Jianhong Zhang

Modeling of a Rope-Driven Self-Levelling Crane

This paper concerns the fields of the eccentric payload crane systems. We firstly introduce a four-rope-driven self-levelling crane system, which can adjust the payload to level precisely and safely by changing the lengths of the ropes. Then, the system model is deduced according to force equation, moment equation principles and geometry restrictions, without considering the acceleration items. Finally, a control strategy is proposed to adjust the system.

Fuzzy logic based adjustment control of a cable-driven auto-leveling parallel robot

To solve the level-adjusting and force-tuning problems of high accurate and costly payloads when loading and unloading, a cable-driven auto-leveling parallel robot is developed. A hierarchical fuzzy controller, which has the ability to deal with the rule explosion problem, is proposed in this paper. After a brief introduction of the architecture of the closed-loop control system for the cable-driven auto-leveling parallel robot, the construction of the hierarchical fuzzy controller is set up, in which the force offsets of the four cables and the angle deviations of the two diagonal inclinations are chosen as input variables, and the output variables are the position changes of the four linear motion units. The hierarchical fuzzy controller contains two layers - the low level layer which generates two outputs for leveling adjustment and force tuning, and the high level layer which is used to coordinate the two outputs from the low level layer. Experimental results have demonstrated that the hierarchical fuzzy controller can achieve the control objectives with high regulation accuracy and short adjusting time, and can be easily applied to practical systems.

Disturbance compensated adaptive backstepping control for an unmanned seaplane

A disturbance compensated adaptive backstepping controller is presented for a class of nonlinear systems with external disturbances. We develop a disturbance observer, with which the problem of disturbance compensation can be transformed into an adaptive control problem. Command filtered adaptive backstepping method is then used to design the control law to track the desired trajectory. In order to analyze the property of the controller, the overall close-loop error system is built. Using the Lyapunov approach, we prove that the proposed controller provides the uniformly asymptotic stability for the considered system and achieves perfect disturbance compensation. Finally, the developed method is applied to an unmanned seaplane system in the presence of large external disturbances. Simulation results show that the controller has good performance for the unmanned seaplane in different wave conditions.