JP2003324983A - Servo amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a servo amplifier wherein noise components are removed from analog signals from a current sensor and a servo motor can be controlled with accuracy. <P>SOLUTION: The servo amplifier comprises the current sensor 13 which senses a current outputted to the servo motor 18 and converts the current into an analog signal, the channel 1 of a first A-D converter 12 which converts analog signals into digital signals, a noise sensing circuit which sense noise components superposed on a first signal line 15 connecting the current sensor 13 and the channel 1 of the first A-D converter 12 (The noise sensing circuit is composed of a constant voltage circuit 14, the channel 2 of the first A-D converter 12; and a second signal line 16 connecting the constant voltage circuit and the channel 2), and CPU 11 which processes digital signals. A digital signal obtained by converting the current of the current sensor 13 from analog to digital and an output signal from the noise sensing circuit are inputted to the CPU 11 and processed there. Thus, digital data with noise superposed on the current sensor removed is obtained. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo motor
The present invention relates to a circuit for removing a noise component superimposed on an analog output signal of a current sensor in a servo amplifier driven by WM.

[0002]

2. Description of the Related Art Conventionally, when removing noise from an analog signal, a noise filter consisting of a resistor and a capacitor for removing the noise is attached to an analog signal line, and noise in a frequency band peculiar to this noise filter is removed. / D
Converted to digital signal by converter.

[0003]

However, when a noise filter consisting of a resistor and a capacitor is installed, the frequency band that can be removed is limited due to the characteristics of the noise filter, and noise components that do not comply with it are rejected by the noise filter. However, there is a problem that even the noise components that have passed through and are input to the A / D converter are digitally converted, which adversely affects the PWM drive of the servo motor.

Further, when a plurality of analog signals are handled, the same number of noise filters as the number of signals is required, and there is a problem that the number of parts constituting the noise removing circuit increases.

The present invention solves such a conventional problem, and provides a servo amplifier capable of accurately controlling a servo motor by removing a noise component from an analog signal of a current sensor with a simple structure. With the goal.

[0006]

In order to solve the above problems, the present invention provides a current sensor for sensing a current output to a servomotor and converting it into an analog signal, and an analog signal of the current sensor into a digital signal. First A / D to convert
A converter, a first signal line that connects the current sensor and the first A / D converter, a noise sensing circuit that senses a noise component superimposed on the first signal line, and a digital signal is processed. And a first A /
The digital signal of the D converter and the digital signal of the noise sensing circuit are input to the CPU for arithmetic processing to remove superimposed noise.

[0007]

In order to solve the above-mentioned problems, an invention according to claim 1 is a current sensor for sensing a current output to a servo motor and converting it into an analog signal in a servo amplifier for PWM driving the servo motor. And a first A for converting an analog signal of the current sensor into a digital signal
/ D converter, a first signal line connecting the current sensor and the first A / D converter, a noise sensing circuit for sensing a noise component superimposed on the first signal line, and calculating a digital signal A current for outputting to the servo motor, which is provided with a CPU for processing, inputs the digital signal of the first A / D converter and the digital signal of the noise sensing circuit to the CPU for arithmetic processing to remove superimposed noise. The amount can be detected with high accuracy.

According to a second aspect of the invention, the noise sensing circuit has a constant voltage circuit for generating a constant voltage and a second A / A circuit for converting the output voltage of the constant voltage circuit into a digital signal.
A D converter and a second signal line connecting the constant voltage circuit and the second A / D converter are provided, and the second signal line is arranged right next to the first signal line. Since the noise superimposed on the signal line is superimposed on the second signal line and input to the CPU, the superimposed noise can be removed.

The invention according to claim 3 is the first A /
The timing of converting into a digital signal by the D converter and the timing of converting into a digital signal by the second A / D converter are input to the CPU in synchronism with each other. Data shift due to discretization of time when converting into a digital signal And the noise component can be correctly removed from the signal of the current sensor.

According to the present invention, the first signal line and the second signal line have the same length so that the first signal line serves as an antenna and a specific frequency component is superimposed as noise. However, since the noise component due to the length of the wiring is similarly applied to both signal lines, the noise removal accuracy can be improved.

According to a fifth aspect of the present invention, the current sensor and the first A / D converter are arranged on the same substrate, and the first signal line is arranged on the printed circuit board in a parallel pattern. Since the noise component due to the positioning of the wiring is applied to both wirings in the same manner, the noise removal accuracy can be improved.

According to the invention of claim 6, the first signal line and the second signal line are composed of electric wires, and the electric wires are coaxial cables or parallel wires, and the electric wires can be separated. The noise removal accuracy can be improved.

