Dailin Zhang

Globally Optimal Estimates for Rotation Averaging Problems

This paper investigates the difficulty of obtaining the global optimum in rotation averaging problems and presents different representations of rotation matrix. One of the drawbacks is that there is a 2-to-1 mapping when using the angle-axis and quaternion representation of rotation matrix. By using the chordal metric and a hierarchy of convex relaxations to the non-convex rotation averaging problems, the global optimum is obtained most of the time and the ambiguity caused by the other two representations of rotation matrix can be avoided. The experiments show that the polynomial optimization method works efficiently and reliably and the results are certified to be the global minimizer most of the time.

An indirect tire identification method based on a two-layered fuzzy scheme

While the heights and numbers of tires in the assembly line are changing, the traditional methods are difficult to identify the types of the tires, so an indirect tire identification method is proposed to identify the types of the tires, which uses the widths of the tires, the diameters and the shapes of the hubs to classify the tires. First, the tires are identified according to the widths and diameters by using the fuzzy C-means clustering algorithm. Second, the shapes of the hubs are used to distinguish the tires with similar dimensions. Finally, a two-layered fuzzy scheme is designed to identify the tires. Experimental results show that the two-layered fuzzy scheme is more effective than the fuzzy C-means clustering algorithm. And the proposed indirect tire identification method can achieve an accuracy of above 99.9% in the assembly line of tires.

Cross coupling control design for three-dimensional contouring control system based on layered modeling method

This paper proposes a class of layered modeling and compensation method which has two advantages: the one is that coupling compensation of different layers can be done by using two-axis coupling compensation theory with the simplified coupling model; the other is that this method can adjust layered coupling strength according to control requirements. A typical three-dimensional motion control system is modeled based on the layered modeling method and the cross coupling compensation system is designed. Finally, simulations are made to verify the performance of the proposed cross coupling compensation system. The simulation results show that the proposed cross coupling system can attain higher contouring accuracy than a traditional cross coupling controller and verify that better contouring accuracy can be achieved with applied high coupling strength.