Research Initiation: Development of a Spherical Stepper Wrist Motor

本研究的目的是为研制能够在单个关节中进行三个方向运动的球形腕部步进电机奠定理论基础。球关节球形腕式马达具有结构简单、设计紧凑、工作空间中部除边界和转子离心力不平衡外无奇异性的特点。球形腕部步进电机在高速等离子、激光切割等要求末端执行器快速、连续、各向同性定向的领域有着重要的应用。这项研究将集中在三个方面。首先是利用有限元技术对给定设计的磁场和磁阻力进行预测，这也将有助于更好地了解设计参数对转矩和分辨率的影响。第二种是使用非线性编程技术的优化，以最大化扭矩，同时最小化指定分辨率下的重量和体积。第三个领域是开发两级控制方案，以预先规划最优轨迹，并开发具有良好干扰抑制的定向控制律。

The objective of this research is to establish a theoretical basis for the creation of a spherical wrist stepper motor capable of three degrees of orientation motion in a single joint. The ball-joint-like spherical wrist motor is characterized by its simplicity in structure, compact design and free from singularities in the middle of the workspace except at the boundaries and unbalanced rotor centrifugal forces. The spherical wrist stepper motor has significant applications where the end-effector is required to orient quickly, continuously and isotropically in all directions such as high speed plasma and laser cutting. The research will focus on three areas. The first is the prediction of the magnetic fields and reluctance forces for a given design using finite element technique, which will also provide a good understanding of the influences of the design parameters, on the torque and resolution. The second is an optimization using non-linear programming techniques to maximize torque while minimizing weight and volume for a specified resolution. The third area is the development of a two-level control scheme to pre-plan an optimum trajectory and to develop an orientation control law with good disturbance rejection.