bluuebunny/crossref_metadata_2025 huggingface dataset:
Form Grinding of Helical Gears: Effects of Disk Shaped Tools Plunging
Authors: Gorla Carlo , Rosa Francesco
Published: June 2008

Following the example of aerospace transmissions producers, nowadays, more and more industrial fields are interested in reducing transmission noise and vibration and in increasing operating life. This requires a precise understanding of the real transmission behavior since the first steps of the design process. The usual approach is to apply theoretical meshing loads and to compute web, rim and supporting structures deflections by one of the several available methods (i.e. Finite Element Method), in order to predict stresses and deformations. But these calculations usually neglect that deformations modify gear meshing conditions, and therefore also load conditions can be very different from the theoretical ones. In order to realize models that simulate the contact between the actual tooth surfaces, taking into account the actual gear meshing conditions, we first need to know the gear tooth flank microgeometry. Also the experimental development phase of gear pairs could take advantage from a theoretical prediction of gear tooth flank micro-geometry, in order to minimize the necessary trials to set up the grinding machine. In this paper, a method and a software to compute the actual micro-geometry of ground tooth flank surfaces of helical gears is presented. In particular the grinding process by means of disk shaped tools has been studied. The effects of the choice of various parameters (especially the angle between the gear and the tool axis) have been investigated. The effects of tool plunging during its motion along the gear face have also been considered in order to appreciate the undesired modifications of tooth transverse and normal sections, caused by the particular shape of the instantaneous contact lines between the grinding wheel and the gear tooth flank being ground. The introduction of a new component of the tool relative velocity with respect to the gear, in fact, modifies the meshing conditions between the gear and the tool. The modification of the tool axis orientation, during the grinding operation, reduces this undesired effect. As a result of these calculations, the exact theoretical surface for more realistic meshing simulation is available, and, furthermore, the run of some simulations can give some helpful hints to set up the grinding machine and to design the grinding wheel.
Requirement for Limits of Action and Wildhaber’s Limit Normal
Authors: Honda Sho
Published: June 2008

One of the most important criteria to design a gear pair which has smooth tooth surfaces around a given design point is how far the design point is from the limits of action. However, in the present theories, the definition is obscure and the calculation methods are not clear except for cylindrical gears. In this paper, when a path of contact and its contact normals are given according to the unified designing method applicable to all kinds of gears having the same equations defined in the common coordinate systems which are determined by the disposition of the gear axes and the angular velocities, the infinitesimal surface of action along the path of contact and the corresponding tooth surfaces are determined and the requirement for limit of action for all kinds of gears is obtained. To design a smooth tooth surface around the design point, it is convenient to look for the limit path of contact with its contact normal whose limit of action coincides with the design point, from which a design path of contact must be inclined adequately. Finally, it is shown that Wildhaber’s limit normal is the contact normal of the limit path of contact solved under the condition that the given path of contact is an arc around the gear axis and is just one solution of the limits of action of a hypoid gear pair.
Conical Involute Gear: Development, Applications, and View for Tomorrow
Authors: Mitome Ken-ichi , Ohmachi Tatsuya , Komatsubara Hidenori
Published: June 2008

The design and production system of the conical involute gear has been developed. This system is composed of gear cutting method, gear grinding method, over-ball measurement for control of finishing dimensions, tooth surface measurement, tooth surface analysis, tooth action and normal allowable load between two mating gears, and the design of a pair of gears. As a result, conical involute gears came to be used in a wide range of applications. This paper presents the research and development for more than 25 years, many applications, and a new possibility for tomorrow.
Friction and Wear Characteristics of Natural Iron Sand Coating
Authors: Kondo Yasuo , Koide Takao , Miyachika Kouitsu , Obata Fumio
Published: June 2008

Friction and wear characteristics of natural iron sand coating were experimentally examined in the absence of lubricant. The friction motion was not be continuous, but be intermittent and proceeded by a process of stick-slip. An oxide film, Fe2O3, was formed along the sliding marks, but the amount of coating worn away was slight. There is a striking similarity in the friction coefficient between the zinc/iron sand coating and MoS2 over a load range of 20N to 1000N. The iron sand coating has a spongy structure and the bonding strength between the iron sand particles is so small that the metallic junction formed between sliding surfaces may be weaker than the substrate. Consequently the amount of metal removed may be small. In addition, the oxide film formed on coating is so soft and fluid that it may in itself function as lubricants and may play little part in abrading the other surface.
Development of a Novel Gear Measuring Device of High Accuracy
Authors: Ha¨rtig Frank , Keck Christian , Kniel Karin , Schwenke Heinrich , Wendt Klaus , Wa¨ldele Franz
Published: June 2008

