Research On Fault Prognosis Method Of Industrial Robot Based On Self-organized Criticality Theory

Industrial robots,as a kind of sophisticated and complex Mechatronics system,are used in various automatic production lines and play an important role in the transformation and upgrading of labor-intensive industries.However,the cost of daily maintenance and maintenance of robots is quite high,besides,managers are in a passive position during the process of maintenance.The resulting shutdown will cause certain losses to factories and enterprises;So,if we can forecast faults earlier,prepare well for dealing with accidents in time and solve some potential problems,it is possible to deal with industrial robots' faults in essence.Therefore,this paper firstly analyze of the factors affecting the error of industrial robots,establish the error model of ABB IRB120 six degree of freedom industrial robot(Hereinafter referred to as IRB120 industrial robot).Secondly,bases on the current working state of completing the acquisition and analysis of the vibration signal.Thirdly,using self-organizd criticality theory analyze the position and posture error fault of IRB120 industrial robot.Finally,plot the calculated results on the Statistical Process Control chart in order to come ture the prediction of robot fault.The main contents are as follows:(1)Analyze of the factors affecting the error of industrial robots.Establish the DH model of IRB120 industrial robot,then by the direct transformation method establish the transformation matrix of a joint axis relative to the base coordinate system and verify the feasibility of this method.Set up the error model of industrial robot by the direct transformation method,it provides theoretical support for the follow-up study of the fault issue caused by robot pose error.(2)Study the theory of self-organized criticality in complexity science,and then take sand pile model for an example to clarify and illuminate the meaning of self-organized criticality.Use vibration displacement of IRB120 industrial robot as characteristic quantity to study the IRB120 industrial robot's fault issue due to the fact that the repeated positioning accuracy of IRB120 industrial robot can not meet the requirement.Result shows that the third and the fifth joint axes have great influence on the fault issue,and the vibration displacement of the third joint axis has self-organized criticality characteristics.By the self-organized criticality theory to find the criticality state of IRB120 industrial robot occur fault issue because of pose error and the corresponding criticality numerical value.(3)Establish control limits based on the obtained data,including the upper and lower control lines of the control chart and the self-organized criticality value obtained in Chapter 3.Based on self-organized criticality characteristic of vibration displacement sample of IRB120 industrial robot,using the control chart which has the characteristics of prophylaxis to analyze the data of IRB120 industrial robot during its working process.Result shows that the above method can achieve the purpose of robot's fault prognosis.