Showing papers on "Hydraulic machinery published in 2015"

Adaptive Control of Hydraulic Actuators With LuGre Model-Based Friction Compensation

Abstract: This paper concerns high-accuracy tracking control for hydraulic actuators with nonlinear friction compensation Typically, LuGre model-based friction compensation has been widely employed in sundry industrial servomechanisms However, due to the piecewise continuous property, it is difficult to be integrated with backstepping design, which needs the time derivation of the employed friction model Hence, nonlinear model-based hydraulic control rarely sets foot in friction compensation with nondifferentiable friction models, such as LuGre model, Stribeck effects, although they can give excellent friction description and prediction In this paper, a novel continuously differentiable nonlinear friction model is first derived by modifying the traditional piecewise continuous LuGre model, then an adaptive backstepping controller is proposed for precise tracking control of hydraulic systems to handle parametric uncertainties along with nonlinear friction compensation In the formulated nonlinear hydraulic system model, friction parameters, servovalve null shift, and orifice-type internal leakage are all uniformly considered in the proposed controller The controller theoretically guarantees asymptotic tracking performance in the presence of parametric uncertainties, and the robustness against unconsidered dynamics, as well as external disturbances, is also ensured via Lyapunov analysis The effectiveness of the proposed controller is demonstrated via comparative experimental results

Condition monitoring of a complex hydraulic system using multivariate statistics

Abstract: In this paper, a systematic approach for the automated training of condition monitoring systems for complex hydraulic systems is developed and evaluated. We analyzed different fault scenarios using a test rig that allows simulating a reversible degradation of component's conditions. By analyzing the correlation of features extracted from raw sensor data and the known fault characteristics of experimental obtained data, the most significant features specific to a fault case can be identified. These feature values are transferred to a lower-dimensional discriminant space using linear discriminant analysis (LDA) which allows the classification of fault condition and grade of severity. We successfully implemented and tested the system for a fixed working cycle of the hydraulic system. Furthermore, the classification rate for random load cycles was enhanced by a distribution analysis of feature trends.

Engineering research in fluid power: a review

Abstract: This article reviews recent developments in fluid power engineering, particularly its market and research in China. The development and new techniques of the pump, valve, and actuator are presented in brief with a discussion of two typical modern fluid power systems, which are the switched inertance hydraulic system and the hydraulic quadruped robot. Challenges and recommendations are given in four aspects including efficiency, compactness and integration, cleanliness, and fluid power education.

Review of hydraulic transmission technologies for wave power generation

Abstract: Energy extraction and conversion from ocean waves are being increasingly regarded as a research hotspot. Many different wave energy conversion systems have been proposed to convert wave energy into electricity. The paper reviewed and analyzed the hydraulic transmission technologies used in various kinds of wave energy conversion systems, and introduced a water/oil integrated transmission system used in wave energy converter to reduce the pollution caused by hydraulic oil leakage. This paper also proposed a digital hydraulic cylinder group, which could regulate the pressure of hydraulic power take-off system and reduce the energy interference in multiple devices deployed in arrays. The wave power generation applications will develop rapidly due to the fading fossil energy resources and serious environmental pollution, while the hydraulic transmission technologies with water/oil integrated transmission and digital hydraulic cylinder group will be of crucial importance to the process of the development.

Energy Efficiency Comparison between Hydraulic Hybrid and Hybrid Electric Vehicles

Abstract: Conventional vehicles tend to consume considerable amounts of fuel, which generates exhaust gases and environmental pollution during intermittent driving cycles. Therefore, prospective vehicle designs favor improved exhaust emissions and energy consumption without compromising vehicle performance. Although pure electric vehicles feature high performance and low pollution characteristics, their limitations are their short driving range and high battery costs. Hybrid electric vehicles (HEVs) are comparatively environmentally friendly and energy efficient, but cost substantially more compared with conventional vehicles. Hydraulic hybrid vehicles (HHVs) are mainly operated using engines, or using alternate combinations of engine and hydraulic power sources while vehicles accelerate. When the hydraulic system accumulator is depleted, the conventional engine reengages; concurrently, brake-regenerated power is recycled and reused by employing hydraulic motor–pump modules in circulation patterns to conserve fuel and recycle brake energy. This study adopted MATLAB Simulink to construct complete HHV and HEV models for backward simulations. New European Driving Cycles were used to determine the changes in fuel economy. The output of power components and the state-of-charge of energy could be retrieved. Varying power component models, energy storage component models, and series or parallel configurations were combined into seven different vehicle configurations: the conventional manual transmission vehicle, series hybrid electric vehicle, series hydraulic hybrid vehicle, parallel hybrid electric vehicle, parallel hydraulic hybrid vehicle, purely electric vehicle, and hydraulic-electric hybrid vehicle. The simulation results show that fuel consumption was 21.80% lower in the series hydraulic hybrid vehicle compared to the series hybrid electric vehicle; additionally, fuel consumption was 3.80% lower in the parallel hybrid electric vehicle compared to the parallel hydraulic hybrid vehicle. Furthermore, the hydraulic–electric hybrid vehicles consumed 11.4% less electricity than the purely electric vehicle did. The simulations indicated that hydraulic-electric hybrid vehicle could provide the best energy cost among all the configurations studied.

