Page 358 - Mechatronics with Experiments

JWST499-Cetinkunt
JWST499-c06
344 MECHATRONICS Printer: Yet to Come October 9, 2014 8:1 254mm×178mm
V ss
4.7μF 0.1μF
F BIAS SEL1 SEL2 V ss V ss
nc = No connect 3 21 20 19
nc 4 18 EXC
sin EXC
5 AD2S99 17
DGND AGND
6 top view 16
cos (not to scale)
7 15 nc
SEL2 = GND nc 8 14 nc
SEL1 = V ss
F out = 5kHz 910 11 12 13
Synref V DD
nc LOS V DD nc
50kΩ 4.7μF
0.1μF
0.1μF
100kΩ
18 17 16 15 14 0.1μF V DD
REF 4.7μF
19 cos LO 13
V DD
4.7μF 0.1μF
20 cos V SS 12 V ss
1 AGND DGND 11
S2 cos S4 2 sin AD2S90 10
R2 S3
3 sin LO top view 9
REF sin (not to scale)
4567 8
R4 Resolver S1
FIGURE 6.15: An example circuit for resolver signal processing. It can be used for a resolver
which has one rotor and two stator windings. AD2S99 chip provides the reference oscillator
signal, and an AD2S90 chip processes the resolver signals for conversion to digital data.

= . Functionally, the end result is that the output position value presented is proportional
to the rotor angle
V (t) = k ⋅ (t) (6.59)
out 1
This circuit can be implemented with integrated circuits AD2S99 programmable oscilla-
tor chip and AD2S90 resolver to digital converter (RTDC) chip by analog devices (Fig-
ure 6.15). The AD2S99 chip is a programmable sinusoidal oscillator. The input supply
voltage is ±5 VDC. It provides the sinusoidal excitation voltage for the primary winding.
The excitation frequency is programmable to be one 2 kHz, 5 kHz, 10 kHz, or 20 kHz. It
accepts the induced voltage signals from the secondary winding pair at the sin and cos pins.
In addition, it provides a synchronous square wave reference output signal that is phase
locked with the sin and cos signal. This signal is used by the AD2S90 chip for converting
the resolver signal to a digital signal. AD2S90 is the main chip that performs the conversion
of the resolver analog signals to digital form. It provides the resulting digital position signal
in two different format: a 12-bit serial digital code and an incremental encoder equivalent
A and B channel signal. In motor control applications, many amplifiers accept the resolver
signal and use it for current commutation. In addition, they output an encoder equivalent
(encoder emulation) signal which can be used by a closed loop position controller. It emu-
lates a 1024-line per revolution incremental encoder A and B channels. When the A and
B channel signals are decoded with ×4, it results in 4096 counts∕rev resolution which is
equivalent to a 12-bit resolution.