In this paper, we outline the two alternatives we faced in implementing a hypermedia-based educational software for analyzing planar mechanisms by both global and modular approaches. Our software uses a “spatial” information allocation, which is consistent with the physical nature of the problems involved in mechanism simulation, and which follows the paradigm of object-oriented programming. The hypermedia material developed and furnished to students allows them to explore, to carry out individual experiments, to work out projects, and to draw up reports concerning kinematic analysis of linkages.

This paper examines the problem of identifying the assembly configurations (ACs), also called circuits, of planar non-single-input-dyadic (NSID) mechanisms. An SID mechanism is a multi-loop mechanism which can be defined by adding one loop at a time such that the mechanism has one degree of freedom (DOF) after each loop is added. An NSID mechanism is any mechanism that does not meet the SID criterion. This includes all multi-DOF mechanisms, and some complex single-DOF mechanisms. An automatic, method is presented which allows a computer to determine the ACs of an NSID mechanism. For single-DOF mechanisms, the ACs are represented by curves drawn in a plane represented by two joint variables. For multi-DOF mechanisms, the ACs consist of one or more regions in the plane, which are defined by the curves that bound, them. The automated method finds these bounding curves, and then determines which curves belong to the same region, and which regions belong to the same AC. Mechanisms with pin joints and sliding joints are considered.

Robot kinematics generally includes forward and inverse kinematics at the position, velocity, and acceleration level. These constructs are essential for the cartesian control of serial manipulators. This paper presents the development of a C++ class library that supports the forward and inverse kinematics of all possible geometries of serial manipulators. Object-oriented analysis and design is the primary software development methodology used. Application of this methodology led to the sub-division of the kinematics domain into forward, and inverse kinematics. Analysis of these sub-domains resulted in their further sub-division, identification of abstract components, development of classes, interface specifications, and finally implementation and testing. Examples demonstrating programming and extensibility of the components in the kinematics domain are given. This work was part of the development of the Operational Software Components for Advanced Robotics (OSCAR) at the Robotics Research Group of The University of Texas at Austin. OSCAR supports reusable software components for the control of advanced robotic manipulators. This includes mathematical constructs, kinematics, dynamics, fault-tolerance, performance criteria, manual controllers, and a variety of physical manipulators and simulations.

In this paper a systematic way of representing complex cable-pulley mechanism configurations and a method to analyze and synthesize the motion of these cable-pulley devices is presented. The cable-pulley system model that is being considered is composed of three basic elements which are pulleys, blocks, and cables. A configuration table is used to identify the constraint equations by systematically defining the connections between the cables, pulleys, and blocks. The basic strategy is to use the constraint equations to generate the relationship between each variable and a subset of the variables identified as the inputs. The number of input variables is equal to the total number of variables minus the number of independent constraints. This choosing of the set of inputs is done in conjunction with a row reduction process on the system of constraint equations which identifies the number of inputs and ultimately generates the relationships of each variable to the input(s). Examples are given to illustrate the procedure.

This paper discusses kinematics of a 3-RPS parallel pyramid manipulator using the principal screws. Firstly, the principal screws are identified by quadric degeneration. The planar conies representing the relations between the pitches and the three linear inputs are described, and the three-dimensional distribution of the axes of all the twists is illustrated. Finally, a numerical example is given successfully.

This paper examines the problem of finding the assembly configurations, also called circuits, of spatial single-loop single-DOF mechanisms with spheric and planar joints. All six lower pairs are considered: revolute (R), cylindric (C), prismatic (P), helical (H), spheric (S), and planar (E). The RSSR, CSS, CCS, RRSC, RSRC, and RRSRR mechanisms are covered, along with all variations in which an R joint is replaced with a P or H joint, or an S joint is replaced with an E joint. A numerical method is given to find the ACs, and is illustrated with several examples.

This paper studies the geometric design of spatial two degrees of freedom, open loop robot manipulators with revolute joints that perform tasks, which require the positioning of the end-effector in three spatial locations. This research is important in situations where a robotic manipulator or mechanism with a small number of joint degrees of freedom is designed to perform higher degree of freedom end-effector tasks. The loop-closure geometric equations provide eighteen design equations in eighteen unknowns. Polynomial Elimination techniques are used to solve these equations and obtain the manipulator Denavit and Hartenberg parameters. A sixth order polynomial is obtained in one of the design parameters. Only two of the six roots of the polynomial are real and they correspond to two different robot manipulators that can reach the desired end-effector poses.

