双足机器人气动变刚度足部设计及步态规划研究

发布时间：2018-09-08 09:53

【摘要】：仿人双足机器人具有灵活的移动机构和很强的移动能力,特别在崎岖不平的地面及复杂的环境中双足机器人的移动能力相比轮式和履带式机器人具有明显的优势。但是,目前双足机器人的足部结构多为平足和点足结构,在机器人的步行过程中足部无法始终提供可靠的支撑效果,在地面突起物的影响下常发生足部支撑点区域的变化和支撑点的滑移,对双足机器人的行走稳定性产生负面的影响。因此本课题旨在设计一种能够降低不平整地面对双足机器人行走稳定性影响的足部系统,并针对这种足部结构,设计双足行走步态。首先,总结了平足结构及点足结构的问题,借鉴了目前具有适应能力的足部设计方案,提出了基于被动排气原理的气动变刚度足的结构方案,使足部上的变刚度单元能够通过被动触发实现高低刚度切换的功能,使足部既能为双足步行提供有效支撑又能包容地面突起物。基于以上变刚度方案进行了变刚度单元的布置方案研究,对足部结构进行了设计和校核,集成压力传感器,完成结构设计。其次,考虑气电混合驱动的双足机器人的实际机械结构,考虑具有两个耦合自由度的膝关节的结构特点,建立了双足机器人的运动学模型。考虑气动变刚度足的弹性势能,考虑足部柔性对机器人姿态的影响,建立了双足机器人系统的动力学模型。而后,考虑足部触地及离地时姿态保持水平的要求,利用多项式插值的方法规划了适用于气动变刚度足的双足步行步态。求解了步行过程中各关节转角的运动轨迹,结合气动肌肉的气压-位移特性以及关节的结构特点,求解了肌肉气压变化轨迹。最后,搭建刚度实验平台并分析了变刚度单元的刚度特性;对压力传感器进行了标定。搭建足部适应能力实验装置,验证足部适应地面突起物的功能。设计并搭建了双足行走实验平台,针对机器人的硬件接口搭建了双足机器人的控制系统,针对电机和气动肌肉的特性设计了关节控制器。进行了平整地面和不平整地面上的行走实验,验证了步态规划算法的正确性,对比了普通平足和气动变刚度足的步行姿态及ZMP轨迹,验证了气动变刚度足部系统的功能以及其对双足机器人步行稳定性的改善。
[Abstract]:The humanoid biped robot has flexible moving mechanism and strong moving ability. Especially in the rugged ground and complex environment, the biped robot has obvious advantages over wheeled and crawler robots. However, at present, the foot structure of biped robot is mostly flat foot and point foot structure, and the foot can not always provide reliable support effect during the walking process of the robot. Under the influence of the ground protrusions, the change of the supporting point area and the slip of the support point often occur, which has a negative effect on the walking stability of the biped robot. Therefore, the purpose of this paper is to design a foot system which can reduce the effect of uneven action on the walking stability of biped robot, and to design the biped gait for this kind of foot structure. Firstly, the problems of flat foot structure and point foot structure are summarized, and the design scheme of pneumatic variable stiffness foot based on passive exhaust principle is put forward. The variable stiffness element on the foot can realize the function of high and low stiffness switching by passively triggering, so that the foot can not only provide effective support for biped walking but also contain ground protrusions. Based on the above variable stiffness scheme, the layout scheme of the variable stiffness element is studied. The foot structure is designed and checked, and the pressure sensor is integrated to complete the structure design. Secondly, considering the actual mechanical structure of biped robot driven by gas and electricity and the structural characteristics of knee joint with two coupling degrees of freedom, the kinematics model of biped robot is established. Considering the potential energy of aerodynamic variable stiffness foot and the effect of foot flexibility on robot attitude, the dynamic model of biped robot system is established. Then, considering the requirement of maintaining the level of foot attitude when touching the ground and leaving the ground, the biped walking gait suitable for pneumatic variable stiffness foot is planned by polynomial interpolation method. The motion trajectory of the joint angle during walking is solved. Combined with the pneumatic muscle pressure displacement characteristics and the structural characteristics of the joint, the track of the muscle pressure change is solved. Finally, the stiffness experimental platform is built and the stiffness characteristics of the variable stiffness element are analyzed, and the pressure sensor is calibrated. Build the foot adaptability experimental device to verify the foot adaptation to the ground protruding function. The biped walking experimental platform is designed and built. The control system of biped robot is built according to the hardware interface of the robot and the joint controller is designed according to the characteristics of motor and pneumatic muscle. The walking experiments on flat and uneven ground are carried out to verify the correctness of gait planning algorithm. The walking attitude and ZMP trajectory of common flat foot and pneumatic variable stiffness foot are compared. The function of pneumatic variable stiffness foot system and its improvement on walking stability of biped robot are verified.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP242

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