The German national metrology institute, the Physikalisch-Technische Bundesanstalt (PTB), has developed a novel calibration method for gear artefacts. This reduces the current calibration uncertainty of gear standards, which is an essential step towards meeting the rising quality demands of the gear manufacturing industry. The measurement setup is based on a coordinate measuring machine (CMM) equipped with a high-precision rotary table. The key element of the novel gear measuring device is a tracking interferometer (TI) for reading the distance information. This information is combined with the reading of the coordinate measuring machine line scales in order to reduce the overall measurement uncertainty. If an optimized measurement strategy is applied, the measurement results are almost achieved with laser interferometer accuracy. First simulations and measurement results for an involute profile artefact are presented and discussed.
Optimal Tooth Modifications in Hypoid Gears
Authors: Simon Vilmos V.
Published: June 2008

A method for the determination of optimal tooth modifications in hypoid gears based on improved load distribution and reduced transmission errors is presented. The modifications are introduced into the pinion tooth surface by using a cutter with bicircular profile and by changing the cutter diameter. In the optimization of tool parameters the influence of shaft misalignments of the mating members is included. As the result of these modifications a point contact of the meshed teeth surfaces appears instead of line contact; the hypoid gear pair becomes mismatched. By using the method presented in [1] the influence of tooth modifications introduced on tooth contact and transmission errors is investigated. Based on the results that was obtained the radii and position of circular tool profile arcs and the cutter diameter for pinion teeth generation were optimized. By applying the optimal tool parameters, the maximum tooth contact pressure is reduced by 16.22% and the angular position error of the driven gear by 178.72%, in regard to the hypoid gear pair with a pinion manufactured by a cutter of straight-sided profile and of diameter determined by the commonly used methods.
Coatings for Automotive Planetary Gearsets
Authors: Anderson N. E. , Lev L. C.
Published: June 2008

The operating environment in typical automotive planetary gearsets leads to harsh tribological conditions. Relatively low operating speeds combined with low viscosity lubricants hinder the formation of protective oil films. As power density increases, gear surface fatigue (pitting) limits gear life and the life of the transmission as a whole. Coatings have been found to be effective in extending pitting fatigue life of gears. The authors have tested a number of different coatings over the last ten years. Some of them increased gear life by fifteen times in bench tests. The most successful coatings have been hard, ceramic coatings such as B4C and Diamond-Like Carbon (DLC) that smooth the mating surface and improve the lubrication conditions in the contact. Recently CrN, a widely available and affordable coating, has been studied and found to be a good alternative to other coatings.
Increased Surface Fatigue Lives of Spur Gears by Application of a Coating
Authors: Krantz Timothy L. , Cooper Clark V. , Townsend Dennis P. , Hansen Bruce D.
Published: June 2008

Hard coatings have potential for increasing gear surface fatigue lives. Experiments were conducted using gears both with and without a metal-containing, carbon-based coating. The gears were case-carburized AISI 9310 steel spur gears. Some gears were provided with the coating by magnetron sputtering. Lives were evaluated by accelerated life tests. For uncoated gears, all of fifteen tests resulted in fatigue failure before completing 275 million revolutions. For coated gears, eleven of the fourteen tests were suspended with no fatigue failure after 275 million revolutions. The improved life owing to the coating, approximately a six-fold increase, was a statistically significant result.
Preliminary Comparison of Experimental and Analytical Efficiency Results of High-Speed Helical Gear Trains
Authors: Handschuh Robert F. , Kilmain Charles J.
Published: June 2008

An experimental and analytical comparison of the efficiency of high-speed helical gear trains is presented. Analyses of the gearing losses were conducted. Test data from a helical gear train at varying speeds and loads (to 3730 kW (5,000 hp) and 15,000 rpm) was collected. A comparison of the results indicated that the operational conditions of the gearing system effects the loss contributions of the various mechanisms and therefore the overall efficiency of the gear system.
Determining Power Losses in Helical Gear Mesh: Case Study
Authors: Heingartner Petra , Mba David
Published: June 2008

Currently legislation is in place to encourage a reduction in energy usage. As such there is an increased demand for machinery with higher efficiencies, not only to reduce the operational costs of the machinery, but also to cut capital expenditure. The power losses associated with the gear mesh can be divided into speed and load dependant losses. This paper reviews some of the mathematical models proposed for the individual components associated with these losses, such as windage, churning, sliding and rolling friction loses. A mathematical model is proposed which predicts the power losses on helical gears highlighting the major contributor to losses in the gear mesh. Furthermore, the mathematical model is validated with a case study.
Gear Surface Temperature Monitoring
Authors: Jia Yi , Quinones Pablo D.
Published: June 2008

Frictional heating from rolling and sliding contacts of gear teeth is of extreme importance for monitoring the health of a gear transmission under its continuing operation. The surface temperature holds the critical information about a gear’s health condition. A new power circulating gear test rig with a multichannel computer data acquisition system has been built to develop various sensor technologies for surface temperature evaluation of gear teeth. In this paper, the surface temperature monitoring of gear tooth will be presented by using miniature thermocouples. Five miniature type-K thermocouples of 125 μm in diameter have been embedded underneath the tooth surface of a spur gear, and real-time surface temperature variations from a wide range of operating conditions were measured. The various effects of load, rotating speed, and meshing point on the surface temperature are discussed. The results attained in this study indicate that the maximum temperature rise occurs on the dedendum, close to the dedendum circle, and the maximum surface temperature difference at the various contact points along the tooth profile was 13°C. Among the various temperature monitoring techniques, the thermocouple is a very reliable and practical mean for gear health monitoring.
A Novel Three-DOF 3-RRRRR Parallel Platform Mechanism and Its Position Analysis
Authors: Li Shihua , Huang Zhen , Wu Jianguang
Published: June 2008

