Bio-inspired egomotion estimation from optic flow fields

Tangential neurons in the fly brain are sensitive to the typical optic flow patterns generated during self-motion. We examine whether a simplified model of these neurons can be used to predict the measured motion sensitivities in the fly. The model is tested in a robotic self-motion estimation task.



Computational Modeling of Fly Tangential Neurons

The tangential neurons in the fly brain are sensitive to the typical optic flow patterns generated during self-motion. This suggests a possible involvement in the self-motion estimation process. We compared the measured local preferred directions and motion sensitivities of the VS-neurons (Krapp et al., 1998) to a matched filter model that is optimized for the task of self-motion estimation. In contrast to previous approaches, prior knowledge about distance and self-motion statistics is incorporated in the form of a "world model". We could show that a special case of the matched filter model is able to predict the local motion sensitivities observed in some VS-neurons. This suggests that their receptive field organization can be understood as an adaptation to the processing requirements of estimating self-motion from the optic flow.

In a second study, we examined whether the matched filter model can be used to estimate self-motion from the optic flow. Tests on a mobile robot (modified Khepera) demonstrated that the matched filter approach works for real time camera input and the noisy motion fields computed by Reichardt motion detectors. The achievable accuracy of the proposed approach was investigated in collaboration with the group of Prof. M.V. Srinivasan at the Center of Visual Sciences at the Australian National University in Canberra. We used a gantry carrying an omnidirectional vision sensor that can be moved along three translational and one rotational degree of freedom. The experiments indicate that the proposed approach yields accurate results for rotation estimates, independently of the current translation and scene layout. Translation estimates, however, turned out to be sensitive to simultaneous rotation and to the particular distance distribution of the scene. The gantry experiments confirm that the receptive field organization of the tangential neurons allows them, as an ensemble, to extract self-motion from the optic flow.