Cylinder System Research Articles

A Feature-Extraction-Based Adaptive Refinement Method for Solving the Reynolds Equation in Piston–Cylinder System

A fast local refinement algorithm based on feature extraction is developed. In the mesh-based Reynolds equation solutions, two refinement features based on the physical parameters of fluid lubrication are firstly defined, namely, pressure value feature and pressure gradient feature. Then, a fast adaptive strategy different from the traditional methods based on residuals or recovery errors is constructed according to the features, which are expected to determine the element needed to be refined. Considering the update requirement of the feature parameters, an adaptive update strategy for feature parameters is also developed. Finally, the feasibility of the scheme is verified on a single-cylinder gasoline engine. Results show that the current algorithm can effectively reduce the computational scale while ensuring the computational accuracy of the mesh-based model, compared with the traditional global and local refinement strategy.

Distribution Mechanism of Asymmetric Axial Piston Pump

Pump-controlled single-rod hydraulic cylinders are energy-saving and efficient, which is the development direction of hydraulic systems in the future. However, the flow imbalance caused by the unequal effective areas of the two chambers of single-rod hydraulic cylinders has always restricted the development and application of pump-controlled single-rod hydraulic cylinders. The flow rate of the inlet and outlet ports of the ordinary axial piston pump is equal and the flow rate of the large and small chambers of the single rod hydraulic cylinder does not match. In order to solve this problem, the ordinary axial piston pump is improved into an asymmetric axial piston pump, on this basis, the flow distribution mechanism of the asymmetric axial piston pump is explored, and the design theory of the asymmetric axial piston pump is improved. Theoretical analysis of the relationship between the angle of the distribution window of the asymmetrical axial piston pump and the area ratio of the single-rod hydraulic cylinder is carried out, and its mathematical model is derived. Design of valve plates for asymmetrical axial piston pumps to match single rod hydraulic cylinders with different area ratios. The physical model of the asymmetrical axial piston pump and the asymmetrical axial piston pump controlled single-rod hydraulic cylinder system was established in the computer simulation software AMESim. The simulation analysis of the inlet and outlet flow of the asymmetric axial piston pump under different working conditions and the matching of the asymmetric axial piston pump and the single-rod hydraulic cylinder with different area ratios. The simulation results show that the use of an asymmetrical axial piston pump can compensate the flow imbalance caused by the unequal effective areas of the two chambers of the single-rod hydraulic cylinder, so that the flow of the asymmetrical axial piston pump and the single-rod hydraulic cylinder can completely match.

Modelling and Simulation of Two-Float Oscillating Flapping-Wing Wave Energy Converter

In order to achieve an efficient collection of wave energy and stable power output, a two-float oscillating flapping-wing wave energy converter is proposed. Based on the hydraulic conversion system of the multi-chamber cylinder, a hydraulic conversion and merging system of the multi-chamber cylinder is created. The composition and working principle of the system, as well as the parameters of the acquisition mechanism, hydraulic conversion and merging system, are determined. AQWA is used to simulate the flapping-wing angular displacement response, and AMESim is used to build the simulation model of the acquisition mechanism, the hydraulic conversion and merging of multi-chamber cylinders, and the power conversion and energy storage system. The research results show that the system can work stably under level 3 and 4 sea conditions, and the input power of the battery is stable at about 46.5kW and 56.5kW, respectively. The rationality and feasibility of the two-float oscillating flapping-wing wave energy converter are verified by simulation.

Effect of the geometric configuration of the pendulum system of tandem cylinders (PSTC) on the hydrokinetic energy conversion efficiency of wake-induced vibration

Effect of the geometric configuration of the pendulum system of tandem cylinders (PSTC) on the hydrokinetic energy conversion efficiency of wake-induced vibration

Wave interaction with a concentric bottom-mounted cylinder system with dual porous ring plates

The interaction between linear surface waves and a concentric bottom-mounted cylinder system has been investigated using the eigenfunction expansion approach. This system contains an outer porous cylinder and an inner impermeable cylinder, which are connected by dual porous ring plates. Both cylinders are surface-piercing and rigidly installed on the flat bottom of the ocean, while the porous ring plates are fixed below the free water surface. The analytical solution of the velocity potentials can be obtained by matching the boundary conditions. After obtaining the velocity potentials, the wave force and free surface elevation are computed. The numerical results obtained for limiting cases agreed well with the published results. The results of the study show that reducing the draft, spacing, and permeability of the dual plates all contribute to reduce the horizontal force of the inner cylinder. However, the significance of the lower plate is mainly to cope with the condition where the water surface is lower than the upper plate.

