Research On Space Selfrelocatingmanipulator Endeffector And Thereofcapture And Latching

The range of the self-relocating manipulator and its spatial working volume is no longer limited by the length of the manipulator arm and its permanent fixity at one end. They will spread throughout the exterior of the space module and be better for the Chinese space station construction and routine maintenance. The self-relocating manipulator has two identical end-effectors. However, the existing end-effectors cannot have large misalignment envelope, central mechanical power output and mechanism integration. The additional function needs extra device, which limits the capability of the manipulator arm. For the development of the our space robot technology, it is a promotion if an end-effector with those functions and an compliant operation method for ORU exchange are proposed.Three-finger-grasping-trefoil-fixture is proposed to make the end-effector with both large misalignment envelope and central mechanial power output. The capture mechanism is established. A driving force function between the fingers and capture mechanism is established to derive the dragging method and mechanism. A flexible element latchicng is proposed to against deficiencies of dead center or eccentricity latching and for the requirements of the system errors and deformation absorbtion. A design criterion “capture and latching functionality independence, and mechanism simplification” is proposed to make the end-effector with both large misalignment envelope and mechanism integration. With which, a corresponding relation is established to describe the mechanism, capture sequence, function and finger tracjectory. Based on which, a mid-process linking is proposed to implement the criterion, i.e. the capture finger retracts the grapple fixture after capturing it and constitutes a linkage with the static latching mechanism. A hook-shaft linking method and mechanism are established. Finally, the latching mechanism is determined by a backward derivation method based on the linkage. The grapple fixture is determined according to the corresponding function and structure.The capture misalignment is redefined according to the capture scheme. A method combining single dimensional and all(six) dimensional analyses is proposed against positional misalignment variables independence and angular misalignment variables coupling, together with four criterions. Four mathmatic models of the misalignment variable analysis in the mating surface and axial direction are established to achieve single dimensional misalignment envelope. For the motion inconsistency of capture feature space led by yaw and pitch rotation, the boundary points are constrained in the cpature finger plane intersecting with rotational surface of interface plate hemline. And they are compared with the grasping area boundary, which establishes the mathmatic models and achieve the angular misalignment envelope. The mathmatic model of single dimensional misalignment analysis provides theoretical basis for all dimensional analysis. For the later, a three-view method is proposed to achieve the boundary constraint conditions. With the boundary point rotation coordinate transformation and their three-view projection models, the slope comparison and rectangle region constraint are employed in the mating surface, the axial positional misalignment envelope and criterion 3 are employed in the capture finger planes and their normal plane through the end-effector axis, which derives the mathmatic models of the boundary constraint conditions. The simulation demonstrates that the capture misalignemnt envelope satisfies the requirements.A relation corresponding the capture and latching process to finger trajectory is established to show that the process is unrelated to the initial position and orientation of the grapple fixture. The mathmatic model of the capture process analysis is established to describe the linking relationship among the grapple fixture, capture finger and latching mechanism in the capture, dragging and mid-process linking phases. The relational models of linking cpature, linkage determination and mechanism motion are established to achieve the mid-process linking,. The mathmatic model of the latching process analysis is established to achieve the constraint relation expression of latching fingers capture and drive the grapple fixture separation and linking relationship expression of latching process. The function of the acting force on grapple fixture with the capture force and lathing force is established to demonstrate the capture and the latching functionality independence. The stiffness characteristics model of the mating surface under latching is established by bifractional analytical method and virtual material method. The mathmatic model of release process is established to secure release. The simulation demonstrates that the mathmatic model of capture and latching process relationship provides theoretical basis for the capture operation analysis of the end-effector.With the satisfaction of the environmental suitability, stiffness testing and so on, the misalignment envelope was measured by two industrial robots, the result demonstrates that it meets the requirements. The self-relocation capture and payload capture was tested on the air-bearing testbed, the result shows that the mid-process linking can definitely separate the capture and latching process and achieve the functionality independence. Based on the prototype performance testing, ORU exchange based on managing contact dynamics strategy was experimented with the establishment of the compliant contact model found on Hertz theory and Winkler elastic foundation theory, corresponding to the non-conformal contact and conformal contact, respectively. The planar contact cannot mimic the space nonlinear contact. Therefore, according to the characteristics of the capture operation process, a “slice” method was used to divide the contact into axial and radial planar contact, which can extremely retain the subset of the on-orbit contact. The results demonstrate that the ORU capture is soft with the zero force control of the manipulator and its installation is compliant with the joint impedance control.