Dinh Van Phong

An algorithm for deriving equations of motion of constrained mechanical system

The article deals with the form of equations of motion of mechanical system with constraints. For holozoic systems the number of differential equation is equal to the degrees of freedom, without regard to the number of chosen coordinates. The possibilities of computer processing (symbolical and numerical) are shown. Two simple examples demonstrate the described technique.

Experiments and numerical calculation to determine aerodynamic characteristics of flows around 3D wings

The report presents method and results of experiments in wind tunnel to determine aerodynamic characteristics of 3D wings by measuring pressure distribution on the wing surfaces. Simultaneously, a numerical method by using sources and doublets distributed on panel elements of wing surface also is carried out to calculate flows around 3D wings. This computational method allows solving inviscid problems for wings with thickness profile. The experimental and numerical results are compared to each other to verify the built program that permits to extend the range of applications with the variation of wing profiles, wing planforms, and incidence angles.

Principle of compatibility and non-generalised coordinates

The contribution is devoted to using so-called non-generalised coordinates for deriving the system of equations of motion. Differently from common techniques for constrained mechanical systems the principle of compatibility is chosen as the tool. This takes the advantage in the possibility for extension to systems with nonideal constraints, however, the special treatment is needed. In the article the author derived the theoretical basis as well as numerical algorithms concerning the combination of nongeneralised coordinates with the principle of compatibility. Some comparisons of the technique under consideration and usual technique using Lagrange multipliers are discussed. Some examples are shown for illustration. The case of contact of moving disc on the surface is given in detail

Determining reaction forces in planar mechanisms

In the paper, it is introduced a method to det ermine joint reaction forces, constraint forces and internal forces at the cross section of linkages. Based on the principle of compatibility and the ideality of constraints, the methodology is presented to analyze and determine reaction forces in planar mechanisms.

On Numerical Methods for Constrained Mechanical Systems

The dynamics of complex mechanical system is becoming increasingly important. Detailed descriptions are needed for physical processes occurring in machines, robots and other multibody systems, see [11], [14], [15]. Accuracy must be maintained as computational volume increases. Many mechanical systems are controlled by programs. The controlling quantities are reaction forces corresponding to constraints. Numerical errors in computations may lead to violation of these constraints; the level of violation depends on the complexity of the system and the nature of the constraints.

Solution of discrete oscillating system on personal computer

The article is devoted an algorithm for deriving mass matrix , stiffness matrix and damping matrix for oscillating discrete system. The algorithm is common setting equation of motion. This technique enables solving different problems of oscillating system, especially a problem of parameters optimization, by numerical methods. Comparison of different methods realized on personal computers was done.