Browsing by Subject "Manipulators (Mechanism)"
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Item Application of the matrix approach to the kinematic modeling and analysis of spaial mechanisms(Texas Tech University, 1995-05) Suryanarayan, Krishna PrasadThe purpose of this thesis is to apply the homogeneous matrix transformation approach to the design of automotive alignment mechanisms and to briefly review its application to the kinematic analysis of a hyper-redundant manipulator. The homogeneous matrix transformation approach allows the determination of the position, velocity and acceleration of any point on the mechanism, defined in local coordinates, with respect to the world coordinate system, from a knowledge of the joint and link parameters. This homogeneous matrix method presents itself as a unique tool in the analysis of automotive alignment mechanisms as currently, these mechanisms are designed using geometric methods which involve tedious calculations. By the application of this matrix approach to their analysis, the design process is greatly simplified and it enables the design of these mechanisms to be easily implemented by breaking the design into smaller modules which are then solved individually to yield the final solution. Additionally, an investigation is performed to show the use of this matrix approach in the study of the kinematics of a hyper-redundant manipulator which is composed of wedge shaped discs.Item Determination of Repeatability of a Limited Sequence Control Industrial Robot(Texas Tech University, 1983-08) Kajila, SadanandaNot Available.Item Geometric-based spatial path planning(2008-08) March, Peter Setterlund, 1978-; Tesar, DelbertCartesian space path planning involves generating the position and orientation trajectories for a manipulator end-effector. Currently, much of the literature in motion planning for robotics concentrates on topics such as obstacle avoidance, dynamic optimizations, or high-level task planning. The focus of this research is on operator-generated motions. This will involve analytically studying the effects of higher-order properties (such as curvature and torsion) on the shape of spatial Cartesian curves. A particular emphasis will be placed on developing physical meanings and graphical visualization for these properties to aid the operator in generating geometrically complex motions. This research begins with a brief introduction to the domain of robotics and manipulator motion planning. An overview of work in the area of manipulator motion planning will demonstrate a lack of research on generating geometrically complex spatial paths. To pursue this goal, this report will then provide a review of the theory of algrebraic curves and their higher-order properties. This involves an evaluation of several different representations for both planar and spatial curves. Then, a survey of interactive curve generation techniques will be performed, which will draw from fields outside of robotics such as Computer Graphics and Computer-Aided Design (CAD). In addition to the reviewed methods, a new method for describing and generating spatial curves is proposed and demonstrated. This method begins with the study of a finite set of local geometric motion shapes (circular arcs, cusps, helices, etc). The local geometric shapes are studied in terms of their geometric parameters (curvature and torsion), analyzed to give physical meaning to these parameters, and displayed graphically as a family of curves based on these controlling parameters. This leads to the development of path constraints with well-defined physical meaning. Then, a curve generation method is developed that can convert these geometric constraints into parametric constraints and blend between them to form a complete motion program (cycle) of smooth paths connecting several carefully developed local curve properties. Up to ten distinct local curve shapes were developed in detail and one curve cycle demonstrated how all this could be combined into a full path planning scenario. Finally, the developed methods are packaged together into existing software and applied to an example demonstration.Item Influence of actuator parameters on performance capabilities of serial robotic manipulator systems(2008-08) Rios, Oziel, 1980-; Tesar, DelbertA serial robotic manipulator arm is a complex electro-mechanical system whose performance is primarily characterized by the internal parameters of its actuators. The actuator itself is a complex nonlinear system whose performance can be characterized by the speed and torque capabilities of its motor and its accuracy depends on the resolution of the encoder as well as its ability to resist deformations in its gear train under load. The mechanical gain associated with the gear train transmission is critical to the overall performance of the actuator since it amplifies the motor torque thus improving the force capability of the manipulator housing it, reduces the motor speed to a suitable output speed operating range, dominates the inertia content of the manipulator and amplifies the stiffness improving the precision under load of the overall system. In this work, a basic analytic process that can be used to manage the actuator parameters to obtain an improved arm design based on a set of desired/required performance specifications is laid out. The key to this analytic process is the mapping of the actuator parameters (motor speed, motor torque, rotary stiffness, encoder resolution, transmission efficiency, mass, rotary inertia) to their effective values at the system output via the mechanical gains of the actuator transmissions as well as the effective mechanical gains associated with the manipulator geometry. This forward mapping of the actuator parameters allows the designer to determine how each of the actuator parameters influences the functional capacity of the serial manipulator arm. The analytic formulation is demonstrated to be effective in addressing the issue of configuration management of serial robotic manipulators where the goal is to assemble a system from a finite set of actuator modules that meets some required performance specifications. To this end, four design case studies demonstrating the solution of the configuration management problem are presented where the application domains include designing for light to heavy-duty force applications, designing for responsiveness and designing for Human-Robot Interactions (HRI). The design trade-offs for each of the application domains are analyzed and design guidelines are presented. This research also formulates a new approach to characterizing the dynamic behavior of serial chain mechanisms via the kinetic energy distribution. In any mechanism, the amount of kinetic energy in the system is a very important quantity to analyze. Since the inertial torques are directly related to the rate of change of the kinetic energy, better design (and operation) is achieved by having an understanding of how kinetic energy is distributed along the mechanism structure as well as how rapidly kinetic energy is flowing within it. In this work, a description of the Kinetic Energy Partition Values (KEPV) for serial chain mechanisms, as well as their rates of change, are presented. The KEPVs arise from the partitioning of the mechanism’s kinetic energy. Two design criteria, one based on the KEPVs and another based on their rates of change, are developed. These design criteria are indicators of both the dynamic isotropy of the system as well as the amount of kinetic energy flow within the system. A six-axis spatial manipulator is used to illustrate the solution of a design optimization problem