Actuators and Their Applications

Fundamentals, Principles, Materials, and Emerging Technologies

Rajender Boddula, Abdullah M. Asiri, Rajender Boddula, Abdullah M. Asiri

• Publisher: Wiley-Scrivener
• Year: 2020
• ISBN:
  9781119662754
• Edition: 1
• Topic: Tecnologia e ingegneria
• Subtopic: Ingegneria meccanica

As demand has increased for new types of equipment that are more suited to the ever-evolving world of industry, demand for both new and traditional types of actuators has soared. From automotive and aeronautical to biomedical and robotics, engineers are constantly developing actuating devices that are adapted to their particular needs in their particular field, and actuators are used in almost every field of engineering that there is.

This volume not only lays out the fundamentals of actuators, such as how they operate, the different kinds, and their various applications, but it also informs the engineer or student about the new actuators that are being developed and the state-of-the-art of actuators. Edited and written by highly experienced and well-respected engineers with a deep understanding of their subject, there is no other volume on actuators that is more current or comprehensive.

Whether as a guide for the latest innovations in actuators, a refresher reference work for the veteran engineer, or an introductory text for the engineering student, this is a must-have for any engineer's or university's library. Covering the theory and the practical applications, this breakthrough volume is a "one stop shop" for any engineer or student interested in actuators.

1
Piezoelectric Actuators and Their Applications

N. Suresh Kumar¹*, R. Padma Suvarna¹, K. Chandra Babu Naidu^2†, S. Ramesh², M.S.S.R.K.N. Sarma², H. Manjunatha³, Ramyakrishna Pothu⁴ and Rajender Boddula⁵

¹Department of Physics, JNTUA, Anantapuramu, India

²Department of Physics, GITAM Deemed to be University, Bangalore, India

³Department of Chemistry, GITAM Deemed to be University, Bangalore, India

⁴College of Chemistry and Chemical Engineering, Hunan University, Changsha, China

⁵CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, China

Abstract
Piezoelectric actuators (PEAs) are a type of microactuators which mainly use the inverse piezoelectric effect to produce small displacement at high speed by applying voltage. This chapter includes the detailed discussion on piezoelectric actuators in the direction of industrial benefits. In addition, the classification of piezoelectric actuators is made. Especially, the piezoelectric actuators showed the MEMS (microelectromechanical systems) applications at larger extent. We elaborated different piezoelectric materials such as lead and lead zirconium-based compounds for actuator applications. In view of this, few parameters like memory, domain rotation, etc., are considered for justifying the actuator applications. The importance of these actuators towards robotics is also elucidated.

Keywords: Actuators, piezoelectric materials, hydraulic actuator, journal bearings, machines

1.1 Introduction

A part of a device which moves or controls the mechanism is called an actuator. Example is an electric motor which converts a control signal to mechanical action. An actuator is one which converts energy into motion. This energy may be hydraulic, pneumatic, electric, thermal, mechanical, or even human power [1]. Whenever a control signal is received, actuator converts the energy of the signal into mechanical motion. The control system may be a fixed mechanical/electronic system or a software-based printer device/robot. Based on the type of control system or energy, actuators are classified into different types which are hydraulic, pneumatic, electrical, mechanical actuators, etc.

1.2 Types of Actuators

A hydraulic actuator uses hydraulic power for the mechanical process. Here, the output will be a linear, rotatory, or oscillatory motion. In hydraulic systems, energy is transmitted with the help of pressure of fluid in a sealed system. It has advantages like efficient power transmission, accuracy, and also flexible in maintenance. Usage of these systems is safe in chemical plants and mines as they do not produce any sparks. Here, leakage of the fluid is the major drawback. Because, once the fluid leaks, it may catch fire or leads to serious injuries when it bursts [2]. Examples are brakes in cars/trucks, wheelchair lifts, hydraulic jacks, and flaps on air-crafts, etc. Figure 1.1 represents one type of hydraulic actuator.

A pneumatic actuator rotation is shown in Figure 1.2. It uses energy in the form of compressed air at high pressure to produce motion. This actuator is mainly advisable in main engine controls for swift starting and stopping. These actuators are economical, lightweight, less maintenance, and simple when compared to other actuators. The disadvantage with this actuator is application-specific that is an actuator sized for a specific purpose cannot be used for other applications [3, 4].

An electric actuator uses a motor for converting electrical energy into mechanical torque. This is used in multi-turn valves. Figure 1.3 shows different types of electric actuators. As there is no involvement of either fossil fuels or oils these actuators are the cleanest and easily available ones [5, 6]. Another type of actuator is supercoiled polymer (SCP) or twisted and coiled polymer (TCP) actuators which use electric power for actuating. These are made up of silver-coated nylon and gold and appear helical like a splicing. These are constructed by twisting like nylon thread such as fishing line. They serve as bicep muscle to control the motion of arms in robots. Because of electrical resistance, electrical energy gets converted into thermal energy also called Joule heating. When the temperature of this actuator is increased due to joule heating, counteraction of the polymer takes place resulting in contraction of the actuator [7].

Figure 1.1 Hydraulic actuator.

Figure 1.2 Pneumatic actuator.

Figure 1.3 Electric actuators.

Mechanical actuator converts one type of motion into another like rotatory into linear. Example for this type is rack and pinion. This type of actuators depends on constitutional components like gears and rails, pulleys, and chairs. In order to use actuators in the fields of agriculture for fruit harvesting and biomedicine in robotics soft actuators are being developed. Because of amalgamation of microscopic changes at the basic (molecular) level into a macroscopic distortion, soft actuators generate flexible motion. Figure 1.4 represents mechanical actuator.

Electromechanical actuators are nothing but mechanical actuators in which the control signal is given by an electric motor which converts the rotatory motion into linear displacement. These actuators work on the inclined plane concept. The required inclination is provided by the threads of a lead screw. It acts as a ramp and converts small rotational force into linear displacement. Based on parameters like operation, speed increased load capacity, mechanical efficiency, etc., different EM actuators are designed which are shown in Figure 1.5. The common design consists of a lead screw passing through the motor. The lead nut is the only moving part while the lead screw remains fixed and non-rotating. When the motor rotates, the lead screw either extends outwards or retracts inwards. By using alternating threads on the same shaft, different actuators are designed. Actuators begin on the lead screw and provide a higher adjustment capability between the starts and the nut thread area of contact, influencing the extension speed and load capacity.

The density of motion of the nut is determined by the lead screw and by coupling the linkages to the nut. Usually, in many cases, screw is connected to the motor. Based on the amount of the loads, the actuator is expected to move various motors like dc brush, stepper, induction motors, etc. Coming to its advantages, the person handling this actuator can have complete control over the movement. They can control the velocity and position accurately without switching off the device or when the device is in running state, the force and motion profile can be changed by changing its software. These actuators consume power only when they are in operation. Low maintenance, high efficiency, and being environmentally friendly make these actuators a potential candidate in hazardous areas. These are used in packaging, food, energy process control, construction, and automation indust...