Converting electric tractors to autonomous systems

Founded in 1985 by Ewald Schiller, Schiller Automatisierungstechnik has developed into a company with more than 240 employees in Osterhofen, Metten, Grafenau and Shenyang, China. Electrical, mechanical and IT systems for automation, logistics, cleanrooms and electrical planning are among the company's core competencies. Schiller laid the foundations for the development of solutions for autonomous tugger trains in 2018. "It quickly became clear to us that safety technology would be a key issue for our driverless transport systems, because with tugger trains, as with operation with trailers in general, the trailers' lane departure is an important problem to solve," says Peter Stoiber, Head of Mobile Robotics at Schiller, explaining one of the challenges during the development work.

The engineer and his team also had to calculate the error probability of all components and ensure maximum availability in order to comply with the strict machine guidelines. The development work led to the perfection of an indoor GPS, with the help of which the tugger train always recognizes where it is. This means that no structural changes are necessary for orientation during transportation. Each Schiller tugger train can also be easily adapted to changing situations in the production process and can also be used at other locations. The biggest advantage of the solution is that commercially available electric tugs can be converted into autonomous systems using Schiller technology.

The task: Fail-safe electronics

Even if the tugger trains can still be operated by the driver after being fitted with the conversion kits, the autopilot shows its strengths in everyday use. For example, when the tugger train arrives near the next work station, a smartwatch on the wrist of the employee in charge reports the status via a vibration alarm. The employee can then load or unload the wagons and give the signal "All actions completed, send train on". In this way, the route is continued without delay. Unnecessary travel times for staff are eliminated. One of the last problems in the development process that Peter Stoiber, as Head of Mobile Robotics, had to face with his team was that the train sometimes has to travel on uneven tracks or cross building corridors on the many different routes through the automotive plant. These are potential hazards that could jeopardize the reliability of the electronics. It was therefore important to prevent the control cabinet from vibrating. To achieve this, the tugger train was to be fitted with vibration dampers at the critical points.

As with all electronic and mechanical components of the system, Schiller Automatisierungstechnik analyzed and tested the potential solutions in great detail. The design department identified ACE shock absorbers as the ideal solution partner. "ACE initially impressed us with its large selection of suitable components, and we were able to configure and calculate the vibration dampers on the ACE website," Stoiber recalls. "ACE's sales department then responded very quickly to our inquiry and convinced us with a sample. This gave us additional confidence in the quality and durability of the proposed solutions." Based on the key data of the maximum speed of 10 km/h and the control cabinet weight of 50 kg, four rubber-metal isolators of type AAM-52205 were determined. This family of maintenance-free and ready-to-install vibration dampers is designed to absorb loads between 0.5 and 22.7 kg. The small shock and vibration-isolating connecting elements therefore help to effectively protect lighter components. They isolate in all directions and can be mounted in any desired spatial axis and used for loads in the push, push and pull direction. Made of galvanized metal and with rubber components made of neoprene as standard, they are also available from ACE with highly damping silicone for special applications against heavy impacts.

Even though they are being used for the first time in their standard version on driverless transport systems in the logistics sector in the application described here, vehicle technology has long been familiar territory for these machine elements. ACE customers around the world use them to protect against shocks and vibrations in lighter electronic systems and components, including in off-road vehicles and trucks, which have always been steered by humans to date.