The calculation of forces in the kinematic pairs of mechanisms by inverse dynamics is usually performed without friction considerations -- In practice, when examination of articulated mechanisms takes into account friction, the solution of the inverse dynamics results in a complex procedure -- If a modular approach for the inverse dynamics is used, then exact solutions are available, but not necessarily are practical -- For example, the analytical solution for a second-class first-type Assur group is a 16th degree equation -- Previous researches proposed an approximated but practical (graphical) method to calculate the forces on the kinematic pairs taking into account the friction forces -- In this article, an analytical interpretation of the Artobolevski approximated method is developed for the second-class Assur group with three rotational pairs -- The final results for the reactions calculated with the implemented method present a good approximation with respect to the graphical solution -- Future work should consider friction forces not only in second-class groups with rotational joints, but also in second-class groups with prismatic joints and high-class Assur group

La precisión y exactitud, que son requerimientos habituales en los procesos de manufactura, están definidas por el contexto de fabricación, tanto desde las especificaciones del proceso como desde el propio sistema de manufactura. La calibración cinemática de sistemas electromecánicos contribuye a lograr los requerimientosdefabricación. Este trabajo presenta un método de calibración cinemática para una ruteadora CNC que opera en un contexto de tolerancias dimensionales lineales ISO 2768-c. El método de calibración está basado en la estimación de los parámetros de un modelo cinemático con una representación de variaciones dimensionales (lineales y angulares) de la estructura. La estimación de los parámetros es realizada a partir de errores de maquinado medidos mediante fotogrametría monocular de un patrón geométrico que registra un mecanizado intencional. La calibración se implementó en una máquina CNC mediante ajuste del código G, alcanzando así los requerimientos de fabricación exigidos por el contexto propuesto

Robotic gait retraining systems typically function by employing mechanisms that move a patient’s lower limbs in a controlled manner. In this paper, an end-effector gait retraining system was designed, utilizing a 2-PRR mechanism (PRR refers to the structure of each robot’s limb, consisting of an active prismatic pair (P) and two passive rotational pairs (RR) pairs). The mechanism, which corresponds to a parallel robot, was synthesized through visual design tools (design atlases) to evaluate performance indices, such as the workspace size, local and global conditioning, and mechanism stiffness. Quasi-static force analyses were conducted to calculate worst-case scenario operational loads. These loads were then used to obtain a valid cross-section geometry that would withstand static stress, buckling failure, and fatigue failure.

Collisions are a key topic in physics and engineering education. An experiment with multiple body one-dimensional collisions is presented, aiming to measure relevant physical quantities by tracking the motion of the system of particles during the collision. Relations between different physical quantities can be explored in the experiment, such as linear momentum, impulse, and energy. Equations are presented for modeling velocity changes during the collisions under the elastic and inelastic conditions and extensions to many body colliders can be easily implemented. Predictions for the velocities and other collision quantities were verified for a set of mass parameters by photogrammetry and digital video analysis.

In civil construction Abstract— This paper presents a dimensional synthesis for a 2-PRR planar parallel robot with a structural plane of symmetry. This robot can achieve the translation of the moving platform without changing the orientation, being useful for applications that require controlled positions with high rigidity. Because the performance of parallel robots is highly sensitive to their geometric parameters, many methodologies to state the dimensional synthesis has been developed. We used the method of Parameter - Finiteness Normalization Method (PFNM) to state the dimensional synthesis using Global Condition Index (GCI) and workspace ( ) design atlases. For the two, GCI and , designed atlases, it is not possible to maximize one of the indexes without diminishing the other one, which represents a design compromise. Also, we remark singular configurations that are coming from specific geometry or limit positions. The complete dimensional synthesis is also presented.