Gedong Jiang

A harmonic drive model considering geometry and internal interaction

A new harmonic drive model considering the geometry, internal interactions and assembly error of key parts is proposed in this paper. In this model, a single tooth pair is used to represent the transmission mechanism of harmonic drive. The meshing stiffness between the flexspline and the circular spline, the torsional stiffness of the flexspline cylinder, and the radial stiffness of the thin-walled ball bearing are included and formulated. The kinematic error is fitted using a low-velocity test, and its generating mechanism is analysed. The friction of the harmonic drive is formulated at the tooth meshing section and at the ball bearing, where its parameters are identified based on experimental results. Based on the new model, velocity step simulations are conducted. For comparison, velocity step experiments at eight different velocities from 60 to 3000 r/min are performed, and the simulation results are in good agreement with the experimental results. The new model reveals the dynamic behaviour of the harmonic drive system; therefore, it will be useful for the dynamic design and precision control of harmonic drive systems.

Deformation and stress analysis of short flexspline in the harmonic drive system with load

A detailed surface to surface contact finite element model of harmonic drive system is established in this paper to reveal the stress and deformation states of short flexspline. The boundary condition of the gear teeth meshing is evaluated by experimental formula. The stress and deformation of flexspline are solved and their relationships with varying loads are analyzed. It is found that the deformation and stress at the flexspline gear cross section change geometrically with heightened load, but the distributions of the deformation and stress increments remain unchanged. The solution results are compatible with the cases of flexspline destruction and axial stress distribution under load. This approach can help to optimize the structure and manufacturing process of harmonic reducer and increase the reliability of related automation equipment.

A new method using pole placement technique to tune multi-axis PID parameter for matched servo dynamics

A new method which employs pole placement technique of modern control theory to tune proportional–integral–derivative parameter for simultaneously achieving multi-axis matched dynamics and single axis stability is addressed in this article. This method has the advantage of simplicity in tuning, intuition in principle, and easy in program. Four different cascade proportional–integral–derivative control structures are investigated for applying the matching method appropriately and better understanding of its limitation. The deduction that the feedback gain ratios of position to speed loop of the same type interpolation axes imposed with the same desired poles are approximately equal is obtained. Experimental results show that the servo feed system designed or tuned by the proposed method can easily achieve matched dynamics. Furthermore, this method can be also employed to multi-axis motion system which is composed with both linear and rotating axes.

A Novel Inertia Identification Method for Servo System Using Genetic Algorithm

To improve the dynamic response characteristics of permanent magnet synchronous motor (PMSM) servo system, an inertia identification method based on the theory of model reference adaptive system (MRAS) has been researched. A novel inertia identification method using genetic algorithm (GA) is proposed for requirements of rapid convergence and high precision. This method takes advantage of the global search capability of GA, taking deviation between actual angular velocity and estimated angular velocity as control error, utilizing integral of time multiplied absolute value of error (ITAE) as optimized target, dynamically adjusting adaptive gain of MRAS, to achieve optimization of control parameters on-line. Experimental results proved that this method has a faster convergence rate and a higher precision in inertia identification, confirmed effectiveness and feasibility of this method.

Inertia identification based on model reference adaptive system with variable gain for AC servo systems

To improve the dynamic response characteristics of permanent magnet synchronous motor (PMSM) servo systems, inertia identification based on the theory of model reference adaptive system (MRAS) has been researched. A novel method with variable gain is proposed for requirements of rapid convergence and high accuracy. This method improved by introducing an error integrator, which was employed to adjust the adaptive gain of MRAS dynamically, according to the control deviation between actual angular velocity and estimated angular velocity. Experimental results proved that this method has a fast convergence rate and high accuracy in inertia identification, confirmed effectiveness and feasibility of this method.