bluuebunny/crossref_metadata_2025 huggingface dataset:
Crank-Slider With Spring Constant Force Mechanism
Authors: Frischknecht Bart D. , Howell Larry L. , Magleby Spencer P.
Published: April 2009

This paper explores the development and performance of new constant-force compliant mechanisms that involve the addition of a translational spring element to slider-crank constant force mechanisms. The translational spring element has the additional requirement that, similar to a slider, it resists off-axis loads sufficiently to permit translation along only one axis. Geometric and energy storage parameters have been determined by optimization for five classes of mechanisms. The results of the optimization are values for geometric and energy storage parameters for each mechanism class for various levels of the translational spring parameter and various levels of constant-force behavior. The new configurations experience decreasing performance with increasing translational spring stiffness. The potential to implement a translational spring that also acts as a slider link provides the motivation for the new configurations. Such a spring would have the potential to completely remove friction from the mechanism and provide a constant-force solution that could replace current solutions such as hydraulic or pneumatic devices. The new configurations also have the potential to be manufactured as one piece or in layers, opening up new arenas for compressive constant-force mechanisms. Prototyping and testing of one of the new configurations are included as an example to demonstrate the use of the behavioral model.
A Dual Stage Planar Cable Robot: Dynamic Modeling and Design of a Robust Controller With Positive Inputs
Authors: Oh So-Ryeok , Mankala Kalyan , Agrawal Sunil K. , Albus James S.
Published: April 2009

Cable robots have been extensively used for loading and unloading of cargo in shipping industries. A novel six-degree of freedom two-stage cable robot has been proposed by NIST for skin-to-skin transfer of cargo. In this paper, we look at a planar version of this two-stage cable robot. The disturbance motion from the sea is considered while modeling the dynamics of robot. The problem of robust control of the end-effector in the presence of unknown disturbances, along with maintaining positive tensions in the cables, is tackled by using the idea of redundancy. Simulation results show the effectiveness of the control strategy.
Analytical and Experimental Analysis of a Precision Positioning Actuator System
Authors: Gullicks Jason G. , Semke William H.
Published: April 2009

An innovative flexure design concept is developed that involves the use of composite materials with bonded piezoelectric actuators to create a “smart actuator” for nanometer scale positioning both in and out of plane. The utilization of smart actuators/sensors will have many benefits over current positioning stages including the utilization of advantageous composite properties, the increase of the resonant frequency of the stage system, the simplification of the manufacturing procedure, and possible increased range of motion. Enhanced mechanical response is made possible by using composite materials and proper layer orientation. This work is a “proof of concept” design for the ultra-precision smart actuator. Analytical and numerical models were developed to determine the response of the composite material and piezoelectric actuator system. Experimentation was performed on the system to verify the results of the mathematical and numerical models. Good correlation between mathematical, numerical, and experimental data was seen in axial and bending modes of operation. Results from the parametric and experimental verification studies are presented to illustrate the efficacy of the design concept.
The Finite Screw System Associated With the Spatial RPRP Overconstrained Linkage
Authors: Huang Chintien , Tu Han-Tsung
Published: April 2009

The spatial RPRP linkage is a closed-loop linkage composed of two revolute and two prismatic joints. It is an overconstrained linkage, which does not obey the Gru¨bler criteria. This paper investigates the finite displacement of the RPRP linkage and shows that all possible finite displacement screws of the coupler link form a screw system of the second order. This paper explores two configurations of the RPRP linkages, folded and unfolded. The screw systems for both types of RPRP linkage are obtained by intersecting two 3-systems corresponding to the RP and PR dyads. A numerical example is provided to verify the result.
Biologically Inspired Design of Small Flapping Wing Air Vehicles Using Four Bar Mechanisms and Quasi-Steady Aerodynamics
Authors: Madangopal Rajkiran , Khan Zaeem A. , Agrawal Sunil K.
Published: April 2009

In this paper, the energetics of a flapping wing micro air vehicle is analyzed with the objective of design of flapping wing air vehicles. The salient features of this study are: (i) design of an energy storage mechanism in the air vehicle similar to an insect thorax which stores part of the kinetic energy of the wing as elastic potential energy in the thorax during a flapping cycle; (ii) inclusion of aerodynamic wing models using blade element theory and inertia of the mechanism using rigid body modeling techniques; (iii) optimization of parameters of the energy storage mechanism using the dynamic models so that energy input from the external actuators during a flapping cycle is minimized. A series of engineering prototypes based on these studies have been fabricated which justify the use of these mathematical techniques.
Real-Time Direct Position Analysis of Parallel Spherical Wrists by Using Extra Sensor Data
Authors: Vertechy R. , Parenti-Castelli V.
Published: April 2009

