Modeling, Design, and Implementation of an Underactuated Gripper with Capability of Grasping Thin Objects

Underactuated robotic grippers have the advantage of lower cost, simpler control, and higher safety over the fully actuated grippers. In this study, an underactuated robotic finger is presented. The design issues that should be considered for stable grasping are discussed in detail. This robotic finger is applied to design a two-fingered underactuated gripper. Firstly, a new three-DOF linkage-driven robotic finger that combines a five-bar mechanism and a double parallelogram is presented. This special architecture allows us to put all of the required actuators into the palm. By adding a torsion spring and a mechanical stopper at a passive joint, this underactuated finger mechanism can be used to perform parallel grasping, shape-adaptive grasping, and environmental contact-based grasp. Secondly, the dynamic model of this robotic finger is developed to investigate how to select an appropriate torsion spring. The dynamic simulation is performed with a multi-body dynamic simulator to verify our proposed approach. Moreover, static grasp models of both two-point and three-point contact grasps are investigated. Finally, different types of grasping modes are verified experimentally with a two-fingered underactuated robotic gripper.

Dual Mass Flywheel Parameter Identification

Reducing emissions brings changes in the design of internal combustion engines and thus new challenges for dual-mass flywheels (DMF) in terms of Noise Vibration and Harshness (NVH). The first part of the article describes a simple model of a centrifugal pendulum. Consequently, a more complicated DMF dynamic model involves friction between the spring components. The second part of the article deal with the multibody model of DMF using a CAD model. The dynamic model consists of a torsion spring and two bodies. The model is compared with the experimental method, which is also described in the paper.

IMPROVING THE DESIGN OF THE SPRING SUSPENSION OF TRAILED VEHICLES

This article presents materials related to the development of a promising design of adaptive tor-sion bar suspension for trailed special and cargo vehicles, both trailers and semi-trailers, designed for the transportation of bulk and general cargo. A number of technical solutions, created at the level of inventions, are proposed, which make it possible to simplify the existing types of spring suspensions, reduce their metal consumption, improve the smoothness of trailed vehicles (TV) and increase their operational reliability due to the operation of suspensions in automatic mode when they overcome micro and macro unevenness of the roadway. Analytical studies were carried out with the development of a design scheme and a methodology for calculating the design of an adaptive torsion spring for static and dynamic strength.

DYNAMIC LOAD REDUCTION DEVICE IN MACHINE DRIVE WITH SPRING AND SELECTION OF ITS PARAMETERS

The peculiarity of the technological equipment of light industry is the significant dynamic loads that occur during unstable operating modes and is one of the main reasons for reducing the reliability and durability of its operation. The problem of increasing the reliability and durability of their work by reducing the dynamic loads is relevant, because the known means of reducing the dynamic loads in the drive of machines can not always be used in light industry machines. Therefore, when designing light industry equipment, first of all, attention should be paid to reducing the dynamic loads in the drive and preventing accidents. The paper considers the feasibility of using a device with a torsion spring to reduce the dynamic loads in the drive of process equipment, check its performance and develop a method for selecting rational parameters. In the course of work modern methods of researches of mechanical systems are used for the purpose of an estimation of expediency of use of the device with a torsion spring for reduction of starting dynamic loadings in the drive of machine. On the basis of the analysis of features of work of the technological equipment of light industry the expediency of use in the drive of cars of the gear safety coupling with a torsion spring is established. A new design of the device is proposed to reduce the dynamic loads that occur during machine start-up. Unlike the known devices, the proposed device is made in the form of a toothed safety clutch with a torsion spring, which simplifies its design and increases efficiency. The use of a cylindrical torsion spring as an elastic element, which connects the half-clutch to the flange on which the satellite gears are mounted, prevents overloading of the drive and the choice of rational rigidity of the device depending on the change of operation, which increases its durability and expands performance. The method of checking the efficiency of the device for reducing dynamic loads and selecting its rational parameters is presented. The scientific novelty is the development of scientific bases and engineering methods of designing devices to reduce dynamic loads in the drive of technological equipment. The practical significance lies in the development of a new design of the device to reduce the dynamic loads in the drive of machines and the engineering method of choosing its rational parameters.

