Adaptive Control ofRobotic Deburring Process Basedon Impedance Control

Field: Engineering (Physical Sciences)

An adaptive algorithm forthedetection ofburrs andcavities onaworkpiece isproposed forthebeburring process. The conventional forcecontrol methodforthe deburring process hastheinherent characteristic ofleaving thedeburred surface oredgeasanimprint oftheoriginal and cannotdistinguish theposition deflection oftheend-effector andthelarger burrs. Bytheadaptive algorithm, thereference cutting force innormaldirection andthefeed-rate canbe adjusted automatically according tothevariation oftheburr size togetsmoothsurface. A process force modelconsidering theburrseffect isdeveloped topredict thecutting force. Furthermore, theproposed algorithm isintegrated intothe impedancecontrolforthe deburring operation. The simulation experiment hasshownthattheadaptive algorithm iseffective todetermine theexistence oftheburrs, obtain the desired contour andimprove themachining efficiency. I.INTRODUCTION Automated robotic deburring systemshavebeen investigated foranumberofyears asareplacement for manual operation, whichisconsidered aslabor intensive andlowproductivity method. Itshows that thecutting force intangential direction varies withtheburrsize, while the forceinnormaldirection maintains almost constant regardless oftheburrsize whentheburrs arerelatively small anduniform (1,2). A consistent chamfer therefore can beobtained thecontrol oftheconstant normal force. The constant force control inthenormal direction isaneffective method indeburring process, butasthevariations ofthe burrs sizes arelarger andtheburrs aregreater thenormal force cannolonger beusedasanaccurate measure ofthe chamfer depth. Thecontrol strategy based onconstant force will result inanunevenchamfer foritscharacteristics in nature. Inaddition, whentheforce required toremoveburrs isequal toorgreater thantheforce required tochamfer, it becomesdifficult todistinguish thedeflection ofthe end-effector causedby the disturbance, part misalignment, tool wearandthegreater burrs. Manyadaptive force controllers forrobotic finishing processes havebeenconsidered (3,4)tosolve these problems. In(3), theadaptive technique ofminimizing the force error wasusedtocompensate foruncertainties in unknown workpiece. Adaptation ofthegrinding coefficient thatrelates thenormal andthetangential force onthe surface hasbeenstudied in(4). Few alternatives or additional vision sensors wereinvestigated togettheburr size, location andthecutdepth (5,6). A generalized burr modelbased rapid deburring passplanner waspresented utilized toidentify burrshapeandthechamfer depth information witha laser vision sensor (5). Butvision sensors arerestricted inthemachining operation forthe chips anddustinenvironment. In(7,8),anewcontroller wasproposed with alogic module tomodify thethrust force basedontheburrs presence ornot,andthecontroller performed well indetecting burrs andachieving thedesired chamfer depths andwasrobust inface ofpart misalignment androbot baseerrors. Whereas thetangential cutting force, feed-rate andthewearofthetools, which arecrucial tothe quality ofdeburred surface, werenotbediscussed. Recently, fuzzy logic orneural networks havebeenapplied forcontrol todeal withthehighly variable ofburrs (9-1 1), however, it isdifficult todesign thefuzzy controller systematically. The neural network controller, however, requires prelearning or timeforadapting, andisrestricted inreal-time control of machining. Animpedance control method with anadaptive algorithm isproposed inthispapertosolve theproblem. The deflection ofend-effector andworkpiece defects canbe detected. Theinput reference cutting force andthefeed rate canbeadjusted according tothedifferent situations. Itis effective togetthesmooth surface andreduce therepetition times ofdeburring procedure.