Current Issue : July - September Volume : 2015 Issue Number : 3 Articles : 5 Articles
To handle different perspectives of unstructured uncertainties, two robust control techniques on the basis of a universal model\nare studied in this paper. Rather than building a model only applicable to a specific small-scale multi rotor helicopter (MHeli),\nthe paper proposes a modeling technique to develop a universal model-framework. Particularly, it is straightforward to apply the\nuniversal model to a certain MHeli because the contribution and allocation matrix is proposed in the model-framework. Based on\nthe model uncertainties, the load perturbation of the rotor is the primary focus due to its indispensable importance in the tracking\nperformance. In contrast to the common methods, it is proposed to take this unstructured uncertainty in that external disturbance\nand designs disturbance observer (DOB). In addition, a class of lead-compensator is specifically designed as for compensating\nphase lag induced by DOB. Compared with H? loop-shaping, greater robust tracking performance on rejecting load perturbation\ncould be achieved as a trade off between robust stability and tracking performance which is successfully avoided with DOB-based\ncontrol strategy....
Space manipulators are mainly used in the spatial loading task. According to problems of the spatial loading diversity, the testing\nloading installing position, and the utilization ratio of a test platform, the space manipulator is asked to evaluate the position and\nattitude of itself. This paper proposes the Point Omnidirectional Coefficient (POC) with unit attitude sphere/circle to describe\nattitude of the end-effector, which evaluates any points in the attainable space of the manipulators, in combination with the\nmanipulation�s position message, and get relationships between its position and attitude of all points in the attainable space. It\nrepresents the mapping between sphere surface and plane for mission attitude constraints and the method for calculating volume\nof points space including attainable space, Omnidirectional space, and mission attitude space. Furthermore, the Manipulator\nOmnidirectional Coefficient based on mission or not is proposed for evaluating manipulator performance.Through analysis and\nsimulation about 3D and 2D manipulators, the results show that the above theoretical approach is feasible and the relationships\nabout link lengths, joints angles, attainable space, and Manipulator Omnidirectional Coefficient are drawn for guiding design....
Aiming at the recognition and location of non cooperative spacecraft, this paper presents a monocular vision pose measurement\nmethod based on solar triangle structure. First of all, an autonomous recognition algorithm of feature structure based on sliding\nwindow Hough transformation (SWHT) and inscribed circle of a triangle is proposed, and the image coordinates of feature points\non the triangle can be obtained relying on this algorithm, combined with the P4P algorithm and the structure of spacecraft,\ncalculating the relative pose of target expressed by rotation and translation matrix. The whole algorithm can be loaded into the\nprewritten on board program, which will get the auto complete feature structure extraction and relative pose measurement without\nhuman intervention, and this method does not need to mount any markers on the target. Then compare the measured values with\nthe accurate value of the laser tracker, so that a conclusion can be drawn that the maximum position error is lower than 5% and the\nrotation error is lower than 4%, which meets the requirements of non cooperative spacecraft�s pose measurement for observations,\ntracking, and docking in the final rendezvous phase....
This paper studies the self-organized fission control problem for flocking system. Motivated by the fission behavior of biological\nflocks, information coupling degree (ICD) is firstly designed to represent the interaction intensity between individuals. Then, from\nthe information transfer perspective, a ââ?¬Å?maximum-ICDââ?¬Â based pairwise interaction rule is proposed to realize the directional\ninformation propagation within the flock. Together with the ââ?¬Å?separation/alignment/cohesionââ?¬Â rules, a self-organized fission control\nalgorithmis established that achieves the spontaneous splitting of flocking system under conflict external stimuli. Finally, numerical\nsimulations are provided to demonstrate the effectiveness of the proposed algorithm....
We investigate the kinematic feasibility of a tendon-based flexible parallel platform actuator. Much of the research on tendondriven\nStewart platforms is devoted either to the completely restrained positioning mechanism (CRPM) or to one particular type\nof the incompletely restrained positioning mechanism (IRPM) where the external force is provided by the gravitational pull on\nthe platform such as in cable-suspended Stewart platforms. An IRPM-based platform is proposed which uses the external force\nprovided by a compliant member. The compliant central column allows the configuration to achieve n DOFs with n tendons.\nIn particular, this investigation focuses on the angular deflection of the upper platform with respect to the lower platform. The\napplication here is aimed at developing a linkable module that can be connected to one another so as to form a ââ?¬Å?snake robotââ?¬Â of\nsorts. Since locomotion takes precedence over positioning in this application, a 3-DOF Stewart platformis adopted. For an arbitrary\nangular displace of the end-effector, the corresponding length of each tendon can be determined through inverse kinematics.\nMathematical singularities are investigated using the traditional analytical method of defining the Jacobian....
Loading....