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of DC-driven, and the AC motor with a small size, light
weight, full-enclosed work and so on. Here we focus on
talking about AC spindle drive unit with the spindle axis
associated with the feed control.
1) AC spindle drive unit
This feed AC servo motor using permanent magnet
synchronous motor, but the spindle cage AC motor uses
AC motors, it is because the CNC machine tool numerical
control machine tool spindle drive system without the
feed drive system, as did need such a high dynamic
performance and transfer speed range. We use the vector
control algorithm, the basic idea is through a complex
coordinate transformation to an equivalent AC motor into
a DC motor and controlled. Using this algorithm, AC
motors and DC motors very similar to the mathematical
model, which can be equally good speed performance[4,9].
AC spindle drive unit from the grid-side inverter,
control regulator, the load-side inverter, microprocessor
controller, such as the composition of components.Shown
as Figure 5.
Figure5. AC SPINDLE DRIVE UNIT STRUCTURE
Spindle motor operating characteristics as shown in
Figure 6.
Figure6. SPINDLE MOTOR OPERATING CHARACTERISTIC CURVE
Figure 6, M is torque, P is power, n to the base speed.
The following belong in the base speed n0 constant speed
governor, by changing the armature voltage methods. Its
speed formula is:
U − I
a
R
n =
(1)
CeΦ
Φ = KI
f
(2)
Which, n 0 following excitation current I f the same,
changing the armature voltage U speed, the output
depends on the maximum torque Mmax maximum
armature current Imax, the maximum current time due to
a constant, and therefore the maximum torque output is
constant , but the output power will increase as the speed
increases, so n 0 hereinafter referred to as constant torque
speed.
N 0 above the base speed up adoption of a weak
magnetic method of speed governor, that is, by adjusting
the I f the method, the output of the maximum torque
Mmax as follows:
M
max
CM ΦI max
= (3)
Speed in the weak magnetic l, I f-fold reduction of K,
rotational speed will be a corresponding increase in K
times the output of the maximum torque motor is because
the magnetic flux Reduction in K times the maximum
power output remains unchanged, thereby achieving the
constant power speed.
2) Spindle axis associated with the feed control
a) SPC
In the spindle and feed axis control to be associated
with the use of the pulse encoder, commonly used can be
divided into incremental and absolute type, contact and
contactless card types. We use incremental pulse encoder
because the encoder with high precision, simple structure,
reliable.
Incremental pulse encoder is generally 90 degrees out
of phase two of the A, B signal and a zero-bit C signal, in
which A, B signal can either be used to calculate the size
of angular displacement at the same time use them to lead
or lag phase They can also identify the relative direction
of rotation, then the B signal ahead of A signals that fat
transfer; C signal for each transponder can serve as a zero
signal, the signal for the A or B signals, several technical
benchmarks[4].
In addition, incremental pulse can also be used for the
preparation of spindle speed measurement, but the
measured maximum speed n max single pulse width
limited by its corresponding formula is as follows:
60
n
max
= (4)
NT
0
Where, n max is the maximum measured pulse encoder
speed (r / min); N for pulse encoder pulses per revolution
generated by the number of (r); T0 for a single pulse
width (s).
b) spindle rotation and axial feed of the
Association Control
We have installed on the spindle to detect the spindle
encoder pulses corner, phase, zero-signal, the spindle
rotation process, linked with the pulse encoder
continuously send pulses sent to CNC devices, according
to the results of interpolation calculations, the control into
the to the axis servo system that allows feed rate and
spindle speed to maintain the ratio between required.
c) spindle rotation and radial feed of the
Association Control
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