Frequency Response Characteristics Analysis Of Air Rudder System And Experimental Investigation

Air rudder system plays an important role in controlling the flight attitude of aircrafts. Its frequency response characteristics directly affect the rapid response of control surface. When working at high frequency, there will be a severe contact-impact phenomenon between the joint elements due to the existence of joint clearance, which can degrade control accuracy of rudder system and lead to poor frequency response characteristics. The variation of some factors, such as amplitude of control order and working load, has an important influence on the frequency response characteristics of rudder system. This research expanded the theoretical and experimental investigation of the frequency characteristics of air rudder system to study the rule of joint clearance affecting frequency response characteristics.Based on the system composition and working principle, the simulation models of rudder system are established to describe the mechanical system, electrical system and control circle using Adams and Simulink. Considering the movement and forced state of joint elements, a revolute joint clearance model is built based on the improved Coulomb Friction Theorem and contact-impact mode, which are embedded into simulation model through Adams contact subroutine. Introducing a method to redefine contact areas, which is combined with normal contact force to constraint the joint elements, to overcome the difficulty of calculating contact-impact force.A series of co-simulations of frequency characteristics about rudder system, transmission mechanism and rudder servo system are carried out based on simulation model with joint clearance, where joint clearance, amplitude of order and working load are considered. According to test condition and requires, different frequency response characteristics testing theories are analyzed and a test scheme based on frequency response analyzer is proposed. A test-bed is established based on xPC Target.For rudder system with different joint clearance state, a series of dynamic characteristics test is carried out based on the established test-bed. Compared with simulation result, the contact-impact model of revolute joint is verified through dynamic test on transmission mechanism. The test results of frequency response characteristics are analyzed and the law of revolute joint clearance affecting frequency response characteristics of rudder system is revealed, so that a technical reference is provided for rudder system design and optimization.