In the literature, mobile robots featuring both omni-directional and rough-terrain mobility are typically realized by heavy and complicated mechanisms. In considering real outdoor applications, such as hazardous site-inspections or scientific investigations, however, it is desired to develop small and light-weight robots by focusing on the mechanical simplicity and toughness. The primary objective of this study is to investigate and to realize an omni-directional mobile robot on unpaved rough terrain by small, light-weight, simple mechanism. For this purpose, we propose a new concept of wheel structure as well as an omni-directional moving robot. The new wheel, named globular metal spring wheel and composed simply of several super-elasticity-material rods, has not only omni-directional functionality but also properties of light weight, mechanical simplicity and external shock absorbing function. With this globular wheel, a new omni-directional mobile robot, “Eggbeater”, is also developed to evaluate the mobility performance. This paper presents our proposal and development of the globular metal spring wheel and the omni-directional rough-terrain mobile robot, and discusses performance evaluation experiments.

This paper presents a new methodology of attitude determination for cost-effective and small-size inertial measurement units, consisting of tri-axial gyroscope sensors, accelerometers and geo-magnetometers. Introduced for the algorithm development is a quaternion feedback structure, where bias terms in the gyroscope rate information, appearing in the phase-locked loop, are identified with the theoretical guarantee of the global and asymptotical stability. The bias-term identification and modification process is performed continuously without the influence of the disturbance by combining the proposed disturbance evaluation scheme and the conventional vector matching method. Practical validity of the presented framework is fully evaluated by experiments. The evaluation result shows that the approach in this paper can offer drift-free performance with property of disturbance attenuation and rejection under arbitrary high-frequency attitude test motion of spatial rotation and translation.