| With the rapid development of heavy load robot and high-end equipment manufacturing industry and their increasingly strategic position,higher requirements are put forward for the control performance and system energy efficiency of driving technology.The driving modes of actuators are mainly pneumatic driving,electric driving and hydraulic driving.Pneumatic driving is seldom used in high-power mechanical equipment due to low working pressure level and poor stability although it is efficient and environmental.Electric driving has obvious advantages in the efficiency of the mechanical actuator and the accuracy of motion control,but the power output capability of electric driving is relatively limited due to the magnetic saturation performance of the magnetic conductive material.Hydraulic driving has been widely used in engineering machinery,aerospace,equipment manufacturing and other fields due to its advantages of high output force/torque,high power density and strong overload capacity,but there are shortcomings of high energy consumption and imprecision control performance.At present,the researches on driving technology are mainly studying energy-saving technology of hydraulic system to improve energy efficiency and control strategy of hydraulic system to improve control performance,but it is difficult to consider both high energy efficiency and high control performance due to the limitation of its own characteristics.In this paper,in order to ensure high power density,high precision and high energy efficiency synchronously,a structure scheme of electro-hydraulic composite driving cylinder system combining electric driving and hydraulic driving is proposed.The system which integrates the advantages of high control performance of electric driving and high power density of hydraulic driving,realizes high precision motion by active control of speed and torque of motor,and high power density and fast response by passive control of pressure and flow of hydraulic system.The major constituent units of the system are analyzed and the parameters of the key components are matched.The mathematical models of the valve-cylinder system,pump-cylinder system and electro-hydraulic composite driving cylinder system are constructed respectively,and the control performances of open-loop systems and closed-loop systems of three systems are analyzed.In order to adapt the system to different loads,an allocation strategy of electric and hydraulic energy based on load identification is proposed and the critical loads in the scheme are designed.The AMESim system simulation models of electro-hydraulic composite driving cylinder are established to study the influence of open/closed-loop control methods on system control performance and verify the rationality of the allocation strategy of electric and hydraulic energy.According to the working principle of the system and the parameter setting of the components,the test platform of electro-hydraulic composite driving cylinder system is built.In order to compare with the traditional hydraulic control system,a contrastive test platform of valve/pump-cylinder system is built.A set of computer-aided test system is built for both two sets of test platforms.Based on the test platforms and the AMESim system simulation models,the control characteristics and energy conservation of the electro-hydraulic composite driving cylinder system are simulated and tested.The results show that the electro-hydraulic composite driving cylinder system has good power amplification characteristics.For the velocity control,the velocity response under the step input,the mutational velocity response under the square wave input and the velocity following ability under the sinusoidal input of the electro-hydraulic composite driving cylinder system are superior to those of the valve/pump-cylinder system;For the position control,the positioning accuracy under the slope input and the position following ability under the sinusoidal input of the electro-hydraulic composite driving cylinder system are superior to those of the valve/pump-cylinder system;The efficiency of the electro-hydraulic composite driving cylinder system increases with the increase of the load,and it is higher than valve/pump-cylinder system under the same load.The electro-hydraulic composite driving cylinder system proposed in this paper has good performance in driving power,control characteristics and energy saving. |
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