Replacing a Constant Pressure Valve Controlled System with a Pump Controlled System

Traditionally, a typical hydraulic circuit utilized in stationary
industrial applications is based on valve operated actuation. One
realization of such a system is a constant pressure circuit
employing a hydraulic accumulator as an energy reserve and
pressure stabilizer. The pump is used to maintain the desired
pressure level, for example by using a variable displacement
pump that controls the displacement setting based on the
pressure level.
The main benefit of this system architecture is its ability to
produce high output powers with a very low response time.
However, it is not the most energy efficient and in many cases,
not the most space efficient solution. The efficiency of this
system type is reduced mainly by the need to choke the pressure
difference between the set system pressure and the actual
pressure need in the actuator. By directly controlling the actuator
via controlling the pump’s output flow with an electric servo
motor, the throttling losses of the valve controlled system can be
avoided. In addition, this enables the usage of closed circuits
which in terms removes the need for a large reservoir.
In this study, the replacement of a valve controlled hydraulic
system with a pump controlled system in an industrial stationary
material handling machine is investigated. The machine’s work
cycle consist of continuous consecutive lifting and lowering
motions of one end of a platform pivoted at the opposite end. The
study consist of designing the replacing circuit topology, of
dimensioning the hydraulic components utilizing a created
Simulink-based tool and of a simulation based analysis on the
dynamic properties of the designed hydraulic system.