According to a seventh aspect of the present invention, a plurality of current sensors are provided, each current sensor is provided with a first A / D converter and a first signal line, and a noise sensing circuit is shared. By using a plurality of current sensors, it is possible to increase the accuracy of detection of the amount of current output to the servo motor and reduce the size of a plurality of noise removal circuits.

Further, according to the present invention, a plurality of A / D converters are built in the CPU, and the output signal of the current sensor and the output signal of the constant voltage circuit are supplied to the first signal line and the second signal line. First A / D built in the CPU via
Since it is input to the converter and the second A / D converter, the noise removing circuit and the servo amplifier can be downsized.

[0015]

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

(Embodiment 1) In FIG. 1, 11 is a CP
U and 12 are 2-channel A / D converters, and channel 1 is used as a first A / D converter and channel 2 is used as a second A / D converter. Reference numeral 13 is a current sensor, 14 is a constant voltage circuit, 15 is a first signal line, 16 is a second signal line, 17 is a servo amplifier, and 18 is a servo motor.

The analog signal of the current detected by the current sensor 13 is sent to the A / D converter 12 via the first signal line 15.
Input signal to channel 1 and output signal (digital signal)
Is input to the CPU 11. Servo motor switching noise is superimposed on this current signal (analog signal), and when this is digitally converted, digital data in which a noise component is added to the current detection signal of the current sensor 13 is generated.

On the other hand, the noise sensing circuit is the constant voltage circuit 1
4, the second signal line 16 and the channel 2 of the A / D converter 12, and the output signal (digital signal) of the channel 2 of the A / D converter 12 is input to the CPU 11. The constant voltage circuit 14 is arranged in the vicinity of the current sensor 13, and the first signal line 15 and the second signal line 16 are arranged in parallel. Due to this, the same switching noise as that of the first signal line 15 is applied to the second signal line 16, and when digitally converted, digital data having only a noise component is generated.

Then, when the digital data added with the noise component output from the channel 1 and the digital data containing only the noise component output from the channel 2 are input to the CPU 11 and subjected to arithmetic processing, noise superimposed on the current sensor is removed. Digital data can be obtained.

In this digital data generation process, A
By synchronizing the timing of converting the digital signals of the channel 1 and the channel 2 of the / D converter 12, noise can be reliably removed by the arithmetic processing of the CPU.

When the current sensor and the first A / D converter are arranged on the same printed circuit board, the first and second signal lines are printed wiring (copper foil pattern),
By arranging them in close proximity and in parallel, the influence of noise caused by the length and positioning of the signal line can be made equal, and the noise component of the first signal line and the noise component of the second signal line can be made the same. Therefore, noise can be reliably removed.

(Embodiment 2) Embodiment 2 is a current sensor and a first
The A / D converter is suitable for mounting on another printed circuit board, and coaxial cables are used for the first and second signal lines.

In FIG. 2, 21 is a CPU, 22 is a 2-channel A / D converter, and channel 1 is used as a first A / D converter and channel 2 is used as a second A / D converter. Reference numeral 23 is a current sensor, 24 is a constant voltage circuit, and 25 is a coaxial cable, which includes a first signal line and a second signal line. 27 is a servo amplifier, 2
Reference numeral 8 is a servo motor.

The procedure is the same as that of the first embodiment except that the coaxial cable 25 is used for the first signal line and the second signal line, and the description of noise removal is omitted.

Since the coaxial cable is used for the signal line, it is less affected by noise other than the switching current of the servo motor as compared with the first embodiment.

Incidentally, instead of the coaxial cable, a parallel wire in which a plurality of electric wires are closely adhered in parallel may be used, and the cost can be reduced.

(Third Embodiment) In the third embodiment, the CPU has a plurality of A's.
It has a built-in / D converter.

In FIG. 3, reference numeral 31 is a CPU which has a built-in 2-channel A / D converter. Channel 1 is the first A / D converter and channel 2 is the second A / D converter.
Used as a D converter. 33 is a current sensor, 34 is a constant voltage circuit, 35 is a first signal line, 36 is a second signal line, 37 is a servo amplifier, and 38 is a servo motor.

The difference from the first embodiment is that a plurality of A
The point is that the / D converter is built in. Therefore, the first and second signal lines are connected to the first and second A / D converters of the CPU 31. The noise removal is the same as in the first embodiment, and will not be repeated.

(Embodiment 4) In Embodiment 4, two current sensors are provided, and the current is detected in two of the three phases of the servomotor, and the remaining one phase is detected in the same manner as in the prior art. The two phases are calculated and estimated.

In FIG. 4, 41 is a CPU, 42 is a 3-channel A / D converter, and channels 1 and 2 are used as a first A / D converter and channel 3 is used as a second A / D converter. 43 and 49 are current sensors, 44 is a constant voltage circuit, 45 and 50 are first signal lines, 46 is a second signal line, 47 is a servo amplifier, and 48 is a servo motor.

