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This paper compares two different rule-based power management (PM) strategies, in terms of their resultant fuel consumptions, through a simulation study as applied to a hybrid hydraulic multi-actuator displacement controlled (DC) system. Specifically, the system analyzed is a mini-excavator, wherein the digging functions are powered using four variable displacement pump/motors - these units are also shared by the auxiliary functions. In addition, the on-board hydraulic energy storage device, or accumulator, is charged or discharged using an additional pump/motor, called the storage unit. A parallel architecture is used for the hybrid system wherein the additional pump/motor is on the engine shaft, running at the same speed as the engine (and the other four pumps). An aggressive and fast, digging cycle was used to size the storage unit and accumulator, as well as to compare the performance of the two different strategies.

The paper presents a new computer based design method for valve plate design using the simulation program CASPAR and the extension tool AVAS. CASPAR is based on a non-isothermal gap flow model considering time dependent gap heights and surface deformations due to high pressure loads for all connected gaps of swash plate axial piston machines. Among others the program allows the prediction of oscillating forces exerted on machine parts and the calculation of effective flow pulsation on both ports as a function of design and operating parameters. Together with the calculated instantaneous cylinder pressure the flow pulsation and oscillating forces can be taken as criterion to evaluate the effectiveness of design measures for noise reduction during the design phase, i.e. before prototype production. The models used in the program have been verified by different measurements on pumps and motors.

Modern on-road vehicles have been making steady strides when it comes to employing technological advances featuring active safety systems. However, off-highway machines are lagging in this area and are in dire need for modernization. One chassis system that has been receiving much attention in the automotive field is the steering system, where several electric and electrohydraulic steering architectures have been implemented and steer-by-wire technologies are under current research and development activities. On the other hand, off-highway articulated steering vehicles have not adequately evolved to meet the needs of Original Equipment Manufacturers (OEM) as well as their end customers. Present-day hydrostatic steering systems are plagued with poor energy efficiency due to valve throttling losses and are considered passive systems relative to safety, adjustability, and comfort.

Noise generation in axial piston machines can be attributed to two main sources; fluid borne and structure borne. Any attempt towards noise reduction in axial piston machines should focus on simultaneous reduction of these two sources. A multi-parameter multi-objective optimization approach to design valve plates to reduce both sources of noise for pumps which operate in a wide range of operating conditions has been detailed in a previous work (Seeniraj and Ivantysynova, 2008). The focus of this paper is to explain the background and to demonstrate the functionality and usefulness of the methodology for pump design.