具柔性脊柱的四足机器人结构优化与控制

发布时间：2018-09-14 10:05

【摘要】：四足机器人具有良好的环境适应性和运动灵活性,可以广泛运用于军事、工业、生活等各个方面,成为机器人研究领域中的热点问题。论文在前人研究的基础上,设计了具有柔性脊柱的四足机器人,建立了其动力学模型,分析了bound步态下模型的被动运动特性,研究了机身长度、惯量和刚度参数对机器人运动性能和稳定性的影响,完成了结构参数优化,提出了机器人常用步态的控制方法。猎豹被认为是速度最快的四足哺乳动物,本文从仿生学角度出发,参考猎豹的骨骼构型和运动方式,开发HUST cheetah四足机器人。依照猎豹的骨骼结构特点,构建四足机器人的基本构型框架。分析在不同运动状态下猎豹的受力特性,提出四足机器人基本设计原则。仿生学研究发现动物在运功过程中,关节之间存在很大的相关性,利用主成份分析法(Principal Component Analysis)探究猎豹运动过程中各个关节间的相关性,耦合具有相关性的关节,减少了机器人主动驱动关节数量,优化机器人的机械结构。在此基础上,提出了HUST cheetah四足机器人的设计原理和整体设计方案。观察猎豹bound步态的运动特点,通过合理假设与简化,建立具柔性脊柱的四足机器人在bound步态下的动力学模型。为了减少该模型的结构参数变量、使模型更具有一般性,对模型进行了无量纲化处理。采用庞加莱映射方法研究此模型的被动动力学,利用牛顿-拉弗逊方法提出了模型不动点求解方法。分析了在不动点下模型的被动运动特性,提出了不动点稳定性的判定方法,为结构参数优化和控制研究提供理论基础。稳定性研究发现合理的结构参数是决定机器人稳定性的关键。以提高具柔性脊柱的四足机器人在不动点处的运动性能和稳定性为优化目标,提出了同一系统能量状态下不动点的搜索方法,分析在同一能量状态下机器人脊柱长度、惯量和刚度对不动点稳定性的影响,得出了腿部刚度和脊柱刚度是决定具柔性脊柱的四足机器人稳定性的关键因素,进而完成了四足机器人长度、惯量和刚度优化。在此基础上进一步分析了非对称前后脊柱参数对机器人运动性能和稳定性的影响,研究发现合理降低前后脊柱质量比既保证了稳定性又提升了机器人的运动性能,据此完成了非对称前后脊柱参数的优化。此外刚性脊柱模型和柔性脊柱模型的对比分析发现,柔性脊柱能够提高四足机器人的运动性能。基于被动动力学研究结论可知,在理想情况下机器人能够在无需借助外界驱动的情况下实现自稳定的周期运动。然而由于摩擦、外界干扰等因素的影响,机器人很难持续稳定运动。为使HUST cheetah机器人能够按照被动运动方式实现持续稳定运动,本文构建了基于机器人被动动力学的分层控制器。在高层控制器中,利用被动动力学,提出了基于目标状态的关节控制方法。在底层控制器中,提出了基于位置和速度闭环的PD力矩控制,并通过仿真试验验证了控制算法的有效性。此外,猎豹常用步态除了适合高速运动的bound步态外,还有适合低速运动的tort步态,本文还提出了基于弹簧倒立摆模型(SLIP)的HUST cheetah机器人tort步态控制方法。在上述理论分析与研究基础上,开发了具有柔性脊柱的四足机器人HUST cheetah,完成了步态运动和理论验证试验,证明了HUST cheetah机器人高速稳定运动能力。
[Abstract]:Quadruped robot has good environmental adaptability and motion flexibility, and can be widely used in military, industrial, life and other aspects. It has become a hot issue in the field of robot research. Based on previous studies, a quadruped robot with flexible spine is designed, its dynamic model is established, and its bound gait is analyzed. The passive motion characteristics of the model are studied. The effects of the fuselage length, inertia and stiffness parameters on the motion performance and stability of the robot are studied. The structure parameters are optimized and the gait control methods are proposed. The cheetah is considered to be the fastest quadruped mammal. From the bionics point of view, the cheetah's skeleton is referred to. HUST cheetah quadruped robot is developed in this paper. According to the characteristics of the cheetah's skeleton structure, the basic configuration frame of the quadruped robot is constructed. Principal Component Analysis (PCA) is used to explore the correlation between the joints in the process of cheetah movement, coupling the related joints, reducing the number of active driving joints and optimizing the mechanical structure of the robot. On this basis, the design principle and the whole of HUST cheetah quadruped robot are proposed. A dynamic model of a quadruped robot with a flexible spine under bound gait is established by observing the kinematic characteristics of the leopard bound gait. In order to reduce the structural parameters of the model and make the model more general, the model is dimensionless. The Poincare mapping method is used to study this problem. The passive dynamics of the model is solved by Newton-Raphson method. The passive motion characteristics of the model at the fixed point are analyzed. A method for determining the stability of the fixed point is proposed. It provides a theoretical basis for the optimization and control of structural parameters. To improve the motion performance and stability of a quadruped robot with a flexible spine at a fixed point, a method of searching fixed points under the same system energy state is proposed. The influence of the length, inertia and stiffness of the robot spine on the stability of the fixed point under the same energy state is analyzed, and the leg stiffness is obtained. Degree and spinal stiffness are the key factors to determine the stability of a quadruped robot with a flexible spine, and then the length, inertia and stiffness of the quadruped robot are optimized. The stability of the robot is guaranteed and the motion performance of the robot is improved. The optimization of the parameters of the asymmetrical front and rear spines is accomplished. In addition, the comparison between the rigid spine model and the flexible spine model shows that the flexible spine can improve the motion performance of the quadruped robot. It can realize self-stable periodic motion without external drive. However, it is difficult for the robot to move steadily because of friction and external disturbance. In order to make the HUST cheetah robot move steadily in passive mode, a hierarchical control based on passive dynamics is proposed. In the high-level controller, a joint control method based on target state is proposed by using passive dynamics. In the low-level controller, a closed-loop PD torque control based on position and speed is proposed, and the effectiveness of the control algorithm is verified by simulation experiments. Besides the bound gait which is suitable for high-speed movement, the common gait of cheetah is also presented. A tort gait control method based on the spring inverted pendulum model (SLIP) is proposed for the tort gait control of the HUST cheetah robot. On the basis of the above theoretical analysis and research, a quadruped robot with a flexible spine, HUST cheetah, is developed. The gait motion and theoretical validation tests are completed, and the HUST cheetah machine is proved. The robot has high speed and stable movement ability.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TP242

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