Energy-saving in excavators with application of independent metering valve †

Abstract: We applied an independent metering valve to excavator hydraulic systems in order to verify its effect on energy reduction in excavators through flow regeneration. The structure and modes of independent metering valve were introduced. Then, an excavator hydraulic system was modeled with independent metering valve configuration. Simulations compared power consumption of pump between excavator hydraulic systems with a conventional main control valve (MCV) and independent metering valve configuration (IMV). Through this comparative study, the IMV’s effectiveness on energy saving in the excavator system was analyzed.

Piecewise Affine System Identification of a Hydraulic Wind Power Transfer System

Abstract: Hydraulic wind power transfer systems exhibit a highly nonlinear dynamic influenced by system actuator hysteresis and disturbances from wind speed and load torque. This paper presents a system identification approach to approximate such a nonlinear dynamic. Piecewise affine (PWA) models are obtained utilizing the averaged nonlinear models of hysteresis in a confined space. State-space representation of PWA models is obtained over the allocated operating point clusters. The experimental results demonstrate a close agreement with that of the simulated. The experimental results and simulation show more than 91% match.

Experimental investigation of a switched inertance hydraulic system with a high-speed rotary valve

Abstract: This paper reports on experimental investigations of a switched inertance hydraulic system (SIHS), which is designed to control the flow and pressure of a hydraulic supply. The switched system basically consists of a switching element, an inductance (inertance), and a capacitance. Two basic modes, a flow booster and a pressure booster, can be configured in a three-port SIHS. It is capable of boosting the pressure or flow with a corresponding drop in flow or pressure, respectively. This technique makes use of the inherent reactive behavior of hydraulic components. A high-speed rotary valve is used to provide sufficiently high switching frequency and to minimize the pressure and flow loss at the valve orifice, and a small diameter tube is used to provide an inductive effect. In this paper, a flow booster is introduced as the switched system for investigation. The measured steady-state and dynamic characteristics of the rotary valve are presented, and the dynamics characteristics of the flow booster are investigated in terms of pressure loss, flow loss, and system efficiency. The speed of sound is measured by analysis of the measured dynamic pressures in the inertance tube. A detailed analytical model of an SIHS is applied to analyze the experimental results. Experimental results on a flow booster rig show a very promising performance for the SIHS.

Counterbalancing Speed Control for Hydrostatic Drive Heavy Vehicle Under Long Down-Slope

Abstract: This paper deals with the counterbalancing speed control issue of the closed hydrostatic drive hydraulic system of the heavy transportation vehicle under long down-slope. First, a novel method to realize the balancing to the down-slope weight force and the regulation to the motor speed is proposed. Next, a global fast terminal sliding mode control method is introduced to the speed control system. Then, addressing the load torque disturbance, a disturbance observer is designed for rejecting to disturbance. Finally, a test rig is established for verifying the effectiveness of the control method. The simulation and experimental results show that the designed continued hydraulic counterbalancing speed control system can smoothly regulate the traveling speed and restrain the load disturbance.

High dynamic feedback linearization control of hydraulic actuators with backstepping

Abstract: This article concerns the high dynamic tracking control of hydraulic servo systems. Unlike previous works usually dealing with high-accuracy tracking control, the proposed feedback linearization co...

Speed-variable Switched Differential Pump System for Direct Operation of Hydraulic Cylinders

