Considering  also  the  stiffness  and  accuracy   (in a practical sense considering what is reasonable to build), the picture is more complex。 Each of the first three types in Table 54。1 we refer to as serial kinematic

Table 54。1 Main categories of mechanical structures of industrial robots: Gantry is what a Cartesian coordinate robot is typically called with three prismatic joints, whose axes are coincident with a Cartesian coordinate system。 The SCARA or selective compliance assembly robot arm has two parallel rotary joints to provide compliance in a selected plane。 The articulated robot has three or more, typically six, rotary joints placed in series with their interconnecting links。 The parallel link robot is characterized by links that form closed loop structures shown with prismatic joints, but can also have revolute joints such as the Delta robot (Fig。 54。5) (pictures courtesy of Güdel, ADEPT, ABB, PI Physik Instrumente)

machines (SKMs), while the last is a parallel kinematic machine (PKM)。 To obtain maximum stiffness, again for a certain minimum level of cost, the end-effector is better supported from different directions, and here the PKM has significant advantages。 On the other hand, if high stiffness (but not low weight and high   dexterity)

is the main concern, a typical computerized numerical control (CNC) machine (e。g。, for milling) is  identical in principle to the gantry mechanism。 There are also modular systems with servo-controlled actuators that can be used to build both robots with purpose-designed mechanisms。

54。4 Typical Industrial Robot Applications

Out of the many possible uses of industrial robots se- lected case studies on high-potential robot applications will be briefly described。 Typical associated enabling technologies will be depicted。

54。4。1 Handling

Handling in robotics comprises numerous processes such as grasping, transporting, packaging, palletizing, and picking。 As seen in Fig。 54。8 handling is the largest

robot application field which is found in all  branches of manufacturing and logistics。 A central feature and major challenge in the engineering of robotic handling systems is the design of the gripper and associated grasping strategies given the physical  properties  of the workpiece, throughputs, and uncertainties regarding object geometry and location。 Current high-potential application of robot handling systems are: tending of CNC machines for workerless shifts [54。29], palletiz- ing,  and  lifting  of  objects  for  ergonomic  reasons or

Fig。54。9a–d Units of sausage are cut from strings, then placed into the thermo-formed cavities before applying lidding。 The coordination of the robots and the optimization of the picking frequency require a selection of the best path for each robot。 Missed sausages are fed back on the conveyor for another try。 The shown 4-DOF parallel robot reaches cycle times of 1—3 Hz and can move payloads of up to 8 kg (courtesy of robomotion, Germany)

Fig。54。10a–d Lightweight customized vacuum gripper (0:75 kg mass) through additive manufacturing。 Cookies are delivered continuously on a belt, grasped from the belt, and batches of eight are put on a blister matrix before final packaging。 The gripper’s spacing is pneumatically actuated and its rotation through the parallel robot’s central rotational axis (courtesy of robomotion, Germany)

when limitations specified in load handling regulations are exceeded [54。30], for reasons of cleanliness as is typical in the food, pharmaceutical, and semiconduc- tor industries [54。31–33], avoiding monotonous work and psychological strain, and ensure logistics quality through workpiece or object tracking [54。34]。 In the following, two use-cases of material handling will be highlighted, each in a different industrial domain, and based on specific industrial robot type and enabling technologies。