JPH04268897A - Analog multiplex transmission method - Google Patents

Abstract

PURPOSE:To supply a method transmitting control data to plural analog units which are scattered and arranged in a plant and the like by means of one transmission line. CONSTITUTION:Plural reception stations 6 having actuators are connected to one transmission line 5 connected to a transmission station 4 being a main station. A peak value transmits a power source pulse A higher than a data pulse for data transmission B from the transmission station 4 to the transmission line 5 at a prescribed interval. A capacitor 21 accumulates the charge of the power source pulse A so as to set it to be driving power on the side of the reception stations 6. When the power source pulse A terminates, the both ends of the transmission line 5 is set to a state where they are terminated by a characteristic impedance by the reverse bias operation of a diode 20 so as to transmit a high speed digital signal. Control data is inserted between the power source pulses A as the data pulse B by giving a time difference to it while it is sequentially transmitted to the transmission line 5. Respective reception stations 6 separate the data pulse B in synchronizing with the power source pulse and reproduce an analog value.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention connects a plurality of analog devices scattered in a plant etc. through a single transmission path, and multiplexes control data from a control device to the analog devices through this transmission path. The present invention relates to an analog multiplex transmission method for transmission.

0002

2. Description of the Related Art Analog devices called actuators are often used to control plants and automation equipment using analog variables such as valve openings and motor rotation speeds. When connecting these devices to a control device, it is common to individually wire each analog device and connect it to the control device via a D/A converter.

0003

[Problem to be Solved by the Invention] However, analog devices are often scattered in various places, and it is very time-consuming to individually wire between the control device and these devices. If the wiring is scattered, a large amount of wiring material is required, resulting in a heavy economic burden. Further, the control device requires a large number of wiring connections, which makes the device larger than necessary, and the large number of wires coming in and going out makes it complicated, which can lead to wiring errors.

In view of the above points, the present invention connects a plurality of analog devices scattered in a plant or the like to one transmission path, and transmits control data to the plurality of analog devices in a multiplex manner. The purpose of the present invention is to provide an analog multiplex transmission method that enables the following.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention connects one transmission path shared by a plurality of receiving stations assigned own station numbers to a transmitting station, and transmits a peak value from the transmitting station to a transmitting station. sends power pulses that are sufficiently higher than the data pulses used for data transmission to the transmission line at predetermined intervals, and at each receiving station, the electric charge of the power pulses is accumulated in diodes and capacitors to serve as driving power for the receiving station, and the power pulse ends. At this point, both ends of the transmission line are terminated with a characteristic impedance due to the reverse bias effect of the diode, making it possible to transmit high-speed digital signals.Furthermore, each receiving station detects the end point of the power pulse, and thereby Oscillators with the same phase and frequency are simultaneously oscillated to determine the timing to capture data, and the transmitting station generates data pulses based on digital data that controls various actuators connected to each receiving station. The data pulses are sequentially sent to the transmission path while being inserted between the power pulses with a preset time difference for each own station number of each receiving station, and each receiving station receives the data pulses in synchronization with the power pulses based on the time difference. By separating and counting the data pulses for a certain period of time, only the data pulses corresponding to the own station number are captured, and the F/V
This converts the signal into an analog value and outputs it to the actuator.

[0006]

[Operation] In the analog multiplex transmission method according to the present invention, the main station is a transmitting station, the slave station is a receiving station, and the transmitting station sends power pulses having a sufficiently higher peak value than data pulses to the transmission line at predetermined intervals. do. At the receiving station, the electric charge of the power supply pulse is accumulated by a diode and a capacitor and used as driving power for the receiving station. This eliminates the need for a power supply on the receiving station side. At the end of the power supply pulse, both ends of the transmission line are terminated by characteristic impedance due to the reverse bias effect of the diode, making it possible to transmit high-speed digital signals. Further, each receiving station is given its own station number, and a time difference at the time of data acquisition is set in correspondence with the own station number. The transmitting station then converts the analog value that drives the actuator of each receiving station into digital data when transmitting the power pulse, and sequentially sends it out to the transmission line as a data pulse with a time difference corresponding to the own station number of each receiving station. and transmits while inserting it between power pulses. Each receiving station separates and captures data pulses based on the time difference corresponding to its own station number in synchronization with the power pulse, reconverts them into analog values, and outputs them to their respective actuators.

