A
A
C
C
S
S
8
8
0
0
6
6
D
D
i
i
g
g
i
i
t
t
a
a
l
l
A
A
C
C
S
S
e
e
r
r
v
v
o
o
d
d
r
r
i
i
v
v
e
e
M
M
a
a
n
n
u
u
a
a
l
l
R
R
e
e
v
v
1
1
.
.
0
0
Tel: (86)755-26434369
30
Website: www.leadshine.com
Figure 29: Step response with better Kp and Ki of
current-loop(Kp=25000,Ki=850)
5.
At that moment Kp and Ki of the current loop is nearly optimum. To reduce the
raise time please increase Kp, and increase Ki to reduce the steady-state error. You
can use the mouse to drag a rectangle to zoom in the curse for more detail. Click any
place of the window to zoom out. See figure 30.
Figure 30: Drag a rectangle to zoom in
A
A
C
C
S
S
8
8
0
0
6
6
D
D
i
i
g
g
i
i
t
t
a
a
l
l
A
A
C
C
S
S
e
e
r
r
v
v
o
o
d
d
r
r
i
i
v
v
e
e
M
M
a
a
n
n
u
u
a
a
l
l
R
R
e
e
v
v
1
1
.
.
0
0
Tel: (86)755-26434369
31
Website: www.leadshine.com
Position Loop Tuning
Position Loop Introduction
Position loop tuning is dependant on the mechanical load, and therefore will change
with any mechanical system changes. Position loop tuning should be performed with
the motor installed in the system. The position loop can be closed around velocity or
torque mode (depending on whether the velocity loop is enabled or disabled). If it is
closed around velocity mode, the position loop algorithm output becomes the new
velocity set point. If it is closed around torque mode, the position loop algorithm
output becomes the new torque set point. There are some important differences in the
tuning process and application of these two approaches.
Position around Velocity:
This mode is most common in "contouring" application,
where a position trajectory must be tracked very closely. The velocity loop provides
additional "stiffness", and keeps the dynamic position errors minimal, since the
system now reacts to not just position errors, but also velocity errors (which can be
interpreted as position error changes). It is important to start with a stable yet
responsive velocity loop. Typically, it is sufficient to just use the position loop
proportional gain. Feedforward gain can be added to improve tracking performance
(i.e. minimize the difference between commanded and actual position). The velocity
loop is disabled in current version ACS806, and it adopts
Position around Current
(Torque) mode.
Position around Torque:
This mode is most common in point-to-point applications,
where actual motion between start and end point is not very critical. In this case,
velocity loop tuning can be avoided. This can be advantageous if the velocity
feedback is poor (e.g. low resolution encoder, poor encoder quadrature.).
In this case,
the tuning process requires that the position loop proportional and derivative
gain are increased simultaneously, unless the system has sufficient friction, in
which case no derivative gain is necessary. Once a stable response is achieved,
integral gain can be added to improve stiffness.
It is best to use a step command