Robots are finding their way into more and more areas and, as research progresses, they are also becoming more widely accepted. Robotics is already an integral part of teaching within the Measurement and Sensor Technology division in the Electrical Engineering and Information Technology (Etit) department. Learning and research are carried out, among other things, using a conventional modern industrial robot, which, with accessories, costs around 100,000 euros. Several robots would be required for use by all of the students for practical training, final dissertations and seminars. This means that the demand for robots for practical teaching is high, as, unfortunately, are the costs.

It is good if the expertise and enthusiasm for developing such robots can be found among the students themselves: In his bachelor thesis, Felix Herbst developed a functional six-axis articulated-arm robot and manufactured it in an innovative way. This robot, which is largely 3D-printed, has a span of 43 centimetres, making it considerably smaller than the industrial robot at 80 centimetres, but can be programmed in the same way and is equipped with modern sensor technology to autonomously determine the position of the individual axes. Cost: just 600 euros. “My motivation was to design a cost-effective robot arm as an alternative to the existing industrial robot,” says Herbst.

A six-axis articulated-arm robot...

He succeeded, but more than that: His robot is flexible and modular in its application. To this end, he used CAD (computer-aided design) applications to produce a technical drawing. Then one layer after another was applied using fused deposition modelling. Herbst’s robot is not only cheaper, but also easy to reproduce and more versatile than the industrial model. “While many manufacturers like to use closed systems which then cannot be changed by the user, I made sure that the electronics and interfaces were designed to be expandable and not limited to the current measured values and commands.”

...equipped with an independent motor control circuit board...

And so the in-house robot is in no way inferior to the industrial robot in terms of electronics. On the contrary: “Each of the six independent motor control circuit boards is equipped with a microprocessor, a motor driver, a magnetic encoder for zero-point positioning and a CAN (Controller Area Network) interface,” explains Sven Suppelt, who developed the robot’s electronics alongside his Etit master’s degree and his work on the TU spin-off ‘core sensing’. “You could say that we are bringing the intelligence of motor control directly to the motors.” The robot can thus be controlled with considerably fewer cables, and integration density is increased. In close cooperation with Felix Herbst, he took a step-by-step approach to continuously optimising the circuit board.

...and a needle with an integrated force sensor...

This robot can now perform various movements and be used for different applications, such as in medicine. Equipped with a hollow needle with an integrated force sensor at its tip, which was developed by Sonja Wismath in her bachelor thesis in the Etit department, the robot is used as a surgical assistant and for automated needle injections. The forces generated by the interaction of the needle tip with the surrounding tissue can thus be measured. “These forces can be presented to the doctor in a more detailed way both during treatment and in a training scenario. This sensitises the doctor’s haptic perception,” says Wismath. This enables more precise needle insertion. Romol Chadda, a PhD student in the Measurement and Sensor Technology division and, together with Jan Hinrichs, the supervisor of the bachelor thesis, presented the needle at the IEEE Sensors Conference in Canada this October: “The reactions were very positive. Biomedical engineering has always been a relevant aspect of research, as it is directly related to the well-being of mankind and can significantly improve quality of life. Recent innovations and technologies are now enabling greater progress in this area. Many of the reactions have encouraged us to continue research.”

...becomes a surgical assistant.

The robot equipped with this hollow needle thus becomes a surgical assistant, which is used for the practical experiment “Biomedical engineering – the robot as a surgical assistant” in the Biomedical Engineering cooperative degree programme. In medical robotics, the operating doctor still has control over the activity to be performed and is merely supported by the robot. “The biggest challenge will be to optimise robots to such an extent that they can collaborate with other people,” says Dennis Roth, also a master’s student in the Etit department and supervisor of the practical experiment. The students should fundamentally be introduced to the use of robot operating systems during their practical training and various terms from robotics should be explained. They also learn how medical robots can be used for needle biopsies. “The students will be made aware of the difficulties that can occur and that such a needle insertion is not quite as trivial as it may initially seem.” The special thing about it, however, is “that the robot developed by Felix can be made available to many students without great expense. It allows one’s own codes and one’s own program sequences to be tested safely, meaning that the inhibition threshold in handling is much lower.”

Enthusiasm for one’s own subject

And to allow this highly interdisciplinary project to also be applied from the coming summer semester, Felix Herbst is working on reproducing the robot as part of the project seminar PEM (practical development methodology) in the specialisation Sensor, Actuator and Electronics (SAE). “In addition, I am currently experimenting with new drive concepts that should make the robot even more precise and cost-effective. In parallel, I am working on expanding the software functionality. I would like to integrate additional sensors and motor controllers, which will then offer new possible uses.”

Asked about their motivation, all gave similar answers, namely enthusiasm for their respective specialism. Felix Herbst: “Robotics for me combines software and hardware in a meaningful way. I like programming and see a physical result straight away when the program works. I am simply fascinated by automation and man-machine interaction.”

Professor Mario Kupnik, Head of the Measurement and Sensor Technology division, supervised, coordinated and brought together the individual projects. He is fascinated by the outstanding cooperation among his students: “From scratch, our students have developed a very impressive robot that is now available to the next generation of biomedical engineering students, as well as students of electrical engineering, mechatronics and computer science, and significantly improves their practical training. This speaks for the quality of our research-led teaching and the high level at which our students are learning and already conducting research. This is one of the main reasons why I moved to TU Darmstadt at the beginning of 2015.”

The B.Sc. Biomedical Engineering degree programme is jointly sponsored by the Electrical Engineering and Information Technology department at TU Darmstadt in cooperation with the Faculty of Medicine at Goethe University Frankfurt (GU). Modules are thus taught both at the TU and the GU. Supported by the RMU Initiative Funding for Teaching, the TU’s Measurement and Sensor Technology division and the GU’s Institute for Diagnostic and Interventional Radiology (Professor Thomas Vogl) will collaborate to set up practical experiments in the field of medical robotics. The surgical robot will be used for this purpose.