SOAR: Smartweld optimization and analysis routines

A suite of MATLAB-based code modules has been developed to provide optimal weld schedules, regulating weld process parameters for C0[sub 2] and pulse ND:YAG laser welding methods, and arc welding in support of the Smartweld manufacturing initiative. The optimization methodology consists of mixed genetic and gradient-based algorithms to query semi-empirical, nonlinear algebraic models. The optimization output provides heat-input-efficient welds for user-specified weld dimensions. User querying of all weld models is available to examine sub-optimal schedules. In addition, a heat conduction equation solver for 2-D heat flow is available to provide the user with an additional check of weld thermal effects. The inclusion of thermodynamic properties allows the extension of the empirical models to include materials other than those tested. All solution methods are provided with graphical user interfaces and display pertinent results in two and three-dimensional form. The code architecture provides an extensible framework to add an arbitrary number of modules

SOAR: An extensible suite of codes for weld analysis and optimal weld schedules

A suite of MATLAB-based code modules has been developed to provide optimal weld schedules, regulating weld process parameters for CO2 and pulse Nd:YAG laser welding methods, and arc welding in support of the Smartweld manufacturing initiative at Sandia National Laboratories. The optimization methodology consists of mixed genetic and gradient-based algorithms to query semi-empirical, nonlinear algebraic models. The optimization output provides heat-input-efficient welds for user-specified weld dimensions. User querying of all weld models is available to examine sub-optimal schedules. In addition, a heat conduction equation solver for 2-D heat flow is available to provide the user with an additional check of weld thermal effects. The inclusion of thermodynamic properties allows the extension of the empirical models to include materials other than those tested. All solution methods are provided with graphical user interfaces and display pertinent results in two and three-dimensional form. The code architecture provides an extensible framework to add an arbitrary number of modules

Weld procedure development with OSLW - optimization software for laser welding

Weld procedure development can require extensive experimentation, in-depth process knowledge, and is further complicated by the fact that there are often multiple sets of parameters that will meet the weld requirements. Choosing among these multiple weld procedures can be hastened with computer models that find parameters to meet selected weld dimensional requirements while simultaneously optimizing important figures of merit. Software is described that performs this task for CO{sub 2} laser beam welding. The models are based on dimensionless parameter correlations that are derived from solutions to the moving heat source equations. The use of both handbook and empirically verified thermophysical property values allows OSLW to be extended to many different materials. Graphics displays show the resulting solution on contour plots that can be used to further probe the model. The important figures of merit for laser beam welding are energy transfer efficiency and melting efficiency. The application enables the user to input desired weld shape dimensions, select the material to be welded, and to constrain the search problem to meet the application requirements. Successful testing of the software at a laser welding fabricator has validated this tool for weld procedure development

Minimum-time trajectory control of a two-link flexible robotic manipulator

This paper analyzes the experimental and simulation results of a minimum-time trajectory control scheme for a two-link flexible robot. An off-line optimization routine determines a minimum-time, straight line tip trajectory which stays within the torque constraints of the motors and ends in a quiescent state, i.e., no vibrational transients. An efficient finite-element model is used in the optimization to approximate the flexible arm dynamics. The control strategy described here is used to determine the feedback gains for the position, velocity, and strain gage signals from a quadratic cost criterion based on the finite-element model linearized about the straight line tip trajectory. These feedback signals are added to the modeled torque obtained from the optimization routine and used to control the robot arm actuators. The results indicate that this combination of model-based and error-driven control strategies achieves a closer tracking of the desired trajectory and a better handling of modeling errors (such as tip payloads) than either strategy alone

Techniques for controlling a two-link flexible arm

The long length and relatively small cross sectional area of the robotic arms envisioned for use inside of the underground nuclear waste storage tanks will require the control of flexible structures. This will become an important problem in the characterization and remediation of these tanks. We are developing control strategies to actively damp residual vibrations in flexible robotic arms caused by high speed motion and abrupt external forces. A planar, two-link flexible arm is currently being used to test these control strategies. In this paper, two methods of control are discussed. The first is a minimum-time control approach which utilizes a finite element model and and optimization program. These tools plan the motor torque profiles necessary for the tip of the arm to move along a straight line, in minimum time, within the motors' torque constraints, and end in a quiescent state. To account for modeling errors in the finite element model, errors in joint angles, velocities, and link curvatures are added to the optimal torque trajectory. Linear quadratic Gaussian (LQG) regulatory design theory is used to determine the feedback gains. The second method of control is a teleoperated joystick controller which uses an input shaping technique to alter the commands of the joystick so as to reduce the residual vibration of the fundamental modes. Approximating the system as linear, the natural frequency and damping ratio are estimated on-line for the complete system, which includes the structure plus a lower level proportional derivative controller. An input shaping filter is determined from the estimated natural frequency, estimated damping ratio, and the desired transfer function of the system. 11 reps., 9 figs

Family environment, expressed emotion and adolescent self-harm: a review of conceptual, empirical, cross-cultural and clinical perspectives

Self-harm in young people is a complex and pervasive problem with a number of co-existing risk factors. Although research has implicated a range of family variables in understanding the onset, maintenance and prevention of adolescent self-harm, relatively little attention has been given to the expressed emotion (EE) construct. Based on a narrative review and synthesis of peer-reviewed literature up to and including 2011, this paper considers the conceptual background and empirical evidence for the role of family environment in the expression of adolescent self-harm, with a particular focus on EE. The clinical implications of this literature for working with young people and families from different cultures are also addressed. In summary, the surveyed research provides insufficient evidence for a direct causal link between family environment and adolescent self-harm, with questions raised about the temporal sequencing of measured variables, specificity of implicated family risk factors, and the nature and role of protective factors in families. Emerging evidence for an association between high EE and adolescent self-harm requires replication in well-controlled, prospective studies. There is also a lack of empirically-supported, family-based treatment modalities for adolescents who self-harm. Intervention strategies should be guided by personalised formulation, taking into account individual vulnerabilities, strengths and social contexts, as well as cultural norms for family environment