CN116996154A - Synchronous acquisition system and method based on EtherCAT - Google Patents

Abstract

The invention discloses a synchronous acquisition system and a synchronous acquisition method based on EtherCAT. The invention utilizes EtherCAT industrial Ethernet to realize that the master station equipment controls a plurality of slave station equipment to synchronously collect and transmit and receive data, synchronous collection deviation does not exist in different collection channels of single slave station equipment, the synchronous collection deviation among different slave stations is accurate to nanosecond level, the real-time performance of the system is improved, and the compatibility and the expansion capability of the system are enhanced.

Description

Synchronous acquisition system and method based on EtherCAT

Technical Field

The invention relates to a synchronous acquisition system, in particular to an EtherCAT-based synchronous acquisition system, and belongs to the technical field of synchronous acquisition.

Background

In general, in the working process of large-scale mechanical equipment, the mechanical vibration state of the large-scale mechanical equipment can be analyzed, a plurality of vibration measuring points are required to be collected at the same time, and the high-precision synchronous collection of multi-point vibration data is very important to the simulation and consistency analysis of the large-scale mechanical equipment.

In the prior art, 1) an EtherCAT slave station module disclosed by publication No. CN112711202A comprises hardware and a driver program loaded on the hardware, wherein the EtherCAT slave station module can realize multiple pulse mode output through the MCU interface driver program;

2) An EtherCAT slave station controller based on a DSP processor and a communication method are disclosed in the publication No. CN 112667532A. The first interface of the DSP processor is connected with the EtherCAT slave station controller, so that data transmission between the DSP processor and the EtherCAT slave station controller can be efficiently carried out, the EtherCAT slave station controller carries out synchronous signal transmission with the DSP processor through a plurality of interrupt interfaces, the signal transmission efficiency is effectively improved, and the slave station controller with low cost, strong universality and high configurability is realized;

3) The system and the method for calibrating the multichannel synchronous acquisition phase disclosed by the publication No. CN110266421A are characterized in that target phase information corresponding to a reference channel is compared with target phase information corresponding to the rest channels, and control parameters are output to a programmable clock delay module according to a comparison result, so that the programmable clock delay module calibrates the multichannel clock network signals according to the control parameters, and calibration of the multichannel clock network signals is realized;

4) The analog signal multichannel synchronous acquisition system and the acquisition method thereof disclosed by the publication No. CN111856993A are characterized in that when a signal acquisition input unit acquires signals, a generation unit generates virtual signals, the analog signals are transmitted regularly through an analog signal timing transmission module, the acquisition system is self-checked in a mode of inserting the virtual signals, and the produced information and the information converted by the acquisition system are compared, so that the integrity of the information acquired by the acquisition system can be checked, the safety is higher, and errors are not easy to occur;

5) The high-precision synchronous acquisition device for the lightning arrester on-line monitoring system disclosed by the publication No. CN215493858U can improve the precision of on-line monitoring of leakage current of the lightning arrester according to the locked standard time pulse signal and the sampling starting signal;

6) The signal acquisition control slave station system based on the FPGA is disclosed by the publication number CN216286236U, and each slave station unit comprises an AD module, an FPGA main control unit and an EtherCat industrial Ethernet module which are in communication connection; the FPGA is used for realizing acquisition channel selection and gain control; the EtherCat industrial Ethernet module is used for realizing the synchronous data acquisition of multiple slave stations; the EtherCat is adopted as a slave station protocol, and the board card can realize data synchronous transmission; a secondary station system is constructed using a multiple secondary station design.

In the multichannel synchronous acquisition equipment, in order to ensure the synchronism of acquisition, the prior art can know that the multichannel synchronous acquisition equipment is mainly divided into two schemes: one scheme adopts FPGA/DSP to send acquisition instructions to a plurality of AD chips at the same time; the other scheme transmits an acquisition instruction to the acquisition device through a standard time pulse signal of the Beidou time service device. The deviation generated by the first scheme mainly comes from the SYNC synchronizing signals of the matched crystal oscillator of the FPGA/DSP and different AD chips, and the scheme synchronously collects the deviation to be a subtle level; the deviation generated by the second scheme is of nanosecond level, but the scheme needs to be periodically time-synchronized with the Beidou system, and is not suitable for use in certain network closed environments.

Disclosure of Invention

The invention aims to solve at least one technical problem and provide an EtherCAT-based synchronous acquisition system.

