Real-Time Optimization for Eye-in-Hand Visual Search

This paper presents a multistage, real-time optimization algorithm to perform visual searches. A cost function relates the success of the visual search at any given pose in the workspace. This function is measurable at every camera pose, but it is not necessarily known as a function of changing pose, and its gradient with respect to the workspace or joint space coordinates is not known. In the first stage, a camera is constrained on a fixed sphere centered on the robot and searches for a general target direction by multidirectional direct search. In the second stage, the camera is constrained on a series of spheres centered on refined estimates of the search target's position. A series of extremum seeking control (ESC) algorithms are executed to search the best pose to observe the target. Since there is no existing method to detect when ESC has converged, we propose a novel frequency domain criteria to decide when to terminate the current ESC and launch another on the next candidate sphere. We prove that, under certain conditions, ESC will converge to known neighborhood of the optimal point in finite time. Simulations and experiments are presented to illustrate the effectiveness of the proposed algorithm.