DE10119396A1 - Time sequence of events determining method for complex automation system uses a large number of sensors and or actuators wirelessly connected to a central unit such that energy use is minimized - Google Patents

Abstract

According to the method: each sensor or actuator (4.1-4.n) determines the time of an event using its local clock (5.1- 5.n); the base station (1) constantly transmits the actual time from the main clock (2) together with data transfer blocks; a comparison of local and actual time is undertaken in the sensors and actuators and used to determine a correction value and; the time with the correction applied is used for time stamping events occurring in the actuator or sensor.

Description

The invention relates to a method for determining the chronological order events in a system with a large number of sensors and / or actuators. For example, the term "event" is used to report a an object-detecting proximity sensor or reporting the status of a Understood actuator. The invention can be used, for example, for proximity switches / proximity tion sensors, temperature measuring sensors, pressure measuring sensors, current measuring sensors or voltage measuring sensors as well as in micromechanical, piezoelectric, elec trochemical, magnetostrictive, electrostatic or electromagnetic actuators be used.

In particular, the invention is suitable for a machine or system with a lot number of sensors and / or actuators, for example industrial robots, manufacturing tomat or manufacturing machine.

In DE 199 26 799 A1, a system for a machine having a plurality of wireless proximity sensors, in particular a production machine, is proposed, wherein

• - Each proximity sensor at least one for energy consumption from a medium fre quent magnetic field has suitable secondary winding,
• - At least one primary winding fed by a medium-frequency oscillator for the wireless supply of the proximity sensors with electrical energy is seen
• - And wherein each proximity sensor is equipped with a transmitter, which radio signals containing interesting sensor information to a central, with outputs a base station connected to a process computer of the machine.

Compared to conventional solutions, this wireless system is also eliminated Wire / cable connection for electrical power supply and for communication relatively high due to planning, material, installation, documentation and maintenance Cost factor of the wire / cable connections. Failures due to Ka broken or bad, for example corroded contacts occur.

DE 199 26 562 A1 describes a method and an arrangement for wireless Supply of a large number of actuators with electrical energy, one actuator and one primary development and a system for a large number of actuators Schine proposed, the proposed technology with respect to Energiever Supply and communication similar to that for DE 199 26 799 A1 given technology.

In the systems mentioned above, it is important that the time series follow the occurrence of events - such as the chronological order of the Occurrence of sensor signals from proximity sensors. With The mode of operation can be helped by listing the time occurrence of the sensor signals of the system can be checked and it is easier and faster in the event of a malfunction This makes it possible to analyze the malfunction and to identify defective components. because is in the foreground that the communication facilities of the sensors and / or actuators are operated with the lowest possible energy consumption.

The invention has for its object a method for determining the temporal Order of occurrence of events in a system with a variety of  Specify sensors and / or actuators of the type mentioned, with its help the communication devices of the sensors and / or actuators with as little as possible can be operated according to energy consumption.

This task is fiction, in connection with the features of the preamble solved by the features specified in the characterizing part of claim 1.

The advantages that can be achieved with the invention are, in particular, that the front proposed procedure the resolving power with regard to the chronological order the occurrence of events is improved without requiring the Communication device of the sensors and / or actuators constantly switched on To keep condition. Rather, the sensors and / or actuators can be in one operated saving mode, in which the communication facilities of the Sensors and / or actuators only used to report the occurrence of an event be switched. Also the repeated transmission of the information in subsequent ones Periods affect the high achieved due to the time stamping of events Not resolving power. Such retransmission is upon occurrence interference, for example in the case of fading or interference.

Further advantages are evident from the description below.

Advantageous embodiments of the invention are characterized in the subclaims net.

The invention is described below with reference to the embodiment shown in the drawing Examples explained. Show it:

Fig. 1 is a system sisstation with a plurality of sensors and / or actuators and a Ba,

Fig. 2 is a cyclic TDMA data transmission block,

Fig. 3 shows a sequence of successively successive data blocks.

In Fig. 1, a system is shown with a plurality of sensors and / or actuators and a base station. The base station 1 has a master clock 2 and a communication device 3 . It is a multitude of sensors and / or actuators 4.1 , 4.2 . , , 4 .n (n = any integer positive number) is provided, which are installed, for example, within a system or attached to a machine, in particular a production machine. The sensors and / or actuators 4.1 , 4.2 . , , 4 .n each have a local clock 5.1 , 5.2 . , , 5 .n and a communication device 6.1 , 6.2 . , , 6 .n on. It is always from sensors / actuators 4.1 . , , 4 .n the speech, which can be either sensors or actuators. In general, the sensors have a sensor head which detects the sensor environment with a downstream signal evaluation, and the actuators have an actuator unit (for example a compressed air valve or a contactor) and a control unit therefor.

