This thesis proposes a new type of hydraulic valve: an adjustable-ratio flow divider. This valve attempts to split one input flow into two output flows in a predetermined ratio, independent of load pressure or total flow. The valve uses a two dimensional structure to form a two-stage valve with only one moving part; the pilot stage uses the spool s rotary position, and the main stage uses its linear position. This arrangement allows for a cheaper, simpler valve with smaller volumes (translating into faster response). The ratio of outlet flows can be set on the fly by the angular position of the spool, driven by a stepper motor or other low-power input. In order to evaluate the initial feasibility of the concept, steady state and dynamic models were developed and the effects of the physical parameters were studied. Two non-linear non-derivative multiobjective optimization strategies were used to determine the optimum parameters for a prototype. Finally, the prototype s performance was experimentally examined and appears to work as expected.

A commercial backhoe has been modified for haptic control research at Georgia Tech's Fluid Power and Motion Control Center (FPMC). Electrohydraulic valves and feedback sensors have been retrofitted to the backhoe and interfaced with a haptic joystick through a computerized control system. The resulting system provides force feedback to the hand of the operator as he or she manipulates the bucket with the joystick in Cartesian space. This system has been constructed for use as a platform for ongoing research in the area of haptic controls for the fluid power industry. The work presented herein is divided into seven chapters. The first chapter introduces the haptic backhoe concept and provides some motivation for the project. The second chapter presents the current state of haptics-for-hydraulics research as presented in scientific literature. The third chapter presents kinematic and dynamic modeling of the haptic backhoe components for use both in simulation and control. The fourth chapter presents simulation results from the model derived in the preceeding chapter. The fifth chapter describes the design of the physical system. The sixth chapter presents initial test results of the backhoe moving under closed-loop haptic control. The last chapter describes the current state of the system and suggests several areas for future exploration. It is hoped that the haptic backhoe will continue to serve as a useful research tool for many years into the future.

Thesis (M.S.)--University of Wisconsin--Madison, 1970. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

<p>Fluid power education would benefit from the adoption of an alternative to traditional hands-on instructional methods. Hands-on education is invaluable because it offers students experience interacting with and controlling fluid power systems and components, but systems are typically space-consuming and expensive. The study sought to prove the viability of mixed reality (MR) as an alternative to traditional hands-on fluid power instruction through the creation of MR lab exercises. A summary of design methodology was created to demonstrate how virtual fluid power components were modeled and presented in a mixed reality environment. Data was collected from students enrolled at Purdue University who participated in traditional and mixed reality fluid power lab exercises. Student responses were expected to express a positive reception of mixed reality as a fluid power instructional tool. The study anticipated that utilizing mixed reality in a fluid power laboratory setting would increase student comprehension of fluid power concepts. Educational variables were limited by restricting testing to students within the advanced fluid power course of Purdue University’s Polytechnic Institute. Students in this course provided feedback that drew comparisons between traditional and mixed reality instructional methods. Labs were created to remain within the course schedule so as not to disrupt course curriculum. Data from Likert-type surveys were analyzed from pre- and post-lab questionnaires as well as student feedback from their experience after completing each mixed reality (MR) lab. Analysis showed that MR is a viable alternative to traditional hands-on instructional methods as students showed an increase in material comprehension of both fluid power components and concepts. Students perceived MR as a beneficial instructional tool but continued to show preference towards physical interactions with components. A combination of instructional methods is recommended.</p> <p>  </p>

Excessive fluid-borne noise in hydraulic systems is a problem the fluid power industry has long struggled to address. Traditional noise control devices such as Helmholtz resonators, tuning coils, and Herschel-Quincke tubes are generally too large for fluid power systems unless the speed of sound in the device can be reduced. A compliant lining can achieve this effect, but compliance (and lossy compliance) has had little attention in noise control in general, and in fluid power in particular. One means to achieve compliance in these devices, especially at elevated pressures, is through a liner made of syntactic foam, which in this case is a urethane host matrix with embedded hollow, polymer microspheres. The material properties at elevated pressure are unknown by the liner manufacturer, but are known to be pressure- and temperature-dependent. Therefore, the effect of hydrostatic pressures from 2.1-21 MPa and temperatures from 20-45 C on the liner properties, thus the device performance, are studied. For a Helmholtz resonator, a theoretical model is fit to experimentally-measured transmission loss of the device using a least-squares routine, which solves the inverse problem for the complex bulk modulus of the liner. These material properties are used to compare a predictive model of a tuning coil to experimental data, and in a parameter study of a Herschel-Quincke tube. The compliance of the liner is found to lower the effective sound speed by an order of magnitude and decrease the volume of the cavity of a Helmholtz resonator by up to two orders of magnitude. This work is expected to result is more compact noise control devices for fluid power systems.

