Hydraulic Hybrid System Research Articles

Hydraulic Hybrid Cut-to-Length Forest Harvester—Evaluation of Effects on Productivity and Fuel Efficiency

A cut-to-length (CTL) forest harvester is a purpose-built, hydraulically actuated mobile work machine used for felling, delimbing, and cross-cutting trees into dimensions and assortments. In such a machine, the diesel engine load is known to fluctuate greatly over the work cycle. To manage these changing power demands, a hydraulic hybrid system is implemented into a full-scale proof-of-concept machine to discover its functionality and to collect experimental results in real operating conditions. The hydraulic hybrid system installed on a CTL harvester machine was tuned to enable the collection of two actual datasets of timber harvesting, and data collection over a period of production use was carried out. In addition to updating the state-of-the-art research into heavy non-road mobile machinery regarding hybrid systems, this paper discusses the two tests carried out in actual production conditions with the studied hydraulic hybrid system. The adaptations and modifications to the studied and tested system since earlier papers are discussed—especially the improvements in the system dynamics and response as well as the control of the hybrid system. In conclusion, the tested system can be said to operate satisfactorily and shows clear advantages over the conventional system, even though it still has some limitations. The results show that the system has the potential to increase the productivity of the machine through the demonstrated higher peak power, as well as showing improvement in fuel efficiency under highly fluctuating loads, especially with heavy or large-volume tree stems.

Research on the complete vehicle control strategy of the composite accumulator hydraulic hybrid power system

The compound accumulator is an energy storage device consisting of a large accumulator and a small accumulator. Compared with the traditional single accumulator hydraulic hybrid vehicle, it has the characteristics and advantages of fast braking response for the small accumulator and more energy recovery for the large accumulator, combining braking characteristics and energy recovery rate. This paper proposes the control strategy for parallel hydraulic hybrid vehicle based on compound accumulator, which can determine the working timing for large and small accumulators according to the specific driving conditions, thereby improving the braking performance and fuel economy for the vehicle. Under NEDC conditions, this paper uses dynamic programming algorithm to find the optimal control sequence for torque distribution and energy management of the hydraulic hybrid vehicle with composite accumulator, obtains the control rules and logic thresholds of the logic threshold control strategy, and obtains the switching rule of the working timing of the composite accumulator. The simulation of specific cycle conditions is carried out to verify the rationality of vehicle control strategy and to explore the energy-saving mechanism of parallel hydraulic hybrid power system based on composite accumulator. The NEDC urban cycle test was carried out, and the comparison between the test and simulation results showed that the hydraulic hybrid operation mode, large and small accumulator pressure, and engine fuel consumption during the test were basically consistent with the simulation results and verified the control effect of the vehicle control strategy and the energy-saving mechanism of the parallel hydraulic hybrid system based on the composite accumulator.

Review of Hydro-Pneumatic Accumulator Models for the Study of the Energy Efficiency of Hydraulic Systems

This review article deals with hydro-pneumatic accumulators (HPAs) charged with nitrogen. The focus is on HPA models used in the study of the energy efficiency of hydraulic systems. Hydraulic circuits with HPA are presented along with their various applications for delivering the required volume of fluid, maintaining the required pressure, ensuring safe operation, safety stop, leak compensation, fluid volume change compensation, pulsation damping, and pressure shock absorption. A general regenerative hydraulic system and a general hybrid hydraulic system are also presented. The review focuses primarily on HPA computational, dynamic, and simulation models. Basic HPA calculation parameters and computational models of energy storage and thermodynamic cycle are presented. Various computational and dynamic models of HPA have been defined, such as the thermodynamic model, simulation model, dynamic model, pulsation damper model, and shock pulse damper model. Research projects that have used HPA in industrial hydraulic systems are reviewed, such as those maintaining operating pressure in an industrial 80 MN open-die hydraulic forging press and acting as a shock pulse absorber in the lifting and levelling module of a tracked mobile robotic bricklaying system. The development of energy storage technology in HPA from various sources is now a global challenge.

