Optimal Control Theory Applied to Pressure-Controlled Axial Piston Pump Design

Lin, S. J.; Akers, A.

doi:10.1115/1.2896167

Cited by 18 publications

(6 citation statements)

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“…It is customary to model the volumetric flow-rate across a hydraulic control valve using the classical orifice-equation which assumes steady, incompressible and inviscid flow conditions. While these assumptions are not strictly adhered to in the case of this analysis, the use of the classical orifice-equation is justified based upon its common utility in research that is similar [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and the mathematical expediency that this equation offers. Using the classical orifice-equation the volumetric flow-rate in an out of the valve may be written as…”

Section: Control Pressurementioning

confidence: 99%

“…Baz summarizes previous work in his article and suggests that the past emphasis has been placed on optimizing the frequency response of the pump at specific operating conditions rather than synthesizing the overall pump behavior to obtain specific performance under various load disturbances. Akers and Lin [2][3][4] have investigated applications of optimal control theory for a pump utilizing a single-stage and a two-stage servo valve. In his work, he developed an optimal control law for such a system and found that the response frequency obtained by using a two-stage valve was slightly faster when compared to a single-stage valve and that the peak pressures were reduced by a factor of 2.…”

Section: Introductionmentioning

confidence: 99%

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Physical Limitations for the Bandwidth Frequency of a Pressure Controlled, Axial-Piston Pump

Manring

Mehta

2011

Journal of Dynamic Systems, Measurement, and Control

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The objectives of this paper are to identify the design parameters that have the greatest impact on the bandwidth frequency of a pressure controlled, axial-piston pump. This study is motivated by the fact that a physical limitation for these machines has been observed in practice, as it has been difficult to increase the bandwidth frequency much beyond 25 Hz. Though much research has been done over the past thirty years to understand the dynamical behavior of these machines, the essential design-characteristics that determine the bandwidth frequency of the pump remain elusive. In part, this is due to the fact that the machine is complex and when coupled with a hydraulic control valve that is disturbed by steady and transient fluid-momentum effects this dynamical property becomes difficult to assess. In order to achieve the objectives of this research, this paper presents the most comprehensive pump-and-valve model of a pressure controlled, axial-piston machine available in the literature to date. The pump model includes the effects of the discrete pumping-elements acting on the swash plate, while the valve model includes both steady and transient fluid-momentum forces. To identify the dominate features of the model, nondimensional analysis is employed and the complexity of the model is subsequently reduced by eliminating negligible terms. Furthermore, a closed-form expression for the bandwidth frequency is employed and perturbation analysis is used to identify the dominant set of parameters that impact the bandwidth frequency of the pump. In conclusion, it is shown that, by far, the greatest impact on the bandwidth frequency may be achieved by reducing the swept volume of the control actuator and by increasing the flow capacity of the control valve.

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Section: Control Pressurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Physical Limitations for the Bandwidth Frequency of a Pressure Controlled, Axial-Piston Pump

Manring

Mehta

2011

Journal of Dynamic Systems, Measurement, and Control

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“…An optimal controller was designed for pressure regulation of an axial piston pump by Lin and Akers, 10,11 and the control performance was improved by considering the servo valve dynamics. Grabbel and Ivantysynova 5 have developed a nonlinear model of the servo pump.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear supply pressure control for a variable displacement axial piston pump

Wei

Guo

Fang

et al. 2015

Proceedings of the Institution of Mechanical Engineers, Part I:

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For many electro-hydraulic pump-controlled systems, supply pressure control of the hydraulic pump is of great importance. However, the control performance is significantly affected by unknown time-varying load flow requirements. To improve the supply pressure tracking performance in the presence of unknown time-varying load flow disturbances, a nonlinear controller is designed based on the control-oriented mathematical model presented in this article. First, a disturbance observer is used to estimate the unknown time-varying load flow; a nonlinear feedforward controller is then derived using the differential flatness property of the system based on the estimated load flow; in addition, a feedback controller is implemented to stabilize the system. Sliding mode control is also used to compensate for load flow estimation error. The stability of the whole system is proved using Lyapunov theory. Experimental results demonstrate that the proposed control strategy has good supply pressure tracking performance.

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“…ECHPs are important components of pump control systems [4], which are characterized by their excellent energysaving performance. Therefore, ECHPs' mechanical design, modeling, simulation and control algorithm have been studied for a long time, and are still important research topics [5][6][7][8][9][10]. There are many applications of ECHPs, such as hydraulic injection molding machines [11,12], hydraulic presses [13,14], hydraulic elevators [15], etc.…”

Section: Introductionmentioning

confidence: 99%

Improvements to the measurement of electrically controlled hydraulic pumps’ flow/pressure characteristics

Tao¹,

Liu²,

Gu³

et al. 2011

Meas. Sci. Technol.

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To increase the measurement accuracy, and also to automate the measurement operation, we modify the electrically controlled hydraulic pumps’ (ECHPs’) flow/pressure performance characteristic description and improve the test method in existent standards. According to ECHPs’ working principle, we divide ECHPs’ operation into two models: constant flow operating mode (CFOM) and constant pressure operating mode (CPOM). A direct drive servo-proportional control valve (DDV) is used to load the test pump. In the CFOM, we change the pressure load at a constant rate by driving the DDV's displacement with nonlinear feedback and a proportional–integral (PI) controller. In the CPOM, we take advantage of the DDV's inherent linearity between its input signal and output flow, and change the flow load at a constant rate by using open-loop spool displacement control. A mathematic model is built for the derivation of a stable condition and the analysis of steady-state pressure tracking error. The theoretical analysis shows that the feedback linearization and PI controller with negative proportional and integral gains are able to track a slope pressure load command with a desired rate. The test results also show that the mathematical model is valid and the proposed method can improve the measurement accuracy remarkably.

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Optimal Control Theory Applied to Pressure-Controlled Axial Piston Pump Design

Cited by 18 publications

References 0 publications

Physical Limitations for the Bandwidth Frequency of a Pressure Controlled, Axial-Piston Pump

Physical Limitations for the Bandwidth Frequency of a Pressure Controlled, Axial-Piston Pump

Nonlinear supply pressure control for a variable displacement axial piston pump

Improvements to the measurement of electrically controlled hydraulic pumps’ flow/pressure characteristics

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