Design Of Five-axis Manipulator System With Immediate Electrohydraulic Drive And Its Physical Simulation Based On Gazebo

The load capacity is an important index to measure the performance of the manipulator.As the joint type manipulator is mostly driven by the motor directly,and the motor moves with the joint during the working process,the joint output torque is subject to the weight of the driving motor.The larger the output torque,the larger the size of the motor required;The larger the motor size,the greater the influence of motor dead weight on the load capacity.In this paper,the electrohydraulic direct drive technology is proposed as the dynamic driving mode of the articulated manipulator to improve its load capacity.Based on this,an electrohydraulic direct drive five-axis manipulator system is designed,and the dynamic performance of the electrohydraulic direct drive system is optimized by using the fuzzy adaptive PID algorithm.The main features of the electrohydraulic direct drive manipulator joint are as follows :(1)electrohydraulic direct drive joint is an indirect drive joint,and the volume and weight of the joint are reduced by separating the drive motor from the joint oil cylinder through the oil channel;(2)the hydraulic cylinder has a high energy density,and the output torque is much higher than the combination of motor reducer under the same volume;(3)electrohydraulic direct drive is a rotational speed positive displacement pump control system,whose control object is servo motor.Compared with the hydraulic valve control system,electrohydraulic direct drive has the characteristics of small size,easy to control,simple structure,high energy efficiency,and low pollution.The real manipulator will be affected by inertia,moment of inertia,friction,obstacles and other factors,which are often nonlinear or unpredictable.In order to get close to the real simulation effect,the motion simulation is usually carried out in the simulation environment with a physics engine.In this paper,the efficient,real and visual trajectory planning simulation of the manipulator is carried out in the form of the joint simulation of the trajectory planning software Moveit!and the physical simulation environment Gazebo under the ROS framework.The specific research content is as follows:Structure design of five-axis manipulator with immediate electrohydraulic drive.The electrohydraulic direct drive arm has a special structure.The joint control object is the servo motor,the actuator is the hydraulic cylinder,and each joint is an independent drive modular structure.The whole machine structure can be divided into: single joint hydraulic system,joint mechanical transmission structure,and the whole machine arm structure.Through the analysis of the characteristics of the electrohydraulic direct drive manipulator system,the design and selection are carried out from the aspects of dynamic performance optimization and lightweight principle of the hydraulic system.A compact,lightweight,and modular five-axis manipulator was designed.Study on control performance of electrohydraulic direct drive system.The main disadvantage of the electrohydraulic direct drive technology is that the dynamic performance of the system is not high.In addition,as a manipulator joint dynamic drive,the electrohydraulic direct drive technology still has many nonlinear factors.In this paper,by establishing a mathematical model of the electrohydraulic direct driving system,the main parameters affecting the system dynamic performance is analyzed.On the basis of the mathematical model,the fuzzy adaptive PID algorithm is used to suppress the nonlinear disturbance in the system,and the control effect of the fuzzy adaptive PID controller is simulated by AMEsim-Simulink co-simulation.The result shows that the fuzzy adaptive PID algorithm is better than conventional PID algorithm on the control effect.Research on physical simulation method based on Gazebo.Taking advantage of the convenience of the popular robot operating system ROS,hybot,a five-axis manipulator designed in this paper,is taken as an example to study the implementation process of the joint simulation between the trajectory planner Moveit!and the physical simulation environment Gazebo.It has been proved that this method can quickly build the manipulator simulation environment and carry out high quality physical simulation,which greatly improves the efficiency of the development of manipulator control software.