Free Trial

Safari Books Online is a digital library providing on-demand subscription access to thousands of learning resources.


Share this Page URL
Help

Chapter 10: Safer and Faster Humanitaria... > STRUCTURE OF EXISTING EOD ROBOTS - Pg. 179

Safer and Faster Humanitarian Demining with Robots if the user is experienced he loses time and con- centration when he focuses on driving the robot instead of deactivating the explosive. In task space control, the wrist of the robotic arm is driven to the desired position via the control unit (Crane, 1998; Spong, 1989). In this process, the user moves the wrist in just one step. The robot moves to the desired position via the calculation made by the microcontroller placed on the robot and the joint angles for the desired position are achieved (McKerrow, 1991; Feng, 1993). The EOD robot designed and manufactured in this project can be controlled both in joint space and task space. The user selects the control mode from the menu placed on the control unit. Having both joint space and task space control allows the user more flexibility in controlling the robotic arm's movement. For instance, an obstacle might make it necessary for one joint to be at a more acute angle than what might be automati- cally chosen by the robot. In this case joint space control is more logical. There is one significant problem for this type of robot and that is the fact that the user looks at the explosive material through the camera. The object in the camera image is not the same size as the real object and depth knowledge cannot be retrieved since the system does not use stereo camera systems. This chapter aims to explain the state of the art in explosive ordnance disposal robots, their key features, the prototyping stage of an EOD robot, its control algorithms and the future of this type of robots. The EOD robots are different than the classical service robots since they are required to work outside and deal with rough terrain and meanwhile they need to be accurate to work on explosive materials. The prototyping stage teaches the researchers what does not work and with these valuable experiences, a better robotic system can be designed and realized. The control algorithms make the robot more user friendly and efficient. The properties which can be added in the future are also discussed to give a better understanding to the reader about the evaluation of this type of robots. STRUCTURE OF EXISTING EOD ROBOTS When the system components are considered; an EOD robot consists of 5 parts, namely: a mobile platform, a manipulator arm, an end-effector, a camera system, and a control box (not shown in the figure) (Figure 2). The EOD expert operates the robot remotely to deactivate the ordnance. The mobile platform carries the total system to the job site, next to the explosive material. Since the robot is used outside, it is mostly de- signed as a tracked vehicle, and even some ad- vanced systems use reconfigurable tracks to be able to better adapt to the difficult terrain and pass the obstacles easier. The mobile base speed, geo- metrical size or the weight of the robot is not important for military use and that is why the existing robots differ a lot from each other; base speed reaching up to 13km/h and total weight over 300kgs. The speed of the robotic system is not important since the distance traveled is mostly around 100 meters. The climbing ability and the balance of the base determine the perfor- mance of the robot. Having high traction capabil- ity and keeping the center of gravity of the base low, since this is the largest part of the robot mainly due to the batteries, make the base suc- cessful. When designing an EOD robot it is important to first understand the necessary components as well as the advantages and disadvantages to different configurations of these. The following gives a brief description of each part as well as parameters that need to be considered before designing an EOD robot. 1. One of the most important parameters for an EOD robot base is the climbing angle - be- ing at least 45º and the ability to function on 179