Direct Driven Hydraulic System for Skidders

Abstract

This paper investigates potential uses of a novel direct driven electro-hydraulic systems for articulated forestry tractors (skidders), due to these systems having notably higher energy efficiencies compared to classical electro-hydraulic systems that are currently being used in skidders for steering, lifting the front and the rear plate, as well as for operating the double-drum winch. A detailed analysis of the skidder rear plate mechanism is carried out, and static force profiles of hydraulic cylinders are obtained for the rear plate based on mechanism dynamics and measurement data from the literature. Thus, obtained results have been used to emulate the real-life force profiles in laboratory experiments featuring both the classical and the proposed direct driven hydraulic systems for the purpose of comparative analysis of their energy and fuel efficiency. These results are subsequently used to estimate the skidder fuel consumption and possible fuel savings over the entire vehicle life span for the realistic vehicle utilisation scenario. The main result is that fuel consumption can be reduced up to five times in the case of direct driven hydraulic system, thus effectively resulting in return of investment period of about four years in the case of skidder being retrofitted with direct driven hydraulic system.

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

“…Another group of experimental studies can be identified in which the implemented hardware is limited to the power-train, including the cylinders, and the load force is emulated by applying weights or force from load cylinders. Two examples of this are [14], where static load conditions of a skidder are simulated by lifting and lowering different weight plates, and in [15], another hydraulic cylinder is used to apply a load to the tested cylinder, which the authors mention as a way of testing the performance in a realistic duty cycle. Such an approach might be sufficient to evaluate the static efficiencies of a single actuator, but realistic cycles with multiple mutually influencing actuators and realistic inertia for dynamic investigations cannot be tested.…”

“…Furthermore, the efficiency or consumption of the whole implement system with all major actuators is of interest; thus, boom, tilt, and telescope cylinders should be present in the setup connected by the real kinematic chains. Accordingly, setting up a test rig for a single actuator as in [14][15][16][17], would not be effective. Instead, an existing conventional nine-tonne telehandler has been chosen as the test platform, which can be seen in Figure 1, to incorporate the original kinematic chains, inertia, and control interface.…”

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].…”