This paper examines the problem of finding the assembly configurations, also called circuits, of spatial single-loop single-DOF mechanisms with five or more links. The RRRCC, RRCRC, RRRRCR, and RRRRRRR mechanisms are covered, along with all variations in which a revolute (R) joint is replaced by a prismatic (P) joint. A numerical method is given to find the ACs, and is illustrated with several examples.

This paper examines the problem of identifying the assembly configurations (ACs), also called circuits, of planar multi-loop mechanisms with kinematic limitations, such as joint limits, link interference, collision with stationary obstacles, and workspace limitations. First, a method is given to describe numerically the satisfaction or violation of these kinematic limitations, and then this is applied to find the ACs of mechanisms with kinematic limitations. The method is valid for mechanisms with one or two degrees of freedom, and is illustrated with two examples.

The gait transition models of a quadruped are studied based on gait kinematics and CMAC neural networks are applied to learn and generalize these gait transition models. Three gait transition cases are studied: from wave gait to continuous follow-the-leader gait, from walk to trot, and from trot to gallop. Four solution methods are proposed for solving the gait transition models. Computer simulations are conducted to evaluate and display the gait transition models. The good transition gaits are then selected to train CMAC neural network gait transition models. The performance of the CMAC gait transition models are evaluated and found to be satisfactory.

The design of a novel scanning apparatus used for digitizing dental impression molds is presented. The apparatus consists of a four-degree-of-freedom hybrid spherical linkage capable of moving the dental mold relative to a laser scanner along a curved path in the specified orientations. Since closed form inverse kinematics solutions are not available for the multiple degree-of-freedom spatial mechanism in question, symbolic and numerical computation techniques are used extensively for kinematics analysis, dimension design, and optimization. In addition, mechanical design and simulation software (Pro/Engineer & Pro/Mechanica), as well as the rapid prototyping machines are used to reduce the development cost and cycle time.

This paper presents a novel application for a portable 4-cable-suspended point end-effector robot, that of algae harvesting from large (1–4 acres) outdoor circulating pond systems. Algae, used as an alternative energy crop to produce biofuels (and other consumer products), still remain too expensive. One of the greatest expenses in processing algae is the harvesting process. To replace the typical energy-intensive pumping of the entire pond water through algae filters, we propose using a cable-suspended robot to collect algae, which largely then drains while the robot translates the product to a collection point. An additional benefit of our concept, in additional to lower harvesting cost, is that the algae still growing in the pond is not shocked as in the current pumping process, leading to better, healthier yields.

Humanoid biped robots are typically complex in design, having numerous degrees-of-freedom (DOF) due to the ambitious goal of mimicking the human gait. This paper presents the forward kinematics and dynamics of a new sixteen DOF humanoid biped robot. The synthesis of the kinematic chains is based on human body parameters in terms of ratios, range of motion, and physical length. The paper proposes a new architecture for a biped robot with seven DOF per each leg, adding one DOF that imitates the toe joint. The dynamic model is approached by dividing the legs into the sagittal and frontal planes, which simplifies the mathematical model by further applying the principle of Lagrangian dynamics. The paper contains several simulations and numerical examples to prove the analytical results.

In this paper, a new type of the positioner is proposed, which has with dual-drive and dual-screw. Comparing with the positioner of the traditional gear transmission system, the positioner with the new mechanism has less power and less work space. Based on the designing requirements, we optimized the dimensions of the mechanism of the positioner, and carried out the kinematic and dynamic analysis of the positioner. The strength and the rigidity of the positioner are analyzed by the use of FEM. Finally, according to fuzzy mathematical theory, the reliability of the mechanism motion of the positioner is studied.

A CAD variation geometry approach is proposed for accurately solving the position-orientation, linear velocity/acceleration, and Euler angular velocity/angular acceleration of a symmetrical 3-dof 3-UPU parallel robot. Based on the finite-difference method as the foundations, using the computer aided geometry constraints and dimension driving technique, the simulation mechanism of the 3-UPU parallel robot with Euler angles is created, and the position-orientation can be got. Then the linear velocity/acceleration simulation mechanisms and Euler angular velocity/angular acceleration simulation mechanisms are created. When modifying the driving dimension of three driving limbs, the configurations of the simulation mechanisms are varied correspondingly, and all of the kinematical parameters are solved automatically. The simulation solutions are verified by an analytic approach. The results show that the CAD variation geometry is not only fairly quick and straightforward, but is also advantageous from viewpoint of accuracy and repeatability.

