Mass-produced underwater vehicles

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There has never been so much human activity in the depths of the oceans. Several thousand meters below the surface, oil companies are prospecting for new deposits and deep-sea mining companies are looking for valuable mineral resources. Then there are the thousands of kilometers of pipelines and submarine cables that need regular maintenance. Not to mention the marine scientists who would like to be able to use robust devices to survey large areas of the ocean floor. All these applications mean there is a growing demand for underwater exploration vehicles.

To meet this demand, researchers at the Fraunhofer Institute for Optronics, System Technologies and Image Exploitation IOSB in Ilmenau and Karlsruhe have designed a powerful autonomous underwater vehicle (AUV) capable of being manufactured in large numbers. Companies have been using AUVs for many years in deep-sea exploration missions. These untethered vehicles glide independently through the water collecting observation data, and make their own way back to the research vessel. Up to now, these have primarily been custom-built and very expensive. They have complicated structures, which makes them relatively difficult to handle by the crew on board the research vessel; for instance, accessing the batteries in order to replace them. It takes one hour to read the many terabytes of observation data out of the AUV’s onboard processor. What’s more, many of these vehicles are so heavy that only specially trained operators can place them in the water using the ship’s winch.

Mass-produced underwater vehicles

CAN bus system prevents cable spaghetti

The IOSB’s AUV overcomes all of these problems and will be on display at the Oceanology International exhibition (Booth H600) in London from March 15 to 17, 2016. The vehicle called DEDAVE (Deep Diving AUV for Exploration) bears a certain resemblance to the space shuttle. The research team, led by project manager Professor Thomas Rauschenbach, has fitted it out with technologies not normally found in AUVs to date. To avoid the typical mess of cables, which was often a source of faults, they installed a CAN bus system like those found in every modern car. It consists of a slim cable to which all control devices and electric motors can be connected. “Many experts who visit our laboratory are amazed how neat and tidy DEDAVE looks on the inside,” says Rauschenbach. The advantage of having so few cables and connectors is that faults are avoided. New modules, sensors or test devices can also be connected quickly and easily to the standardized CAN bus. Batteries and data storage devices are held in place by a tough but simple latch mechanism, allowing them to be removed with a minimum of effort. There is no longer any need to download data from the processor.

Room for four AUVs in one shipping container

One of the strengths of the lightweight, 3.5-meter-long underwater vehicle is that it takes up very little space. Aboard a ship, AUVs are stored in standard shipping containers, which usually offer only enough room for one vehicle. “We, one the other hand, can fit four AUVs into the same container,” says Rauschenbach. “The advantage of having four vehicles available is that larger than usual areas of ocean can be surveyed in far less time.” Despite their small size, the AUVs still provide plenty of additional carrying space. The payload bay measures approximately one meter in length, which is sufficient for installing several different sensors for capturing ocean floor survey data.

The underwater vehicle is powered by eight batteries, each weighing 15 kilograms. A fast-release latch mechanism enables them to be removed and replaced with little effort. A fully charged battery holds enough power for up to 20 hours’ travel. The software for the sophisticated battery management system was specially developed by researchers at the Fraunhofer Institute for Silicon Technology ISIT in Itzehoe. In collaboration with the GEOMAR Helmholtz Center for Ocean Research, Kiel, and a Spanish research center, DEDAVE will go through deep sea testing off the coast of Gran Canaria in the coming weeks.

Prof. Dr. Thomas Rauschenbach:

“The underwater vehicle has already passed numerous different tests. Before it goes into production, it will now undergo several weeks of deep-sea testing off the coast of Gran Canaria.”

Underwater vehicle goes into series production

DEDAVE is the world’s first autonomous underwater vehicle to be developed from the outset with a view to series production. It will be manufactured by a company to be specifically created for this purpose as a spin-off from the IOSB in the first half of 2016. The series production of a product of this type requires that every single manufacturing step is documented in detail. This is the only means of ensuring that the trained workers can build the vehicles as on an assembly line. For this part of the project, specialists from the auto industry have been engaged to contribute their expertise in industrial manufacturing and the qualification of subcontractors.

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Lean commands for Industry 4.0

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Bosch Rexroth provides software development kit for the script language Lua for Open Core Interface

The engineering framework Open Core Engineering by Rexroth now also supports the script language Lua. This gives users another option for bringing more intelligence into production. The simple and understandable syntax of Lua has proven itself on a global level. Bosch Rexroth is now also making the advantages, which for example are used in controlling complex figures in computer games, available to the automation industry. Lua can be used to control robotics or program axial movements. The end user can optimize its machine program itself with simple software tools – without needing to program one single line of PLC code.

Boach Rexroth robotics OCE Lua
With the simple script language Lua, putting robots into operation is quick and easy with Lua

Lua is ideally suited for the use in small networked devices and control units, as the size of the script interpreter is very small – less than half of one megabyte. In modular production, Lua scripts stored on the component carrier via RFID chip can contain complete work instructions. Machines in a M2M network or higher-level product systems generate scripts independently in order to control other processes and machines – as a basis for integrated machine intelligence. In light of the diverse possible uses in the Industry 4.0 environment, Rexroth integrated the Lua interpreter into the Open Core Interface of its IndraMotion MLC control units. OEMs thus create solutions in a combination of Lua and PLC code, where the customer-specific components are integrated into the script. This significantly reduces the effort required for adjustment for technological development.

Easier programming and commissioning of robotics

The flexibility of Lua allows for user-specific command interfaces with which axial movements of robotics and other machines can very easily be defined. For example, Rexroth has a simple function library for the programming language Robot Control Language (RCL), which facilitates the transition. As a replacement for RCL, the control system IndraMotion MLC then uses the Lua script.

Today, design engineers no longer require elaborate tools and development environments to represent a pick-and-place process in Lua. They merely write a simple script in a common text editor, and then transfer the file to the control unit. Subsequent expansion stages then promise the browser-based editing and testing of the control unit’s integrated web server.

Once the application-specific PLC code has been shifted into simple, easily accessible Lua scripts, the logic becomes transparent, understandable, and adaptable for the end customer. With regard to fast commissioning, the end user quickly loads the script from the control unit into the text editor and completes programming of the axial movement. The service effort on site is also reduced if future adjustments are performed remotely by the customer or an engineer.

The software development kit (SDK) for the script language Lua for the Open Core Interface can now be downloaded for free from Rexroth’s engineering network. The Lua development toolkit (LDT), which is also available free of charge, serves as a development environment.