Showing papers on "Hydraulic machinery published in 2017"

RISE-Based Adaptive Control of Hydraulic Systems With Asymptotic Tracking

Abstract: Parametric uncertainty associated with unmodeled disturbance always exist in physical hydraulic systems, and complicate the advanced nonlinear controller design. In this paper, an adaptive compensation with a robust integral of the sign of the error (RISE) feedback is developed for high precise tracking control of hydraulic motion system. To handle both payload and hydraulic unknown parameters in one controller, a chain of integrator nonlinear system model is first derived, and an adaptive RISE controller is then proposed, in which adaptive law is synthesized to handle parametric uncertainty and RISE robust term to attenuate unmodeled disturbance. The major feature of the proposed controller is that it can theoretically guarantee asymptotic tracking performance with a continuous control input, in the presence of various parametric uncertainties and unmodeled disturbances such as unconsidered dynamics as well as external disturbances via Lyapunov analysis. However, the proposed controller takes the acceleration as a system state, which usually suffers heavy noise pollution and thus cannot be utilized directly in actual control. To solve this practical issue, in this paper, a tracking differentiator is employed to extract high-quality acceleration signal and to make the proposed controller feasible execution. The effectiveness of the proposed nonlinear controller is demonstrated via comparative experimental results.

Design and Experimental Evaluation of a Fast Torque-Controlled Hydraulic Humanoid Robot

Abstract: This paper reports the design and control of a fast torque-controlled hydraulic humanoid robot, TaeMu. The robot has 15 active joints that are all driven by hydraulic servocylinders with an external hydraulic power supply. The 1377-mm tall robot has a three-axis active torso used for static and dynamic balancing. It weighs 72.3 kg including a dummy weight stand for the arms. Its lightweight design with carbon-fiber-reinforced plastic allows the legs to have a similar mass distribution to that of human legs. We present the details of the hardware design including the hydraulic actuator selection, mechanism, and control systems, as well as the passivity-based controller design for joint torque control and whole-body motion control. We present experimentally obtained results, such as speed testing, basic torque control testing, full-body compliant balancing with attitude regulation/tracking, and balanced full-squat motions. The experimentally obtained results and estimated joint specification imply the high potential of the robot to perform human-like motions if the researchers can invent proper control algorithms.

Review of boom potential energy regeneration technology for hydraulic construction machinery

Abstract: Facing severe environmental problems, to improve the efficiency of the hydraulic construction machinery is in great demand The potential energy when the boom is lowering is dissipated as heat in hydraulic system It is urgent to improve the maximum use of regeneration energy to reduce the fuel consumption This paper first analyzes the proportion of regeneration energy for each actuator and studies the special working style of the boom energy regeneration system (ERS) in a 20-t HE Then, types of the ERS are discussed The research and development of the electric ERS technology and the hydraulic ERS technology based on construction machinery are reviewed At last, the paper puts forwards the challenges and the future development of ERSs

Modeling and Experiments of a Hydraulic Electromagnetic Energy-Harvesting Shock Absorber

Abstract: Hydraulic electromagnetic energy-harvesting shock absorbers (HESAs) have been proposed recently, with the purpose to mitigate the vibration of vehicle suspensions and also recover the vibration energy traditionally dissipated by oil dampers. This paper designs an HESA prototype for heavy vehicles and creates a dynamic modeling to study its characteristics. The model shows that the HESA's output force can be decomposed into the electric damping force, friction damping force, the inertia force, and the accumulator force. Based on the modeling, the counteracting effect between the accumulator force and the inertia force is explained, and the influences of the parameters are analyzed. Simulations are conducted to investigate the effects of the high-pressure accumulator and the inertia on the regenerative voltage. Experiments are also carried out to study the characteristics of vibration damping and energy harvesting. Results show that the damping coefficient of the proposed HESA ranges from 32 to 91 kNs/m, which covers most of the damping range of 25–50 kNs/m for typical heavy-duty trucks and 15–80 kNs/m for railway freight vehicles. The average regenerative power reaches 220 W and the corresponding hydraulic efficiency reaches 30%, at a vibration input of 3 Hz frequency and 7 mm amplitude. Moreover, the influences of different hydraulic components on the hydraulic efficiency are also experimentally studied in order to guide the future design of HESAs.

Review of the Energy Saving Hydraulic System Based on Common Pressure Rail

Abstract: Recently, much effort has been directed toward reducing the energy consumption of hydraulic systems against the backdrop of energy shortages and environmental problems. This paper is focused on the development of an energy-saving hydraulic system based on common pressure rail (CPR), which has the potential benefit of being widely applicable to construction machinery. First, the principle of CPR is introduced. Then, the main components, including hydraulic transformers and storage elements, are reviewed, followed by an analysis of the development and research efforts focused on the CPR from a system perspective, which includes energy saving application and control performance investigation. Finally, the challenges and the direction of future development are discussed.