Optimal Energy Consumption and Response Capability Assessment for Hydraulic Servo Systems Containing Counterbalance Valves

Abstract Counterbalance valves (CBVs) are broadly applied in hydraulic manipulators, which is essential to ensure safe operation while moving a heavy load. They inevitably introduce additional energy consumption and poor dynamic performance. For the manipulator joint in tunnel boring machines, smooth and precise motion control has to be realized. However, for the forward design considerations, in this case, no systematic work has been done to determine the component parameters based on an energy-saving approach and to derive the natural frequency of the joint at the hydraulic level. To fill this gap, this paper proposes a forward design approach for the proportional valve-controlled hydraulic cylinder system containing CBVs, which is a basic hydraulic configuration adopted for the manipulator joint. Specifically, the optimization model aiming at the minimum energy consumption is defined and improved to solve the key parameters, including the pilot ratio of the CBV and the area ratio of the cylinder. By considering constraints, the other component parameters could be further calculated. After that, the theoretical derivation of natural frequency is given to evaluate the response capability of the system. The overall design procedure is presented to determine the cylinder, CBV, control valve, and constant pressure supply. Based on the validated numerical model, the energy-based design principle is proven effective and could ensure that energy saving is not less than 5% and not more than 36% on average. Furthermore, the natural frequency obtained by the sweep test is verified to be consistent with the theoretical value, and the impact of this parameter on control performance is analyzed. The results indicate that the proposed approach has an excellent guide for the forward design of such systems.

Unstable outer cylinder whirl of concentric double rotating cylinder system

Unstable outer cylinder whirl of concentric double rotating cylinder system

Unstable inner cylinder whirl of concentric double rotating cylinder system

Unstable inner cylinder whirl of concentric double rotating cylinder system

Multi-model adaptive PID control of variable speed pump-controlled hydraulic cylinder system

Multi-model adaptive PID control of variable speed pump-controlled hydraulic cylinder system

Learning-Based Nonlinear Model Predictive Controller for Hydraulic Cylinder Control of Ship Steering System

The steering mechanism of ship steering gear is generally driven by a hydraulic system. The precise control of the hydraulic cylinder in the steering mechanism can be achieved by the target rudder angle. However, hydraulic systems are often described as nonlinear systems with uncertainties. Since the system parameters are uncertain and system performances are influenced by disturbances and noises, the robustness cannot be satisfied by approximating the nonlinear theory by a linear theory. In this paper, a learning-based model predictive controller (LB-MPC) is designed for the position control of an electro-hydraulic cylinder system. In order to reduce the influence of uncertainty of the hydraulic system caused by the model mismatch, the Gaussian process (GP) is adopted, and also the real-time input and output data are used to improve the model. A comparative simulation of GP-MPC and MPC is performed assuming that the interference and uncertainty terms are bounded. Consequently, the proposed control strategy can effectively improve the piston position quickly and precisely with multiple constraint conditions.

Energy Losses Related to Ring Pack Wear in Gasoline Car Engine

Decreasing production and rising prices of cars, especially those with electric drive, lead to longer use of cars with internal combustion engines. It can be assumed that in the future, more and more cars powered by such engines with high mileage and therefore high wear will be used. Engine wear leads to reduced efficiency and increased emissions. This paper analyzes the impact of wear of the piston–rings–cylinder system components on energy losses associated with gas leakage from the combustion chamber and friction of the rings against the cylinder liner in a car spark-ignition engine. A ring pack model was used for the analyses. The input data for the simulation were gained in measurements made on the engine test stand and measurements of the wear of the engine components used in the car. The energy losses associated with blow-by in an unworn engine ranged from 1.5% of the indicated work at high load to almost 5% at low load. In the engine after 300,000 km, these losses increased to 2.5% and 7.5%, respectively. Ring friction losses in an unworn engine ranged from 1.5% at high load to 9% at low load. The effect of wear on these losses was smaller. They increased by only 0.1% at high load and 1% at low load.

