Donned in a gauzy dental gown, the PR2 robot lifts its left hand and grasps the mixing bowl placed in front of it. The robot’s right hand, equipped with a rubber spatula, shortly follows suit, veering inside the bowl and toward the mound of softened butter waiting inside. Then, in a concentrated and meticulous manner, the PR2 turns its head down toward the bowl, and slowly begins mixing the butter.
The process of creaming butter and sugar, mixing in a handful of dry ingredients and sprinkling in chocolate chips to make cookies is a recipe simple enough for most humans to follow, but for a robot it is a complex task that requires hours of hierarchical planning by roboticists and real-time planning by the robot.
Graduate student Mario Bollini, a member of Professor Daniela Rus’ Distributed Robotics Lab, has spent the past several months programming the research and development platform PR2 robot, developed by Willow Garage, to bake chocolate chip cookies from scratch.
“My task is to have the PR2 bake cookies all the way from locating the ingredients in front of it on the table to putting the cookie in the oven,” Bollini said.
While the project was originally intended as a simple introductory project, it has turned out to be quite challenging due to all of the nuances involved with programming a robot to follow a lengthy list of tasks, while also employing vision, object detection and executing controlled motions.
To bake the cookies, Bollini first has the PR2 examine the table using a laser scanner and stereo camera to locate the cookie sheet and butter. All of the other ingredients and supplies the PR2 identifies by color and size. The PR2 then follows a hard code of the recipe, from mixing the ingredients to scraping the cookie dough onto the baking sheet and patting it into a large cookie.
Graduate student Jenny Barry, a member of the Learning and Intelligent Systems Group led by Professors Leslie Pack Kaelbling and Tomas Lozano-Perez, is currently leading a team of under graduate students on programming the PR2 to wipe down the table and open the oven door, so that the PR2 can go from preparing the kitchen for baking by clearing off the work surface to placing the cookie sheet in the oven. To do this, she is employing a technique called hierarchical planning, a means of breaking down a larger task into smaller steps.
Bollini’s present task is recalibrating the PR2 to perfectly mix flour, sugar and butter, as dry beans were initially used to avoid messes. He is hoping to have the PR2 prepared to serve as a full-fledged chocolate chip cookie baker by next month.