Tham khảo tài liệu 'advances in flight control systems part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Adaptive Fight Control Actuators and Mechanisms for Missiles Munitions and Uninhabited Aerial Vehicles UAVs 7 Fig. 5. Tip-Joint Flexspar Fin Geometric Parameters If one examinies the basic construction of a piezoelectric bender element then a simple expression can be laid out which relates laminate curvature k to cure parameters material characteristics and active free strain levels of the actuator L. As has been shown over the past 20 years it is important to use thermally induced precompression in all flightworthy adaptive aerostructures as shown in Equation 3. Equation 4 is the solution of the bending curvature considering a symmetric balanced laminate composed of two sheets of CAP actuator material bonded on either side of an uncoupled substrate. By using the geometry of Figure 5 the curvatures commanded can be translated into control surface deflections d. Of course these estimations assume a frictionless balanced system operating without geometric binding which typically set in on real systems for rotation angles in excess of 15 . rA11 A12 0 1 m A11 A 0 1 at L 0 D11 D12J lamVj L 0 D11 D12 Ja 0 3 A11 A12 D11 J m b11 B12 1Ũ 12 a Ea tsta 2tbta 12y Í ts 2tb 2ta ts 2tb 2 K 4 s 2 sin-1 xc - cos Klo lotot - y o 2 5 These expressions have been regularly used for more than a decade to predict Flexspar actuator deflection levels with experimental and predicted results typically within 5 of each B11 Ja 2 8 Advances in Flight Control Systems Fig. 6. Typical Flexspar Deflection s and Correlation Levels17 The Flexspar actuator configuration is still to this day one of the more well used actuation schemes for flight control. It comes in two major variants the Tip-Joint Flexspar arrangement as shown in Fig. 5. This configuration is particularly well suited to low subsonic flight control using symmetric balanced aerodynamic surfaces. A high moment configuration called a Shell-Joint Flexspar actuator is used for high subsonic and faster control surfaces. In the .
