With the advancing of reflectarray antenna technology, a rotational actuator is desired to enable the beam scanning capability. The anticipated characteristics of this actuator include small volume, low energy consumption, easy to control, fast response, high reliability, and etc. The actuator developed by this study is composed of bimorphs and microgears. It can rotate clockwise and counterclockwise alternately by varying the applied voltage. The most prominent advantage of this actuator is that it only requires feed forward control which is easy to implement. It doesn’t need feedback control, as other actuators do, with no accumulative errors for its positioning application. This study has optimized the geometry of this actuator using the multi-physics coupling finite element method (FEM) software. The components of this actuator have been fabricated by micro-electric-mechanical-system (MEMS) fabrication process and precise machining technology. Glass fiber reinforced composited (GFRC) and Lead Zirconium Titanate (PZT) materials are used to fabricate the bimorph. The copper and stainless steel are used to fabricate the housing and gear, respectively. Several actuators have been assembled and tested to investigate the characteristics of this actuator. A test set up has been developed to measure the relationship between the rotation angle and the applied voltage. A fast camera has been employed to experimentally assess the response time, repeatability, stability and etc. Finally, the experimental results are correlated with the analysis results.
The recent radio frequency communication system developments are generating the need for creating space antennas with lightweight and high precision. The carbon fiber reinforced composite (CFRC) materials have been used to manufacture the high precision reflector. The wave-front errors caused by fabrication and on-orbit distortion are inevitable. The adaptive CFRC reflector has received much attention to do the wave-front error correction. Due to uneven stress distribution that is introduced by actuation force and fabrication, the high order wave-front errors such as print-through error is found on the reflector surface. However, the adaptive CFRC reflector with PZT actuators basically has no control authority over the high order wave-front errors. A new design architecture assembled secondary ribs at the weak triangular surfaces is presented in this paper. The virtual experimental study of the new adaptive CFRC reflector has conducted. The controllability of the original adaptive CFRC reflector and the new adaptive CFRC reflector with secondary ribs are investigated. The virtual experimental investigation shows that the new adaptive CFRC reflector is feasible and efficient to diminish the high order wave-front error.
The novel linear actuator is researched with light weight, small volume, low power consumption, fast response and relatively large displacement output. It can be used for the net surface control of large deployable mesh antennas, the tension precise adjustment of the controlled cable in the tension and tensile truss structure and many other applications. The structure and the geometry parameters are designed and analysed by finite element method in multi-physics coupling. Meantime, the relationship between input voltage and displacement output is computed, and the strength check is completed according to the stress distribution. Carbon fiber reinforced composite (CFRC), glass fiber reinforced composited (GFRC), and Lead Zirconium Titanate (PZT) materials are used to fabricate the actuator by using laser etching and others MEMS process. The displacement output is measured by the laser displacement sensor device at the input voltage range of DC0-180V. The response time is obtained by oscilloscope at the arbitrarily voltage in the above range. The nominal force output is measured by the PTR-1101 mechanics setup. Finally, the computed and test results are compared and analysed.
The trend in future space high precision reflectors is going towards large aperture, lightweight and actively controlled
deformable antennas. An adaptive shape control system for a Carbon Fiber Reinforced Composite (CFRC) reflector is
conducted by Piezoelectric Ceramic Transducer (PZT) actuators. This adaptive shape control system has been shown to
effectively mitigate common low order wave-front error, but it is inevitably plagued by high order wave-front error
control. In order to improve the controllability of the adaptive CFRC reflector control system for high order wave-front
error, the design of adaptive CFRC reflector requires optimizing further. According to numerical and experimental
results, the print-through error induced by manufacturing and PZT actuators actuation is a type of predominant high
order wave-front error. This paper describes a design which some secondary rib elements are embedded within the
triangular cells of the primary ribs. These small secondary ribs are designed to support the reflector surface’s weak
region. Controllability of this new adaptive CFRC reflector control system with small secondary ribs is evaluated by
generalized Zernike functions. This new design scheme can reduce high order residual error and suppress the high order
wave-front error such as print-through error. Finally, design parameters of the adaptive CFRC reflector control system
with small secondary ribs, such as primary rib height, secondary rib height, cut-out height of primary rib, are optimized.
An adaptive control system for correcting wave-front error of a CFRC reflector has been studied. Errors investigated in this paper were mainly introduced by fabrication and gravity. 72 Piezoelectric Ceramic Transducer (PZT) actuators were integrated to the CFRC reflector to conduct wave-front error control. The adaptive CFRC reflector was fixed on an optical platform without any external loads. The temperature and humidity were well controlled during the experimental study. The wave-front error correction algorithm is based on influence matrix approach coupled with least squares optimization method. The linear relationship between the PZT actuator’s input voltage and the output displacement of the adaptive CFRC reflector surface is validated. A laser displacement sensor was used for measuring the displacements. The influence matrix was obtained experimentally by measuring the displacements of the associated points while each actuator was activated separately. The wave-front error and influence matrix were measured using a V-Stars photogrammetry system. Experimental investigation validated that this adaptive control system is capable to significantly reduce the reflector surface geometry error. Experimental results are correlated very well with simulation results which were obtained by using a multidisciplinary analytical approach. Conclusions of this study suggest that the adaptive CFRC reflector technology can provide a low cost method to significantly increase the precision of a CFRC reflector.
Maintaining geometrical high precision for a graphite fiber reinforced composite (GFRC) reflector is a challenging task. Although great efforts have been placed to improve the fabrication precision, geometry adaptive control for a reflector is becoming more and more necessary. This paper studied geometry adaptive control for a GFRC reflector with piezoelectric ceramic transducer (PZT) actuators assembled on the ribs. In order to model the piezoelectric effect in finite element analysis (FEA), a thermal analogy was used in which the temperature was applied to simulate the actuation voltage, and the piezoelectric constant was mimicked by a Coefficient of Thermal Expansion (CTE). PZT actuator’s equivalent model was validated by an experiment. The deformations of a triangular GFRC specimen with three PZT actuators were also measured experimentally and compared with that of simulation. This study developed a multidisciplinary analytical model, which includes the composite structure, thermal, thermal deformation and control system, to perform an optimization analysis and design for the adaptive GFRC reflector by considering the free vibration, gravity deformation and geometry controllability.