| The ship (model) attitude is always needed for small ships' motion control and ship model or self-propelled model trials. According to the specific requirement for these trials, sometimes the data used to describe sway, surge and heave is also required except for attitude angles and the attitude measurement facilities are desired to install and remove momentarily. The general ship attitude measurement facilities are unsuitable for the above-mentioned situations because they are almost not only too expensive, voluminous and heave but also with complicated structure and not easy to install and remove. So, it is very significative and with better commercial value and market prospect that developing a kind of mini-type ship attitude measurement system especially for small ships' motion control and trials.Based on above reasons and background, a kind of small marine attitude measurement system based on multi-sensor technology was developed in this thesis, which is especially for small ships' motion control and trials. This system, which has many characteristics such as compact structure, small volume, light quality and also is easy to load and unload, is able to measure many kinds of ship motion parameters and satisfy the requirement for control and trials.The miniaturization and low-cost design conception was followed throughout in this thesis. A strap-down mode is applied to measure attitude parameters directly depending on several banks of sensors. The whole system is divided into hardware and software parts which measures ship motion parameters and processes data respectively. In this thesis, detailed design and produce procedure about hardware part was described including choosing sensors, designing circuit for adjusting signal, storing data, microprocessor, communication interface, and designing for human-computer interaction function and so on. It is proved by the results from real tests that hardware part can meet the requests of scheduled target.A mathematical analytic platform should be given by computer which is used to finish attitude algorithm since a strap-down mode is applied to replace complex frames in traditional systems. The proper algorithm is chosen based on the comparison among several familiar attitude algorithms for the designed system. In addition, as a result of the fact that the sensitive elements directly suffer from the dynamic condition on ship in strap-down systems, the system software must be able to make up the reliability resulting from single sensor and insure the valid measurement even though the work condition changes or some sensors are invalid or damaged because of the serious shock or vibration. Therefore, an algorithm based on the state estimation was proposed which could not only overcome the defect of traditional algorithms that rely on the statistical rules of the ship motion, but also compensate the errors resulting from the changing of sensors' sensitivity and non-linear characteristic as temperature and work condition. This algorithm isn't restricted by ship and sea-conditions and so on.For the errors resulting from assemblage in three-dimensional measurement system based on low-cost multi-sensors, a simple method which doesn't need many and good equipments was used to calibrate and align the designed system and the complete procedure was described in detail.Finally, the reasons resulting in unbounded errors were analyzed and the aiding systems composed of declinometer, speedometer and complementary filters were designed. A kind of fuzzy logic based data fusion algorithm was applied to compensate error cumulation resulting from integration. The results from the tests prove that the accurate and reliable attitude information about ship can be acquired with the help of aiding systems. |
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