Track a point without the known map

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Hi, everyone! I have a application that require the robot following a point in the indoor environment with variant obstacles. the robot is aware of the target point relative position (x, y). the robot is equipped with 3D camera. How can the robot move from the current pose to the target position(x,y), actually here we set a problem that what action can reduce the relative value (x,y) without a known map.