[0007]

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

FIG. 1 shows a schematic configuration of the entire apparatus employing the analog multiplex transmission method according to the present invention.
A plant control device 1 is equipped with an RS232C interface 2 that is a serial interface for communication, and an analog multiplex transmission section 3 is connected to the RS232C interface 2.

The analog multiplex transmission unit 3 has a transmitting station 4 that transmits data as its main station, and connects to the transmitting station 4 one transmission line 5 made of a twisted pair wire or a coaxial cable. Receiving station 6, which is a dependent station, is connected,
These many receiving stations 6 share one transmission path 5. Each of the receiving stations 6 is connected to an actuator 7 that controls the operation based on an analog quantity.

The transmitting station 4 of the analog multiplex transmission unit 3 includes a power pulse generator 8 for generating a power pulse A having a peak value of 30V as shown in FIG. 2, and a data pulse generator 8 for transmitting a data pulse B having a peak value of 10V. A power supply section 1 includes a pulse transmitting section 9 and a counter section 10 for counting pulses, and drives them.
1 is provided.

Further, the receiving station 6 is provided with a power pulse detecting section 12 for detecting the power pulse A, a station number setting section 13 for setting a own station number unique to each receiving station 6, and also for receiving the data pulse B. A data pulse receiving section 14, an oscillator 15 common to each receiving station for each receiving station 6 to generate an accurate clock with the same phase and frequency, a counter section 16 for counting pulses, and a frequency signal generated from the data pulse B. A frequency signal generation section 17, an F/V conversion section 18 that converts the frequency signal into a voltage signal, and an isolation section 19 that connects the actuator 7 with electrical insulation are provided. Further, as shown in FIG. 4, the connection part with the transmission line 5 is constructed by a circuit in which a diode 20 and a capacitor 21 are coupled in series, and both ends of the capacitor 21 are coupled to a power supply circuit (not shown) of the receiving station 6. ing.

Next, data transmission between the transmitting station 4 and the receiving station 6 will be explained.

First, a local station number representing the own station number is set in the station number setting section 13 of each receiving station 6. In addition, since the transmitting station 4 sends multiple pieces of data to each receiving station 6 to one transmission line 5, the data to each receiving station 6 is sent with a time difference to prevent confusion of data. Send sequentially. For this reason, the transmitting station 4 is set with a time difference when transmitting data corresponding to the own station number of each receiving station 6. Furthermore, each receiving station 6 also stores the number corresponding to the set time difference own station number as the time difference at the time of data acquisition of the own station, and selects the own station number from among the plurality of data transmitted from the transmitting station 4. Make it possible to retrieve the data.

[0014] Then, the power pulse A whose peak value is 30V, which is sufficiently higher than the peak value of the data pulse B, as shown in FIG. A data pulse B, which will be described later, is inserted in between. At the receiving station 6, when the power pulse A starts to rise, it is connected to the capacitor 2 through the diode 20.
1 and starts accumulating this charge. As shown in FIG. 3, the power supply pulse A takes charge and charges the capacitor 21, and at the end of the falling power supply pulse, the diode 20 in FIG. This enables the transmission of high-speed digital signals by terminating both ends of the transmission line 5 with characteristic impedance. The charge accumulated in the capacitor 21 is used as driving power for the receiving station 6.

Next, to explain the procedure for transmitting the data pulse B, when the control digital data for the actuator 7 is output from the control device 1 to the transmitting station 4 via the RS232C interface 2, the transmitting station 4 transmits the power pulse. Based on a clock pulse synchronized with A, a counter section 10 counts the time difference in data transmission, which is set in advance for each receiving station 6. Then, when the time set for each receiving station 6 has elapsed, control data for driving the actuator 7 of each receiving station 6 is sequentially sent to the transmission line 5 as a data pulse B. FIG. 2 is a transmission waveform diagram showing a state in which data pulse B is inserted between power pulses A. Data pulse B, which is control data, is sent to three reception stations 6 with a time difference, and the reception The data for the own station number (1) of station 6 is in part (1), and the data for the own station number (2) of receiving station 6 is in part (2).
In the part, the data for the own station number (3) of receiving station 6 is (3
) indicates that the data is being transmitted. Note that the part (0) is secured as a data stability period.

