Potential Function Guidance Method for Extraterrestrial Body Landing Based on Trajectory Curvature Adjustment

This paper presents a variable hierarchy six degree of freedom non-linear sliding mode controller for a satellite using potential function guidance for both position and attitude. The novelty is the formulation of the joint attitude/position sliding mode controller in combination with potential function guidance and proof of its asymptotic stability. The control method scales well to multiple satellites flying in formation with dynamic position and attitude requirements and as such is highly relevant to application in space systems such as interferometry. A target application of the acquisition and maintenance of a Halo type orbit about an unstable collinear Lagrange point, to a specified attitude, is obtained under the influence of the restricted three body dynamics.

Trajectory planning of a free-floating dual-arm space robot with minimal base disturbance in obstacle environments

Rigid-body guidance synthesis of linkages must satisfy the requirements of position and posture simultaneously, which increases the difficulty of dimensional synthesis. Extraction of harmonic characteristic parameters via a Fourier series to describe the output motion of the linkage, followed by rigid-body guidance synthesis, is a simple and efficient approach. However, current research on this method has focused mainly on four-bar linkages and simple spherical and spatial mechanisms. There is less research on six-bar linkages, primarily due to the large number of design parameters, the complexity of the motion output, and the difficulty of dimensional synthesis. This article establishes a reduced-dimension optimization synthesis method for rigid-body guidance of the Stephenson-III six-bar linkage on the basis of Fourier harmonic characteristics. The optimization variables do not include the installation dimensions, allowing for the optimization space to be reduced by four dimensions, thereby reducing the optimization complexity. Constraints such as the link length nonnegativity condition, the crank existence condition, the transmission angle condition, and the link length ratio condition are established to ensure the feasibility of the final solution. Finally, on the basis of the task poses at the human ankle joint, a single-degree-of-freedom (DOF) end-traction Stephenson-III six-bar gait rehabilitation training mechanism was synthesized and designed via the proposed rigid-body guidance synthesis method. The trajectory and posture angle curves generated by the prototype experiment were essentially consistent with the theoretical design, verifying the correctness of the theoretical design method and manufacturing assembly as well as the feasibility of the rehabilitation training program.

Virtual-Target-Based trajectory following using a light-of-sight angle constraint for long-range guided projectiles