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Pump failure is a general concerned problem in the hydraulic field. Once happening, it will cause a huge property loss and even the life loss. The common methods to prevent the occurrence of pump failure is by preventative maintenance and breakdown maintenance, however, both of them have significant drawbacks. This research focuses on the axial piston pump and provides a new solution by the prognostic of pump failure using the classification of machine learning. Different kinds of sensors (temperature, acceleration and etc.) were installed into a good condition pump and three different kinds of damaged pumps to measure 10 of their parameters. Then, several classification models were trained by different machine learning algorithms including Decision Tree, K-Nearest Neighbor, and Neural Network. These classification models can detect the “unhealthy” state of the pump and locate the damaged parts from real-time data. Finally, the performances of these models were evaluated by different metrics including Training Time, Accuracy and etc. According to the results, for the prognostic of axial piston pump failure, the algorithm with the highest accuracy is Fine KNN; while the algorithm that has a good balance of training time and accuracy is Fine Tree; finally, the Deep Neural Network has a good accuracy and can be designed with different hidden layer structures, in addition, the trained net of the Deep Neural Network can also be reserved and retrained with new data.

11th International Fluid Power Conference, 11. IFK, Aachen, Germany, 19 Mar 2018 - 21 Mar 2018; Aachen : [Mainz], 586-595 (2018)., Published by [Mainz], Aachen

11th International Fluid Power Conference, 11. IFK, Aachen, Germany, 19 Mar 2018 - 21 Mar 2018; Aachen : [Mainz], 14-27 (2018)., Published by [Mainz], Aachen

Virtual prototyping of positive pumps and motors is incredibly useful, increasing speed of development and lowering cost. The calculations of fluids discharge pressure, displaced by a swashplate-type-axial piston pump/motor is dependent on the load impedance driven by the unit. The load impedance is estimated by a variable orifice found downstream of the unit. Similarly, the suction line impedance is also estimated with an orifice. The current project aims to evaluate the various loading architectures in their ability to quickly and accurately create the desired impedance. The robustness of the loading architectures was tested on a wide range of pump sizes, speeds, pressures, and displacements. The estimated initial conditions of the loading architectures, such as the orifice areas and line volumes and pressures are very efficient means of converging to the correct discharge pressure. To develop a model, based on past simulation, a full factorial design of experiments (DOE) was performed to generate the required training data set. The DOE revealed the models sensitivity to the normally unknown variables which contributed to large variations in accuracy. However, after analyzing the impact of other variables, an alternate approach was taken. By creating a variant of the simulation, which sets port pressures equal to line pressures, orifice areas can be effectively removed from the equation. In order to compare the performance, ideal valve plates specific to each code variant should be used. This is because arbitrary valve plates may favor one over the other, yielding extraneous conclusions. An existing genetic algorithm found the accuracy was unaffected while greatly improving speed.

Noise control is an important factor in evaluating the design of positive displacement machines. This research project aims to develop new tools in MATLAB, with emphasis on visual approaches, to comprehensively characterize the noise generated by positive displacement machines in spatial, temporal and frequency domains. Sound pressure level (SPL), sound intensity level (SIL) and loudness were calculated and plotted on a measurement surface surrounding the pump, which illustrates the spatial distribution of the sound field. In order to highlight the phenomenon within specific frequency bands, Butterworth filters were used to isolate desired frequencies, such that specific harmonic content or 1/3 Octave bands content can be analyzed. In addition to static visualization methods, videos were created by compressing a series of sphere plots in time to illustrate the dynamic characteristics of the measured sound. Corresponding phase plots were generated at the same time to statically illustrate these dynamic characteristics shown on videos. The successful generation of the various methods of characterizing and visualizing pumps generated noise was evaluated on a large sample set of more than 150 measure grids with nearly 30000 individual microphone measurements. The creation of these analytics has already changed the conversation and challenged the state of the art in hydraulic Noise Vibration and Harshness (NVH).

Axial piston machines of the swashplate type are commonly used in various hydraulic systems and with recent developments in displacement control, it is essential to maximize their efficiency further reducing operation costs as well as improving performance and reliability. This paper reports findings of a research study conducted for the piston-cylinder interface utilizing a novel fluid structure thermal interaction model considering solid body deformation due to thermal and pressure effects in order to accurately predict the transient fluid film within the gap. A large reduction in energy dissipation is possible due to reduced clearances allowable due to the surface shaping of the piston resulting in a reduction in leakage. From this study, it is shown that surface shaping of the piston in combination with a reduced clearance is not only beneficial by improving the efficiency of a machine, but also increases the reliability and the performance of the machine as the load support is enhanced.

Noise emission is a major drawback of the positive displacement machine. The noise source can be divided into structure borne noise source (SBNS) and fluid borne noise source (FBNS). Passive techniques such as valve plate optimization have been used for noise reduction of axial piston machines. However, passive techniques are only effective for limited operating conditions or at least need compromises in design. In this paper, active vibration control of swash plate is investigated for vibration and noise reduction over a wide range of operating conditions as an additional method to passive noise reduction techniques. A 75cc pump has been modified for implementation of active vibration control using the swash plate. One tri-axial acceleration sensor and one angle sensor are installed on the swash plate and a high speed servovalve is used for the swash plate actuation. The multi-frequency two-weight least mean square (LMS) filter synthesizes the servovalve input signal to generate a destructive interference force which minimizes the swash plate vibration. An experimental test setup has been realized using Labview field-programmable gate array (FPGA) via cRIO. Simulation and experimental studies are conducted to investigate the possibility of active vibration control.

