A hydraulic cylinder is a mechanical actuator that is widely used in different industries such as construction, manufacturing, aerospace, and offshore oil and gas. Seal wear in hydraulic cylinders ...results in hydraulic fluid leakage or contamination of the hydraulic fluid. Untimely, failure of a hydraulic cylinder increases the maintenance cost and reduces productivity. Therefore, condition monitoring of the hydraulic cylinder is necessary to understand the current state of equipment. In the literature, there have been numerous documented attempts to perform condition monitoring of hydraulic cylinders using different methods, based on fluid properties, pressure, vibration, and acoustic emission. However, there have been limited attempts to present a state-of-the-art review of condition monitoring of hydraulic cylinders. This article presents an overview of the methods used for the condition monitoring of hydraulic cylinders, including the detection of different failure modes using different sensors, the separability of fault conditions using sensor-based features, and the ability to pick up incipient faults by sensor-based features. This information is required for new readers in this area of expertise. This article summarizes different condition monitoring methods that have been used from its early implementation to very recent dates, aiming at clarifying recent advances and identifying challenges in the research of the condition monitoring of hydraulic cylinders. It is anticipated that the information presented in this article will be beneficial for new researchers and provide directions for future research in the area of condition monitoring of hydraulic cylinders.
This paper discusses an identification input for nominal hydraulic arms. First, we focus on an input-output nonlinearity which exists even in the absence of nonlinear friction and prevents us from ...observing and measuring the input-output behaviors. Second, we propose a new identification input based on the physical parameters of hydraulic arms via the special nondimensionalization technique. Third, we show the effectiveness of the new identification input experimentally. Finally, we show an application of the proposed new identification input to observe and measure the input-output behaviors. Especially, in the frequency domain, we identify the uncertainty that was impossible for the conventional identification input.
The article presents an author’s approach to the study of the behavior of plastic hydraulic cylinder structures under load. Plastics as design materials, due to their different properties, behave ...differently from metals. So far, there is little information about hydraulic cylinders made of plastics. They are a technical novelty, and there are no established standards or research methods for them. The tests were carried out on the example of two models of different internal diameter, the smaller one being Ø30 mm and the larger one Ø50 mm. Information was gathered by FEM simulation tests and tests of real models on a special test stand. The simulation section presents geometric models, discrete models and assumed boundary conditions, as well as the results of the performed simulations. For tests of real models, a description of the stand with the measuring equipment used is presented, e.g., laser displacement sensors, as well as the method of conducting the tests and the results. Then, the results are analyzed and compared. Deformations of the examined structures are discussed, e.g., tube swelling or deflection, which seem to be characteristic for plastic cylinders. Finally, the possibility of using selected plastics for the design material of hydraulic cylinders and the suitability of the research method used are assessed.
Mechanical products are becoming more diversified with the continuous development of precision processing and materials technologies. The friction force generated by the O-ring seal in a hydraulic ...cylinder was once considered redundant. However, its utilization has recently been proposed. The hardness of the O-ring and the inner diameter of its groove directly affect the normal pressure between the O-ring and the inner wall of the cylinder, thereby affecting the friction behavior. In order to explore this friction behavior, a strain-based friction force measurement system is developed in this study, and the steady-state and dynamic friction values under different working conditions are studied and discussed in depth. This research on the friction behavior in the cylinder provides a theoretical basis for more convenient design and utilization of the friction force generated between the O-ring and the inner wall of the cylinder.