Push recovery control for the underactuated lower extremity exoskeleton based on improved capture point concept

Purpose The purpose of this paper is to use a simple method to enhance the ability of lower limb exoskeletons to restore balance under large interference conditions and to solve the problem that biped robot stability criterion cannot be fully applied to the underactuated lower limb exoskeletons. Design/methodology/approach The method used in this paper is to construct an underactuated lower extremity exoskeleton ankle joint with a torsion spring. Based on the constructed exoskeleton, the linear inverted torsion spring pendulum model is proposed, and the traditional capture point (CP) concept is optimized. Findings The underactuated exoskeleton ankle joint with torsion springs, combined with the improved CP concept, can effectively reduce the forward stepping distance under the same interference condition, which is equivalent to enhancing the balance ability of the lower extremity exoskeleton. Originality/value The contribution of this paper is to enhance the balance ability of the exoskeleton of the lower limbs under large interference conditions. The torsion spring is used as the exoskeleton ankle joint, and the traditional CP concept is optimized according to the constructed exoskeleton.

Experimental Results of Local Shear Stresses and Friction Torque in an Open Rotor-Stator Disc System

This contribution presents experimental investigations of friction torque in an open rotor-stator disc system by using two different measuring procedures. The first procedure based on a thermo electrical wall shear stress sensor. The sensor is investigated in two different substrates and different measuring parameters. A thermal model consisting of the supplied heating power, the thermal resistance toward the fluid, and into the substrate as well as the over temperature is used to achieve the heat transfer coefficient on the sensor surface. This heat transfer coefficient is attributed by a functional relationship to the wall shear stress. This relationship is firstly calibrated in a rectangular channel and subsequently validated at a fully turbulent flat plat flow. The second measuring procedure based on the tangential displacement of the stator disc due the friction torque. The disc is attached at a torsion spring. The friction torque is achieved by the torsion spring constant and the tangential displacement of the stator disc. Both measuring procedures are compared and agree well with each other. The used test rig has the possibility of reaching rotational Reynolds numbers representative for instance of a modern gas turbine. The investigations were carried out by a 0.5 m diameter rotor disc rotating up to 8500 rpm with a gap ratio between 0.008 and 0.04. The friction torque is measured on the stator disc and can be converted into moment coefficient. Moment coefficient on stator as well as measured pressure distributions are presented.

Effectiveness of bilateral single-hinged knee bracing in osteoarthritis: A finite element study

Effectiveness of knee braces remains to be identified. Therefore, the purpose of this study was to investigate the effectiveness of bilateral single-hinged knee bracing in knee osteoarthritis (OA) using finite element (FE) method. A three-dimensional FE model consisted of main model (knee-brace structure) and submodel (strap-muscle system) was developed. The submodel was used to convert the elastic strap-muscle interaction into an equivalent stiffness value required by the main model. Adding 100 N · mm/rad torsion spring to the brace with 5 kPa strap pressure lowered maximum von Mises stress in the knee OA components at a flexion angle greater than or equal to 90°. Separately, employing 10% brace pre-tension to the brace with 5 kPa strap pressure started to reduce stresses at a flexion angle of 70°. The configuration involving a combination of 10% brace pre-tension and 300 N · mm/rad torsion spring with 30 kPa strap tightness produced stress reduction over the entire range from 0° to 100° flexion angle. The basic bilateral single-hinged knee brace has shown to reduce stresses in the knee OA at high flexion angles only. Compared to the torsion spring, the brace pre-tension has shown to provide more significant benefits (i.e. stress reduction at lower flexion angles). The most sophisticated effects were achieved when the torsion spring was used in combination with the brace pre-tension. These two features can be potentially used for the development of an active knee brace if they can be modulated at different flexion angles or during the gait cycle.

BACKLASH-FREE POWER DRIVE OF MACHINES

Thebacklash-freepower drive of the machines ensures that the working shaft does not move freely when changing the direction of rotation. As a backlash-freegapless power drive, a single-stage planetary gearbox is proposed, containing two Central wheels, a carrier, and satellites, which are blocks of two gears, each of which is mounted on the carrierʼs axis by means of a rolling bearing and a freerunning Cam clutch. At the same time, the couplings are placed so as to ensure free rotation of the wheels in different directions. The gears are connected to each other by a pre-twisted cylindrical torsion spring. The proposed design will ensure reliable operation of the drive when the specified requirements are met.