Design and control of a bending deformation actuator for hypersonic variant aircraft using shape memory alloy springs

How to effectively manage and reduce aerodynamic heating of nose cone is an important issue in hypersonic vehicle design. Active bending deformation of nose cone is an effective way of reducing extreme stagnation heat flux. Based on Shape Memory Alloy (SMA) spring, which is capable of returning to a preset shape under specific temperature conditions, an intelligent actuator for nose cone bending deformation is proposed. With this actuator, the nose cone can achieve 8° deflection deformation and real-time self-locking at any position. Mathematical models of the actuator during deformation process are derived and analyzed. The temperature of SMA springs can reach the austenite phase temperature within 3 s. To improve the autonomy controllability of bending deformation for the nose cone, a dual closed-loop control system of temperature and angle is designed. The performance of the control system is further analyzed by simulation. The results indicate that the temperature of SMA springs will not exceed 66 °C. And the bending angle of nose cone can be precisely adjusted according to the desired value. Finally, the performance of the actuator under various heating cycles and different cooling conditions is evaluated through experimental investigations. The results indicate that the demand for bending deformation of nose cone can be sufficiently met in terms of deformation amount.