scholarly journals Experimental Study of the Direct Drive Hydraulic System with the Torque Mode

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 941
Author(s):  
Chenyang Zhang ◽  
Hongzhou Jiang
Keyword(s):  
Transfer Function ◽  
Dynamic Characteristics ◽  
Control Strategy ◽  
Hydraulic System ◽  
Parallel Mechanism ◽  
Dynamic Pressure ◽  
Second Order ◽  
Direct Drive ◽  
Pressure Feedback ◽  
Speed Mode

The torque mode is more suitable for the direct drive 6 degree of freedom (6-DOF) parallel mechanism than the speed mode that both dynamic coupling and current coupling among motors are easily solved, but its key parameters and dynamic characteristics have never been studied, which are important and are the goals of this paper. First the hydraulic system of the direct drive 6-DOF parallel mechanism is simplified. Then the transfer function of the direct drive hydraulic system with the torque mode is deduced together with that of the speed mode. Finally, comparative experiments are conducted. Results show that the dynamic characteristics of the system with the torque mode which are generally worse than those with the speed mode, are mainly determined by the parameters of the motor-pump second-order element of the transfer function composed of two under-damped second-order elements, proportion differentiation (PD) control strategy and dynamic pressure feedback (DPF) control strategy are useful for the system with the torque mode, but practical and effective methods are still needed.

scholarly journals PD Plus Dynamic Pressure Feedback Control for a Direct Drive Stewart Manipulator

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1125 ◽  
Author(s):  
Chenyang Zhang
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Dynamic Characteristics ◽  
Control Strategy ◽  
Dynamic Pressure ◽  
Control Input ◽  
Servo Motor ◽  
Direct Drive ◽  
Pressure Feedback ◽  
Current Coupling

In order to ensure good dynamic characteristics, servo valve is usually adopted as the drive part of Stewart manipulator which causes huge power consumption, while direct drive electro-hydraulic servo system has the advantages of energy saving, simple structure, convenient installation, and low failure rate. But its dynamic characteristics are so poor that it can only be applied to occasions where quick response is not needed. On the consideration above, following works are done in this paper. Since current coupling exists in the control system based on the speed of the servo motor as the control input, the control system of the direct drive Stewart manipulator is established based on the current of the servo motor as the control input in which the current coupling can be solved. In order to improve the dynamic characteristics of the direct drive Stewart manipulator, a Proportion Differentiation (PD) plus dynamic pressure feedback control strategy is also put forward in this paper, which is verified by using a simulated hydraulically driven Stewart manipulator. Simulation results show that both dynamic coupling and current coupling are solved and the control strategy proposed in this paper can significantly increase the bandwidths of all degrees of freedom.

scholarly journals A Generalized Control Model and Its Digital Algorithm for Aerospace Electrohydraulic Actuators

Proceedings ◽  
2020 ◽  
Vol 64 (1) ◽  
pp. 31
Author(s):  
Shoujun Zhao ◽  
Keqin Chen ◽  
Xiaosha Zhang ◽  
Yingxin Zhao ◽  
Guanghui Jing ◽  
...  
Keyword(s):  
Transfer Function ◽  
Dynamic Pressure ◽  
Resonance Effect ◽  
Notch Filter ◽  
Digital Signal ◽  
Second Order ◽  
Large Engine ◽  
Combined Control ◽  
Pressure Feedback ◽  
Digital Algorithm

It is difficult to describe precisely, and thus control satisfactorily, the dynamics of an electrohydraulic actuator to drive a high thrust liquid launcher engine, whose structural resonant frequency is usually low due to its heavy inertia and its complicated mass distribution. A generalized model is therefore put forward for maximum simplification and sufficient approximation, where a second-order transfer function is used to model the heavy mass-spring nature of the large engine body outside of the rod position loop, another second-order transfer function with two zeros and two poles representing the hydro-mechanical composite resonance effect in the closed rod position loop. A combined control strategy is applied to meet the stringent specification of static and dynamic performances, including a notch filter, a piecewise or nonlinear proportional, integral and differential (PID) controller and a feed-forward compensation. The control algorithm is implemented in digital signal processors with the same software structure but different parameters for different aerospace actuators. Compared to other approaches, this one makes it easier to grasp the system resonance nature, and, most importantly, the traditional dynamic pressure feedback (DPF) is replaced with the convenient digital algorithm, bringing prominent benefits such as a simplified design, reduced hardware cost and inherent higher reliability. The approach has been validated by simulation, experiments and successful flights.