The invention realizes the above purpose through the following technical scheme: the synchronous acquisition system based on the EtherCAT comprises a master station device and a plurality of slave station devices supporting the synchronous acquisition of the EtherCAT;

the synchronous acquisition system carries out synchronous acquisition through a synchronous clock of the EtherCAT slave station controller;

the master station equipment comprises equipment with an Ethernet interface and TWINCAT3 upper computer software matched with EtherCAT, and the slave station equipment comprises two EtherCAT industrial Ethernet interfaces and IEPE vibration sensors with four acquisition channel interfaces;

the connection mode of the master station device and the slave station device comprises a direct connection mode and an open mode;

the master station device and the slave station device are installed in a distributed mode.

As still further aspects of the invention: the direct connection mode is that a master station device is connected with a plurality of slave station devices, and the plurality of slave station devices are connected through the Ethernet and form an Ethernet device.

As still further aspects of the invention: the open mode is that a plurality of master station devices are connected with a plurality of slave station devices, the plurality of slave station devices are divided into at least two groups of Ethernet devices, and the slave station devices of each group of Ethernet devices are connected through Ethernet.

As still further aspects of the invention: distributed installations include, but are not limited to, linear installations, ring installations, and tree installations.

A synchronous acquisition method of a synchronous acquisition system, the synchronous acquisition method comprising:

s1, installing TWINCAT3 upper computer software matched with EtherCAT on equipment provided with an Ethernet interface to form master station equipment;

s2, the upper computer software of the master station equipment controls all slave station equipment of the same EtherCAT network segment;

s3, the slave station equipment takes the MCU as a main control, processes the instruction issued by the master station equipment and uploads the data processed by the FPGA;

s4, the synchronous clock of the EtherCAT slave station controller is accessed to an FPGA pin, and an AD acquisition instruction is issued in real time by capturing signal changes.

As still further aspects of the invention: in step S1, after installing the twin cat3 upper computer software, the master station device performs the following configuration:

1) Scanning the slave station apparatus;

2) Setting a slave station device synchronization mode;

3) Setting a slave station device synchronization period;

4) Setting a transmission data structure;

5) After the configuration is completed, a command control interface is entered.

As still further aspects of the invention: in step S2, the control of the slave station apparatus includes: the method comprises the steps of collecting time selection, stopping collecting, sampling rate selection, amplification factor selection, resetting, standby, uploading original data, uploading processed data and stopping uploading data.

As still further aspects of the invention: the slave station device includes seven interfaces: the system comprises a power supply interface, a data input interface, a data output interface and a four-way vibration signal acquisition interface; the data input interface is connected with the output interfaces of other secondary station equipment or the master station, the data output interface is connected with the data input interfaces of other secondary station equipment, and the vibration signal acquisition interface is connected with the IEPE vibration sensor.

As still further aspects of the invention: in step S4, the synchronization clock of the EtherCAT slave station controller includes:

a) System time: the system time is the system timing of the synchronous acquisition system and is used for communication and time marking;

b) Reference clock and slave clock: the clock of the first slave station equipment with the EtherCAT function connected with the master station equipment is used as a reference clock, and the clocks of other slave station equipment are slave clocks; wherein the reference clock is used to synchronize the slave clocks of other slave station devices with the master station clock, the reference clock providing system time;

c) Master station clock: an initialization clock provided by the master station device;

d) Local clock: each slave station equipment with the EtherCAT function locally and independently operates a local clock, the difference value between the local clock and the reference clock is a clock initial offset, the reference clock is different from the clock source between each slave station equipment with the EtherCAT function, and the offset existing in the operation process is the clock drift;

e) Local system time: the local clock of each slave station equipment with the EtherCAT function generates a local system time after compensation and synchronization, and the EtherCAT clock synchronization mechanism keeps the local system time of each slave station equipment consistent, and the reference clock keeps consistent with the local system time of the slave station equipment;

f) Transmission delay time: the delay of command data frames when transmitted between the respective slave station apparatuses due to the internal and physical connection of the apparatuses is referred to as a transmission delay time;

h) Dynamic clock offset: the reference clock is different from the clock source between the slave station devices with EtherCAT function, and the offset existing in the running process is a dynamic clock offset.

