness is included due to the error of the sensor.6 An object of the present invention is to eliminate rotational unevenness due to an error included in a motor speed sensor, etc.

[Means to solve the problem]

The above purpose is to provide a speed control device that includes a driver (INV) that applies a current or voltage of a magnitude according to a command speed and a speed detection signal, and a speed detection circuit (INV) that detects the speed from the signal from the speed detection element. COUNT) and a microcomputer (MC) that drives the driver by comparing the commanded speed and the detected speed.The microcomputer calculates a speed error, which is the difference between the commanded speed and the detected speed, and A calculation means for multiplying a gain to obtain a drive signal for the driver, and a harmonic component detection means for detecting a harmonic component included in at least two or more past detected speeds, current commands, and speed errors. This can be achieved by providing a means for reducing the above-mentioned harmonic components included in the current command, etc.

[Effect]

By reducing the harmonic components contained in the speed error, detected speed, current command, etc., the control device no longer responds to the error contained in the speed sensor. Therefore, the error of the speed sensor is removed, and rotational unevenness is reduced. can provide a small motor.

〔Example〕

Examples of the present invention will be described below.

FIG. 1 shows a speed control device according to an embodiment of the present invention in which the movable body is a brushless motor.

M is a motor serving as a moving body, which may be either a rotating type or a linear type, and may or may not have a brush.

PS is a magnetic pole position detector that detects the position of the motor M, especially the rotor, and is used to switch the phase current of the motor M. Although the internal structure of the motor is not shown, brushless motors electronically detect the position of the rotor.
It is usually configured to allow the Wl flow to flow through two phase windings selected depending on the position of the rotor. FG is a speed detector attached to the rotating shaft of the motor M. Depending on the accuracy of the FG installation, errors in higher harmonics due to the influence of leakage magnetic fields from the outside of PPR1 are included as described above.

INV is an inverter that is a driver that drives a motor, and usually consists of 6 switching elements to form 3 positive and 3 negative arms, allowing current to flow through two selected phase windings, and changing the size of the windings. It is something that can be done. ACR is an automatic voltage regulation circuit (Automatic Current
The regulator is configured to receive a current detection value obtained from a current transformer (CT). MC is a microcomputer with the functions described later, C0UN.
T is a speed detection circuit, which is actually composed of a counter, and speed detection is performed by detecting the number of pulses detected at a fixed sampling time or the interval of FG pulses. The main parts of the speed detection device C include the above-mentioned microcomputer MC1 automatic current adjustment circuit ACR, driver (inverter) INV, and speed detection circuit C0UNT. Then, the number of pulses obtained by the speed detection circuit C0UNT and the pulse interval of FG are transmitted to the microcomputer, and the signal from the magnetic pole position detector PS is also transmitted to the microcomputer MC and the driver. The microcomputer MC calculates the information from the speed detection circuit into a detected speed, and further calculates the command speed from the speed command signal (not shown) to control on/off and current of the switching element of the driver. Functions to adjust the magnitude of the value.

FIG. 2 is a concrete block diagram of the speed control device. In this figure, the speed detection signal is detected by counting the number of pulses of a reference oscillator (clock or counter) that falls between the pulses of the speed detector FG, and the signal n obtained thereby is It is converted into a detected speed Nt using a processing method. Furthermore, a speed error NE is calculated from the difference between the commanded speed NF and the detected speed N1, and a new current command Is is output after proportional and integral control (PI control) processing. The current control system consists of hardware,
Current command Is and current detection value obtained from current transformer CT 1. The current error Ie is calculated from z, and the current is applied to the motor M via the automatic current adjustment circuit ACR. Note that the inverter is omitted in FIG. 2.

The overall configuration of these components is almost the same as that conventionally known, but the present invention is based on a novel harmonic component detection means 10 (normally 10A or one IOB) shown in a broken line frame in FIG. ).

In other words, any same wave number (harmonic) inherent in the detection speed N,
By calculating the component from at least two or more past detected speed values, and then subtracting the frequency component calculated above from the detected speed, any frequency (for example, FG error frequency) can be calculated from among the detected speeds. can be removed. This makes it possible to remove, for example, error frequency components contained within the FG. The same thing can be achieved with the current command IS shown in FIG. 2, and the same thing can be achieved with the speed error NE.

Figure 3 shows the operation. Figure 3 (a) shows the FG pulse period n per rotation observed in the speed detection circuit C0UNT when operating with the gain K of the speed control system selected relatively small.
f(θ) is shown. The detected speed Nf is calculated as /nf(θ) in the microcomputer from the above signal.

The rotational unevenness component of this detected speed Nf(θ) is shown in Fig. 3(b).
Shown below.

Here, rotation unevenness is caused by sensor installation accuracy.
6PPR due to torque ripple generated by the PPR component itself
An example in which the component exists is shown.

When the gain of the speed control system is increased, the detected speed changes to IPPR as shown in FIG. 3(c).

The rotational irregularities of the 6PPR components become smaller, especially the I P
PR becomes smaller. However, since the I PPR component is a sensor error component, the actual motor speed includes the I PPR component as shown in FIG. 3(d).

