Stuart T. Smith

Bio: Stuart T. Smith is an academic researcher from University of North Carolina at Charlotte. The author has contributed to research in topics: Actuator & Metrology. The author has an hindex of 29, co-authored 141 publications receiving 3233 citations. Previous affiliations of Stuart T. Smith include Griffith University & University of North Carolina at Chapel Hill.

Flexures: Elements of Elastic Mechanisms

Abstract: Introduction: Advantages and Disadvantages of Flexures. Goals of Flexure Design. Essentials: Basic Elasticity. Behavior of Materials. Fatigue. Bending of Symmetric Beams. Rigid Body Dynamics: Linear Systems Theory. Vibrations and Natural Frequencies of Continuous Systems. Flexure Elements: Leaf Type Springs. Notch Hinge. Two Axis Hinges. The Four Bar Link. Flexure Systems: General Model for Dynamics of planar Flexures. Hinges of Rotational Symmetry: The Disc Coupling. Rotationally Symmetric Leaf Type Hinge. The Bellows as a Flexure Element. Levers. Manufacturing and Assembly Considerations: Machining and Heat Treatment of Some Common Flexure Materials.

Elliptical flexure hinges

Abstract: This paper presents closed form equations based on a modification of those originally derived by Paros and Weisbord in 1965, for the mechanical compliance of a simple monolithic flexure hinge of elliptic cross section, the geometry of which is determined by the ratio e of the major and minor axes. It is shown that these equations converge at e=1 to the Paros and Weisbord equations for a hinge of circular section and at e ⇒∞ to the equations predicted from simple beam bending theory for the compliance of a cantilever beam. These equations are then assessed by comparison with results from finite element analysis over a range of geometries typical of many hinge designs. Based on the finite element analysis, stress concentration factors for the elliptical hinge are also presented. As a further verification of these equations, a number of elliptical hinges were manufactured on a CNC milling machine. Experimental data were produced by applying a bending moment using dead weight loading and measuring subsequent ...

Giant magnetoresistance-based eddy-current sensor

Abstract: The purpose of this paper is to introduce a new eddy-current testing technique for surface or near-surface defect detection in nonmagnetic metals using giant magnetoresistive (GMR) sensors. It is shown that GMR-based eddy-current probes are able to accurately detect short surface-breaking cracks in conductive materials. The self-rectifying property of the GMR sensor used in this study leads to a simplified signal conditioning circuit, which can be fully integrated on a silicon chip with the GMR sensor. The ability to manufacture probes having small dimensions and high sensitivity (220 mV/mT) to low magnetic fields over a broad frequency range (from dc up to 1 MHz) enhances the spatial resolution of such an eddy-current testing probe. Experimental results obtained by scanning two different probes over a slotted aluminum specimen are presented. General performance characteristics are demonstrated by measurements of surface and subsurface defects of different sizes and geometries. Dependence of the sensor output on orientation, liftoff distance, and excitation intensity is also investigated.

Foundations of ultraprecision mechanism design

Abstract: Introductory mechanics fundamental concepts in precision design flexure design for positioning and control drive couplings and the mechanics of contact actuators and sensors for controlled displacements materials selection in precision mechanical design sideways for long range precision motion the dynamics of instrument mechanisms.

Design and assessment of monolithic high precision translation mechanisms

Abstract: Crucial to the success of devices such as the scanning tunnelling microscope is the availability of translation mechanisms of very high precision. Elastic design is a natural approach to this problem and here one family of such devices, mechanisms cut from a monolith and using 'web hinges', is examined in detail. Simple design rules, derived in part from finite-element analysis, are given and manufacturing tolerances considered. It is demonstrated that the drive system can cause significant parasitic motion even in very stiff systems and so a non-contact force transducer utilising a solenoid and permanent magnet is investigated. Experimental investigation confirms that even with very routine, low-cost manufacturing methods the combination of these devices can produce 'slideways' with subnanometer out-of-plane inaccuracies.

Soft Actuators for Small-Scale Robotics.

Abstract: This review comprises a detailed survey of ongoing methodologies for soft actuators, highlighting approaches suitable for nanometer- to centimeter-scale robotic applications. Soft robots present a special design challenge in that their actuation and sensing mechanisms are often highly integrated with the robot body and overall functionality. When less than a centimeter, they belong to an even more special subcategory of robots or devices, in that they often lack on-board power, sensing, computation, and control. Soft, active materials are particularly well suited for this task, with a wide range of stimulants and a number of impressive examples, demonstrating large deformations, high motion complexities, and varied multifunctionality. Recent research includes both the development of new materials and composites, as well as novel implementations leveraging the unique properties of soft materials.

High performance ferroelectric relaxor-PbTiO3 single crystals: Status and perspective

Abstract: Ferroelectrics are essential components in a wide range of applications, including ultrasonic transducers, sensors, and actuators. In the single crystal form, relaxor-PbTiO3 (PT) piezoelectric materials have been extensively studied due to their ultrahigh piezoelectric and electromechanical properties. In this article, a perspective and future development of relaxor-PT crystals are given. Initially, various techniques for the growth of relaxor-PT crystals are reviewed, with crystals up to 100 mm in diameter and 200 mm in length being readily achievable using the Bridgman technique. Second, the characterizations of dielectric and electromechanical properties are surveyed. Boundary conditions, including temperature, electric field, and stress, are discussed in relation to device limitations. Third, the physical origins of the high piezoelectric properties and unique loss characteristics in relaxor-PT crystals are discussed with respect to their crystal structure, phase, engineered domain configuration, macr...

Leadless tissue stimulation systems and methods

Abstract: Systems including an implantable receiver-stimulator and an implantable controller-transmitter are used for leadless electrical stimulation of body tissues. Cardiac pacing and arrhythmia control is accomplished with one or more implantable receiver-stimulators and an external or implantable controller-transmitter. Systems are implanted by testing external or implantable devices at different tissue sites, observing physiologic and device responses, and selecting sites with preferred performance for implanting the systems. In these systems, a controller-transmitter is activated at a remote tissue location to transmit/deliver acoustic energy through the body to a receiver-stimulator at a target tissue location. The receiver-stimulator converts the acoustic energy to electrical energy for electrical stimulation of the body tissue. The tissue locations(s) can be optimized by moving either or both of the controller-transmitter and the receiver-stimulator to determine the best patient and device responses.