ADLINK Technology cPCI-8168, User Manual

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Operation Theory 41
4.1.4 Software real-time motion control kernel
There are three ways to accomplish motion control kernel: DSP-
based, ASIC based, and software real-time based.
A motion control system needs an absolute real-time control cycle
and the calculation on the controller must provide control data at
the same cycle. If not, the motor will not run smoothly. Many
machine makers will use a PC’s computing power to do this by
simply using a feedback counter card and a voltage output or
pulse output card. This method is cost effective but requires a
great deal of software effort. For realtime performance a real-time
software is necessary, increasing the complexity of the system.
However, this method is the most flexible way for a professional
motion control designers. Most of these methods are on NC
machines.
4.1.5 DSP based motion control kernel
A DSP-based motion control kernel solves real-time software
problems ona computer. DSP is a micro-processer that can be
used for all motion control calculations. DSP does not have the
problems real-time software does since DSP has its own OS to
arrange all procedures and there aren’t any interruptions from
other inputs or context switching problems like Windows based
computers. Although real-time provides optimal performance, the
calculation speed is not currently as fast as a PC’s CPU. The soft-
ware interfacing between the vendors of DSP based controllers
and its users is difficult to use. To simplify the software interface for
users some controller vendors provide an assembly language to
learn while other controller vendors provide only a handshake doc-
uments. Neither method is user friendly. However, a DSP based
controller is a more efficient way for machine makers to build their
applications than software kernel .
4.1.6 ASIC based motion control kernel
An ASIC-base motion control kernel does not have any real-time
problems since all motion functions are done via ASIC. Users or
controller vendors only need to set some required parameters and
the motion control will be done easily. This kind of motion control
separates all system integration problems into 4 parts: motor