Research On Bionic Hydraulic Driving Technology And Efficiency For Multi-joints Robot

With the development of the performance of the mobile robot,its application scope expands unceasingly,while the traditional motor driven mobile robots are difficult to perform the tasks of large loads due to its limited load capacity,such as the combat mission bearing weapons and equipment on special terrain battlefield and the rescue mission carrying the rescue equipment in the earthquake-stricken area.Thereby,the hydraulic power driven mobile robots have more and more riveted people attention because of its advantages of the large load capacity and high mobility.Due to the limitation of size and weight,the hydraulic system structure of the mobile robot always commonly adopts Sing Pump Source &Multi Actuators(SP&MA).But in the process of the robot motion,each actuator has a different load at the same time,and any one actuator has widely fluctuating forces and displacements over time,so the hydraulic system of the mobile robot has low efficiency due to the mismatch between the system pressure and the load.The low energy efficiency will restrict the practical process of this kind of mobile robot and does not match the theme of energy saving and environmental protection.It aimed at the problem of the low efficiency of the hydraulic system of the mobile robot,the study of this dissertation are carried out form two aspects of energy supply and output of hydraulic system to improve the matching degree of the supply pressure and the load.This dissertation has proposed a mechanism of bionic multi-stage energy supply hydraulic system and high efficiency hydraulic actuator by imitating the biological multi-stage energy supplement and muscle structure and the adjustment mode of its different output force.The main contributions and innovations are concluded as follows:(1)The reasons for the low efficiency of the typical SP&MA hydraulic system of the mobile robot are analyzed in detail.In order to specify this reason and provide a comparison basis for verifying the proposed energy efficient methods,a bionic quadruped robot with 16 actuators is designed in this dissertation.Then the dynamic simulation of the quadruped robot is given and analyzed based on the three typical motions which are squats,turns and trots.And according to the simulation results,the efficiency of the typical SP&MA hydraulic system of the robot is calculated.(2)The design and analysis of the bionic energy efficient multi-stage energy supply hydraulic system are carried out in detail.For the first time the bionic multi-stage energy supply method is introduced into the design process of the multi actuators hydraulic system of the mobile robot.With respect to this design mothed,it comes up with a double-stage energy supply system(DSS)using small accumulators which are distributed layout.The DSS is a composition of a low pressure variable pump and distributed instantaneous high power sources.The former provides energy for most continuous works under low-pressure,while the latter is established to satisfy instant high-pressure demands by the small accumulators.The principle of DSS is described and the DSS is analyzed to explain the main reason that the efficiency of DSS is lower than that of the single-stage energy supply system(SSS).(3)This dissertation propose a novel fluid power converter(FPC)based on the principle of pulse-width modulation control,which is analogous to a boost converter in power electronics.The FPC is introduced into the DSS to improve the pressure match degree when the DSS carries out the most continuous works under low-pressure.The FPC utilizes the energy conversion between the mechanical energy and the fluid power to achieve the regulation of the output pressure and flow rate.The FPC is different to the traditional throttling control(resistance control RC)which relies on dissipation of power,and the FPC has the energy efficient characteristics.In this dissertation,the principle of the FPC is described and the structure of key inertia components is designed in detail.The simulation model based on the mathematics models is built to analyze the performance of the FPC.It is clearly shown that the FPC can keep the high energy efficiency when adjusts the pressure and flow rate.(4)The design and analysis of the bionic energy efficient hydraulic actuator are carried out in detail.First time the bionic mechanism is introduced into the design the hydraulic actuator by imitating the multiple fibers and motor units structure and the recruitment mode of the motor units of the human muscle.Under guidance of this mechanism,a kind of bionic hydraulic actuator is proposed.The structure design,analysis and optimization of the actuator are carried out in this dissertation,and some other structures development plans are given.Through establishing the energy loss model of the bionic and the traditional hydraulic actuator,the reason for the high energy efficiency of the bionic actuator is explained in detail.Finally,the simulation analysis of the load matching control of the bionic actuator is carried out.(5)The simulation and experimental verification of the DSS and the bionic hydraulic actuator are presented in this dissertation.The simulation models of the hydraulic systems based on DSS with the FPC or not and the bionic actuator are established,respectively.Using the object of quadruped robot designed in this paper,the energy efficiency of the corresponding hydraulic system is calculated when the robot makes the three typical motions.It is verified that mothed proposed in this paper can improve the energy efficiency of the hydraulic system through comparing with that of the typical SP&MA hydraulic system of the robot.(6)To further verify the characteristics of the bionic actuator,three prototypes and one arm experimental platform are proposed.Through testing the friction force of the bionic hydraulic cylinder with the asymmetric and symmetrical structure,it is proved the optimized structure is better.Finally,the experiments that the bionic actuator respectively drives the arm robot to lift 10 kg and 15 kg weights are carried out.The results show that the bionic actuator can achieve the aim of energy saving and high efficiency through the load match.The bionic design mechanism of the multi-stage energy supply and the actuator provide the guidance for the design of the hydraulic system of the mobile robot.At the same time,the DSS and bionic actuator proposed in this paper have positive significance for putting forward the practical process of the hydraulic driven mobile robot.In addition,these methods are of universal applicability,and can be used to improve the energy efficiency of the hydraulic system of engineering machineries with multiple actuators,so this paper studies also have a certain economic value.