Experimental Investigations of Partially Valve-, Partially Displacement-Controlled Electrified Telehandler Implements

Abstract

The next generation of electrified heavy-duty mobile machines (HDMMs) requires more efficient hydraulic systems—to save energy and to compensate for the limited capacities of available mobile electric energy sources. This study is experimentally demonstrating the functionality, dynamic performance, and efficiency of such a more efficient but also cost-effective system. The demonstrator is a conventional nine-tonne telehandler that has been transformed by replacing the diesel engine with an electric machine (EM) and changing the boom function from valve to displacement control. Since the system control and the resulting dynamics are not trivial, key aspects of it are explained in the paper. With the functional system, achievable consumption reductions could be obtained by measuring five different representative work cycles repeatedly and comparing the average consumption values to the consumption of a purely valve-controlled but also electrified reference version. In four of five cycles, an average reduction of 21–31% was achieved, which confirms the simulation results from previous studies and the effectiveness of the concept. However, one cycle—characterized by serial movements and longer breaks of the boom movement—showed a reduction of only 3% and that the effectiveness of the concept can also be lower in certain cases that depend mainly on the operator.

Energy Efficient Excavator Functions Based on Electro-Hydraulic Variable-Speed Drive Network

“…Even though many hydraulic systems contain more than a single cylinder, limited attention has so far been given to dedicated multi-axis electro-hydraulic drives. This field has, however, begun to emerge in the last few years ranging from solutions combining displacement units in variable-speed and/or displacement-controlled cylinders with valve-controlled cylinders in a mix [6,7] to more disruptive drive design approaches such as the so-called HHEA [8,9] and so-called electro-hydraulic variable-speed drive networks [10][11][12]. The latter approach generally contains a tremendous amount of possible drive architectures, with this number increasing exponentially with the number of cylinders (or motors) in a system.…”

Experimental Tests on the Influence of Accumulated Pressure Energy on the Response Time of a Hydraulic Cylinder under External Load Actuated in a Classic and Distributed System Structure

“…However, the main recent development direction seems to be towards the analysis of hydraulic systems having distributed valve structure and employing two-way, two-position (2/2) valves. Such systems are integrated on the level of the electric control system [24][25][26][27][28]. Attempts at developing electro-hydraulic systems with high dynamic parameters are also present in research on new electrically controlled valves [29] and on systems employing multi-chamber cylinders [30].…”