JP2000217395A - Actuator control device - Google Patents

Abstract

(57) [PROBLEMS] To use a device using a PWM control type actuator in the vicinity of a device using radio waves such as a radio or a television, and to control the frequency of the PWM control of the actuator by monitoring the radio or the TV. Make noise generated by affecting the frequency band inconspicuous. SOLUTION: By changing the frequency of the PWM control aperiodically, the time required for an integer multiple of the frequency of the PWM control in the monitor frequency band becomes aperiodic in a short time, and noise becomes less noticeable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator control device for controlling an actuator by a PWM-controlled current.

[0002]

2. Description of the Related Art PWM control is a method in which a current is provided with a cycle and the ratio of the time during which the current flows and the time during which no current flows within the cycle is changed. The actuator is controlled by using the PWM control. There is a method. The cycle at this time is the frequency of the PWM control, and is usually a high frequency of about several tens kHz.

[0003] The PWM control type actuator consumes less power and generates less heat than an analog control type in which a transistor or the like is used as a variable resistor to directly control the magnitude of current flowing through the actuator to control the actuator. It has the advantage of being small. Therefore, in recent years, it has been used for controlling various devices.

However, when a device using the actuator of the PWM control method is used in the vicinity of a device using radio waves such as a radio or a television, the high frequency of the PWM control of the actuator uses the radio waves of the radio or the TV. It may affect the frequency band (monitor frequency band) monitored by the device, and may cause noise on the radio or television.
Here, it is known that the high frequency of the PWM control of the actuator easily affects the frequency band of an integral multiple thereof as noise. In other words, even if the frequency of the PWM control is lower than the monitor frequency band, if the integer multiple of the frequency is in the monitor frequency band, it is likely to be the noise of the radio or television.

In order to prevent this noise, it is theoretically necessary to set the control frequency of the actuator higher than the monitor frequency band. However, the frequency band of radio and television is several hundreds kHz to several tens MHz or more. On the other hand, the frequency that the actuator driver that controls the actuator by PWM control can handle is usually several tens kHz.
In practice, it is difficult to make the frequency of the PWM control higher than the monitor frequency band.

Therefore, in order to prevent noise from the radio or television, for example, as disclosed in Japanese Patent Laid-Open No. 7-99795, the frequency of PWM control is periodically changed. Here, the situation when the frequency of the PWM control is periodically changed will be described with reference to the graph of FIG.

In the graph of FIG. 3, the vertical axis indicates frequency, and the horizontal axis indicates the passage of time. A broken line indicates a transition of an integer multiple of the frequency of the PWM control when the frequency of the PWM control is periodically changed. Here, for example, the frequency of the PWM control is 35 kHz ± 10 kHz. The shaded horizontal band is a monitor frequency band for a radio or a television, for example, about 700 kHz here.
If this portion overlaps with an integer multiple (here, for example, 20 times) of the frequency of the PWM control, noise is likely to be generated on the radio, television, or the like.

In the prior art, an integer multiple of the frequency of the PWM control is continuously applied to the monitor frequency band by periodically changing the frequency of the PWM control as shown by a broken line in FIG. Can be prevented, but since an integer multiple of the frequency of the PWM control is periodically applied to the monitor frequency band, noise is periodically generated, and the radio and television viewers are worried about the noise. There was a problem that it was easy.

[0009]

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, the present invention has a problem that noise is generated when a device using a PWM control type actuator is used near a device using radio waves such as a radio or a television. The purpose is to prevent it from being noticeable.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an actuator controlled by a current and a control of a current supplied to the actuator by PWM.
In an actuator control device including an actuator control unit that performs control, the frequency of the PWM control of the actuator control unit is changed aperiodically.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows a hardware configuration of the present embodiment. Reference numeral 1 denotes a controller, which determines an aperiodic (random) frequency of current control, receives a sensor signal from an externally provided sensor 5, and receives a duty ratio corresponding to a control position of the actuator 4 ( In one cycle of the random frequency, a ratio of a time during which a current flows to the transistor 3 to a time during which no current flows is determined, and a PWM signal having the frequency and the duty ratio is determined by the I / F circuit 2.
Output to The I / F circuit 2 uses the P of the controller 1
Receiving the WM signal, the PW of the current corresponding to transistor 3
Output M signal. The transistor 3 receives the PWM signal of the I / F circuit 2 and turns on / off a current flowing from the power supply to the actuator 4 according to the PWM signal. As a result, the actuator 4 is driven. When the controller 1 can output a current of a level corresponding to the transistor 3, the I / F circuit 2 is unnecessary.

