In this article the authors have studied a hydraulic system configuration where each actuator/supply system comprises an electrically controlled variable displacement pump/motor working in an open circuit together with four separate electrically controlled valves. Performance, operability and energy consumption are evaluated in a wheel loader, first with its original load sensing hydraulic system and then modified with a completely new pump controlled hydraulic system. Measurements published in this article demonstrate the advantages and drawbacks of pump control in an open circuit compared both to a pump controlled, closed circuit solution and to a valve controlled, load sensing system. Performance is evaluated by looking at the fuel consumption, productivity, and operability of a wheel loader. Theoretical calculations of energy efficiency including the dominant losses in system components are evaluated and validated. Fuel consumption is measured and put side by side with measurements of the same machine equipped with a load sensing hydraulic system.
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