When the receiving station 6 receives a pulse signal as shown in FIG. 3, the power pulse detection unit 12 detects the end point of the power pulse A, and causes the oscillators 15 of all the receiving stations 6 to emit at the same time so that the pulse signal has the same phase. Clock signals of the same frequency are generated and the clocks of the respective oscillators 15 are accurately synchronized. Then, the data acquisition time stored for each receiving station 6 is counted by the counter section 16 based on the clock pulse from the end of the power pulse A, and when the data acquisition time has come, the data pulse reception section 14 starts the data pulse B. The data corresponding to the analog value is obtained by starting reading the data of the own station from among the plurality of data and counting the data pulses B for a certain period of time. After converting this data into a frequency signal by the frequency signal generator 17, the F/V converter 1
8 converts it into a voltage signal that becomes an analog signal, and outputs the analog value to the actuator 7 through the isolation section 19.

[0017] The F/V conversion is preferable because it can obtain higher accuracy than D/A conversion or the like. As for this digital-to-analog conversion method, it is preferable to appropriately adopt a method suitable for the system requirements.

FIG. 5 is a diagram showing another embodiment in which the connection format of the transmission line shown in FIG. 4 is modified, and although there is a difference in transmission speed from the connection format of the transmission line shown in FIG. Even if such a connection format is adopted, the essence of the present invention does not change, and it goes without saying that the present invention includes various modifications without departing from the gist of the present invention.

[0019]

As described above, according to the analog multiplex transmission method according to the present invention, a plurality of receiving stations 6 are connected to one transmission path 5 connected to the transmitting station 4 serving as the main station, and the receiving stations 6 Since the control data for the actuators 7 is inserted between the power pulses A sent from the transmitting station 4 with a time difference and transmitted to the receiving station 6, the actuators 7 scattered through one transmission line 5 can be controlled. This eliminates the need to individually connect each of the actuators 7 scattered in a plant etc. to the main control device as in the past, reducing the labor and materials required for wiring and reducing costs. Miswiring can be eliminated.

Furthermore, since the receiving station 6 accumulates the electric charge of the power pulse A sent from the transmitting station 4 and uses it as driving power for the receiving station 6, there is no need to provide a power supply device on the receiving station 6 side. The station 6 can be made compact, and there is no need to separately provide wiring for power supply from the transmitting station 4 side, so that the labor and cost required for wiring can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram illustrating an embodiment of the method of the present invention.

FIG. 2 is a transmission waveform diagram showing the relationship between power pulses and data pulses.

FIG. 3 is a transmission waveform diagram of power pulses.

FIG. 4 is an explanatory diagram showing a connection section between a transmission path and a receiving station.

FIG. 5 is an explanatory diagram showing another example of a connection format between a transmission path and a receiving station.

[Explanation of symbols]

1 Control device 3 Analog multiplex transmission section 4 Transmitting station 5 Transmission line 6 Receiving station 7 Actuator

Claims (1)

[Claims] Claim 1: One transmission path shared by a plurality of receiving stations assigned own station numbers is connected to a transmitting station, and the transmitting station sends power pulses whose peak value is sufficiently higher than the data pulse for data transmission at predetermined intervals. At each receiving station, the electric charge of the power pulse is accumulated by a diode and a capacitor and used as driving power for the receiving station.At the end of the power pulse, the reverse bias effect of the diode creates a characteristic impedance at both ends of the transmission line. In addition, each receiving station uses an oscillator with the same phase and frequency to detect the end point of the power pulse and use this to determine the timing to capture data on the transmission path. Simultaneous oscillation is performed, and the transmitting station generates data pulses based on digital data that controls various actuators connected to each receiving station, and the data pulses are given a preset time difference for each receiving station's own station number. The data pulses are sequentially sent to the transmission line while being inserted between the power pulses, and each receiving station separates the data pulses based on the time difference in synchronization with the power pulses, and calculates the own station number by counting the data pulses for a certain period of time. An analog multiplex transmission method characterized in that only corresponding data pulses are taken in, regenerated into analog values by F/V conversion, and output to an actuator.