LUT Kone

Heikkinen, J., Luostarinen, L., and Handroos, H. (2012). Virtual environment for
investigating Human Machine Interface in Machines with hydraulic transmissions.
Proceedings of the 7th FPNI PhD Symposium on Fluid Power, Reggio Emilia, Italy, June
27-30, 2012, pp. 225-234.

Heikkinen J., Minav T., Handroos H., Tapia J. (2014) Electric motor based hydraulic motor pump emulator in real time HIL-simulation: Finding The optimum emulator electric motor,
Proceedings of the 8th FPNI PhD Symposium on Fluid Power, Lappenranta, Finland, 2014

The goal of this research is to apply direct-driven hydraulics (DDH) to the concept of zonal (i.e., locally and operation-focused) hydraulics, which is an essential step in the hybridization and automation of machines. DDH itself aims to combine the best properties of electric and hydraulic technologies and will lead to increased productivity, minimized energy consumption and higher robust performance in both stationary and mobile machines operating in various environments. In the proposed setup, the speed and position control of a double-acting cylinder is implemented directly with an electric motor drive in a closed-loop system without conventional control valves and an oil tank. The selection of the location of the hydraulic accumulator and connection of the external leakage lines will also be part of this study. Simulations and experimental research to study the details of the hydromechanical and electrical realization of the DDH are performed.

Hardware-in-the-loop (HIL) setup is used in research, since it allows fast, accurate and easily repeatable testing of hybrid topologies of non-road mobile machinery under realistic conditions. In a previous study, it was shown that a virtual model of a hydraulic machine in a HIL setup can be used for testing by emulating a directly driven hydraulic pump with an electric motor. As the used setup did not completely fulfil the requirements, criterion for choosing a new electric motor was suggested. Therefore, in this research set of initial solution motor parameters to fulfil a minimum settling time of Ts =0.001 seconds for hydraulic pump emulator electric motor torque response was made based on analytical design of a coreless motor. A Matlab/Simulink model of the optimum electric motor for directly driven hydraulic pump emulation was made. According to the simulation, the capability of the designed electric motor in following a 1 kHz torque reference signal was proven.

Direct driven hydraulic drives (DDH) have the advantages of compact high power density in hydraulic systems and flexible control of electric motors. These advantages can benefit non-road mobile machinery (NRMM) applications. However, maintaining high efficiency while working in sub-zero conditions with NRMM is challenging. Therefore, this paper investigates the effect of hydraulic oil on the efficiency of a DDH in a cold environment for an NRMM application. In the DDH setup, the speed and position control of a double-acting cylinder was implemented directly with an electric motor drive in a closed-loop system without the conventional control valves. Efficiency measurements of the DDH setup with two oils (conventional multi-grade and high-performance) were conducted under different operating conditions (speed and payload) and environmental conditions (temperature in °C). The paper provides an evaluation of the electro-hydraulic system and a discussion on the usage of hydraulic oil by non-road mobile working machines in sub-zero conditions. An experimental investigation demonstrated an improvement in efficiency of 5%-unit at 22 °C, from 2%-unit to 5%-unit at 3 °C, and of almost a 10%-unit at temperatures below zero (−10 °C) by changing oil.