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AD2S100

AC Vector Processor

Analog Devices 

AD2S100

√In Figure 9, “–1” operator performs a 180° phase shift opera-

tion. It can be illustrated by a 2-phase-to-3-phase reverse trans-

formation. An example is shown in Figure 10.

Cosθ

R

R

Sinθ

R

2

PH/IP1 (Cosθ)

PH/OP1

Cos(θ + φ)

AD2S100

PH/OP3

Cos(θ + 240° + φ)

PH/IP4 (Sinθ)

PH/OP2

Cos(θ + 120° + φ)

Cos(θ – φ)

Cos(θ + 120° – φ)

Cos(θ + 240° – φ)

φ

Figure 10. Two-Phase to Three-Phase Reverse

Transformation

Field Oriented Control of AC Induction Machine in a Rotor

Flux Frame

The architecture shown in Figure 11 identifies a simplified

scheme where the AD2S100 permits the DSP computing core

to execute the motor control in what is normally termed the

rotor reference frame. This reference frame actually operates in

synchronism with the rotor of a motor. This has significant

benefits regarding motor control efficiency and economics. The

calculating power required in the rotor reference frame is signifi-

cantly reduced because the currents and flux are rotating at the

slip frequency. This permits calculations to be carried out in

time frames of, 100 µs, or under by a fixed-point DSP. Bench-

mark timing in this type of architecture can attain floating-point

speed processing with a fixed-point processor. Perhaps the larg-

est advantage is in the ease with which the rotor flux position

can be obtained. A large amount of computation time is, there-

fore, removed by the AD2S100 vector processors due to the

split architecture shown in Figure 11. Motor control systems

employing one DSP to carry out the cartesian to polar transfor-

mations required for vector control are, therefore, tasked with

additional duties due to the fact that they normally operate in

the flux reference frame.

The robustness of the control system can also be increased by

carrying out the control in the rotor reference frame. This is

achieved through the ability to increase and improve both the

algorithm quality in nonlinear calculations attributed to magne-

tizing inductance and rotor time constant for example. An

increase in sampling time can also be concluded with this archi-

tecture by avoiding the additional computing associated with

number truncation and rounding errors which reduce the signal-

to-noise rejection ratio.

POSITION

FEEDBACK

VELOCITY

FEEDBACK

v

v

v

POSITION

SET POINT

CONTROL SOFTWARE ADSP2101

v imrmax

is1

VECTOR

CO-PROCESSOR

(a + jb)e–jρ

SPEED

CONTROL

+ ε'

–

ε

LIMIT

+ ω'

TORQUE

CONTROL

LIMIT

md'

–

ω

FIELD

WEAKENING

+ imr'

–

imr

Cm

+ iqs'

–

iqs

+ ids'

–

ids

is2

REVERSE

ROTATION

is3

iqs

ω+

+ ω2

Tr

iqs

ω1

θ2

+

+ε

Vqs'

VECTOR

Vs1

CO-PROCESSOR

Vds' (a + jb)e'–jρ'

ρ'

Vs2

FORWARD

ROTATION

Vs3

AD2S100

ids

ρ

AD2S100

Figure 11. Rotor Reference Frame Architecture

REV. A

–9–

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