Design and Analysis of a Spherical Continuously Variable Transmission

In this article we propose the design of a novel continuously variable transmission, the spherical continuously variable transmission (S-CVT). The S-CVT consists of a sphere, input and output discs, and variators. The rotating input and output discs are connected to the power source and output shafts, respectively, while the sphere is situated between the input and output discs. The transmission ratio is controlled by adjusting the location of the contact point between the variators and the sphere, which in turn controls the axis of rotation of the sphere. The S-CVT can smoothly transit between the forward, neutral, and reverse states without any brakes or clutches, and its compact and simple design and its relatively simple control make it particularly effective for mechanical systems in which excessively large torques are not required (e.g., mobile robots, household appliances, small-scale machining centers). We describe the operating principles behind the S-CVT, including a kinematic and dynamic analysis. Simulations and experiments with a constructed prototype are conducted to assess the performance of the S-CVT, including a study of its energy efficiency vis-a-vis reduction gears.