Tentative title Design and development of a backlash-free cycloidal cycloidal gear reducer
Introduction Cycloid speed reducers have found wide applications in the automation field such as industry industry robots, robots, machine machine tools tools and automatic automatic machinery machinery.. Compared Compared to planetary planetary gear gear reducers, cycloid gear reducers possess better characteristics. They are high transmission accuracy accuracy,, large reduction reduction ratio, ratio, great great load capacity capacity,, high efficienc efficiency y, low backlash backlash,, long service life and high shock load capacity. The state of technology and research topics on cycloid gearbox The research research and develop development ment study study conducted conducted by various various researchers researchers on the cycloid speed reducers have covered the following topics . !per !perat atin ing g prin princi cipl ple e ". Conditio Conditions ns for for non-un non-underc dercuttin utting g manufac manufacturi turing ng #. $orce $orce ana analys lysis is and and effi efficie ciency ncy %. Devel Develop opmen mentt of new mechan mechanism isms s
The research problem in this study &ll the gear drives have certain amount of backlash which is undesirable undesirable in applications re'uiring high positional accuracy. (xamples of such applications are in the automation field such as industry robots, machine tools and automatic machinery. )o there is a need to develop a cycloid gearbox with *ero backlash. The tentative title is fixed based on the various research papers on different aspects of cycloid gearboxes and backlash of planetary gearboxes. The main ob+ective of this study is to design, analyse and develop a high efficient cycloid gear reducer with minimum backlash.
The literature survey In the design design of the cyclo cycloid id speed speed reduc reducer er,, design designers ers alway always s consid consider er certai certain n ob+ective ob+ectives s such as efficien efficiency cy,, weight, weight, load capacity, capacity, contact contact strength strength dependi depending ng on the re'uirements. &lso, there are interactions and constraints between these ob+ectives. ian ang / carried out an optimi*ation methodology based on genetic algorithm. The goal of the study was to simultaneously minimi*e volume and maximi*e efficiency. The research resul results ts can help help design designers ers to employ employ for minim minimum um materi material al and and cost cost by fulfil fulfillin ling g high high efficiency and other performance re'uirements. re'uirements. Cycloid gear drives have some inherent drawbacks namely, backlash and tor'ue ripple which lower the performance of a drive in high precision and high speed applications. 0acklash and tor'ue ripple are caused directly by the existence of machining tolerances. They They are usuall usually y inevit inevitabl able e due due to many many practi practical cal consid considera eratio tions ns such such as precis precision ion of machine tools, prevention of +amming conditions, and application of lubricants, etc. 1ery slight machining tolerance will cause a significant amount of backlash in the +oint. If this
mechanism is used as a +oint transmission in a robot arm, the resulting positional error would be unacceptable "/. The work done by an-)ung 2in #/ presents the new design of a two-stage cycloidal speed reducer. Two new structures of two-stage cycloidal speed reducers were enumerated after topological analysis. & new configuration with the least number of links and +oints was chosen to establish the design procedure and a mock-up was fabricated to validate the feasibility of this type of two-stage cycloidal drive. 3odifications of the cycloidal gear profile and transmission errors were analy*ed 'uantitatively. It was shown that a smaller 'uantity of modification in a single type of modification yields smaller kinematic errors. 0ased on the results obtained, this new cycloidal drive is reali*able as a compact, high speed reduction ratio, and high accuracy speed reduction device. In the work done by 0ingkui Chen %/, a new cycloid drive with double contact lines between one tooth pair was generated by applying double-enveloping theory in cycloid drives. The meshing e'uation, tooth profile e'uation, meshing line e'uation, and t he induced normal curvature formula for this new cycloid drive are established and derived. The author made the physical prototype and the transmission error of the prototype was also tested. & nonlinear manipulator +oint model with planetary gear train transmission was developed in the research conducted by Tianfu 4ang 5/. In this model, the time-variant stiffness of planetary gear train and the backlash were taken into consideration. The stiffness of the e'uivalent model was built based on the gear parameters and meshing phase relationship. The backlash effect was modeled as an alternate engagement mechanism. The backlash was the main source of positioning error and impact. The backlash could not be avoided. 6ence, precision modeling and manufacturing technology in controlling backlash is critical in precision manipulator systems. The study by Chiu-$an 6sieh 7/ constructed an analytic model of system dynamics in a cycloid reducer with a small tooth difference. )pecifically, taking a transmission ratio of 8 as an example, it analy*ed both free-pin and fixed-pin designs to show the shortcomings of traditional designs. It then proposed a non pin design that improved on these shortcomings, one in which the pinwheel is replaced by a cycloid internal gear. It determined the parameter design range of non undercutting. The results indicated that appropriate design parameters could indeed improve on the shortcomings of the traditional design.
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9eferences ian ang, )hanming 2uo, Deyu )u, :3ulti-ob+ective optimal design of cycloid speed reducer based on genetic algorithm;, 3echanism and 3achine Theory <" ="<7> #5?%@ 4ang D. C. 6., 0lanche . A., :Design and application guidelines for cycloid drives with machining tolerances;, 3ech. 3ach. Theory, 1ol. "5, Bo. 5, pp %@8-5<, < an-)ung 2in, 4i-ei )hih, yh-one 2ee, :Design of a two-stage cycloidal gear reducer with tooth modifications;, 3echanism and 3achine Theory 8 ="<%> @%? 8 0ingkui Chen, 6ui Ehong, ingya 2iu, Chaoyang 2i, Tingting $ang, :Aeneration and investigation of a new cycloid drive with double contact;, 3echanism and 3achine Theory % ="<"> "8
5. Tianfu 4ang, )hao*e4an, Eengyao6an, :Bonlinear model of space manipulator +oint considering time-variant stiffness and backlash;, ournal of )ound and 1ibration #% ="<5> "%7?"5 7. Chiu-$an 6sieh, :Traditional versus improved designs for cycloidal speed reducers with a small tooth differenceF The effect on dynamics;, 3echanism and 3achine Theory @7 ="<5> 5?#5