The paper presents an algorithm for the real-time evaluation of the actual end-effector orientation (pose) of general parallel spherical wrists. Conceptually, the method relies on the evidence that the pose of a rigid body is defined once the location of at least two linearly independent vectors attached to the body is known. The location of these vectors of the wrist end-effector is determined by the solution of the direct position analysis of some properly chosen kinematic chains (legs) of the manipulator. In order to accomplish this analysis, extra-sensors, which measure suitable non-actuated variables of the chosen legs, need to be placed in addition to the ones normally embedded in the servo motors, i.e. the sensors which measure the actuated variables. From a mathematical point of view, the algorithm is built on the Polar Decomposition of a matrix and has inherent least square features. Thus, together with measurement redundancy, i.e. more sensors (extra-sensors) than the mechanism degrees of freedom, the method also allows minimizing the influence of both round-off and measurement errors on the estimation of the location of the wrist end-effector. The method is general but, in order to prove its effectiveness, without loss of generality it has been customized to the solution of the (3-UPS)S fully parallel wrist architecture. Comparison of the proposed method, in both its general and specialized form, with others from the literature is provided.
Identifying Gait Patterns for Dynamically Stable Walking
Authors: Agrawal Abhishek , Agrawal Sunil K.
Published: April 2009

We anticipate that the motion of biped machines should be similar to human motion to achieve dynamic stability. In this paper, a novel approach to compute dynamically stable gait of a planar six degree-of-freedom biped is presented. This approach is analytical and is based on periodic property of a gait cycle. The resulting gait satisfies all dynamic stability criteria.
Modeling Spatial Rigid Multibody Systems Using an Explicit-Time Integration Finite Element Solver and a Penalty Formulation
Authors: Wasfy Tamer
Published: April 2009

A new technique for modeling rigid bodies undergoing spatial motion using an explicit time-integration finite element code is presented. The key elements of the technique are: (a) use of the total rotation matrix relative to the inertial frame to measure the rotation of the rigid bodies; (b) time-integration of the rotational equations of motion in a body fixed (material) frame, with the resulting incremental rotations added to the total rotation matrix; (c) penalty formulation for creating connection points (virtual nodes which do not add extra degrees of freedom) on the rigid-body where joints can be placed. The use of the rotation matrix along with incremental rotation updates circumvents the problem of singularities associated with other types of three and four parameter rotation measures. Benchmark rigid multibody dynamics problems are solved to demonstrate the accuracy of the present technique.
Selecting Joint Locations in a Watt II Six-Bar With Sliding Output to Ensure a Cranking Input
Authors: Perry Lauren S. , Murray Andrew P.
Published: April 2009

One method for generating a Watt II six-bar with a sliding output is to identify the location of its six revolute (R) joints. The location of the output prismatic (P) joint does not need to be identified as it can be assumed to allow vertical motion through the final R joint. If classified, like the 4R, based on the range of motion of each link as cranking or rocking, a number of possibilities exist classifying the four moving links connecting the six R joints. In this paper, we introduce a methodology for ensuring that the link connecting the first two R joints is a crank. As there are four more locations to specify, each location needs to be selected in light of the locations of the previous R joints. To accomplish this goal, we identify the Watt II six-bar transition linkages on the boundary between classifications.
Numerical Optimization of the Design of a Laparoscopic Grasper, Statically Balanced With Normal Springs
Authors: Drenth Jacco , Herder Just L.
Published: April 2009

Static balancing can be used as a means to compensate certain (disturbance) forces in a mechanism. This paper describes a two-step design strategy for statically balanced mechanisms, balanced with normal extension springs. During the first step, ideal springs (with zero free length) are used to develop a perfectly balanced design. This can be done with the aid of a design framework, which is based on a set of elementary rules for the modification of a standard configuration of idealized springs under constant system potential energy. In the second step, the ideal springs are replaced with normal springs and the resulting unbalanced system is numerically optimized, using a genetic algorithm. The emphasis of this paper will be on the second step. A laparoscopic grasper is used as a design example and is optimized for the specified range of motion. It is optimized with respect to a constant total potential energy function and a constant force transfer function between the operating force and the resulting force that is applied by the grasper.
A New Measurement Device for Kinematic Calibration of Parallel Manipulators
Authors: Rauf Abdul , Kim Sung-Gaun , Ryu Jeha
Published: April 2009

Kinematic calibration is a process that estimates the actual values of geometric parameters to minimize the error in absolute positioning. Measuring all the components of Cartesian posture assure identification of all parameters. However, measuring all components, particularly the orientation, can be difficult and expensive. On the other hand, with partial pose measurements, experimental procedure is simpler. However, all parameters may not be identifiable. This paper proposes a new device that can be used to identify all kinematic parameters with partial pose measurements. Study is performed for a 6 DOF (degree-of-freedom) fully parallel Hexa Slide manipulator. The device, however, is general and can be used for other parallel manipulators. The proposed device consists of a link with U joints on both sides and is equipped with a rotary sensor and a biaxial inclinometer. When attached between the base and the mobile platform, the device restricts the end-effector’s motion to 5 DOF and measures two position components and one rotation component of the end-effector. Numerical analyses of the identification Jacobian reveal that all parameters are identifiable. Computer simulations show that the identification is robust for the errors in the initial guess and the measurement noise. Intrinsic inaccuracies of the device can significantly deteriorate the calibration results. A measurement procedure is proposed and cost functions are discussed to prevent propagation of the inaccuracies to the calibration results.
Sensitivity Analysis of the Orthoglide, a 3-DOF Translational Parallel Kinematic Machine
Authors: Caro Ste´phane , Wenger Philippe , Bennis Fouad , Chablat Damien
Published: April 2009

