The Reliability Research Of The Hexapod Bionic Robot With The 2UPS+UP Mechnism As The Mechanical Legs

Using the reliability mathematics as the analysis tools, the reliability problem of a hexapod bionic robot was studied. The robot was researched and developed by our group and the State Key Laboratory of Mechanical System and Vibration of Shanghai Jiao Tong University, and the structure of all the six mechanical legs is the 2UPS+UP mechanismIn the process of installation and debugging,an incongruous phenomenon appeared in one leg, it was because of some raffle is in the groove of one ball screw after inspection, this is the background of this dissertation. Three methods were used from static to dynamic. Firstly, from a static view, using the fault tree analysis tool, the effect of the reliability of the eight joints on the reliability of the whole 2UPS+UP mechanism was analyzed: The minimum cut sets and minimum path sets of the top event was given, the reliability formula of this mechanism was got. An algorithm of calculating the value of the structural important function was presented, the MATLAB source code was given, and the relationship among the structural important degrees of the eight pairs was analyzed. Secondly, from the perspective of dynamic, with a continuous time Markov processes as the repairable system analysis tool, the effects of the failure rate of three branched chains on the reliability of the whole mechanism was analyzed: Using the visualization method, the transient state probabilities, the transient availability and the transient fault frequency of the repairable system was analyzed in detail; The reliability equation which shows the variation law of the transient reliability changes with the failure rate of the three branched chains was obtained, and the size relationships of the effect of three branched-chain’ failure rate on the mechanical leg were compared; The steady state reliability indexes were got. At last, considering that in the actual repairing process, checking a system is at a fixed interval, rather than always, the repairable system using a discrete time models was analyzed: The transient and steady state reliability indexes were got; Similarities and differences of the reliability indexes between the two repairable systems were compared, and the reasons were analyzed.After the adequate discussion of the mechanical legs’ reliability, the reliability of the hexapod robot was analyzed. Firstly, using the 5/6(G) voting system as the analysis tool, the case that only one leg failed was analyzed: the reliability and failure rate of unrepairable system were given; Reliability indexes of the repairable system were analyzed; The reliability index in the unrepairable and repairable systems was compared. Secondly, only two nonadjacent failure legs were accepted: A new reliability mathematics tool—the ring style 4/6(G) conditional voting system was presented, and the complete definition of this tool was given; Using the new tool, the reliability indexes of the unrepairable and reparable systems were analyzed respectively. At last, some important reliability indexes of the two cases were compared, the size relationships of reliability indexes between the two cases was obtained.The dissertation begins with the reliability analysis of the mechanical leg, and ends with the reliability discussion of the hexapod bionic robot. The results of this dissertation can be used to guide the production and after-sale services of the 2UPS+UP mechanism, as well as the hexapod robot; The results about the hexapod robot are not limited to the 2UPS+UP mechenism as mechenical legs; The comparison results between the two cases of the hexapod verified the practical significance of the gait planning and the trajectory planning of the hexapod bionic with failure legs; The continued research about the new reliability tool — the ring style 4/6(G) conditional voting system — can enrich the theoretical system of reliability mathematics.