Problem Definition

Up to date, nuclear reactors are still a promising source of energy for many countries worldwide. With more than 400 nuclear power plants currently in operation, and each requiring approximately 44 miles of piping, it becomes tremendously painstaking and time inefficient for regular and manual examinations of the pipelines

A nuclear power plant has requested specifically for an autonomous machine capable of scanning the outer surface of the pipes for any potential signs of radioactive material accumulation and recording the locations of the spots. A minimum of three spots need to be detected for a 120 inch pipe.

Roboko is an autonomous robot designed to accomplish the aforementioned task.

Design Solution

The project is divided into three subsystems: electrochemical, circuit and microcontroller. I was in charge of the circuit component. I designed all electronic interfaces to connect the sensors and actuators to the microcontroller board, specified power requirements, performed voltage and current calculations and soldered all circuits.

Roboko is constructed from three layers of hardwood held together by four angled titanium beams at its corners. Its arm is in form of a “crab clamp” mechanism, which can open up upon detecting a pipe support by an IR sensor. To report the position and number of black spots, 16 IR sensors are evenly spaced apart and mounted on the ring to detect black spots that randomly distribute along the pipe. Upon detection, a buzzer will sound, and the black spot’s position (including distance and radial component) based on the IR will be recorded.

Growth

Having limited knowledge on circuit analysis and structure, I picked up several important skills from this project. I was able to analyze voltage and current signals and take into account real-world factors to select components that meet the power rating requirements, build from circuit schematics and solder the components, and explore alternative design solutions when a challenge is faced.

One of my tasks was to design a buzzer for indicating when a black spot has been detected. When I connected it to a signal pin from the microcontroller and ground, I noticed the sound is very faint. I investigated the cause and realized that the current provided by the microcontroller board was too low. I researched on current amplifiers and connected the buzzer to a NPN transistor, which allows current to be amplified when a low current is recieved, and stays as open circuit when there is no signal.

I was also exposed to complex integrated circuits and electronic devices. For example, to solve the issue of the lack of pins on the microcontroller to receive 16 IR sensor signals, I proposed using a 16-to-1 bit multiplexer. A multiplexer allows one to know precisely which one of the sixteen terminals is receiving a signal of 1 based on the 4 bit binary number at the output. This can be used to assist the team in locating the radial position of the spot on the pipe.

Conclusion

The project had been a satisfying experience. I was exposed to the electrical side of a design and how it is integrated with software to control a robot. I recognized the value of teamwork and people with various talents and backgrounds to design a robot. Cheers to my team. The accomplishment would not have been made possible without them.