A Comprehensive Review of Energy Regeneration and Conversion Technologies Based on Mechanical–Electric–Hydraulic Hybrid Energy Storage Systems in Vehicles

The primary purpose of this paper is to investigate energy regeneration and conversion technologies based on mechanical–electric–hydraulic hybrid energy storage systems in vehicles. There has been renewed interest in hydraulic storage systems since evidence has been presented that shows that they have the distinct advantages of high energy output and energy recuperation compared to electrical energy recovery systems, which are widely applied in electric vehicles; however, they are known to be high-cost, with a complicated structure and not zero carbon. In this paper, we first review recent research on hydraulic energy regeneration and conversion technologies. Secondly, as the main part of this paper, the latest technological progress and breakthroughs of the mechanical–electric–hydraulic hybrid energy storage systems in vehicles—which are divided into four categories: passenger, minibus and bus, commercial vehicle and special vehicle—are analyzed and discussed in depth. In addition, the current research status of energy management techniques is presented and summarized. Finally, prospects and challenges are suggested and explained. It is evident from the literature review that the mechanical–electric–hydraulic hybrid systems perform excellently in vehicles. Clearly, this review will be helpful to understand, explore and define the hydraulic vehicle of the future concerning energy optimization and environmental friendliness.

Energy management strategy for hydraulic hybrid system with compound accumulator based on dynamic programming

The compound accumulator is an energy storage device composed of one large accumulator and one small accumulator. Compared with traditional single-accumulator hydraulic hybrid vehicles, hydraulic hybrid vehicles based on compound accumulator can switch the working timing of large and small accumulators according to the characteristics of different working conditions, more braking energy can be recovered on the premise of providing enough braking strength. This article is aimed at hydraulic hybrid vehicles based on compound accumulator. First, the key components of the hydraulic system were matched, then according to the engine fuel consumption curve, the engine’s high-efficiency work area is divided, and formulated a rule-based energy management strategy based on the principle of adjusting the engine to work in a high-efficiency area. The internal pressure of the compound accumulator is selected as the state variable, the ratio of the torque of the hydraulic pump/motor to the required torque of the vehicle is the control variable, and the optimal fuel economy of the entire cycle is the objective function, and the mathematical model is established using the dynamic programming algorithm, and compiled a program in MATLAB to obtain the optimal torque distribution relationship between the engine and the hydraulic pump/motor and the optimal working timing of the large and small accumulators. Simulation results show that compared with the traditional hydraulic hybrid vehicle with single accumulator based on initial rules and the hydraulic hybrid vehicle with compound accumulator based on initial rules, the hybrid vehicle with compound accumulator based on improved rules can save fuel by 11.84[Formula: see text] and 5.96[Formula: see text] respectively. The fuel saving potential of the compound accumulator structure and the effectiveness of the improved rule control strategy based on dynamic programming algorithm are verified.

Technical Solutions of Forest Machine Hybridization

The paper deals with the characteristics of three different types of power train hybridization of forest logging machines and with the benefits of reducing environmental impacts by comparing new technology with more conventional, older technology. New hybridization options that could be implemented in forestry machines are also discussed. The paper divides a hybrid solution into three classes based on the energy used in the system of hybridization. First is an electro-hybrid system that uses an electric motor and battery or different storage device. The second, a hydraulic hybrid system, is a solution with a hydraulic accumulator, hydraulic motor, and pump. The third system is a combination of the electro-hybrid and hydraulic-hybrid system. The current technical and technological development of hybrid drive systems, as well as their components, has led to significant improvements in drive performance and thus better performance of the new generation of forest vehicles. Improved energy efficiency using hybrid propulsion systems in forest vehicles would result in a significant reduction in greenhouse gas emissions and possibly lower maintenance costs.

