Energy optimal design of servo-actuated systems: A concurrent approach based on scaling rules

This paper addresses the issue of reducing the energy consumption of servo-actuated systems by means of the optimal selection of the electric motor and of the gearbox from catalogs of commercially available components. This idea overcomes a lack of literature: on the one hand, the energy efficiency of these systems is usually tackled through the improvement of the efficiency of each individual component rather than on focusing on a global efficiency goal; on the other one, the methods to select these components neglect the specific issue of energy consumption, being usually focused on cost reduction or minimum motor sizing. The aim of this paper is to propose a model-based design approach for the energy-optimal concurrent selection of motor, coupling and gearbox in servo-actuated systems. The method is based on the use of scaling rules, which are developed to condensate all the relevant characteristics of the system into just two parameters: the gearbox transmission ratio and the motor continuous torque at stall. Scaling rules summarize and reveal the complex relations between the system parameters and energy consumption, and hence are incorporated into the analytic formulation of the overall energy consumption. The use of these metamodels, that can be easily obtained from data provided in datasheets, allows casting the design problem as a constrained optimization problem with just two design variables. The outlined procedure is completely automatic and does not require any design iteration. The results, evaluated for two application examples, demonstrate the relevant energy savings provided by the proposed method.