In order to enrich deficient-DOF parallel mechanism models, a novel model of a 3-DOF platform manipulator is presented and establish its inverse kinematics equation. Here, studies instantaneous motions of 3-RRRRR parallel manipulator at initial configuration and general configuration. Find: it has three degrees of freedom at initial configuration and after translated along the X, Y, Z axis. Secondly, the relation is given between every active input (θ1) and moving platform position by using D-H means, the solution is developed for inverse kinematics, numerical example for the position kinematic is presented, the figure of workspace along the Z-axis is drawn finally. The mechanism can be applied to jiggle mechanism.
Position and Workspace Analyses of 3-SPR and 3-RPS Parallel Manipulators
Authors: Lu Yi , Zhao Yonghe
Published: June 2008

An analytic approach and a simulation mechanism for solving position and the workspace of a 3-SPR parallel manipulator are proposed. First, a simulation mechanism of the 3-SPR parallel manipulator and a simulation mechanism of the 3-RPS parallel manipulator are created by using the computer aided geometry constraints and dimension-driving techniques. Second, some analytic formulas are derived for inverse and forward solving position and orientation of the 3-SPR parallel manipulator. Third, some available solutions from multi-solutions during deriving analytic formula are determined, and analytic inverse and forward solutions are verified by using simulation mechanisms. Finally, the workspace of the 3-SPR parallel manipulator is created and three key parameters for determining work space of two kinds of parallel manipulators are solved. Calculation results prove that the position working space of the 3-SPR parallel manipulator is much larger than that of the 3-RPS parallel manipulator, and the orientation workspace of the 3-SPR parallel manipulator is less than that of 3-RPS parallel manipulator.
Dynamics and Motion Control of Flexible Manipulators With Multi-Degree of Kinematic Redundancy
Authors: Yu Yue-Qing , Yang Ji-Yun
Published: June 2008

The dynamics and motion control of flexible robot manipulators is an advanced topic in the study of robotics. The precise tracking of the end-effector trajectory of flexible robots can be improved by the self-motion of redundant manipulators. The flexible manipulator with single-degree of kinematic redundancy has been considered only at present. This study addresses on the dynamics and motion control of flexible robots with multi-degree of kinematic redundancy. Compared with the robot with one-degree of redundancy, the optimal motion programming of a flexible robot manipulator with two-degree of redundancy has been obtained successfully based on pseudo-inverse solution. The numerical results of planar three-link and four-link flexible manipulators show the advantage of multi-degree of redundancy in improving the kinematic and dynamic performances of flexible robot manipulators.
Workspace Analysis and Visualization of Mechanical Manipulators With Non-Unilateral Constraints
Authors: Yang Jingzhou , Abdel-Malek Karim
Published: June 2008

An analytical method is presented to obtain all surfaces enveloping the workspace of a general n degree-of-freedom mechanism with non-unilateral constraints. The method is applicable to kinematic chains that can be modeled using the Denavit-Hartenberg representation method for serial manipulators. The method introduced in this paper is based upon analytical criteria for determining singular behavior of the mechanism. A perturbation approach is implemented to determine the interior and exterior of the workspace. The complete mathematical formulation is presented and illustrated using 3 and 4 DOF spatial manipulators. The paper present a rigorous analysis of the sub-Jacobians to determine a classification of singularities: Type I sets are position Jacobian singularities; Type II sets are instantaneous singularities that are due to a generalized joint that is reaching its apex; Type III sets are domain boundary singularities, which are associated with the initial and final values of the time interval; Type IV sets are coupled singularities, which are associated with a relative singular Jacobian, where the null space is reduced in one submatrix due to either of two occurrences: a Type II or Type III singularities. The paper presents a general formulation for determining the workspace.
Optimization of Biped Gait Synthesis Using Fuzzy Neural Network Controller
Authors: Pajaziti Arbnor , Gojani Ismajl , Shala Ahmet , Kopacek Peter
Published: June 2008

The Biped Robots have specific dynamical constraints and stability problems, which reduce significantly their motion range. In these conditions, path planning and tracking becomes very important. The joint profiles have been determined based on constraint equations cast in terms of step length and high, step period, maximum step height etc. In this paper Fuzzy Neural Network Controller for Path-Planning and Tracking on incline terrain (up stairs) of a planar five-link Biped Robot is presented. The locomotion control structure is based on integration of kinematics and dynamics model of Biped Robot. The proposed Control Scheme and Fuzzy Neural Algorithm could be useful for building an autonomous non-destructive testing system based on Biped Robot. Structure of Fuzzy Neural Network Controller is optimized using Genetic Algorithm. The effectiveness of the method is demonstrated by simulation example using Matlab software.
Research and Design of a Pre-Stressed Six-Component Force/Torque Sensor Based on the Stewart Platform
Authors: Zhao Yong-Sheng , Hou Yu-Lei , Yan Zhi-Wei , Yuan Hui-Ling , Gao Jin
Published: June 2008

