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10

Controllers for automation

Chapter outline
10.1 Servo control ............................................................................................................................. 242
10.1.1 Digital controllers.......................................................................................................... 248
10.1.2 Advanced control systems............................................................................................ 251
10.2 Simulation of drives and controllers ...................................................................................... 252
10.3 Motion controllers .................................................................................................................... 258
10.3.1 Axis controllers .............................................................................................................. 258
10.3.2 Machine tool controllers .............................................................................................. 259
10.4 Programmable logic controllers .............................................................................................. 260
10.4.1 Combinational logic programming............................................................................. 264
10.4.2 Sequential logic programming .................................................................................... 267
10.5 Summary.................................................................................................................................... 270
References........................................................................................................................................... 270

Previous chapters have discussed the operation and characteristics of a wide range of
machine tools, robotics and related applications. While Chapter 1, Electromechanical
Systems, considered the overall systems, Chapter 2, Analysing a Drive System, reviewed
the criteria to be placed on the selection procedure, which was discussed in Chapter 3,
Power Transmission and Sizing. In all the applications considered, the control of the
required velocity or position is undertaken as a closed loop, which needs to be
considered as part of the design process. The chapter will firstly provide a brief overview
of closed loop control from a theoretical viewpoint. This is followed by considering how
a controller is integrated into an application, in particular, machine tools and robotic
applications, where controllers can be considered to fall into one of the following broad
categories:
Motion controllers are able to control the speed and position of one or a number of
axes, either individually or when undertaking a coordinated move (i.e. contouring). In
addition to closing the servo loop, modern motion controllers may also provide
limited data-management facilities, input and outputs channels, communication, and
safety circuits required by the machine tool or robot to execute the design function.
Multiaxis computer-numerical-control for machine-tool or robot will contain
several motion controllers for the axes, together with systems which will generate
the required motion profile, and the user and system interfaces. In the machine

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