Abstract
Mobile robots have the potential to be widely used. They can be used in complex indoor and outdoor
environments accomplishing jobs which typically are earmarked for humans. A basic requirement for
these kind of robots is ability to navigate autonomously. For autonomous navigation to be possible the robot needs to be able to perceive the environment around; specifically localize itself in it, and create a map which it can use to plan and navigate. Localization and mapping are inter-dependent on each other, that is to say localization quality determines mapping quality and mapping quality determines further localization quality. Furthermore, it will determine how reliably we avoid obstacles, search for objects, determine the best path for a goal etc. Quality of the map which is created is of enormous importance, as it inherently dictates merit of the task robot is expected to execute. Accurate mapping of environment becomes more challenging when it is attempted using a monocular camera. Monocular camera posses it’s host of difficulties, but is very cost effective compared to
expensive laser scanners and stereo cameras. As a sensor, monocular camera provides plethora of information like depth, color, texture which can be used object identification, face recognition, lip reading, traffic signs, and and 3D structure, most of which is still not being harnessed, and hence presents itself as a sensor for the future and worth pursuing. Therefore, we have used a Monocular camera as the quintessential sensor for mapping the surroundings. We are a long way from realizing monocular camera’s potential. As of now it is incapable of handling violent motions. A fast moving robot or a sharp turn leads to breaking of the mapping process. Sideways motion for the camera is an ideal movement for VSLAM systems, but this luxury is not afforded to mobile robots. Looking straight ahead and moving in front (along the principle axis) is a feasible motion for them. For such motion, moving straight in a line at slow speed(not too slow) produces better result, and when robot needs to turn it is done so moderately. Hence, we have proposed a planning framework which devices a path ensuring motion with aforementioned constraints, that is we have optimized heading change, and velocity with respect to distance from the goal. We model our robot as a non-holonomic vehicle which allows us to define feasible motion states for the robot. We than parametrize it’s states, namely it’s position and orientation into polynomial functions, which serve as easy inputs for optimization methods. We use optimization at two stages, first a non-linear optimization to generate path for a given start and goal position, and second a relatively naive quadratic optimization method to estimate initial guess for the non-linear optimizer. A good initial guess from the quadratic optimization method will be reflected in quality of final output. We show that by following the path generated by aforementioned framework VSLAM is able to localize camera successfully, which is to say estimated camera trajectory has similar curves to the generated trajectory. We also show following the
generated constrained trajectory tracking performance improves in comparison to when robot follows unconstrained trajectory generated by RRT, one of the most popular algorithms for path planning.
We add dense reconstruction of planar objects after the path planning framework in our attempts
towards automation. Algorithms used to create 3D maps from stream of images have primarily focused
on sparse point maps. Sparse maps are incomplete representation of the environment, making comprehension of available data very hard. They are also not able to cater complete information to modules down the pipeline of a full fledged robotic system. We have proposed a framework for dense reconstruction of 3D planar objects. Most objects in an indoor environment are planar, hence we have focused our attention towards reconstructing such surfaces. Targeting planar objects allows us to perform dense tracking in real time on commodity laptop. We have used Homography and segmentation techniques to identify and track planar objects. Post-reconstruction we present a modified Bundle Adjustment, an optimization technique used to correct position of 3D points. Traditionally VSLAM based systems have required human intervention, dense model of an environment will provide us with information such as span of obstacles and ground required for autonomous navigation. In results section we qualitatively demonstrate superiority of dense models over sparse point clouds. We also, both quantitatively and qualitatively show performance enhancement achieved by proposed bundle adjustment over original bundle adjustment.
In conclusion, we present a path planning framework which allows robot to move by on it’s own
accord if answer to “Where to go?” is known. We also present a reconstruction framework which
improves