where the goal is to demonstrate how the inertial parameters of the actuators and mechanical gains of the actuator transmissions alter the kinetic energy of the system which is “measured” via an effective mass criterion and its distribution which is measured via the KEPV criterion. It is demonstrated that the mechanical gains in the actuators significantly influence the magnitude of the kinetic energy as well as its distribution within the system.Item Minimum distance influence coefficients for obstacle avoidance in manipulator motion planning(2002) Harden, Troy Anthony; Tesar, DelbertOne weakness of current robotic technology is motion planning. Current robots especially struggle to effectively operate in cluttered environments. In this report, first and second order influence coefficients for minimum distance magnitudes are developed. These coefficients provide fundamental analytics for rates of change of minimum distance magnitudes and allow for deeper insight into the interaction between a manipulator and its environment. They are also demonstrated as viable tools for use in manipulator obstacle avoidance. Influence coefficients are rigorously developed for three simple manipulator and workspace modeling primitives: a sphere, a cylisphere, and a quadrilateral plane. In addition, a general method to use for similar derivations for new modeling primitives is presented. Also, a comparison of the speed and accuracy of using finite differencing to calculate the second order coefficients instead of calculating them analytically is given. The developed influence coefficients provide extraordinary insight into the interactions between a robot and its environment because they isolate the geometry of the distance functions from system inputs (manipulator joint commands). As a demonstration of potential uses of these coefficients, twelve obstacle avoidance criteria based on minimum distances and artificial forces are developed and demonstrated using criteria-based inverse kinematics on a ten degree of freedom manipulator operating around three obstacles. In the demonstration, the zeroth and first order criteria run at an average rate of 1042 hertz and the second order criteria run at an average rate of 2.045 hertz. Using the developed criteria one at a time, the manipulator successfully completed a demanding end-effector path, 5200 setpoints in length, for many of the criteria. In some cases, using higher-order criteria improved manipulator performance. None of the criteria allowed the manipulator to strike the obstacles. This research successfully demonstrates the usefulness of first and second order influence coefficients for minimum distance magnitudes in solving the obstacle avoidance motion-planning problem. The obstacle avoidance results also point to the feasibility of using the developed coefficients to solve a wide range of additional motion-planning problems that focus on how a system interacts with its environment.Item Modeling, simulation and experimental verification of contact/impact dynamics in flexible articulated structures(Texas Tech University, 1998-05) Hariharesan, SeralaathanRobots are used in diverse applications, ranging from entertainment to manufacturing to space applications. Each application has its own requirements in terms of performance, design and operating environment. Based on these requirements, a designer/researcher will have to design a robot that performs its designated task with maximum possible efficiency. Robots are widely used in manufacturing for machining, assembly line operations, welding, painting, inspection, etc. They are also used in a host of other areas like laboratories to place and remove test tubes in centrifuges and to handle hazardous chemicals. In the nuclear industry, they are used to handle radioactive fuel as well as radioactive waste. Robots are also used in remote or highly contaminated areas to measure radiation or toxic levels. Robots have also found their way into the field of agriculture. An interesting application is their use as a sheepshearing machine, where it is used to shear wool off sheep. There are submersible robotic vehicles used for deep sea exploration. These submersible vehicles are used for mining the ocean floor. Last, but not least, there is the space industry which uses robots in various forms. Robots in space applications usually face environments that are hostile to human survival. Planetary rovers with manipulator arms, satellite maintenance robots, manipulator arms for space manufacturing and construction of space stations and space ships and unmanned exploration vehicles are some of the applications of robots in space.Item Physical modeling of tools necessary for robot manipulation(2006) Chang, Kyogun; Tesar, DelbertPrevious research on modeling general processes has focused on physical and empirical modeling of dedicated process machines which have sufficient stiffness and accuracy. For example, machining centers have relatively high stiffness and exhibit negligible deflections. Robot manipulators have low stiffness which easily allows undesirable deflections under large reaction forces. Also, models for intuitive decision surfaces for users, decision making systems, or system controllers have not been embedded or otherwise deployed effectively. The objective of this research is to suggest graphical and parametric models of robotic processes suited for intuitive user friendly graphs and modeling nonlinear systems and to initiate a program which proves usefulness of performance maps. Performance maps are primitive surface representations which can be used to create decision surfaces. General robotic processes considered are robotic drilling, grinding, deburring, chiseling, sawing, peg insertion, force-fit insertion, forming for assembly, screw fastening, and riveting. To achieve the objective, a framework for in-depth parametric and analytic modeling of robotic processes is presented. First, relevant process parameters such as process operating variables, system condition parameters, and process performance criteria are defined. Process operating variables are the robot controller inputs. System condition parameters are process parameters which define system constraints and characteristics. Process performance criteria are critical parameters to define, anticipate, and evaluate product quality, system stability, economic performance, and system performance. Second, performance maps which describe the graphical relationship of the relevant process parameters are developed. A performance map is the surface representation of a process performance criterion as a function of process operating variable(s), system condition parameter(s), or other process performance criteria. Third, the application of performance maps of robotic drilling is simulated, to illustrate their advantages. Whether robot deflections generated during the process satisfy tolerance requirements or not is evaluated and suitable robot postures are recommended. Pertinent literature is extensively reviewed to recognize current research trends in modeling and parameterizing relevant process parameters. Approximately, 100 performance maps were created as graphical and parametric models based on process performance. Two performance envelopes were developed. Proper robot postures were suggested to drill a hole with constant feed-rate or bounded ranges of that feed-rate.Item Task-based decision making and control of robotic manipulators(2004) Pholsiri, Chalongrath; Tesar, Delbert; Kapoor, ChetanItem Task-based resource allocation for improving the reusability of redundant manipulators(2002-05) Pryor, Mitchell Wayne; Tesar, Delbert