Series Hydraulic Hybrid Vehicle Research Articles

Hydraulic hybrid passenger vehicle: Fuel savings possibilities

This work proposes to model a small series hydraulic hybrid vehicle (SHHV) for the power demand of a real driving cycle. The real driving cycle was measured with a low-cost Bluetooth Scanner connected to the On-Board Diagnostic (OBD) port of the vehicle and applied to a computational model. The hydraulic power to drive the modeled SHHV was supplied by a hydraulic pump and/or by an accumulator. Optimization tools were used to size the hydraulic components. Furthermore, the optimization tools were also used to calculate the values of the control variables for activating the pump, accumulator and the hydraulic motor, in order to have the minimum fuel consumption by the vehicle’s combustion engine. The model implemented had its fuel consumption reduced by 37% in relation to the passenger car utilized for the driving cycle data acquisition.

Framework for Simulation-Based Simultaneous System Optimization for a Series Hydraulic Hybrid Vehicle

Hybridization of hydraulic drivetrains offers the potential of efficiency improvement for on- and off-road applications. To realize the advantages, a carefully designed system and corresponding control strategy are required, which are commonly obtained through a sequential design process.Addressing component selection and control parameterization simultaneously through simulation-based optimization allows for exploration of a large design space as well as design relations and trade-offs, and their evaluation in dynamic conditions which exist in real driving scenarios. In this paper, the optimization framework for a hydraulic hybrid vehicle is introduced, including the simulation model for a series hybrid architecture and component scaling considerations impacting the system’s performance.Anumber of optimization experiments for an on-road light-duty vehicle, focused on standard-drivecycle- performance, illustrate the impact of the problem formulation on the final design and thus the complexity of the design problem. The designs found demonstrate both the potential of energy storage in series hybrids, via an energy balance diagram, as well as some challenges. The framework presented here provides a base for systematic evaluation of design alternatives and problem formulation aspects.

Robustness and performance evaluations for simulation-based control and component parameter optimization for a series hydraulic hybrid vehicle

ABSTRACTSimulation-based optimization is a useful tool in the design of complex engineering products. Simulation models are used to capture numerous aspects of the design problem for the objective function. Optimization results obtained can be assessed from various perspectives. In this study, component and control optimization of a series hydraulic hybrid vehicle is used as an application, and different robustness and performance aspects are evaluated. Owing to relatively high computational loads, efficient optimization algorithms are important to provide sufficient quality of results at reasonable computational costs. To estimate problem complexity and evaluate optimization algorithm performance, the definitions for information entropy and the related performance index are extended. The insights gained from various simulation-based optimization experiments and their subsequent analysis help characterize the efficiency of the optimization problem formulation and parameterization, as well as optimization algorithm selection with respect to parallel computation capabilities for further development of the model and optimization framework.

Framework for simulation-based simultaneous system optimization for a series hydraulic hybrid vehicle

Hybridisation of hydraulic drivetrains offers the potential of efficiency improvement for on – and off-road applications. To realise the advantages, a carefully designed system and corresponding co ...

ON THE DYNAMIC BEHAVIOR OF SERIES HYDRAULIC HYBRID VEHICLE

High Stopping frequency of heavy vehicles such as refuse trucks produces a large amount of energy which is generated by driving engine during vehicle acceleration. Most of this energy is wasted in form of heat to the environment when the vehicle brakes. This wasted energy normally lost during braking is significant especially in repeated stopping vehicles. This research presents a concept for the hydraulic hybrid system design using automation studio software to build the suggested hydraulic circuit. The classical mechanical traction in traditional vehicle can be replaced by this system without lowering vehicle performance and other satisfaction criteria in addition to achieving the main target from hybridization; regenerate energy which is always lost during vehicle braking and reuse to accelerate it again. It also includes the hydro- mechanical system architecture (which is called SHHS) and its component specification after changes in traditional vehicle structure. The switching matrix for control unit also illustrated. In this paper, the dynamics model for the SHHS (Series hydraulic hybrid vehicle) is constructed by MATLAB/SIMULINK package. The vehicle performance is investigated during various modes of operation at different condition.

Different Rule-based Control Schemes for a Series Hydraulic Hybrid Vehicle

In a hybrid hydraulic vehicle, the hydraulic accumulator is used as the secondary power source in addition to the engine to propel the vehicle. Since the accumulator is a passive power source, it will be only used to compensate the difference between the power demand and the power delivery by the engine. Obviously, the main energy consumption is the engine. Hence a straightforward strategy to improve the fuel economy is to reduce the engine operating period. In contrast, because of the low energy density characteristic, the accumulator can only afford the required power in a short period. As a consequence, the hydraulic hybrid vehicle has been concluded only suitable for start-stop-and-go driving pattern. This paper present different rule-based control schemes for a 3.5- ton series hydraulic hybrid truck. The simulation results indicate that by applying suitable control scheme, the proposed series hydraulic hybrid system offers improvements of fuel economy for both urban and highway driving condition. The improvement is of 42.67% and 36.56% for urban and highway driving conditions, respectively in comparison with the corresponding conventional vehicle.

The Development of an Optimal Control Strategy for a Series Hydraulic Hybrid Vehicle

In this work, a Truck Class II series hydraulic hybrid model is established. Dynamic Programming (DP) methodology is applied to derive the optimal power-splitting factor for the hybrid system for preselected driving schedules. Implementable rules are derived by extracting the optimal trajectory features from a DP scheme. The system behaviors illustrate that the improved control strategy gives a highly effective operation region for the engine and high power density characteristics for the hydraulic components.

Energy Efficiency Comparison between Hydraulic Hybrid and Hybrid Electric Vehicles

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.