This paper presents a sensitivity analysis of the Orthoglide, a 3-DOF translational Parallel Kinematic Machine. Two complementary methods are used to analyze its sensitivity to its dimensional and angular variations. First, a linkage kinematic analysis method is used to have a rough idea of the influence of the dimensional variations on the location of the end-effector, and shows that the variations in design parameters of the same type from one leg to another one have the same influence on the end-effector. However, this method does not allow the designer to know the influence of the variations in the parallelograms. Thus, a differential vector method is used to study the influence of the dimensional and angular variations in the parts of the manipulator, and particularly the variations in the parallelograms, on the position and orientation of the end-effector. It turns out that the isotropic kinematic configuration of the manipulator is the least sensitive one to its geometrical variations, contrary to the closest configurations to its kinematic singular configurations, which are the most sensitive to geometrical variations.
Locomotion Through the Intestine by Means of Rolling Stents
Authors: Breedveld Paul , van der Kouwe Danie¨lle E. , van Gorp Maria A. J.
Published: April 2009

Colonoscopy is a standard medical procedure in which a long and flexible endoscope is inserted into the rectum for inspection of the large intestine and for simple interventions. Pushing the endoscope tip from behind via a long and flexible tube leads easily to buckling when the tip comes in contact with sharp curves in the intestinal wall. Buckling is accompanied by painful cramps and makes it difficult to complete the procedure. A way to avoid buckling is not to push the tip from behind, but to use the friction with the intestinal wall to pull the tip forward. This paper describes the state-of-the-art in research on intestinal locomotion methods and presents a new locomotion method based on a rolling donut that is positioned around the endoscope tip. The donut functions like a circular caterpillar and is constructed from three stents that generate high friction with the intestinal wall. The diameter of the donut can be changed and the stents can be driven independently to reduce slip in intestinal curves. The resulting Rolling-Stent Endoscope contains a new steerable mechanism by which the tip can be bent in all directions over a very large angle. The Rolling-Stent Endoscope was applied for a patent and a prototype is under development for evaluation in the intestine of a pig.
Torsional Stiffnesses of the Soft Contact of a Soft-Robotic-Finger
Authors: Ghafoor Abdul , Dai Jian S.
Published: April 2009

This paper investigates the equivalent contour representation of the soft contact, proposes torsional stiffness coefficients relating the contact contour to a soft-robotic-finger contact and develops the finite elastic elements of the soft finger. The contact is modeled between a grasped object and a soft fingertip as a number of contours with a set of equivalent elastic contact points arranged on each contour. The stiffness matrix model is presented and related to the torsional stiffness coefficients. The paper further reveals the effect of the robotic finger stiffness on the stiffness coefficients by modeling the finger with a finite number of elastic elements arranged serially. The couples which arise from the elastic elements give translational and torsional stiffness characteristics of the soft contact. This presents a way of measuring soft contact stiffness. In particular, the torsional stiffness is investigated with its variance with the contours. A case study is presented at the end.
Position Analysis of the RRP-3(SS) Multi-Loop Spatial Structure
Authors: Innocenti Carlo , Wenger Philippe
Published: April 2009

The paper presents the position analysis of a spatial structure composed of two platforms mutually connected by one RRP and three SS serial kinematic chains, where R, P, and S stand for revolute, prismatic, and spherical kinematic pair respectively. A set of three compatibility equations is laid down that, following algebraic elimination, results in a 28th-order univariate algebraic equation, which in turn provides the addressed problem with 28 solutions in the complex domain. Among the applications of the results presented in this paper is the solution to the forward kinematics of the Tricept, a well-known in-parallel-actuated spatial manipulator. Numerical examples show adoption of the proposed method in dealing with two case studies.
A Fairly Simple Method to Identify the Curvature of a Cam Profile
Authors: Ceccarelli Marco , Carbone Giuseppe , Lanni Chiara , Ottaviano Erika
Published: April 2009

In this paper, the problem of identification of cam profiles is addressed by proposing a suitable kinematic model. A suitable test-bed has been designed and built at LARM: Laboratory of Robotics and Mechatronics in Cassino for experimental tests. The study proposed in this paper has been carried out specifically for circular-arc cams and validation tests have given satisfactory results for identification of the profile curvature.
Design of an Ultra Precision Diaphragm Flexure Stage for Out-of-Plane Motion Guidance
Authors: Chen Shih-Chi , Golda Dariusz , Herrmann Ariel , Slocum Alexander H.
Published: April 2009

