Robots are physical agents that perform tasks by manipulating the physical world. To do so, they are equipped with effectors such as legs, wheels, joints, and grippers. Effectors have a single purpose: to assert physical forces on the environment. Robots are also equipped with sensors, which allow them to perceive their environment. Present-day robotics employs a diverse set of sensors, including cameras and lasers to measure the environment, and gyroscopes and accelerometers to measure the robot’s own motion.
Most of today’s robots fall into one of three primary categories. Manipulators, or robot arms, are physically anchored to their workplace, for example in a factory assembly line or on the International Space Station. Manipulator motion usually involves a chain of controllable joints, enabling such robots to place their effectors in any position within the workplace. Manipulators are by far the most common type of industrial robots. with approximately one million units installed worldwide. Some mobile manipulators are used in hospitals to assist surgeons. Few car manufacturers could survive without robotic manipulators, and some manipulators have even been used to generate original artwork.
The second category is the mobile robot. Mobile robots move about their environment using wheels, legs, or similar mechanisms. They have been put to use delivering food in hospitals, moving containers at loading docks, and similar tasks. Unmanned ground vehicles, or UGVs, drive autonomously on streets, highways, and off-road. The planetary rover explored Mars for a period of 3 months in 1997. Subsequent NASA robots include the twin Mars Exploration Rovers (one is depicted on the cover of this book), which landed in 2003 and were still operating six years later. Other types of mobile robots include unmanned air vehicles (UAVs), commonly used for surveillance, crop-spraying, and military operations.
Autonomous underwater vehicles (AUVs) are used in deep-sea exploration. Mobile robots deliver packages in the workplace and vacuum the floors at home.
The third type of robot combines mobility with manipulation and is often called a mobile manipulator. Humanoid robots mimic the human torso. Mobile manipulators can apply their effectors further afield than anchored manipulators can, but their task is made harder because they don’t have the rigidity that the anchor provides.
The field of robotics also includes prosthetic devices (artificial limbs, ears, and eyes for humans), intelligent environments (such as an entire house that is equipped with sensors and effectors), and multibody systems, wherein robotic action is achieved through swarms of small cooperating robots.
Real robots must cope with environments that are partially observable, stochastic, dynamic, and continuous. Many robot environments are sequential and multiagent as well. Partial observability and stochasticity are the results of dealing with a large, complex world Robot cameras cannot see around comers, and motion commands are subject to uncertainty due to gears slipping, friction, etc. Also, the real world stubbornly refuses to operate faster than in real-time. In a simulated environment, it is possible to use simple algorithms to learn in a few CPU hours from millions of trials. In a real environment, it might take years to run these trials. Furthermore, real crashes really hurt, unlike simulated ones. Practical robotic systems, need to embody prior knowledge about the robot, its physical environment, and the tasks that the robot will perform so that the robot can learn quickly and perform safely.
Robotics brings together many of the concepts we have seen earlier in the book, including probabilistic state estimation, and perception. planning, unsupervised learning, and reinforcement learning. For some of these concepts, robotics serves as a challenging example application. For other concepts, this chapter breaks new ground in introducing the continuous version of techniques that we previously saw only in the discrete case.
