A novel spherical wheel driven by chains with guiding wheels

A novel combination of chains with guiding wheel and spherical wheel unit (CWWU1) is presented in this paper, and its operating principle is basically a spherical wheel driven by two perpendicular pairs of chains with a set of guiding wheels. Thus, a CWWU1 base robot similar to the previous CWWU (combination of Omni wheel and spherical wheel unit) can perform the static and dynamic balancing function that a single wheel with inverse mouse-ball drive developed by Carnegie Mellon University (CMU) can also achieve. However, the previous CWWU has an unwanted compromise in which the strength is inversely proportional to the smoothing motion needed to be made. That is, increase the Omni wheels to improve the smoothness of motion will reduce the spacing of Omni wheel which will weak the strength of the Omni wheels. The CWWU1 can solve this problem, and the major difference between them is that the motion of CWWU1 can be smoother than the previous CWWU due to more than one guiding wheel to contact the surface of the spherical wheel. The other difference is that the size of CWWU1 can be reduced more as compared with the previous CWWU in case of size limit applications. Both robots have several exclusive features which can resolve key problems inherited in the CMU robot. Especially, the simultaneous demand of both a high-friction and low-friction material for the spherical ball is an undesired compromise needed to make for the CMU robot.