[Abstract] In the past decades, Synthetic Aperture Radar (SAR) antennas have attracted much attention for its advantages over other optical based antennas in earth observation because of their all-weather and daylight independent capabilities. The large size membrane SAR antennas has the advantages of achieving large gain and good resolution with ultra light mass. In this paper, we have developed a foldable deployable structure to deploy a membrane antenna in two directions, longitudinal and lateral directions. The longitudinal deployment is driven by two symmetrically arranged deployable structures. Each of them has a six-bar linkage mechanism and two closed-cable-loops. Several motion controllable hinges fulfill the lateral deployment. The hinge is composed of a SMA actuator, tape springs and a motion control mechanism. In this paper, the six-bar linkage has been designed with an optimal method to meet the demand of simultaneous deployment of all frames and keeping in a common plane after they are fully deployed. To analyze the dynamic performance of the driving mechanism, the multibody dynamic analysis software ADAMS has been used. For large size antennas, the effect of the frame flexibility on the dynamic performance of the system cannot be ignored. Using ADAMS/Flex, we studied the effect of frame flexibility on the dynamic properties of the support structure. Also, the natural frequencies and mode shapes of the deployed structure have been analyzed using finite element method. In this paper, the structure of the motion controllable hinge is introduced and the relationship between the joint output torque with respect to its parameters is studied.
This work presents the current mechanical prototype of a SAR membrane antenna being tested at the Canadian Space Agency. The current concept of the C-Band membrane antenna calls for a 4 m by 10 m membrane, a wing of that antenna measuring 4 m by 5 m. The prototype measures 2 m by 3 m, which is slightly longer than a half-scale prototype of one wing. This prototype will be fully representative of the mechanical concept of the CBand membrane antenna. The three horizontal layers, with the vertical layers embedded, are flattened one on top of the other for stowage. When deployed, the bottom layer and the top layer are separated by approximately 15 cm. A mechanism has been devised to tension the membranes and deploy them. Each side of the spacecraft has a frame made of struts and the deployment is activated from a single six-bar linkage mechanism. The hinges are made of spring tapes, guiding devices, and a shape memory alloy. The current state of the integration of the frame is reported here, as well as the tests done to assess the performance of the tensioning scheme of the membrane.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
