Robots generally have a single arm that has from two to six axes of motion. With a typical six-axis robot, the arm is positioned in three axes and the robot wrist is positioned in the other three. Robot arms move in one of four positioning systems: rectangular, cylindrical, spherical, or jointed arm, or a modification of these three configurations. Typical functions include material handling, machining, painting, welding, and assembly.
Robots are powered by any of three actuation systems: Hydraulic, pneumatic, or electrical. In some cases two methods are combined.
Hydraulic actuation is preferred for heavy loads. It is mechanically simple and fast. Accuracy is generally less than an electric system and greater than pneumatic actuation. Pneumatic power is generally used for low-cost, less accurate pick-and-place applications.
Electrical actuation is preferred where speed and accuracy are prime considerations.
Robot hands, or end effectors, may be general purpose or designed to do a specific task. General-purpose end effectors are usually needed for material-handling tasks where it is not known where the robot will grip a product or which of several products will be moved.
Robots use some type of sensing system if the product handled involves many unknowns, or if it is not practical to have extremely precise arm positioning. For example, it may be more cost-effective to have a hand find a part through touch sensing than to pay for precise positioning jigs and arm motion.