USING MINIMAX APPROACHES TO PLAN OPTIMAL TASK COMMUTATION CONFIGURATIONS FOR COMBINED MOBILE PLATFORM-MANIPULATOR SYSTEMS

An important characteristics of mobile manipulators is their particula r kinematic redundancy created by the addition of the degrees of freed om of the platform and those of the manipulator. This kinematic redund ancy is very desirable since it allows mobile manipulators to operate under many modes of motion and to perform a wide variety of tasks. On the other hand, it also significantly complicates the problem of plann ing a series of sequential tasks, in particular for the critical times at which the system needs to ''switch'' from one task to the other (t ask commutation), with changes in mode of motion, task requirement, an d task constraints. This paper focuses on the problem of planning the positions and configurations in which the system needs to be at task c ommutation in order to assure that it can properly initiate the next t ask to be performed. The concept of and need for ''commutation configu rations'' in sequences of mobile manipulator tasks is introduced, and an optimization approach is proposed for their calculation during the task sequence planning phase. A variety of optimization criteria were previously investigated to optimize the task commutation configuration s of the system when task requirements involve obstacle avoidance, rea ch, maneuverability, and optimization of strength. In this paper, we s how that a ''minimax'' approach is particularly adapted for most of th ese requirements. We develop the corresponding criteria and discuss so lution algorithms to solve the ''minimax'' optimization problems. An i mplementation of the algorithms of our HERMIES-III mobile manipulator is then described and sample results are presented and discussed.