Optimization of the choice of the system electric drive-device-transmission for mechatronic applications

The appropriate choice of an electrical motor and transmission in mechatronicapplications, that is under dynamic conditions generated by both inertial and resistant loads, has a deep effect on the machine performance. It is influenced by considerations both of technical and economic nature. Such a step in mechatronic design is complicated from two circumstances: the motor torque depends significatively on the motor own moment of inertia, that is unknown, and the motor and the transmissionchoices are deeply interrelated: this paper shows that the key parameter is the generalized motor’s moment of inertia at the joint; furthermore the limitations of the required components, such as the operating ranges of the drivesystem, must be taken into account. Once the machine task is specified, with generic load’s periodic motion law and resistant torque, a previously stated feasibility criterion allows to eliminate all the drivesystems that are not capable to drive the given load, whatever is the transmission ratio. In this paper, a detailed analysis of this criterion, besides permitting its presentation in terms of known mechanical quantities, allows to address the optimization of the choice of motor and transmission when the motor’s thermal problem is more limiting than the maximum torque exerted by the motor. The method is then applied to an industrial case.