Digital Hydraulic Cylinder Research Articles

SISTEM DE ACȚIONARE EFICIENT ENERGETIC CU CILINDRU HIDRAULIC DIGITAL PENTRU MAȘINI DE CONSTRUCȚII ȘI AGRICOLE

Given the need to reduce greenhouse gas emissions, new energy-efficient solutions can be adopted for construction and agricultural machinery. Such a solution is a digital hydraulic cylinder that uses several active areas and a constant pressure supply with which a gradual variation of the driving force can be obtained. Traditional hydraulic systems have high energy losses due to the need to direct and throttle the flow through different valves. The article presents simulations in the AMESim environment and laboratory experiments of a digital hydraulic cylinder with three active areas. Through numerical simulations, the authors aim to highlight the energy efficiency of a digital hydraulic cylinder compared to a hydraulic cylinder in a conventional drive.

Synchronization Control of Two Digital Hydraulic Cylinders Based on Cross-coupling

According to the problem that the displacement of a traditional digital hydraulic cylinder cannot be adjusted in real-time, a synchronous control algorithm for a double digital hydraulic cylinder is proposed based on the cross-coupling control strategy. AMESim simulation of the dual-cylinder synchronization control system shows that the control algorithm not only makes the digital hydraulic cylinder track the input signal accurately, but also improves robustness and synchronization performance.

A New Elastic Non Contacting Sealing Concept for Valves

The hydraulic binary counter concept was proposed as a means to realize compact and lightweight digital hydraulic cylinder drives for exoskeleton actuation. This counter principle is based on hydraulically actuated switching valves which have a hysteretic response with respect to the pilot pressure. Manufacturing tolerances of the tiny components caused unexpected high leakage which, in turn, led to a malfunction of the system.
 In this paper a new sealing concept, is introduced to solve this problem. It is based on a non-contact seal (sealing gap), which exploits a self-regulating, elasto-hydrodynamic effect to reduce a rather large initial gap h0 – to allow a rough tolerance – into a very small sealing gap h(x) to avoid dry friction of valve spool movement on the one hand but have very small leakage on the other hand.
 As sealing, an annular flexible ring made, e.g. of PTFE, is used which combines sufficient flexibility to allow this self adapting mechanism to a sufficient extent and to stay the high pressure loads.
 For the mathematical analysis of the concept, an approximate elasto-hydrodynamic analytical model is used. It sets the gap pressure, obtained from the Reynold’s equation for the sealing gap, the elastic restoring forces of the sealing ring, and the imparting pressure in equilibrium.
 The sealing concept is then simulated with a numerical model built with the finite element code ABAQUS, this results are compared with the one of the analytical model.
 It solves the Reynolds equation by a user defined subroutine. The simulation results indicate that this sealing principle delivers way better results than standard gap seals despite its rough manufacturing tolerances with one order of magnitude higher tolerance ranges. The application of this concept is not limited to small valves as needed for exoskeleton hydraulics but can be transferred to conventional type of hydraulics as well.

Research on Adaptive Friction Compensation of Digital Hydraulic Cylinder Based on LuGre Friction Model

This paper aims to eliminate nonlinear friction from the performance of the digital hydraulic cylinder to enable it to have good adaptive ability. First, a mathematical model of a digital hydraulic cylinder based on the LuGre friction model was established, and then a dual‐observer structure was designed to estimate the unobservable state variables in the friction model. The Lyapunov method is used to prove the global asymptotic stability of the closed‐loop system using the adaptive friction compensation method. Finally, Simulink is used to simulate the system performance. The simulation results indicate that the addition of adaptive friction compensation control can effectively reduce system static error, suppress system limit loop oscillation, “position decapitation,” “speed dead zone,” and low‐speed creep phenomena, and improve the overall performance of the digital hydraulic cylinder. The control method has practical application value for improving the performance index of the digital hydraulic cylinder.

Mechanism Modeling and Simulink Simulation Analysis of Digital Hydraulic Cylinder

Based on the structure of the digital hydraulic cylinder and the principle of closed-loop control, the mechanism models of the stepper motor and the spool mechanism, the three-way spool valve, and the hydraulic cylinder are established respectively, and the overall mathematical model of the digital hydraulic cylinder is synthesized, and its Simulink simulation model is constructed. The stability and positioning accuracy of the system are analyzed. The results show that the error of this type of digital hydraulic cylinder is 0.0142mm for 1mm action and 0.0182mm for 2mm action. At the same time, it is found that the fluctuation of oil supply pressure will cause system jitter and reducing the frequency of stepper motor can improve the positioning accuracy of the cylinder.

Co-simulation analysis of the single stage screw feedback digital hydraulic cylinder

Taking the single-stage spiral feedback digital hydraulic cylinder as the research object, on the basis of analyzing its composition and mechanical feedback mechanism, we explored the idea of collaborative simulation based on AMESim and Simulink software, and finally realized the collaborative simulation of digital hydraulic cylinder. In this simulation, we use AMESim software to build the mechanical and hydraulic models, Simulink software to build the step-in motor model, and integrate the hydraulic model into the Simulink platform environment through the software interface. We can easily change the parameters to analyze its performance, and provide a convenient way for digital hydraulic cylinder performance optimization research.