Experimental investigation of flow past three-cylinder rotating system

Wake interactions from a three-cylinder system arranged in an intermediate-spacing setting in static and rotating conditions are investigated. The complex flows generated are relevant to fundamental fluid flow phenomena and engineering applications and merit investigation. In this study, experiments using hot-wire and two-dimensional (2D) Particle Image Velocimetry (PIV) are conducted in order to characterize the fluid flow at various Reynolds numbers and rotational speeds. The three-cylinder system setup is in equidistant triangular arrangement, each cylinder having diameter of 3.1 mm with a 9.7 mm circumscribed-circle diameter among them. To elucidate the cylinder system flow phenomena occurring during static and rotating conditions, the PIV measurement campaign was conducted in two stages. Firstly, a very close view of the flow was used to capture wake interaction between three cylinders in detail at a representative case of low Reynolds number, Re = 57, at three static orientations. Secondly, the experiment was conducted using a larger field of view to capture far field flow characteristics at increased Reynolds numbers, Re = 310 and 1250, for three static orientations and various rotating conditions. For static cases, the results show some flow phenomena that has been reported in several computational studies before, but new experimental evidence of early mixing and breakdown of the wake through a variety of flow patterns are revealed. With the addition of the new parameter of continuous rotation, the three-cylinder system further evolves into new scenarios, including cases with resembling single-cylinder wake patterns. Time-resolved characteristics of the flow are obtained from point-wise hot-wire anemometry and are presented as a function of cylinder system rotational speed, Re number, and non-dimensional frequency or Strouhal (St) number.

Research on Hydraulic Servo Valve Control Based on Fuzzy RBF

Aiming at the problems of low control precision and slow response speed of traditional control of actuators in hydraulic systems, the mathematical model of the valve-controlled cylinder is established as the research object, and the control strategy of fuzzy RBF neural network is proposed to control hydraulic servo valves On the basis of traditional fuzzy control, fuzzy control and RBF neural network control are integrated. According to the mathematical model of the system, a tracking controller is designed to realize precise control and real-time feedback of the valve-controlled cylinder system. The simulation results show that compared with traditional PID and fuzzy PID systems, the fuzzy RBF neural network strategy has high control precision, fast response speed, better robustness, and stability.

VIBRATION AND STRAIN SIGNAL ACQUISITION FOR NUMERICAL SIMULATION OF A COFFEE HARVESTER

Coffee harvesters utilize vibration systems to dislodge coffee beans. The vibration system is usually coupled to the end of an axis (rod cylinder). This cylinder can fail in the field, which usually occurs by means of cracks close to its flange in the region that promotes vibration. Numerical simulations are typically used to predict strains and stresses based on vibration signals in machines in general. This work acquired the vibration and strain signals of a coffee harvester rod cylinder prototype and compared the results using finite element analysis. To this end, a rod cylinder system was prototyped on a reduced scale (1:3) to recreate frequency and strain data, which were used for numerical simulation comparisons. The results showed that the predicted von Mises stress in the analyzed zone was 16.47 MPa (below the material yield strength, 250 MPa) based on a frequency of 14.2 Hz applied to the rod cylinder. This confirmed that cracks found in rod cylinders in the field are not generated by high stresses, as reported in the literature. The results demonstrated the potential of finite element analysis for strain and stress prediction when applied to agricultural machine components.

