On the Extraction of Kinematic Behavior From Optimal Compliant Topologies With Application to Number Synthesis of Linkages

This paper presents a number of systematically designed compliant topologies and discusses how the intrinsic kinematic behavior can be extracted from them. This is then applied to the number synthesis of linkages. Many techniques developed for number synthesis of linkages enumerate numerous possible kinematic chains, but few can select the best configuration among them. A systematic computational approach that can select the best configuration based on kinetostatic design specifications is presented here. This is a serendipitous result that transpired when two well-developed design techniques for compliant mechanisms were combined. A number of examples with non-intuitive design specifications are included to illustrate the new approach to number synthesis. The examples also illustrate that the kinematic behavior is aptly captured in the elastic mechanics-based topology optimization method to compliant mechanism design. Dimensional synthesis is also accomplished in the same procedure, which is an added benefit of this approach.

Posture Prediction Versus Inverse Kinematics

Inverse kinematics is concerned with the determination of joint variables of a manipulator given its final position or final position and orientation. Posture prediction also refers to the same problem but is typically associated with models of the human limbs, in particular for postures assumed by the torso and upper extremities. There has been numerous works pertaining to the determination and enumeration of inverse kinematic solutions for serial robot manipulators. Part of these works have also been directly extended to the determination of postures for humans, but have rarely addressed the choice of solutions undertaken by humans, but have focused on purely kinematic solutions. In this paper, we present a theoretical framework that is based on cost functions as human performance measures, subsequently predicting postures based on optimizing one or more of such cost functions. This paper seeks to answer two questions: (1) Is a given point reachable (2) If the point is reachable, we shall predict a realistic posture. We believe that the human brain assumes different postures driven by the task to be executed and not only on geometry. Furthermore, because of our optimization approach to the inverse kinematics problem, models with large number of degrees of freedom are addressed. The method is illustrated using several examples.

Metamodeling Development for Vehicle Frontal Impact Simulation

Response surface methods or metamodels are commonly used to approximate large engineering systems. This paper presents a new metric for evaluating a response surface method or a metamodeling technique. Five response surface methods are studied: Stepwise Regression, Moving Least Square, Kriging, Multiquadratic, and Adaptive and Interactive Modeling System. A real world frontal impact design problem is used as an example, which is a complex, highly nonlinear, transient, dynamic, large deformation finite element model. The optimal Latin Hypercube Sampling method is used to distribute the sampling points uniformly over the entire design space. The Root Mean Square Error is used as the error indicator to study the accuracy and convergence rate of the metamodels for this vehicle impact analysis. A hybrid approach/strategy for selecting the best metamodels of impact responses is proposed.

A Study on Shape Optimization Using Affine Transformation

This paper presents a new method to determine an optimal shape using affine transformation which is used in the field of Computer Aided Design (CAD), linear programming, and etc. We use affine transformation as coordinate transformation. Affine transformation is a linear transformation, so that shapes transformed must be linearly. Shape optimization of a inclined beam for example, we can deal with in the following manner. We define a simple cantilever beam first in initial design domain, and calculate an optimal shape. Then we use affine transformation remaining with optimal shape calculated in simple design domain and get to an optimal shape of the inclined beam. To compare with an optimal shape obtained by our proposed method, we calculate an optimal shape directly by conventional method in the same design domain after coordinate transformation. We show that affine transformation plays a role as scaling to structural optimization by finite element method and that necessary and sufficient conditions between design variables and shape transformation matrix may exist to get an exact optimal shape. We treat some numerical examples by our proposed method. In numerical examples, we consider shape optimization of inclined cantilever beam for simplicity. We show that some stepwise linear optimal shapes could be expressed from an optimal shape of a simple cantilever beam by using affine transformation. Optimal shape calculated by our method can obtain easily and speedy. Through some numerical examples, we could examine effectiveness of our proposed method.

Investigation of Compliant Centrifugal Clutch Designs

Compliant centrifugal clutches can make centrifugal clutches feasible in cost and weight sensitive applications. This paper introduces new configurations of compliant centrifugal clutches, proposes pseudo-rigid-body models for their analysis, and presents torque capacity results for several prototypes. The results are also compared to those obtained from compliant centrifugal clutch designs already commercially available. While all four new clutch designs compare favorably to commercially available clutch configurations, the floating opposing arm (FOA) clutch demonstrated the highest torque capacity of all the configurations.

