Self-Calibration of Eye-to-Hand and Workspace for Mobile Service Robot

Background

Distributed Vision System (DVS), a particular example of sensor network, consists of physical vision agents monitoring the working environment (Ishiguro, 1997). The vision agents connect with each other through computer network or are controlled by central computer. The concept of distributed vision system can be applied to construct a wide area surveillance system for human tracking (Atsushi et al., 1998; 2002), a robot indoor navigation system (Ishiguro, 1997; Nakazawa, et al., 1998; Sogo, et al., 1999), or a non-specific target tracking system (Takashi & Norimichi, 2002).

Positioning in three-dimensional space is an important technical issue in many industrial and commercial applications. Specifically, noncontact measurement of the rough surface of a target is useful in many industrial occasions because it is convenient and non-destructive. Distance measurement device based on laser diode technology can provide precise measurements. This kind of measurement device is called laser distance sensor or laser range finder. Laser distance measuring method can be technically divided into three categories: interferometry, time-of-flight, and triangulation and each of them have advantages and limitations (Amann, et al., 2001). A robot arm equipped with a 2-D laser range finder can take dimensional information of the target while adapting its view in applications such as 3-D scanning (Soucy, et al., 1998; Lamb, et al., 1999). In some applications where target locations (points) in space relative to the robot arm are required, it is sufficient to use a 1-D distance sensor mounted on the end effector. Usually a 1-D laser distance sensor with a visible laser light is able to serve the measurement purpose. In such a sensing system, the factors causing the systematic errors include imperfect position and orientation arguments of the laser distance sensor. Since the accuracy of such measurement system is influenced by the precision of installation parameters, the calibration is essential and critical.