Actuation

The present work aims at providing a wide view of the actuators used in automation and robotics. The idea was to describe most of the actuation solutions without entering too deep into details, offering a general panorama of the trends that are followed in robotics to address several problems. Due to their large diffusion, electromechanical actuators will be discussed extensively, covering several topics from constructive specifications to elementary control problems. This chapter starts with an introduction on descriptive scheme of an actuation stage. Control blocks and feedback types are illustrated to offer to the reader the possibility of identifying the different structures composing electronic and mechanical counterparts. Working principles for actuations are then described and reported to classify the different technological approaches. AC and DC motors are presented and illustrated. Dynamics of DC motor is discussed in details and problems related to the presence of reduction stage and load are reported. Introduction on compliant actuation is also included due to the emerging field in robotics for human machine interaction. Series elastic and variable stiffness actuation solutions are mentioned. Piezoelectric effect and the widely used constructive solutions are depicted highlighting the obtained specifications with the different architectures of piezoelectric elements. Shape memory alloys and polymeric actuator are also introduced highlighting their dynamic behavior and the most famous applications in the robotic field.