The communication facilities 6.1 . , , 6 .n of the sensors / actuators contain the necessary radio transmitters and / or radio receivers in order to establish wireless communication between base station 1 and sensors / actuators 4.1 . , , 4 .n to enable. In the case of a sensor, the processed sensor signal reaches a modulator / encoder with a downstream radio transmitter and antenna, from where it is sent to the base station 1 . In the case of an actuator, the control signal sent by the base station 1 reaches the control unit via an antenna, a radio receiver and a demodulator / decoder.

The base station 1 is expediently connected to a central computer (process computer, programmable logic controller), receives sensor signals from the sensors and signal signals relating to the current state of actuators (uplink, "in the upward direction", from the sensors / actuators to the base station), and gives control signals Activation / deactivation of the actuators and emits signals for setting specific parameters of the actuators and sensors (downlink, "in the downward direction", from the base station to the sensors / actuators). The communication device 3 of the base station accordingly has an antenna to which a radio receiver and a radio transmitter are connected. The signals of the radio receiver are fed to a demodulator / decoder and a modulator / encoder is connected upstream of the radio transmitter.

In FIG. 2 a cyclical TDMA frame (Time Division Multiple Access) is illustrated as it is preferably used in the proposed system. Such a data transmission block or frame R1 is composed of n successive time slots ZT.1, ZT.2. , .ZT.n together. Anytime slot ZT.1. , .ZT.n is assigned to a specific sensor or actuator. Although, for example, the sensors generate their messages at random moments, it does not follow an immediate, but rather a transmission adapted to the assigned time slot. The precise timing of the time slots ZT.1. , .ZT.n and frame R1. , , is done by the master clock 2 of the base station 1 . Since the local clocks 5.1 . , , 5 .n of the sensors / actuators are not synchronized with master clock 2 , each time slot contains ZT1. , .ZT.n in addition to the information to be transmitted, a typical synchronization word for exact synchronization between base station 1 on the one hand and sensors / actuators 4.1 . , , 4 .n on the other hand.

In this context, FIG. 3 shows a sequence of successively successive data transmission blocks R1, R2, R3. , , shown. R1, R2, R3 can also be referred to as frame numbers.

If the communication is not exposed to interference, the information or events of all sensors / actuators 4.1 are transmitted. , , 4 .n within a single frame or frame. However, in the base station 1, the individual events transmitted within a frame cannot be assigned a precise chronological order, since - as mentioned above - the transmission does not take place according to the time of occurrence of the events, but rather according to the respectively assigned time slot.

If faults occur, for example fading or interference, this is repeated Transmission of the information in the following framework or in the following Frame required. For example, a transmission security of  99.99% are assumed if the four successive frames transmit the same information. After four frames have been transferred, an actua takes place Information in the fifth frame (which in turn four times is transmitted). It is easy to understand that in the example given during the timeframe of four frames the reported events no precise temporal Order can be assigned.

One way of improving the resolution with regard to the temporal sequence of the occurrence of events is that the base station 1 assigns an ascending number to each frame sent and that this number is sent together with the frame and is thus communicated to the sensors / actuators. The sensors / actuators 4.1 . , , 4 .n can then determine during which frame an event to be reported occurs and, when the event is reported, name this number of the frame. This solution to the time stamping with frame number requires, however, that the sensors / actuators 4.1 . , , 4 .n be operated continuously in the switched-on state in order to know the current frame number. This possibility of improvement is therefore ruled out in realizations in which a continuous on state of the communication devices of the sensors / actuators is not desired in order to minimize the energy consumption.

Another way of improving the resolution with regard to the chronological order of occurrence of events is that the base station 1 sends the current time of the master clock 2 together with the data transmission blocks. This current time of the master clock 2 synchronizes the time of the local clock 5.1 . , , 5 .n. The sensors / actuators 4.1 . , , 4 .n can then record the time of the local clock as a time stamp when an event occurs. An advantage of this method is that the time stamp is much more accurate because the exact moment of the occurrence of the event is captured within a frame. A disadvantage of this method, however, is that the local time 5.1 . , , 5 .n always shows a certain deviation (drift) from the time of the master clock 2 . In addition, this solution to time stamping using local time also presupposes that the communication devices of the sensors / actuators 4.1 . , , 4 .n be operated continuously in the switched-on state. This possibility of improvement is therefore also ruled out in implementations in which a continuous on state of the communication devices of the sensors / actuators 4.1 . , , 4 .n is not desired in order to minimize energy consumption.