This paper presents the research and design of a novel parallel architecture of pre-stressed six-component force/torque sensor based on the Stewart platform. The mathematical model of the structure was build by using the screw theory. The influence of joint frictional moment on the performances of the sensor is analyzed by using the concept of kinematic influence coefficient. In this paper, we define the indices of force/torque isotropy and generalized amplifying index to evaluate the performances of the sensor and discuss the optimal design of the sensor dimensions considering these indices. The prototype sensor was designed and manufactured. The theoretical and experimental study of the static calibration of the prototype is carried out, and the problem of the hyperstatic is solved perfectly. The results from the static calibration experimentation validate the correctness of the theoretical analysis.
The Novel Characteristic Representations of Kinematic Chains and Their Applications
Authors: Huang Z. , Ding H. F. , Cao Y.
Published: June 2008

In this paper, based on perimeter topological graphs of kinematic chains, many novel topological concepts including the synthetic degree-sequence, the characteristic adjacency matrix and the characteristic representation code of kinematic chain are proposed. Both the characteristic adjacency matrix and the characteristic representation code are unique for any kinematic chain and easy to be set up. Therefore a quite effective isomorphism identification method is presented depending on the characteristic adjacency matrix. It high effectiveness is proved by many examples. With object-oriented programming language, a program which can sketch topological graphs of kinematic chains has been developed based on the characteristic representation code. Finally, an application software system establishing the atlas database of topological graphs is introduced. And some functions about the atlas database are also presented in this paper.
A New Appraoch to Shape Optimization for Closed Path Synthesis of Planar Mechanisms
Authors: Smaili Ahmad , Diab Nadim
Published: June 2008

A method for the synthesis of four-bar mechanisms to generate closed paths through shape optimization is herein introduced. The objective function is not based on Fourier descriptors, rather on the cyclic angular deviation (CAD) vector associated with a set of desired points on the curve. A simple method is introduced to account for the starting point shift between the desired CAD and the generated one. Following shape optimization, a simple mathematical approach is devised to properly scale, rotate, and translate the mechanism to the desired configuration. A case study is presented to demonstrate the effectiveness and robustness of the proposed method.
An Adaptive Evolutionary Switching Control for Robot Manipulators
Authors: Ouyang P. R. , Zhang W. J. , Gupta Madan M.
Published: June 2008

In this paper, a new adaptive switching control approach, called adaptive evolutionary switching PD control (AES-PD), is proposed for iterative operations of robot manipulators. The proposed AES-PD control method is a combination of the feedback of PD control with gain switching and feedforward using the input torque profile obtained from the previous iteration. The asymptotic convergence of the AES-PD control method is theoretically proved using Lyapunov’s method. The philosophy of the switching control strategy is interpreted in the context of the iteration domain to increase the speed of the convergence for trajectory tracking of robot manipulators. The AES-PD control has a simple control structure that makes it easily implemented. The validity of the proposed control scheme is demonstrated for the trajectory tracking of robot manipulators through simulation studies. Simulation results show that the AES-PD control can improve the tracking performance with an increase of the iteration number. The EAS-PD control method has the adaptive and learning ability; therefore, it should be very attractive to applications of industrial robot control.
A New Approach for Exact/Approximate Point Synthesis of Planar Mechanisms
Authors: Smaili Ahmad , Diab Nadim
Published: June 2008

The aim of this article is to provide a simple method to solve the mixed exact-approximate dimensional synthesis problem of planar mechanism. The method results in a mechanism that can traverse a closed path with the choice of any number of exact points while the rest are approximate points. The algorithm is based on optimum synthesis rather than on precision position methods. Ant-gradient search is applied on an objective function based on log10 of the error between the desired positions and those generated by the optimum solution. The log10 function discriminates on the side of generating miniscule errors (on the order of 10−14) at the exact points while allowing for higher errors at the approximate positions. The algorithm is tested by way of five examples. One of these examples was used to test exact/approximate synthesis method based on precision point synthesis approach.
Residue Level Inverse Kinematics of Peptide Chains in the Presence of Observation Inaccuracies and Bond Length Changes
Authors: Subramanian Raghavendran , Kazerounian Kazem
Published: June 2008

