43
CHAPTER 7 – Programming
SMT-BD1/t
The torque control structure associated to this sequence is presented below :
At the start of a torque control sequence, the motor is accelerating and then running at the
Speed set point
parameter value until the shaft is locked. The motor running direction depends on the sign of the
Speed set point
parameter. When the motor shaft displacement has been stopped in the running direction, the current is raising
up to the limit value defined by the
Internal torque set point
parameter or the value given by the ANin1 analog
input voltage if
Analog torque set point
is selected. When the current limit value has been reached, the TER
logic output is activated and the amplifier is holding the torque set point during the time value defined by the
parameter
Torque holding time
. The torque control sequence is then automatically over after the holding time
value. If the
Torque holding time
parameter value exceeds 16000 ms, then the torque holding time is infinite and
the sequence stop condition can be used to leave the torque control sequence.
During the torque holding time, if the motor speed value is exceeding the
Overspeed limit
parameter value
because of a material braking, a torque sequence error is generated. When a torque sequence error is generated,
the TER logic output is desactivated and the torque control sequence is immediately stopped. The sequence
which number is given by the
Sequence error link
parameter value is then automatically executed. This security
is useful for a winding application where it is necessary to set the
Speed set point
parameter value higher than
the line speed value in order to reach the current limitation during the winding operation.
The selection of both
Analog torque set point
and
Set point modulation by diameter sensor
allows a typical
winder or unwinder tension control application, as shown on the following diagram:
The SMT-BD1/t amplifier is driving the spool motor and provides a constant material tension control according to
the analog set point (
Analog torque set point
selected) and the diameter measurement signal (
Set point ratio
modulation by diameter sensor
selected). When the spool diameter is changing, the motor torque value is
modified according to the diameter measurement value in order to maintain the right material force with regard to
the tension set point. In an unwinding application, the
Speed set point
parameter is set at a low value in order to
have the material automatically rewound and progressively stretched up to the tension set point at the sequence
start. In a winding application, the
Speed set point
parameter must be set at a higher value than the maximum
value of the line speed during the winding operation in order to reach the current limitation.
ANin1
torque set point
Speed ref
ANin2
diameter
measurement
Accel/decel
ramp
Constant
ratio
Diameter
modulation
Speed
PI
motor speed
controller
Motor
+
-
Current
limit
Torque
ratio
Speed
set point
Torque
set point
Speed
ratio
IA, IB
Master encoder
channels
Encoder
modulation
Motor
Running material
Roller
Tension
set point
SMT-BD1/t
amplifier
Material
spool
Diameter
measurement
