Nonlinear Motion Control of Complicated Dual Rotary Crane Systems Without Velocity Feedback: Design, Analysis, and Hardware Experiments

As a class of underactuated systems, cooperative dual rotary crane systems (DRCSs) are widely used to complete the task of large payload transportation in complex environments, since the working capacity of single cranes is quite limited. However, the control issues of DRCS fail to receive enough attention at present. Compared with single cranes, DRCSs contain more state variables, geometric constraints, and coupling relationships. Therefore, the complex kinematic and dynamic characteristics make controller design/stability analysis very challenging for DRCS. In order to solve these problems, based on the dynamic model of DRCS established by Lagrange's method, an output feedback control method with consideration for actuator constraints is designed to realize accurate dual boom positioning and rapid elimination of payload swings. The stability of the equilibrium point for the closed-loop system is analyzed by using Lyapunov techniques and LaSalle's invariance principle. To the best of our knowledge, this article yields the first solution for effective control of DRCS, which needs no velocity feedback, respects the actuator constraints, and is designed and analyzed without linearizing the complicated nonlinear dynamic equations. Finally, a series of hardware experiments on a self-built experimental platform is carried out to illustrate the effectiveness of the proposed controller. Note to Practitioners-This article is motivated by the control problem of dual rotary boom crane systems. In order to meet industrial requirements, the masses and volumes of to-be-hoisted cargoes are larger than before, and consequently, dual-crane systems are more frequently needed to fulfill transportation tasks. For such systems, although they improve the load capacity, greater challenges are caused when eliminating cargo swings in the transportation process. To the best of our knowledge, current control methods are mainly designed based on linearized/reduced models, whose performance may be not satisfactory when swing angles are large. Moreover, most methods use velocity signals with unexpected noises and ignore the constraints of actuators' amplitudes, which may not be feasible in practical applications. To solve these problems, this article presents an output feedback controller, which can simultaneously solve the problems of saturation constraints and velocity signal unavailability. The proposed controller can guarantee accurate boom positioning and cargo swing elimination with guaranteed theoretical proof. Furthermore, the control performance is verified experimentally on a self-built testbed. In future efforts, we intend to apply the presented control method to industrial applications.