The cylinder block/valve plate interface is a critical design element of axial piston machines. In the past, extensive work has been done at Maha Fluid Power Research center to model this interface were a novel fluid structure thermal interaction model was developed which accounts for thermal and elasto-hydrodynamic effects and has been proven to give an accurate prediction of the fluid film thickness. This paper presents an in-depth investigation of the impact of the elastic deformation due to pressure and thermal loadings of the end case/housing on the performance of the cylinder block/valve plate interface. This research seeks to understand in a systematic manner the sensitivity of the cylinder block/valve plate interface to the structural design and material properties. A comparison between simulations results is done by utilizing different end case designs and material compositions, both in the valveplate and end case solids.

Environmental awareness, production costs and operating expenses have provided a large incentive for the investigation of novel and more efficient fluid power technologies for decades. In the earth-moving sector, hydraulic hybrids have emerged as a highly efficient and affordable choice for the next generation hydraulic systems. Displacementcontrolled (DC) actuation has demonstrated that, when coupled with hydraulic hybrids, the engine power can be downsized by up to 50% leading to substantial savings. This concept has been realized by the authors‘ group on an excavator prototype where a secondary-controlled hydraulic hybrid drive was implemented on the swing. Actuatorlevel controls have been formulated by the authors‘ group but the challenge remains to effectively manage the system on the supervisory-level. In this paper, a power management controller is proposed to minimize fuel consumption while taking into account performance. The algorithm, a feedforward and cost-function combination considers operator commands, the DC actuators‘ power consumption and the power available from the engine and hydraulic hybrid as metrics. The developed strategy brings the technology closer to the predicted savings while achieving superior operability.

Positive displacement machines working as hydraulic pumps or hydraulic motors have always been, are and will be an essential part of any hydraulic system. Current trends and future demands on energy efficient systems will not only drastically increase the number of positive displacement machines needed for modern efficient hydraulic circuits but will significantly change the performance requirements of pumps and motors. Throttleless system configurations will change the landscape of hydraulic actuation in aerospace, mobile machines, automotive and many other areas and will definitely open the door for new applications due to its enhanced competitiveness with electric and electro-mechanical systems.

Hydraulic hybrids transmissions have the potentially to substantially improve the fuel efficiency of on road vehicles. In fact recent studies have demonstrated that this technology can improve fuel economy by upwards of 30% over competing electric hybrids. To further improve the fuel economy and performance of this technology a novel blended hydraulic hybrid transmission has been constructed at the Maha Fluid Power Research Center. While this novel hybrid architecture created by the Maha lab has many benefits over conventional systems, there are a number of control challenges present due to several discrete modes of operation. And though improving fuel economy is quite important, in order for a vehicle to gain wide spread acceptance in a global market positive driver perception and comfort must be assured. Thus it is important to develop control schemes which enhance and optimize drivability. Controller development began by improving an existing hydraulic hybrid powertrain model constructed in MATLAB Simulink. Control schemes for individual modes of operation were then proposed and investigated in the improved simulation model. Finally once sufficiently well-developed these control scheme were applied, tuned, and evaluated on the Maha lab’s hydraulic hybrid demonstration vehicle. The controllers developed showed an overall improvement in drivability as well as a great improvement in the transitions between discrete modes of operations. This held true for both the simulation model and more importantly when implemented in the demonstration vehicle. The new controls proposed in this work help to enhance the driver’s perception of a novel and highly efficient hydraulic hybrid transmission.

In this paper a feasibility study has been conducted to determine a technique for the measurement of lubricant fluid film thickness in the piston-cylinder interface of an axial piston pump. The thickness of the lubricant film has a significant impact on the efficiency of the piston pump yet it still remains an uncertainty. If the lubricant film is too thin then friction will cause excessive damage resulting in deformation of interacting surfaces resulting in further uncertainty in thickness measurement. If the lubricant film is too thick then there is excessive leakage which will compromise the efficiency of the system. Acoustic, inductive, capacitive and optical techniques were investigated through literature review and it was decided to investigate further into acoustic techniques. Experimental procedures using ultrasound to measure the lubricant fluid film thickness are investigated and an experimental procedure is explored further into in this paper. The governing factors of measuring fluid film thickness were determined. The effect of surface deformation on lubricant thickness is also investigated and a technique of imaging using ultrasonic sensors is presented. A CAD model displaying sensor locations and mounting apparatus in piston-cylinder interface is also presented. A feasible method for the measurement of lubricant fluid film thickness is proposed. These measurements will be used to validate existing models which predict the behavior of lubricant fluid film.

Variable displacement vane pumps (VDVP) are one type of positive displacement pumps used in automatic transmission vehicles for lubricating the gears, cooling the transmission and actuating the clutches. Though fixed displacement pumps are widely used, they output a constant effective flow at a given speed. Depending on pump sizing considerations, the pump can be oversized at high speeds because flow demand of the transmission is independent of engine speed. The excess flow returns to the tank through an orifice that causes the oil to heat up, increasing the energy required for cooling and reducing the efficiency of the transmission. A VDVP is used because the effective flow is adjustable to meet transmission demands any speed. The VDVP studied in this paper is unstable because of a feedback loop between pressure fluctuations at the pump’s outlet and the control system. To design a better VDVP with increased stability and controllability, a simulation model of the current pump design needs to be validated against measurements. Therefore a test rig design with required pump modifications is proposed in this study. Six pressure sensors are installed such that they measure the pressure in each of the pump’s displacement chambers. A LVDT is used to measure the pump’s eccentricity changes as the displacement is varied. Part of this study was to develop a custom MATLAB script that combines all the sensor data to show a pressure profile for each displacement chamber. The pump modifications for sensor installation and test rig implementation was designed.