Enhanced energy efficiency of industrial application by direct driven hydraulic unit

Direct Driven Hydraulic (DDH) systems, which are characterized by a closed circuit type and a speed-controlled pump, offer a possibility of reaching higher energy efficiencies compared to the traditional open circuit type valve-controlled systems, and simultaneously offering high accuracy and dynamics. This study presents experimental results gained with a DDH system applied to an industrial position control application. The results include the system behavior regarding the accuracy of position control, pressures, power, and energy consumption with three different system structures: basic DDH, load- compensated DDH and load-compensated and damped DDH. It was found that compared to valve-controlled hydraulics, DDH system offered potential for significant energy savings, especially if combined with hydraulic load compensation. However, without damping, the motion involved marked vibrations in the end of the stroke. Vibrations were avoided by introducing damping, but at the cost of reduced energy efficiency.Peer reviewe

Experimental Study on Fast and Energy-Efficient Direct Driven Hydraulic Actuator Unit

In this experimental study, a Direct Driven Hydraulics (DDH) system of the closed circuit type was utilized for cyclic vertical actuation in heavy load material handling. The actuator was controlled by a speed-controlled fixed displacement pump. The high energy saving potential of this system has been demonstrated in previous studies by the authors, but the dynamic characteristics of the ramped and P-controlled base system were considered unsatisfactory. Therefore, the system was implemented with an open-loop S-curve control that utilized a pre-calculated RPM (revolutions per minute) profile for the electric motor in order to realize a smooth actuator and load transition as a function of time. The results indicate that S-curve control is exceptionally well suited for producing a controlled lifting–lowering rapid motion with a heavy load, while still keeping the actuator chamber pressures within acceptable limits. In comparison, the motion produced by P-control was characterized by large unwanted pressure peaks together with velocity fluctuations and vibrations at the end of the stroke. Using a combination of S-curve control and hydraulic load compensation, a mass of 1325 kg could be moved 0.26 m in less than 0.5 s. The load compensation reduced the energy consumption by 64%, which would allow downsizing the electric motor and enable cost-efficient DDH implementation

Experimental Investigation of a Directly Driven Hydraulic Unit in an Industrial Application

Government-enforced regulations have led to increasing demands for energy efficient solutions in the industry. To diminish the losses of hydraulic systems and to increase their energy efficiency, several pump control methods have been developed. In this work, a new experimental direct drive actuator solution, powered directly by a servo motor controlled hydraulic pump-motor, is evaluated. As an additional innovative feature, a load compensating hydraulic circuit has been introduced in order to reduce power consumption even further. The study presents results of performance measurements of this new concept.Peer reviewe