An ultra-precision diaphragm flexure stage was designed and optimized for pure out-of-plane Z-motion guidance with an effort to minimize parasitic lateral and tilt motions. The diaphragm flexure stage will be used to guide an objective lens along the optical axis in a high performance microscope. A concept with cross-linked radial spoke geometry akin to a bicycle wheel was designed to maximize its in-plane to out-of-plane stiffness ratio. The geometry was then optimized using finite element analysis. Several prototypes were manufactured using an abrasive water jet machining center and tested with a reconfigurable test fixture. Sets of two and four diaphragms were tested. Negligible improvement in parasitic motion was observed between the two and four-diaphragm configurations. The experimental results for out-of-plane stiffness matched the finite element result within 0.3%. Negligible hysteresis in vertical motion was observed. Maximum lateral parasitic motion on the order 2 μm was measured over a Z-motion range of 140 μm. The lateral displacement was linear (R2=0.998) and repeatable, and could be an artifact of misalignment of the diaphragms in the test fixture.
Design and Optimization of a Mechanism for Out of Plane Insect Wing Like Motion With Twist
Authors: Banala Sai K. , Karakaya Yeliz , McIntosh Sean , Khan Zaeem , Agrawal Sunil K.
Published: April 2009

A mechanism is presented that can generate insect wing like motion. This motion includes both flapping out of the stroke plane in addition to twist of the wing. The mechanism has a single degree-of-freedom and employs a five bar mechanism in addition to an auxiliary four bar mechanism. The parameters in the mechanism were optimized to generate a prescribed motion of the wing taken from a hawk moth kinematic flight data. A scaled model of the mechanism was fabricated to verify practical feasibility of the design. In future we will miniaturize this mechanism on our flying bird prototypes.
Development of a Test Bed System for Robot Actuators
Authors: Yoo Jae Gu , Hvass Paul , Tesar Delbert
Published: April 2009

This paper describes the design and utilization of an advanced dynamic dynamometer test bed for electromechanical robot actuators. Typically actuators are tested at steady state under continuous load, but this is insufficient to characterize the nonlinear properties of actuators. The test bed was specifically designed with the capability to emulate high bandwidth complex duty cycle loads. Furthermore, the test bed is modular which enables rapid reconfiguration of test components. The test bed is comprised of a servo motor which serves as a dynamic load emulator, a brake, a clutch, full sensor array for comprehensive monitoring of test variables, and supporting motion control hardware. Two preliminary tests of a permanent magnet synchronous motor (PMSM) were conducted to demonstrate some of the test bed’s capabilities. These included a torque ripple test and a test to determine torque variation for a sinusoidal load at constant speed. The results show increased torque ripple for increasing speed. The sinusoidal loading test demonstrates the nonlinearities associated with actuator dynamics. Future testing will focus on the full characterization of an actuator.
High Speed Automotive Cam Design Using Direct Multiple-Shooting Optimal Control Techniques
Authors: Mennicke Sebastian , Longman Richard W. , Chew Meng-Sang , Bock Hans Georg
Published: April 2009

Prior investigations have presented the use of optimal control theory in the design of high-speed cam follower systems. These investigations were constrained by the difficulty of numerical solutions of optimal control problems, and this limited the types of criteria investigated, the state inequality constraints considered, and the realism of the models used. In recent years numerical solution techniques based on direct multiple shooting and using specially structured sequential quadratic programming have become available. These are capable of handling complex optimization criteria and imposing state and control in-equality constraints. This paper investigates and illustrates the potential of such methods in revolutionizing high speed automotive cam design. Cam design is complicated by the number of partially competing criteria one is interested in. This work synthesizes an optimal cam design approach, considering a range of speeds, the area under the lift curve, Hertzian contact stress, vibrations and residual vibrations, energy loss, cam curvature, follower force, and contact stress. The paper illustrates how all of these criteria can be integrated into the optimization in the design stage. Since the polydyne method is not an optimization procedure, the resulting design is superior to polydyne design in all aspects considered.
Preliminary Design Concepts for Compliant Mechanism Prosthetic Knee Joints
Authors: Gue´rinot Alexandre E. , Magleby Spencer P. , Howell Larry L.
Published: April 2009

Compliant mechanisms present several design advantages that may be exploited in prosthetic joint design — low friction and wear, low part count, light weight, high reliability, efficient manufacturing and assembly, etc. However, they also come with their share of challenges. For example, in the past compliant mechanisms have not been viable alternatives to rigid-body joints in high compression applications. Two principles, isolation and inversion, can be successfully applied to many compliant joints to increase their ability to withstand high compressive loads and make them viable design alternatives to some current prosthetic joint designs. This paper presents preliminary design concepts for a compliant prosthetic knee. The inverted cross-axis flexural pivot design is selected and a proof of concept prototype is constructed and tested. The prototype exceeds the functional specification of 550 lbs, and satisfies a maximum deflection of 140°, an infinite life for a deflection of 110°, and a weight under 2 lbs.
A Tabu-Gradient Search-Based Optimization Technique for Synthesis of Mechanisms
Authors: Smaili Ahmad , Atallah Naji
Published: April 2009

