noted the effect of nonlinear friction in harmonic drive on system transmission performance, while Aliev studied the dynamic behavior of flexible gear in harmonic drive in 1986.
#Harmonic drive full
Since the teeth of the flexspline are usually two fewer than that of the circular spline, for a full revolution of the wave generator, the flexspline will only counterrotate a very small angle of two teeth, so the harmonic drive generates a high transmission ratio.Įxploded view of harmonic drive and installation. The counterrotation of flexspline is a combined effect of meshing between flexspline and circular spline and pushing driven by the wave generator, as demonstrated in literature.
Simultaneously, the teeth on the flexspline will mesh with that of the circular spline at regions near the major axis of the wave generator, which would create a counterrotation at the flexspline output with respect to the wave generator.
#Harmonic drive generator
The elliptical wave generator which rotates within the flexspline deflects the flexspline slightly from its natural circular form into an elliptical shape continuously. The transmission form is mainly a reduction drive that is, the wave generator is connected to the motor axis and the flexspline is connected to the output, while the circular spline is fixed. Therefore, it is essential to have a detailed understanding of the dynamic behaviors in harmonic drive.Ī harmonic drive consists of the three main components identified in Figure 1: flexspline, circular spline, and wave generator. designated the high friction and the dynamics of the flexspline in harmonic drive as the main issues that significantly challenge the control systems. showed that the nonlinear, elastic attribute of the harmonic drive might deteriorate the static control accuracy due to the transmission error with hysteresis. For example, Taghirad and Belanger demonstrated that harmonic drive systems suffer from high flexibility, resonance vibration, friction, and structural damping nonlinearities. In the meantime, as a critical transmission component, some unexpected dynamic behaviors of the harmonic drive are presented in the previous literature. Since harmonic drive was invented in the 1950s, it has been widely used in various types of important electromechanical equipment such as robots, machine tools, radars, satellites, space rovers, spatial manipulators, and other weapon systems because of their desirable characteristics of near-zero backlash, light weight, compactness, and high gear ratio. The results show that the influence of the component stiffness on the system dynamic response is more significant at high driving velocity, the increase of the stiffness of each component will decrease the dynamic transmission accuracy of harmonic drive, and the bearing radial stiffness is the most sensitive parameter to system’s dynamic response among all the stiffness factors. Based on the proposed model, the influence of different component stiffness on the velocity step response of the harmonic drive is analyzed.
#Harmonic drive series
A series of experiments on the dynamic transmission error at different driving velocities are carried out to verify the proposed model. A dedicated experimental apparatus based on double motor twisting is constructed to measure the characteristics of harmonic drive, and the attribute parameters of the proposed model are identified. To highlight the key factors which influence the dynamic performance of the harmonic drive, a refined harmonic drive model considering nonlinear stiffness, kinematic error, and friction of the critical components is established.