As an essential branch of metal additive manufacturing

wire and arc additive manufacturing (WAAM)

using an arc as the energy beam

is suitable for rapidly fabricating medium-to-large scale metal components and exhibits a wide application prospect in aerospace and national defense. Nevertheless

the issues of low forming accuracy

poor process stability and difficult defect control restrict high-efficiency and high-quality development and application of this technology. It has been urgently to implement online monitoring and closed-loop control during the entire WAAM process for the demand of reliable

automatic

and quality-ensured manufacture. The characteristic parameters and their main influential factors are analyzed. Principles and research status of process sensing methods are illustrated. Control methods of forming quality in WAAM are summarized. Eventually

principal developing orientations of process sensing and control in WAAM are proposed.