This paper focuses on the position tracking control issue of electrohydraulic systems (EHS). The dynamical model of EHS is introduced in the first place, based on which a type of Variable Structure Disturbance Observer (VSDO) is constructed for EHS to estimate the parametric uncertainty the EHS possesses. Then, a backstepping controller is designed under VSDO to realize the high precision position tracking purpose. To avoid the phenomenon of differential explosion, a dynamic surface control method is adopted in this paper, which improved the position tracking control performance of EHS. The proposed theoretical results are verified by numerical simulation and experiment to illustrate the feasibility.

Rate control ensures the coded bit stream can meet channel bandwidth or storage space requirements. however, it may degrade rate-distortion (R-D) performance of encoders. Inspired by temporal dependent rate distortion optimization, this paper proposes a temporal dependency based CTU level rate control algorithm to improve R-D performance while achieving a high bitrate accuracy. First, an estimation method of CTU level R-D model is proposed to better characterize R-D relationship. Second, a formulation combining inter-CTU dependencies and R-D characteristics is constructed for CTU level bit allocation, which aims to minimize the distortion of the whole video sequence under the constraint of frame level bit budget. Finally, in the process of encoding a frame, a strict constraint of bits is used to reduce the difference between numbers of actual and target bits for the current frame. Experimental results show that, on the platform of HEVC test model (HM-16.7), the proposed algorithm achieves considerable R-D performance improvement with smaller bitrate error. Specifically, against HM-16.7 without rate control, the proposed scheme achieves bitrate savings of 4.2% and 3.7% on average under the configurations of low delay P and B frames, respectively.