A Slick Little Robot

By Harry T. Roman

	Some of the tanks that OTIS inspects are huge.

OTIS is a mobile robot, and I helped design it.

Actually, OTIS is just one of about twenty robots I helped create. CECIL crawls inside the dangerous reactor areas of nuclear power plants and submarines. RoBall can walk inside steel pipes and inspect them with a tiny camera. And SURBOT climbs stairs, guards high-security areas, and lifts heavy objects.

But OTIS is my favorite. It was the first robot I helped design, and now it is used all over the world.

OTIS is short for Oil Tank Inspection System. It is used to inspect oil tanks at refineries, power plants, and seaports. Those large, tuna-can-shaped tanks hold fuel oil for trucks, homes, and factories. The tanks are often forty to one hundred feet across and fifty feet high. Five to eight medium-sized houses could fit into one of these tanks.

The four-wheeled robot is lowered into an oil tank.

To make sure oil doesn’t leak into the environment, the tanks must be cleaned and checked regularly. The usual way of cleaning and inspecting the tanks creates problems. Draining the oil from the tanks is messy. Also, the people who climb inside the tanks to inspect them are in danger, even though they use special suits and breathing equipment. These inspectors sometimes must spend weeks doing the hot, boring work.

OTIS does the job in a couple of days, saving time and money. The oil tanks need to be drained only when OTIS finds a spot that has to be fixed.

OTIS’s Job
When we designed OTIS, our challenge was to create a robot that could clean the oil and inspect the steel floor of the tank while all of the oil was still in the tank! No one had ever done that before. Here is how we did it.

Our first problem was to choose the right material for OTIS’s body. Otherwise, the oil in the tank would harm the robot and possibly leak inside and destroy delicate electronic equipment. We used a strong plastic. Rubber seals between body parts prevented the oil from leaking into OTIS, even at high pressures. The pressure at the bottom of an oil tank is similar to being under tons of water.

Next, we made an important decision about how OTIS would move around inside the tank. There were two choices: Let the robot swim through the oil or roll along the bottom of the tank.

Since OTIS would need to bring vacuum hoses and electrical cables to do the job, we decided to lower the robot in through the opening at the top of the tank. We used magnetic wheels to attach OTIS to the metal tank floor. Having the robot crawling on the floor gave us a way to track where OTIS was at any time.

Seeing Through Oil
Next we gave our robot special camera eyes so we could see the tank floor. We designed lights that would allow OTIS to “see” through the yellow-orange color of the oil. These eyes show us the floor plus any obstacles that OTIS may have to avoid, such as devices that warm the oil in cold weather.

	A worker hooks up OTIS's hoses before the big job begins.

In OTIS’s belly, between his wheels, we placed a small but high-powered vacuum system. This device sucks up dirty oil that has sunk to the bottom of the tank. The dirty oil goes up one vacuum hose to the top of the oil tank, where a special filter removes the dirt. The clean oil then flows back into the tank through another hose.

The Robot’s Brain
Maybe the hardest part to design was OTIS’s “brain.” We had to solve the problem of how OTIS could check the metal floor of a tank for cracks, holes, or other problems.

We used high-pitched sound waves called ultrasonics. We cannot hear these sound waves. They are beyond the range of human ears. Like a bat hunting for insects, OTIS uses ultrasonics to read the surface of the metal. Common bats of North America hunt by sending out squeaks, which bounce off objects and return to the bat. A bat can tell where an insect is by how long it takes sound waves to bounce off that insect and enter the bat’s ears.

OTIS crawls along, inspecting the floor of an oil tank.

In a similar way, OTIS gets information about the floor of the oil tank by sending down sounds that bounce off the floor back to the robot.

OTIS is constantly sending information by sound so that the person operating the robot can tell where it is and what it’s doing. OTIS’s location is shown on a screen. As OTIS gathers information about the floor of the tank, that information also shows on the screen. The good areas of the floor appear as green, and the bad areas are shown in red.

Whenever I see those large tanks I think of OTIS. I wonder where he is, helping to keep the environment clean and humans safe from dangerous work. Now there are more robots like OTIS, doing the same kind of work. I wonder what their names are!