Research On Power Match And Energy Saving Control Of Hydraulic Excavator Driving System

With the increase of variety and quantity of construction machinery, limit to the emission-quality and noise level becomes more strictly. With the enhancement of people environmental protection awareness, study on the environment-friendly product is the trend for the research and development of construction machinery. In days of energy crisis and environment-friendly, energy saving of excavator is of higher development potential project. Under this background and combining the national "863" project, aiming at research on powerful and economical excavator, the thesis makes research on power match and energy saving control of excavator's driving system. The main research work as follows:The development of research on energy saving control of excavator's driving system at home and abroad is surveyed. Characteristic and working condition of excavator are analyzed. Relationship and information delivery method among engine, pump, load and operator are given. The form and reason of energy lose arousing by improper match of driving system are given. Based on hardware environment of PLC and PC104 and software environment of VxWorks embedded system, the general control scheme of excavator is put out according to the characteristic of excavator and trend of energy saving control technique.The transfer function among engine effective torque, speed and cycle fuel feeding are established. Greater than 1/4 of the maximum displacement is the economic zero of pump. The following power control method is based on this. The characteristic and efficiency of LUDV (Load Independent Flow Distribution Control System) system is analyzed. And then the flow equations are developed. Starting with the basic equations of hydraulic systems and according to experiment and practice, a simplified model of electro hydraulic system is obtained. The estimation methods and formulas for equivalent mass, bearing force of hydraulic cylinder and flow gain coefficient Kq are given.Expression of bucket tip posture and the relationship between the manipulator rotation angle and cylinder distant are put out. the four excavating duty cycle and relief conditon of cylinder are sucessfully distinguish. Expression between load force and system pressure is established. The simulation of bearing force of hydraulic cylinder when the bucket moves at the level lines under free load is given. Under free load, fixed load and actual working condition, the pump pressure is test. Weighted average filtering method is used to process the pressure signal. The load condition is distinguished based on the pressue probability distribution and the posture of manipulator. Section function is adopted to fitting the perfect displacement control curve. The ramping function is used to control the actuator speed. Three criterion to judge the idle control performance is put out. Adaptive control is used to optimize the domain of PWM duty ratio, the minimum ramping time and idle speed.According to the normally used working zero of engine, the engine fuel supply control, pump power control, difference pressure of load sense valve control and output pressure of proportional relied valve control are coordinated. The method of adjusting P-Q curve is put out to realize economic matching among engine, pump and load. The method of combining constant power control with variable power control is put out to realize powerful matching control.The characteristic of engine working at different mounting way and different environment is analyzed. Selecting pump pressure, speed difference and its variance ratio as input, and current of pump power control and pressure difference control as output, fuzzy control is adopted to improve the power matching and energy saving control method.Testing platform is established. Using ratio between output power of pump and fuel consumption to appraise the economic performance of excavator. Under free load, 490kg fixed load and actual working condition, pressure and flow of pump and fuel consumption of engine is test. From the result, no matter on the constant load or variable load, it got good results at different speed and different working condition, especially at the actual working condition, it got at least 8% energy saving using the power matching control method. It proved that the power matching control method is correct and availability. Moreover, the paper put this method into use in the other kind of machine; it also got good result, which established expansive base for the further usage.Generally, the paper aims at powerful and economic control. Taking engine, pump, load and operator into consideration, put out idle control, adjust p-Q curve control, constant power control, variable power control and fuzzy control, solves the energy losing problem. Finally, put the theory into practice use and get good results. The paper provides systematic and intact power matching and energy saving control method for the excavator driving system.