Research On Harmonic Drive With Short Flexspline For Robot And Its Experiment Studies

The normal harmonic drive does not meet the installation space demand in thepractical application of the humanoid robot, so short flexspline harmonic drive isintroduced in order to maintain the performance of the reducer. Compared to the normalharmonic drive short flexspline harmonic drive’s structure is more compact, lighter inweight. Not only in the humanoid robot, in other areas there is an increasing demand.But there is big gap between the domestic product and the imported one due to theproblem of design and manufacture.Teeth profile of flexspline was determined, on the basis of pitch line method, theconjugate profile of flexspline was calculated. According to the characteristic of theshort flexspline which is when wave generator assembled in the flexspline, theflexspline has a larger tilt angle causing meshing area between flexspline and circularspline declining, so using two-arc flexspline tooth profile as the flexspline’s toothprofile and the circular spline with a certain angle was introduced.A harmonic drive finite-element model for type size50with short flexspline withcontact pairs including flexible bear of wave generator was proposed. Equivalent stress,deformation, contact stress and area of contact were studied. The design method thatcircular spine with tilt angle proved effect by the result of FEA. The meshingperformance of the short flexspline with the circular spline of angle of0.2°increases by35%in the contact area.On the basis of the type50, the1/4short flexspline and circular spline weredesigned and manufactured using the chosen angle0.2°by WEDM-LS. The processesof manufacturing were given in details. The prototype was successfully made.According to the transmission stiffness is mainly determined by the size of themeshing area, the prototype was tested in the transmission stiffness and hysteresisexperiments compared to the normal one. The result shows that short flexspline with thecircular spline of angle of0.2°has a39%larger transmission stiffness which means ithas larger contact area between teeth indirectly. Finally using the two harmonic driveswith normal teeth and tilt teeth in the transmission stiffness experiment,2DOF robotarm has been made.