Identification &implementation of 3D of small scale helicopter control system design

Abstract

Considerable attention has been attracted to the analysis and control of helicopters due to their potential military and civil applications as well as scientific significance. In order to build a testbed for implementing newly developed linear and nonlinear control techniques, a device of 3-DOF helicopter is developed in our laboratory (Signaux et systèmes) similar to that produced by Quanser Consulting Inc. for laboratory use. Such a platform emulates the longitudinal motion of actual helicopters and presents significant similarities, in terms of dynamics and underactuation properties, with six-DOF multicopters; hence, it constitutes a prime experimental testbed and is widely used for the design of nonlinear feedback controllers. The 3-DOF laboratory helicopter consists of a base that carries a long arm capable of rotating about the elevation axis. One end of the arm is attached to a counterweight, while two bldc motors with propellers are installed at the other end to create forces that drive the propellers. Two motors’ axes are parallel, and the thrust vector is normal to the frame. Three encoders are connected to the helicopter in order to measure the elevation, pitch, and travel angles of the body, and two voltage controlling electronic speed controllers are used to realize the control action in the system. The front-and back-motor voltages are the control input of the system. Since there are more degrees of freedom than actuators, this is an under-actuated system. The 3DOF helicopter is modeled using Newton-Euler, and three equation of motions were considered. Different experimental setups were developed in our laboratory for identifying the unknown motions equations parameters. The first experiment established the bldc motor- propeller thrust force-voltage relation-ship parameters. Three other experiments are based on time-motion recorded measurement for each axis, while the others axis were fixed. Using these measurement data, the requested model parameters were generated using optimization technique with MATLAB MINUNC function. A linearized 3DOF helicopter MIMO state space model, obtained from nonlinear model, around an equilibrium point is used to design an LQR and LQG (Linear Quadratic Guassian) controllers which are simulated using SIMULINK. A 3D image (3DOF helicopter) with the LQR controller is implemented using LABVIEW, allowing real-time simulation of a 3D view of travel, yaw and elevation variations. The designed LQR controller algorithm is successfully implemented using LABVIEW to control the 3DOF platform in real-time in order to assess the controller performances and compare it with the simulated ones. The NI PCI6221 daq board is used to generate the control voltages of the front and back motors. While the three axis positions are sensed using the 1000 p/r encoders. All variable parameters, including the 3 axis helicopter variable and generated output are data-logged using developed recording functions within the developed software for complete analysis and performance evaluation