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水下球形探测机器人自主运动控制研究
中文摘要

水下球形机器人具有耐压性强、稳定性好、运动灵活和易于隐蔽等优点,在军事国防、石油勘探、科学考察和水产养殖等领域应用前景广泛。运动控制技术是水下机器人实现控制目标的关键,但传统的水下机器人运动控制技术在时效性、精度和抗扰动等方面尚不能完全满足控制要求。因此,有必要研究耗时少,精度高,抗扰性强和易于工程实现的水下机器人控制方法。本论文以BYSQ-3水下球形探测机器人为研究对象,探索适合于该机器人的自主运动控制技术。主要针对水下机器人的点镇定、路径跟踪和姿态调节等常见运动模式展开研究。 本文主要研究了以下几个方面内容。 (1)利用牛顿运动定律,建立了惯性坐标系和水下球形机器人随体坐标系,分析了水下球形机器人静力学与动力学特点,综合考虑了水下球形机器人受到的重力、浮力、流体动力、科里奥利向心力、恢复力和干扰力等因素,建立了水下球形机器人的6自由度动力学模型及简化的水平面3自由度动力学模型。 (2)研究了基于系统齐次性理论的水下球形机器人的水平面点镇定运动控制方法。利用水下球形机器人6自由度运动学和动力学模型,进行微分同胚变换和控制输入变换,对动力学方程进行解耦,把解耦后的动力学模型分为两个子系统,研究了两个子系统的结构,设计了非线性有限时间自主运动点镇定控制律,并进行了理论推导、数值仿真和泳池实验。 (3)研究了基于加幂积分技术的水下球形机器人水平面点镇定运动控制方法,利用CFD技术分析了系统的水动力系数。通过在李雅普诺夫函数的构造中加入积分项,采用基于反步法的设计思路,设计了水下球形机器人的有限时间点镇定运动控制策略,由于不仅增益可调,幂指数也可调节,该控制器更易于工程实现。数值仿真和泳池试验结果证实所设计的控制器具有较快的收敛性和良好的稳定性。 (4)研究了水下球形机器人的曲线路径跟踪控制策略,把水下球形机器人的动力学方程转化为非线性级联系统,利用非线性级联系统理论设计了具有二阶非完整性的水下球形机器人路径跟踪有限时间控制器。该控制方法不仅对水下球形机器人适用,也可以直接推广至其他类型的非完整机械系统。 (5)研究了水下球形机器人的水平面航迹镇定的终端滑模有限时间控制方法,对航迹跟踪误差的运动学和动力学模型进行了研究,并分为运动学和动力学两个层面设计了路径跟踪控制器。运动学层面把速度误差看作虚拟控制输入镇定位置误差,动力学层面利用驱动电机实现速度误差的镇定,通过在控制器中引入积分项和自适应更新律,使路径跟踪误差在有限时间内收敛到原点,并具有较高的精度。 (6)研究了基于四元数描述的水下机器人姿态控制问题,设计了基于二阶积分滑模的自适应增益控制器,控制输入作用于滑模面的二阶导数,可以降低系统的抖振。所设计的自适应律可以更新控制器的增益,通过这种方法,不需事先知道不确定性和外部扰动的数值,可以避免控制器增益的过度适应问题。该控制器具有全局鲁棒性和有限时间稳定性。 通过以上研究,建立了BYSQ-3水下机器人的动力学模型,利用非线性有限时间控制理论,针对BYSQ-3水下点镇定、路径跟踪以及姿态调节三种常见运动模式,分别设计了控制器,与传统的渐进稳定控制器相比,基于有限时间理论所设计的控制器具有稳定性能好,响应速度快,抗干扰性强等优点,也更易于工程实现,使球形水下机器人在水下可以更好地完成各种控制任务。 关键词 水下球形探测机器人 欠驱动系统 自主运动有限时间控制 高阶滑模控制