Mechanism synthesis requires the use of optimization methods to obtain approximate solution whenever the desired number of positions the mechanism is required to traverse exceeds a few (five in a 4R linkage). Deterministic gradient-based methods are usually impractical when used alone because they move in the direction of local minima. Random search methods on the other hand have a better chance of converging to a global minimum. This paper presents a tabu-gradient search based method for optimum synthesis of planar mechanisms. Using recency-based short-term memory strategy, tabu-search is initially used to find a solution near global minimum, followed by a gradient search to move the solution ever closer to the global minimum. A brief review of tabu search method is presented. Then, tabu-gradient search algorithm is applied to synthesize a four-bar mechanism for a 10-point path generation with prescribed timing task. As expected, Tabu-gradient base search resulted in a better solution with less number of iterations and shorter run-time.
The Synthesis of Robust Spherical Motion Generators
Authors: Al-Widyan Khalid , Angeles Jorge
Published: April 2009

The synthesis of spherical motion generators in the presence of an incomplete set of finitely-separated attitudes is discussed in this paper. Given that five attitudes of the coupler link define a discrete set of dyads, any number of attitudes smaller than five is considered incomplete in this paper. The attitudes completing the set are determined so as to produce a robust linkage against variations in these attitudes. To this end, a theoretical framework as well as a general methodology for robust synthesis are laid down. Robustness is needed in this context to overcome the presence of uncertainty due to the selection of the intermediate attitudes, which many a time are left up to the mechanism designer’s judgment. To validate the concepts and illustrate the application of the methodology proposed here, we include a numerical example.
The Design of a Chain of Spherical Stephenson Mechanisms for a Gearless Pitch-Roll Wrist
Authors: Herna´ndez S. , Bai S. P. , Angeles J.
Published: April 2009

Although bevel-gear wrists are widely used in industrial manipulators due to their simple kinematics and low manufacturing cost, their gear trains function under rolling and sliding, the latter bringing about noise and vibration. Sliding is inherent to the straight teeth of the bevel gears of these trains. Moreover, un-avoidable backlash introduces unmodeled dynamics, which mars robot performance. To alleviate these drawbacks, a gearless pitch-roll wrist is currently under design for low backlash and high stiffness. The wrist consists of spherical cam-rollers and spherical Stephenson linkages; two roller-carrying disks drive a combination of cams and Stephenson mechanisms rotating as a differential mechanism. In this paper, the design of the chain of spherical Stephenson mechanisms (SSMs) is introduced. The problem of the dimensional synthesis is addressed and interference avoidance is discussed. An embodiment of the concept is also included.
Application of Compliant Mechanisms to Active Vibration Isolation Systems
Authors: Tantanawat Tanakorn , Li Zhe , Kota Sridhar
Published: April 2009

Compliant mechanisms have been designed for various types of applications to transmit desired forces and motions. In this paper, we explore an application of compliant mechanisms for active vibration isolation systems. For this type of application, an actuator and a compliant mechanism are used to cancel undesired disturbance, resulting in attenuated output amplitude. An actuator provides external energy to the system while a compliant mechanism functions as a transmission controlling the amount of displacement transmitted from the actuator to the payload to be isolated. This paper illustrates, based on preliminary results of finite element analyses (FEA), that a compliant mechanism equipped with an actuator can be used as an active vibration isolator to effectively cancel a known sinusoidal displacement disturbance at low frequencies by using a feedforward disturbance compensation control. The nonlinear FEA shows that a sinusoidal displacement disturbance of 6.0 mm amplitude is reduced by 95% at 3.9 Hz and 91% at 35.1 Hz with a sinusoidal displacement controlled input of 0.73 mm amplitude.
Dynamic Model of a Four-Wheel-Drive HMMWV
Authors: Sleight Randy , Agrawal Sunil K.
Published: April 2009

There is a need for HMMWV dynamic models for autonomous control of these vehicles. Currently, such four-wheel-drive vehicle models are unavailable. This paper derives the kinematics, dynamics and computation aspects of the problem. The subsystem models, e.g. tire, brake and powertrain, are presented as well. Our results show agreement with published simulations of the HMMWV. The current simulations in Mat-lab execute 30 times slower than real-time. Future work will implement this model in a planning algorithm for autonomous vehicle control.
Manipulator Task-Based Performance Optimization
Authors: Pholsiri Chalongrath , Kapoor Chetan , Tesar Delbert
Published: April 2009

