Mobile Manipulators (MM) has attracted a lot of researchers for incorporation in the robotics field owning to their multitude of applications in real world. Welding automation has its wide applications in industry like automobile manufacturing and power generation industry involving spherical tanks. The objective of this study is to design workspace and devise a methodology to plan position trajectory of welding tool that produces smooth welding while the mobile platform turns simultaneously. The robot proposed in this paper has the manipulator mounted on a platform moving as a turntable to increase the workspace and enhances the mobility of the manipulator. The earlier produces linear segment of weld while the later produces parabolic segment. The kinematic equations for mobile platform and the mounted manipulator are described in detail. The workspace of the robot is visualized based on computations of transformation matrices and jacobians structured based on kinematic equation. Trajectories for each joint, computed using inverse kinematic equations, are also presented. For spherical trajectories the solution of system equations is combined with constraint values for each manipulator joint, thus allowing computation of desired joint position at any time interval. The efficacy of the proposed methodology for the trajectory planning is tested through a case study. The simulation results of motion transformation, workspace and trajectory show that linear segments of the trajectory combine with parabolic trajectory segments smoothly with zero acceleration within designed reachable workspace. The experimental results verify the efficacy of application of presented kinematic and inverse kinematic models for welding of spherical objects.

The software industry has been evolving over the years. Software maintenance is as crucial as software development. Software maintenance cost has gained a significant important both for practitioners and researchers. Software maintenance cost is very crucial to estimate the productivity of the software, reliability, adaptability, and control. This research investigation is a study that is based on the literature of investigation conducted previously in the field of software maintenance. We have found studies that reveal the effort estimation problems related and have a direct impact on software maintenance. We have also identified problems that have a direct impact on software maintenance. This study will act as a guideline for researchers to counter these problems. This study will act as a platform to classify new direction and initiate full-scale research.

Rehabilitation in the form of locomotion assistance and gait training through robotic exoskeletons requires both precision and accuracy to achieve effective results. The essential challenge is to ensure robust tracking of the reference signal, i.e., of the gait or locomotion. This paper presents the design of model-based (MB) and model-free (MF) robust control strategies to achieve desired performance and robustness in terms of transient behavior and steady-state/tracking error, implementable to the locomotion assistance and gait training by exoskeletons. The dynamic responses of the exoskeleton system were investigated with both the control strategies. The study was carried out with a variety of reference signals and performance was evaluated to identify the best suited approach for rehabilitation exoskeletons. In case of the model-based control, a mathematical model of the system was developed using a bond graph modeling technique and a lead compensated H-infinity reference gain controller was designed to ensure robust tracking performance. In the model-free control strategy, however, the system function is approximated using radial basis function neural networks (RBFNNs) and an adaptive proportional-derivative RBFNN controller was designed to achieve the desired results with minimum tracking error. Both strategies make the system robust and stable. However, the MF control strategy is faster for all reference inputs as compared to the MB control strategy i.e., faster to approach the peak value and settle, and rapidly approaches the zero steady-state/tracking error. The rise time in the case of a sinusoidal input for model-free control is 0.4 s faster than the rise time in model-based control. Similarly, the settling time is 3.9 s faster in the case of model-free control, which is a prominent difference and can provide better rehabilitation results.

The process of material removal from a workpiece to obtain the desired shape is termed machining. Present-day material removal technologies have high spindle speeds and thus allow quick material removal. These high-speed spindles are highly exposed to vibrations and, as a result, the accuracy of the final workpiece’s dimensions is compromised. To overcome this problem, the motion of the tool is restricted, and multiple degrees of freedom are given through the motion of the workpiece in different axes. A machining bed configured as a parallel manipulator capable of giving six degrees of freedom (DOF) to the workpiece is proposed in this regard. However, the proposed six DOF machining bed should be energy efficient to avoid an increase in machining cost. The benefit of using the proposed configuration is a reduction in dimensional error and computational time which, as a result, reduces the energy utilization, vibrations, and machining time in practice. This paper presents kinematics, dynamics and energy efficiency models, and the development of the proposed configuration of the machining bed. The energy efficiency model is derived from the dynamics model. The models are verified in simulation and experimentally. To minimize error and computation time, a PID controller is also designed and tested in simulation as well as experimentally. The resulting energy efficiency is also analyzed. The results verify the efficacy of the proposed configuration of the machining bed, minimizing position error to 2% and reducing computation time by 27%, hence reducing the energy consumption and enhancing the energy efficiency by 60%.

Trajectory planning and tracking are the most important aspects of mobile robot research for industrial application. In this research, an intelligent hybrid control is presented to enhance the usability of mobile robots in environments cluttered with static obstacles. The control is hybrid in two ways. On one hand, the algorithm combines obstacles avoidance and trajectory generation. The generated trajectory acts as a reference path to be followed by the mobile robot. On the other hand, the algorithm not only generates trajectory but also tracks the generated trajectory. An optimization-based intelligent algorithm, simulated annealing, is designed to plan and generate a trajectory for collision-free robot motion in an environment with stationary obstacles. The PID (Proportional-Integral-Derivative) control algorithm is designed to track the generated trajectory with minimum error. Both algorithms are hybridized such that the generated trajectory becomes a reference trajectory for the tracking control algorithm. The simulated annealing generates a realistic trajectory that consists of a series of the best points with obstacles on the path. The best point is selected with the shortest distance from the robot's destination. These points are selected one from each of the grids, generated between the start and destination point of the robot motion. The dimensions of the robot are considered and included in the obstacles dimension to reduce the dimension complexity of the robot. The effectiveness of the proposed hybrid technique is tested in simulation and in real-time experiments for seven types of cluttered environments. The environments vary with size, shape, placement and arrangement of the obstacles. The results show that the simulated annealing generates a collision-free trajectory intelligently without trapping in local minima in these cluttered environments while the PID control tracks the reference trajectory with a maximum absolute error of 0.2 mm. Hence, the proposed method enhances the usability of mobile robots in environments cluttered with static objects.

This paper presents design of an anthropomorphic prosthetic hand which is actuated through single transducer. To provide more accurate and detailed model for the digital simulation of prosthesis, the Bond Graph approach is used. The prosthesis has five phalanges. Because of different parameters (length, width and weight), each phalange acts as an individual module to be designed but ultimately controlled by single source. The phalanges are actuated using flexible strings which are running over the pulleys and fixed with the transducer shaft. The damping of the pulleys and gears, stiffness of the strings, and inertias of each phalange are modeled precisely to provide better performance under different circumstances. Bond graph technique proved to be the more detailed and analytical way of designing the prosthetics to make them more controllable and efficient in the applications where highly précised functionality is desired. The transducer commissioned for the actuation of the prosthetic has also been modeled using Bond graph technique so that its functionality could be analyzed more efficiently. Considering backlash of the reducer part of transducer as an uncertainty to the prosthesis dynamics, a robust controller is designed so that the position of the phalanges could be controlled precisely and the prosthetic hand could mimic the movements more efficiently.