A time suboptimal method for on-orbit rapid attitude maneuver control of agile spacecraft with attitude angular velocity constraint is proposed, which can generate suboptimal control torque command for real-time application. Spacecraft time-optimal slew maneuver has been studied by many researchers, and most of the interest is focused on formulating and resolving the optimization problem of spacecraft attitude maneuver in proper ways. Pseudospectral method, among most of the existing methods, is feasible to figure out the preferred solution satisfying the control precision, which possesses the values of practical application. However, pseudospectral method consumes much time for planning attitude trajectory making it impossible for on-orbit spacecraft real-time control, especially for observation mission with frequent maneuver. After thorough analysis of the time optimal attitude maneuvering results, several patterns with respect to the generation of attitude control command are summarized that result in an interpolation control method, which is time suboptimal and is capable of on-orbit real-time application for spacecraft with small products of inertia. Closed-loop control is implemented to cancel the final pointing error. Several simulations have been performed to validate the performance of the proposed strategy, and have demonstrated the potential application for small agile spacecraft with limited attitude control ability.

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In this paper, position control is addressed for a two-joint robot finger system driven by pneumatic artificial muscles. It is hard to obtain high precision control for a two-joint robot finger system due to coupling and nonlinearities. A two-input and two-output decoupling problem is solved via active disturbance rejection control without complicated calculations. An extended state observer is designed to estimate the nonlinearities. Furthermore, the stability of the two-joint robot finger system is shown by a back-stepping method. Results from experiments are demonstrated to show the effectiveness of the proposed control approach.

A high resolution digital elevation model (DEM) enables easy derivation of subsequent information for various applications. This paper uses Real-Time Kinematic (RTK) GPS to examine the quality of some DEMs generated by such means as radar interferometry (InSAR), airborne laser scanning (ALS) and photogrammetry. The preliminary results show that a DEM generated from ALS has the highest accuracy with a RMS error of 0.09 ~ 0.3m. The RMS errors of DEMs derived by photogrammetric and radar interferometric techniques are 1.03 ~ 3.75m and 4.26 ~ 27.81m respectively.

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