In goal-based tasks such as navigating a robot from location A to location B in a dynamic environment, human intent can mean to choose a specific trade-off between multiple competing objectives. For example, intent can mean to find a path that balances between "Go quickly" and "Go stealthily". Given human expectations about how a path balances such tradeoffs, the path should match the human's intent throughout the entire execution of the path even if the environment changes. If the path drifts from the human's intent because the environment changes, then a new robotic-path needs to be planned -- referred to as path-replanning. <p> </p>
We discuss here three system-initiated triggers (prompts) for path-replanning. The objective is to create an interactive replanning system that yields paths that consistently match human intent. The triggers are to replan (a) at regular time intervals, (b) when the current robotic path deviates from the user intent, and (c) when a better path can be obtained from a different homotopy class. Further, we consider one user-generated replanning trigger that allows the user to stop the robot anytime to put the robot onto a new route. These four trigger variants seek to answer two fundamental critical questions: When is a re-planned path acceptable to a human? and How should a planner involve a human in replanning?
n a problem where a human uses supervisory control to manage robot path-planning, there are times when human does the path planning, and if satisﬁed commits those paths to be executed by the robot, and the robot executes that plan. In planning a path, the robot often uses an optimization algorithm that maximizes or minimizes an objective. When a human is assigned the task of path planning for robot, the human may care about multiple objectives. This work proposes a graphical user interface (GUI) designed for interactive robot path-planning when an operator may prefer one objective over others or care about how multiple objectives are traded oﬀ. The GUI represents multiple objectives using the metaphor of an artist’s palette. A distinct color is used to represent each objective, and tradeoﬀs among objectives are balanced in a manner that an artist mixes colors to get the desired shade of color. Thus, human intent is analogous to the artist’s shade of color. We call the GUI an “Adverb Palette” where the word “Adverb” represents a speciﬁc type of objective for the path, such as the adverbs “quickly” and “safely” in the commands: “travel the path quickly”, “make the journey safely”. The novel interactive interface provides the user an opportunity to evaluate various alternatives (that tradeoﬀ between diﬀerent objectives) by allowing her to visualize the instantaneous outcomes that result from her actions on the interface. In addition to assisting analysis of various solutions given by an optimization algorithm, the palette has additional feature of allowing the user to deﬁne and visualize her own paths, by means of waypoints (guiding locations) thereby spanning variety for planning. The goal of the Adverb Palette is thus to provide a way for the user and robot to ﬁnd an acceptable solution even though they use very diﬀerent representations of the problem. Subjective evaluations suggest that even non-experts in robotics can carry out the planning tasks with a great deal of ﬂexibility using the adverb palette.