Integrated Fixed Time Sliding Mode Control for Motion and Vibration of Space Robot with Fully Flexible Base–Link–Joint

The dynamic modeling, motion control and flexible vibration active suppression of space robot under the influence of flexible base, flexible link and flexible joint are explored, and motion and vibration integrated fixed-time sliding mode control of fully flexible system is designed. The flexibility of the base and joints are equivalent to the vibration effect of linear springs and torsion springs. The flexible links are regarded as Euler–Bernoulli simply supported beams, which are analyzed by the hypothetical mode method, and the dynamic model of the fully flexible space robot is established by using the Lagrange equation. Then, the singular perturbation theory is used to decompose the model into slow subsystem including rigid motion and the link flexible vibrations, and fast subsystems including the base and the joint flexible vibrations. A fixed time sliding mode control based on hybrid trajectory is designed for the slow subsystem to ensure that the base and joints track the desired trajectory in a limited time while achieving vibration suppression on the flexible links. For the fast subsystem, linear quadratic optimal control is used to suppress the flexible vibration of the base and joints. The simulation results show that the controller proposed in the paper can make the system state converge within a fixed time, is robust to model uncertainty and external interference, and can effectively suppress the flexible vibration of the base, links, and joints.

Comparative Study of Soil Structure Interaction Analysis of Building on Clayey and Sandy Soil

Present days the analysis of structure with seismic design is more popular. because the first priority of the engineer is effective and durable structure. There are two type of base system first is rigid and second is flexible. In case of flexible base structure, only seismic analysis is not give very effective results. In this condition the SSI effect is more significant and give effective results for flexible base system. The term Soil Structure Interaction (SSI) means interaction between soil to the substructure. This effect give more accurate results after consider in the seismic analysis. If a structure is design according to the seismic analysis with SSI effect than structure could get more durability and safety against earthquake as compare to seismic analysis without SSI effect condition. So the SSI effect can change response of the seismic very significantly. The present study aim is based on seismic analysis of building with Soil Structure Interaction effect on two different soil. A frame rectangular building of G+6 storey has analyzed for flexible base simulating sand and clay soil conditions The software is used SAP2000. Raft foundation has been modeled also. Analysis is made with the response spectrum of IS 1893 2016 code. Seismic response of SSI analysis results are compare in terms of lateral storey displacement, base shear and modal behavior of natural time period on different type of soil ( clay and sand). and conclude that the lateral storey displacement, base shear and natural time period values in SSI analysis with sand soil is maximum as compare to clay soil.

Repetitive Learning Sliding Mode Stabilization Control for a Flexible-Base, Flexible-Link and Flexible-Joint Space Robot Capturing a Satellite

During the process of satellite capture by a flexible base–link–joint space robot, the base, joints, and links vibrate easily and also rotate in a disorderly manner owing to the impact torque. To address this problem, a repetitive learning sliding mode stabilization control is proposed to stabilize the system. First, the dynamic models of the fully flexible space robot and the captured satellite are established, respectively, and the impact effect is calculated according to the motion and force transfer relationships. Based on this, a dynamic model of the system after capturing is established. Subsequently, the system is decomposed into slow and fast subsystems using the singular perturbation theory. To ensure that the base attitude and the joints of the slow subsystem reach the desired trajectories, link vibrations are suppressed simultaneously, and a repetitive learning sliding mode controller based on the concept of the virtual force is designed. Moreover, a multilinear optimal controller is proposed for the fast subsystem to suppress the vibration of the base and joints. Two sub-controllers constitute the repetitive learning sliding mode stabilization control for the system. This ensures that the base attitude and joints of the system reach the desired trajectories in a limited time after capturing, obtain better control quality, and suppress the multiple flexible vibrations of the base, links and joints. Finally, the simulation results verify the effectiveness of the designed control strategy.