As still further aspects of the invention: in step S4, the method for calculating the synchronization clock of the EtherCAT slave station controller includes:

i) when initializing, the master station equipment transmits command data frames and acquires clock initial offset of each slave station equipment;

II) when initializing, the master station equipment reads the time value stored by the slave station equipment and calculates the transmission delay time;

III) in the initialization process, in order to quickly compensate the initial deviation of the clock, the master station equipment continuously transmits commands in independent command data frames after measuring the transmission delay time and the initial offset of the clock, so that the slave station equipment time is synchronous, and the initialization of the distributed clock is completed;

IV) in the periodic operation stage, the command is periodically sent along with the process data to read the reference system time, the reference system time is written into the slave station equipment, and the dynamic clock offset is compensated in real time.

The beneficial effects of the invention are as follows:

1) The synchronous acquisition system adopts a distributed installation mode, and utilizes the EtherCAT industrial Ethernet to realize the synchronous acquisition and data receiving and transmitting of a plurality of slave station devices controlled by the master station device;

2) The single slave station equipment has no acquisition deviation in different acquisition channels, and the synchronous acquisition deviation among different slave station equipment is accurate to nanosecond level, so that compared with the first scheme, the technical scheme effectively reduces the synchronous acquisition deviation;

3) The EtherCAT industrial Ethernet adopted by the synchronous acquisition system is that an EtherCAT slave station controller is added on the basis of the Ethernet, and compared with the second scheme, the technical scheme can be used in a network closed environment;

4) The synchronous acquisition system has the characteristics of high instantaneity, multiple access points, flexible topology and the like, not only improves the instantaneity of the system, but also enhances the compatibility and expansion capacity of the system, and adopts EtherCAT industrial Ethernet as a communication bus of a master station device and a synchronous acquisition slave station device, thereby effectively reducing the time deviation of synchronous acquisition.

Drawings

FIG. 1 is a schematic diagram of a system architecture in a direct connection mode according to the present invention;

FIG. 2 is a schematic diagram of a system architecture in an open mode of the present invention;

FIG. 3 is a schematic diagram of the software configuration steps of the synchronous acquisition master station of the present invention;

FIG. 4 is a schematic diagram of a scanning slave station apparatus of the present invention;

FIG. 5 is a diagram illustrating a synchronization mode and a synchronization cycle according to the present invention;

FIG. 6 is a diagram showing the average value of AD samples received by the channel 1;

FIG. 7 is a schematic diagram of a software command control interface of a synchronous acquisition master station;

FIG. 8 is a schematic diagram of the synchronous acquisition slave station of EtherCAT of the present invention;

FIG. 9 is a schematic diagram of the EtherCAT synchronous clock computation of a plurality of slave stations according to the present invention;

FIG. 10 is a schematic diagram of the internal computing scheme of a single slave station of the present invention;

FIG. 11 is a diagram illustrating a data input/output event completed during a data refresh cycle according to the present invention;

fig. 12 is a schematic diagram of the EtherCAT slave station response synchronous acquisition instruction flow in the present invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Embodiment one: the synchronous acquisition system based on the EtherCAT comprises a master station device and a plurality of slave station devices supporting the synchronous acquisition of the EtherCAT.

The master station equipment refers to equipment with an Ethernet interface, TWINCAT3 upper computer software matched with EtherCAT can be installed on the equipment, and the slave station equipment comprises two EtherCAT industrial Ethernet interfaces and IEPE vibration sensors with four acquisition channel interfaces.

Each secondary station device has an appearance of 160mm×100mm×70mm, the furthest transmission distance between the secondary station devices is 100m, and the primary station device and the secondary station device can form a distributed structure in a linear, ring-shaped and tree-shaped topology.

What is needed here is explicitly: the synchronous acquisition system carries out synchronous acquisition through the synchronous clock of the EtherCAT slave station controller.

Embodiment two: direct mode of master device and slave device. As shown in fig. 1, the synchronous acquisition system comprises a master station device and a plurality of slave station devices, wherein the master station device is connected with a first slave station device, and the first slave station device is sequentially connected with other slave station devices in series. The slave station devices are sequentially connected in series to form an EtherCAT network segment, namely an Ethernet device.

Embodiment III: an open mode of the master device and the slave device. As shown in fig. 2, the synchronous acquisition system comprises a plurality of master station devices and a plurality of slave station devices. The slave station devices of each group are sequentially connected in series through Ethernet, and the first slave station device of each group of slave station devices is connected with the switch through Ethernet. Thus, the slave devices of each group form an EtherCAT network segment, i.e. form an ethernet device.