Analyzing of influencing factors on dynamic response characteristics of double closed-loop control digital hydraulic cylinder

Analyzing of influencing factors on dynamic response characteristics of double closed-loop control digital hydraulic cylinder

Hydraulic actuation of exoskeletons - state of the art and prospects

Exoskeleton technology appreciates rising sales and rumors are circulating about more use of hydraulic actuation in future This paper gives general requirements on exoskeleton actuation technologies and concludes that only new hydraulic principles have a chance to fulfill the extremely challenging requirements The digital hydraulic cylinder and its control by a hydraulic binary counter are briefly presented as one promising principle

A mathematical analysis of a hydraulic binary counter for hydraulic exoskeleton actuation

Low weight and compactness are the main requirements on components for exoskeletons. For drives this means also high efficiency to keep energy storage and power transducing devices small. The digital hydraulic cylinder drive is an excellent candidate to become a superior technology for exoskeleton actuation. It requires several valves to control pressure in its many chambers. Solenoid valves suffer from the high weight and space of the solenoids. In this paper, the hydraulic binary counter in a configuration with only passive elements is studied mathematically, since it can control a digital cylinder with much smaller space and weight than magnetically actuated valves. From qualitative considerations of the system equations supplemented by a numerical study, it is shown that such a counter works properly. But it poses requirements on the control pressure range which are difficult to fulfil for digital cylinder drives with more than five chambers.

Design and Analysis of Hydraulic Chassis with Obstacle Avoidance Function

This article mainly expounds the design of hydraulic system for the hydraulic chassis with obstacle avoidance function. Including the selection of hydraulic motor wheels, hydraulic pump, digital hydraulic cylinder and the matching of engine power. And briefly introduces the principle of obstacle avoidance.

Research on the Digital Hydraulic Cylinder Nonlinear Robust Controlling Methods with Input Saturation

First, the nonlinear model of the digital hydraulic cylinder and the controller are constructed, then the nonlinear problem is translated into the solving of a linear matrix inequality. Finally the anti-windup compensator is designed. Simulation results show that the proposed controller and compensator guarantee the robustness and good dynamic behavior of the system.

Control-oriented modelling and development of a model-based switching algorithm for a digital hydraulic independent metering cylinder drive

The article concerns the modelling and control of a digital hydraulic cylinder drive involving a standard differential cylinder controlled by four digital flow control units in a full bridge circuit. A special focus of the modelling lies in the compromise between the prediction accuracy of the model and the computational efficiency of the control algorithms based on the models. A physically motivated model for the static pressure-flow-characteristic of digital flow control units is derived and compared to conventional models. Based on this model, a switching algorithm is developed which finds an optimal switching combination for each DFCU, if certain dimensioning conditions are fulfilled. The algorithm forms the inner loop of a hierarchical controller for the overall system. In an outer loop, a flatness-based tracking controller is used for the independent metering control of the cylinder. The models and algorithms developed in this article are validated in experimental investigations using a laboratory test rig.

Nonlinear Position Control of Digital Hydraulic Cylinder Despite Disturbance

A nonlinear controller is presented for a digital hydraulic cylinder against disturbance. We first establish the nonlinear model of digital hydraulic cylinder position control system. Then a Lyapunov function and a nonlinear controller are presented. The controller designing problem is translated into the problem of solving a linear matrix inequality. The experiment results show that the controller proposed by this paper has much better performance than traditional one.

Hopf Bifurcation Analysis of Digital Hydraulic Cylinder

A dimensionless nonlinear state-space model was established considering the structural particularities of digital hydraulic cylinder, and dynamic bifurcation characteristics of the system were analyzed and validated based on MATCONT. The results show that, when the piston diameter, valve orifice area gradient, ball-screw pitch and the maximum desired speed are not designed appropriately, digital hydraulic cylinder is prone to Hopf bifurcation. Limit cycles that the stable and the unstable neutralize each other at subcritical Hopf bifurcation points, causing the system tracking outputs divergence from continuous oscillation to increasing oscillation. Losing synchronism of stepper motor is essentially a form of the instability caused by system supercritical Hopf bifurcation.

The Simulation Analysis of Control Performance on Closed-Loop Control the Digital Hydraulic Cylinder

The working principle and design features of close-loop control digital stepping hydraulic cylinder were described, the ways to improve precision were analyzed. Base on the detailed analysis to response state of PID control, technology of fuzzy control and table the arithmetic of fuzzy-PID control was applied, which preferably satisfied control request.

Dynamic Characteristics Simulation of the Digital Hydraulic Cylinder Based on AMESim

Hydraulic transmission has a wide range of applications and attains rapid development. As the traditional methods of mathematic modeling in the design of the electro-hydraulic control system are very complex, making the design and debugging cycle of the hydraulic system longer. Thus in this paper, using the AMESim which is a senior modeling software facing engineering task design, does the modeling and simulation calculations for one kind of digital hydraulic cylinder. We get its simulation in the application of the actual working condition. At the same time, we optimize the simulation parameters and analyze the simulation results. The simulation results and analysis can provide certain reference value for the design, debugging and subsequent improvement of the digital hydraulic cylinder. According to the simulation results, it can meet different operational requirements by making appropriate compensation and adjustment in practical applications.