Embedded Systems September 2000 Vol13_10

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SPECTRA e FIGURE 1 ifhree phase stator and power bridge - Of course, we may write this matrix in an algebraic form as well : isd = ia *cos( Be)+ i fJ *sin(&. ) And the reverse transform may be expressed: ia = isd *cos(&)- isq *sin(&) ip = isd *sin( B)+ iq *cos( B) [ I fJ / 01 ]-[cos(B) sin(e)I/ "] - sm( e) cos( e) I" A short aside Now, we can combine both trans- forms into one matrix. This fact is a great deal easier to see and under- stand when we view the transforms as matrices: ' ------- ' . When putting together an Embedded System, remember ... A system is more than the sum of its parts. ADS GRAPHICS CLIENT™ PLUS Application Ready Systems at your fingertips! A StrongARM 206 MHz M Embedded linux WinCE 3.0 JavaNxWorks/OS-9 ADS engineers complete embedded system solutions so that you can focus on what's most important: Your Application [ ] [ l d =l. cos(ll) ' • cos(ll-y) cos(ll-2y) / 3 -sin(ll) -sin(ll-y) -sin(ll-2y) 1: r/ ] Even though this look efficient, take care. Depending upon the architec- ture of your processor, it can end up being more work because of the extra sinusoidal computations of position. Using the algorithms Before we can begin to use this form of control, we need to initialize the sys- tem. Since we base our control of the current in the phase windings on the position of the rotor-to keep the torque angle 90 degrees in advance of the stator flux-we must find out pre- cisely where the rotor is to start. We can do this by applying a known and constant voltage vector to the sta- tor . We do this in such a way as to cause the rotor to align with one of the poles. We use this positioning to estab- lish our first position with the encoder and to reset the electrical position. In Table l , you will see the eight states 184 SEPTEMBER 2000 Embedded Systems Programming

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