Water-Hammer Control in Pressurized-Pipe Flow Using a Branched Polymeric Penstock

Abstract: This paper investigates the redesigning of existing steel piping hydraulic systems to control severe water hammer positive and negative surges. The applied control strategy is based on addi...

Modeling and Offset-Free Model Predictive Control of a Hydraulic Mini Excavator

Abstract: During the virtual development and experimental testing of advanced construction machinery, automation approaches for automated task execution can prove very valuable In this paper, modeling and automation approaches for a hydraulic mini excavator are developed In particular, a physical model for detailed system analysis and a simplified Hammerstein model for controller tuning are developed and validated with measurement data from the mini excavator For attitude estimation of the excavator, inertial measurement units and extended Kalman filters are used in a sensor fusion framework The control concept for automation is based on a virtual driver consisting of a state machine for task coordination as well as offset-free model predictive controllers (MPCs) for decentralized and robust tracking control of all motion axes The constrained MPC optimization problems are solved in real time by means of the accelerated proximal gradient method Experimental results from the mini excavator prove the developed control approach to be valuable for virtual development and automated testing during the commissioning of hydraulic machinery Note to Practitioners —In this paper, a hydraulic mini excavator is considered for demonstrating the benefits of automation with regard to the development of advanced mobile machinery A detailed physical model and a simplified model are introduced for virtual analysis and comissioning of the excavator This allows for detailed system analysis even at an early development stage Then, a framework for automated testing of the real prototype is introduced This concept is based on attitude estimation filters, a state machine, and model predictive controllers and closely resembles the human driver in its behavior, but allows for reproducible testing results and therefore reduces commissioning efforts and development costs Particular attention is paid to the robustness of the control concept, since the coupling of the hydraulic axes and digging forces lead to disturbances that need to be compensated A simple, yet efficient and real-time capable algorithm is provided for numerical optimization Experimental results show that the developed methods can contribute to the automation of hydraulic machinery, and that the introduced framework can easily be extended in order to automate other types of machinery with simple hydraulics

Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems

Abstract: Cavitation is the transition from a liquid to a vapour phase, due to a drop in pressure to the level of the vapour tension of the fluid. Two kinds of cavitation have been reviewed here: acoustic cavitation and hydrodynamic cavitation. As acoustic cavitation in engineering systems is related to the propagation of waves through a region subjected to liquid vaporization, the available expressions of the sound speed are discussed. One of the main effects of hydrodynamic cavitation in the nozzles and orifices of hydraulic power systems is a reduction in flow permeability. Different discharge coefficient formulae are analysed in this paper: the Reynolds number and the cavitation number result to be the key fluid dynamical parameters for liquid and cavitating flows, respectively. The latest advances in the characterization of different cavitation regimes in a nozzle, as the cavitation number reduces, are presented. The physical cause of choked flows is explained, and an analogy between cavitation and supersonic aerodynamic flows is proposed. The main approaches to cavitation modelling in hydraulic power systems are also reviewed: these are divided into homogeneous-mixture and two-phase models. The homogeneous-mixture models are further subdivided into barotropic and baroclinic models. The advantages and disadvantages of an implementation of the complete Rayleigh-Plesset equation are examined.

An Energy-Saving Method by Balancing the Load of Operations for Hydraulic Press

Abstract: Large energy loss caused by mismatching between the installed power and demanded power, as well as the wasted potential energy, is a serious problem for a hydraulic press. In order to reduce the energy loss, an energy-saving method by balancing the load of operations of presses was proposed based on the analysis of energy flow characteristics of the hydraulic system. In the method, the motor pumps in the drive system are shared in different time by a unit composed of two hydraulic presses so that the energy loss caused by unloading operations can be reduced. Furthermore, these two presses are combined, and the excessive energy from one press can serve as the input energy to the other one during some operations to improve the energy efficiency of the drive system, and the potential energy can be utilized directly. Meanwhile, operation durations of these combined presses are optimized for coordination of working processes. The method was applied to two hydraulic presses in a tandem line, and the energy consumption was obtained by quantifying the characteristics of conversion components. Results indicate that for a single press, 36% of electrical energy can be saved in the investigated forming processes.