Dihedral angles as generalized coordinates define the geometric conformation of a peptide chain. Given the exact coordinates of the atoms, it is possible to rigorously calculate the dihedral angles. We will refer to this calculation process as the residue level inverse kinematics of peptide chains. However uncertainties and experimental observation inaccuracies in the atoms’ coordinates handicap this otherwise simple and straightforward process. In this paper, we present three new efficient methodologies to find all the dihedral angles of a peptide chain for a given conformation. Comparison of these results with the dihedral angle values reported in the PDB (Protein Data Bank) indicates significant improvements. While these improvements benefit most modeling methods in protein analysis, it is in particular, very significant in homology modeling where the dihedral angles are the structural variables. The first method presented here fits a best plane through five atoms of each peptide unit. The angle between the successive planes is defined as the dihedral angle. The second method is based on the Zero-Position analysis method. Successive links in this method rotate by the dihedral angles so as to minimize the structural error between respective atoms in the model conformation with given atoms’ coordinates. Dihedral angle final values correspond to the minimum structural error configuration. In this method, singular value decomposition (SVD) technique is used to best fit the atoms in the two conformations. The third method is a variant of the second method. In this instead of rotating all the links successively only three links are matched each time to extract the dihedral angle of the middle link. By doing so, the error accumulation on the successive links is reduced. This paper focuses on the Euclidean norm as the measure of merit (structural error) to compare different methods with the Protein Data Bank (PDB). This Euclidean norm is further, minimized by optimizing the geometrical features of the peptide plane.
Real-Time Robot Capability Analysis
Authors: Pholsiri Chalongrath , Kapoor Chetan , Tesar Delbert
Published: June 2008

Robot Capability Analysis (RCA) is a process in which force/motion capabilities of a manipulator are evaluated. It is very useful in both the design and operational phases of robotics. Traditionally, ellipsoids and polytopes are used to both graphically and numerically represent these capabilities. Ellipsoids are computationally efficient but tend to underestimate while polytopes are accurate but computationally intensive. This article proposes a new approach to RCA called the Vector Expansion (VE) method. The VE method offers accurate estimates of robot capabilities in real time and therefore is very suitable in applications like task-based decision making or online path planning. In addition, this method can provide information about the joint that is limiting a robot capability at a given time, thus giving an insight as to how to improve the performance of the robot. This method is then used to estimate capabilities of 4-DOF planar robots and the results discussed and compared with the conventional ellipsoid method. The proposed method is also successfully applied to the 7-DOF Mitsubishi PA10-7C robot.
Supension System Vehicle Design Using a Local Optimization Procedure
Authors: Sancibrian Ramon , Garcia Pablo , Viadero Fernando , Fernandez Alfonso
Published: June 2008

This paper deals with the design of double-wishbone and multilink independent suspension systems. To achieve this objective, the proposed method uses a dimensional synthesis technique based on local optimization. An objective function is defined using exact-gradient determination to search for the optimal solution. The multibody system is described by a set of constraint equations which are used to perform the necessary differentiation. Due to the kinematic characteristics of suspension systems, the technique developed here provides a valuable tool for obtaining the optimal solution fulfilling typical requirements imposed in this kind of problems. In this way, double-wishbone and multilink mechanisms are synthesized solving path generation and rigid-body guidance problems at the same time. Finally, two examples are shown to illustrate the application of the method to this kind of systems.
Kinematic Analyses of 5-DOF 3-RCRR Parallel Mechanism
Authors: Huang Zhen , Zhu Si J.
Published: June 2008

This paper presents the kinematic analyses of a 5-DOF 3-RCRR parallel mechanism. The end-effector of this mechanism can rotate round rotation center and one reference point on it can translate in a plane parallels to the base platform. Since the traditional Kutzbach-Gru¨bler formula is not valid for this mechanism, the modified Kutzbach-Gru¨bler formula and screw theory are used in the mobility analysis. The Duffy’s spherical analytic theory is used in forward/reverse position analyses. In forward/reverse velocity/acceleration analyses, virtual mechanism principle is used to build a virtual parallel mechanism (3-PvRCRR), which is equivalent to the initial mechanism (3-RCRR) on kinematics if all rates of virtual pairs (Pv) are set to be zero. At the end, some kinematics curves are presented with a numerical example.
Orientation-Singularity and Orientation Capability Analyses of the Stewart-Gough Manipulator
Authors: Cao Y. , Huang Z. , Ge Q. J.
Published: June 2008

In this paper, the orientation-singularity and orientation capability analyses of the Stewart-Gough manipulator are presented. Based on a particular kind of orientation representation of the manipulator, a polynomial expression of degree thirteen is derived, which represents the orientation-singularity locus of the manipulator at a given position, and examples are given to illustrate the result. The description of the orientation capability of the manipulator and the orientation capability index are discussed. In addition, effects of the geometry parameters of the moving platform, including the central angle, the ratio of the moving platform to the base one and the position of the moving platform on the orientation capability of the manipulator are also presented in this paper.
Tooth Profile Modifications for Optimum Dynamic Load in Spur Gears Based on Pseudo-Interference Stiffness Estimation Method
Authors: Pimsarn Monsak , Kazerounian Kazem
Published: June 2008

