| With the development of technology,the application fields of the industrial robots are gradually widening.In addition to play an important role in the manufacturing,industrial robots are also used in military,service and other fields.As for the application of industrial robots,it has greatly improved social productivity,and freed people from the repetitive and tedious labor.However,the most important premise for robots using in more fields is the adequate safety performance.Nowadays,the security issue of the robots has restricted the further development and application of robot technology,and it becomes a topic in the research of the robot.This paper originated from National Natural Science Foundation project of "Actively Improving the Safety of Robot-arm by Feedback Control of the Force Generated from the Deformation of Viscoelastic Covering".The objective of this project is to make the robot arm cover with viscoelastic material and combine with some appropriate control measures to restrain the force when the industrial robot arm are collided with people,which will improve the safety of robot.The severe collision between people and robot is directly relating to the hardness of the contact surfaces.The robot arm covered with viscoelastic materials can not only reduce the collision contact force greatly,provide the buffer time and absorb the kinetic energy of robot arm,but also increase the contact area between human and robot,further reduce the stress of the collision area.The paper focuses on the effects of mechanical arm of viscoelastic material of collision process have on the collision force,the stress-strain of collision zone,the energy absorption and others,and also complete the modeling and the analyzing of the collision process,which provides a theoretical basis for the selection of viscoelastic materials.Firstly,according to the properties of viscoelastic materials,the paper selects three solid equivalent constitutive relation of viscoelastic material by analyzing the properties of the creep and stress relaxation.It uses the universal testing machine to test and identify the parameter of material model and the dynamic performance of the material.According to the constitutive relations of materials,it builds the model of human freedom collision,analyses the influence of viscoelastic coating and the model parameters on the impact force during the collision process,and analyses the process of the collision through the simulation.Secondly,according to the characteristics of the material dynamic stress-strain and the situation of body force,it realizes the modeling of the human and the robot through the SolidWorks,using the finite element to simulate the process of collision,studying the weakening effect of viscoelastic materials on the stress of collision through the software of LS-DYNA post processing.Finally,it analyses the energy absorption of viscoelastic material during the collision process and the influence of model parameters on the energy absorption ability of the material.It also establishes the material energy losing model of the free falling process,through the design and the construction of the free fall impact experiment,using the high speed camera and the image processing software it gets the displacement changes of the collision and the collision velocity before and after the test,terrifies the material energy absorption effect. |
