A Reconfiguration Algorithm for the Single-Driven Hexapod-Type Parallel Mechanism

This paper presents a hexapod-type reconfigurable parallel mechanism that operates from a single actuator. The mechanism design allows reproducing diverse output link trajectories without using additional actuators. The paper provides the kinematic analysis where the analytical relationships between the output link coordinates and actuated movement are determined. These relations are used next to develop an original and computationally effective algorithm for the reconfiguration procedure. The algorithm enables selecting mechanism parameters to realize a specific output link trajectory. Several examples demonstrate the implementation of the proposed techniques. CAD simulations on a mechanism virtual prototype verify the correctness of the suggested algorithm.

Development and Analysis of a Parallel Structure Mechanism with Slotted Arcuate Guides and a Constant Entry Point

The development and study of new mechanisms of a parallel structure ensuring the constancy of the point of instrument entry into the working area is an urgent task of surgery and scientific medicine. A structural synthesis of a parallel structure mechanism designed for robotic laparoscopic surgery has been performed. The proposed mechanism is equipped with arcuate guides with slots installed on the base perpendicular to each other. At the intersection of the slots, there is a bushing through which a straight shaft connected to the output link moves linearly. This arrangement provides a constant entry point, which allows the developed mechanism to be used in laparoscopic surgery and studies of plasma properties. For this mechanism, the inverse problem of positions has been solved, the working area has been determined, and a 3D model has been developed.

Structural Synthesis and Analysis of Mechanisms with an Output Link Performing Two Rotational and One Translational Movements

The article considers mechanisms based on a hinged flat parallelogram with an additional link, ensuring the ability to maintain the insertion point of the tool installed on the output link. A rotational kinematic pair coupled to the base allows the plane of rotation of the articulated parallelogram to change the angle of inclination. The proposed design should have a greater load capacity than the available analogues, since the rotational kinematic pair mating the articulated parallelogram with the base is made in the form of two semi-axes, and the output link is located between the intermediate links of this parallelogram. The equality of the rotation angles of the output link and the intermediate links of the articulated parallelogram is ensured by the presence of additional links or belt drives. Three-dimensional models of these mechanisms are presented, and their structural synthesis is carried out in various modifications. Depending on the modification, it becomes possible to apply such mechanisms not only in industry, including additive technologies, but also in the field of medicine during surgical operations and in the study of plasma properties.

Research of Kinematic Stepping Mechanism

In this paper, a kinematic analysis of Theo Jansen’s stepping mechanism has been carried out and an algorithm for finding the output link trajectory from the given dimensions of the stepping mechanism elements, implemented by Mathcad program, has been developed. It is possible to output characterising parameters of all intermediate links with any number of intermediate links of a step cycle of the mechanism. The dimensions of the mechanism elements have been selected so that they provide the optimal smooth trajectory of the stepping point, minimising the mechanism oscillations in the vertical plane. A comparison of the trajectories of the foot in this study with the classical trajectory of Theo Jansen and the trajectory from article [7] has been provided. A minimum swing of the oscillation of the centre of mechanism masses in the vertical plane has been selected as an optimality criterion, combined with the maximum smoothness of the trajectory, provided that maximization of the step height is not required.

Design and Analysis of Parallel Mechanism with Linear Drives Located on the Base at Specified Angles

The article considers a novel parallel mechanism with drives located on the base at different angles to its plane. This arrangement allows performing a relative movement between objects under water or in space (in aggressive environments). The new mechanism topology is compact for transportation and efficient for operation in aggressive environments. Structural synthesis has been performed; the number of degrees of freedom of the output link was calculated. A general approach to solving the inverse kinematics problem of positions is proposed and an example for a kinematic chain is shown. Denavit — Hartenberg matrices are used to solve the problem of positions. The position of the output link described by this matrix is used to represent the points of this link in the base coordinate system. The constraint equations are applied, which are the distances between the points of the base and the output link.

