Integrated Design With Structural And Control System For The Flexible Deployable Space Antenna

In view of the multi-nonlinear-factor influence to the smoothness and veracity ofdeployment for deployable space antennas, several key technological problems weredealt with in depth. The main works can be described as follows.1. The deformable bodies are discretized with a hypothesized displacement fieldstructured by the Rayleigh-Ritz method. The kinetic energy, geopotential energy,elasticity potential energy and the corresponding mass matrix, stiffness matrix anddamping matrix are deduced, and then the second type of Lagrange equation is used toestablish the flexible multi-body dynamic model. Via the dynamic analysis, the statevariable responding curves of the deployable antenna can be achieved. The dynamiccharacteristic and the nonlinear influence mechanism of the deployment are obtained,thus providing the foundation for control system design in latter sections.2. Bezier curves are used to synthesize the input trajectory of the driving cable.Therefore, the corresponding deployment output trajectory can be deduced from theKinetics functions of deployable antennas. The feasibility to obtain differentdeployment trajectories by altering the Bezier control points is investigated. And thenvia setting up reasonable objective function and constraint conditions, the optimaldeployment trajectory can be achieved, which can not only ensure the continuity butalso reduce the peak value of the deployment angular acceleration. Then, the inequalityconstraint, describing the constant deployment mid-period, is discussed. With numericalsimulations and comparisons, it is found that the constant deployment mid-period willlead to large impact on antennas. Therefore, the deployment should be anaccelerated-decelerated curve without constant mid-period, which will give guidance forpractical applications.3. A decoupling control method is presented for the controlled deployment offlexible deployable space antennas. In order to define the concept of the ‘mechanismeigenfrequency’, mechanism is transformed to several instantaneous structures. Viafinding the variational rules of instantaneous structure eigenfrequency with the changeof the deployment angle, the guideline for ‘critical position’, where the ‘mechanismeigenfrequency’is obtained, is proposed. A low-pass filter is used to decouple themovement feedback signal into two separate parts: the rigid movement and the vibrationcaused by flex factors. The cut-off frequency of the low-pass filter is discussed. Therigid and flex controllers are designed according to the characteristics of the decoupledfeedback respectively. And then the coupling relationship of the gain parameters between the two controllers is discussed and a guideline for the proper parameterselection is proposed based on an energy correlation analysis.4. The coupled relationship of the antenna structure, deployment trajectory, andcontrol system is discussed, and then the integrated design model is proposed. Amulti-objective function is set to simultaneously minimize the antenna mass, the impacton antenna, and the error accumulation for control system. The link cross-section areasof the antenna, the Bezier control points, and the controller gain parameters are selectedas the design variables. And with the eigenfrequency, stiffness, stability, rapidity andaccuracy constraints, the optimal integrated system design is achieved.5. A2-meter-diameter model for Astromesh cable-net deployable antenna isdesigned and built. Experimental investigation is carried out, such as structural modalanalysis, reflector surface precision, and deployment test. Based on the comparing withthe simulation and test results, the rationality of the structure and deployment analysismethod in this paper is validated. Meanwhile, based on the measurements of thecable-state in the deployment, the influence of the cable tension to the deployment isdiscussed, and then the revised deployment dynamic model is proposed.