Mosquitoes drink using a pair of in-line muscular pumps in the head that draw liquid food through a long drinking channel termed as proboscis. Experimental investigations of mosquito drinking using synchrotron x-ray indicate two modes of drinking, a predominantly occurring continuous mode in which the anterior cibarial and posterior pharyngeal pumps expand cyclically at a constant phase difference and an isolated burst mode in which the pharyngeal pump expansion is several orders of magnitude larger than in the continuous mode. The objective of this thesis is to explain the mechanics and functional implication of this two-pump dual mode drinking of a mosquito. A reduced order mathematical model suggests that the primary role of the pharyngeal pump is in the burst mode. Since the precise geometry of the pump during drinking is yet not known, the drinking mechanism is modeled using different pump geometries based on morphological constraints in the animal. The model shows the continuous mode as being more effective in terms of energy expenditure, while the burst mode creates a large pressure difference across the proboscis which might be used to clear an obstruction in the channel or prime the channel. The hypothesis regarding the ability of a mosquito to self-clear an obstruction is analyzed by modeling the presence of an air bubble inside the system. The model indicates that air bubbles maybe able to stop flow during continuous mode drinking, and these same bubbles can be cleared by switching temporarily to burst mode drinking. / Master of Science

This paper describes a novel concept for a low cost variable delivery external gear pump (VD-EGP). The proposed VD-EGP is based on the realization of a variable timing for the connections of the internal displacement chambers with the inlet and outlet ports. With respect to a standard EGP, an additional element (slider) is used along with asymmetric gears to realize the variable timing principle. Previously performed tests confirmed the validity of the concept, for a design capable of varing the flow in the 65%-100% range. Although the VD-EGP concept is suitable for various flow control system typologies (manual, electro-actuated, hydraulically flow- or pressure- compensated), this paper particularly details the design and the test results for a prototype that includes both a manual flow control system and a pressure compensator. Flow vs pressure and volumetric efficiency curves are discussed along with transient (outlet flow fluctuation) features of the VD-EGP.

Fluid power technology has been widely used in industrial practice; however, its energy efficiency became a big concern in the recent years. Much progress has been made to improve fluid power energy efficiency from many aspects. Among these approaches, using a valve-less system to replace a traditional valve-controlled system showed eminent energy reduction. This thesis studies the valve-less solution-pump displacement controlled actuators- from the view of controls background. Singular perturbations have been applied to the fluid power to account for fluid stiffness; and a novel hydraulic circuit for single rod cylinder has been presented to increase the hydraulic circuit stabilities. Recursive Least Squares has been applied to account for measurement noise thus the parameters have fast convergence rate, square root algorithm has further applied to increase the controller's numerical stability and efficiency. It was showed that this technique is consistent with other techniques to increase controller's robustness. The developed algorithm is further extended to a hybrid adaptive control scheme to achieve desired trajectory tracking for general cases. A hardware test-bed using the invented hydraulic circuit was built up. The experimental results are presents and validated the proposed algorithms and the circuit itself. The end goal of this project is to develop control algorithms and hydraulic circuit suitable for industrial practice.

This paper describes a novel concept for a low cost variable delivery external gear pump (VD-EGP). The proposed VD-EGP is based on the realization of a variable timing for the connections of the internal displacement chambers with the inlet and outlet ports. With respect to a standard EGP, an additional element (slider) is used along with asymmetric gears to realize the variable timing principle. Previously performed tests confirmed the validity of the concept, for a design capable of varing the flow in the 65%-100% range. Although the VD-EGP concept is suitable for various flow control system typologies (manual, electro-actuated, hydraulically flow- or pressure- compensated), this paper particularly details the design and the test results for a prototype that includes both a manual flow control system and a pressure compensator. Flow vs pressure and volumetric efficiency curves are discussed along with transient (outlet flow fluctuation) features of the VD-EGP.

Hydraulics has always been the first choice of actuation in off-road, construction and mining vehicles due to its power density, low cost, built in cooling and lubrication. However, the current state of our environment along with stricter regulations has brought light to newer technologies within hydraulics to improve the existing system. This urge to enhance efficiency and reduce energy consumption has led to a point where new technologies must be evaluated. One such technology is the programmable hydraulic pump called the digital displacement pump (DDP). This new pump may have the potential to revolutionize mobile hydraulics as it can be used to improve part load efficiencies, response and make it easier to control from a system perspective. The DDP is a radial piston pump that has been fit with solenoid on/off valves at the inlet of each cylinder to control the flow of the working fluid. The displacement setting of the pump depends on the displacement of each cylinder controlled digitally by the 'active' inlet valve. The pump can act as a single unit to supply one circuit or it can dedicate pistons for supplying several circuits in parallel using different pump outlet configurations. They can be setup to run in pressure controlled or flow controlled systems to achieve the above mentioned flow sharing capability. An energy study based on two fixed drive cycles (short and intermediate) are conducted on the existing system of a loader used for mining called the ST14 Battery. A breakdown of the energy consumption in the machine is created to look at the impact of the three main actuators (boom, bucket and steering), pump losses and throttling losses have. The losses due to simultaneous load handling and the energy that can be saved by swapping the pumps with a digital displacement pump are also found out and analysed. A model of the existing hydraulic system is made using Simulink and Hopsan using the data and results from the energy study. It will be used to simulate and evaluate future system architectures. This model is then used to simulate a system architecture where the existing pumps are swapped with digital displacement pumps. This architecture is more energy efficient due to the higher energy efficiency of the pump. The findings from the energy study and simulations are compared and results are obtained regarding power losses, energy consumption and overall usability of the models. The addition of the two DDP’s instead of the existing inline pumps has resulted in energy savings resulting in 4% more running time in the intermediate cycle and 5.6% in the short cycle while keeping the functionality of the machine.