This research uses new developments in redundancy resolution and real-time capability analysis to improve the ability of an articulated arm to satisfy task constraints. Task constraints are specified using numerical values of position, velocity, force, and accuracy. Inherent in the definition of task constraints is the number of output constraints that the system needs to satisfy. The relationship of this with the input space (degrees of freedom) defines the ability to optimize manipulator performance. This is done through a Task-Based Redundancy Resolution (TBRR) scheme that uses the extra resources to find a solution that avoids system constraints (joint limits, singularities, etc.) and satisfies task constraints. To avoid system constraints, we use well-understood criteria associated with the constraints. For task requirements, the robot capabilities are estimated based on kinematic and dynamic manipulability analyses. We then compare the robot capabilities with the user-specified requirement values. This eliminates a confusing chore of selecting a proper set of performance criteria for a task at hand. The breakthrough of this approach lies in the fact that it continuously evaluates the relationship between task constraints and system resources, and when possible, improves system performance. This makes it equally applicable to redundant and non-redundant systems. The scheme is implemented using an object-oriented operational software framework and its effectiveness is demonstrated in computer simulations of a 10-DOF manipulator.
Spatial Distance of Point-Lines
Authors: Zhang Yi , Ting Kwun-Lon
Published: April 2009

A point-line is the combination of a directed line with a reference point on it. In this article, the spatial distance between two point-lines in space is defined based on a point-line displacement model. The displacement of a point-line from one position to the other is uniquely described as the composition of a pure translation along the point-line and a screw displacement about the common normal of the two positions. It is shown that such a displacement model leads to a simpler configuration of the underlying screw triangle and defines the shortest distance between two point-lines. The dual quaternion algebra is used to describe the idea with mathematic expressions.
Design Optimization for a Parallel MEMS Mechanism With Flexure Joints
Authors: Kang Byoung Hun , Wen John T. , Dagalakis Nicholas G. , Gorman Jason J.
Published: April 2009

This paper presents an analysis tool and design method for MEMS parallel mechanisms. Due to processing constraints in MEMS fabrication, flexure joints are frequently used in MEMS mechanisms. Flexure joints offer advantages over other joint designs due to their monolithic characteristics. They can be used to reduce the size of manipulators or to increase the precision of motion. Their inherent flexibility, however, also results in task space compliance which needs to be carefully designed to match the task specification. This paper presents an analysis and design tool for such mechanisms by using the differential kinematics. Performance metrics are chosen based on manipulability and task stiffness matrices, which in turn are used in a multi-objective optimization. As an illustrative example, a 1-DOF MEMS parallel mechanism based on the macro- and meso-scale models designed by NIST is considered with several choices of performance metrics and design variables. The resulting designs are successfully fabricated using DRIE process.
Theoretical and Experimental Analysis of In Vivo Wheeled Mobility
Authors: Rentschler Mark , Dumpert Jason , Hadzialic Adnan , Platt Stephen R. , Farritor Shane , Oleynikov Dmitry , Iagnemma Karl
Published: April 2009

Laparoscopy is abdominal surgery performed with long tools inserted through small incisions. The use of small incisions reduces patient trauma, but also eliminates the surgeon’s ability to directly view and touch the surgical environment. These limitations generally restrict the application of laparoscopy to less complex procedures. Large robots external to the patient have been used to aid in the manipulation of the tools and improve dexterity. This paper presents a theoretical and experimental analysis of miniature in vivo robots. The objective is to develop a wireless mobile imaging robot that can be placed inside the abdominal cavity during surgery. Such robots will allow the surgeon to view the surgical environment from multi-angles. The motion of these in vivo robots will not be constrained by the insertion incisions.
Type Synthesis of 3-DOF PPR Parallel Manipulators Based on Screw Theory and the Concept of Virtual Chain
Authors: Kong Xianwen , Gosselin Cle´ment M.
Published: April 2009

PPR-PMs (parallel manipulators) are the parallel counterparts of the 3-DOF PPR serial robots, which are composed of two P (prismatic) joints and one R (revolute) joint. For a PPR-PM, the moving platform can rotate arbitrarily about an axis undergoing a planar translation. This paper deals with the type synthesis of 3-DOF PPR-PMs. At first, virtual chains are introduced to represent the motion patterns of 3-DOF motions and relevant results from screw theory are recalled. A method is then proposed for the type synthesis of 3-DOF PPR-PMs. Using the proposed approach, the type synthesis of 3-DOF PPR-PMs is performed in three steps, namely, the type synthesis of legs for PPR-PKCs (parallel kinematic chains), the type synthesis of PPR-PKCs, and the selection of actuated joints of PPR-PMs. The three steps are dealt with in detail consequently. The characteristics of the proposed approach is that the type synthesis of legs for PPR-PKCs is reduced to the type synthesis of 3-DOF overconstrained single-loop kinematic chains and thus easy to perform. In addition to all the 3-DOF PPR-PKCs and 3-DOF PPR-PMs proposed in the literature, a number of new 3-DOF PPR-PKCs and 3-DOF PPR-PMs are identified. It is also found that there are no PPR-PMs with identical types of legs.
Manipulability-Based Configuration Evaluation of Cooperative Payload Transport by Mobile Robot Collectives
Authors: Tang Chin Pei , Krovi Venkat
Published: April 2009

