JPH0950335A - Transmission interface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission interface which can stably drive a larger number line receivers item before via a single line driver and also can cut noises. SOLUTION: An input circuit in the transmission interface includes a line driver 2, output terminals A and B, communication lines 31 and 32 which are connected between the input terminals A1 to An and B1 to Bn of the servo amplifiers 41 to 4n respectively, and input circuits 81 to 8n and 91 to 9n which are placed among the terminals A1 to An and B1 to Bn of the amplifiers 41 to 4n and two input terminals of the line receivers 71 to 7n. Each of circuits 81 to 8n and 91 to 9n contains the inductances L1 and L2 which are connected in series to each other and a capacitance C1 which is placed between a point (a) and the ground.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission interface for connecting, for example, a plurality of industrial robots and a personal computer (hereinafter referred to as a personal computer) that controls the industrial robots.

[0002]

2. Description of the Related Art In recent years, along with factory automation, a method has been adopted in which a plurality of industrial robots are controlled by a single personal computer in a factory, for example, via an RS422 standard transmission interface. ing.

FIG. 4 is a block diagram showing the configuration of a personal computer and a robot connected by a conventional transmission interface. In the figure, reference numeral 1 is a personal computer that controls a motor (not shown) of robots 101 to 10n described later, and generates a control signal S1. Reference numeral 2 is a line driver (for example, RS422 standard) for transmitting the control signal S1 generated by the personal computer 1. When the control data S1 is "1", the line driver 2 applies a negative voltage (for example, -5V) to the output terminal A and a positive voltage (+ 5V) to the output terminal B, and controls data When S1 is "0", a positive voltage (+
5V) and a negative voltage (-5V) are applied to the output terminal B, respectively. Communication lines 31 and 32 are connected between the output terminals A and B and the input terminals A1 to An and B1 to Bn of the servo amplifiers 41 to 4n, respectively, and transmit the control signal S1.

Reference numerals 41 to 4n are servo amplifiers for driving the respective motors of the robots 101 to 10n. 51 to 5n are
The input circuits are respectively inserted between the input terminals A1 to An of the servo amplifiers 41 to 4n and one input ends of line receivers 71 to 7n described later. The input circuits 51 to 5n are composed of resistors R and R connected in series, and an RC low pass filter composed of a capacitance C interposed between a point a shown in FIG. It serves to cut the noise induced on the lines 31 and 32. Reference numerals 61 to 6n are input circuits having the same configuration as the input circuits 51 to 5n, and input terminals B1 to Bn of the servo amplifiers 41 to 4n and the line receiver 7 are provided.
They are respectively inserted between the other input terminals 1 to 7n.

The line receivers 71 to 7n are built in the servo amplifiers 41 to 4n, respectively, and control signals S1 transmitted from the line driver 2 are transmitted to the communication lines 31 and 32 and the input circuits 51 to 5n and 61 to 6n. Control signal S received via
2 is output to the motors of the robots 101 to 10n. The servo amplifiers 41 to 4n output "1" when the voltage applied to one input end is smaller than the voltage applied to the other input end, and also to one input end. When the applied voltage is higher than the voltage applied to the other input terminal, "0" is output. RT is a terminating resistor connected between the input terminals An and Bn of the servo amplifier 4n.

[0006]

By the way, in the above-mentioned conventional transmission interface, the servo amplifier 4 is used.
As the number of 1 to 4n increases, the load seen from the line driver 2 increases. Therefore, there is a problem that the line driver 2 cannot be driven for the reason described below.

FIG. 5 shows a load viewed from the line driver 2 shown in FIG. 4, that is, an equivalent circuit of the input circuits 51 to 5n and 61 to 6n. In this figure, the resistors R, R, ... Shown in FIG. 4 are combined resistances R / n, R / n, and the capacitances C, C ,.
Each can be represented by C. In this figure, for example,
When the voltage V is applied to the communication line 31, a current i flows to the ground via the combined resistance R / n and the combined capacitance nC as shown in FIG. This current i is, as shown in FIG. 6, at time t = 0 (during the driving of the line driver 2 or the control signal S
It exhibits the characteristic of a transient phenomenon in a so-called RC series circuit in which it becomes maximum (i = nV / R) at the time of inversion of the logic of 1) and then decreases exponentially. On the other hand, communication line 32
When a voltage -V is applied to the same, a current i similarly flows from the ground to the communication line 32 through the combined capacitance nC and the combined resistance R / n. As described above, the line driver 2 instantaneously outputs the current i (nV / R) during driving or when the logic of the control signal S1 is inverted. The current i
Is proportional to the number n of servo amplifiers 41 to 4n,
When the number of units n exceeds a certain number, the current i changes to the line driver 2
Exceeds the rated output current value of, and the line driver 2 cannot be driven.

The present invention has been made under such a background, and a single line driver can stably drive a large number of line receivers as compared with the conventional one, and also generate noise. The purpose is to provide a transmission interface that can be cut.

