No abstract

Dynamic models of several mechanical systems are used for the analysis of specific robotic mechanisms. Two different situations may be encountered. The first situation is when the robot’s command system, based on Lagrange’s differential equations, calculates the corrections of command parameters of the actuators at short intervals of time. This model includes both the characteristics of the mechanical structure and those of the actuators and transmission. A second situation is encountered during the motion planning, when a model is needed to calculate both engine parameters and inertial forces which are applied to the mechanical system during the operation. Consequently, in this study, a d’Alembert-Newton model is used for extended dynamic analysis of a new constructive solution of a parallel mechanism. The dynamic model of a HEXA parallel mechanism has been developed using the abovementioned theory, and further, the dynamic inverse solution has been obtained. The numerical results were obtained using an original algorithm. This dynamic model allows the estimation of power absorbed by each actuator and also the loading control for each kinematic chain of the HEXA parallel mechanism. Knowing the variation of driving torque, for all the six actuators of the mechanism, allows the user to choose an optimal trajectory, such as avoiding excessive loading of a single kinematic chain.

This paper presents a method for determining the singular configurations of a 6RSS parallel mechanism based on its kinematic model. The parallel mechanism consists of a fixed plate and a mobile platform connected through six independent kinematic chains. Each of the six kinematic chains has an actuating rotational joint and two spherical joints. The kinematic analysis is based on the kinematic screw method. The resultant motion can thus be represented by composing the kinematic screws of the component motions. Starting from the two Jacobian matrices of the kinematic model, the two types of singularities encountered in parallel mechanisms are identified. Singular configurations are determined by an algorithm which is further used to produce three-dimensional representations of the two matrices determinants. Also, with the same program, it is possible to accurately establish the existence or inexistence of a mechanism for a given position and orientation.

The study of the kinematic performances of a parallel mechanisms an important aspect in terms of analysis and design. This paper presents a study on the kinematic manipulability and kinematic efficiency of a 6RSS parallel mechanism. The parallel mechanism consists of a fixed plate and a mobile platform connected by six independent kinematic chains. Each of the six kinematic chains has an actuated rotational joint and two spherical joints. The motion equations for the six kinematic chains of the parallel mechanism are defined when the characteristic point P moves on the spatial curve with constant speed. Based on the global Jacobian matrix determinant and the angular speeds of actuated arms was graphically represented the variation of the two kinematic indices. Kinematic indices allow for assessing the quality of the mechanism motion; they also help us avoid those critical configurations encountered in the case of parallel mechanisms.

When speaking about other energy storage devices, flywheels can be viable alternatives due to the low degradation process during the entire operating life, and its numerous energy discharge rates. In this paper, the problem of the flywheel shape, present in the KERS system, is approached analytically. The analysis was performed on three series of rotors and the results were validated using a CAD program. The linear relationship between the mass of the flywheel mass and its rotation axis was emphasized by Pappus-Guldin theorem. Based on the results it was shown that the value of kinetic energy is higher when the mass of the flywheel is concentrated closer to the axis of rotation.