Nonholonomic camera space manipulation using cameras mounted on a mobile base

摘要

The body of work called "Camera Space Manipulation" is an effective and proven method of robotic control. Essentially, this technique identifies and refines the input-output relationship of the plant using estimation methods and drives the plantopen-loop to its target state. Three-dimensional "success" of the desired motion, i.e., the end effector of the manipulator engages a target at a particular location with a particular orientation, is guaranteed when there is camera space success in twocameras which are adequately separated. Very accurate, sub-pixel positioning of a robotic end effector is possible using this method. To date, however, most efforts in this area have primarily considered holonomic systems. This work addresses the problemof nonholonomic camera space manipulation by considering the problem of a nonholonomic robot with two cameras and a holonomic manipulator on board the nonholonomic platform. While perhaps not as common in robotics, such a combination of holonomic andnonholnomic degrees of freedom are ubiquitous in industry: fork lifts and earth moving equipment are common examples of a nonholonomic system with an on-board holonomic actuator. The nonholonomic nature of the system makes the automation problem moredifficult due to a variety of reasons; in particular, the target location is not fixed in the image planes, as it is for holonomic systems (since the cameras are attached to a moving platform), and there is a fundamental "path dependent" nature ofnonholonomic kinematics. This work focuses on the sensor space or camera-space-based control laws necessary for effectively implementing an autonomous system of this type.