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Underwater Walking Robot - Crabster CR200

The underwater walking robot named Crabster CR200 is developed by researchers at the Korean Institute of Ocean Science and Technology (KIOST). The task of the Crabster CR200 is to inspect the seabed structure and shipwrecks off the coast of Korea Peninsula. This summer the robot will explore wrecks despite the powerful surge of tidal current.

The CR200 has 6 legs for mechanical contact with seabed and like its biological cousins, the forward 2 legs also work as robotic arms for underwater manipulation. It can pick up objects and store them inside a frontal compartment. The Crabster is equipped with 10 optical cameras and a long-range scanning sonar which scans up to 200 m (650 ft) away, so the robot is able to perform the precise inspection and manipulation in a low visibility environment.

The CR200 endures the tidal current by controlling the posture of its body and legs. Researches used computer simulations to streamline the robot's main shell, that improves the stability:

The numerical simulations were performed for the evaluation of current loads acting on the CR200 with a variety of incident angles using ANSYS-CFX package. The Reynolds-averaged Navier-Stokes equations were solved to simulate the fluid flow around the CR200 to calculate forces and moments induced by incoming current with angles.

The robot is powered through an external power cable and it can operate under water for more than 24 hours

Let us see, how its first major underwater test looked. Test took place at KIOST's South Sea Research Institute, located in Geoje City, South Korea. The robot's weight is 600 kg (1322 lb) and in total it is 2.42 m long, 2.45 m wide, and 2 m high (7.9 ft x 8 ft x 6.5 ft). The robot and its remote control station were designed to be easily transported in a pair of shipping containers.

Four people remotely control the Crabster CR200 from the control station inside the shipping container. The pilot controls the robot's walking and posture. Manipulators, cameras, and lights are controled by a co-pilot. A sonar engineer monitors the scanning sonar and other sensors, while a navigator plans its movement and keeps track of its position.
Robot's equipment is shown in the figure below. It's equipped with i.a. an acoustic camera, acoustic doppler current profiler, high resolution scanning sonar, and several contact force sensor.

The Crabster performed well during its first dive. Bong-Huan Jun, a principal research scientist at KIOST, said:

I was very excited, but on the other hand I was nervous during the test. There are many mechanical and electrical parts inside the legs, such as the electrical motors, reduction gears, amplifiers, and interface boards. If even one sealing is faulty, seawater will enter the container which could cause shorts and corrosion. Any single minor problem would require a long time to fix.

Here is the video of the first major underwater test at KIOST's South Sea Research Institute:

The Crabster CR200 team includes researchers from five universities:

  • Seoul National University of Science and Technology developed the gait algorithm, using Little Crabster as a test-bed;
  • Mokpo National University performed hydrodynamic analysis and estimation of current load on the robot;
  • Chungnam National University helped with optimal joint path planning for swimming motion;
  • Pukyong National University studied how to implement fault tolerance gait;
  • Kookmin University contributed with numerical modeling and simulation of the robot.

The video below shows the robot's standing-up posture. The Crabster CR200 is a really big robot.


Anonymous said…
Nice mechatronics project. Very complex from technical point of view.

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