Different types of actuators pdf

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Download now. Related titles. Carousel Previous Carousel Next. Jump to Page. Search inside document. There are number of mechanical transducers present, some of them are 1 Bellows :- These are the elastic elements that convert the air pressure into displacement, and it is commonly used for the measurement of pressure. Some commonly used electrical transducers are 1 Potentiometers:- They convert the change in displacement into change in the resistance, which can be measured easily.

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Sourabh Raj. S shek Dhavud. Raj Mehta. XXmichxX gaming. Dalia Mohamed. Popular in Electronics. Shyanyoon Teh. SJ Manju. Jeffrey Soon. Silvian Ionescu. Aneesh Jose. Trevor Paton. Vedran Karajic. Active, Reactive Apparent power assignment student template Fall Pratik Gupta. This article nisms has shown steadily growing technological advances technically discusses the several types of actuators and in externally activated upper limb prostheses.

From among mechanisms, listing their main characteristics, applications, the actuators, advances include the use of piezoelectric and advantages and disadvantages, and the current state materials, special metal alloys, polymers, and new motor of research in the area of rehabilitation of upper limb applications, while the advances in mechanisms include functions through the use of active prostheses. Com- mechanical designs based on the anatomy of the human parisons of these devices are made with regard to the hand and improvements in the way these components are main criteria of construction and operation required combined.

These efforts are aimed at meeting the need for to achieve optimal prosthetic performance. Key Words: anthropomorphic and functional prosthetic devices that Upper limb prostheses—Actuators—Mechanisms—Myo- enable patients to carry out basic daily tasks more easily electric prostheses—Hand prostheses—Artificial hand.

Improvements in prosthetic functions, such as a ments. Well-matched actuators and mechanisms greater number of degrees of freedom DOF , easy ensure both optimal operation and greater internal control of movements, light weight, anthropomor- space inside the prosthesis to accommodate its elec- phism, and high performance, depend directly on tronic control circuits and power source.

Similarly, the is currently under construction. Composed of motors Received November ; revised August Cliquet, cording to the working principles upon which the Jr. E-mail:cliquet sel. Conventional actuator the servomotor with a reasonable output torque. The shaft assumes based on the DC direct current engine. Used in prostheses in their miniature form, periods and widths varying within limit values in they are divided into coreless DC micromotors and which each value defines a position of the output brushless DC micromotors.

Each servomotor magnets. The mechanical commutator and brushes of this finger, which consists of the proximal, medial, are made of a special metal alloy. The brush-switch and distal phalanges, moves one phalange of the set requires maintenance, which poses problems. Hydraulic actuator Brushless DC Micromotors: In contrast to the Artificial rubber micro-muscle: This is an actuator coreless DC motor, the permanent magnets are that uses hydraulic energy by transferring the located in the rotor, the armature coil is situated in mechanical energy generated by a DC motor to a the stator, and no brushes are needed to excite the fluid, using a piston and cylinder to generate a rotor.

They are also high rotation and low torque hydraulic force, which causes the pressure of motors, requiring gearboxes to set their mechanisms this fluid to rise, allowing it to drive a hydraulic in motion. The smallest models are far more compact device. Lee and Shimoyama 3 used the micropump than coreless DC micromotors, which makes it easy to supply an artificial rubber micro-muscle with to fit them into the prosthetic cavity.

Carrozza et al. The bolt and nut system con- screw-type transmissions, i. The motor-gearbox-transmission set is also placement of the artificial rubber micro-muscle to be quite small to allow it to be integrated within the controlled through stress applied to the motor, which structure of the prosthetic hand, the palm of the hand can generate 0.

This artificial micro-muscle, which con- gearbox-transmission set in the phalanges of the artificial finger. Servomotors: These consist of a DC micromotor, a reduction system, and a control system, and are characterized by their capacity to position the out- FIG. A micropump and artificial micro-muscle are shown, put shaft precisely. The reduction system provides adapted from 3. Artif Organs, Vol. The muscle can also be used as a tension sensor because of its internal pressure characteristic, which changes according to externally applied forces 3.

This system can be sufficiently lightweight to fit into a prosthesis, allowing some joints to be activated without taking up the internal space required for the control circuits and the electric power source. More- over, a compact control system can be built for the artificial rubber muscle without the use of large FIG. A rotatory piezoelectric motor is shown 5.

