农业工程学报2017，Vol.33Issue(23)：66-72,7.DOI:10.11975/j.issn.1002-6819.2017.23.009
果园货运链索横向振动非线性控制
Nonlinear transverse vibration control of orchard conveying chain system
摘要
Abstract
Vibrations associated with motion can degrade the performance of transport systems in orchards. It is important to suppress vibrations which are subjected to varying parameter and boundary disturbance. Early research on the vibration reduction in continuously moving systems was focused on the passive control methods by changing the mass or stiffness to absorb vibrational energy. To improve the effectiveness of vibration controller, many active control methods have been proposed with actuating mechanisms to compute the control effect. The application of conveying chain system was proved to be labor-saving and high efficientin mountainous orchards. Unlike a moving string system, the conveying chain system in the orchard is more complicated in the structure and boundary excitation. When the chain link engages a sprocket tooth,there is an impact caused by polygonal action.The polygonal action results from the chain-support engagement and its resulting vibrations are the source of most of the noise. Moreover, it is inconvenient to mount actuators on the conveying chain system. Since the boundary control technique requires relatively few sensors and actuators, a particular actuator as the control mechanism was attached and coupled to the boundary of the moving chain.The control force was applied by the actuator with negligible dynamics, which was used to reduce the energy of the moving chain while dissipating the energy of a short length of the chain. An image acquisition device was used to measure the transverse displacement of the observation point. The actuator was activated when the vision sensor indicated that the chain vibration has occurred. The behavior of transverse vibration could be predicted by a two-dimensional model in a vertical plane. Then the mathematical model of the coupled chain system including the actuator dynamics was derived by using Hamilton's principle, which could be represented by the nonlinear partial differential equations after the constraints had been applied. The Lyapunov method illustrates that the states of the system will ultimately travel to an equilibrium point if the total energy is dissipating. The energy dissipation strategy was extended to the chain model considering the polygon effect. In the controlled span part, the Lyapunov method was proposed to design the force control law for ensuring the vibration reduction in one span. Based on the total vibration energy of the moving chain, an energy-based Lyapunov function candidate was defined, which assured the dissipation of the vibration energy. To assure the asymptotical stability of the closed-loop system, a force control law was analyzed to determine the control force under the conditions of unknown disturbance and known disturbance. The proposed control force aimed to enforce this span part to be stationary or vibrate with a small amplitude. The comparison of the vibration amplitude at mid-span point under the controlled condition and uncontrolled condition clearly demonstrated that the vibration of chain part decreased much faster with the controller. The asymptotic exponential stability of moving chain system is proved by using the boundary force controller. The performance of the chain control system depends on force control law with guaranteed stability as well as actuator placement. Both simulation and experimental results confirm the feasibility of vibration suppression.关键词
农业机械/运输/振动/山地果园/链索/作动器/李雅普诺夫方法/振动控制Key words
agricultural machinery/transportation/vibrations/mountainous orchard/chain/actuator/Lyapunov method/vibration control分类
农业科技引用本文复制引用
李君,薛坤鹏,杨洲,洪添胜..果园货运链索横向振动非线性控制[J].农业工程学报,2017,33(23):66-72,7.基金项目
国家自然科学基金项目(51205139) （51205139）
农业部农业科研创新团队项目(农办人[2015]62 号) （农办人[2015]62 号）
广东省岭南水果产业技术体系创新团队建设项目(2017LM1107) （2017LM1107）
