Riassunto analitico
The current work aims at developing a 3D mechanical model of a Bent Axis hydraulic unit (BAU) using a lumped parameter multibody modelling approach. The BAU falls under the category of axial piston machines and is capable of functioning both as a pump and a motor. Moreover, our current machine has the capability of varying the displacement volume during operation. In the current treatise, we will focus on it’s working as a pump with a fixed displacement volume. The 3D mechanical model serves the purpose of forming the mechanical counterpart of a pre-existing hydraulic model of the system, which when coupled together form an integrated model of the entire unit.
The lumped parameter modelling approach is adopted as it is computationally less intensive compared to a detailed 3D multibody modelling of a system. Moreover, such a model can be easily coupled to other pre-existing hydraulic sub-models of our system. We also wish to analyze the gap between the cylinder block and the valve plate during pump’s motion. Such an analysis doesn’t necessarily require absolute pinpoint dynamics of other components of the system (which are not directly connected to the cylinder block). Hence, adopting a lumped parameter approach serves our purpose well.
To accomplish our job, we rely on Simcenter AMESim 3D Mechanical library for the modelling purpose. We start by building a kinematic model of our system, respecting the pump architecture, without inclusion of any kind of forces. Once such a model is found to function well, we apply external forces on this system, extracted from the pre-existing hydraulic model, in order to obtain a dynamic model of our pump. Using this 3D dynamic model, we can observe various internal reaction forces and torques in our system. Since our BAU is acting as a pump, the most critical parameter which we can observe from this model is the torque required to drive our system. This driving torque from our 3D lumped parameter multibody model is then compared to the one from our pre-existing model (which consists of the hydraulic part coupled with simplified mechanical submodels of the system), to verify the reliability of our 3D model. Finally, we run the two models for various operating conditions and compare their torques with theoretical torque values. Additionally, we try to observe if our model is able to predict the gap between the cylinder block and the valve plate during pump’s operation. The 3D multibody lumped parameter model was found to be in accordance with our pre-existing model in terms of driving torque and reaction forces. On the other hand, this model wasn’t able to depict the gap between the cylinder block and the valve plate due to our underlying hypothesis of using a universal joint for torque transmission. The universal joint inhibits the translatory motion of the cylinder block along it’s rotary axis, thus depriving us of the chance to observe the gap variation upon subjecting the cylinder block to fluid forces. A final chapter discussing the limitations in our model and scope for it’s development is provided at the end.
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Abstract
The current work aims at developing a 3D mechanical model of a Bent Axis hydraulic unit (BAU) using a lumped parameter multibody modelling approach. The BAU falls under the category of axial piston machines and is capable of functioning both as a pump and a motor. Moreover, our current machine has the capability of varying the displacement volume during operation. In the current treatise, we will focus on it’s working as a pump with a fixed displacement volume. The 3D mechanical model serves the purpose of forming the mechanical counterpart of a pre-existing hydraulic model of the system, which when coupled together form an integrated model of the entire unit.
The lumped parameter modelling approach is adopted as it is computationally less intensive compared to a detailed 3D multibody modelling of a system. Moreover, such a model can be easily coupled to other pre-existing hydraulic sub-models of our system. We also wish to analyze the gap between the cylinder block and the valve plate during pump’s motion. Such an analysis doesn’t necessarily require absolute pinpoint dynamics of other components of the system (which are not directly connected to the cylinder block). Hence, adopting a lumped parameter approach serves our purpose well.
To accomplish our job, we rely on Simcenter AMESim 3D Mechanical library for the modelling purpose. We start by building a kinematic model of our system, respecting the pump architecture, without inclusion of any kind of forces. Once such a model is found to function well, we apply external forces on this system, extracted from the pre-existing hydraulic model, in order to obtain a dynamic model of our pump. Using this 3D dynamic model, we can observe various internal reaction forces and torques in our system. Since our BAU is acting as a pump, the most critical parameter which we can observe from this model is the torque required to drive our system. This driving torque from our 3D lumped parameter multibody model is then compared to the one from our pre-existing model (which consists of the hydraulic part coupled with simplified mechanical submodels of the system), to verify the reliability of our 3D model. Finally, we run the two models for various operating conditions and compare their torques with theoretical torque values. Additionally, we try to observe if our model is able to predict the gap between the cylinder block and the valve plate during pump’s operation. The 3D multibody lumped parameter model was found to be in accordance with our pre-existing model in terms of driving torque and reaction forces. On the other hand, this model wasn’t able to depict the gap between the cylinder block and the valve plate due to our underlying hypothesis of using a universal joint for torque transmission. The universal joint inhibits the translatory motion of the cylinder block along it’s rotary axis, thus depriving us of the chance to observe the gap variation upon subjecting the cylinder block to fluid forces. A final chapter discussing the limitations in our model and scope for it’s development is provided at the end.
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