Anti-Roll Characteristics of Marine Gyrostabilizer Based on Adaptive Control and Hydrodynamic Simulation

The gyrostabilizer produces the anti-roll effect through the precession output moment generated by a high-speed rotating flywheel. As a floating-base multi-body system composed of ship and gyrostabilizer, the recent research that has only focused on the control strategies or multi-body dynamics is obviously not comprehensive. This study presents an adaptive controller based on the variable gain control strategy for a marine gyrostabilizer installed on a port salvage tug. The variable gain control strategy controlled the flywheel precession output moment of the gyrostabilizer and thereby of the precession process, to reduce the ship roll motion effectively. Furthermore, a full-system hydrodynamic model of a gyrostabilizer-ship-wave based on three-dimensional numerical wave flume technology was innovatively established to evaluate its anti-roll performance under irregular wave conditions. The simulation results show that, for the sea state considered, the increase of spin rate of gyrostabilizer flywheel improved the anti-roll effect significantly. The average anti-roll rate of the gyrostabilizer decreased with the increase of significant wave height, wave period and wave encounter angle.

Generic Upscaling Methodology of a Floating Offshore Wind Turbine

This study presents a generic method to upscale a semi-submersible substructure and tower-nacelle-blade for a floating offshore wind turbine from 5 MW to 15 MW and beyond. The effects of upscaling the column radius and/or distance of the floating base are investigated, and a comparison is made with a 15 MW reference design. It is found that scaling column radius increases the mass of the platform and the heave natural period, while scaling column distance raises the center of gravity and metacentric height of the floating system and slightly decreases the heave natural period. The 15 MW reference design addresses these issues through design changes that increase the ballast mass to lower the center of gravity, and increase the added mass to raise the heave natural period. Finally, a method for estimating the scaling of platform parameters with different assumptions is proposed.

Reaction Forces and Flexion-Extension Moments Imposed On Functional Spinal Units with Constrained and Unconstrained in Vitro Testing Systems

A mechanical goal of in vitro testing systems is to minimize differences between applied and actual forces and moments experienced by spinal units. This study quantified the joint reaction forces and reaction flexion-extension moments during dynamic compression loading imposed throughout the physiological flexion-extension range-of-motion. Constrained (fixed base) and unconstrained (floating base) testing systems were compared. Sixteen porcine spinal units were assigned to both testing groups. Following conditioning tests, specimens were dynamically loaded for 1 cycle with a 1 Hz compression waveform to a peak load of 1 kN and 2 kN while positioned in five different postures (neutral, 100% and 300% of the flexion and extension neutral zone), totalling ten trials per FSU. A six degree-of-freedom force and torque sensor was used to measure peak reaction forces and moments for each trial. Shear reaction forces were significantly greater (25.5 N - 85.7 N) when the testing system was constrained compared to unconstrained (p < 0.029). The reaction moment was influenced by posture (p = 0.037), particularly in C5C6 spinal units. In 300% extension (C5C6), the reaction moment was, on average, 9.9 Nm greater than the applied moment in both testing systems and differed from all other postures (p < 0.001). The reaction moment error was, on average, 0.45 Nm at all other postures. In conclusion, these findings demonstrate that comparable reaction moments can be achieved with unconstrained systems, but without inducing appreciable shear reaction forces.

Design Human-Robot Collaborative Lifting Task Using Optimization

In this paper, an optimization-based dynamic modeling method is used for human-robot lifting motion prediction. The three-dimensional (3D) human arm model has 13 degrees of freedom (DOFs) and the 3D robotic arm (Sawyer robotic arm) has 10 DOFs. The human arm and robotic arm are built in Denavit-Hartenberg (DH) representation. In addition, the 3D box is modeled as a floating-base rigid body with 6 global DOFs. The interactions between human arm and box, and robot and box are modeled as a set of grasping forces which are treated as unknowns (design variables) in the optimization formulation. The inverse dynamic optimization is used to simulate the lifting motion where the summation of joint torque squares of human arm is minimized subjected to physical and task constraints. The design variables are control points of cubic B-splines of joint angle profiles of the human arm, robotic arm, and box, and the box grasping forces at each time point. A numerical example is simulated for huma-robot lifting with a 10 Kg box. The human and robotic arms’ joint angle, joint torque, and grasping force profiles are reported. These optimal outputs can be used as references to control the human-robot collaborative lifting task.

Versatile Locomotion Planning and Control for Humanoid Robots

We propose a locomotion framework for bipedal robots consisting of a new motion planning method, dubbed trajectory optimization for walking robots plus (TOWR+), and a new whole-body control method, dubbed implicit hierarchical whole-body controller (IHWBC). For versatility, we consider the use of a composite rigid body (CRB) model to optimize the robot’s walking behavior. The proposed CRB model considers the floating base dynamics while accounting for the effects of the heavy distal mass of humanoids using a pre-trained centroidal inertia network. TOWR+ leverages the phase-based parameterization of its precursor, TOWR, and optimizes for base and end-effectors motions, feet contact wrenches, as well as contact timing and locations without the need to solve a complementary problem or integer program. The use of IHWBC enforces unilateral contact constraints (i.e., non-slip and non-penetration constraints) and a task hierarchy through the cost function, relaxing contact constraints and providing an implicit hierarchy between tasks. This controller provides additional flexibility and smooth task and contact transitions as applied to our 10 degree-of-freedom, line-feet biped robot DRACO. In addition, we introduce a new open-source and light-weight software architecture, dubbed planning and control (PnC), that implements and combines TOWR+ and IHWBC. PnC provides modularity, versatility, and scalability so that the provided modules can be interchanged with other motion planners and whole-body controllers and tested in an end-to-end manner. In the experimental section, we first analyze the performance of TOWR+ using various bipeds. We then demonstrate balancing behaviors on the DRACO hardware using the proposed IHWBC method. Finally, we integrate TOWR+ and IHWBC and demonstrate step-and-stop behaviors on the DRACO hardware.

