Book Analog Interfacing to Embedded Microprocessors
application usually has two loops operating together in parallel. The PID
loop controls motor current to achieve the correct velocity. The input to
the PID loop is the velocity setpoint. A second loop creates the trape-
zoidal waveform by passing velocity setpoint values to the velocity control
PID loop.
Figure 5.20 shows a simple diagram of such a control system. This is typical
of the position-control functionality in a motor control IC such as the
LM628/9. In this figure, the velocity generator block is separate from the
microprocessor, as it would be in a self-contained motion control IC. If you
were writing software for a microprocessor or DSP to directly control a motor,
the velocity generator and PID loops would be software functions.
The position control loop generates position commands to the PID loop.
This is the same position command that was an input to the PID loop in Figure
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