Research on Energy Reclaiming Active Suspension Control Strategy Based on Linear Motor and Hydraulic Hybrid System

Based on linear motor and hydraulic hybrid energy reclaiming suspension, control strategy for multi-mode switched active suspension is designed. By establishing a quarter vehicle suspension system model, a fuzzy sliding mode controller is designed to control the active suspension system, and design active suspension mode switching strategy to select and switch suspension modes of vehicles under different conditions, it improves the performance of active suspension as well as the feed-ability of the suspension. The accuracy of the model and control strategy is verified by simulation, at the same time, a quarter suspension bench is built for test. The test results show the effectiveness of the simulation. The energy-feed test shows that the energy-feed efficiency of the designed energy reclaiming suspension can reach 17.54%.

Experimental and theoretical studies on energy characteristics of hydraulic hybrids for thermal management

The development of fuel-efficient vehicles has increased along with the needs of consumers and the rise of environmental issues. Hybrid vehicles have become a popular alternative to conventional powertrains in the passenger vehicle market. Hydraulic hybrid vehicles have been applied to certain applications with clear benefits, such as high power density. To increase the base of academic knowledge, the energy characteristics of hydraulic hybrids were experimentally and theoretically studied for thermal management. First, measurement data for a series hydraulic hybrid system were collected by hardware in the loop test rig for different temperature conditions. The experimental results were compared for different thermal management conditions, thus showing the power consumption behaviors at different system temperatures. Also, a theoretical approach with thermodynamic properties was introduced for analyzing the energy characteristics of hydraulic hybrid systems. The theoretical results revealed possible explanations for the relationship between energy saving and thermal management for hydraulic hybrid systems. This study was worthy not only in that the experimental data itself worth as reference data for energy characteristics of hydraulic hybrid systems for thermal management, but also in that a novel theoretical approach for energy characteristics analysis was introduced, using energy and exergy analysis for the first time.

Study and optimization of a parallel hydraulic hybrid system for heavy vehicles

The parallel hydraulic hybridization, thanks to its simplicity and high specific power, is a suitable solution for the retrofitting of off-highway vehicles subject to work cycles with frequent stop-and-go. This work is focused on the potential of the low-cost parallel hybrid solutions, i.e. characterized by current-technology components, for a specific class of heavy vehicles: city buses. After functional sizing, the hybrid vehicle was modelled and simulated in the Amesim environment. The comparison with the non-hybridized reference vehicle highlighted an interesting consumption reduction, which in any case varies with the type of route. Finally, an optimization of the hybrid vehicle was carried out by means of genetic algorithms, which led to a further, and not negligible, consumption reduction compared to the hybridized version. Optimization, therefore, can be seen as a tool to overcome those minimum benefit thresholds that manufacturers consider as necessary for the industrialization and marketing of new energy recovery systems.

Design and energy utilization of electro-hydrostatic hydraulic hybrid system for battery bus

In order to solve the problems of large peak torque and short battery life when the city battery bus starts or accelerates, a new electro-hydrostatic hydraulic hybrid powertrain is designed in this paper that can operate efficiently in all speed conditions with a certain type of electric bus running in Chengdu. The improvement of comprehensive energy efficiency of power system by switching between different power modes under typical operating conditions is studied. Through the co-simulation of AMESim and MATLAB/Simulink-stateflow software, the vehicle and control models are established and the rule-based dynamic optimal energy management strategy is set. The dynamic performance and energy utilization characteristics of New European Driving Cycle and the cycle condition of investigation under actual driving environments are analyzed. The core problems of energy coupling of electro-hydrostatic hydraulic hybrid powertrain are studied experimentally to verify the correctness of the design thought and simulation model. The results show that under the premise of satisfying the dynamic performance, the designed electro-hydrostatic hydraulic hybrid system can effectively improve the overall average efficiency of operating point of the electric motor and greatly reduce the peak torque. The peak torque is reduced by 36.4% and the battery power consumed by the selected cycle is reduced by 33.98% under New European Driving Cycle conditions. Under the actual cycle conditions, the peak torque is reduced by 28.9%, and the battery power consumed by the selected cycle is reduced by 32.3%.

