Servo - July 2010

GEERHEAD

The latest Aqua robot with rubber treaded legs for walking. Here, a human operator tethers the robot with a cable for remote communications and manuevers. The researchers have just completed development of a set of six all-purpose legs [not shown] for land and sea so they don’t have to change the robot’s legs to go into the water from the shore.

models, the older models are still useful and can sometimes be upgraded. “We try to back port new technologies into older models when possible, but that is not always possible,” says Dudek.

Speaking of new technologies, the greatest advancement is the new smaller, sleeker body design which allows the robot to operate more quickly. Researchers can also pack it into a single pelican case for easy stowage on planes for flight to remote water destinations.

The computers are also faster and higher performance, as are the cameras. The Kroy has two computers inside and uses three cameras which study the environment and help with navigation. Two of the cameras face forward, the other one is in the back.

The robot’s software — RoboDevel — runs on a real-time operating system called QNX. This software generates the different gaits or strides the robot needs to employ on land and under water. It also operates the servo software.

The robot’s many gaits include one for very fast strides that are unfortunately not energy efficient, and others are for turning, moving laterally, and so on.

The robot’s legs store spring energy when they bend under a load and this energy is released as the legs push forward. This is a critical part of the robot’s locomotion strategy. When the robot weighs down on the legs, the compression of the spring stores energy that is released, aiding forward movement.

“The swimming and walking functions are implemented as RHexLib modules. A visual processing module for Aqua is being developed with VXL as the vision library,” according to Dudek.

The robot actually runs two operating systems. One of the computers runs Linux and one runs QNX (which is similar to Linux). The computer running QNX moves the legs and tracks their motion. When the robot transitions from water to shore, it is crucial that the timing is accurate when changing gaits. The Linux operating system manages diver-following and long-term planning by the robot.