A mathematical dynamic model is derived for the compliant constant-force mechanism, based on the pseudo-rigid-body model simplification of the device. The compliant constant-force mechanism is a slider mechanism incorporating large-deflection beams, which outputs near-constant-force across the range of its designed deflection. The equation of motion is successfully validated with empirical data from five separate mechanisms, comprising two configurations of compliant constant-force mechanism. The dynamic model is cast in generalized form to represent all possible configurations of compliant constant-force mechanism. Deriving the dynamic equation from the pseudo-rigid-body model is useful because every configuration is represented by the same model, so a separate treatment is not required for each configuration. An unexpected dynamic trait of the constant-force mechanism is discovered: there exists a range of frequencies for which the output force of the mechanism accords nearer to constant-force than does the output force at static levels.

This thesis presents research on the force and deflection behavior of beams with rectangular cross-sections undergoing lateral torsional buckling. The large 3-D deflection path of buckling beam tips was closely approximated by circular arcs in two planes. A new chain algorithm element was created from pseudo-rigid-body segments and used in a chain calculation that accurately predicted the force deflection relationship of beams with large 3-D deflections.

No description available.

The Bistable Aerial Platform (BAP) has been developed in order to further enlarge the repertoire of devices available at the microscale. This novel device functions as a switch in that its platform can lock in two positions, up or down. Herein, it will be examined and explained, but a true understanding of its workings requires a better understanding of its compliant constituent parts. The Helico-Kinematic Platform (HKP), which serves as an actuator for the BAP, is currently under investigation by another researcher and will be merely touched upon here. The focus, therefore, will rest on the analysis of the Quadrantal Bistable Mechanism (QBM), the principle component of the BAP. A preliminary pseudo-rigid-body model, an aid for the understanding of compliant mechanisms, will also be examined for the QBM. The models developed for these two devices, the HKP and QBM, can later be combined to form a full model of the Bistable Aerial Platform.

We have designed and examined a compliant knee mechanism that may offer solutions to problems that exist for infants and toddlers who are just learning to walk. Pediatric prosthetic knees on the market today are not well designed for infants and toddlers for various reasons. Children at this age need a prosthetic that is light in weight, durable, and stable during stance. Of the eleven knees on the market for children, all but three are polycentric or four-bar knees, meaning they have multiple points of movement. Polycentric knees are popular designs because they offer the added benefit of stable stance control and increased toe clearance, unfortunately this type of knee is often too heavy for young children to wear comfortably and is not well suited for harsh environments such as sand or water, common places children like to play. The remaining three knees do not offer a stance control feature and are equally vulnerable to harsh environments due to ball bearing hinges. Compliant mechanisms offer several design advantages that may make them suitable in pediatric prosthetic knees -- light weight, less susceptible to harsh environments, polycentric capable, low part count, etc. Unfortunately, they present new challenges that must be dealt with individually. For example compliant mechanisms are typically not well suited in applications that need adjustability. This problem was solved by mixing compliant mechanism design with traditional mechanism design methods. This paper presents a preliminary design concept for a compliant pediatric prosthetic knee. The carbon fiber composite spring steel design was first built and then evaluated using Finite Element Analysis. The prototype's instant center was plotted using the graphical method. From our analysis position, force and stress information was gathered for a deflection up to 120 degrees. The instant centers that were plotted indicate that the knee has good potential in offering adequate stability during stance.

No description available.

Existing classes of centrifugal clutch concepts were reviewed. The pseudo-rigid-body model (PRBM), rigid-body replacement synthesis, force-deflection analysis, compliance potential evaluation, and compliant concept evaluation were used to develop effective new centrifugal clutch concepts. These methods helped develop and model four novel compliant centrifugal clutch designs, model two existing designs, and identify a concept with excellent potential for low-cost centrifugal clutch applications. This concept, the floating opposing arm (FOA) clutch, doubles the torque capacity metric relative to existing compliant designs. Torque and engagement speed models for this clutch were developed and verified against four prototype clutches. Additional novel designs devel-oped through this work have lower torque capacities, but also show good potential because of other unique characteristics. All of the designs were prototyped and tested to measure their torque-speed relationships.

This work discusses the dynamic predictions of compliant mechanisms using the Pseudo-Rigid-Body model (PRBM). In order to improve the number of mechanisms that can be modeled, this research develops and identifies several key concepts in the behavior of beam segments where both ends are fixed to a rigid body (fixed-fixed flexible segments). A model is presented, and several examples are discussed. The dynamic behavior of several compliant segments is predicted using the PRBM and the results are compared to finite element analysis and experimental results. Details are presented as to the transient behavior of a typical uniform rectangular cross section beam. The results of this study are extended and applied to compliant planar mechanisms. It is shown by comparison with finite element analysis and experimental results that the PRBM is a good model of the physical system's dynamic behavior. The method is also demonstrated for use with compliant microelectromechanical (MEMS) systems.

No description available.

Implants used in lumbar spinal fusion and lumbar total disc replacement procedures have improved substantially over the years, however, the opportunity remains to improve either the adjustability, durability, motion, or minimally invasive characteristics which could aid in achieving optimal surgical outcomes. It is hypothesized that the inherent advantages of compliant mechanisms specifically Deployable Euler Spiral Connectors (DESCs) and a new mechanism known as the interior contact aided rolling element (I-CORE) are well suited for each of these applications and will be explored and utilized as the basis of these proposed designs. By addressing these challenges, the research endeavors to improve patient outcomes in both lumbar fusion and lumbar disc replacement procedures and advance the field of lumbar spinal surgery. Expandable cages, ideal for minimally invasive lumbar fusion, can be implanted in a compact form and then expanded. Differences in shape, size, material, and adjustability of cages are often overlooked. A systematic review revealed that design variations, such as rectangular titanium cages with medial-lateral and vertical expansion, and those with adjustable lordosis, are linked to better patient outcomes. Deployable Euler Spiral Connectors were leveraged to create an expandable fusion cage while also including recommended features from the systematic review. Finite element analysis, benchtop mechanical testing, and validation via in vitro device insertion were performed. The design highlights the potential of compliant mechanism devices for advancing minimally invasive lumbar fusion. A new compliant mechanism called the Interior Contact-Aided Rolling Element (I-CORE) is described and modeled using the pseudo-rigid-body method. The new mechanism included two degrees of rotational freedom at a tailorable stiffness combined with tailorable vertical compressibility and a mobile center of rotation. The model is outlined and validated using FEA and benchtop mechanical testing. The model is shown to be sufficiently accurate for initial design work. A novel motion preserving spinal implant using the I-CORE mechanism is described. Prototypes were manufactured from Ti6Al4V and validated using benchtop mechanical and in vitro biomechanical testing. Properties including compressive, shear, and torsional stiffness were quantified. The device was tested for expulsion and subsidence forces, showing results comparable to current devices. In vitro testing with human cadaveric lumbar segments demonstrated that the compliant interbody device maintained robust compressive, shear, and torsional strength, closely replicating the motion quality of intact segments when properly placed.