ON THE QUESTION OF LABOR SAFETY IN THE CONSTRUCTION OF MODERN HOUSES ON WATER

Problem statement. Architecture near rivers and other bodies of water reflects the artistic and stylistic features of cities. Modern surface architecture has been devided in two large groups and includes a large number of typological units. The first group is large hydraulic structures (canals, dams, locks, bridges). The second group are the buildings and structures with social and housing functions. Despite the different purposes, the objects of this group have a common structural scheme, which is represented by two components: a floating base and a superstructure [1]. Today buildings on water are very popular all over the world. The main reasons for this are overpopulation of the territory, high taxes on land and others. Such buildings are popular in Germany, the Netherlands, Great Britain, the United States of America, Venice, France, India, the Czech Republic and others. In Ukraine, the construction of buildings on water is promising and may become popular for the following reasons: rather short term of order implementation; long service life (up to 50 years); a large number of mooring places; closeness to nature; privacy of rest and others [2]. Due to the fact that the process of erecting buildings on water is quite complicated and covers several branches of production at once, consideration of the issue of ensuring safe working conditions is relevant and necessary. Also, this issue has its own specifics associated with the selection of workers and ensuring safety when working on water. Purpose of the article is an analysis of the state of safety and organization of safe working conditions during the erection of modern buildings on the water. Conclusions. 1. Fatal injury rates in the construction industry have consistently exceeded those in the mechanical engineering industry in recent years. At the same time, the indicators of fatal injuries in recent years have a tendency to increase and constancy in both industries. 2. The percentage of the main causes of occupational accidents is almost constant. The influence of the main hazardous production factors associated with the construction of buildings on water, for the most part, leads to the occurrence of accidents. 3. Drawing up recommendations for the safe implementation of consistently all stages of the construction of buildings on water is an important issue of our time, since such construction has great development prospects in our country.

The influence of external factors on the technological system of high-precision machine tool in the conditions of floating workshops

В статье приведены результаты анализа и теоретических исследований динамической системы технологического оборудования плавучей мастерской. В системе металлорежущего станка при работе происходят сложные вибрационные воздействия, как стационарные, так и нестационарные, в результате колебательных процессов. Для обеспечения работоспособности оборудования необходимо выполнить компенсацию колебаний, создаваемых технологическим оборудованием вследствие смещений плавучей мастерской в результате внешних возмущений. Наиболее точным по существующим представлениям является описание морского волнения суперпозицией волновых систем. Для описания энергетического спектра трехмерного волнения обычно используется формула Артура. Для определения динамических характеристик несущей системы, а именно, амплитудно-частотных и амплитудно-фазовых частотных характеристик, необходимо наличие динамических моделей технологических систем станка, которые необходимо построить на основе конкретной расчетной схемы. Предложена одна из схем, позволяющая проиллюстрировать динамику перемещений центров круга, заготовки и изменения фактической глубины резания в процессе круглого наружного шлифования. Повышение качества обработки деталей непосредственно связано с необходимостью ослабления вынужденных колебаний станка, передаваемых через поверхность палубы от внешних источников. Уровень вынужденных колебаний станка снижается при установке его на виброизолирующие устройства. Традиционные виброизолирующие опоры не могут быть использованы на плавучих мастерских по причине невозможности их функционирования в условиях качки плавучего основания и горизонтальных смещений под ее воздействием. Получение расширенной модели стохастического описания процесса съема материала при взаимодействии инструмента, заготовки и источника внешних возмущений способствует определению основных технологических показателей процесса обработки в условиях плавучих мастерских. The article presents the results of analysis and theoretical studies of the dynamic system of technological equipment of a floating workshop. In the system of a metal cutting machine during operation, complex vibrational influences occur, both stationary and non-stationary, as a result of oscillatory processes. To ensure the work of the equipment, it is necessary to compensate for fluctuations created by technological equipment due to displacements of the floating workshop as a result of external disturbances. The most accurate according to existing models is the description of sea waves by a superposition of wave systems. The Arthur formula is usually used to describe the energy spectrum of three-dimensional waves. To determine the dynamic characteristics of the carrier system, namely, the amplitude-frequency and amplitude-phase frequency characteristics, it is necessary to have dynamic models of technological systems of the machine, which must be built on the basis of a specific design scheme. One of the schemes is proposed, which allows one to illustrate the dynamics of the displacements of the centers of the circle, the workpiece, and the change in the actual depth of cutting in the process of circular external grinding. Improving the quality of processing parts is directly related to the need to weaken the forced vibrations of the machine transmitted through the surface of the deck from external sources. The level of forced vibrations of the machine decreases when it is installed on vibration-isolating devices. Traditional vibration-isolating supports cannot be used in floating workshops because of the impossibility of their functioning under the rolling pitch of the floating base and horizontal displacements under its influence. The obtained extended model of the stochastic description of the material removal process during the interaction of the tool, the workpiece and the source of external disturbances helps to determine the main technological parameters of the processing in the conditions of floating workshops.