Underactuated crane differential flat tracking control method

The invention discloses an underactuated crane differential flat tracking control method which is characterized in that a sigmoid function is utilized to construct a novel acceleration trajectory which comprises the whole process of acceleration, constant speed and deceleration, is smooth and continuous and can meet actual physical constraints; a crane kinetic model containing load lifting is converted to obtain differential flat output equations of transverse movement and vertical movement of a load, the differential flat output equations are converted into an integral series form, and a linear expansion state observer is designed to estimate each order state and total disturbance of the transverse movement and the vertical movement of the load; and the ideal values of all-order states of the transverse and vertical movement of the load at all moments are compared with actual values or estimated values to obtain state errors, the total disturbance is compensated, and an error feedback control law of the tran