Robust Repetitive Learning-Based Trajectory Tracking Control for a Leg Exoskeleton Driven by Hybrid Hydraulic System

For the purpose of reducing power consumption of a leg exoskeleton for augmenting human performance, a novel hybrid hydraulic system (HHS) which includes a unidirectional servo valve and a solenoid on-off valve is excogitated, and its energy saving control is studied in this paper. Inspired by the varieties of contact force between human leg and ground during walking, the unidirectional servo valve and the solenoid on-off valve are only activated in the stance phase and the swing phase, respectively. In the stance phase, a robust repetitive learning scheme is presented by using the backstepping technique for the unidirectional servo valve, aiming to track the periodic human leg movement, and in the swing phase, an on-off control is proposed for the solenoid valve to release the pressure in the hydraulic cylinder so that the exoskeleton leg is bent by the human leg passively. The proposed control strategy is implemented in an ARM-based embedded microprocessor and the control performance is verified via experiment on the developed exoskeleton robot. The experimental results show that the power consumption of the proposed system is almost 30% less than that of systems with bidirectional hydraulic system.

Adaptive Fuzzy Sliding Mode Control Based on Pi-sigma Fuzzy Neutral Network for Hydraulic Hybrid Control System Using New Hydraulic Transformer

Control issue is the key for applying hydraulic hybrid system, especially for common pressure rail (CPR) system which has the huge potential to enhance efficiency. In the paper, the mathematical model of hydraulic cylinder speed control system using new hydraulic transformer is established. Then an adaptive fuzzy sliding mode controller based on Pi-sigma fuzzy neutral network is designed to solve the problem of parameter uncertainty and nonlinearity without establishing the precise model. Furthermore, compared to PID and conventional adaptive fuzzy system, the controller proposed can achieve good control performance and strong robustness in the presence of time-varying uncertainty.

Parameter Matching Analysis of Hydraulic Hybrid Bergepanzers Based on RBF-Adaptive Artificial Immune Algorithm

Due to the multiple types of support tasks and high-energy efficiency equipment, energy saving research in a Bergepanzer has attracted much attention in recent years. A hydraulic hybrid system is an effective way for these problems of Bergepanzers. The initial problem is to optimize the parameter optimization-matching for a new hydraulic hybrid Bergepanzers (NHHB), which is a relatively complex and variable time-varying nonlinear system. In this paper, an RBF-adaptive artificial immune algorithm (RBF&AAIA) is presented to solve the parameter optimization-matching problem, and the performance of algorithm is analyzed. Finally, the RBF&AAIA is successfully used for the NHHB to optimize the parameters of key components for the minimum energy consumption of system, and the optimal parameter matching group is obtained.

Modelling, analysis and control design of hybrid dynamical systems

Abstract This paper introduces a methodology for one of the challenges regarding cyber-physical systems, ie modelling and control design them as hybrid systems. The proposed methodology comprises modules with specific steps to accomplish the tasks. Specifically, the paper aims to utilize hybrid systems framework onto the chosen hydraulic hybrid system with complex dynamics to showcase different aspects of hybrid systems. The mathematical model was derived using hybrid automata framework and then transformed into the linear form either using Jacobi matrices or using linear approximations without Jacobi matrices. After that the system was validated and analysed and the control design utilizing piecewise linear-quadratic regulator optimal control was proposed. Furthermore, parameters of control algorithm were tuned using particle swarm optimization algorithm. The whole logic, system dynamics and constrains are implemented within MATLAB/Simulink simulation environment using s -functions. The proposed methodology can be implemented on the various types of cyber-physical systems as far as they can be described as hybrid systems.

Numerical analyses of a hydraulic hybrid powertrain system for a transit bus

A dynamic programming optimization algorithm has been applied on a transit bus model in MATLAB in order to assess the fuel economy improvement potential by implementing a hydraulic hybrid powertrain system. The numerical model parameters have been calibrated using experimental data obtained on a Belgrade?s public transport bus. This experiment also provided the representative driving cycle on which to conduct simulation analyses. Various functional parameters of a hydraulic hybrid system have been evaluated for obtaining the best possible fuel economy. Dynamic programming optimization runs have been completed for various hydraulic accumulator sizes, preload values and accumulator foam quantities. It has been shown that a fuel economy improvement of 28% can be achieved by implementing such a system.