It should be noted that: in the second embodiment and the third embodiment, the master station device does not need to be provided separately, only needs to be an existing device with an ethernet interface, and can install the twin cat3 upper computer software matched with the EtherCAT on the device. The TWINCAT3 upper computer software can be installed under both the WINDOWS operating system and the Ubuntu operating system.

In addition, to ensure the stability of the synchronous acquisition system, the EtherCAT slave controller synchronization period is generally set to the millisecond level. The EL6XXXX series independent master station equipment manufactured by Beckhoff is used, and the synchronization period can be shortened to microsecond level, so that the uploading rate of the acquired data is improved.

Embodiment four: as shown in fig. 12, a synchronous acquisition method of a synchronous acquisition system based on EtherCAT includes:

first: and installing TWINCAT3 upper computer software matched with EtherCAT on equipment provided with an Ethernet interface, wherein the equipment becomes master station equipment.

After the software of the twin cat3 upper computer of the master station device is installed, as shown in fig. 3, the master station device is configured: 1) Scanning the slave station apparatus; 2) Setting a slave station device synchronization mode; 3) Setting a slave station device synchronization period; 4) Setting a transmission data structure; 5) After the configuration is completed, a command control interface is entered.

Taking 8 sets of slave station equipment as an example, clicking SCAN in software of the master station equipment to SCAN equipment can SCAN 8 sets of slave station equipment normally. When a certain slave station device is not scanned due to software, the synchronization mode of other slave station devices is not affected. The corresponding slave device number can be seen in the software of the master device to disappear, thereby locating the failed slave device, as shown in fig. 4.

The synchronization mode and synchronization period are set in the software of the master station device, and the minimum can be set to microsecond level. To ensure system stability, it is typically set to the millisecond level. The synchronization pattern and synchronization period are set as shown in fig. 5.

The setting data structure can be changed according to personal requirements, and the setting can be performed in software of the master station device, and the setting channel 1 receives the average value of the AD samples, as shown in fig. 6.

Second,: and the upper computer software of the master station equipment controls all the slave station equipment in the same EtherCAT network segment.

Control (operation) of all the slave devices includes: acquisition time selection (duration can be customized), stop acquisition, sampling rate selection (default 8K, optional 16K, 32K), magnification selection (not magnification, 10-fold magnification, 100-fold magnification), reset, standby, upload raw data, upload processed data, and stop uploading data, as shown in fig. 7.

Third,: the slave station equipment takes the MCU as a main control, processes the instruction issued by the master station equipment and uploads the data processed by the FPGA.

The main structure of the slave station equipment consists of a power supply circuit, AD sampling, a main control unit and EtherCAT industrial Ethernet, as shown in figure 8.

The power supply circuit is divided into an analog power supply circuit, a digital power supply circuit and a sensor power supply circuit;

the AD sampling mainly comprises IEPE sensor excitation source selection, direct current isolation, amplification factor selection, filtering, AD conversion and digital isolation circuits.

The MCU is a main control unit, receives a command from the master station device from the EtherCAT slave station controller, transmits the command to the FPGA, and uploads AD data from the FPGA to the master station device through EtherCAT industrial Ethernet.

The minimum system of the FPGA is configured by SPI, the main clock is 25MHz, two DDR3L are configured, and the reset is external reset. The FPGA receives MCU instructions to control the amplification factor, sampling rate and the like of the AD chip, and the acquired AD data is uploaded to the MCU in real time after the processing of the MCU instructions is completed.

The EtherCAT industrial Ethernet is mainly realized by an EtherCAT slave station controller, programs are written into the EEPROM through an RJ45 network port, two paths of RJ45 interfaces are provided, one path is a data input interface, and the other path is a data output interface. The data input interface is connected with the output interfaces of other slave station devices or the master station, and the data output interface is connected with the data input interfaces of other slave stations or not. In addition, the secondary station equipment also comprises a power interface and a four-way vibration signal acquisition interface; the vibration signal acquisition interface is connected with the IEPE vibration sensor.

Fourth,: the synchronous clock of the EtherCAT slave station controller is accessed to the FPGA pin, and an AD acquisition instruction is issued in real time by capturing signal change.

