A delta wing is subjected to small-amplitude perturbations over a range of periods, to simulate leading-edge control concepts. Substantial modifications of the instantaneous and averaged structure of the leading-edge vortex are attainable, both with and without a downstream impingement plate. The features of the vortex response are characterized using a technique of high-image-density particle image velocimetry. The location of the onset of vortex breakdown can either be advanced or retarded, and the attendant changes in vortex structure are interpreted in the context of buffeting of the impingement plate. Comparison of the vortex structure with and without deployment of the plate shows a dramatic influence of the plate.