Interest in cooperative systems typically arises when certain tasks are either too complex to be performed by a single agent or when there are distinct benefits that accrue by cooperation of many simple agents. A quantitative examination of performance enhancement, due to the implementation of cooperation, is critical. In this paper, we focus on the development of a quantitative performance-analysis framework for a cooperative system with multiple wheeled mobile manipulators physically transporting a common payload. Each mobile manipulator module consists of a differentially-driven wheeled mobile robot with a mounted planar three-degree-of-freedom (d.o.f.) manipulator. A composite cooperative system is formed when a payload is placed at the end-effectors of multiple such modules. Such a system possesses the ability to change its relative configuration as well as accommodate relative positioning errors of the mobile bases. However, the combination of nonholonomic constraints due to the mobile bases, holonomic constraints due to the closed kinematic loops formed and the varying actuation of the joints within the cooperative system requires careful treatment for realizing the payload transport task. In this paper, we will analyze the cooperative composite system within a constrained mechanical system framework, by extending methods developed for treatment of articulated-closed-chain systems. Specifically, we will focus on the velocity-level kinematic modeling, while taking into account the nonholonomic/holonomic constraints and different joint-actuation schemes within the system. We then examine the applicability of a manipulability measure (isotropy index), to quantitatively analyze the system-level performance of the cooperative system, with these different joint-actuation schemes, with representative case-studies.
Construction of the Design Space of Single-Loop Change-Point Mechanisms
Authors: Lusk Craig P. , Howell Larry L.
Published: April 2009

Change-point mechanisms are shown to be significant in the design of surface micromachined MEMS. The design space of change-point mechanisms is derived for an arbitrary single loop change-point mechanism using a global and local approach. A function on the design space, the mechanism’s length, is constructed for fourbars. An inversion operator, a mapping from the design space to the design space, is also constructed for fourbars. The method for constructing the function and the operator is shown to be capable of extension to single loop change-point mechanisms with five or more links. The results give insight into design possibilities and limitations of change-point mechanisms.
Material and Local Time Derivatives of Screws With Applications to Dynamics and Stiffness
Authors: Lipkin Harvey
Published: April 2009

Screw quantities provide geometric insight into three-dimensional mechanics modeled by rigid bodies and lumped parameters. Four distinct cases of time differentiation are examined by combining fixed and moving body derivatives (fundamental to rigid body mechanics) with material and local derivatives (fundamental to continuum mechanics). Three combinations always yield another screw quantity while the most common, the material derivative with respect to the fixed body, does not. Two fundamental formulations are examined with this last derivative, Euler’s Laws and the gravitational loading of an elastic system. By coincidence, the formulations appear screw-like when they are expressed at the center-of-mass but, in contrast to actual screw formulations, they do not retain invariant forms when expressed at arbitrary points.
Automated Modeling of Nonlinear Mechanisms for Virtual Prototyping
Authors: Colton Mark B. , Hollerbach John M.
Published: April 2009

This paper addresses the problem of obtaining models of nonlinear mechanisms for use in virtual prototyping systems. The objective of the described modeling procedure is to more accurately represent the feel of complex mechanisms in force feedback applications. The model structure selected for this study is a 2nd-order impedance model, with mass, damping, stiffness, and coulomb friction that vary with position. An automated testbed system is described, as well as a segmented least-squares algorithm for estimating position-varying model parameters. Baseline results are obtained for a system comprised of a mass, dashpot, and nonlinear (hardening) spring.
Inverse Static Analysis for a Planar Compliant Platform Mechanism
Authors: Su Hai-Jun , McCarthy J. Michael
Published: April 2009

This paper studies the inverse static analysis of a planar parallel mechanism with compliant limbs. A known force and moment is applied to the moving platform, and it is required to determine the assembly configurations, or equilibrium points. Partial derivatives of the potential energy function yields the equilibrium conditions. The geometric and static constraints lead to a system of ten polynomials with ten unknowns. We use polynomial homotopy method to find that there are as many as 70 equilibrium configurations. Two examples with equilateral geometry are provided. We also examine the system behavior during a movement between selected equilibrium positions.
Synthetica 2.0: Software for the Synthesis of Constrained Serial Chains
Authors: Perez Alba , Su Hai-Jun , McCarthy J. Michael
Published: April 2009

A spatial linkage is defined by a workpiece supported by one or more serial chains. We say that the spatial linkage can perform a given task when this task belongs to its workspace. A task can be specified as a discrete set of positions or as a set of curves or surfaces. Spatial serial chains can be synthesized to perform specified tasks, and combined to form more complicated linkages. Recently we developed Synthetica 1.0, a Java-based architecture for the computer-aided-design of spatial linkages that contains task definition and visualization, and linkage visualization, analysis and synthesis modules. In this paper, we present the new version, Synthetica 2.0. Among other additions, the new version includes task interpolation, a selection matrix, a generic synthesizer and several specialized synthesis procedures for constrained spatial linkages.
Kinematics and Workspace Analysis of Protein Based Nano-Motors
Authors: Sharma G. , Badescu M. , Dubey A. , Mavroidis C. , Sessa T. , Tomassone S. M. , Yarmush M. L.
Published: April 2009

