Browsing by Subject "Fluid power"

Now showing 1 - 6 of 6
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    Design and control of fully flexible valve actuation systems for camless engines
    (2012-12) Gillella, Pradeep Kumar
    The motivation to improve the fuel efficiency and reduce emissions of the internal combustion engine comes from the dwindling oil reserves and the increased concerns about climate change. A key step towards realizing these improvements is to introduce flexibilities into the mechanisms used for air and fuel management by replacing the mechanical devices with mechatronic systems. The introduction of fuel injection systems in place of the carburetors resulted in significant improvements due to the additional flexibilities in fuel management. The traditional air management systems use camshaft based mechanisms to actuate the intake/exhaust valves. The benefits offered by fully flexible valve actuation and the limitations of the camshaft based systems motivate the development of a "Camless valve actuation system". Research in this area during the past two decades has led to the development of several concepts. However, the stringent performance requirements to ensure reliable operation and the shortcomings of the previously developed concepts has impeded the widespread deployment of these systems. In this research, we propose to address the problem from two perspectives. A design based solution capable of achieving fully flexible operation using inexpensive components while requiring simplified controllers is first introduced. It is followed by the development of a systematic procedure for optimizing the design of a key component in this system to improve it performance and robustness. The second topic focuses on the implementation aspects of a new control algorithm to enable precise tracking of the engine valve reference profile. The effectiveness of the linear time invariant controllers based on the internal model principle for steady state operation of the engine is leveraged to enable tracking control during engine speed transients by extending the control framework to the time-varying setting. The challenges associated with the time-varying nature of the controller are revealed and the developed solutions help its implementation and validation on experimental hardware. The proposed framework can easily be extended to other engine subsystems as well as other general rotational machinery.
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    Design of a hydraulic dexterous manipulator for minimally invasive surgery
    (2013-09) Berg, Devin Rodney
    The research described here identifies the limitations of existing robotic surgical platforms, which include the balance between the scale of the robot and its manipulability in terms of range of motion, load capacity, and tool capability, then develops a means of overcoming them by taking advantage of fluid power as an enabling technology with its inherent power density and controllability. The approach described here differs significantly from conventional surgical robots in that the robot is embedded within the surgical device itself, whereas in the conventional system, a general-purpose robot is used to manipulate various surgical tools. This is done in order to demonstrate that fluid power can be used advantageously for the design of embedded surgical robotic systems for minimally invasive surgery. To enable the design of a fluid powered surgical robot, it was first necessary to identify the design requirements for a robot of this nature as well as the considerations unique to this approach. To this end, a quantification of the necessary load capacity for natural orifice robots was conducted. Further, through a review of the literature in the fields of surgery and robotics, considerations of necessary workspace and limitations for the prevention of tissue damage were explored. The results of these analyses are presented. The technologies that comprise this novel surgical robotic system include a hydraulic control valve, actuation units, and an enabling structure. The intended application of these technologies introduced numerous limitations and challenges to the design process. The most stringent of these limitations was that of overall size, due to the realities of patient anatomy, which prevented the use of commercially available hydraulic components. An assemblage of components to achieve the aforementioned design requirements is described including the design of a novel hydraulic control valve to enable manipulation of three actuators using a single valve sized to fit within the working channel of a surgical endoscope. The advantage of the described approach is that the device enables greater miniaturization, improves cost effectiveness, and has better ease of mobility. The mobility and the relaxed requirements for operating room cleanliness can be potentially useful for mobile clinics, out-patient clinical settings, and on the battlefield. Being more cost effective and having a small overall size, the robotic assisted surgical devices can be widely deployed, even in rural or other less technology intensive environments. Through careful review of the literature and analytical evaluation of the various proposed concepts, it was possible to arrive at a design that meets the needs of modern surgical interventions while addressing the perceived limitations of existing surgical robotics. Through the efforts described in this dissertation, much new information was produced and developments resulted. The considerations of hydraulic power for surgical robots were evaluated and are applicable to other surgical tasks where hydraulic power may be used advantageously. A quantification of the load requirements for surgical robots performing abdominal procedures was produced which will provide a guide for other researchers developing surgical robots. These values are difficult to find in the literature and are a valuable resource for the field. An alternative, simplified model for predicting the behavior of continuum beams under load was developed to provide an inverse formulation for computing beam shape and end loads. This is useful as continuum beams are widely used for minimally invasive surgical manipulators as well as in a wide variety of other applications. Finally, a novel valve concept and two possible designs realizing this concept were developed. These valve designs facilitate control over the three actuators in an antagonistic arrangement. Further, the valve designs enable proportional control of the three actuators at a size scale not commercially available. In summary, the design of a novel hydraulic surgical manipulator as a summation of its parts has been performed. This design demonstrates the feasibility of the fluid power approach to embedded minimally invasive surgical robotics. The pursuit of this research has provided many unique challenges and the work presented here has addressed many of them, as well as laid the foundation for future developments in the application of hydraulic power to the growing field of surgical robotics for minimally invasive surgery.
