Circumferential spatial tooth profile modification of flexspline for harmonic drive: A novel method and a case study

Abstract

Harmonic drive is widely used in the industrial robotics field due to the excellent deceleration performance. The tooth modification of the flexspline in the harmonic drive faces a great challenge. In this paper, a novel spatial tooth profile modification method along the circumferential direction of flexspline for a harmonic drive is proposed. Through the hob circumferential offset, the tooth profile rotates and the tooth thickness of interference part is reduced, then the spatial meshing is realized. The circumferential modification method has a small change of meshing point position and small pressure angle, which is beneficial to maintain the trans-mission accuracy and improve the service life of the harmonic drive. In addition, the relation model of spatial motion between hob and flexspline, and the relation between tooth profile and modification quantity are studied. Two main factors, circumferential modification quantity and radius of flexspline indexing circle on circumferential modification are analyzed. Afterward, the novel stepwise modification of the circumferential spatial tooth profile of flexspline is introduced. Finally, a case study of circumferential spatial tooth profile modification of flexspline for harmonic drive is conducted to show the advantages of the proposed modification method.