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.

An Effective Approach to Model Parallel Robots With Flexible Links

This paper is focused on the development of an effective hardware and software architecture that is useful to improve the performance of slender parallel manipulators. The latter can perform high acceleration in fast pick and place applications, but their features can be also exploited in more advanced operations, where path following is a central issue. A simple and effective approach to model the elastodynamic behavior of flexible parallel manipulator is proposed, conceived to be fast and easy to implement in model-based control schemes. Moreover, a workbench architecture based on camera acquisitions is essential to calibrate the elastodynamic model and provide all the required information that are needed to improve path following of flexible mechanims.

Introduction: Ecologising Taiwan

Ecologising Taiwan means to think ecologically about, from, as well as by way of Taiwan. On the one hand, we ecologise Taiwan by viewing it through an ecological perspective; on the other hand, we also want to treat Taiwan itself as an agent that drives our thinking, no longer merely an object of our anthropocentric and anthropocenic gaze. Taiwan, as an island that encompasses a particularly wide range of biotopes, redefines insularity in its connectivity to other global spaces and networks: it pits its infinite potential for different encounters, relations, and comparisons against any bias of smallness and isolation. Culturally specific representations—the stories we tell about the environment and how we tell them—are important in environmental thinking. Thus ecologising Taiwan is not only about what ecological thinking can do for Taiwan but also about what Taiwan can do for ecological thought. In order to sound out the different resonances of what ecologising Taiwan might mean, this special issue brings together six essays that explore flexible links between ecological thought and Taiwanese culture. As such, this special issue is part of the ecological chain of Taiwan studies, featuring topics (even topoi) on languages, genres, media forms, and methodologies in contestation and transformation.