Mobile Manipulation Software Systems
Published At 2014-10-11 15:09:05, By Devon Ash
Robots can do what we can do. But better. At least that's what the romantic vision of a robot leads us to believe. There are toy robots that do one repeated action like waving. There are military robots that carry out autonomous missions. They operate on every level of commercialization and have been an avid force in the manufacturing of low-cost materials since 1938. In 1938, it was a crane-like device powered by a single motor and it had 5 degrees of freedom. It was able to stack objects using pre-scripted motions and timings. In 1961, it was the first industrialized robot that happened in the world at the assembly lines of General Electric. Today, the world has bi-pedal autonomous humanoid robots. Autonomous vehicles of all shapes and sizes. In all parts and configurations. And they're even available with any attachment you can imagine: cameras, gps, flamethrowers, gas meters, inertial measurement units, machine guns, lasers, beer, and sometimes even children.
In this introduction to robotics, to narrow things down, I give a bit of background knowledge on the components that will make up the PR2. The PR2 (Personal Robot 2) is an extension of the PR1 developed at thourough by Willow Garage. It was a landmark in robotics, being a very thorough mobile manipulation research platform that uses ROS. Coupled with the course "The Robot Operating System I" you will find great success in learning how to participate in robotics. The PR2 is what is known as a "Mobile Manipulation Humanoid" robot. It has all the functionality of a human, but with a mobile base it solves the problem of having to deal with the dynamics of walking and incorporating that into the rest of the system. Robots like Boston Dynamic's Atlas and the RoboCup Large Size Soccer platform are more interested in the dynamics of walking and balancing.
A is the PR2's head, nicknamed its sensor suite. However, it was almost immediately outdated when the Kinect 1 came out and now it is significantly outdated now that the Kinect 2.0 is out. For our robot at Open Robotics, we will be using the Kinect 2.0 now that there is a driver available for it. B represents the laser range finger the PR2 uses to create its forward point cloud. Point clouds are arrays of 3 dimensional points that have color information as well. They can be used for depth perception and to solve various computer vision tasks. ROS entertains The Point Cloud Library on all of its robots. C points to the robot's right arm. On the PR2, both arms are identical in software and in hardware. It is a 7 degree of freedom manipulator with a grasper. In prior versions of ROS, the PR2 used the arm_navigation stacks along with the pr2_arm_navigation specific implementation to achieve its manipulation goals. Now, with the release of Sachin Chitta's MoveIt! the pr2 does its manipulation using the moveit_pr2 software suite. The Open Robotics robot will also be using MoveIt to control the arms and manipulate objects.
And finally, E represents the mobile base. Our robot has a mobile base that has a software implementation almost identical to the pr2's except for its driver/controller configuration.
A mobile manipulation robot contains all of the necessary things to be a complete robot and so the PR2 will be a great platform for demonstrating the concepts necessary to understand how to build one. The PR2 lacks one thing: legs. However, if one wishes to learn about robotic legs and the dynamics of that, it would require long tedious hours of sorting through papers as the research is still deeply in-progress. The PR2 does have however: robotic arms, a robotic head, an extensive sensor suite, mobility, and the utmost requirements for learning and teaching: it's free, it's accessible, and everyone can own one in simulation (The PR2 Simulator). That being said, this series of tutorials will cover (from a software perspective) how to integrate and build a robotic arm, a robotic head, incorporate an extensive sensor suite, make it mobile, and glue it all together (all of the components needed to officially declare the PR2 a mobile manipulation robot)