A systematic methodology combining optimization, three dimensional analytical rigid body dynamics and a novel method, namely, Pseudo-Interference Stiffness Estimation method (PISE) [1]- [2], is proposed to dramatically reduce gear design time and improve the spur gear system dynamic performance. The main aim of this methodology is to search for the pro les of tooth crowning and shaving that eventually lead to the optimum dynamic tooth load in the gear mesh. An example of the detailed design study is numerically investigated. The results show that the dynamic tooth load can be reduced to up to 50 percent of its original value. However, this reduction is only valid at the operating ranges of the design load and design speed. It is also found that the effect of pro le modi cation on the dynamic response of the gear system was mostly observed to be a reduction in the peak dynamic tooth load at the resonance speed. Later, the investigation of gear tooth durability was conducted to validate an improvement of gear life. The rating factors given in AGMA publication, Hertzian contact stress, bending fatigue stress, ash temperature and PV index are employed in gear durability determination. The results show that, with the reduction of 50 percent in dynamic tooth load, the reductions in PV index, bending fatigue, Hertzian contact stress, and ash temperature can be achieved up to 64, 58, 28 and 39 percent, respectively.
A Robotized Needle Insertion Device for Percutaneous Procedures
Authors: Piccin Olivier , Renaud Pierre , Barbe´ Laurent , Bayle Bernard , Maurin Benjamin , de Mathelin Michel
Published: June 2008

In this paper, a new robotized needle insertion device is proposed for computer-assisted percutaneous therapy. The insertion device is integrated in a robotic system dedicated to gesture guidance in a Computed Tomography (CT) scan. The presented design fulfills the stringent requirements of such a medical application: compatibility with a CT-scan and haptic control by the practitioner are ensured as well as safety and sterilization. The novel design of the insertion device is first presented, outlining its main properties, before introducing preliminary experimental results.
Wide Curve Based Geometric Optimization of Compliant Mechanisms
Authors: Zhou Hong , Ting Kwun-Lon
Published: June 2008

A wide curve is a curve with width or cross-section. This paper presents a geometric optimization method of compliant mechanisms based on the free form wide curve theory. With the proposed method, geometric optimization can be performed to further improve the performance of a compliant mechanism after its topology is selected. Every connection in the topology is represented as a parametric wide curve in which variable shape and size are fully described and conveniently controlled by the limited number of parameters. The geometric optimization is formulated on the control parameters of the wide curves corresponding to all connections in the topology. Problem-dependent objectives are optimized and practical constraints are imposed during the optimization process. The optimization problem is solved by the constrained nonlinear programming algorithm in Matlab Optimization Toolbox. An example is presented to verify the effectiveness of the proposed optimization procedure.
Laplace and Extended Adjacency Matrices for Isomorphism Detection of Kinematic Chains Using the Characteristic Polynomial Approach
Authors: Sunkari Rajesh Pavan , Schmidt Linda C.
Published: June 2008

The kinematic chain isomorphism problem is one of the most challenging problems facing mechanism researchers. Methods using the spectral properties, characteristic polynomial and eigenvectors, of the graph related matrices were developed in literature for isomorphism detection. Detection of isomorphism using only the spectral properties corresponds to a polynomial time isomorphism detection algorithm. However, most of the methods used are either computationally inefficient or unreliable (i.e., failing to identify non-isomorphic chains). This work establishes the reliability of using the characteristic polynomial of the Laplace matrix for isomorphism detection of a kinematic chain. The Laplace matrix of a graph is used extensively in the field of algebraic graph theory for characterizing a graph using its spectral properties. The reliability in isomorphism detection of the characteristic polynomial of the Laplace matrix was comparable with that of the adjacency matrix. However, using the characteristic polynomials of both the matrices is superior to using either method alone. In search for a single matrix whose characteristic polynomial unfailingly detects isomorphism, novel matrices called the extended adjacency matrices are developed. The reliability of the characteristic polynomials of these matrices is established. One of the proposed extended adjacency matrices is shown to be the best graph matrix for isomorphism detection using the characteristic polynomial approach.
Critical Review of Existing Degeneracy Testing and Mobility Type Identification Algorithms for Kinematic Chains
Authors: Sunkari Rajesh Pavan , Schmidt Linda C.
Published: June 2008

Mobility analysis is one of the fundamental problems of structural studies of kinematic chains. Degeneracy testing, an important step in structural synthesis, can be considered as a part of the mobility analysis due to the similarity of the two problems. One common error in the algorithms for these two problems is the assumption that the graph of a planar kinematic chain is a planar graph. This work shows that almost all the mobility analysis algorithms, except that of Lee and Yoon, have this error. This work also critically reviews the two most efficient algorithms on degeneracy testing, those by Hwang and Hwang, and Lee and Yoon. It is shown that due to the errors in the Hwang and Hwang’s algorithm, it failed to identify some of the degenerate chains. Furthermore, the accuracy of the Lee and Yoon’s algorithms for mobility analysis and degeneracy testing is proved by providing the mathematical justification of the individual steps of the algorithms.
Static Balancing of Tensegrity Mechanisms
Authors: Arsenault Marc , Gosselin Cle´ment M.
Published: June 2008