A Model Predictive Control Approach for Fuel Economy Improvement of a Series Hydraulic Hybrid Vehicle

This study applied a model predictive control (MPC) framework to solve the cruising control problem of a series hydraulic hybrid vehicle (SHHV). The controller not only regulates vehicle velocity, but also engine torque, engine speed, and accumulator pressure to their corresponding reference values. At each time step, a quadratic programming problem is solved within a predictive horizon to obtain the optimal control inputs. The objective is to minimize the output error. This approach ensures that the components operate at high efficiency thereby improving the total efficiency of the system. The proposed SHHV control system was evaluated under urban and highway driving conditions. By handling constraints and input-output interactions, the MPC-based control system ensures that the system operates safely and efficiently. The fuel economy of the proposed control scheme shows a noticeable improvement in comparison with the PID-based system, in which three Proportional-Integral-Derivative (PID) controllers are used for cruising control.

Optimal energy management of a series hybrid vehicle with combined fuel economy and low-emission objectives

A series hybrid powertrain provides ultimate freedom in controlling the engine. The flexibility enabled with hybridization creates chances for a synergistic approach, in which the hybrid supervisory control can be augmented to address both the emissions and the efficiency. In this paper, two policy optimization techniques are proposed, namely stochastic dynamic programming and neurodynamic programming, for designing power management controllers. These controllers are then compared with a baseline rule-based controller. The intention is to investigate the additional benefits possible through application of policy optimization algorithms and a systematic framework capable of representing complex system-level effects. The power management of a series hydraulic hybrid vehicle is pursued as a sequential decision-making problem under uncertainty (stochastic control). The low energy density of the hydraulic accumulator adds to the control challenge. First, stochastic dynamic programming and neurodynamic programming are applied to design a controller based on the fuel economy objective. The problem is subsequently expanded to include minimization of transient diesel engine emissions. This poses additional challenges due to the increased state space. The problem is computationally intractable by stochastic dynamic programming and is solved using the newly proposed neurodynamic programming framework. Finally, the supervisory controllers are implemented and evaluated using simulations and an engine-in-the-loop facility. It is shown that, by designing an intelligent multi-objective controller, significant reduction in both the fuel consumption and the emissions can be achieved compared with strategies which focus solely on the fuel consumption.

Modeling, Simulation and Design Optimization of a Series Hydraulic Hybrid Vehicle

Crude oil resources in the world continue to diminish; automobile, agricultural machinery and construction machinery manufacturing companies are placing more emphasis on energy efficient series hydraulic hybrid systems which can replace their conventional transmission systems. Series hydraulic hybrid system is a mechatronics system with two source of power (that includes prime mover and hydro-pneumatic accumulator) which drives the vehicle. Even though, it has been proven as an energy efficient system, sizing of the components or sub-system for automobiles has got a major influence on energy efficiency of vehicle. In this paper, a power bond graph approach is used to model the dynamics of series hydraulic hybrid system and simulation results elucidate various modes of operations. It also shows the dynamic response of hydro-pneumatic accumulator, prime-mover and system output speed. Further, design optimization of system is carried out to optimize the physical /process parameters for the maximum system's output energy that, leads to increase in energy efficiency and environmental friendly vehicle.

Modeling and Simulation Study of a Series Hydraulic Hybrid Vehicle

As a branch of the Hydraulic Hybrid Vehicle (HHV) technology, Series Hydraulic Hybrid Vehicle (SHHV) has been an important research object of institutions and automotive manufacturers all over the world. With the flexibility of engine management and regenerative braking characteristics SHHV is expected to be a short-term solution to develop a higher efficiency, cleaner, and safer transportation. In this work, the function and parameter determination of key components for SHHV are discussed. Based on the analytical analysis, the suitable set of component parameters is selected. The model of SHHV is implemented via Simulink/MATLAB mostly based on SimScape toolbox. The proposed model can be used as a development tool to quickly simulate the real hybrid system when it allows applying different parameter sets and in various conditions. The performance of the system is evaluated through some specific cases and the capability of braking energy recovery of the system is also investigated. Simulation results indicate that for a 2.5 ton truck case, more than 86% of braking energy can be captured and more than 72% of that energy can be returned to the kinetic energy of vehicle motion.

Thermostatic Control for Series Hydraulic Hybrid Vehicle (SHHV) Energy Management

The main contributions of this paper are the development of forward-facing model of a series hydraulic hybrid vehicle (SHHV) power-train for medium size trucks, of which the fundamental architecture is described, together with dynamic equations and basic features of subsystem modules. A thermostatic SoC supervisory power management control algorithm is assessed, with the expectation that series configuration would maximize the fuel economy as engine is decoupled from the wheels. Simulation results over the urban driving cycle represent a significant departure from the conventional wisdom of operating the engine near its sweet spot and indicate what is preferred from the system stand-point, and also demonstrate the potential of the selected hybrid system to substantially improve vehicle fuel economy.

Stochastic model predictive power management strategy for series hydraulic hybrid vehicle

With the expectation that series configuration would maximise the fuel economy as engine is decoupled from the wheels, a forward-facing, series hydraulic hybrid vehicle (SHHV) powertrain model for medium size trucks is developed in this paper, and is employed to investigate the application of stochastic model predictive control (SMPC) methodology for developing power management strategy. For properly managing all the control variables that arise from the significant freedoms introduced by the SHHV powertrain, two-level hierarchical control architecture is proposed. Simulation results over the urban driving cycle are presented to demonstrate the effectiveness of SMPC compared with other deterministic approaches and the potential of the selected hybrid system to substantially improve vehicle fuel economy.