DESIGN AND IMPLEMENTATION OF AN OBSTACLE DETECTOR ROBOTIC VEHICLE. A RESEARCH PROJECT MATERIAL ON COMPUTER SCIENCE EDUCATION
1.1 BACKGROUND OF STUDY
Over the years the curiosity of man and his intellectual prowess has led him to the discovery and invention of tools and machines that some only envisioned as impossible. In an attempt to make life easier and more comfortable he has delved into endless studies and researches to validate his unthinkable ideas, and one of the results of his intellectual power is the creation of autonomous self-controlling machines and devices. Robotics is a science of modern technology in which machine systems are programmed for general use. Obstacle detection and avoidance been an aspect of robotics, it involves the task of carrying out some preprogrammed objective which is subject to non-collision position constraints. The growing need of unmanned aerial and ground vehicles especially for military surveillance and city wars, has made the concept of obstacle avoidance a much desired one.
The obstacle detector robotic vehicle is designed to navigate without any sort of external influence through an unknown environment by avoiding collisions. However, it is worthy of note that the concept of obstacle avoidance differs considerably from path planning, this is considered so because the former is usually implemented using the reactive control law while the latter involves the pre-computation of an obstacle-free path in which the robot is programmed to navigate through. The need for such a system cuts across almost every sector of society. In 1988 a mobile nursing robot system was proposed, it was designed as an aid to bedridden patients who acquire constant assistance for the most elementary need. Such a devise was hoped to return a measure of independence to bedridden patients and also reduce the number of people who need hospitalization and constant attendance. (Borenstein and Koren, 1988).
The concept of obstacle detection and avoidance works essentially with the aid of robotic sensors. These sensors provide the means for the robot to detect information about its self and its environment. A single sensor integrated into an obstacle detector robotic vehicle is sufficient to navigate the system through its environment, although increasing the number and variety of sensors can greatly increase the ability of the robot to accumulate a more thorough information and understanding of the world around it. Most autonomous robotic systems will have multiple sensors (Brooks, 1986).
There are wide variety of sensors available which are capable of measuring almost anything, from environmental conditions (distance, light, sound, temperature) to angular and linear acceleration, forces and distances. The first sensor often incorporated into a mobile robot is a distance sensor, which is usually in the form of an infrared or Ultrasonic sensor. In both cases a pulse (light or sound) is sent and its reflection is timed to get a sense of distance. Usually these values are sent to the controller many times each second.
The use of ultrasonic sensors in most applications is easier, cheaper, and computationally simpler. Ultrasonic transducers are preferable to obtain three dimensional information on the environment (Borenstein and Koren, 1988).
They measure and detect distances to moving objects, are impervious to moving to target materials, surface and color, solid state units have virtually unlimited maintenance free life span. Ultrasonic sensors are not affected by dust, dirt or high-moisture environment.