| The increasing demand for multi-degree-of-freedom (DOF) actuators in a number of industries has motivated a flurry of research in the development of non-conventional actuators, one of which is a ball-joint-like variable reluctance (VR) spherical motor. This motor is capable of providing smooth and isotropic three-dimensional motion in a single joint. Compared to conventional robotic manipulators that offer the same motion capabilities, the innovative spherical motor possesses several advantages. Not only can the spherical motor combine 3-DOF motion in a single joint, it has a large range of motion with no singularities in its workspace. The VR spherical motor is much simpler and compact in design than most multiple single-axis robotic manipulators. The motor is also relatively easy to manufacture. These unique characteristics of a spherical motor have potential contributions to a wide range of applications such as coordinate measuring, object tracking, material handling, automated assembling, welding, and laser cutting. Most of these features have been demonstrated in previous research efforts at Georgia Tech. The spherical motor, however, exhibits coupled, nonlinear and very complex dynamics that make the design and implementation of feedback controllers very challenging. The orientation-varying torque generated by the spherical motor also contributes to the challenges in controller design. |