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    Design, modeling, and control of a novel architecture for automatic transmission systems
    (2013-06) Mallela, Virinchi
    Automotive transmissions are required to efficiently transfer energy from the engine to the wheels. Automatic transmissions are one of the most widely used transmission systems in the United States. This transmission houses a hydraulic system which is used to actuate the clutch system to realize different gear ratios. Currently, these clutches are primarily controlled in open-loop using hydraulic valves in a physical embodiment designed specifically for a given transmission system in order to perform precise pressure and flow control. To meet the increasing demand for higher fuel economy, transmissions with greater number of gear ratios are being introduced. The hydraulic architecture is becoming increasingly complicated with more clutches and control elements. With the advancement of MEMS technology, the sensor-based direct feedback control of clutches becomes possible. This paper first analyzes the current architecture of transmission hydraulic system and then presents a new architecture for the feedback-based clutches. The proposed architecture is further validated through experiments using hardware-in-the-loop system.
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    The development of a power management strategy for a hydraulic hybrid passenger vehicle
    (2014-07) Meyer, Jonathan James
    The amount of energy being consumed is increasing each year, with the highest sector being the transportation industry. Within the transportation sector, the highest area of oil consumption is in the small and lightweight vehicle category. With increasing oil prices and decreasing supply, methods of reducing oil consumption have been studied. One is by developing a hybrid vehicle, which combines the internal combustion engine with an additional power source. For lightweight vehicles, electric hybrid vehicles have been thoroughly studied. While hydraulic hybrids have been studied for larger applications such as delivery trucks and buses, little research has been done in the area of small, lightweight vehicles. Hydraulics have a higher power density than electronics, so hydraulic hybrids can get better performance than electric hybrids while reducing fuel consumption.In this research, a series and power-split architecture is studied for a passenger vehicle. Because of the additional hydraulic power source along with energy storage, the optimal way to control these vehicles is not known. Therefore, an energy management strategy must be developed to determine the optimal strategy for splitting the power between the engine and the hydraulics.Three different methods are used to develop the energy management strategy - a rule-based strategy based on dynamic programming results, stochastic dynamic programming, and model predictive control. An experimental hardware-in-the-loop setup is used to replicate a series hybrid in which the different energy management strategies are tried. Through simulation and experimentation, it was found that not one strategy works best in all scenarios, and variables such as knowledge of duty cycle and energy storage must be taken into account when developing the strategy.An input-coupled power-split hybrid was also studied, which combines the mechanical efficiency of the parallel hybrid with the engine management of a series hybrid. Through a series of simulations, a strategy that declutched the engine from the drivetrain while the vehicle is stopped gave a significant reduction in fuel consumption. Another advantage of the power-split architecture is the ability to operate the vehicle in different modes by declutching the engine and removing hydraulic units by the use of valves. By using this strategy, the fuel economy can be almost doubled over a baseline strategy which operates only in power-split mode. Finally, the size of the accumulator can have an effect on the fuel consumption, with a smaller accumulator leading to less fuel consumed; however, if the accumulator is too small, the performance starts to degrade with a downsized engine.The results of this research can be used to develop a toolbox that can be used for developing energy management strategies by having the user enter a model, objective function, and duty cycle for a system. By using other information, such as knowledge of duty cycle, the toolbox can determine the best method of developing the control strategy, reducing the amount of time and resources for developing an optimal control strategy.
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    Modeling and Experimental Validation of Disc and Reed Style Check Valves for Hydraulic Applications
    (2016-08) Knutson, Anthony
    The goal of this thesis is to develop a computationally inexpensive, accurate, and practical mathematical model of a hydraulic reed style check valve. While the modeling of disc style check valves is well represented in literature, reed valve modeling research has focused on applications in air compressors and internal combustion engines, where the working fluid has low density, viscosity, and bulk modulus. However, in a hydraulic system, the fluid – namely oil – is dense, viscous, and stiff, contributing additional physical effects that must be considered. Furthermore, the operating pressure in hydraulic systems is higher than in pneumatic systems, creating additional challenges from a structural perspective. In this thesis, a one degree of freedom hydraulic disc and reed style check valve model were developed using a hybrid analytical, computational, and experimental approach. The disc valve equation of motion was derived from Newton’s second law applied to the disc considering forces including pressure, spring reaction, and drag. Euler- Bernoulli beam theory was used to derive the reed valve equation of motion. In each case, the valve flow rate was modeled as quasi-steady orifice flow using an empirical discharge coefficient. A non-contact method of experimentally measuring check valve position during operation using a laser triangulation sensor (LTS) was developed. An acrylic viewing window was installed in the check valve manifold to allow optical access. To precisely measure position through air, acrylic, and oil, refraction of the laser light was accounted for using Snell’s law. Finally, the disc and reed valve models were validated in the context of a single cylinder hydraulic piston pump across a range of operating conditions. Pump delivery, which is a measure of volumetric efficiency, and check valve position were chosen as the validation metrics. Experimental results showed that both the disc and reed check valve model accurately predicted the timing of valve opening and closing. The disc valve model predicted pump delivery within 5% of measured values for all cases while the reed valve model predicted pump delivery within 3% of measured values for all cases.
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