This paper presents a force control strategy for a water-surface robot. The
control strategy reduces the number of vehicle actuators required for the
force control by utilizing the restoring force/moment applied to the vehicl
e. In this research, the relationship between thruster outputs and the cont
act force/moment at the endpoint is derived taking the restoring force into
account, and the range of the realizable contact force is calculated using
this relationship. Moreover, a simulator of the vehicle motion is develope
d and the results of experiments using this simulator illustrate the validi
ty of the proposed algorithm.