A manipulator size optimization method based on dexterous workspace volume

Background: Manipulators for robots are required to have high manipulability for adaptability in different tasks. However, general methods for designing manipulators with high manipulability are deficient. Here, aiming at improving the manipulability of the six degrees-of-freedom (DOF) manipulator, a method for optimizing structure size parameters based on the dexterous workspace volume is proposed. Methods: Firstly, the kinematic analysis of the manipulator is performed. Then, the manipulability of the single working point of the manipulator is judged based on reachability in different postures. The workspace of the manipulator is discretized to obtain the volume of the overall dexterous workspace. By taking the maximum volume of the dexterous workspace as the optimization goal, Genetic Algorithm (GA) is used to optimize the structure size parameters to achieve optimal manipulability. AUBO 6-DOF manipulator is defined and analyzed as an example. Results: The optimization results indicate that the dexterous workspace of the manipulator expands in volume and its manipulability is improved. The validity of the proposed optimization method is verified by comparing the distribution of dexterous workspace of the manipulator. Conclusions: This article proposes an optimization method for the structure size parameters of a 6-DOF manipulator, which can be implemented to improving the manipulability of the manipulator.

NAVAL ARCHITECTURAL CONSIDERATIONS IN THE DESIGN OF FLOATING DOCK

A brief introduction about floating docks, its advantages and types have been described. The naval architectural considerations which play a significant role in the design of floating dock have been explained. Typical ratios of L/B and L/D as a function of Dock’s lifting capacity have been presented. Empirical formulation for the same have also been indicated wherever applicable. Intact stability and its criterion as applicable for a floating dock have been described. Critical positions during evolution of docking operation and important considerations while performing stability calculations have been highlighted. Attention has also been drawn to the damage stability of floating dock. Aspects of longitudinal and transverse bending moment, which are the governing aspects in the scantling calculations have been described. Also typical methods for securing and mooring of floating dock, without compromising on flexibility for docking operations have been described. Methodology and consideration which has to be kept in mind while using design software (such as NAPA) have been indicated. Simple size optimization techniques which result in steel / ballast volume reduction have also been explained.

Analysis of a Preliminary Design Approach for Conformal Lattice Structures

An important issue when designing conformal lattice structures is the geometric modeling and prediction of mechanical properties. This paper presents suitable methods for obtaining optimized conformal lattice structures and validating them without the need for high computational power and time, enabling the designer to have quick feedback in the first design phases. A wireframe modeling method based on non-uniform rational basis spline (NURBS) free-form deformation (FFD) that allows conforming a regular lattice structure inside a design space is presented. Next, a previously proposed size optimization method is adopted for optimizing the cross-sections of lattice structures. Finally, two different commercial finite element software are involved for the validation of the results, based on Euler–Bernoulli and Timoshenko beam theories. The findings highlight the adaptability of the NURBS-FFD modeling approach and the reliability of the size optimization method, especially in stretching-dominated cell topologies and load conditions. At the same time, the limitation of the structural beam analysis when dealing with thick beams is noted. Moreover, the behavior of different kinds of lattices was investigated.