Bilateral Control Between Electric and Hydraulic Actuators Using Linearization of Hydraulic Actuators

Abstract: In this study, bilateral control between electric and hydraulic actuators is investigated. Bilateral control realizes telemanipulation of remote robots with the sense of touch. We focus on the system of local (master) robots, manipulated by operators that are driven by electric actuators, and slave robots, which work in remote places that are driven by hydraulic actuators. To obtain bilateral control in this situation, we find that combination of three key techniques is necessary. The first key is oblique coordinate control, which can decouple position and force controllers of bilateral control. The second key is linearization of hydraulic actuators as third-order systems including oil compression by using disturbance observers. In the absence of linearization, the design becomes practically impossible because of the need to apply complicated models. Since the master robots are second-order systems, and the slave robots are linearized as third-order systems, oblique coordinate control cannot be implemented. Then, the last key is the agreement of system order of electric and hydraulic actuators by using a pseudodifferentiator. Two conventional controllers and the proposed method are experimentally and analytically compared. The proposed method shows the best tracking performance and is the most stable in contact control among the three controllers.

Hydraulic fracturing equipment with non-hydraulic power

Abstract: The present disclosure is directed to a hydraulic fracturing system for fracturing a subterranean formation. In an embodiment, the system can include an electric pump fluidly connected to a well associated with the formation, and configured to pump fluid into a wellbore associated with the well at a high pressure so that the fluid passes from the wellbore into the formation and fractures the formation. The system can further include one or more ancillary units associated with the fluid pumped into the wellbore. The system can further include a first motor electrically coupled to the electric pump to operate the electric pump, and one or more second motors, each of the second motors electrically coupled to each of the ancillary units to operate the one or more ancillary units.

Head Dependence of Pump-Storage-Unit Model Applied to Generation Scheduling

Abstract: This paper presents a head-dependent model for pump storage units (PSUs) in a power system for short-term generation scheduling over one week. A hydraulic system with upper and lower reservoirs, each having their own in and out river flows, is considered. Hydraulic conditions, as well as head effects, are explicitly modeled for both generation and pumping modes of the PSUs. The problem is solved by the branch-and-cut method to obtain a near-optimal solution. Test results of an hourly generation schedule, including comparisons of pump efficiencies, hydraulic conditions, and operating costs of the PSUs for a real power system, are presented.

Design and Analysis of an Electric Hydraulic Hybrid Powertrain in Electric Vehicles

Abstract: An electric hydraulic hybrid (EH2) powertrain for urban vehicles has been introduced and evaluated in this paper. The high power density hydraulic system in parallel configuration reduces the electricity consumption and the battery discharging stress of the electric powertrain, which extends the vehicle driving range and improves the battery pack lifespan. The proposed EH2 powertrain has been integrated to a city delivery truck model and a city bus model, evaluated over six corresponding driving cycles, respectively. Based on the simulation results, the city delivery truck battery discharging stress could be reduced by 30% on average and the city bus driving range could be extended by 50% in the best scenario. A scaled down prototype has been built and the experimental results validate the benefits of the EH2 powertrain.

Digital hydraulic multi-pressure actuator – the concept, simulation study and first experimental results

Abstract: The decentralisation of hydraulic systems is a recent trend in industrial hydraulics. Speed variable drive is one concept where an actuator is driven by an integrated pump, thus removing the need for control valves or complex centralised variable displacement hydraulic units and long pipelines. The motivation for the development is the need to improve the energy efficiency and flexibility of drives. A similar solution to mobile hydraulics is not currently available. This paper studies a digital hydraulic approach, which includes a local hydraulic energy storage located together with the actuator, the means to convert efficiently energy from the storage to mechanical work and a small start-/stop-type pump unit sized according to mean power. The simulation results and first experimental results show that the approach has remarkable energy saving potential compared to traditional valve controlled systems, but further research is needed to improve the controllability.

Global Energy-Optimal Redundancy Resolution of Hydraulic Manipulators: Experimental Results for a Forestry Manipulator

Abstract: This paper addresses the energy-inefficiency problem of four-degrees-of-freedom (4-DOF) hydraulic manipulators through redundancy resolution in robotic closed-loop controlled applications. Because conventional methods typically are local and have poor performance for resolving redundancy with respect to minimum hydraulic energy consumption, global energy-optimal redundancy resolution is proposed at the valve-controlled actuator and hydraulic power system interaction level. The energy consumption of the widely popular valve-controlled load-sensing (LS) and constant-pressure (CP) systems is effectively minimised through cost functions formulated in a discrete-time dynamic programming (DP) approach with minimum state representation. A prescribed end-effector path and important actuator constraints at the position, velocity and acceleration levels are also satisfied in the solution. Extensive field experiments performed on a forestry hydraulic manipulator demonstrate the performance of the proposed solution. Approximately 15–30% greater hydraulic energy consumption was observed with the conventional methods in the LS and CP systems. These results encourage energy-optimal redundancy resolution in future robotic applications of hydraulic manipulators.