Therefore, if the I PPR component is not influenced by other factors of the motor (for example, it is well balanced and the drive torque ripple is small), the I PPR component in the detected speed shown in Figure 2 (c) will be By doing so, it is possible to remove the error in the IPPR of the sensor while keeping the 6PPR component sufficiently small. In other words, it is possible to reduce the rotational unevenness of the actual speed, rather than the rotational unevenness observed in the FG.

It is clear that the sensor error can also be reduced by performing similar operations on the current command and speed error. In other words, in the case of the embodiment, if any one of the detected speed, current command, and speed error in the loop of the speed control system does not respond or is not sensed by the IPPRPPR component contained in the sensor, the IPPR errors can be removed.

Next, the function of the frequency detection 10 will be explained.

Generally, the velocity Nf(θ) can be expanded into each frequency component according to the following equation.

However, no: DC component an: Coefficient of sine bn Coefficient of two cosines And the absolute value of noHanlbn for any frequency component is expressed by the following equation.

The third method uses an FG that generates n pulses per revolution.
In the example shown in the figure, the frequency (frequency component) of nxPPR per rotation is determined by the following equation.

However, for N...the number of pulses per rotation N f n :
Speed of the n-th pulse In general, the DC component can be ignored, and the magnitude N of the frequency component (harmonic component) is determined by the following equation.

By subtracting the magnitude of the above frequency components from the original signal as shown in the block diagram of FIG. 2, the error harmonics of the speed sensor can be removed from the speed ripple.

FIG. 4 shows a flowchart of the microcomputer according to the present invention. An example in which an IPPR component is included as a speed sensor error will be shown. It is assumed that the speed control is performed by the pulse component of the FG. First, in step 2, the speed command is taken in, and in step 2, the detected speed is calculated from the period of the FG. ■ is I for each FG
This is to find the sine term coefficient and cosine term coefficient of the PPR component. ■ is used to check whether the calculation shown in ■ has been performed for one rotation, and a counter is used. When one rotation is completed, ANI (n) and BNI (n) are registered. The registered value is used to calculate the frequency component N in step (3). In (2), only the harmonic components caused by the sensor are removed from the detected speed NF. (2) and (2) are general speed control calculations in which the speed error NE and proportional term (including integral and differential terms in some cases) are calculated.

The above calculation removes rotational unevenness components caused by errors in the speed sensor and the like.

Regarding the above, countermeasures against speed sensor errors have been described. In addition, external noise (50Hz or 10Hz)
Even if noise such as power supply noise (0HX power supply noise, etc.) is included in the speed control loop and has an adverse effect, the same method can be used as a countermeasure. However, in this case, it is not necessary to correct the harmonic components for one rotation position, but to make similar corrections for the time harmonics (frequency components). In other words, if the noise component is 50 Hz, it is necessary to calculate the 50 Hz component included in the speed control loop and perform similar correction for this component.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a speed control device that eliminates rotational irregularities and vibrations caused by errors caused by mounting of a speed sensor, etc., and resonance of external noise systems.

[Brief explanation of the drawing]

FIG. 1 is a block diagram according to the present invention, FIG. 2 is a control block diagram thereof, FIG. 3 is an explanatory diagram of the operation of the present invention, and FIG. 4 is a diagram showing an operating program of the microcomputer of the present invention. M...Motor, ps...Magnetic pole position detector, FG...
・Speed sensor, C0UNT...Speed detection circuit, MC・
...Microcomputer, ACR...Automatic current adjustment circuit, C...Control circuit, INV...Driver, IS
...Current command, 10...Frequency detection. Figure 1 C, MC Figure 2 OA Kasumi 3I2I 4th-

Claims (1)

[Claims] 1. The relationship between a moving object, a speed detection element that detects the moving speed of the moving object, a speed detection signal obtained from this speed detection element, and a speed command signal given from the outside is more appropriate. The speed control device includes a driver (INV) that applies a current or voltage of a magnitude according to the command speed and the speed detection signal. , a speed detection circuit (COUNT
) and a microcomputer that drives the driver (INV) by comparing the command speed obtained from the speed command signal and the detected speed calculated based on the speed signal obtained from the speed detection circuit (COUNT). (MC), and the microcomputer calculates a speed error that is the difference between the commanded speed and the detected speed, and multiplies the speed error by a gain to obtain a drive signal for the driver (INV). and means for detecting harmonic components included in the detected speed, speed error, current command, etc. from at least two or more past detected speeds, speed errors, current commands, etc., the detected speed,
A speed control device comprising means for reducing the detected harmonic components contained in speed errors, current commands, etc. 2. A speed control device, wherein the moving body according to claim 1 is a motor that rotates or moves linearly. 3. In claim 1, the cycle of speed control in which a current or voltage of a magnitude according to the command speed and the speed detection signal is applied to the driver is defined as the detected speed, speed error,
A speed control device characterized in that the period is shorter than the period for detecting harmonic components included in a current command.