The computation of the equilibrium configurations of tensegrity mechanisms is often a very tedious task even for relatively simple architectures. However, it has been observed that the complexity of this problem is significantly reduced when gravitational loads are compensated with the use of static balancing techniques. In this work, the general static balancing conditions are adapted for the case of tensegrity mechanisms. Afterwards, the modified conditions are applied to two new spatial three-degree-of-freedom tensegrity mechanisms.
Double-Tensural Bistable Mechanisms (DTBM) With On-Chip Actuation and Spring-Like Post-Bistable Behavior
Authors: Wilcox Daniel L. , Howell Larry L.
Published: June 2008

A set of mechanisms called Double Tensural Bistable Mechanisms (DTBM) is presented. DTBMs are fully compliant linear bistable mechanisms that have two bending segments that undergo tension loading. Five configurations of the DTBM are designed, fabricated using surface micromachining, and tested. Measured force and displacement are compared with finite element analysis (FEA) predictions. For two DTBM configurations, a novel post-switch, large-displacement, low-k linear spring behavior is predicted by the FEA models and verified through experimental testing. On-chip actuation of two devices is achieved using thermomechanical in-plane microactuators (TIMs). The DTBM mechanism set explores a relatively new design space for fully compliant micromechanisms, and mechanisms from this class have promise in such applications as shutter positioning, microvalves, electrical relays, inertial sensors and g/time switches.
Collision Detection of Cylindrical Rigid Bodies Using Line Geometry
Authors: Ketchel John S. , Larochelle Pierre M.
Published: June 2008

This paper presents a novel methodology for detecting collisions of cylindrically shaped rigid bodies moving in three dimensions. This algorithm uses line geometry and dual number algebra to exploit the geometry of right circular cylindrical objects to facilitate the detection of collisions. First, the rigid bodies are modelled with infinite length cylinders and a necessary condition for collision is evaluated. If the necessary condition is not satisfied then the two bodies are not capable of collision. If the necessary condition is satisfied then a collision between the bodies may occur and we proceed to the next stage of the algorithm. In the second stage the bodies are modelled with finite length cylinders and a definitive necessary and sufficient collision detection algorithm is employed. The result is a straight-forward and efficient means of detecting collisions of cylindrically shaped bodies moving in three dimensions. This methodology has applications in spatial mechanism design, robot motion planning, workspace analysis of parallel kinematic machines such as Stewart-Gough platforms, nuclear physics, medical research, computer graphics and well drilling. A case study examining a spatial 4C robotic mechanism for self collisions is included.
Geometric Characterization of the Configuration Space of Rigid Body Mechanisms in Regular and Singular Points
Authors: Mu¨ller Andreas
Published: June 2008

The kinematics of rigid body mechanisms is considered from a differential-geometric perspective. Geometric properties of a mechanism are intrinsically determined by the topology of its configuration space — the solution set of closure functions. The mechanism kinematics is usually characterized by the tangent space and tangent cone to the configuration space, i.e. by locally considering its topology. There are, however, mechanisms for which this is not sufficient. Generally, beside the topology, a complete picture of the kinematics needs both, the configuration space and the ideal generated by the closure functions. Tangent spaces/cones are differential-geometric objects associated to a variety. Two additional objects are introduced in this paper: the kinematic tangent space and the kinematic tangent cone. Three locally equivalent models for the mechanism kinematics are introduced. Due to their different mathematical nature the different models admit to apply specific mathematical tools. The analysis of model I is based on Lie group and screw algebraic methods, while model II and III are analyzed using methods from algebraic geometry. A computationally efficient algorithm for the construction of the kinematic tangent cone is presented. Its application is shown for several examples. A novel mechanism is presented of which the differential and local degree of freedom are different in regular points, so-called ‘paradox-in-the-small’.
On the Polynomial Solution of the Synthesis of Five Plane-Sphere Contacts or PPS Chains That Guide a Rigid Body Through Six Assigned Poses
Authors: Di Gregorio Raffaele
Published: June 2008

A new polynomial solution to the synthesis of the body guided by plane-sphere contacts through six assigned poses will be presented. The proposed procedure starts from a system of seven quadratic compatibility equations in seven unknowns and computes a 10th-degree eliminant without passing through a fictitious polynomial equation with degree greater than ten. In particular, the proposed solution procedure requires the computation of the determinant of a 30×30 matrix that has 20 columns with constant entries and the remaining 10 columns with entries that are linear in one out of the seven unknowns. The entries of this matrix are obtained by simply permuting the coefficients appearing in the compatibility equations. Moreover, it will be shown that, due to the special structure of this matrix, the solution procedure can be reduced further so that it involves only the computation of the determinant of a 10×10 matrix. Finally, the proposed procedure is applied to a real case.
Bifurcation Characteristics of Six-Bar Linkages
Authors: Wang Yu-Xin , Guo Rui-Qin
Published: June 2008

