جستجوی مقالات مرتبط با کلیدواژه « تعیین وضعیت ماهواره » در نشریات گروه « مکانیک »

Simulating environmental conditions for the satellite attitude sensors is a fundamental requirement of hardware in the loop tests of attitude determination and control subsystem. In this paper, a new design for simulating sun vector and magnetic vector is presented. The operating environment for attitude sensors is simulated using a sun simulator, a two-degree-of-freedom table for changing the attitude of the sun sensor, and a three-axis Helmholtz coil. The sensors measurements showed that with this setup, the sun and magnetic vectors can be created with an acceptable accuracy using the orbital position and the attitude of the satellite. So, the test bed can be used for attitude determination of hardware in the loop tests.

Attitude Determining is one of the major and critical satellites space missions. In this study, a new method to Attitude determination of satellites is presented. Such that, based on the proposed method search space will be more limited then accuracy and speed of attitude determination in the proposed method has risen. At first in this method, implementation and the test algorithms will be discussed, after these some algorithms, such as navigation, pattern recognition and ultimately attitude determination will be reviewed. In order to implement these algorithm. High quality images of stars which must provided by the star tracker camera requires to implement. Really these images to perform the necessary processing sent to the processor so the processor based on designed algorithms, determines the attitude of camera and satellite in all three axes. This means that some features considered for star tracker and based on them begins the designing process. The range of accurately determination for star tracker is one of these features. In this article, the ranges of two axes of Yao and Pitch less than 20 seconds on the scale of degree are considered and in the roll axis less than 100 seconds is intended. Can show in the results, much better accuracy and less than initial assumptions have been achieved. It also carried out by an adaptive identified algorithm so that the brighter stars are identified and based on their attitude determination, the sensor accuracy have increased. Because of according research, the clearer stars, have more accurate in calculation. The other important feature is the speed of attitude detection which performed by 1 GHz processor, and correct identification of pyramidal algorithm where have reached less than 15 milliseconds. Due to the duration, the desire update rate gained. Other important parameters which influence the accuracy of the attitude determination is knowing the exact coordinates of the intersection point vector of focal length lens with image sensors. By Land calibration for camera with a good accuracy, these parameters were estimated.

Evaluation of the satellite attitude determination system is very complicate because of need to simulate space environment on the ground. In this paper a laboratory Implementation of attitude estimation using sun sensor and magnetometer is reported.The test setup includes a sun simulator installed in a dark room. The magnetometer measures the local magnetic field. Sensors are rotated using a 2 DOF table. The reference models are adapted with the test setup. Attitude determination using classic and extended kalman filter methods is implemented by sensors data fusion. The test results verify the controlled motion of sensors in the limits of setup accuracy order.