Types of Industrial Robots

Four basic types of robot configurations are in use today. Some robots are hybrids of one or more configurations. The configurations are called cylindrical, rectilinear, spherical, and jointed spherical, which is also called articulated arm. These robots are so named because their work envelope looks like the shape that describes them. For instance, the work envelope of the cylindrical robot looks like a cylinder, and the work envelope of the rectilinear robot looks like a rectangle.

These robots can be powered by electric motors, electric actuators, hydraulic motors, hydraulic cylinders, or pneumatic cylinders. In some cases the electric motors rotate ball-screw mechanisms or rack and pinion systems to provide linear motion from the rotary motion of the motor. Sometimes linear stepper motors are also used to provide linear motion. In other applications motors are used with gears, belts, chains, and pulleys to provide a variety of linear and rotational motion.

Each axis a robot has is called a degree of freedom. For instance, if a robot has three axes, it's said to have three degrees of freedom. The degrees of freedom include the axis that's provided by the wrist as well as the three axes provided by the main robot body. In other words, a robot with three body axes (base, waist, and upper arm) and three wrist axes (pitch, roll, and yaw) will have six degrees of freedom.

Something one may notice about robots is that they have continually evolved since they were first introduced on a large scale in industry, and they continually evolve with changes that occur with technology. For instance, the first electric robots were rather small and usually powered with DC motors since it was easier to control the speed and power of a DC motor. In the 1980s larger transistors that could handle over 1000 A and 500 volts were introduced, and AC variable-frequency amplifiers were designed. This allowed very large AC motors to be used on robots to replace the DC and hydraulic drives. You will see many of the changes that have taken place in the robot industry in the remainder of this section.