An expert system for motor sizing using mechanical dynamics and thermal characterization

Motor selection is a crucial step in the design and development of practical machinery that perform motion tasks. In particular, proper servomotors must be used in industrial motion control systems. Incorporating an unsuitable motor can lead to inefficiency, malfunction, and adverse consequences related to safety, accuracy, and cost of the overall system. An expert system (ES) that incorporates the skill, knowledge, and experience of motor selection along with the associated engineering principles can provide many practical benefits. Such a knowledge-based decision-making system can improve the speed and accuracy of the selection process, while greatly reducing the undesirable effects of improper motor sizing. Also, the use of such a computer system can incorporate a vast database of motor and drive units, a task that is not practical with a manual process of motor selection. In this paper, first a rationale for the use of ESs in various practical domains of decisionmaking is presented. Then, a methodology for motor selection (sizing) using an ES is outlined. Typical motor control applications and duty cycles (DCs) are presented and analysed with respect to the relevant rotational inertia and angular acceleration expressions, as required in the ES. Subsequently, a database of inertial and thermal properties of over 50 direct-current (dc) motors and gears is developed. By coupling the motor selection procedure with this database, a user-guided motor selection program is presented, which is the key constituent of the developed ES. Along with typical motor control applications and DC, this ES enables the user to create their own custom applications using custom design components such as shafts and bearings, and customized DCs by submitting any required motion profile. Details of the system implementation are given, and verification of the system performance is carried out. Even though the presented developments primarily concern dc motors, the methodology can be extended to other types of electric motors and actuators.