Development of a multi-modal tactile force sensing system for deep-sea applications

With the increasing demand for autonomy in robotic systems, there is a rising need for sensory data sensed via different modalities. In this way system states and the aspects of unstructured environments can be assessed in the most detailed fashion possible, thus providing a basis for making decisions regarding the robot’s task. Compared to other sensing modalities, the sense of touch is underrepresented in today’s robots. That is where this thesis comes in. A tactile sensing system is developed that combines several modalities of contact sensing. Using such a system enables comprehensive tactile acquisition of the objects in the contact area of a robotic endeffector.

Furthermore, the multi-modal approach of the system increases confidence in the tactile signal as events perceived by the different tactile sensory channels can be compared. The resulting number of sensor elements also poses challenges to integration into robotic end-effectors because the available space is limited. Sensing modalities that are sensitive to contact forces often require an integration space directly at the contact location, thus leading to competing requirements.
The use of the tactile sense in robotic grippers is of great relevance especially for robotic systems in the deep sea. Up to now manipulation systems in master-slave control mode have been used in this area of application. An operator performing the manipulation task has to rely on visual feedback coming from cameras. Working on the ocean’s seafloor means having to cope with conditions of limited visibility caused by swirled-up sediment. Tactile sensing systems can help to speed up manipulation tasks under these conditions or even make them possible. Application in the deep sea poses additional challenges for the development of a tactile sensing system as the employed measurement principles have to cope with the environmental conditions, such as ambient pressure and water. Besides the measurement principles, the acquisition electronics as well as the actuation methods have to withstand the high pressures (in the framework of this thesis the developed system and its components are evaluated at pressures of up to 600 bar, corresponding to a depth of 6,000 m).

These topics are explored within this work. The feasibility of the developed concepts is evaluated in combination with an industrial manipulator arm for deep-sea applications and within a pressure chamber.



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last updated 31.03.2023