Robots, which are constructed from many elements that are related to various engineering systems including mechanical systems, electronic systems, artificial intelligence and so son, are going to be utilized in various fields. It is necessary to examine overall safety techniques for the establishment of robot safety. First, hazard control principles are systematized base on the accident causation theory "Action-change & Action-chain Models". Secondly, the constitution principles of hazard control systems that are the final line of defense against hazards are generalized and systematized using the theory of hazard control chains, in order that the principles can be applied to the overall fields of engineering. Finally, illustrative examples constituting hazard control systems are demonstrated for some robots, such as a transfer robot, a rescue robot etc., based on the principles.