Kinematic and workspace analyses are performed to predict the performance of a new nanoscale biomolecular motor: The Viral Protein Linear (VPL) Motor. The motor is based on a conformational change observed in a family of viral envelope proteins when subjected to a changing pH environment. The conformational change produces a motion of about 10 nm, making the VPL a basic linear actuator, which can be further interfaced with other organic/inorganic nanoscale components such as DNA actuators and carbon nanotubes. This paper presents the principle of operation of the VPL motor and the development of direct and inverse kinematic models for workspace analysis. Preliminary results obtained from the developed computational tools are presented.
An Algebraic Elimination Based Algorithm for Solving the Geometric Design Problem of Spatial 3R Manipulators
Authors: Lee Eric , Mavroidis Constantinos
Published: April 2009

In this paper, the geometric design problem of serial-link robot manipulators with three revolute (R) joints when three precision points are specified is solved using an algebraic elimination method for the first time. Three spatial positions and orientations are defined and the dimensions of the geometric parameters of the 3-R manipulator are computed so that the manipulator will be able to place its end-effector at these three pre-specified locations. In this problem, six of the design parameters are set as free choices and their values are selected arbitrarily. For the specific case studied in this paper, a twelve-degree single variable polynomial is calculated that has eight roots that are the design solutions and the other four roots are extraneous solutions.
The Kinematics of Wheeled Mobile Robots With Dual-Wheel Transmission Units
Authors: Chen Chao , Ostrovskaya Svetlana , Angeles Jorge
Published: April 2009

The Dual-Wheel Transmission (DWT) unit, an innovative driving mechanism for wheeled mobile robots (WMRs), was introduced elsewhere. In this paper we conduct the direct and inverse kinematic analysis of WMRs with such units. This analysis can be applied as well to other types of WMRs equipped with conventional wheels. Both central and offset types of wheel units are discussed. The closed form symbolic solutions provided in this paper may reduce the computational complexity, as required in the real time control of such systems. Furthermore, the underlying relations reveal the geometric and physical meanings of the constraints imposed on the robots at hand.
Synthesis of Spatial Slider-Crank Mechanism for High-Speed Applications
Authors: Farhang Kambiz , Kulusu Phanidhar
Published: April 2009

Certain kinematic design constraints can be derived based on requisite dynamic performance requirements of a mechanism. Perhaps a most suitable kinematic synthesis task related to dynamic performance is function generation involving the entire motion cycle of the mechanism. For this purpose the closed-form equation of a spatial slider-crank mechanism is used to obtain approximate equations separating the various harmonics of the crank angle. The approximate equation is in terms of harmonic functions of the crank angle containing coefficients in terms of the linkage geometry. Hence the approximate equations provide an analytical means of relating the harmonic content of the slider position/displacement to the mechanism dimension. The approximate equations are utilized to establish kinematic synthesis constraints that relate to the dynamic behavior of the mechanism. Conditions for optimum dynamic performance are obtained in explicit analytical form in terms of the spatial slider-crank mechanism dimension, and used to demonstrate kinematic synthesis for minimized higher harmonic content in the slider position; thereby reduction of the induced shaking forces.
A Compliant Mechanism Design Methodology for Coupled and Uncoupled Systems, and Governing Free Choice Selection Considerations
Authors: Midha Ashok , Annamalai Yuvaraj , Kolachalam Sharath K.
Published: April 2009

Compliant mechanisms are defined as mechanisms that gain some, or all of their mobility from the flexibility of their members. Suitable use of pseudo-rigid-body models for compliant segments, and relying on the state-of-the-art knowledge of rigid-body mechanism synthesis types, greatly simplifies the design of compliant mechanisms. Assuming a pseudo-rigid-body four-bar mechanism, with one to four torsional springs located at the revolute joints to represent mechanism compliance, a simple, heuristic approach is provided to develop various compliant mechanism types. The synthesis with compliance method is used for three, four and five precision positions, with consideration of one to four torsional springs, to systematically develop design tables for standard mechanism synthesis types. These tables appropriately reflect the mechanism compliance by specification of either energy or torque. Examples are presented to demonstrate the use of weakly or strongly coupled sets of kinematic and energy/torque equations, as well as different compliant mechanism types in obtaining solutions.
Improved Pseudo-Rigid-Body Model Parameter Values for End-Force-Loaded Compliant Beams
Authors: Pauly Joby , Midha Ashok
Published: April 2009

Pseudo-rigid-body models help expedite the compliant mechanism design process by aiding the analysis and synthesis of candidate design solutions, using loop-closure techniques for rigid-body mechanisms. Opportunities for improvement were observed in the values of pseudo-rigid-body model parameters for compliant beams with nearly axial, tensile end force loads. This paper presents improved values for the affected parameters.