Selection of Obstacle Avoidance Behaviors Based on Visual and Ultrasonic Sensors for Quadruped Robots

Robots are indispensable today to improve process efficiencies and labor savings in the industry and service sector. The importance of robots has also been recognized for work in critical environment, such as, space, ocean bottom, power plants, as well as, in the fields of clinical medicine, hazard prevention, etc. For this, a large number of robots have been developed, and researchers continue to design robots with greater capabilities to perform more challenging and comprehensive tasks (Hirose et al., 1986; Ooka et al., 1986; Cruse et al., 1994; Chen et al., 2002a; Habib, 2003a). There are many ways for a robot to move across a solid surface in which wheels, crawlers, and legs were common options for the available robots. The application fields of such robots are naturally restricted, depending on the condition of the ground. Wheeled mobile robots are mechanically simple, easy to construct, easy to implement a controller, dynamically stable in general, and they are ideal for operation on level and hard surfaces. When the surface is rough and has projections and depressions with dimensions that are greater than the diameter of the wheel or when the surface is soft, resistance to the movement increases drastically and their function as transport machines is almost lost, which leads to poor performance. The crawler type locomotion mechanisms have traverse ability higher than that of the wheel, but its control is hard and the dead-reckoning is difficult to realize, though it is possible to move on different terrains. In order to have good mobility over uneven and rough terrain a legged robot seems to be a good solution because legged locomotion is mechanically superior to wheeled or tracked locomotion over a variety of soil conditions and certainly superior for crossing obstacles. The path of the legged machine can be (partially) decoupled from the sequence of footholds, allowing a higher degree of mobility. This can be especially useful in narrow surroundings or terrain with discrete footholds (Raibert, 1986; Hirose, 2001). However, creating and controlling a legged machine that is powerful enough, but still light enough is very difficult. Legged robots are usually slower and have a lower load/power ratio with respect to wheeled robot. Autonomous legged robots have distinct control issues that must be addressed. These problems are amplified when the robot is small with an onboard controller that is purposely simple to accommodate weight and expense restrictions. The kinematics and dynamics of legged robots are nonlinear, while robot parameters, such as center of mass position, amount of payload, etc. are not known exactly and might also O pe n A cc es s D at ab as e w w w .ite ch on lin e. co m