| Future missions to Mars will place heavy emphasis on scientific sample and return operations, which will require a rover to revisit sites of interest. Visual Teach and Repeat (VT&R) has proven to be an effective method to enable autonomous repeating of any previously driven route without a global positioning system. However, one of the major challenges in recognizing previously visited locations is lighting change, as this can drastically change the appearance of the scene. In an effort to achieve lighting invariance, this thesis details the design of a VT&R system that uses a laser scanner as the primary sensor. The key novelty is to apply appearance-based vision techniques traditionally used with camera systems to laser intensity images for motion estimation. Field tests were conducted in an outdoor environment over an entire diurnal cycle, covering more than 11km with an autonomy rate of 99.7% by distance. |