Optimization of Energy Recovery Efficiency for Parallel Hydraulic Hybrid Power Systems Based on Dynamic Programming

In this paper, an optimization algorithm of energy recovery efficiency is proposed for parallel hydraulic hybrid systems (PHHS) using dynamic programming (DP). Global optimal solution of pump displacement and transmission ratio under the known urban drive cycles is obtained by using the DP approach, where the total amount of energy recovery is defined as the cost function, and the pump displacement and the transmission ratio of the torque coupler are defined as the deciding variables. Two major steps are involved in verifying the proposed approach. Firstly, a PHHS Simulink model is accurately obtained by repeated comparison with the bench test. Subsequently, we derive a parallel hydraulic hybrid vehicle (PHHV) from adding a hydraulic hybrid system to an electric vehicle in ADVISOR (advanced vehicle simulator). This vehicle is used to validate the effectiveness of the proposed method in energy recovery efficiency.

Research on variable pressure characteristics of step variable hydraulic hybrid system based on cartridge value group

Compared with the traditional hydraulic hybrid system, step variable hydraulic hybrid power system has the advantages of low cost, fast response and pollution resistance. However, the existing variable elements are heavy, and the control valve group has the disadvantages of insufficient through-flow capacity, large flow resistance, large leakage and reversing impact. In this study, the hydraulic components integrated by the cartridge valve group which can replace the traditional three-position four-way valve group are applied to the hydraulic hybrid power system. The AMESim simulation models of directional cartridge valve and the step variable hydraulic hybrid power system are established in this study. Through simulation analysis, it is verified that the cartridge valve integrated element can replace the traditional reversing valve to solve the defects of cumbersome components and insufficient through-flow capacity. Some important parameters of the system components are simulated and analysed. The simulation results can be used to improve the design efficiency and ensure the design quality.

Parameters and control optimisation of hybrid vehicle based on simulation model

It is generally difficult to obtain accurate optimisation functions during parameters matching and optimisation process of the hybrid system, especially in the optimisation variable field containing both a continuous set and a discontinuous set and when the control strategy has an important influence on the system performance. To aim at the fuel economy of the parallel hydraulic hybrid system, a global parameter matching and control strategy based on the simulation model were proposed. The AMESim simulation model as the judgment module of the optimisation algorithm was used to match and optimise the main parameters and control strategies in the hybrid system. The communication of underlying parameters was developed by the VBA in EXCEL platform. Parameters match was implemented on a truck crane chassis in practice. The test results indicated that the rate of fuel saving reached 15.2%, which was generally consistent with the theoretical analysis. The parameters were met the energy-saving requirements of hybrid vehicles.

Research on variable pressure characteristics of step variable hydraulic hybrid system based on cartridge value group

Research on variable pressure characteristics of step variable hydraulic hybrid system based on cartridge value group

Integrated model control of brake–wheel system using bond graph method

Brake system is an important actuator of most active safety systems equipped on vehicles. It combines with the wheel to make vehicle decelerate and finally stop it. Moreover, brake system is an electronic, mechanical, and hydraulic hybrid system; it contains some highly nonlinear characters, which is a challenge to system control. In this article, an integrated model of brake system and single-wheel system using bond graph method is developed, in which the nonlinear characters of the volumetric compliance effect of brake fluid and the resistance effect of valves are taken into consideration. The accuracy and reliability of the brake system is verified by experiment. Nonlinear sliding-mode controller as well as sliding-mode observer is proposed. The controller is used to modulate inlet and outlet valves control signals according to the vehicle states, which will lead to cancel the usage of wheel cylinder pressure sensors. The controller is analyzed by different tire–road friction coefficient conditions. The results show that the proposed integrated bond graph model is accurate, and the nonlinear sliding-mode control is reliable on valves control signal regulation.