scholarly journals Research on Heat Transfer Dynamic Characteristics of Composite Layer Based on Laplace Transform

2019 ◽  
Author(s):  
Chunyu Xu ◽  
Junhua Lin ◽  
Wenhao Liu ◽  
Yuanbiao Zhang
Keyword(s):  
Heat Transfer ◽  
Composite Materials ◽  
Temperature Distribution ◽  
Transfer Function ◽  
Dynamic Characteristics ◽  
Transfer Functions ◽  
Composite Layer ◽  
Engineering Application ◽  
Second Order ◽  
Inverse Transformation

This paper predict and effectively control the temperature distribution of the steady-state and transient states of anisotropic four-layer composite materials online, knowing the density, specific heat, heat conductivity and thickness of the composite materials. Based on the transfer function, a mathematical model was established to study the dynamic characteristics of heat transfer of the composite materials. First of all, the Fourier heat transfer law was used to establish a one-dimensional Fourier heat conduction differential equation for each composite layer, and the Laplace transformation was carried out to obtain the system function. Then the approximate second-order transfer function of the system was obtained by Taylor expansion, and the Laplace inverse transformation was carried out to obtain the transfer function of the whole system in the time domain. Finally, the accuracy of the simplified analytical solutions of the first, second and third order approximate transfer functions was compared with computer simulation. The results showed that the second order approximate transfer functions can describe the dynamic process of heat transfer better than others. The research on the dynamic characteristics of heat transfer in the composite layer and the dynamic model of heat transfer in composite layer proposed in this paper have a reference value for practical engineering application. It can effectively predict the temperature distribution of composite layer material and reduce the cost of experimental measurement of heat transfer performance of materials.

Application Analysis of Dynamic Pressure Damper in Hydraulic Systems

2015 ◽  
Vol 724 ◽  
pp. 287-294
Author(s):  
Xu Yao Mao ◽  
Yun Fei Peng ◽  
Chao Wu ◽  
Jun Hua Hu ◽  
Hong Yuan Ding
Keyword(s):  
Hydraulic System ◽  
Dynamic Pressure ◽  
System Stability ◽  
Hydraulic Systems ◽  
System Parameters ◽  
Application Analysis ◽  
Pressure Feedback ◽  
Pressure Impact ◽  
Hydraulic Cylinders

Typical hydraulic systems with inertia executive components like hydraulic cylinders are generally low in damping and lack of stability. Adding DPD to systems is an easy and effectual method to solve these problems. The performance of a mechanical dynamic pressure feedback DPD applied in a common hydraulic system was simulated while the influences of the structure and system parameters on DPD and the system were analyzed. Further research on characteristic optimization was carried out by adding accumulators to DPD. It shows that the DPD can practically improve the system stability and contain the pressure impact. The accumulators should be set appropriately before the damping orifices and have a certain ability to absorb pressure impact.

Study on Dynamic Characteristic in Hydraulic System Based on Bypass Method by the AMESim

2014 ◽  
Vol 703 ◽  
pp. 298-302
Author(s):  
Jun Zhang ◽  
Yong Wu ◽  
Hong Mei Tang ◽  
Chun Ren Tang ◽  
Xian Hua Li
Keyword(s):  
High Pressure ◽  
Numerical Analysis ◽  
Dynamic Characteristics ◽  
Measurement System ◽  
Hydraulic System ◽  
Dynamic Pressure ◽  
Pressure Side ◽  
Dynamic Flow ◽  
System Flow ◽  
Side Flow

s. At present, based on the bypass method to measurement the dynamic of the high pressure side flow in hydraulic system became more and more. In order to analysis the dynamic characteristics, the bypass method measurement system flow schematic was introduced in this paper, the dynamic flow of the main oil and the system was obtained by using dynamic flow of the side oil. Meanwhile, the dynamic pressure of the main oil was obtained by using dynamic pressure of the side oil. From the results of numerical analysis indicates that it is feasible to use the bypass method to get the characteristics of the dynamic flow and dynamic pressure in the system.

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