Noriaki Mizukami

Iterative overlap-part estimation method for localization and generation of reliable terrain maps

For efficient wide-area exploration by an autonomous planetary rover, the generation of a global environmental map is very important. A global map is generated by matching and overlapping terrain features from digital elevation maps that are obtained during a rover traveling in a region. Each set of data contains information in different areas, and the overlapping part in each set of data may be missing data because of difference in a position and an orientation of a rover. Conventional alignment techniques based on comparing features assume that data were measured from very similar positions and orientations. Otherwise, differences in the measured region deteriorate the quality of a resulting global map. This problem should be addressed by a fairly simple way because of the limited processing capabilities of planetary exploration rovers. Hence, we propose a method for generating highly accurate global maps by considering differences in measured regions and iteratively estimating the overlapping parts in terrain data. The method is evaluated using simulated data and some experimental data obtained from experiments using a mobile robot in a real environment.

Simultaneous Control for Position and Vibration of a Planetary Rover with Flexible Structures

This paper proposes a synthesis procedure for a robust control target to be utilized in the simultaneous control of position and vibration of a planetary rover with flexible structures. The target is designed as a type of feedforward control input and its profile is derived only by solving a regulator problem with an initial velocity. In the regulator problem, the non-stationary robust control method is employed to make the target profile be robust against parameter variation. Further, the design procedure for the target is independent of the positioning distance and time schedule. The robustness of the target against parameter variation is examined through numerical calculations and the results are compared with those obtained from conventional methods. As a result, the usefulness of the proposed command shaping procedure is demonstrated and the high robustness of the target is confirmed.

Discussion on validity of lugged wheel model and evaluation method

Soft soil covers planetary surfaces, so the wheel of a planetary rover easily slips and gets stuck. In order to prevent increase in the slip and getting stuck, the wheel can have lugs that have a shape of a paddle to improve the wheel force. There have been some studies about the influence of the lugs. However, design method of an effective lug has not been studied well yet. Since terramechanics-based wheel models have been considered with a flat wheel surface, those models based on terramechanics are not applicable to the lugged wheel. In this research, in order to establish the design method of the effective lugs, a lugged wheel model was discussed and proposed regarding the variation of the shear characteristics. The variation of shear characteristics is indicated by a shear deformation modulus. The lugged wheel model is based on the shear deformation modulus varied by the lug design. In this paper, the simulation was performed to verify the validity of the lugged wheel model, and it was confirmed that the model could formulate the performance of the wheel traversability. Moreover, the wheel experimental device was described to understand the traversability of the lugged wheel. The evaluation method of the proposed lugged shear deformation model was also considered.