Application of Hardware-in-the-Loop Simulation Technology in the Development of Electro-Hydraulic Servo System Control Algorithms

In this paper, we present a method to identify paramaters for controlling electro-hydraulic servo systems in a real-time environment. With the aim of addressing the problem that it is difficult to accurately obtain the state space equation parameters of the physical entity of the electro-hydraulic servo system, we introduce an online identification theory (recursive least squares method) for identifying said parameters of the state space model in a valve-controlled symmetrical cylinder system. After accurately obtaining the parameters of the system, nonlinear control of the valve-controlled symmetrical cylinder system is carried out using a backstepping algorithm. In order to verify the actual effect of the online identification algorithm and backstepping algorithm, a hardware-in-the-loop (HIL) simulation platform for the valve-controlled symmetrical cylinder system is built in a Linux real-time system, and the real-time performance of the system is evaluated, which demonstrates that the platform can be reliably applied for subsequent system identification and backstepping verification. The results of the HIL simulation test demonstrate that the online identification algorithm and backstepping control method developed in this paper are effective and reliable.

The Tribo-Dynamics Performance of the Lubricated Piston Skirt–Cylinder System Considering the Cylinder Liner Vibration

The tribo-dynamics performance of the piston–cylinder system is affected by multiple physical fields. The current work presents a novel multiphysics coupling method to model and analyze the lubricated piston skirt–cylinder interface considering the cylinder liner vibration. This method is implemented by coupling multibody dynamics of the crank-connecting rod–piston–cylinder system, the heat transfer of the cylinder and piston, hydrodynamics lubrication on the skirt–cylinder interface, vibration of the cylinder liner, and thermal as well as elastic deformation in the piston–cylinder system together with rheological characteristics of lubricating oil. The proposed method is adopted into a four-stroke gasoline engine to predict its dynamics and tribological characteristics, with the purpose of revealing the influence of cylinder liner vibration on the tribo-dynamics implementation of the piston–cylinder system. The results indicate that increasing the stiffness and damping coefficient of the cylinder is beneficial to suppress the vibration of the system, but it has little effect on the tribological characteristics of the piston skirt–cylinder interface.

PO16: Commissioning of the Varian Universal Interstitial Cylinder (UIC) System for HDR Brachytherapy of Cervical Cancer

<h3>Purpose</h3> Varian Medical Systems (VMS) has recently released the Universal Interstitial Cylinder (UIC) for use with Ir-192 HDR brachytherapy. We commissioned one cylinder with a plastic Universal Cervix Probe (UPC) and plastic interstitial needles using CT and MR images. A phantom specifically designed to avoid the introduction of water or water-like materials into the needle guide tracks was used and various marker strands were investigated to accurately reconstruct source positions. <h3>Materials and Methods</h3> CT and MR scan were taken for the UIC set: one cylinder (30 mm diameter) with plastic UCP (80 mm, 30 degrees) and eight interstitial needles (channel #2-#9). To compare three different methods for channel identification, CT images (Siemens Biograph mCT, Siemens AG) with slice thickness of 0.6 mm were taken with either no radio opaque markers, VMS-numbered markers, or nylon coated stainless steel leader wires ("fish wire") which aid in channel identification and image registration. The MR images were taken on a 3T Magnetom Skyra Siemens MRI scanner using 3D T1 and 2D T2 weighted clinical HDR gynecological MRI protocols. An HDR MRI Lumen Marker (C4 Imaging, LLC) was placed in the channel #9 to check for any applicator rotation. The needle guide track openings at the distal end of the UIC cylinder causes liquid to be introduced into the tracks which results in unintended MR and CT signal. A gynecological phantom was constructed by placing the applicator set into three different phantom materials: wet towels, gelatin, or ground beef. Image quality of the CT and MRI scans for these phantoms were compared for treatment planning. The applicator dimensions were verified on CT and kV planar images. Dimensions from the vendor solid applicator models, which are based on the computer-aided design model files of the specific applicator were compared to those on CT and kV images. <h3>Results</h3> The phantoms made of wet towels or gelatin allowed significant amounts of liquid to enter the needle guide tracks from the holes in the distal end of the cylinder. This can mislead as to the actual source positions in the applicator. Specifically, it resulted in channels with unintended MR and CT signal (Figure 1a). The ground beef phantom was developed to limit this introduction of liquid into the cylinder (Figure 1b). CT scans with no markers displayed substantially wider needle guide tracks than the plastic needles (Figure 1b). CT scans with VMS-markers showed significant artifact (Figure 1c). CT scans with fish wire provided the best visibility of the needles within the needle guide tracks (Figure 1d). This scan along with the solid applicator model was also used to confirm distance from the outer wall to the inside of the needle guide track (8 mm) and to the center of the needle (7 mm) and the 30 mm diameter of the cylinder (Figure 1d). The use of an MR marker allowed that needle (channel #9) to be identified in the T1w MR scan (Figure 1b). The dimensions of the applicators could be validated on CT (Figure 1d) and kV planar images (Figure 1e). <h3>Conclusions</h3> The UIC applicator was commissioned for CT and MR image based treatment planning for HDR brachytherapy. Planar kV images verified dimensions of applicator against vendor specs. Accurate source position reconstruction was feasible using CT scan with 0.6 mm slice thickness and radio-opaque markers. The use of a ground beef phantom rather than a liquid based phantom minimized unintended MR and CT signal by limiting introduction of fluid into the needle guide tracks.

