Stabilization of Visually Guided Robotic Lampreys
J.C. Overdevest (TU Delft - Mechanical Engineering)
M. Jafarian (TU Delft - Team Matin Jafarian)
C. Cavaliere (TU Delft - Team Bart De Schutter)
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Abstract
This thesis contains two contributions to the stabilization of visually guided robotic lampreys: the head stabilization method and the head-led target tracking design. Both approach the problem that camera inputs, attached to the head segment, are disturbed due to the participation of the head in the locomotion gait of the robot. Head stabilization is designed to stabilize the head segment itself, and head-led target tracking is designed to stabilize the target in the field of view of the cameras. The head stabilization and head-led target tracking designs are build upon the Ijspeert model. The Ijspeert model is an biologically inspired oscillator-based central pattern generator, capable of producing locomotion signals to achieve a lateral undulation gait. Analysis of this Ijspeert model is done by rewriting the model as a network of Kuramoto oscillators. This analysis concludes with a proof for the convergence of the phase differences of the Ijspeert oscillators. Although methods that mitigate the head stabilization problem for robotic lampreys have been designed before, the head stabilization method in this thesis approaches the head stabilization problem as a control problem for the fist time, to the best of our knowledge. The head stabilization method is designed to align the head segment with the average body direction, by providing head stabilizing parameters to the Ijspeert model. Perfect head stabilization is achieved, under the assumption that the motor dynamics are instant. Even though head stabilization is not perfectly achieved in reality with non-instant motor dynamics, we have verified that the head stabilized Ijspeert model is an improvement in terms of head stability, compared to the Ijspeert model without head stabilization. The designed head stabilization method is applied to a novel head-led target tracking design. This method combines a forward locomotion gait with a turning controller to perform target tracking, and is designed to increase the accuracy of visual information by directing the head segment towards the target. The head-led target tracking design is verified by placing the robotic lamprey in a virtual fluid environment with a target, which showed that the target is reached by the robot. Furthermore, the head-led target tracking design is compared to a design from the literature that does not direct the head segment towards the target. The head-led target tracking design shows improvements to the design from the literature in terms of the used performance measures.