This paper presents an improved Oriented Features from Accelerated Segment Test (FAST) and Rotated BRIEF (ORB) algorithm named ORB using three-patch and local gray difference (ORB-TPLGD). ORB takes a breakthrough in real-time aspect. However, subtle changes of the image may greatly affect its final binary description. In this paper, the feature description generation is focused. On one hand, instead of pixel patch pairs comparison method used in present ORB algorithm, a three-pixel patch group comparison method is adopted to generate the binary string. In each group, the gray value of the main patch is compared with that of the other two companion patches to determine the corresponding bit of the binary description. On the other hand, the present ORB algorithm simply uses the gray size comparison between pixel patch pairs, while ignoring the information of the gray difference value. In this paper, another binary string based on the gray difference information mentioned above is generated. Finally, the feature fusion method is adopted to combine the binary strings generated in the above two steps to generate a new feature description. Experiment results indicate that our improved ORB algorithm can achieve greater performance than ORB and some other related algorithms.

In this paper, a simple yet effective method has been raised for non-overshooting control of linear higher order plant. It is based on Posicast control, asymptotic gain scheduling and dominant pole placement by modified proportional-integral-derivative (PID) controllers, including PI-D, I-PD, PI-PD and PD-PID. The control system is composed by two closed-loops, that is, the inner loop where modified PID controllers are used to stabilize the plant by dominant pole placement, and the outer loop where asymptotic gain scheduling is used to shape the non-overshooting step response. Use of the modified PID controllers is the key to secure success of asymptotic gain scheduling, for dominance of the specified poles and phase lag dominant pole control system can be designed by these controllers in the inner loop. Three numerical examples are used to validate the method; results show that a non-overshooting control with relatively short settling time and small undershoot can be realized.

This paper mainly focuses on discussing computatio-nal method of determining whether step responses are nondecreasing for linear time invariant (LTI) systems, including negative real pole systems and complex pole systems. A modified theorem of Jayasuriya and Dharne and a useful fact are offered to deal with negative real pole systems which may have right half plane (RHP) zeros. A necessary condition is presented for complex pole systems to have non-decreasing step responses. Besides, an approximated method is further given as an improvement for determining step responses of complex pole systems.