Analysis and evaluation of singularities play an important role in several aspects of mechanisms and robotics including design, trajectory planning, and control. In this paper, taking the Watt linkage as an example, the bifurcation characteristics of a six-bar linkage have been investigated. It has been found that the bifurcation characteristics of the mechanism belong to the turning point bifurcation and sometimes a kind of dual turning point bifurcation will take place, and selecting different driving link and Ground, the bifurcation characteristics will not be changed but it only has effects on the number of singularities.
Some Special Cases of the Burmester Problem for Four and Five Poses
Authors: Angeles Jorge , Bai Shaoping
Published: June 2008

The Burmester problem aims at finding the geometric parameters of a planar four-bar linkage for a prescribed set of finitely separated poses. The synthesis related to the Burmester problem deals with both revolute-revolute (RR) and prismatic-revolute (PR) dyads. A PR dyad is a special case of RR dyad, i.e., a dyad with one end-point at infinity. The special nature of PR dyads warrants a special treatment, outside of the general methods of four-bar linkage synthesis, which target mainly RR dyads. In this paper, we study the synthesis of planar four-bar linkages addressing the problem of the determination of PR dyads. The conditions for the presence of PR dyads with the prescribed poses are derived. A synthesis method is developed by resorting to the parallelism condition of the displacement vectors of the circle points of PR dyads. We show that the “circle” point of a PR dyad can be determined as one common intersection of three or four circles, depending on whether four or, correspondingly, five poses are prescribed.
Robustness Study of Generic and Non-Generic 3R Positioning Manipulators
Authors: Caro Stephane , Wenger Philippe , Bennis Fouad
Published: June 2008

This paper presents a robustness study of 3R manipulators and aims at answering the following question: are generic manipulators more robust than non-generic manipulators? We exploit several properties specific to 3R manipulators such as singularities, cuspidality, homotopy classes, and path feasibility, in order to find some correlations between genericity and robustness concepts. For instance, we show that generic manipulators, close to non-generic ones in the space of geometric parameters, are not robust with respect to their homotopy class and to the feasibility of paths. Moreover, we notice that the dexterity and the accuracy of 3R manipulator do not depend on genericity.
Mobility Determination of Paradoxical Linkages
Authors: Rico Jose´ Mari´a , Ravani Bahram
Published: June 2008

It is well known that the Kutzbach-Gru¨bler criterion fails in computing the mobility of exceptional and paradoxical linkages, these two classes of linkages are sometimes referred to as overconstrained. Recently, the authors [1] developed a new mobility criterion that correctly computes the mobility of trivial and exceptional linkages. In the form presented in [1; 2] the mobility criterion can not compute the mobility of paradoxical linkages. This paper presents an extension of the mobility criterion developed by the authors that allows the computation of the degrees-of-freedom of large classes of paradoxical linkages, the conditions for taking advantage of this extension are revealed. Moreover, a hypothesis for applying this extension to classical paradoxical linkages such as the Bennett and Goldberg linkages is presented. Several examples are used to illustrate the method.
Kinematics of a H-Type Pure Translational Parallel Manipulator
Authors: Lee Chung-Ching , Chiu Jeng-Hong , Wu Hung-Hui
Published: June 2008

From the viewpoint of kinematics, a three-dof H-type pure translational parallel manipulator is presented for the development of automatic assembly devices and a regional structure of a six-dof hybrid parallel platform. First, we describe the structural properties of manipulator and analyze its kinematic mobility. A pure translational motion is verified to exist through the well-known D-H symbolic notations and the coordinate transformation technique. What follows are the forward and inverse kinematic analysis and their analytical closed-form solutions by the matrix algebra approach. For further confirmation of the derived equations, some numerical examples are also given. Moreover, with the help of the analytical displacement kinematics, we identify the volume of workspace. At last, taking account of the overall Jacobian matrix provides the condition number and the identification of singularity of configuration is explored based on the direct and inverse kinematics Jacobian matrix.
Gait Rehabilitation With an Active Leg Orthosis
Authors: Banala Sai K. , Agrawal Sunil K.
Published: June 2008

In this paper, we discuss the design and control strategies for an active gait rehabilitation device for the lower extrmity. This device uses gravity balancing to reduce the net torque required by the actuators during motion. Two controllers are proposed in this paper. The first uses a robust controller and the second uses a torque assisting control law. Simulations of these controllers are presented in this paper. Experiments are currently being conducted with this orthosis on healthy and stroke subjects.
Design for Improved Trans-Tibial Prosthetic Devices Using Four Bar Mechanisms
Authors: Wells Joseph G. , Voglewede Philip A. , Rocheleau David N.
Published: June 2008

Currently available prosthetic devices for trans-tibial (below the knee) amputees allow a great deal of mobility, but they do not allow amputees to walk with a normal gait. Most designs utilize passive elements to approximate the complex nonlinear response of the foot and ankle. This paper outlines early work in the design of a hybrid passive/active prosthesis that uses the inherent nonlinearity of a four bar mechanism and the power of numerical optimization to more closely duplicate the function of the human foot/ankle complex during walking.