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IMPROVED SENSORLESS CONTROL WITH THE ST62 MCU FOR UNIVERSAL MOTOR

ANNEX 3

MONITORING ON A PC COMPUTER SCREEN

In order to monitor various variables during the motor characterization, an RS232

connection is provided in the micro-controller software between the ST6 and a per-

sonal computer. In the program “regul.asm”, two data bytes are sent to the PC every

mains cycle: on negative half-cycles, the measured current it0 is sent, and on positive

half-cycles, the calculated firing delay td is sent. The instructions used to send this

data are the following:

for the it0 byte:

ld

a,it0

call rs232

and for the td byte:

ld

a,td

call rs232

When it is called, the rs232 subroutine sends at 19200 bauds on port pin PA3 the

data byte contained in the accumulator. This takes approximately 0.5 mS. Replacing

it0 or td by another register or RAM variable allows to send any intermediate calcula-

tion result or variable (coefficient from look-up table, proportional term, integral term,

current error...). To connect the PA3 and VDD micro-controller pins to the PC require

a level amplification (to boost the signal level from 0-5 volts to -5 / +5 volts) performed

by a Maxim MAX232 circuit, and galvanic isolation, performed by an optocoupler (see

Figure 13). The 9-pin connector must be connected to the COM1 serial port of the

PC.

On the PC side, two executable programs are provided: NUMBER.EXE and

VISU.EXE.

NUMBER.EXE, executed on the PC while the motor is running, displays on the

screen two rows of data in decimal format representing the evolution in time of the re-

ceived data it0 and td. The two rows scroll down the screen, and at the same time are

stored in a text file named NUMBER.PRN. Hitting any key stops the program execu-

tion. The data file NUMBER.PRN remains, available for latter use. It can be imported

into a spreadsheet program for example, to visualize the curves representing in time

domain the evolution of it0 and td.

Program VISU.EXE, on the other hand, allow to display graphically in real time the

time domain evolution of it0 and td. The attached file EGAVGA.BGI must be present

in the same directory, and the PC must have a VGA (or better) screen, as the graphic

is displayed in 640x480 pixels resolution. Hitting any key (except “e”) stops tempo-

rarily the curves drawing, so the user can pause to examine a detail of the display.