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H. Harry Asada. Torres, James, Ph. D. Massachusetts Institute of Technology. Massachusetts Institute of Technology. Dept. of Mechanical Engineering. Massachusetts Institute of Technology. Department of Mechanical Engineering 2012-11-19T19:20:56Z 2012-11-19T19:20:56Z 2012 2012 http://hdl.handle.net/1721.1/74948 816567882 Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. Cataloged from PDF version of thesis. Includes bibliographical references (p. 55-56). Due to the limited displacement of piezoelectric stack actuators, common practice is to use some form of displacement amplification mechanism. An efficient, heavy-duty displacement amplification mechanism for piezoelectric stack actuators is presented in this thesis. The displacement amplification gain is increased by a factor of more than 100 in a single stage by using a buckling mechanism combined with a novel rolling contact design. Unlike traditional flexure-type monolithic mechanisms, which are accurate but inefficient and fragile, the new mechanism consists of all rolling contact couples, providing high stiffness, durability and energy efficient characteristics. Furthermore, a new design of pre-loading mechanism using shape memory alloy doubles the possible cyclic work output and provides a desirable restoring force for constraining the rolling contact mechanism stably and efficiently. This mechanism is intended to be interfaced with a sinusoidal gear cam that acts as the load. The dynamics of the system are derived and are shown to be fifth order. Due to the significantly nonlinear amplification caused by the buckling phenomenon and the gear, the dynamics are run in simulation to gain insight into the dynamic performance of the actuator. There is shown to be an optimal speed at which to run the actuator to maximize the possible power output. Furthermore, due to the simple binary control significant benefits are achieved by varying the control timing based on the velocity to ensure the force and velocity of the output are in phase. Finally, a prototype was constructed to compare to the static model. The prototype had a peak to peak displacement of 6.8 mm, an amplification of over 150, and produced a peak charged force of 56 Newtons. by James Torres. S.M. 56 p. eng Massachusetts Institute of Technology M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 Mechanical Engineering. Large gain amplification mechanism for piezoelectric actuators utilizing a rolling contact joint Thesis application/pdf false Publication unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="35f149e7-0013-4750-8d70-4cd1def534ca"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Language>eng</Language> <Title>Large gain amplification mechanism for piezoelectric actuators utilizing a rolling contact joint</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2012</PublicationDate> <Authors> <Author> <DisplayName>Torres, James, Ph. D. Massachusetts Institute of Technology.</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>http://dspace.mit.edu/handle/1721.1/7582</License> <Keyword>Mechanical Engineering.</Keyword> <Abstract>Due to the limited displacement of piezoelectric stack actuators, common practice is to use some form of displacement amplification mechanism. An efficient, heavy-duty displacement amplification mechanism for piezoelectric stack actuators is presented in this thesis. The displacement amplification gain is increased by a factor of more than 100 in a single stage by using a buckling mechanism combined with a novel rolling contact design. Unlike traditional flexure-type monolithic mechanisms, which are accurate but inefficient and fragile, the new mechanism consists of all rolling contact couples, providing high stiffness, durability and energy efficient characteristics. Furthermore, a new design of pre-loading mechanism using shape memory alloy doubles the possible cyclic work output and provides a desirable restoring force for constraining the rolling contact mechanism stably and efficiently. This mechanism is intended to be interfaced with a sinusoidal gear cam that acts as the load. The dynamics of the system are derived and are shown to be fifth order. Due to the significantly nonlinear amplification caused by the buckling phenomenon and the gear, the dynamics are run in simulation to gain insight into the dynamic performance of the actuator. There is shown to be an optimal speed at which to run the actuator to maximize the possible power output. Furthermore, due to the simple binary control significant benefits are achieved by varying the control timing based on the velocity to ensure the force and velocity of the output are in phase. Finally, a prototype was constructed to compare to the static model. The prototype had a peak to peak displacement of 6.8 mm, an amplification of over 150, and produced a peak charged force of 56 Newtons.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>