nificant role in the implementation of lean manu- facturing strategies。 However, efforts are underway to introduce industrial robots to lean, agile man- ufacturing。 Characteristics are robot solutions that can be flexibly added  to  manufacturing systems on demand, that are  significantly  less expensive on a life-cycle-costing (LCC) basis than today’s systems due to reduced peripherals and systems integration (system out of the box) [54。23]。 With robots becoming commodities in manufacturing they might be used as intuitively and naturally   as a handheld power tool today。 This would imply intuitive and  safe  human–robot collaboration  and

versatility due to advanced sensing, control, and embedding the robot set-up and operation in an IT infrastructure。

● Factories of the future will represent a network   of

self-organizing cyber physical systems (CPS)。 As part of this industrial internet CPSs embed compu- tation, networking, and physical processes and can either represent manufacturing equipment such as machine tools, fixtures, trays, conveyors, tools, etc。 or the workpiece which controls and memorizes its production。 Robots are considered the centerpiece of future smart factories which combine manufac- turing agility, profitability, human ergonomics, and minimized resource consumption [54。24]。

● Robots  in  assembly  have  not  reached  their pre-

dicted installation potential mainly due to cheap labor cost and the lean assembly work systems which support highest flexibility and productivity at minimal waste。 A reason is partly seen in the slow advances in dexterous manipulation for assembly tasks with industrial robustness。 Here, torque-con- trolled lightweight robots [54。25] and two-armed robot systems have been proposed to imitate human ergonomics and task execution [54。26]。

● New financing models such as leasing, pay by  ser-

vice will allow end-users to use robots on demand or to have manufacturing service providers to op- erate manufacturing lines on a pay-on-production basis [54。27]。

Figure 54。8 depicts some key figures on the recent extent of industrial robot diffusion into manufacturing。

54。3 Industrial Robot Kinematics

By definition, an industrial robot is an automatically controlled, reprogrammable, multipurpose manipula- tor, programmable in three or more axes, which can be either fixed in place or mobile for use in indus- trial automation applications [54。28]。 Robots can be categorized according to their number of independent kinematic axes, and their mechanical structure which affect most of the robots’ kinematic properties, the com- putation methods used to determine joint motions, and the form and size of the robot workspace。 Robot me- chanical structures are composed of links that are rigid bodies connecting neighboring (prismatic, rotary, cylin- drical or spherical) joints。 The diagrams in Table 54。1 show several common types of robot mechanical struc- tures。 Of course, the workspace of industrial robots can be significantly expanded by placing the robot arm on an additional linear axis, sometimes reaching a length of more than 50 m, or even on mobile platforms。   Fur-

thermore, robot mechanical structures can be composed by joint modules which are connected by links to form task-specific designs。

With advances in the state of the art in motion control and computer hardware processing capabilities, computation is much less a constraint on mechanism choice than it was for early robot designers。 The choice of mechanical structure of the robot depends mostly on fundamental mechanical requirements such as payload and workspace size。 Considering a given level of cost, there is usually a trade-off between workspace size and stiffness。 To enable the robot to reach inside or around obstacles it is clearly advantageous to use an articulated mechanical design。