A number of hydraulically driven machines are subjected to cyclic loads. Also these
loadcycles may sometimes be completely changed. This situation for the workload is
found typically in transmissions of production machines.
Conventional hydraulic transmissions are difficult to adjust to these variable load
sequences with respect to energy-consumption. In this paper a new concept for the
hydraulic energy supply for cyclic loads is presented. The proposed system is based
on a conventional pump-accumulator energy supply system. A conventional
accumulator system can save energy in cyclic loaded machines. but the reduction
of the losses is limited by the introduction of system dependent losses.
In the proposed energy supply the potential of energy saving is nearly full exploited.
In this system both the pump and the accumulator may be connected to or
disconnected from the system. The hydraulic energy supply can thus be switched to
a flow- or to a pressure system. Proper choice of the switch-times or duration of the
time of connection during a cycle can lead to system pressure and system flow
closely following the desired pressure and flow of the load sequence. For different
load cycles a different set of optimal switch-times have to be calculated in order to
minimise the losses in the hydraulic power supply. In this paper attention will be
paid to the method used to determine the optimal set of switch-times for a given
load sequence. The optimization has to deal with a non-linear system with nonlinear
constraints. The design of optimal systems will be discussed and the
theoretical results for energy saving will be shown. These theoretical results are
compared with some practical results. Finally. the practical implementation of the
proposed system will be discussed.
|Title of host publication||Innovations in fluid power : international workshop, University of Bath, 21st-23rd September 1994|
|Editors||C.R. Burrows, K.A. Edge|
|Place of Publication||New York|
|Publication status||Published - 1995|
|Name||Fluid power series|