In order to solve the problems of nonlinearity, uncertainty and coupling of multi-hydraulic cylinder group platform of a digging-anchor-support robot, as well as the lack of synchronization control ...accuracy of hydraulic synchronous motors, an improved Automatic Disturbance Rejection Controller-Improved Particle Swarm Optimization (ADRC-IPSO) position synchronization control method is proposed. The mathematical model of a multi-hydraulic cylinder group platform of a digging-anchor-support robot is established, the compression factor is used to replace the inertia weight, and the traditional Particle Swarm Optimization (PSO) algorithm is improved by using the genetic algorithm theory to improve the optimization range and convergence rate of the algorithm, and the parameters of the Active Disturbance Rejection Controller (ADRC) were adjusted online. The simulation results verify the effectiveness of the improved ADRC-IPSO control method. The experimental results show that, compared with the traditional ADRC, ADRC-PSO and PID controller, the improved ADRC-IPSO has better position tracking performance and shorter adjusting time, and its step signal synchronization error is controlled within 5.0 mm, and the adjusting time is less than 2.55 s, indicating that the designed controller has better synchronization control effect.
Aiming to solve the problems of long transmission chain, large movement inertia of components and high energy consumption of pumping units, this proposes a new pumping unit with direct balance and ...hydraulic drive. Through mathematical modeling and simulation analysis to compare the suspension dynamic characteristics and balance characteristics of the hydraulically driven pumping unit with the conventional one. It turns out that the suspension maximum speed drop 21.14%, the maximum acceleration drops 28.88% and the root mean square torque drops 92.9% on the suspension of the hydraulically driven pumping unit. The experimental results proves that the hydraulically driven pumping unit has significant energy saving efficiency, and achieves more than 30.9% of active power saving rate. Theoretical and practical research results show that hydraulically driven pumping unit is reliable and better energy saving, which provides a basis in theory and engineering practice in application.
A double acting cylinder operation has been fully monitored in its key functional parameters, focused on characterization of end-of-stroke cushioning and starting phases. Being the cylinder ...performance reliant in the piston constructive geometry, the number and location of piston circumferential grooves is a significant parameter affecting the internal cushioning system performance. An eddy current displacement sensor assembled in the piston allows assessment of piston radial displacement inside the cylinder tube, which is directly related with the studied operating phases. Due to such 3D displacements, the piston becomes as an active and self-adjusting element along the functional cycle of the cylinder. Mechanical joints orientation and operating pressure are also relevant parameters affecting piston radial displacement and, thus, the cushioning and starting performance. Computational Fluid Dynamics (CFD) results confirm the observed functional role of the perimeter grooves; the flow and pressure distributions, where develops a significant radial force, are also in accordance with the registered radial displacement.
A vertical isolation device with variable stiffness (VIVS) is developed using multiple hydraulic cylinders, which can form a three dimensional (3D) isolation device with a horizontal rubber bearing. ...The components and control mechanism of the VIVS are explained in detail. A prototype of the VIVS is fabricated to verify its performance by sinusoidal motion tests and shaking table tests. The experimental results show that the variable stiffness characteristics of the VIVS can be achieved, and the isolation period reaches 1.2 s. The shaking table test also verifies the effectiveness of the VIVS in controlling the acceleration. A theoretical model for the VIVS is proposed and validated, and a 60 m single-layer reticulated dome is simulated based on the model. The results indicate that the axial force and acceleration of the structures with VIVS are effectively mitigated with reduced height and displacement of the VIVS.
•A vertical isolation with variable stiffness is developed using hydraulic cylinders.•Various tests are conducted to investigate the performance of the isolation.•A theoretical model of the isolation is proposed and validated.•Numerical analysis is conducted for a single-layer reticulated dome.•The isolation mitigates the responses with reduced height and displacement.
This paper discusses an identification input for nominal hydraulic arms. First, we focus on an input-output nonlinearity which exists even in the absence of nonlinear friction and prevents us from ...observing and measuring the input-output behaviors. Second, we propose a new identification input based on the physical parameters of hydraulic arms via the special nondimensionalization technique. Third, we show the effectiveness of the new identification input experimentally. Finally, we show an application of the proposed new identification input to observe and measure the input-output behaviors. Especially, in the frequency domain, we identify the uncertainty that was impossible for the conventional identification input.
PDF