This thesis presents a solution enabling lower losses in hydraulic actuator systems. A mobile fluid power system often contains several different actuators supplied with a single load sensing pump. One of the main advantages is the need of only one system pump. This makes the fluid power system compact and cost-effective. A hydraulic load often consists of two ports, e.g. motors and cylinders. Such loads have traditionally been controlled by a valve that controls these ports by one single control signal, namely the position of the spool in a control valve. In this kind of valve, the inlet (meter-in) and outlet (meter-out) orifices are mechanically connected. The mechanical connection makes the system robust and easy to control, at the same time as the system lacks flexibility. Some of the main drawbacks are The fixed relation between the inlet and outlet orifices in most applications produce too much throttling at the outlet orifice under most operating conditions. This makes the system inefficient. The flow directions are fixed for a given spool position; therefore, no energy recuperation and/or regeneration ability is available. In this thesis a novel system idea enabling, for example, recuperation and regeneration is presented. Recuperation is when flow is taken from a tank, pressurized by external loads, and then fed back into the pump line. Regeneration is when either cylinder chambers (or motor ports) are connected to the pump line. Only one system pump is needed. Pressure compensated (load independent), bidirectional, poppet valves are proposed and utilized. The novel system presented in this thesis needs only a position sensor on each compensator spool. This simple sensor is also suitable for identification of mode switches, e.g. between normal, differential and regenerative modes. Patent pending. The balance of where to put the functionality (hardware and/or software) makes it possible to manoeuvre the system with maintained speed control in the case of sensor failure. The main reason is that the novel system does not need pressure transducers for flow determination. Some features of the novel system: Mode switches The mode switches are accomplished without knowledge about the pressures in the system Throttle losses With the new system approach, choice of control and measure signals, the throttle losses at the control valves are reduced Smooth mode switches The system will switch to regenerative mode automatically in a smooth manner when possible Use energy stored in the loads The load, e.g. a cylinder, is able to be used as a motor when possible, enabling the system to recuperate overrun loads The system and its components are described together with the control algorithms that enable energy efficient operation. Measurements from a real application are also presented in the thesis.

Fuel cost represents a significant operating expense for owners and fleet managers of hydraulic off-highway vehicles. Further, the upcoming Tier IV compliance for off-highway applications will create further expense for after-treatment and cooling. Solutions that help address these factors motivate fleet operators to consider and pursue more fuelefficient hydraulic energy recovery systems. Electrical hybridization schemes are typically complex, expensive, and often do not satisfy customer payback expectations. This paper presents a hydraulic energy recovery architecture to realize energy recovery and utilization through a hydraulic hydro-mechanical transformer. The proposed system can significantly reduce hydraulic metering losses and recover energy from multiple services. The transformer enables recovered energy to be stored in a high-pressure accumulator, maximizing energy density. It can also provide system power management, potentially allowing for engine downsizing. A hydraulic test stand is used in the development of the transformer system. The test stand is easily adaptable to simulate transformer operations on an excavator by enabling selected mode valves. The transformer’s basic operations include shaft speed control, pressure transformation control, and output flow control. This paper presents the test results of the transformer’s basic operations on the test stand, which will enable a transformer’s full function on an excavator.

Modern production systems have to allow high performance cutting processes in a flexible production system environment at a high level of accuracy. The final workpiece accuracy is mainly influenced by the thermo-elastic behavior of the machine tool and can be improved by additional measures, compensation strategies and an optimized machine design. These measures are often implemented as stand-alone solutions. According to the Industry 4.0 all information should be connected in a single model of the actual machine state to increase machining accuracy. It is therefore necessary to integrate upcoming smart fluid power systems into the machine network.

Axial piston machines are widely used in the industry ranging from aerospace, agriculture, automotive, heavy machinery, etc. These applications require better pumps and motors to meet current market demands such as higher power density in hydraulic units, smarter pumps (diagnostics and prognostics), higher efficiencies, and compactness. The current state-of-the-art in pump design is mostly based on heuristic design approach with very limited use of numerical toolssince the invention of this positive displacement machine until the present time. The numerical tools being used do not capture the physical phenomena in the thin fluid film between the rotating group components. The work presented in this dissertation aims to demonstrate the feasibility of virtual prototyping utilizing a combination of in-house developed multi-domain models and to propose a novel computational based design methodology for axial piston machines. The methodology is an iterative process between the virtual components in 3D CAD models and the function evaluations for the design requirements utilizing the numerical models which provide an accurate prediction to the behavior of the mechanical components working together. To validate the proposed methodology a case study on a 24 cc/rev axial piston machine was carried out. The machine was built virtually, simulated,and optimized for desired performance. A physical prototype was built based on the case study and tested successfullyfor forty-five operating conditions.