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Aimed at the joint vibration problem caused by the load change of humanoid flexible joint, a torque compensation control method based on state observer is proposed. By controlling the motor to output a torque increment equivalent to the disturbance torque, the joint torque can quickly balance the load torque and shorten the oscillation process of the elastic element passively adapting to the load change. A state observer for estimating load disturbance torque and motor speed is designed, whose convergence is proved by the Lyapunov function. The control structure of the drive system based on the proportional integral-intergral proportional (PI-IP) speed regulator is established, and the observer output feedforward link is added to the speed regulator to improve the anti-interference ability of the system. The simulation results show that compared with proportional integral differential (PID) control and joint force feedback proportional differential (PD) control, the proposed method can restore the motor speed to stability within 0.6 s after load change and realize joint vibration suppression within 1 s. Besides, the joint speed adjustment time is shortened by about 1.8 s and 0.9 s respectively, which effectively improves the dynamic adjustment ability of the system. Finally, the effectiveness of the proposed method was verified by experiments on an integrated flexible joint testing platform.

In this paper, the generation method of the medial axis in the arbitrary quadrilateral surface is proposed. It can provide a solution for the simplification of the complex fillet feature and the generation of the mesh in the model. By using the locus method associated with moving Frenet frame, we realize the simple and fast algorithm for generating the medial axis. As for the engineering problem, B-rep 3D solid models with clear boundary definition are mostly applied; the information of vertex, side and surface of the model, which is clearly stored in the model file, can be used to simplify the traditional locus method for generating the medial axis, in order to reduce the amount of data required by the generation. In this paper, we use the clear boundary information in the B-rep model as the condition for generating the medial axis and the characteristics of the bisector to eliminate the calculation of the branch points, reducing the factors affecting the accuracy of the medial axis. In order to ensure the accuracy of the medial axis, the density of the insertion points can be used for control.

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Objective With the rapid development of spectral imaging technology in recent years, hyperspectral remote sensing images can provide abundant data on surface features. However, the sizable data of hyperspectral images make their storage, transmittal, and application quite difficult. As a result, how to validly code hyperspectral images has become a hot issue. Method The distributed source coding based on coset codes has received much attention because of its good compression performance and low coding complexity. In this study, we present a scheme for lossless distributed source coding of hyperspectral images based on adaptive quadtree segmentation. Assuming that the first frame in every group of spectrum frames is the key frame, the other frames are Wyner-Ziv frames. First, we perform adaptive quadtree segmentation on the key frame and then optimum linear prediction on each block of each Wyner-Ziv frame. Afterwards, the index of the coset codes to be transferred and the k least significant bits of every pixel in this block are ascertained using prediction residuals. Result In this study, adaptive quadtree segmentation scheme has been proved to strengthen the adaptability of the formed coset codes. The proposed scheme can achieve a good compromise between coding efficiency and calculating complexity. Conclusion This scheme is better able to meet the lossless coding requirement for hyperspectral images under low-complexity environment. [ABSTRACT FROM AUTHOR]