Abstract: Efforts to overcome the inherent loss of energy due to throttling in valve driven hydraulic systems are many, and various approaches have been proposed by research communities as well as the industry. Recently, a so-called speed-variable differential pump was proposed for direct drive of hydraulic differential cylinders. The main idea was here to utilize an electric rotary drive, with the shaft interconnected to two antiparallel fixed displacement gear pumps, to actuate a differential cylinder. With the design carried out such that the area ratio of the cylinder matches the displacement ratio of the two gear pumps, the throttling losses are confined to cross port leakage in the cylinder and leakage of the pumps. However, it turns out that the volumetric pump losses and the pressure dynamics of the cylinder and connecting pipes may cause pressure increase- or decrease in the cylinder chambers, which may seriously influence the dynamics and hence the performance during operation. This paper presents an analysis of these properties, and a redesign of the hydraulic system concept is proposed. Here the area- and displacement ratios are deliberately mismatched, causing inherent pressure build-up or cavitation in the return chamber, depending on the direction of motion. In order to avoid cavitation, a third gear pump is introduced, which provides a flow in the relevant cylinder chamber in one direction of motion, while operating in idle mode in the opposite motion direction. Together with two 2/2 way proportional valves, this design allows to control the lower chamber pressure levels, throttling excess compression flow to tank. The resulting design introduces additional losses due to throttling of excess compression flow, but also improves the dynamic properties of the system significantly. The proposed features are verified by comparison with the original pump concept and a conventional valve concept. Furthermore, significant improvement in energy efficiency is demonstrated under certain load conditions.Copyright © 2015 by ASME

A study on the optimum design for the valve plate of a swash plate-type oil hydraulic piston pump

Abstract: Numerous studies have been conducted on hydraulic systems operating under high pressure. However, such systems are difficult to realize because of mechanical limitations as a result of tribological problems between relative sliding parts. Design techniques, manufacturing techniques, and tribological characteristics must be improved or innovated to operate such systems under increased pressure. The stress distributions and optimum design factors needed to satisfy these requirements under maximum pressure are determined by analyzing the stress on the valve plate of a hydraulic axial piston pump. This pump is among the most important relative sliding parts. As per the result of the analysis conducted using an orthogonal array, the extent of the influence of the design factors on maximum stress value is ordered as follows: [z > M > h > r]. Moreover, the maximum stress value of the optimum model is 13.3% lower than that of the standard model. Results also show that the stress characteristic of the optimum model is more stable than that of the standard model.

Simulation of an Excavator Hydraulic System Using Nonlinear Mathematical Models

Abstract: This paper describes a mathematical modelling methodology developed for the rapid simulation of an excavator hydraulic system. The modelling approach presented enables a reduction of the control system development time for a complete excavator, while providing accurate system dynamics. A tool for defining an appropriate control strategy is a key point for satisfying the need for systems with better energy-efficiency. Moreover, the model will be a significant support in investigating energy recovery solutions and evaluating the suitability of hybrid solutions (mechanical/hydraulic/electric). The hydraulic model, composed of the pump’s grey box model and the valve block white box model, has been validated on the basis of a set of experimental data collected on a test bench. The results of this study are presented in this paper.

Mobile Working Hydraulic System Dynamics

Abstract: This thesis deals with innovative working hydraulic systems for mobile machines. Flow control systems are studied as an alternative to load sensing. The fundamental difference is that the pump is c ...

Development of a fast torque-controlled hydraulic humanoid robot that can balance compliantly

Abstract: This paper reports on development of a fast torque-controlled hydraulic humanoid robot Tae-Mu. We present details on the hardware including the actuation, mechanical design, control and sensing systems. The robot has 13 active joints which are all driven by hydraulic servo cylinders with an external hydraulic power supply. The robot is installed with a three-axis active torso, which are utilized for static and dynamic balancing. The height is 141 cm, and the weight is 72.3 kg including a dummy weight stands for the arms. The lightweight design with carbon-fiber-reinforced plastic allowed the legs have the similar mass distribution to human legs. We present experimental results including basic torque control, balancing against external push, balanced squat motions and compliant balancing on a moving platform. The attached experimental video and graphs demonstrates that the fabricated robot has a high potential as a research platform for human sensory-motor control because of its compliance, high torque, speed, range of motion, safety and durability.

A throttle-less single-rod hydraulic cylinder positioning system: Design and experimental evaluation

Abstract: Modern industrial tote dumpers and lifters are equipped with long-stroke single-rod hydraulic cylinders. For years, valve-controlled cylinders have been used in tote dumpers. Valve-controlled actuators are highly inefficient due to huge power losses in throttling valves. They also need a cooling system to remove the wasted heat energy from the hydraulic oil. This article introduces a low-cost throttle-less hydraulic circuit to control the single-rod cylinder of a tote dumper. The system consists of a motor-driven gear pump, an On/Off solenoid valve, to redirect the differential flow of the single-rod hydraulic cylinder and a counterbalance valve, which makes the circuit controllable for assisting loads and keeps the load in position with no effort from the hydraulic pump. Experimental results demonstrate the performance of the circuit. A test rig has been designed to simulate a lifting load. The energy efficiency of the circuit is determined by comparing a valve-controlled circuit with the proposed circui...