Research On Modeling And Corrdinated Turn Control For Small-Size Unmanned Helicopter

Small-size unmanned helicopter (SUH) has great advantages of small size, light weight, low cost, good stealthiness, no casualties and so on, it also can vertical take-off and landing, low altitude flight, rearward flight, sideward flight, coordinated-turn flight, hovering etc.These advantages make SUH has great application value in both military and civilian fields. SUH is a highly non-linear, strong coupled, time-varying open-loop unstable system, posting a great challenge to modeling and flight control.In this paper, "Wings of Yuquan" SUH is the main research object. The hardware and software platform of flight control system is built; the 11-order model is established and parameters are obtained by system identification; flight control strategy of coordinated turn is also proposed,and autonomous coordinated-turn flight experiment is conduct; a controller is designed based on the H-infinity loop shaping theory to improve the tracking performance of the inner loop. The main work and contributions of this paper are as follows:1) According to the needs, to build a set of flight controls for SUH experimental platform, including hardware platform, software platform and simulation platform. The platform has enough computing power, strong real-time, reliable, and easy to expand and other properties.2) Integrated 5 key parts which generate forces and moments of SUH to get their equations of motion, small perturbation linearization method is applied to get its 11-order state-space equation. Data is collected by sweep experiment, parameters is obtained by system identification and the reliability of the model built by the frequency domain validation.3) After analyzed the dynamics of coordinated turn, a control strategy of coordinated turn is proposed, a cascade PID controller is designed, through flight testing, optimize the parameters, improved control scheme, and finally achieve a complete coordinated turn flight experiment. The flight data indicates that the performance of coordinated turn works well:attitude is stable, velocity errors are within ±0.5m/s, height remains relatively stable in the range of error of ±1.2m, horizontal curves approximate a circle and XY position errors within 8%.The results verify that the designed controller is reliable, can be realized in engineering and have a good robustness and dynamic performance.4) Based on the H-infinity loop shaping theory, a robust inner controller is designed for the SUH model, the dimension of the controller is reduced from 16-order to 7-order, and finally verify the controller’s robust by the model under different forward speed. Simulation results show that:the inner loop of each channel has a good tracking speed, steady-state error and overshoot is small, excellent decoupling performance between the channels, the controller still has good control effect within forward speed of 8m/s.