Implementation of remote access to the technological system for formation of islet thin films
methods allow to control processes, to operate equipment with the use of network technologies
and to provide, if necessary, the operation without operator intervention.
However, currently there is a number of tasks, when the presence of the operator near the equipment is nondesirable or unreasonably. This may be related to hygiene of work, harmful factors of production, the experimental studies on unique equipment or training. All these tasks can be solved by the remote access to technological equipment.
Remote access on the one hand allows to move people away from areas where his presence is undesirable or dangerous, and on the other hand gives the opportunity to expand the circle of potential users of the unique scientific equipment, the acquisition of which is impossible or impractical.
This paper describes a system of remote access to equipment, developed at the department of Electronic Technologies in Mechanical Engineering of the Bauman MSTU in framework of the state contract No. 16.647.12.2018 of November 25, 2010. Remote access is implemented for modular vacuum facility for formation of islet thin films .
Practical value of project consists in the fact that the remote access allows a user who does not have high computational power and technical capabilities, to conduct experiments on the formation of islet thin films and nanostructures with use of any computer that has Internet access.
During the expert analysis of the situation in the field of design and use of the complexes of remote access to laboratory equipment, it was determined that the most developed area is associated with providing remote access to measurement tools, different kinds of microscopes. The feature of providing remote access to measurement tools is the integration of developed specialized software with the module for remote access via the Ethernet channels and the Internet, and the interaction with teaching materials, allowing the use of such complexes in the educational process.
Remote access to other research equipment, in particular, to a vacuum processing units, at the beginning of the project had not been realized, so in the course of the project it was necessary to solve following tasks:
Logically partition the hardware into subsystems: technological, energy supply and service.
Development and formalization of the algorithms of technological processes.
Development of the control system that ensures full control and management for all hardware subsystems, including power electronics.
Development of specialized software that allows the user to connect to the control system via communication channels for monitoring and control of ongoing processes.
Development of user interface that is intuitive and easy with one hand, and allows complete control of the equipment on the other side.
All these tasks were successfully solved.
In the framework of project, we developed an interactive educational-scientific complex [1–3], a universal solution for remote access to equipment. Technically complex consists of the unit for formation of islet thin films and nanostructures, system of automatic control and information unit providing an information environment for teaching and research of coating processes via remote access.
The model of remote access implementation is shown in Fig.1.
The complex consists of the following main components:
modular system for formation of islet thin films;
hardware complex, providing the functions of the automatic control system and her connection with the software for remote access;
specialized software tools to provide access to the equipment via the Internet.
Functional structure of the educational complex provides the basic methods of formation of thin-film nano-structured coatings: thermal evaporation, magnetron sputtering, arc discharge and chemical vapor deposition.
Vacuum system for forming a thin-film coatings consists of the following main elements :
vacuum subsystem including a vacuum chamber and means to ensure vacuum;
system for fixation the samples within the vacuum chamber;
system for supply of working gases for the necessary technological environment;
technological system consisting of sources of materials for forming coatings, and of power supply;
energy system to power the equipment.
Each of these subsystems is logically complete and may be subject of control independently of the other. However, for automation it is necessary to consider the restrictions that are initial conditions for start and stop processes. For example, you cannot start pumping if all the necessary flanges are not installed on the vacuum chamber.
Despite the fact that in  for formation of islet thin films as a result of the analysis the methods of thermal evaporation and magnetron sputtering are chosen, the developed educational and scientific complex allows to use four main technological methods: thermal evaporation, magnetron sputtering, arc vaporization and chemical vapor deposition.
Each of these technological methods is performed in the same manner:
to set the sample on the substrate holder, and then put the last into the chamber;
to set the necessary technological source;
to pump out the vacuum chamber to limit pressure provided by vacuum system;
to turn on the flow of the working gas and to set the pressure in the chamber in accordance with the requirements of the technology;
to turn on the source of material and bring it to operating mode;
to open the flap;
to form the coating with control of process settings;
to close the flap;
to turn off the source of material.
to turn off gas and vacuum systems;
to fill the chamber with atmosphere;
to remove the substrate holder and to retrieve the sample with applied coating.
The coincidence of algorithms of formation of the coating made it possible to simplify the control system. For different methods of coating, the differences consist only in the implementation of the management subsystem for power supplies of technological sources. Each source has its own power supply and management, which is responsible for communications with the control system, at the same time being a link between the controller and the technological source.
It should be noted that some operations, such as installation of sample, the substrate holder and source, may not be performed in the automatic mode, and require operator’s assistance. In the framework of this project it is not a problem, but for industrial equipment can be solved using automatic loading systems.
The control system is implemented on the basis of industrial controller, a feature of which is the interface for connection with the local computer network using TCP/IP for data transmission. Data exchange with the controller can be implemented by industrial MODBUS protocol.
The control system completely automates operation of a vacuum subsystem. To start pumping the operator should give the command and wait for reaching the maximum pressure. However, if necessary the pumping can be performed in manual mode. In this case, the operator command to switch on the pumps and to open or close valves as necessary.
Since the main purpose of the facility is to conduct experimental research or laboratory works, the process of forming the coating wasn't automated. This makes sense only for industrial equipment when the technology is proven, and requires the reproducibility of the produced coatings from sample to sample. Thus, in our case, the formation of the coating is fully controlled by the operator-technician in semi-automatic mode. The operator can set the desired pressure in the vacuum chamber or the flow of gas, set the voltage at the sources or the required current value. Maintenance of preset values will be undertaken by a control system.
