An Overview of Research in Distributed Attitude Coordination Control

This paper provides an overview of attitude coordination problems of multi-rigid-body with the goal of promoting research in this area. Theoretical results regarding consensus seeking with different system models, different communication topologies, different control goals and different techniques are summarized. And applications of consensus protocols to multirigid-body coordination are investigated. Finally, some future research directions and open problems are also proposed.

Attitude Coordination of Multi-HUG Formation Based on Multibody System Theory

Application of multiple hybrid underwater gliders （HUGs） is a promising method for large scale, long-term ocean survey. Attitude coordination has become a requisite for task execution of multi-HUG formation. In this paper, a multibody model is presented for attitude coordination among agents in the HUG formation. The HUG formation is regarded as a multi-rigid body system. The interaction between agents in the formation is described by artificial potential field （APF） approach. Attitude control torque is composed of a conservative torque generated by orientation potential field and a dissipative term related with angular velocity. Dynamic modeling of the multibody system is presented to analyze the dynamic process of the HUG formation. Numerical calculation is carried out to simulate attitude synchronization with two kinds of formation topologies. Results show that attitude synchronization can be fulfilled based on the multibody method described in this paper. It is also indicated that different topologies affect attitude control quality with respect to energy consumption and adjusting time. Low level topology should be adopted during formation control scheme design to achieve a better control effect.

Attitude coordination for spacecraft formation with multiple communication delays

Communication delays are inherently present in information exchange between space- craft and have an effect on the control performance of spacecraft formation. In this work, attitude coordination control of spacecraft formation is addressed, which is in the presence of multiple communication delays between spacecraft. Virtual system-based approach is utilized in case that a constant reference attitude is available to only a part of the spacecraft. The feedback from the virtual systems to the spacecraft formation is introduced to maintain the formation. Using backstepping control method, input torque of each spacecraft is designed such that the attitude of each spacecraft converges asymptotically to the states of its corresponding virtual system. Furthermore, the back- stepping technique and the Lyapunov-Krasovskii method contribute to the control law design when the reference attitude is time-varying and can be obtained by each spacecraft. Finally, effectiveness of the proposed methodology is illustrated by the numerical simulations of a spacecraft formation.

Disturbance observer based finite-time coordinated attitude tracking control for spacecraft on SO(3)

To solve the problem of attitude synchronization control for spacecraft formation flying(SFF)suffering from external disturbances under a directed communication topology,a sliding mode disturbance observer(SMDO)based on the finite-time control strategy is developed to observe the time-varying external disturbance via estimating the upper bound of its first derivative.Meanwhile,the rotation matrix is employed to describe the attitude of SFF for the purpose of the avoidance of singularity and unwinding phenomenon.As for the attitude synchronization and the tracking control architecture,a sliding mode surface(SMS)is given such that the control objective can be achieved.The effectiveness and the validity of the proposed method are elaborated via theoretical analysis and numerical simulations.

Evaluating the Relationship between National Park Management and Local Communities’ Perceptions Based on Survey, a Case of Nyungwe National Park, Rwanda

A sustainable management of national park requires collaboration between park staff, NGOs, local organizations and stakeholders, and government intervention. This collaboration promotes community-based welfare and inspires a sense of responsibility, thus promoting more benefits than conflicts. A survey administered to residents surrounding Nyungwe National Park was used to evaluate the relationship between Nyungwe National Park management and local communities. The residents acknowledged a positive attitude towards participating in conservation organizations where there was involvement, while a negative response revealed weak community mobilization. The community’s opinions about protection and tourism progression noted weak conflict resolution, but a positive attitude towards tourism activities in the area since they believed employment was likely as a result. In addition, the residents asked for support from government investments and stakeholders to develop the local private sector, and asked to be involved during the planning process. Approaches including the design of coordination mechanisms and integrated conservation and developments projects are suggested to promote a management structure leading to community involvement in conservation and tourism activities. This will increase visitor numbers and contribute to economic development not only in the region but also in the whole country. Empirical studies along with the factors shaping tourism and conservation activities should be considered as the basis for sustainable decision and policy making for sustainable management, and will contribute to government, stakeholders and park manager collaborations at Nyungwe national park.

Three-dimensional analysis of relationship between relative orientation and motion modes

Target motion modes have a close relationship with the relative orientation of missile-totarget in three-dimensional highly maneuvering target interception. From the perspective of relationship between the sensor coordinate system and the target body coordinate system, a basic model of sensor is stated and the definition of relative angular velocity between the two coordinate systems is introduced firstly. Then, the three-dimensional analytic expressions of relative angular velocity for different motion modes are derived and simplified by analyzing the influences of target centroid motion, rotation around centroid and relative motion. Finally, the relationships of the relative angular velocity directions and values with motion modes are discussed. Simulation results validate the rationality of the theoretical analysis. It is demonstrated that there are significant differences of the relative orientation in different motion modes which include luxuriant information about motion modes. The conclusions are significant for the research of motion mode identification,maneuver detection, maneuvering target tracking and interception using target signatures.