In this paper the generic DOF of mechanisms is investigated. This is the DOF of almost all mechanisms, that can be built from a given set of kinematic pairs in a certain arrangement, but with arbitrary link geometry. In particular, this is the most likely DOF in the presence of link imperfections. The local DOF of a mechanism is the dimension of its configuration space. The differential DOF is the number of linearly independent velocity constraints. It is pointed out, that the local DOF can not always be inferred from the number of constraints (overconstrained mechanisms) nor can the differential DOF always be deduced from the local DOF. It is proven, that the generic DOF of a mechanism is given by the Chebychev-Kutzbach-Gru¨bler formula δ = Σ α f a − g ( j − b + 1 ) , with b and j the number of bodies and joints, and f α the DOF of joint α . Consequently, almost all mechanism are trivial, i.e. not overconstrained.

This paper applies the ‘technomimetics’ concept to generate a new class of parallel mechanisms inspired by origami folds. This new class of 3-DOF (Degree of Freedom) parallel mechanisms is constructed with 3- RPRP architecture. When the geometric constraints mentioned in this paper are applied, the mechanisms will be allowed to rotate around the x and y axes and translate vertically along the z axis, while the centre of the platform remains concentric to the centre of its base. This paper investigates both position and geometry of these mechanisms and identifies the closed form solutions for the inverse kinematics problem. The differential kinematical analysis is developed by deriving the Jacobian matrix through screw theory and the singularities are identified with workspace analysis. The paper ends with isotropic configuration analysis and illustrates the characteristics of the new mechanisms.

This paper deals with the design of steering mechanisms in road vehicles. With this aim, the kinematic models of three types of steering linkages are considered and Ackermann steering geometry is used to define the objective function. The proposed method uses a dimensional synthesis technique based on local optimization to obtain the dimensions of the links. The problem is formulated as function generator synthesis, where the inner wheel is supported by the input link and the output link is supported by the outer wheel. The formulation presented in this paper was developed by the authors and it is capable of considering the necessary accuracy conditions in the design of this kind of linkage. Three examples are shown to illustrate the application of the method.

Visualization and spatial reasoning are integral to developing an understanding of contemporary sciences. They form the basis for understanding a wide variety of topics across science, mathematics and engineering, including molecular structures, topologies, motion and forces, and manufacturing processes. Within engineering, it can be argued that challenging and time consuming topics such as kinematics can be better taught by faculty, and hence better understood and appreciated by students, by advancing our understanding of human visualization and spatial reasoning and using this knowledge to develop computer-based visualization instruction in ways that maximize their effectiveness. The achievement of such a goal will require importing proven extant theories from other fields such as psychology, education, engineering and computer science. This paper presents the results of one such effort for teaching engineering kinematics. The motivation for this work can be found in cognitive science literature, where motion comprehension has been identified and studied as a mental task. Accordingly, a major task in doing this work involved the study of cognitive models of motion comprehension, and identifying key stages present in them. Mapping such key stages in motion comprehension on to kinematics domain, this paper presents the framework for the visual comprehension based pedagogical approach to kinematics. A web-based gear-trains tutor has been developed to demonstrate this concept. Results from the tests on a controlled population of engineering students are presented and the efficacy of a visual comprehension based approach as an instructional tool is discussed.

The instantaneous forward problem (IFP) singularities of a parallel manipulator (PM) must be determined during the manipulator design and avoided during the manipulator operation, because they are configurations where the end-effector pose (position and orientation) cannot be controlled by acting on the actuators any longer, and the internal loads of some links become infinite. When the actuators are locked, PMs become structures consisting of one rigid body (platform) connected to another rigid body (base) by means of a number of kinematic chains (legs). The geometries (singular geometries) of these structures where the platform can perform infinitesimal motion correspond to the IFP singularities of the PMs the structures derive from. In this paper, the singular geometries of the structures with topology SX-YS-ZS (S stands for spherical pair, whereas X, Y and Z stand for three generic one-dof pair which may be or may not be of the same type) are studied with a unified approach. The presented approach leads to obtain an analytic condition which allows all the singular geometries of these structures to be determined. Moreover, the geometric interpretation of the found singularity condition and the exhaustive enumeration of the types of singular geometries is provided. Finally, the use of the presented results in the design of the manipulators which become one structure with topology SX-YS-ZS when the actuators are locked is discussed.