Linear actuator; Modelling; Numerical simulation; Piezoelectric motor; Principle of inertia; Transducer; Ultrasonic linear motor (ULM) Actuators; Computer simulation; Linear actuators; Linear motors; Models; Piezoelectric motors; Piezoelectricity; Transducers; General structures; Optimal performance; Precise positioning; Principle of inertia; Reliable models; Ultrasonic linear motor; Electric machine theory