FIG. 2 shows a control flow in the controller 1 for explanation. First, the controller 1 performs an initial setting (S1). Next, it is determined whether or not a predetermined control cycle has been reached (S2). If the control cycle has not been reached, the same determination is performed again. If the control cycle has been reached, a determination based on a sensor signal from the sensor 5 is performed. To determine the duty ratio of the command signal (S3). Next, the frequency of the PWM control is determined non-periodically (randomly) (S4), and a PWM signal is output to the I / F circuit 2 based on the results of S3 and S4 (S4).
5). As a result, the I / F circuit 2 outputs a PWM signal of a current level corresponding to the transistor 3, and the actuator 4 is driven.

Here, the predetermined control cycle is set to a sufficiently long cycle so as not to affect the PWM control. For example, in the control of a semi-active suspension of an automobile, the predetermined control cycle is 10 msec.
It is about.

Next, the operation of this embodiment will be described with reference to FIG. The frequency of the PWM control is, for example, 35 kHz ± 1
The frequency is controlled to change randomly within the range of 0 kHz, and the integral multiple of the frequency changes irregularly as shown by the thick solid line in the graph of FIG. Therefore, the overlap (T random) with the shaded horizontal band portion of the graph which is the monitor frequency band (here, for example, about 700 kHz) of the radio or television of the integral multiple (here, for example, 20 times) is aperiodic. Become. Therefore, the noise of the radio or the television is generated in a very short time and aperiodically, and the noise can be made less noticeable to the viewer of the radio or the television than in the related art.

In this embodiment, the configuration of the hardware is as shown in FIG. 1. However, the present invention is not limited to this. For example, another configuration that can realize the effects of the present invention, such as using an IC circuit, is used. May be.

In this embodiment, the range in which the frequency of the PWM control changes is within the range of 35 kHz ± 10 kHz. However, the present invention is not limited to this, and other ranges may be used as long as the frequency band can be handled by the actuator.

In this embodiment, the frequency is randomly switched for each control cycle. Alternatively, in a long control cycle, a PWM signal having a random frequency is always transmitted from a PWM source. You may put out.

[0019]

As described above, according to the present invention, in the actuator control device comprising the actuator controlled by the current and the actuator control means for controlling the current supplied to the actuator by the PWM control, By changing the frequency of the PWM control of the control means aperiodically, the noise generated when the device using the actuator control device is used in the vicinity of a device using radio waves such as a radio or a television can be reduced in a short time. Since it appears aperiodically, it is possible to prevent noise from being noticeable to a person who watches the radio or television. According to the present invention, no special circuit for noise suppression is required in the actuator drive circuit.

[0020]

[Brief description of the drawings]

FIG. 1 is a hardware configuration of an actuator control device according to the present invention.

FIG. 2 is a control flowchart of a controller of the actuator control device of the present invention.

FIG. 3 shows an example of PWM frequency control of a conventional actuator control device and PWM of an actuator control device of the present invention.
9 is a graph illustrating an example of M frequency control.

[Explanation of symbols]

 1 controller 2 I / F circuit 3 transistor 4 actuator 5 sensor

Claims (1)

[Claims] 1. An actuator control apparatus comprising: an actuator controlled by a current; and actuator control means for controlling a current supplied to the actuator by PWM control, wherein the frequency of the PWM control of the actuator control means is aperiodic. An actuator control device, characterized in that: