User Manual

12/16 Bosch Rexroth AG
Open and Closed Loop Speed Control SPC RE 95300/12.07
Figure 9: How the SPCD closed loop speed control works
Setpoint specification
Two pushbuttons in the vehicle (left and right) are used to
select the output speed or flow.
They also set the direction of the drive (clockwise/counter-
clockwise) and therefore the direction in which the drum
rotates.
Working behavior
The working behavior of the drum when mixing and delivering
the concrete is controlled by two variables:
• The pushbuttons (right/left) set the setpoint for the output
speed and direction in which the drum rotates.
• The acceleration and deceleration behavior selected by the
time ramps determine how quickly the control changes at the
PWM output.
If the drum is at a downtime and one of the buttons (e.g. right)
is pressed, the drive starts to move in the appropriate direc-
tion (clockwise) and the drum rotates clockwise and mixes the
concrete.
Pressing the same button (right) again increases the output
speed in this direction according to the selected time ramp.
Pressing the other button (the left button in this example)
reduces the output speed in the selected direction of rotation
(clockwise in this example) according to the selected time
ramp.
The time ramps for increasing and reducing the output speed
for concrete mixing are set at the same time.
If the output speed is reduced so much that the mixing drum is
at a downtime and the button that was pressed to reduce the
speed (the left button in this example) is pressed once more,
the drum stays still for a period of time (that can be set) and
then starts to move in the corresponding opposite direction
(counterclockwise). In doing so, the time ramps that were set
together are again used.
Stop function
If both pushbuttons are pressed together, the drum is braked
over an adjustable time ramp until it comes to a downtime
(stop function).
The time ramp used for the stop function is set separately from
the time ramp for the working behavior.
Additional functions
The SPCD closed loop speed control has two additional func-
tions:
• Memory function
The memory function is turned on or off during
commissioning.
If the memory function is on and the stop function is used to
bring the drum to a downtime, the most recent speed and
direction of rotation (that were used immediately before the
stop function was activated) are stored.
Safety switch (also switches off RC)
Left pushbutton
Right pushbutton
Funnel function
Fill level sensor 1
Actual speed 2
Actual speed 1
Setpoint logic
Direction of
rotation Ramps
Memory
Error
monitoring
Correction
calculation
Pump control
Limiter
± 20 %
E
M
G
-
O
F
F
Pump
Fill level sensor 2