英文摘要

The research content of this paper is one part of the National Natural Science Foundation of China“the design and research of a new amphibious spherical robot (51175048).”It mainly studies the motion control of underwater spherical robot. The nonlinear controllers are designed for the common motion of BYSQ-3 spherical underwater robot, the designed controller have good stability, fast response, strong anti disturbance etc., the control method can improve the performance of traditional asymptotically stable control strategy, more easy to implement in engineering. It provides theoretical basis and technical guarantee for underwater robots to accomplish various tasks with high quality. The controllers can also be extended to land mobile robots and space flying robots. In details, this paper mainly studies the following aspects: (1)By using Newton's laws of motion, the earth-fixed frame and the body-fixed frame of underwater robot are established, the statics and dynamics characteristics of the underwater spherical robot are analyzed. Considering the factors of underwater robot such as gravity, buoyancy, hydrodynamic force, Coriolis centripetal force and restoring force, interference force, the simplified 6 degree of freedom model and 3 degrees of freedom horizontal model are established. (2)The point stabilization problem for the underwater spherical roving robot (BYSQ-3) in the horizontal plane is addressed. The finite-time stable control laws are adopted to steer the robot to the origin fastly、 accurately and reliably. Firstly, the inner structure and operational principle of the robot is described and the kinematic and dynamic equations are established. Secondly, the diffeomorphism transformation and change of inputs are introduced to decouple the multivariable coupling system into two subsystems. The second subsystem consists of two double integrator systems. The finite-time controller is introduced to ensure part states converge to zero in finite time. Then, the other states are steered to the origin using the same method. Thirdly, the design process has no virtual input and the stability analysis is simple, the controller designed is easy for engineering implementation. The simulation and experiment results are presented to validate the shorter convergence time and better stability character of the controller. (3)The point stabilization motion control method of underwater spherical robot based on the power integral technique is studied. The hydrodynamic coefficients of the system are analyzed by CFD technology, and the finite time stabilization control strategy based on backstepping is adopted. Through the reversible transform, multi variable nonlinear dynamic equations of the system is divided into two cascaded form subsystem. The first subsystem is composed of two state variables, the second subsystems is composed of two double integral system, for the second subsystem, we designed the finite time stabilization controller which contained two stage. Each stage can ensure the two state variables finite time convergence. Finally the designed controller can guarantee all the state variables converge to the origin in finite time and the coupling phenomenon completely disappeared. The complexity of the system is reduced .Because the gain and the power index both can be adjusted, it is easy to implement in engineering. The finite time stabilization control the law has the advantages of fast convergence and strong anti-interference. The results of numerical simulation and pool test confirm that the controller has fast convergence and good stability. (4)The curve path tracking control strategy of underwater spherical robot is studied. We transform the dynamic equation of the underwater vehicle into a nonlinear cascade system, and design a finite time controller for underwater vehicle path tracking innovatively. The finite time control method of cascade system is not only suitable for underwater spherical robots, but also for other mechanical systems. This control strategy can also be directly extended to other types of non holonomic mechanical systems. Compared with the traditional asymptotically stable controller, the finite time controller can reduce the coupling degree and shorten the convergence time. The simulation results show that the designed finite time controller has good performance. Based on the simulation results, we have carried out the real world experimental test, and validated the effectiveness of the finite time controller. (5)Research on the control method of nonlinear finite time stabilization of spherical robot under water level track, through the study of the tracking error dynamics model of track, the kinetic equation is divided into two parts, using coordinate transformation into dynamic equation of motion error is with low coupling equation, the velocity error as the virtual controller town location error then, the drive motor to achieve stabilization of speed error, respectively, using the theory and the terminal sliding mode control method for cascade system nonlinear control, by introducing the integral term in the controller, the error size tracking in finite time convergence to the origin, and has a high precision. The breakthrough of traditional design method can only reach the infinite horizontal convergence limit of progressive convergence or exponential convergence, and achieve high precision fast track tracking control. (6)The attitude control system of underwater vehicle based on four element number description is studied. Aiming at the attitude control problem of underwater vehicle, a controller based on two order integral sliding mode adaptive gain is designed in this paper, which is a discontinuous finite time controller. The designed adaptive law can update the gain of the controller by this method without the need to know the value of uncertainty and external disturbance in advance. From the simulation results, the controller can avoid the over adaptation of the controller gain. The controller is globally robust and finite time stable, and the finite time stability is proved by the homogeneous theory. It is worth noting that the two order integral sliding mode is introduced to make the system smaller. It can be seen from the comparative data in the paper that compared with other control strategies, the control strategy has higher steady-state accuracy and faster convergence speed. The actual swimming pool experiment also shows the effectiveness of the controller. Through the above research, we initially grasp the basic motion control theory of underwater spherical exploration robot, the finite time motion controllers for common movement patterns of the spherical underwater robot are designed and and the strict theoretical deduction and proof are carried out. Numerical simulation and pool experiments verify the effectiveness of these controllers. The design methods of these finite time controllers can also be extended to other two order nonholonomic systems. KEY WORDS spherical underwater robot underactuated system autonomous movement finite time- control strategy higher order sliding mode control

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