As shown in fig. 9, 10 and 11, the synchronization clock of the EtherCAT slave station controller includes:

a) System time: the system time is the system timing of the synchronous acquisition system and is used for communication and time marking;

b) Reference clock and slave clock: the clock of the first slave station equipment with the EtherCAT function connected with the master station equipment is used as a reference clock, and the clocks of other slave station equipment are slave clocks; wherein the reference clock is used to synchronize the slave clocks of other slave station devices with the master station clock, the reference clock providing system time;

c) Master station clock: an initialization clock provided by the master station device;

d) Local clock: each slave station equipment with the EtherCAT function locally and independently operates a local clock, the difference value between the local clock and the reference clock is a clock initial offset, the reference clock is different from the clock source between each slave station equipment with the EtherCAT function, and the offset existing in the operation process is the clock drift;

e) Local system time: the local clock of each slave station equipment with the EtherCAT function generates a local system time after compensation and synchronization, and the EtherCAT clock synchronization mechanism keeps the local system time of each slave station equipment consistent, and the reference clock keeps consistent with the local system time of the slave station equipment.

f) Transmission delay time: the delay of command data frames when transmitted between the respective slave station apparatuses due to the internal and physical connection of the apparatuses is referred to as a transmission delay time;

h) Dynamic clock offset: the reference clock is different from the clock source between the slave station devices with EtherCAT function, and the offset existing in the running process is a dynamic clock offset.

And determining a synchronous clock signal SYNC through the seven parts a) to h), wherein the clock synchronization precision among a plurality of slave station devices is not more than 30ns, and realizing the synchronous acquisition function of the synchronous acquisition system of the EtherCAT according to the synchronous clock.

A data refresh period is provided between two SYNC signals of the EtherCAT slave station controller, when a data receiving and transmitting event occurs, the slave station device copies output data from a received command data frame in the data refresh period, and then waits for the SYNC signals to reach and then continues the local operation.

The method for calculating the synchronous clock of the EtherCAT slave station controller comprises the following steps:

i) during initialization, the master station device sends command data frames, and obtains clock initial offset of each slave station device (the initial offset is only used for rough synchronization of the slave station device time and only needs to be measured once);

II) when initializing, the master station equipment reads the time value stored by the slave station equipment and calculates the transmission delay time (in order to obtain accurate transmission delay time, the master station equipment can measure for many times and then average, and can measure the transmission delay at any time in the operation after initializing so as to compensate the influence of environmental change on the transmission delay);

III) in the initialization process, in order to quickly compensate the initial deviation of the clock, the master station equipment continuously transmits commands in independent command data frames after measuring the transmission delay time and the initial offset of the clock, so that the slave station equipment time is synchronous, and the initialization of the distributed clock is completed;

IV) in the periodic operation stage, the command is periodically sent along with the process data to read the reference system time, the reference system time is written into the slave station equipment, and the dynamic clock offset is compensated in real time.

When the master station device issues the acquisition command, the acquisition command is contained in a data refresh cycle. In order to ensure the precision of synchronous acquisition, after receiving a synchronous acquisition instruction, the FPGA waits for the next synchronous clock signal, and after capturing the next synchronous clock signal, the FPGA can send the acquisition instruction to the AD. By the method, clock offset and transmission time delay of each secondary station device are reduced, and synchronous acquisition deviation precision among the secondary station devices is not more than 200ns.

Working principle: the distributed installation is adopted, the EtherCAT industrial Ethernet is utilized, the master station equipment is used for controlling the synchronous acquisition and data receiving and transmitting of a plurality of slave station equipment, synchronous acquisition deviation does not exist in different acquisition channels of single slave station equipment, and the synchronous acquisition deviation between different slave station equipment is accurate to nanosecond level.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.

Claims (10)

1. The synchronous acquisition system based on EtherCAT is characterized in that:

the synchronous acquisition system comprises a master station device and a plurality of slave station devices supporting synchronous acquisition of EtherCAT;

the synchronous acquisition system synchronously acquires the synchronous clock of the EtherCAT slave station controller;

the master station equipment comprises equipment with an Ethernet interface and TWINCAT3 upper computer software matched with EtherCAT installed on the equipment;

the slave station equipment comprises two EtherCAT industrial Ethernet interfaces and an IEPE vibration sensor with four acquisition channel interfaces;

the connection mode of the master station equipment and the slave station equipment comprises a direct connection mode and an open mode;

the master station device and the slave station device are installed in a distributed mode.

