This project develops a new motion planning paradigm for enabling robots to work in the presence of humans or cooperatively with humans as co-workers. The paradigm is intended to be fast, reactive, and responsive to the requirements that arise from human-robot interaction. It involves the definition and subsequent implementation of constraints that encode properties of human-aware paths and can be translated to cost functions characterizing path quality. New motion planners are proposed. The operation of these planners is guided by constraints and their corresponding cost functions. The planners produce paths compatible with a given set of constraints. A mechanism to incorporate user feedback on the relative importance of constraints is provided and semi-autonomous operation of the robots is considered. Importantly, the planners are embedded in a novel hybrid-systems framework that allows a robot to automatically switch among planners, and hence behaviors, in order to take into account different constraints and user preferences that arise in the context of semi-autonomous operation. Besides the actual implementation of the planners on specific platforms, this project also disseminates all developed libraries and planners. Compatibility will the Robot Operating System (ROS) is provided for wide adoption, while tutorials at major conferences are planned. The training of graduate students and female undergraduate students are a central focus of this project.