Control strategies for crane systems: A comprehensive review

As a type of indispensable oceanic transportation tools, ship-mounted crane systems are widely employed to transport cargoes and containers on vessels due to their extraordinary flexibility. However, various working requirements and the oceanic environment may cause some uncertain and unfavorable factors for ship-mounted crane control. In particular, to accomplish different control tasks, some plant parameters (e.g., boom lengths, payload masses, and so on) frequently change; hence, most existing model-based controllers cannot ensure satisfactory control performance any longer. For example, inaccurate gravity compensation may result in positioning errors. Additionally, due to ship roll motions caused by sea waves, residual payload swing generally exists, which may result in safety risks in practice. To solve the above-mentioned issues, this paper designs a neural network-based adaptive control method that can provide effective control for both actuated and unactuated state variables based on the original nonlinear ship-mounted crane dynamics without any linearizing operations. In particular, the proposed update law availably compensates parameter/structure uncertainties for ship-mounted crane systems. Based on a 2-D sliding surface, the boom and rope can arrive at their preset positions in finite time, and the payload swing can be completely suppressed. Furthermore, the problem of nonlinear input dead zones is also taken into account. The stability of the equilibrium point of all state variables in ship-mounted crane systems is theoretically proven by a rigorous Lyapunov-based analysis. The hardware experimental results verify the practicability and robustness of the presented control approach.

Neural Network-Based Adaptive Antiswing Control of an Underactuated Ship-Mounted Crane With Roll Motions and Input Dead Zones

This paper studies an adaptive fuzzy tracking control problem for nonlinear stochastic systems with input saturation and nonstrict-feedback form. We use fuzzy logic systems to approximate unknown nonlinear functions. A novel approach is introduced to tackle unknown functions with nonstrict-feedback structure in the design process. By introducing an auxiliary system, the input saturation problem can be solved. Moreover, based on backstepping control design approach, a novel adaptive fuzzy tracking controller is designed to guarantee all signals in the closed-loop system to be bounded, and the system output can be driven to track the trajectory of a given reference signal. Finally, some simulation results are given to confirm the effectiveness of the proposed approach.

Adaptive Fuzzy Control of Stochastic Nonstrict-Feedback Nonlinear Systems With Input Saturation

When modeling cranes, the hook and the suspended cargo are usually regarded roughly as one mass point for simplicity, ie, the cargo swing is modeled as that of a single pendulum However, in practice, when the hook mass is nonnegligible or the cargo has a large size, the crane always exhibits double-pendulum swing dynamics, which is much more complicated and makes most existing control methods unapplicable In addition, all existing closed-loop controllers for (double-pendulum) cranes require full state feedback, while velocities are unavailable in most cases Moreover, they need to linearize the nonlinear crane model and cannot respect the actuator's practical saturation constraint, which may probably lead to actuator saturation and badly degrade the control performance (even unstable) In response to these practical issues, we suggest a novel amplitude-saturated output feedback (OFB) control approach for underactuated crane systems exhibiting double-pendulum effects We provide explicit Lyapunov-based analysis to rigorously prove that the equilibrium point of the closed-loop system is almost globally asymptotically stable, without any approximation to the original nonlinear dynamics As far as we know, this paper presents the first closed-loop control method that can achieve control for an underactuated double-pendulum crane with merely OFB and theoretically-guaranteed saturated control efforts Hardware experimental results demonstrate the superior performance of the proposed approach over existing methods and its strong robustness as well

Amplitude-Saturated Nonlinear Output Feedback Antiswing Control for Underactuated Cranes With Double-Pendulum Cargo Dynamics

This paper focuses on an observer-based adaptive fuzzy control problem for nonstrict-feedback stochastic nonlinear systems with input saturation and prescribed performance. By introducing a mean-value theorem, the obstacle arising from input saturation is overcome. The transient performance of system output is also achieved by means of designing performance function. On the other hand, a variable separation method is used to deal with the difficulty caused by nonstrict-feedback structure. Additionally, fuzzy logic systems are introduced to approximate unknown nonlinear functions. Moreover, an observer is constructed to estimate unknown state variables in the systems. By combining adaptive backstepping control method, an observer-based adaptive fuzzy controller is designed to ensure all signals of the resulting closed-loop system to be bounded, and the output of the system converge to a prescribed area. Finally, two examples are given to show the effectiveness of the proposed control scheme.

