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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.

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.

A new control concept was developed to minimize the power losses of a hydrostatic drive line for off-road vehicles. The drive line control concept is based on two separate closed loop controls, one for the hydrostatic transmission and another for the combustion engine. The command values for both control loops are calculated under consideration of the characteristic curves of the combustion engine and the losses within the hydrostatic transmission, using an on-line optimization procedure. This paper discusses the benefits of this control concept based on a comparison of typical realistic driving manoeuvres. Objective of the investigations for different output powers is the potential of fuel savings under different operating conditions. A hardware-in-the-loop test rig for the investigated hydrostatic propel drive is used for the experimental validation.

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.

Over the last decade, a number of hybrid architectures have been proposed with the main goal of minimizing energy consumption of off-highway vehicles. One of the architecture subsets which has progressively gained attention is hydraulic hybrids for earth-moving equipment. Among these architectures, hydraulic hybrids with secondary-controlled drives have proven to be a reliable, implementable, and highly efficient alternative with the potential for up to 50% engine downsizing when applied to excavator truck-loading cycles. Multi-input multi-output (MIMO) robust linear control strategies have been developed by the authors' group with notable improvements on the control of the state of charge of the high pressure accumulator. Nonetheless, the challenge remains to improve the actuator position and velocity tracking.