[0009]

According to a first aspect of the present invention, a transmission interface connected between a computer for generating control signals for controlling a plurality of robots and the plurality of robots and transmitting the control signals. In the above, a line driver for transmitting the control signal, a plurality of line receivers respectively provided corresponding to the plurality of robots, connected in parallel to the line driver via a communication line, and receiving the control signal, It is characterized by comprising an LC low-pass filter circuit inserted between each input end of the plurality of line receivers and the communication line.

According to a second aspect of the present invention, in the transmission interface according to the first aspect, the LC low pass filter circuit includes two inductances connected in series, a connection point of the two inductances, and a ground. It is characterized in that it is composed of a capacitance interposed between and.

[0011]

According to the present invention, when the control signal is transmitted from the line driver, the control signal is input to each input circuit through the communication line. At this time, the current flowing through the input circuit has a characteristic that it is a transient phenomenon in the LC series circuit, that is, it gradually increases from zero, reaches a maximum value at a certain point, and then gradually decreases. Therefore, when viewed from the side of the line driver, the current that is instantaneously output is suppressed, so that the line driver can be stably driven even when a large number of line receivers are connected in parallel as compared with the conventional one. Further, the noise induced in the communication line is cut by the action of the LC low pass filter.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a personal computer and a robot connected by a transmission interface according to an embodiment of the present invention. In this figure, parts corresponding to respective parts in FIG.
The description is omitted. In this figure, instead of the input circuits 51-5n and 61-6n shown in FIG. 4, input circuits 81-8 are provided.
n, 91 to 9n are provided. The input circuits 81 to 8
Each of n and 91 to 9n is composed of an LC low-pass filter which includes inductances L1 and L2 in place of the resistors R and R shown in FIG. 4 and capacitance C1 in place of the capacitance C.

FIG. 2 is an equivalent circuit of the load, that is, the input circuits 81 to 8n and 91 to 9n as seen from the line driver 2 shown in FIG. 1, and the inductances L1, L1, ... Shown in FIG. The synthetic inductance L1 / n, the inductances L2, L2, ... Can be represented by the synthetic inductance L2 / n, and the capacitance C1 can be similarly represented by the synthetic capacitance nC1. In this figure, the line driver 2 is driven to apply a voltage V to the communication line 31.
Is applied, the current i flows to the ground through the combined inductance L1 / n and the combined capacitance nC1 as shown in FIG. As shown by the solid line in FIG. 3, this current i is at time t = 0 (during the driving of the line driver 2 or the control signal S
It is zero at the time of logic inversion 1), then gradually increases, reaches the maximum value (nV / L1) at time t1, and then gradually decreases after time t1, a so-called transient phenomenon in an LC series circuit. Shows the characteristics of. Further, as a matter of course, the input circuits 81 to 8n and 91 to 9n shown in FIG.
The noise induced in 1 and 32 is cut by the action of the LC low pass filter.

As described above, according to the transmission interface according to the embodiment of the present invention, when the line driver 2 is driven, as is apparent from the characteristics of the current i of the conventional transmission interface shown by the broken line in FIG. At time (t = 0), the current i has a characteristic of gradually rising, and the maximum value of the current i is the current i of the conventional transmission interface.
(See the broken line in FIG. 3). As a result, a single line driver 2 can drive a large number of servo amplifiers 41 to 4n (line receivers 71 to 7n) more stably than the conventional one.

[0015]

As described above, according to the present invention,
The current flowing through the input circuit becomes the characteristic of the transient phenomenon in the LC series circuit, and the current output instantaneously is suppressed from the viewpoint of the line driver side. Therefore, a large number of line receivers are connected in parallel as compared with the conventional transmission interface. However, the line driver can be driven stably, and the noise induced in the communication line can be cut.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a personal computer and a robot connected by a transmission interface according to an embodiment of the present invention.

2 is a diagram showing an equivalent circuit of input circuits 81 to 8n and 91 to 9n viewed from the line driver 2 shown in FIG.

3 is a current i in the equivalent circuits shown in FIGS. 2 and 5. FIG.
FIG. 6 is a diagram showing characteristics of the present invention.

FIG. 4 is a block diagram showing a configuration of a personal computer and a robot connected by a conventional transmission interface.

5 is a diagram showing an equivalent circuit of the input circuits 51 to 5n and 61 to 6n viewed from the line driver 2 shown in FIG.

6 is a diagram showing characteristics of a current i in the equivalent circuit shown in FIG.

[Explanation of symbols]

 1 PC 2 Line driver 31 and 32 Communication line 41 to 4n Servo amplifier 71 to 7n Line receiver 81 to 8n, 91 to 9n Input circuit 101 to 10n Robot L1, L2 Inductance C1 Capacitance S1, S2 Control signal

Claims (2)

[Claims] 1. A transmission interface that is connected between a computer that generates control signals for controlling a plurality of robots and the plurality of robots and that transmits the control signals, and a line driver that transmits the control signals, A plurality of line receivers provided corresponding to the plurality of robots, connected in parallel to the line driver via a communication line, and receiving the control signal; and input terminals of the plurality of line receivers and the communication line. And a LC low pass filter circuit interposed between the transmission interface and the LC low pass filter circuit. 2. The LC low pass filter circuit is composed of two inductances connected in series and a capacitance interposed between a connection point of the two inductances and ground. The transmission interface according to claim 1, wherein: