Page 437 - Mechatronics with Experiments

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JWST499-c07
JWST499-Cetinkunt
ELECTROHYDRAULIC MOTION CONTROL SYSTEMS 423
Command
input devices
Controller
DC P.S.
DSP
Amp Amp

Open center Open center
Pump valve valve
P
M/E
T

Reservoir
Cylinder Cylinder

FIGURE 7.14: Multi degrees of freedom (multi function) hydraulic circuit. This example shows
a series connection of two hydraulic actuator-valve circuits to supply lines. Valves are
necessarily open-center type in order to supply the circuits in the serial connection when an
earlier valve is in neutral position. The valves closer to the pump have priority over the ones
that are connected later in the series circuit. The pump may be of variable or fixed
displacement type.

circuits: the main flow loop between the pump and motor, the charge loop which supplies
replenishment flow to the main loop as well as supply pressurized flow power used to
actuate the pump displacement, and finally the the drain loop which sends the leakage
flow through the components to the reservoir. The pump control types are discussed in
more detail later. Suffice it to say that the pump displacement can be controlled to regulate
various variables, such as pump output pressure, flow rate. The power necessary to actuate
the main pump displacement control system is provided by the charge pump. The control

Pressure limit valve Drain loop
Main loop
Charge Charge
relief High relief
Pump displacement pressure
piston
relief
valves
Pump Pump Charge Hydraulic
pump
control motor
Loop flushing
valve
valve
Heat Charge loop
Filter
exchanger
Filter
FIGURE 7.15: A typical closed circuit hydrostatic transmission circuit. Reproduced with
permission from Danfoss Power Solutions.