A neural network-based classification of environment dynamicsmodels for compliant control of manipulation robots

In this paper, a new method for selecting the appropriate compliance control parameters for robot machining tasks based on connectionist classification of unknown dynamic environments, is proposed. The method classifies the type of environment by using multilayer perceptron, and then, determines the control parameters for compliance control using the estimated characteristics. An important feature is that the process of pattern association can work in an on-line mode as a part of selected compliance control algorithm. Convergence process is improved by using evolutionary approach (genetic algorithms) in order to choose the optimal topology of the proposed multilayer perceptron. Compliant motion simulation experiments with robotic arm placed in contact with dynamic environment, described by the stiffness model and by the general impedance model, have been performed in order to verify the proposed approach.     

Control of manipulation robots interacting with dynamicenvironment: Implementation and experiments

In this paper, simulation experiments with different control laws are given, based on a new approach to solving the control tasks for robots in contact with the environment. The comparison of these control laws with the improved versions of the traditional hybrid control are also analyzed. The simulation experiments performed on a real-scale six-degrees-of-freedom industrial robot demonstrate the advantage of the new control concept and improved performances of the robot interacting with a dynamic environment. The tests conducted on industrial robot Manutec r3 are also presented     

NMR characterization of intermolecular interactions for polymers,IV. Intermolecular interactions of low molecular weight analogues for compatible blends of polystyrene and poly(2,6-dimethyl-1,4-phenylene oxide)

The intermolecular interaction, IMI, leading to the compatibility of polystyrene, PS, and poly (2,6-dimethyl-1,4-phenylene oxide), PPO, has been identified by analyzing the IMI of the model compounds of low molecular weight; cumene, styrene oligomer, 2,6-dimethyl phenol, and its trimer. The IMI has been detected and identified applying Rummens' method for the analysis of the solvent-induced changes in NMR chemical shifts. The results indicate that the driving force in the formation of the compatible blend of PS and PPO is the π-hydrogen bond between the electrodeficient methyl groups in PPO and π-orbitals in PS. There were no indications that n-hydrogen bonds are formed between ring hydrogens of PS and the oxygen in PPO.     

Nonadaptive dynamic control for manipulation robots: Centralized or decentralized control

Different concepts for dynamic control of manipulation robots are presented. Principles for the synthesis of optimal control, optimal regulator, “inverse problem” technique, force feedback, decoupled control, and decentralized control are considered. An attempt is made to provide a comparative analysis of all the stated control algorithms and to point out the advantage of decentralized control concept.     

Adaptive control of single rigid robotic manipulators interacting with dynamic environment — An overview

This paper presents the current state of the art in the adaptive control of single rigid robotic manipulators in the constrained motion tasks. A complete mathematical model of a single rigid robotic manipulator in contact with dynamic environment is presented. The basic approaches in deriving the environment model are given. The significance of the dynamic environment in the scope of the stability problem of the whole system robot-dynamic environment is emphasized. A classification of the adaptive contact control concepts in manipulation robotics is presented. The main characteristics of the most important adaptive strategies in constrained manipulation are given. The advantages and the drawbacks of the presented methods are emphasized. The paper covers results published a few years ago, as well as some recent trends in this field. One important result in the stability analysis of robotic manipulators in the constrained motion tasks is reported. Finally, some concluding remarks are given and possible future investigation trends in adaptive control of robotic manipulators are indicated.     

Bimetallic and Ternary Alloys for Improved Oxygen Reduction Catalysis

Using a combination of density functional theory (DFT) calculations and an array of experimental techniques including in situ X-ray absorption spectroscopy, we identified, synthesized, and tested successfully a new class of electrocatalysts for the oxygen reduction reaction (ORR) that were based on monolayers of Pt deposited on different late transition metals (Au, Pd, Ir, Rh, or Ru), of which the Pd-supported Pt monolayer had the highest ORR activity. The amount of Pt used was further decreased by replacing part of the Pt monolayer with a third late transition metal (Au, Pd, Ir, Rh, Ru, Re, or Os). Several of these mixed Pt monolayers deposited on Pd single crystal or on carbon-supported Pd nanoparticles exhibited up to a 20-fold increase in ORR activity on a Pt-mass basis when compared with conventional all-Pt electrocatalysts. DFT calculations showed that their superior activity originated from the interaction between the Pt monolayer and the Pd substrate and from a reduced OH coverage on Pt sites, the result of enhanced destabilization of Pt–OH induced by the oxygenated third metal. This new class of electrocatalysts promises to alleviate the major problems of existing fuel cell technology by simultaneously decreasing materials cost and enhancing performance.     

On a steady, viscous flow in two-dimensional collapsible channels

Two characteristic cases of steady, viscous flow in 2-D collapsible channels are considered in the paper: low Reynolds number, lubrication type flow, and moderately high Reynolds number, boundary-layer type flow. In the latter case the boundary layer occupies the whole cross-section of the channel, and, in order to treat the flow analytically, we apply an approximate method based strongly on the Karman-Pohlhausen method, known from early developments of the classical boundary-layer theory. In modeling the elastic behavior of channel walls, we show how the careful scaling employed in studying the fluid flow imposes the application of geometrically nonlinear Karman shell theory. For the lubrication type flow we derive a single integro-differential equation describing the wall configuration, while in the boundary-layer type flow a similar integro-differential equation is supplemented by two first order, nonlinear ordinary differential equations. In both cases the governing equations are solved numerically by finite differences, for a wide range of control parameters. At that, steady flow was found to exist in all cases considered (we did not perform the stability analysis of the obtained solutions). Also, in the boundary-layer type flow the boundary layer was shown to be very resistant to separation, so that the presented theory was valid over the whole length of the channel. The effect of control parameters, in particular of the volume flow rate and the entrance transmural pressure, upon the wall configuration was discussed.     

Control of Robots with Elastic Joints Interacting with Dynamic Environment

In this paper, the control of robots with elastic joints in contact with dynamic environment is considered. It is shown how control laws synthesized for the robots with rigid joints interacting with dynamic environment can also be used in the case of robots with elastic joints. The proposed control laws are based on a robot model interacting with dynamic environment, including the dynamics of actuators and the elasticity of joints. The proposed control laws possess two feedback loops: the outer, serving for on-line calculation of the motor shaft angle based on the position error or the contact force error, and the inner one, serving for performing stabilization around the calculated motor shaft angle. Simulation results which exhibit the application of the appropriate control laws are also presented.     

Impedance Control as a Particular Case of the Unified Approach to the Control of Robots Interacting with a Dynamic Known Environment

This paper investigates the problem of impendance control using a unified approach to contact tasks control in robotics, where the interpretation of the contact between the robot and its known environment is based on a sufficiently correct treating of interaction between the environment and robot dynamics. Apart from brief survey of all more important results in the field of impedance control, it will be shown that, from the standpoint of the active compliance method which considers the control with respect to position and force simultaneously, impedance control can be considered as one particular case. The direct aim of the paper is to improve the transient dynamic response immediately after the contact. In that way the performance of impedance control is improved just in the phase in which its quality is of decisive importance.