Page 261 - Electric Drives and Electromechanical Systems

258 Electric Drives and Electromechanical Systems

Thesetwo simulations show theflexibility of MATLAB. In practice a wide range of
motors (both brushed and brushless), gearboxes (harmonic, cycloid, differential and
planetary), leadscrews and belt drives can simulate with easy. In addition, a wide range
of continuous and digital controllers can be incorporated all of which are fully
described in the associated documentation (Mathworks, 2019). Not only can the
complete system be simulated, but the using MATLAB’s control toolbox it is possible to
determine the controller parameters required to a specific response (Mathworks, 2019;
Dukkipati, 2006).

10.3 Motion controllers

In many instances several motor-drives are simultaneously controlled by a single
supervisory controller, as discussed in the CNC machine-tool and robotic applications
reviewed in Chapter 1. The supervisory controller undertakes a wide range of high-level
tasks, such as the generation of position, velocity, and acceleration profiles, together
with a range of housekeeping functions, including data management, communications,
and operation of the user interface. The choice of controller strategy depends on the
number of axes and on the degree of coordination between the axes; possible options
include the following.

10.3.1 Axis controllers

A multi-axis controller can control a number of motion axes simultaneously, to allow
multi-axis moves found in robotics and machine tool contouring. The implementation
can be undertaken with the use of several single-chip microcontrollers on a single
printed-circuit board. A microcontroller is a microprocessor with additional memory
(both random-access memory (RAM) and programmable read-only memory (PROM)),
together with analogue-to-digital (A/D) converters, digital-to-analogue (D/A)
converters, and communications ports fabricated into one package. Several companies
supply customised devices that incorporate motion-control algorithms; all that the
users must supply are the equation parameters and the limiting values. With the
increasing power and ease of programming of industry-standard personal computers, a
range of motion-control cards using these devices have been developed. They have
configured standard expansion sockets which permit a system to be put together with
the minimum of effort. Motion control cards are available in a range of sizes, the largest
can control up to eight axes. By placing more than one axis on a card, multiaxis
interpolation and contouring or coordinated motion between axes can be easily
undertaken. The boards are normally available in several bus configurations giving the
system designer considerable flexibility, including plugging directly into a personal
computer backplane. A typical three-axis card can operate in either independent or
vector-positioning modes and have the ability to contour up to speeds of 500 000
encoder counts per second.