CONSTANT WORK-POINT CONTROL FOR PARALLEL HYBRID SYSTEM WITH CAPACITOR ACCUMULATOR IN HYDRAULIC EXCAVATOR

Limitations of various accumulators in hybrid hydraulic excavator are analyzed. A program using capacitor as the accumulator based on constant work-point control is put forward. A simulating experimental system of hybrid construction machinery is established, and experimental study on constant work-point control for parallel hybrid system with capacitor accumulator is carried out using the pressure and flow rate derived from boom cylinder of hydraulic excavator in actual work as the simulating loads. A program of double work-point control is proposed and proved by further experiments.

Input Split Hydraulic Hybrid Bus and Control Strategy

Simple and efficient energy management strategy is the key to ensure hybrid vehicle performance. Based on hybrid dynamical system theory and the concept of finite state mechanism,power split hybrid connected structure hydraulic hybrid system was proposed and described. In order to meet the demand for driving,the layered advanced control strategy was proposed in this paper,which referred to vehicle driving experience. Using Matlab /Simulink /Stateflow hybrid modeling method, the economy performance and the acceleration performance of the vehicle under the typical city driving cycles were carried on the simulation analysis. The results show that the proposed topology and control strategy can obviously improve engine output characteristic,effectively enhance the vehicle's instantaneous power performance and economy,and also has a better adaptability in different traffic environments.

Mode Switching and Consistency Control for Electric-Hydraulic Hybrid Steering System

Electric-hydraulic hybrid power steering(E-HHPS)system,a novel device with multiple modes for commercial electric vehicles,is designed to realize both superior steering feel and high energy efficiency.However,inconsistent steering perfor-mance occurs in the mode-switching process due to different dynamic characteristics of electric and hydraulic components,which even threatens driving safety.In this paper,mode-switching strategy and dynamic compensation control method are proposed for the E-HHPS system to eliminate the inconsistency of steering feel,which comprehensively considers ideal assistance characteristics and energy consumption of the system.Then,the influence of disturbances on system stability is analyzed,and H_(∞)robust controller is employed to guarantee system robustness and stability.The experimental results dem-onstrate that the proposed strategy can provide a steering system with natural steering feel without apparent inconsistency and effectively minimize energy consumption.

Parameters Matching and Control Method of Hydraulic Hybrid Vehicles with Secondary Regulation Technology

Hydraulic hybrid vehicles （HHV） with secondary regulation technology has the potential of improving fuel economy by operating the engine in the optimum efficiency range and making use of regenerative braking. Hydrostatic transmission technology has the advantage of higher power density and the ability to accept the high rates and high frequencies of charging and discharging, both of which are not favorable for batteries, but the lower energy density requires special power matching design and control strategy to coordinate all the powertrain components in an optimal manner. A multi-objective optimization method is proposed to distinguish the components size values of HHV by considering the requirements of driving cycles and technology aspects. The regenerative braking strategy and energy control strategy based on the optimized HHV is proposed to recovery the braking energy and distribute the regenerated braking energy. Simulation results show that by taking the optimized configuration of HHV, adopting the regenerative braking strategy and energy control strategy are helpful to improve the system efficiency and fuel economy of HHV under urban driving cycles.

Implementable Strategy Research of Brake Energy Recovery Based on Dynamic Programming Algorithm for a Parallel Hydraulic Hybrid Bus

The purpose of this paper is to develop an implementable strategy of brake energy recovery for a parallel hydraulic hybrid bus. Based on brake process analysis, a dynamic programming algorithm of brake energy recovery is established. And then an implementable strategy of brake energy recovery is proposed by the constraint variable trajectories analysis of the dynamic programming algorithm in the typical urban bus cycle. The simulation results indicate the brake energy recovery efficiency of the accumulator can reach 60% in the dynamic programming algorithm. And the hydraulic hybrid system can output braking torque as much as possible.Moreover, the accumulator has almost equal efficiency of brake energy recovery between the implementable strategy and the dynamic programming algorithm. Therefore, the implementable strategy is very effective in improving the efficiency of brake energy recovery.The road tests show the fuel economy of the hydraulic hybrid bus improves by 22.6% compared with the conventional bus.