Prescribed Performance Observer-Based Adaptive Fuzzy Control for Nonstrict-Feedback Stochastic Nonlinear Systems

Presently, ship-mounted cranes are playing more and more important roles in modern ocean transportation and logistics Different from traditional land-fixed crane systems, ship-mounted cranes present much more complicated nonlinear dynamical characteristics and they are persistently influenced by different mismatched disturbances due to harsh sea environments, eg, sea waves, ocean currents, sea winds, and so forth; these unfavorable factors bring about many challenges for the development of effective control schemes This paper presents a novel nonlinear stabilizing control strategy for underactuated ship-mounted crane systems Specifically, some novel coordinate change procedures are first introduced to tackle the disturbing terms by transforming the original dynamics into a new form, which facilitates both controller design and stability analysis After that, a nonlinear control law is constructed to regulate the cargo position to the desired location asymptotically, in the presence of ship roll and heave movements The boundedness and convergence of the closed-loop signals are proven with Lyapunov-based analysis To the best of our knowledge, this is the first closed-loop scheme that can achieve asymptotic control results, without linearizing/approximating the original nonlinear dynamics when performing controller design and stability analysis, for underactuated ship-mounted cranes with ship roll and heave movements Hardware experimental results are included to show that the proposed control method can achieve satisfactory control performance and it admits strong robustness against external perturbations

Nonlinear Stabilizing Control for Ship-Mounted Cranes With Ship Roll and Heave Movements: Design, Analysis, and Experiments

Sliding mode control (SMC), which is known to present strong robustness against various disturbances, has been extensively employed on underactuated systems, whose control problem has been a research focus in recent years. However, though received great attention, the study on SMC for underactuated systems still remains quite open since it is very challenging to construct a proper manifold which can simultaneously stabilize both actuated and unactuated system states. Motivated to promote the corresponding research, we propose an improved second-order SMC (IS-SMC) method for a class of nonlinear underactuated systems in this paper, which guarantees that the closed-loop system's equilibrium point is asymptotically stable even in the presence of unknown nondiminishing disturbances. Different from traditional SMC methods presenting with chattering problem, the control inputs of the proposed method are essentially continuous, which brings much convenience for practical applications. Moreover, for the disturbances which are second-order differentiable, an enhanced IS-SMC (EIS-SMC) method is derived to guarantee the smoothness for both the control inputs and their derivatives. Finally, the proposed approach is applied to a practical underactuated system: The overhead crane system, with sufficient simulation results provided to validate the efficiency of the proposed method.

Continuous Sliding Mode Control Strategy for a Class of Nonlinear Underactuated Systems

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.

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

Rotational-translational actuator (RTAC) systems can capture the major working principle of dual-spin spacecrafts and can be used to study the despin maneuver. In this paper, we consider the problem of globally stabilizing RTAC systems, which work in the vertical plane and are affected by nonvanishing matched disturbances by employing continuous control inputs. To this end, a nonlinear continuous control approach is synthesized to effectively damp out the platform oscillations, while ensuring that the eccentric ball's rotation angle returns to zero without residual swing. To our knowledge, this paper yields the first continuous controller, which is designed and analyzed without linearizing/approximating the original nonlinear dynamical equations to globally stabilize both the rotation and translation of RTAC systems influenced by nonvanishing matched disturbances. We implement experiments to show that the proposed control approach can achieve superior performance vis-a-vis existing methods and it admits for good robustness.

Biao Lu

Papers

Amplitude-Saturated Nonlinear Output Feedback Antiswing Control for Underactuated Cranes With Double-Pendulum Cargo Dynamics

Nonlinear Stabilizing Control for Ship-Mounted Cranes With Ship Roll and Heave Movements: Design, Analysis, and Experiments

Continuous Sliding Mode Control Strategy for a Class of Nonlinear Underactuated Systems

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

Nonlinear Continuous Global Stabilization Control for Underactuated RTAC Systems: Design, Analysis, and Experimentation