ADLINK PCI-8144 - Manual (Page 41)

Operation Theory 31
4.1.4 Software real-time motion control kernel
For motion control kernel, there are three ways to accomplish it:
DSP, ASIC, and software real-time.
A motion control system needs an absolutely real-time control
cycle and the calculation on controller must provide a control data
at the same cycle. If not, the motor will not run smoothly. Many
machine makers will use PC’s computing power to do this. A feed-
back counter card can simply be used and a voltage output or
pulse output card to make it. This method is very low-end and
takes much software effort. For sure their realtime performance,
they will use a real-time software on the system. It increases the
complexity of the system too. But 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 motion control kernel
A DSP-based motion controller kernel solves real-time software
problem on computer. DSP is a micro-processer itself and all
motion control calculations can be done on it. There is no real-time
software problem because DSP has its own OS to arrange all the
procedures. There is no interruption from other inputs or context
switching problem like Windows based computer. Although it has
such a perfect performance on real-time requirements, its calcula-
tion speed is not as fast as PC’s CPU at this age. The software
interfacing between DSP controller’s vendors and users is not
easy to use. Some controller vendors provide some kind of
assembly languages for users to learn and some controller ven-
dors provide only a handshake documents for users to use. Both
ways are not easy to use. DSP based controller provide a better
way than software kernel for machine makers to build they appli-
cations.
4.1.6 ASIC motion control kernel
An ASIC motion control kernel is falls between software kernel
and DSP kernel in terms of difficulty. It has no real-time problem
because all motion functions are done via the ASIC. Users or con-
troller’s vendors just need to set some parameters which the ASIC
requires and the motion control will be done easily. This kind of