The Speed-variable Switched Differential Pump
Concept (SvSDP) is a continuation of the en-
ergy efficient hydraulic Speed-variable Differen-
tial Pump (SvDP) concept original proposed by
Bosch Rexroth A/S. The SvSDP consist of three
gear pumps driven by a single electric motor
connected directly to the inlet and outlet ports
of differential cylinders. A SvSDP system is
designed and dimensioned. To allow for gen-
eral evaluation of the concept, a multi-purpose
test bench for hydraulic systems is also designed
and constructed. A detailed, non-linear dynamic
model of the system is developed, and the pa-
rameterization of the model is conducted based
on experimental results. The model is linearized
and Relative Gain Array (RGA) analysis is used
to identify the amount of cross couplings in the
system. It is found that decentralized control of
the system is not immediately applicable, why
decoupling strategies are investigated. No ex-
perimental verification is made of the designed
closed loop control systems, but from simulation
results it is found, that the decoupled control
strategy gives acceptable and consistent perfor-
mance of the closed loop system. The simulated
closed loop position tracking shows maximum
tracking errors of less that 3 mm even for non-
realizable ramp trajectories.