One of the important functions of the control system is the control of correctness of actions of the operator. For example, the control system will not allow to set a value of the working gas flow, which will increase the pressure in the vacuum chamber above the operating pressure of the turbo pump. On the one hand, this protects the equipment from damage due to improper actions, and, on the other hand, the warning messages can be used for learning correct methods of working.
In addition, the control system have emergency stop function, which guarantees the safe shutdown of the equipment, which prevents its failure.
REMOTE ACCESS SERVER
To provide remote access to equipment the special software, the remote access server, has been developed. A general scheme of the remote access is shown in Fig.2. The automatic control system is connected to the remote access system through the driver [1, 2]. The latter is an intermediate link between the equipment and the remote access server. It has a specification of the formats of controlled signals, through which interact with the remote access system. Implementation of interaction with the automatic control system is hidden inside the driver.
This solution allows to connect virtually any technological equipment with control system by developing the driver corre-sponding to the specifications of the remote access systems without changing the functionality of the software of the complex. Instead of real device the virtual simulator of equipment, which is also connected via the similar driver, can be used. A virtual simulator allows to fully simulate a job, giving the user the feeling that he is working with real equipment. This option doesn't demand the presence of an operator, allows to conduct at the same time several virtual experiments and can be used for the educational purposes.
When working with equipment in the remote access mode in real time and in virtual simulator mode, the same techniques and algorithms are used with the exception of manual operations, for example, of installation of the substrate. For such operations the simulator just gives a signal about readiness of the equipment to job.
In fact, by the remote access server you can connect the required number of virtual simulators or facilities. Their number is determined by the power of computing means and the of data channel.
The remote access server, on the one hand, interacts with hardware through drivers, and on the other hand accepts client connections from the external network. In this project we used a two-tiered approach to creating a system of collective access to the resources of the laboratory. The first level is access to the hardware of a virtual laboratory via the local network of the university, the second one – access via the Internet.
Educational-scientific complex can operate in three modes: in the mode of directive management, of remote access in real time and in virtual simulation mode.
In the directive management mode, the user works near the equipment independently carrying out all actions. In this case, the algorithm and methods of cooperation with educational-scientific complex are the same as during the work with any other processing equipment.
In the remote access mode in real time the user controls the equipment via a LAN or the Internet. In this case the operator’s presence near the equipment is necessary for manual operations. In emergency situations or in case of loss of communication with the user, the operator can work with the system in the directive management mode.
If in the directive management mode the user can use the controls, located directly on the power supply units, in the remote access mode all actions are carried out only through a personal computer with installed software. Any command received remotely, is processed by control system, checked for the correctness of the action and passed to the appropriate subsystem of equipment.
In the virtual simulator mode, as noted above, the user interacts with the simulator of equipment, and the presence of the operator is not required. Connection of several users for carrying out a virtual experiment is possible.
In the remote access mode connections are made without use of web servers directly to the remote access server. To connect, a special program is needed – a thin client. This solution allows to reduce the server response time and provides the control of the equipment, which is the most approximate to real hardware control. The term "thin client" means that all the logic is moved to the server program (on this principle are based all web browsers).
After connecting, the server sends to the client program a description of the available signals for monitoring and control of equipment, and each signal is associated with the description of a typical display item or control. For control signals it can be a numeric or pointer-type indicators, displays. For control the buttons, panels of input of numeric data or simulators of elements like controls sliders or control knobs are used. All controls have physical analogues used in the real control panels for equipment – that promotes intuitive understanding of the interface.
The transfer of forming the user interface on the backend allows to use a common client program for various types of equipment. In addition, in the case of modification of the server interface will be updated automatically for all users who use this equipment. The principle of formation of web pages in Internet is implemented similarly: changes made on the server are available to all users regardless of which software they use.
The interface of software of the educational-scientific complex allows the client to carry out experiments and research of process of formation of thin-film coatings (including of islet nanostructures). The remote access server is configured for sharing with the technological vacuum modular system.
Logically, the user interface is divided into three sections (bookmarks): management of the preparation of the unit to experiment, control of the pumping system and management of technological sources.
Interface of preparation to experiment allows to control the installation of substrate on the holder, of substrate holder into the chamber, selection and setup of technological source.
The interface of vacuum control system allows to turn on the pumping process, to turn on and regulate the flow of the working gas and to control the pressure in a vacuum chamber. For better visualization of the pumping process the mimic diagram of the vacuum system where colors show the turned on items and involved vacuum lines is used. The interface of vacuum control system is shown in Fig.3.
The control interface of the technological subsystem allows to turn on sources of material, to adjust its parameters, and to control the flap, which cuts off the flow of material to the substrate from the source. For control of the growth process of islet thin films, a display window of the tunneling current arising in the applied coating is provided. This allows during the coating process to control the coating thickness, size of islets and degree of surface filling. Interface of the window for sub-system control is presented in Fig.4.
In the project, an original method for providing remote access to process equipment is developed. Suggested methods allow to control processes, to operate equipment with the use of network technologies and to provide, if necessary, the operation without operator intervention.
Developed educational-scientific complex can be used not only for student learning but also for research and development of technologies. The training and demonstration of the four most common methods of formation of nanostructured coatings in a vacuum, testing of technology and selection of modes for the existing methods without loss of production are possible.