Structural and Kinematic Analysis of the Isomorphic Mechanism of a Parallel Structure for Translational Movements of the Output Link

The article considers the mechanism of a parallel structure with three degrees of freedom, having the property of isomorphism. The ratio between the movements in the drive and the movements of the output link is constant. This is due to the fact that all linear drivers are located parallel to the corresponding axes of the fixed coordinate system, and in each kinematic chain there are two rotational kinematic pairs, the which axes are parallel to the axes of the corresponding linear drivers. In addition, each kinematic chain has two dyads that provide linear motion of the linear driver rod. On the basis of the developed three-dimensional model, a structural analysis of the mechanism with determination of the number of degrees of freedom and solving the problem of its positions was carried out. The proposed mechanism can be applied in many areas of activity of industrial enterprises, including additive technologies due to the growth of automation, robotization and the development of artificial intelligence.

High-capacity stacking apparatus for thermoforming machine – Part I: Synthesis of intermittent mechanisms as stacker driving units

The paper presents the type and dimensional synthesis of intermittent mechanisms for use in a thermoforming machine high-capacity stacking apparatus. The aim of this paper is to realize the intermittent motion of the working part of the stacker – conveyor, with a completely mechanical system that should enable the adjustment of the operating parameters of the stacker at a constant motor speed. Mechanical control ensures high positioning accuracy of the product ejection panel, as well as high repeatability of the motion cycle of the conveyor, which is key. Based on the set requirements, the concept of a planar mechanism of simple structure was chosen, which enables oscillatory movement of the output link for continuous motion of the input link, in combination with a one-way clutch (OWC). Four types of intermittent mechanisms have been proposed. However, multiple configurations of the same mechanism type can achieve the same output link motion interval, which is why 3 configurations for each mechanism type are considered, with a total of 4 output link motion intervals, which is 12 potential solutions for only one mechanism type. Afterwards, dimensional synthesis was performed for each type of mechanism by using the optimization method. Based on the analysis of the results, all of the mechanism types are potentially usable. After additional analyses, the optimal solution was chosen.

MODELING OF MECHANICAL TRANSMISSION TAKING INTO ACCOUNT FREQUENCY OF TOOTH-ENGAGEMENT

At present time, in control systems, an electromechanical drive, which includes a reduction gear, is widely used. To ensure the quality of the output movement of the drive, it is not enough synthesize it according to the criteria of performance and accuracy. With increasing requirements for drives, the need arose for such an indicator of the quality of dynamics as smoothness [1], which is mainly influenced by the quality of the mechanical transmission production. The article provides an example of modeling a reduction gear taking into account multi-massage, the number of teeth, geometric errors of tooth-engagement, imbalance of the engine rotor. The spectrum of speed fluctuations of the output link is obtained, which characterizes the smoothness of the reduction gear operation. A conclusion is made about the prospect of using a model approach to diagnose the smooth operation of reduction gears.

DETERMINATION OF SCREWS-GRADIENTS AND MUTUAL SCREWS THAT BRING L-COORDINATE MECHANISMS OF A PARALLEL STRUCTURE OUT OF SPECIAL POSITIONS AT VARIOUS POINTS OF FASTENING OF DRIVES

The article discusses the special configurations (singularities) of spatial l-coordinate mechanisms. At the beginning, the position is shown where all the l-coordinate axes intersect the OX axis. In this case, there is a twist, reciprocal to all unit screws of the axes of prismatic kinematic pairs, this reciprocal twist coincides with the OX axis. In addition, a twist-gradient was found, which brings the mechanism out of a special position (singularity). In this case, the centers of the spherical hinges of the base are located on the plane z = –1. The centers of the spherical hinges of the output link are located at different distances from the XOY plane. Then, all the centers of the spherical hinges of the output link are located on the plane z = 1. The twist-gradient changes in this case. When changing the positions of the planes on which the centers of the spherical hinges of the bases and the output link are located, the twist-gradient no longer changes.