Theoretical background of hydraulic drive control system analysis for testing piston hydraulic cylinders

Abstract

Introduction. The durability and performance of hydraulic machines is determined through life tests. At that, various braking devices (mechanical, electric, hydraulic, etc.) are used for strength loading of the hydraulic motor, as a result of which a significant amount of energy is lost. This can be avoided if the method of rotational motion with energy recovery is used during life tests. This approach is applicable for hydraulic pumps, motors, and hydraulic cylinders.Materials and Methods. A test bench is presented, the design of which provides recreation of the conditions most appropriate for the field operation of hydraulic cylinders. In this case, energy recovery is possible. To solve the research problems, methods of mathematical modeling were used, the basic functional parameters of the proposed design were calculated. The determination of the pressure increment at various points in the hydraulic system is based on the theory of volumetric rigidity. When modeling the motion of the moving elements of the bench hydraulic system, the laws of rotor motion are used.Research Results. In the structure of the test bench, the cylinders in question are located in the pressure main between the hydraulic pump and the hydraulic motor. This enables to significantly reduce the bench itself and to save a significant amount of energy due to its recovery. A basic hydraulic diagram of the test bench for piston hydraulic cylinders is presented, in which the operation of the moving elements of the system is shown. A mathematical modeling of the hydraulic system of the bench is performed. A kinematic diagram of the mechanism for transmitting motion between test cylinders is shown.Discussion and Conclusions. The system of equations presented in the paper shows how the increment of pressure at the selected nodal points of the energy recovery system is determined (in particular, how the increment depends on time, reduced coefficient of volumetric rigidity, operating fluid consumption, and piston areas). The velocities of the hydraulic pistons are determined according to the kinematic scheme of the mechanical transmission of the bench. Thus it can be argued that, thanks to the solution presented in the paper, the life test results of hydraulic cylinders will adequately reflect their operation under rated duties.

Analysis of non-spool throttle flow dividers for synchronous hydromechanical drives

“…An example of such a design is a spring-type flow divider [1][2][3][4][5], the design scheme of which is shown in Figure 1.…”

“…However, it also has a number of serious drawbacks: -firstly, the role of adjustable hydraulic resistances here is performed by the inter-turn gaps of the spring, which imposes very strict requirements on the accuracy of their design dimensions; -secondly, the stiffness of the springs and the membrane element significantly affect the accuracy of the divider; -thirdly, a pressure drop corresponding to the pressure drop in synchronized hydraulic motors acts on the membrane element separating the output chambers, which significantly reduces the accuracy of the divider. Another way to avoid moving precision pairs in the flow divider is to use an elastic ring as a shut-off and regulating element [6][7][8][9]. Figure 2 shows the design diagram of such a flow divider.…”

Simulation of a synchronous hydrodynamic system based on a throttle flow divider of a non-valve type

“…Synchronization of the movements of the output links in an extensive multi-circuit hydromechanical system is complicated by both variable external loading and elastic properties of the hydraulic system itself. Many factors affecting the stability of the hydromechanical system do not allow at the initial stages of design to give an unambiguous answer about the degree of influence of one or another element included in the system [6][7][8][9][10][11][12].…”

Simulation of the testing process of reciprocating hydraulic cylinders with energy recovery

“…As a result of these searches, a test method with energy recovery of hydraulic machines (pumps and motors) of rotational motion was proposed [1][2][3]. The proposed method has shown its effectiveness, and therefore stands have been developed on its basis for conducting tests with energy recovery and hydraulic reciprocating machines (hydraulic cylinders) [4][5][6][7][8].…”