Safe Development Environments for Radiation Tracing Robots

Safe Development Environments for Radiation Tracing Robots

Kai Borgeest (TH Aschaffenburg, Germany) and Daniel Kern (TH Aschaffenburg, Germany)
DOI: 10.4018/978-1-7998-0137-5.ch006
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Abstract

Robots can substitute for men in radioactively-contaminated areas. This is a suitable field to deploy robots for measurements, repair, or clearance, but development and test of such robots could be dangerous, because radiation sources need to be handled. To avoid these hazards in development or public demonstrations, safe alternatives to radiation samples have been sought using an already existing robot (EtaBot). One proposed solution is an optical substitution (“light follower”), the other one a fully-digital simulation of the contaminated area and the robot movement inside it using a hardware-in-the-loop simulator (HiL).
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Introduction

After a nuclear disaster (e.g. Chernobyl, Fukushima) or in some military scenarios, it is too dangerous for people to enter a contaminated area. This is a suitable field to deploy robots for measurements, repair or clearance. Several fully autonomous or remote operated robots have been already built for this purpose. Before operation the robot must be developed, built and tested safely for critical missions. So it is desirable to perform these activities without handling dangerous radiation sources. A further advantage of simulated environments is a higher flexibility. This paper describes two ways of safe development. For the work a self-built, wheeled, multi-purpose robot “EtaBot” has been used. Radiation tracing and optional radiation-based navigation have been implemented in ROS.

One simple way has been dubbed “light follower”. The radiation sensor has been substituted by a photo diode as a light sensor. For the light sensor an interface circuit emulates the signals which in true operation would come from the radiation sensor. The robot can run a given path and just measure radiation on this path, but additionally an algorithm has been implemented to follow actively the radiation source. In this mode a directive radiation source could be represented e.g. by a simple torch light, a distributed scenario by diffuse lamps.

A second, more sophisticated approach is a complete digital simulation of the contaminated environment using a hardware-in-the-loop simulator (HiL). This implies two technical core questions, on the one hand the representation of the contaminated environment and the robot motion in the HiL, on the other side the interfacing between the robot and the HiL. Depending on the interface further functionality needs to be implemented in the simulator. In the particular case of this article, the robot has been reduced to its computation platform. The ROS computer receives radiation signals from the HiL, passes motion commands to an additional microcontroller board which would control steering and the motors. The robot is jacked with its wheels free from ground, the PWM signals are intercepted and fed into the HiL to simulate the robot motion, its location and posture in the contaminated environment. With a graphical map creator, scenarios can be defined and uploaded to the HiL. Radiation exploring robots and the presented approaches are good examples where deep interaction of mechanics and electronics (mechatronics) solves problems (Habib, 2007). A very similar application is exploration for chemicals where sensors may be more complicated, but exploration is easier, because in contrast to the stochastic nature, chemical sensing delivers continuous values (Ishida, 2012).

Key Terms in this Chapter

Geiger-Müller Tube: Tube in which ions are generated by radioactive radiation. An applied voltage causes a measurable discharge.

LiDAR: Light detection and ranging.

AD Converter: Converter from analogue signals to digital signals for further processing in the controller.

Transceiver: Transmitter and receiver, an integrated circuit which physically attaches a controller to the CAN bus.

PXI: PCI eXtensions for Instrumentation, a PCI based backplane bus.

WLAN: Wireless LAN (Local Area Network).

ROS: “Robot Operating System”, a platform for robotic applications.

CAN: Controller Area Network, a digital bus which is common in many industries such as automotive industry.

Radioactivity: Nuclear decomposition releasing radiation.

INES: International Nuclear and Radiological Event Scale (7 is the maximum category of nuclear accidents).

BLDC: BrushLess Direct Current, BLDC motors are supplied with DC, but run internally with multiple phases.

PWM: Pulse Width modulation.

HIL: Hardware in the Loop.

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