Issue link: https://wardsworld.wardsci.com/i/1504662
3 Robotics (continued) + ward ' s science of motion to the joints through mechanical linkages such as shafts, belts, cables, or gears. This approach overcomes many of the problems associated with locating actuators at the joints, but requires the design of backlash-free mechanical linkages that can transmit power effectively through the arm in all of its positions and orientations. An innovation in the design of as- sembly robots is the use of direct-drive motors, which eliminate the need for gear transmissions. This type of robot has become popular for high-speed assembly tasks. End effectors A two-jaw parallel gripper actuated by a pneumatic cylinder is a common type of end effector for industrial robots. End effectors are specialized for particular applications, such as parts handling, welding, and drilling. Using a quick-disconnect mechanism, robots can change their own end effectors to suit the task from a selection of special-purpose attachments. Since position errors of robots, fixtures, and grippers may occur during high-precision assembly tasks, compliance is needed to compensate for misalignment between parts during operations such as inserting a piston into an engine head or fitting a gland on a valve assembly. A spring-actuated mechanism, called a re- mote center compliance (RCC) wrist, may be attached between the robot arm and the end effector for this purpose. Robotic hands Dexterity is as basic to manufacturing assembly as it is to pros- thetic and human hands. Multifingered robot hands can ac- complish fine manipulation, achieve robotic hand cooperation for fixtureless assembly, operate in hazardous environments, explore remote locations, and perform other important func- tions. The usefulness of multifingered robot hands to perform fine manipulation and grasping tasks is widely acknowledged, but it is costly to implement. Mechanisms for robotic hands are commercially available with two to four fingers and a thumb, each with one to four degrees of freedom and actuated by servomotors. Mobile robots Mobile robots can have wheels, tracks, legs, or a combination of these parts. These robots also can crawl, for example, for inspecting pipes. Tracked mobile robots developed for military and surveillance applications are among the most stable and rugged. Automated guided vehicles (AGV) are wheeled mobile robots that deliver parts and tools in factories by following a guide path embedded in the floor. The payload capacity of these vehicles varies from 100 kg (220 lb) to several tons. An AGV for light-duty work such as mail delivery in office buildings can follow a stripe attached to the floor. An AGV can be pro- grammed like an industrial robot to follow a preprogrammed trajectory and to make decisions along the way depending on inputs from external signals. The path of an AGV can be guided by a wire underneath the floor or a stripe painted on the surface. Free-ranging AGVs are also available for industrial and commercial use to avoid the need for installing a fixed path. Walking machines Walking robots have been built with various arrangements and numbers of legs. The control of gait stability for legged loco- motion systems is a difficult implementation issue, particularly for two-legged (biped) machines. Research in locomotion has provided results on kinematic and dynamic modeling, control algorithms, and other forms of stability. Solutions to these research issues have resulted in a better understanding of high- level planning, control requirements, and their implementation. Robot control and planning A robot control system directs the motion and sensory process- ing of a robot or system of cooperating robots. The controller may consist of only a sequencing device for simple robots, although most multiaxis industrial robots employ servo-con- trolled positioning of their joints by a microprocessor-based system. Sensory systems The robot sensory system gathers specific information needed by the control system and, in more advanced systems, main- tains an internal model of the environment to enable predic- tion and decision making. The joint position transducers on industrial robots provide a minimal sensory system for many industrial applications, but other sensors are needed to gather data about the external environment. Sensors may detect posi- tion, velocity, acceleration, visual, proximity, acoustic, force- torque, tactile, thermal, and radiation data. Intelligent systems As information moves up from a device, the amount of infor- mation increases and the speed of data acquisition decreases. These control architectures form the basis for computer inte- grated manufacturing (CIM), a hierarchical approach to orga- nizing automated factories. Another common approach is the interconnection of intelligent system elements that can learn, reason, and modify their configuration to satisfy overall system requirements. The rise of artificial intelligence and machine learning has also vastly expanded the abilities of robots to han- dle increasingly complex tasks and perform work that would be difficult or impossible for humans to perform efficiently.