Cooperative control for automatic towing operation by multiple DP tugboats with fully unknown model parameters

•A leader-follower formation is implemented, and a regulator for the virtual leader is designed to manipulate the towed object.•A customized model parameter-free Dynamic Positioning (DP) system is proposed to address the challenges of full unknown model parameters and large cable tension disturbances.•A backstepping control framework is constructed and a fuzzy adaptive law is incorporated to approximate the unknown dynamics and disturbances (environmental loads and cable tension) as a whole.