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To reduce the grinding trajectory deviation caused by the absolute positioning accuracy of robot, a trajectory compensation method based on Co-Kriging space interpolation method is proposed. Meanwhile, an adaptive iterative constant force control method based on one-dimensional force sensor is proposed to improve the processing quality and efficiency of robot belt grinding. Firstly, an error model based on 6 DOF robot is constructed. Then, considering the workspace of robot belt grinding and the similarity of robot position error, the Co-Kriging compensation algorithm is used to compensate the grinding trajectory, which makes the compensation process convenient and accurate. Then, a grinding dynamics model based on deformation is established, and an adaptive iterative constant force control is proposed for complex robot belt grinding process, which overcomes the instability of grinding force and shortens its convergence time. Finally, the grinding trajectory compensation experiment and the force control experiment of spherical workpiece are carried out. The results show that the space interpolation compensation algorithm based on Co-Kriging method can significantly improve both the space position error of grinding trajectory and the actual error of workpiece, which proves the feasibility of compensation algorithm. Through force control algorithm, the grinding force fluctuation is maintained within 2 N, the mean value, standard deviation and variance of absolute value of force error are significantly reduced, the convergence rate of grinding force and the roughness of workpiece are much better than before, which shows the effectiveness of the proposed force control algorithm.

Three new homo-adamantanyl type natural products were derived from polyprenylated polycyclic acylphloroglucinol. Hypercohones A-C (1–3), along with five other known hypercohones (4–8), were isolated from the aerial parts of Hypericum cohaerens. The structures of 1–3 were elucidated on the basis of comprehensive spectroscopic analysis. The inhibitory activities of these isolates against five human cancer cell lines in vitro were tested. Electronic Supplementary Material Supplementary material is available for this article at 10.1007/s13659-013-0032-9 and is accessible for authorized users.

In this paper, a composite control scheme for macro-micro dual-drive positioning stage with high acceleration and high precision is proposed. The objective of control is to improve the precision by reducing the influence of system vibration and external noise. The positioning stage is composed of voice coil motor (VCM) as macro driver and piezoelectric actuator (PEA) as micro driver. The precision of the macro drive positioning stage is improved by the combined PID control with adaptive Kalman filter (AKF). AKF is used to compensate VCM vibration (as the virtual noise) and the external noise. The control scheme of the micro drive positioning stage is presented as the integrated one with PID and intelligent adaptive inverse control approach to compensate the positioning error caused by macro drive positioning stage. A dynamic recurrent neural networks (DRNN) based inverse control approach is proposed to offset the hysteresis nonlinearity of PEA. Simulations show the positioning precision of macro-micro dual-drive stage is clearly improved via the proposed control scheme.

A new cucurbitacin, endecaphyllacin C, was isolated from the tubers of Hemsleya endecaphylla. The structure was elucidated as 2β,16α,20β,25-tetrahydroxy-24-acetylaminocucurbita-5-en-3,11,22-trione (1) on the basis of extensive 1D and 2D NMR techniques, including COSY, HMBC, HMQC, and NOESY correlations, as well as HR-FAB-MS analysis.