Do you want the continuous on state of the communication devices of the sensors / actuators 4.1 . , , 4 .n avoid, in order to minimize the energy consumption of the sensors / actuators, it is proposed that although the base station 1 constantly sends the current time of the master clock 2 together with the data transmission blocks, the communication devices of the sensors / actuators 4.1 . , , 4 .n can only be operated when an event occurs in the switched-on state. During such a switch-on state of the communication device, the sensor / actuator 4.1 . , , 4 .n receive the current time of master clock 2 and the current time of local clock 5.1 . , , 5 .n compared.

The discrepancies between these two times are used to adaptively adapt the time of the local clock 5.1 . , , 5 .n to achieve the time of the master clock 2 , ie a correction factor is formed with which the time of the local clock 5.1 . , , 5 .n is weighted to form a time based on the master clock 2 . This with the for the various sensors / actuators 4.1 . , , 4 .n different correction factors weighted times of the local clocks 5.1 . , , 5 .n are based on the same time base and can therefore be compared with each other. Consequently, a time stamping of the occurring events based on the time of the local clocks 5.1 . , , 5 .n and the correction factors formed. In this way, the chronological order of occurrence of events can be precisely recorded using the time stamp of the individual events and followed.

As an alternative to the method explained above, it is also possible that the correction factors are not in the individual sensors / actuators 4.1 . , , 4 .n are formed, but instead in the base station 1 . For this purpose the sensors / actuators 4.1 . , , 4 .n when an event occurs during the subsequent assigned time slot

• - the time of the local clock 5.1 . .5.n at the time the event occurred,
• - the time of the local clock 5.1 . , , 5 .n at the time of transmission as well
• - The received time of master clock 2 at the time of transmission.

From the time of the local clock 5.1 . , , 5 .n at the time of transmission and the received time of the master clock 2 at the time of transmission, the base station 1 forms the correction factor with which the time of the local clock 5.1 . , , 5 .n must be weighted in order to form a time for the relevant event on the basis of master clock 2 .

Claims (3)

1. Method for determining the chronological order of the occurrence of events in a system with a plurality of sensors and / or actuators (4.1.. .4.n), which at least partially with wireless communication devices (6.1.. .6.n) and a local clock (5.1. .5.n) are equipped, and a central base station ( 1 ) with wireless communication device ( 3 ) and master clock ( 2 ), the base station ( 1 ) continuously transmitting data blocks (R) for the sensors and / or actuators (4.1. .4.n) and the time of the notification of the occurrence of an event occurs with a time delay after the time of the occurrence of this event during an assigned time period, characterized in that

• - that the sensor and / or actuator (4.1.. .4.n) determines the time of the local clock (5.1.. .5.n) when an event occurs,
• - That the base station ( 1 ) constantly sends the current time of the master clock ( 2 ) together with the data transmission blocks,
• - that the current time of the master clock ( 2 ) is compared with the current time of the local clock (5.1. .5.n),
• - That a correction factor is formed from the discrepancies between these two times by which the time of the local clock (5.1. .5.n) must be weighted in order to form a time based on the master clock ( 2 ),
• - That the time of the local clock weighted with the correction factor (5.1. .5. n) is used when the event occurs for a time stamping of the occurring events based on the time of the master clock ( 2 ).

2. The method according to claim 1, characterized in that the formation of the correction factors and the time stamping of the events occurring in each sensor and / or actuator (4.1.. .4.n) and the base station ( 1 ) only the events provided with time stamps be reported. 3. The method according to claim 1, characterized in that the formation of the correction factors and the time stamping of the events occurring in the base station ( 1 ) takes place, for which purpose the sensors and / or actuators (4.1. .4.n)

• - the time of the local clock (5.1..5.n) at the time the event occurred,
• - the time of the local clock (5.1. .5.n) at the time of transmission and
• - The received time of the master clock ( 2 ) at the time of transmission

report to the base station ( 1 ) and the base station forms the correction factor from the time of the local clock (5.1. .5.n) at the time of transmission and the received time of the master clock ( 2 ) at the time of transmission.