2. The synchronous acquisition system of claim 1, wherein: the direct connection mode is that a master station device is connected with a plurality of slave station devices, and the plurality of slave station devices are connected through the Ethernet and form an Ethernet device.

3. The synchronous acquisition system of claim 1, wherein: the open mode is that a plurality of master station devices are connected with a plurality of slave station devices, the plurality of slave station devices are divided into at least two groups of Ethernet devices, and the slave station devices of each group of Ethernet devices are connected through Ethernet.

4. The synchronous acquisition system of claim 1, wherein: the distributed installations include, but are not limited to, linear installations, ring installations, and tree installations.

5. A synchronous acquisition method based on the synchronous acquisition system of claim 1, characterized in that the synchronous acquisition method comprises:

s1, installing TWINCAT3 upper computer software matched with EtherCAT on equipment provided with an Ethernet interface to form master station equipment;

s2, the upper computer software of the master station equipment controls all slave station equipment of the same EtherCAT network segment;

s3, the slave station equipment takes the MCU as a main control, processes the instruction issued by the master station equipment and uploads the data processed by the FPGA;

s4, the synchronous clock of the EtherCAT slave station controller is accessed to an FPGA pin, and an AD acquisition instruction is issued in real time by capturing signal changes.

6. The synchronous acquisition method according to claim 5, wherein in step S1, after installing the twin cat3 upper computer software, the master station device performs the following configuration:

1) Scanning the slave station apparatus;

2) Setting a slave station device synchronization mode;

3) Setting a slave station device synchronization period;

4) Setting a transmission data structure;

5) After the configuration is completed, a command control interface is entered.

7. The synchronous acquisition method according to claim 5, wherein in the step S2, the control of the slave station apparatus includes: the method comprises the steps of collecting time selection, stopping collecting, sampling rate selection, amplification factor selection, resetting, standby, uploading original data, uploading processed data and stopping uploading data.

8. The synchronized acquisition method of claim 5, wherein the secondary station device includes a seven-way interface: the system comprises a power supply interface, a data input interface, a data output interface and a four-way vibration signal acquisition interface; the data input interface is connected with output interfaces of other secondary station equipment or the master station, the data output interface is connected with data input interfaces of other secondary station equipment, and the vibration signal acquisition interface is connected with the IEPE vibration sensor.

9. The synchronous acquisition method according to claim 5, wherein in the step S4, the synchronous clock of the EtherCAT slave station controller includes:

a) System time: the system time is the system timing of the synchronous acquisition system and is used for communication and time marking;

b) Reference clock and slave clock: the clock of the first slave station equipment with the EtherCAT function connected with the master station equipment is used as a reference clock, and the clocks of other slave station equipment are slave clocks; wherein the reference clock is used to synchronize the slave clocks of other slave station devices with the master station clock, the reference clock providing system time;

c) Master station clock: an initialization clock provided by the master station device;

d) Local clock: each slave station device with EtherCAT function operates independently as a local clock, and the difference value between the local clock and the reference clock is the initial offset of the clock;

e) Local system time: the local clock of each slave station equipment with the EtherCAT function generates a local system time after compensation and synchronization, and the EtherCAT clock synchronization mechanism keeps the local system time of each slave station equipment consistent, and the reference clock keeps consistent with the local system time of the slave station equipment;

f) Transmission delay time: the delay of command data frames when transmitted between the respective slave devices due to the internal and physical connections of the devices is referred to as a transmission delay time;

h) Dynamic clock offset: the reference clock is different from the clock source between the slave station devices with EtherCAT function, and the offset existing in the running process is a dynamic clock offset.

10. The method according to claim 9, wherein in the step S4, the method for calculating the synchronization clock of the EtherCAT slave station controller includes:

i) when initializing, the master station equipment transmits command data frames and acquires clock initial offset of each slave station equipment;

II) when initializing, the master station equipment reads the time value stored by the slave station equipment and calculates the transmission delay time;

III) in the initialization process, in order to quickly compensate the initial deviation of the clock, the master station equipment continuously transmits commands in independent command data frames after measuring the transmission delay time and the initial offset of the clock, so that the slave station equipment time is synchronous, and the initialization of the distributed clock is completed;

IV) in the periodic operation stage, the command is periodically sent along with the process data to read the reference system time, the reference system time is written into the slave station equipment, and the dynamic clock offset is compensated in real time.