Research On Load Swing Suppression Of Quadrotor Suspension System

Recently,the quad-rotor has been widely used in military,civil and entertainment fields because of its small size,strong mobility,simple structure and high security.It can also realize special functions such as vertical take-off and landing,fixed-point hovering and so on.One of the most popular application is unmanned aerial vehicles(UAV)delivery.Traditional transportation mode are inside the fuselage and outside the fuselage with a box.Besides,there is another transportation mode is hanging transportation.A rope with one terminal attached to the bottom of a quad-rotor aircraft,the other one to a transport box or suspended load.Compared with traditional transportation mode,hanging transportation can carry heavier loads.Taking advantages of the quad-rotor vertical take-off and landing,fixed-point hovering.Through quadrotor drop the load in fixed point,it can carry out the next task quickly without landing.And in this way,the efficiency of transportation is improved.However,the movement of quad-rotor and external disturbances such as the wind will cause the load produce vibration during the flight.When the transportation of quadrotor with a slung load reaches the destination,the quad-rotor is required to stop immediately.It may even cause the quad-rotor lose control and thus crash,and slow deceleration will take a long time to stabilize the vibration of the suspended load.Therefore,it is necessary to improve the safety and efficiency of transportation by suppressing the load vibration when during flight.Following are the main contents discussed in this paper.1)The dynamic model of the quadrotor suspension system is presented.The dynamic model of the quadrotor suspension system is established by Lagrange dynamics.The model is composed of the motion of the quadrotor and the load vibration.Considering the coupling relationship between the quadrotor and the load,the nonlinear mathematical model is established.According to the PD control and the function of filter,the corresponding position controller and attitude controller are designed to track the trajectory of the target point.Finally,the advantages and disadvantages of the two methods are compared.2)The vibration of suspended load during flight is regarded as the external disturbance of the system.The closed-loop feedback system is designed to reduce the disturbance under the theory of exact linearization.The mathematical model is expressed by the state space formula.In this paper,the original state system is divided into quadrotor tracking parts with excitation directly and the load swing suppression part with excitation indirectly.The suspended part is approximately linearized under the theory of small disturbance theory.Then,the range of the controller's gain parameters are obtained based on the Routh criterion.The gain parameters are selected reasonably by synthesizing the time taken by the vibration angle to reach the balance point and the vibration amplitude.It makes the controller have the better effect on the vibration suppression of the quadrotor suspension system.3)Suspended load is regarded as a new degree of freedom.According to the dynamic equation of suspended load,the input shaping controller is designed based on the natural frequency and damping ratio.The input shaping technology belongs to one kind of active control.The vibration of the suspended load in flight can reach the equilibrium state by a smaller amplitude and faster.