Study of forces in a 2T9R robot mechanism

The paper presents in detail a method of calculating the forces acting on a 2T9R type robot. In order to determine the reactions (forces in the kinematic couples), one must first determine the inertial forces in the mechanism to which one or more useful loads of the robot can be added. The torsor of the inertia forces is calculated with the help of the masses of the machine elements and the accelerations from the centers of mass of the mechanism elements, so the positions, velocities, and accelerations acting on it will be determined, i.e. its complete kinematics. The calculation method applied by a MathCad program intelligently uses data entry through the IFLOG logic function so that the calculations can be automated. So the effective automation of the calculation program is done exclusively through the IFLOG functions originally used in the paper.

Modern Walking Robots: A Brief Overview

In this review, we would like to present some of the most interesting modern designs of walking robots: bipedal, quadropedal, hexopedal, and octopods. Their advantages and disadvantages are highlighted. It has been determined that structures with eight or more limbs are ineffective due to high level of electricity consumption. The use of more than six number of legs does not give noticeable advantages in profile cross-country ability or maneuverability, however, it allows to reduce the forces and moments of inertia forces due to decrease in mode coefficient (ratio of time spent by propulsor in support to time of entire step), and, consequently, smoother leg movements in swing phase.

Design and Structural Analyses of a Reciprocating S1223 High-Lift Wing for an RA-Driven VTOL UAV

In the design stage of an aircraft, structural analyses are commonly employed to test the integrity of the aircraft components to demonstrate the capability of the structural elements to withstand what they are designed for, as well as predict potential failure of the components. This research focused on the structural design and analysis of a high-lift, low Reynolds number airfoil profile, the Selig S1223, under reciprocating inertial force loading, to determine the feasibility of its use in a new reciprocating airfoil (RA) driven VTOL UAV. The material selected for the wing structures including ribs, spars, and skin, was high-strength carbon fiber. The wing was designed in SolidWorks, while finite element analysis was performed with ANSYS mechanical in conjunction with the inertia forces due to the reciprocating motion of the wing and the lift and drag forces that were derived from the aerodynamic wing analyses. The structural stress and strain determined under the loading conditions were satisfactory and the designed wing could sustain the high reciprocating inertia forces in the RA-driven VTOL UAV module. The results of this study indicate that the Selig S1223 airfoil profile, due to its superior performance at low Reynolds numbers, high-lift, and reduced noise characteristics at low angles of attack, combined with the use of the high strength carbon fiber, proves to be an excellent choice for this RA-driven aircraft application.

A Novel Coaxial Balance Mechanism for Reciprocating Piston Engines

Vibration is an important issue faced by reciprocating piston engines, and is caused by reciprocating inertia forces of the piston set. To reduce the vibration without changing the main structure and size of the original engine, we proposed a novel coaxial balance mechanism design based on a compact unit body. By introducing a second-order balance mass, this mechanism can significantly increase the efficiency of vibration reduction. The proposed mechanism can effectively balance the first-order and second-order inertia forces with the potential of balancing high-order inertia forces. To accurately determine the second-order balance mass, a closed-form method was developed. Simulation results with a single-cylinder piston DK32 engine demonstrate the effectiveness and advantage of the proposed mechanism. At a crankshaft speed of 2350 r/min, compared with the first-order balance device, the average root mean square velocity of the test points on the engine’s cylinder was reduced by 97.31%, and the support reaction force was reduced by 96.54%.

Proportional control moment gyroscope for two-wheeled self-balancing robot

A two-wheeled self-balancing robot is considered for investigating the responses of a control moment gyroscope powered by a proportional controller to prevent the robot rollover against the constant inertia forces because of accelerations of the wheels of the robot. The amplitudes of the frequency equations related to the required angular momentum of flywheels with an optimum controller gain were also found. A simulation model of the robot using computer-aided engineering software (RecurDyn) is built to verify the equations of a Lagrangian model. The results of both obtained from the Lagrangian and that from RecurDyn simulations are analyzed comparatively, in which the proportional control loop reduces the required flywheel speeds Ω of gyros and keeps the robot in a very small amplitude of a stable sinusoidal motion in the upright position.

Investigation of the Influence of Inertia Forces on the Adhesion of the Coating to the Outer Surface of Bodies of Revolution during Thermal Spraying

The article presents the results of a study of the influence of inertial forces on the adhesion of the coating to the external surface of a body of revolution during thermal spraying. A mathematical apparatus is proposed for calculating the inertia forces, acting on a particle of coating, applied to the outer surface of the bodies of revolution. As a result, dependencies have been revealed that allow predicting the adhesion strength of the coating with the steel base during thermal spraying.

A numerical survey of nonlinear dynamical responses of discrete pantographic beams

Materials and structures based on pantographic cells exhibit interesting mechanical peculiarities. They have been studied prevalently in the static case, both in linear and nonlinear regime. When the dynamical behavior is considered, available literature is scarce probably for the intrinsic difficulties in the solution of this kind of problems. The aim of this work is to contribute to filling of this gap by addressing the dynamical response of pantographic beams. Starting from a simple spring mechanical model for pantographic beams, the nonlinear equilibrium problem is formulated directly for such a discrete system also considering inertia forces. Successively, the solution of the system of equilibrium equations is sought by means of a stepwise strategy based on a non-standard integration scheme. Here, only harmonic excitations are considered and, for large displacements, frequency-response curves are thoroughly discussed for some significant cases.

Mining machines elements packing and securing on platform container

The scientific purpose of this paper was to analyse the problem related to intermodal transportation of mining components packed in containers or other cargo transport units coupled with the problem of its proper securing. In this article, the issue of exposing the load to the effects of inertia forces which might cause unintentional movement is presented. The methods of securing the heavy load in cargo transport units are reviewed in the context of cargo immobilisation possibilities while reducing the load sensitivity to mechanical forces. The research part of this article presents the methods of packing and securing an atypical load, which is a part of a mining machine weighing 18t. This paper presents the results of calculations of inertia forces acting on the transported cargo, packed on a container platform. Based on the results, the cross fixing method was selected to secure the cargo and further decisions were made on the type and quantity of conveyor lashings necessary for the safe and correct carriage of the atypical load.

Application of the dynamic Lorentz model to modeling the motion of a rigid body

A qualitative research of the field of phase trajectories of the system of dynamic equations of an absolutely rigid body was carried out, moving around the selected pole under the influence of gyroscopic, dissipative forces and Coriolis inertia forces. The equations of body motion are reduced to a dynamical system generating a Lorentz attractor. Under parametric constraints imposed on the equations of a dynamical system, the structure of its phase trajectories is described depending on the values of the system parameters.

Effect of fluid inertia force on thermal elastohydrodynamic lubrication of elliptic contact

A non-Newtonian thermal elastohydrodynamic lubrication (TEHL) model for the elliptic contact is established, into which the inertia forces of the lubricant is incorporated. In doing so, the film pressure and film temperature are solved using the associated equations. Meanwhile, the elastic deformation is calculated with the discrete convolution and fast Fourier transform (DC-FFT) method. A film thickness experiment is conducted to validate the TEHL model considering the inertia forces. Further, effects of the inertia forces on the TEHL performances are studied at different operation conditions. The results show that when the inertia forces are considered, the central and minimum film thicknesses increase and film temperature near the inlet increases obviously. Moreover, the inertial solution of the central film thickness is closer to the experimental result compared with its inertialess value.