The difference from the first embodiment is that two current sensors 43 and 49 are used, the number of A / D converters and the number of CPU inputs. There is one constant voltage circuit 44,
It is placed near one of the current sensors.

The first signal line 45 connected to the current sensor 43 and the first signal line 5 connected to the current sensor 49
0, the same switching noise is applied to the second signal line 46 connected to the constant voltage circuit 44. Then, the digital data A / D-converted via the first signal line 45 and the first signal line 50 is digital data of current information to which a noise component is added, and is generated via the second signal line 46. Digital data having only a noise component is generated in the A / D converted digital data.

By inputting these digital data into the CPU 41 and processing them, data for two phases obtained by digitally converting the analog signal from which the noise component applied to the current sensor is removed can be obtained.

In the digital data generation process,
The first embodiment synchronizes the timing of conversion into digital signals of channels 1, 2, and 3 of the A / D converter 42.
Is the same as. Further, the first signal lines 45 and 49 and the second signal line may be printed wirings laid out in parallel in the vicinity, coaxial cables or parallel lines.

Furthermore, Embodiments 1 to 4 can be implemented by combining them, and can be implemented similarly even if the current sensors for three phases are used.

[0037]

As is apparent from the above embodiments, according to the inventions of claims 1 and 2, a noise sensing circuit for positively sensing a noise component is provided, and noise is detected by using the sensed information signal. Can be removed.

According to the third, fourth, fifth and sixth aspects of the present invention, noise can be removed more reliably.

According to the invention of claim 7, the CP
By incorporating the A / D converter function in U, the noise removing circuit can be downsized.

Further, according to the eighth aspect of the present invention, even when a plurality of current sensors are used, one noise sensing circuit can remove the noise component from the analog signal of the current sensor, and the servo motor can be controlled accurately. You can get an amplifier.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of noise removal according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of noise removal according to the second embodiment of the present invention.

FIG. 3 is an explanatory diagram of noise removal according to the third embodiment of the present invention.

FIG. 4 is an explanatory diagram of noise removal according to the fourth embodiment of the present invention.

[Explanation of symbols]

11,21,31,41 CPU 12,22,42 A / D converter 13,23,33,43,49 Current sensor 14, 24, 34, 44 constant voltage circuit 15, 35, 45, 50 First signal line 16, 36, 46 Second signal line 17, 27, 37, 47 Servo amplifier 18, 28, 38, 48 Servo motor 25 coaxial cable (or parallel wire)

Claims (8)

[Claims] 1. In a servo amplifier for PWM driving a servo motor, a current sensor for sensing a current output to the servo motor and converting it into an analog signal, and a first A for converting an analog signal of the current sensor into a digital signal. / D
A converter, a first signal line that connects the current sensor and the first A / D converter, a noise sensing circuit that senses a noise component superimposed on the first signal line, and a digital signal is processed. And a first A /
A servo amplifier characterized in that a digital signal of a D converter and a digital signal of a noise sensing circuit are input to a CPU for arithmetic processing to remove superimposed noise. 2. The noise sensing circuit includes a constant voltage circuit for generating a constant voltage, a second A / D converter for converting an output voltage of the constant voltage circuit into a digital signal, the constant voltage circuit and the second voltage converter. A second signal line for connecting to the A / D converter, the second signal line is arranged right next to the first signal line, and noise superimposed on the first signal line is applied to the second signal line. The servo amplifier according to claim 1, wherein the servo amplifier is superposed on the CPU and input to the CPU. 3. The timing of converting into a digital signal by the first A / D converter and the timing of converting into a digital signal by the second A / D converter are synchronized to C
The servo amplifier according to claim 2, wherein the servo amplifier is input to the PU. 4. The servo amplifier according to claim 2, wherein the first signal line and the second signal line have the same length to superimpose a frequency component specific to the first signal line as an antenna as noise. 5. The current sensor and the first A / D converter are arranged on the same substrate, and the first signal line is arranged in a parallel pattern on the printed circuit board.
The listed servo amplifier. 6. The servo amplifier according to claim 2, wherein the first signal line and the second signal line are composed of electric wires, and the electric wires are coaxial cables or parallel wires. 7. A plurality of current sensors are provided, and a first A / D converter and a first signal line are provided for each current sensor,
The servo amplifier according to claim 1, which shares a noise sensing circuit. 8. A plurality of A / D converters are built in a CPU, and the output signal of the current sensor and the output signal of the constant voltage circuit are sent to the CPU via a first signal line and a second signal line.
First A / D converter and second A / D built in
The servo amplifier according to any one of claims 2 to 7, which is input to a converter.