Development of 5mm-Trocar Laparoscopic Forceps With Mechanical Force Feedback

In minimally invasive surgery, surgeons are deprived of direct contact with the patient’s tissue. All manipulation, including diagnostic palpation, is carried out via long and slender instruments, inserted through small trocars inserted in the skin. Due to poor mechanical characteristics, such as internal friction, backlash, and non-linear force transmission functions, current instruments allow only marginal force feedback. Consequently, surgeons lack a major source of vital information, resulting in reduced safety and grasping forces far greater than necessary. Previous research lead to the design of a 10mm-trocar grasper with low friction and an outstanding force transmission characteristic. The present study was conducted to develop this prototype into a clinically applicable instrument which can be used in 5mm-trocar therapy, by redesigning the mechanism while maintaining the excellent mechanical characteristics. This resulted in a clinical prototype, still according the patented rolling link design but in a different embodiment, now also matching the additional specifications. Mechanical testing showed that the mechanical efficiency of the 5mm-trocar version is as high as in the original version. The 5-mm-version will now be used for further optimization and clinical testing.

An Efficient Algorithm for Circular Blending of Edges

This paper describes a method for constructing circular blends using geometric tools. The algorithm presented in this paper is based on marching along a characteristic direction on the tangent plane to the Voronoi surface of the two surfaces being considered for blending. Starting from any point on the edge to be blended, the algorithm converges to the spine curve. The characteristic direction of marching lies on the plane containing the points in assignment and the tangent plane to the Voronoi surface. The spine curve generation algorithm presented in this paper, does not require computing offsets of surfaces or an explicit evaluation of surface-surface intersection (SSI). The algorithm presented is computationally simple and fast, and can be used for constant and variable radius circular blending of surfaces, each of which is G2 continuous. The algorithm can also be used to obtain the surface-surface intersection curve by setting the radius of blend to zero.

A Meta-Object Based Approach to Finite Element Modeling

With the integration of CAD and FEA software packages, design engineers who are not skilled in finite element analysis are performing finite element modeling and analysis. Furthermore, in the analysis of a system, engineers often make numerous modeling simplifications and analysis assumptions depending on the trade-off between cost, accuracy, precision or other engineering analysis objectives. Thus, reusability or interoperability of engineering analysis models is difficult and often impractical due to the wealth of knowledge involved in the creation of such models and the lack of formal methods to codify and explicitly represent this critical modeling knowledge. Most institutions and organizations have started documenting these simplifications and assumptions, making them understandable for the other engineers within the organization. However, this does not allow a seamless exchange of data or interoperability with other analysis models of similar or dissimilar nature. This plays a very important role in today’s market, which is moving away from the traditional make-to-stock production model to a build-to-demand model. We address these issues in this paper by adopting and extending the computer science concept of meta-object, and applying it in novel ways to the domain of FEA and the representation of finite element modeling knowledge. We present a taxonomy for engineering models that aids in the definition of the various object analysis classes. A simple beam analysis example, followed by a more realistic injection-molded part example. The latter example involves injection-mold filling simulation, thermal cooling, and part ejection analyses which are subclasses for a generic manufacturing analysis meta-object class. Prototype implementations of automated support for this meta-object approach to finite element modeling is in progress.

Product Variety Optimization: Simultaneous Optimization of Module Combination and Module Attributes

This paper proposes a simultaneous optimization method for both module combination and module attributes of multiple products. As manufacturing competition has become restricted with high profitability and external constraints, simultaneous design of multiple products, which is called product variety design etc., becomes an important strategy. System-based optimal design paradigm is expected to be essential to rationalize such practices, since design for product variety is more complicated than one for a single product. Toward such a direction, we configure an optimization method for both module combination and module attributes across multiple products. The optimization method hybridizes a genetic algorithm, a mixed-integer programming method with a branch-and-bound technique, and a constrained nonlinear programming method, i.e., a successive quadratic programming method. In its optimization process, the first optimizes the combinatorial pattern of module commonality and similarity among different products, the second optimizes the directions of similarity on scale-based variety, and the third optimizes the continuous module attributes under the others. Finally it is applied to the simultaneous design problem of multiple airplanes to demonstrate its validity and effectiveness.

Computer Assisted Navigation Systems for Hip and Knee Reconstructive Surgery: Evaluation of Traditional Surgical Technique

In this paper we describe a surgical navigation system named HipNav (Hip-Navigation) for THR and KneeNav (Knee-Navigation) for TKR with an emphasis on using these systems as a real time intraoperative measurement tool (these enabling technologies are the surgical toolbox of the future). This approach will permit the direct comparison of patient outcomes with measurable surgical techniques.