Slew/Translation Positioning and Swing Suppression for 4-DOF Tower Cranes With Parametric Uncertainties: Design and Hardware Experimentation

As a powerful large-scale construction tool, a tower crane is a strongly nonlinear underactuated system presenting complicated dynamical characteristics. Existing control methods for tower cranes are developed on the basis of simplified (i.e., linearized/approximated) crane dynamics, and most of them require exact model knowledge. However, practical tower cranes usually suffer from uncertainties (e.g., unknown rope length and payload mass); moreover, when the state variables are not close enough to the equilibrium point due to unexpected disturbances, simplified models might not reflect the actual dynamics any longer, which usually badly degrades the control performance. To tackle these problems, this paper proposes an adaptive control scheme for underactuated tower cranes to achieve simultaneous slew/translation positioning and swing suppression, which can reduce unexpected overshoots for the jib/trolley movements. The closed-loop stability is backed up with the rigorous mathematical analysis. To the best of our knowledge, the proposed controller is the first method for tower cranes with parametric uncertainties, which is developed without linearizing/approximating their nonlinear dynamics. Finally, we introduce our self-built multifunctional hardware crane experiment testbed and present experimental studies for the proposed method. Experimental results show that the new control approach is effective and admits satisfactory robustness.

I. Introduction

For decades, cranes have been widely utilized and play dominant roles as powerful transportation tools in many fields, which, based on their dynamical properties, can be classified into three types, i.e., tower cranes, rotary cranes, and overhead cranes [1]. Though they have different mechanical structures and working principles, the common nature they share is that there are less independent actuators than the degrees of freedom (DOFs) that need to be controlled. Hence, analogous to many mechanical systems such as nonholonomic systems [2], [3], mobile robots [4], aerial/underwater vehicles [5] –[7], wheeled pendulum robots [8] , underactuated robots [9]–[11] , moving liquid containers [12], and so on, cranes are underactuated systems whose control issues are challenging and remain open.