The use of hydraulic power in artificial muscles offers significant advantages, such as the need for little flow, which the stator, when subjected to a difference in adjustable threshold motion, high power efficiency, potential, is strained forward indirect piezoelectric recyclable actuator fluid, amplifiable force output, effect , and the end of the stator forces the rotor to and small overshoot 3.

The difficulty of producing move, causing it to rotate around its shaft in response smaller tubes to miniaturize the pneumatic muscle to the strong friction generated between the actuator lies in the fact that the force of the contraction and the rotor. These are the posite direction 5. Compared to electromagnetic characteristics that may hinder its application in motors, these actuators are small and have a strong prostheses for the implementation of several active output torque, but they are difficult to build and are joints, preventing the number of DOF from being relatively costly 5.

Figure 2 depicts a rotatory piezoelectric motor. This elliptic Piezoelectric actuators: These are based on piezo- movement is transmitted by direct contact with the electric materials that convert mechanical displace- rotor 6 , as shown in Fig.

A piezoelectric material output shaft. The magni- are superimposed to excite the piezoelectric ceramic tude of this effect is proportional to the applied ring itself 6. Alternatively, when an electric field is applied These motors use mechanical vibrations in the to a piezoelectric material, it produces a mechanical ultrasonic region above 20 kHz as their activating displacement 4.

This actuator can be controlled by a flow of elec- tric current that passes through the strained metal alloy. The heat derives from the passage of the elec- tric current through the alloy itself or, depending on the alloy, from the use of resistors placed adjacent to the actuator, which cause the alloy to contract and return to its original shape.

These alloys offer several advantages, i. These alloys also provide high grasping strength. The dis- advantages of these alloys applied as prosthesis actu- FIG. A moving stator and rotor are shown, adapted from 8. However, this motor wire for large strains 5 ; and their nonlinear effect, presents a few disadvantages, i.

One strand of 0. Pons et al. There are various types of polymeric converts heat into mechanical displacement through gels differing in composition and in the type of stim- thermo-elastic transformation. When an alloy is ulus used to cause contraction. Three of these gels are heated to a temperature above that of transition, the PAA polyacid acrylic , which is stimulated by the material passes from the martensitic to the austenitic change in pH; NIPA N-isopropylacrylamide , which phase. Thus, SMA possesses These characteristics render polymeric gels pro- shape memory, i.

The tension in both pairs of cables space. Sakamoto et al. This material would Based on their recent study 5 , Cunha et al. This way to implement prostheses for more agile upper mechanism has three DOF and is composed of three limbs with more DOF, a significant reduction in mass, segments or phalanges, each driven by a servomotor, and easy control.

This alternative material has a high as illustrated in Fig. Some The pulleys are connected to the motor-gearbox are articulated, analogous to a human finger, and can output shaft but not coupled to it; hence, it is the cou- be used to move the cable articulations or the actu- pling system that joins pulley and shaft, causing the ator directly in the mechanism.

When a finger segment has Transmission through cables assumed the desired position, the blocking system CT Arm 1 or 2: This mechanism is composed of locks the respective pulley to hold the segment in segments linked in series by means of joints.

The position, allowing the shaft to move freely. In the joints are moved by means of cables tendons con- inverse movement, the blocking system releases the nected to the pulleys, which are fixed to the segments. Based on the movement of the means of cables connected directly to the corre- artificial finger, the distal joint has only one pulley sponding mechanisms.

The same cables provide the prosthetic hand with several DOF, system is used for the proximal phalange. Its In the mechanism proposed by Ma et al. A multiple transmission mechanism is shown. This device, which is discussed by Carrozza et al. The metacarpophalangeal and interphalangeal proximal joints each have a linear actuator and a slider crank mechanism see Fig. The reduced dimensions and mass of this mecha- nism and the linear actuators enable them to fit in the palm and the proximal phalange, which allows FIG.

Figure 5 illus- trates this actuator and its three basic operation systems. Direct transmission: Slider crank. The design of this finger is based on biomechatronic concepts and it is intended to obtain an anthropomorphic prosthesis. This finger possesses three segments phalanges , which are moved by means of a shaft articulated to FIG.

This slider crank mechanism has a stem connecting the the segment. Accomodation mechanism AM. The mechanism consists basically of a motor, a FIG.