Analysis of Dynamic Characteristics of Hydraulic Driven System for Weight Bearing Lower Limb Exoskeleton

A new kind of weight-bearing lower limb exoskeleton driven by hydraulic cylinder is designed, and its structural characteristics and driving principle are analysed. The mathematical model and control block diagram of the valve controlled unsymmetrical cylinder system for the controlled rotary joint are established. The effects of structural parameters such as servo valve bandwidth, load mass and hydraulic cylinder size on the dynamic characteristics of the system are studied, and the force tracking curve optimized by structural parameters is given to prove the correctness of the theoretical analysis of the system, which provides theoretical support for the design of the weight-bearing lower limb exoskeleton.

Design and performance evaluation of a magnetorheological valve with mosquito-coil-plate fluid flow channels

This work proposed and fabricated a magnetorheological (MR) valve with mosquito-coil-plate fluid flow channels. By setting non-magnetic mosquito-coil-plate arc baffles in the radial fluid flow channels of the conventional radial MR valve, MR fluid was forced to flow circumferentially in the mosquito-coil-plate fluid flow channels surrounded by arc baffles. Thus, the effective fluid flow channels of the proposed MR valve were significantly lengthened in the case of fixed volume, and the radial resistance gaps could be easily adjusted by replacing valve cores with different thicknesses. In order to investigate the distributions of the magnetic flux lines and the changes of the magnetic flux density of the MR valve accurately, the 2D and 3D finite element models of the designed MR valve were established by using ANSYS software. Moreover, pressure drop and response time of the MR valve were experimentally evaluated, and the experimental results show that the designed MR valve can not only output larger pressure drop, but also achieve rapid response time. In addition, the proposed MR valve was used as control unit in a valve controlled cylinder system, and its damping performances were tested separately under different applied currents and harmonic excitations with different amplitudes and frequencies. The test results indicate that the proposed MR valve controlled cylinder system can output reliable damping forces in a variety of operating modes. • A new MR valve with mosquito-coil-plate fluid flow channels was designed. • The pressure drop performance was evaluated through theoretical analysis and experimental verification. • A MR valve controlled cylinder system was established, and its damping performance was investigated. • This proposed MR valve has significantly improved its performance by introducing mosquito-coil-plate fluid flow channels.

Thermal conditioning of remoistened wheat straw to produce durable pellets

Agricultural biomass like wheat straw is known to be lacking natural binders to form durable pellets. Our previous research had shown that steam explosion of wood improved the durability of pellets. However, treated wood required drying prior to pelletization. Thermal conditioning is practiced in the animal feed industry to modify the ingredients of animal feed to produce high quality pellets. We hypothesized that thermal treatment of straw would result in biomass pellets with improved durability when compared to pellets made from untreated biomass. To test this hypothesis, the moisture content (mc) of the straw samples was adjusted to 5%, 10%, and 15% (wet basis). The moistened samples were subjected to dry heat in a sealed reactor set at 80, 100, and 120 °C for 5, 10, and 15 min. The treated straw samples were pelletized by using a single piston cylinder system. The highest durability 91.5% belonged to the treatment of 10% mc straw at 100 °C for 5 min. A response surface method confirmed that the initial mc 10%, treatment temperature 100 °C, and treatment time 5 min, produced the most durable pellets with the lowest unit energy input in forming pellets.