Analysis of Conceptual Solutions of Universal Helical Geared Reducers

Geared reducers are mechanisms designed to reduce the number of revolutions using geared elements and nowadays they present one of the most commonly used types of mechanical transmissions in mechanical engineering. Due to the different shapes of geared elements, there are different types of geared transmissions: helical, bevel, worm, special and combined transmissions.  This paper analyses only helical geared transmissions, since there is a great extent of whole this matter. Helical transmissions are analysed only with external helical gearing, since internal geared pairs represent a special and very large group of gears. Within the external helical geared transmissions, only torque transmissions are analysed, while the transmissions of motion are not analysed and they represent another large group of transmissions. Only universal gear reducers with axial, or almost-axial, parallel shafts are considered (two-stage and three-stage transmissions). Although, single-stage gear reducer produced with parallel shafts are not considered by the paper in order to reduce the area of researching. Gear reducers are most commonly delivered to customer with electric motor, known as motor geared reducer, and they are studied here extensively. Gear reducer can be also delivered without motor, only with input shaft. The basic aim of this paper is to present all characteristics and specificities of motor geared reducer in one place

INFLUENCE OF THE TEETH NUMBER ON THE GEAR MODULE VALUE AND LOAD CAPACITY OF GEAR PAIR IN UNIVERSAL HELICAL GEAR DRIVES

The basic parameters of the universal gear drives, except the axis height, are not defined by the standard, so the manufacturers of universal gear reducers can define them in their way. Most of the manufacturers followed the parameter values of universal gear reducers of leading world producers in order to ensure their interchangeability and the better positioning of their gear units at the market. This paper deals with the analysis of the influence of the gear pair teeth number on the size of the module, as well as on the load carrying capacity of single-stage universal gear units. For defined gear ratio values, different combinations of teeth number of pinion and driven gear were selected. Further, it was made calculation of the basic geometric dimensions of the gear pair, as well as the load capacity

Anthropomorphic Robotic Eyes: Structural Design and Non-Verbal Communication Effectiveness

This paper shows the structure of a mechanical system with 9 DOFs for driving robot eyes, as well as the system’s ability to produce facial expressions. It consists of three subsystems which enable the motion of the eyeballs, eyelids, and eyebrows independently to the rest of the face. Due to its structure, the mechanical system of the eyeballs is able to reproduce all of the motions human eyes are capable of, which is an important condition for the realization of binocular function of the artificial robot eyes, as well as stereovision. From a kinematic standpoint, the mechanical systems of the eyeballs, eyelids, and eyebrows are highly capable of generating the movements of the human eye. The structure of a control system is proposed with the goal of realizing the desired motion of the output links of the mechanical systems. The success of the mechanical system is also rated on how well it enables the robot to generate non-verbal emotional content, which is why an experiment was conducted. Due to this, the face of the human-like robot MARKO was used, covered with a face mask to aid in focusing the participants on the eye region. The participants evaluated the efficiency of the robot’s non-verbal communication, with certain emotions achieving a high rate of recognition

Analysis of Possible Concept Solutions of Chain Drives

Possible concept solutions of chain drives are analysed in this paper in order to point out the benefits of chain drive application and, in particular, the possibility of application of multi-level chain drive. The paper also analyses the possibility of replacing the gear drives with chain drives, which, in the case of short-term drive and using the same direction of rotation, enables a slightly simpler drive solution. The paper doesn’t consider difference between the roller and gear chains application because these two types of chains can be used very successfully. Also, the possibility of using timing belt drive is not considered, but it can be also used very successfully in this type of drive, but only as a transmission of motion

Adaptive continuously variable transmission used for maintaining stationary regime of driving machine

Continuously variable transmissions (CVTs) contained in many complex systems of modern techniques can be designed as purely mechanical systems that can, thanks to their structure, do self adjustments, meaning they can change their own characteristics in order to adapt to the external parameters variations. In this way adaptive CVT can be used for automatic regulation of a system. A general approach to the dynamical description of adaptive CVT behavior as a nonholonomic, completely mechanical system is developed. For the dynamical description of the mechanical nonholonomic system, Appell`s differential equations are used. By numerically solving differential equations of motion, answers about the working stability as well as the dynamical and kinematic behavior of the observed CVT system are obtained thus proving CVT’s functional applicability as a regulator for a changeable working regime. Presented approach can be used in choosing optimal parameters for the synthesis of this type of transmissions

Analysis of justification for applying two gear sets within the universal gear reducers

In the area of universal gear reducers, standard does not prescribe relations between load capacity, gear ratios and axis heights. Therefore, larger load capacity of some gear reducers manufacturers has advantage for lower gear ratio and, vice versa, smaller load capacity of the gearbox achieves higher values of gear ratio. However, there are some manufacturers who produce gear reducers with smaller or larger load capacity for higher or lower gear ratio, within the same axis height. This paper deals with analysis of justification of applying two gear sets, especially in the case when so-called intermediate sizes of gear reducer are not used

The Results of Changing the Current Solution Concept of Universal Motor Gear Reducers with Helical Gears

By analysing and comparing the existing solutions of universal gear reducers with helical gears of the leading manufacturers, it can be noticed the effort to increase the load capacity of the gear reducer within the same axis height. In this way, the manufacturers can offer smaller (cheaper) gear reducers, as well as to simultaneously increase the values of the largest gear ratios. This concept enables the offer of lower-stage (cheaper) gear reducers with higher gear ratios in certain segments of gear ratios. By these efforts, it is reached the maximum, but the further increase is possible only by changing the current concept of universal gear drives. Within this paper, it is given an overview and analysis of one of the possible new conceptual solutions of modern universal motor gear reducer

Assistive humanoid robot MARKO: development of the neck mechanism

The paper presents the development of neck mechanism for humanoid robots. The research was conducted within the project which is developing a humanoid robot Marko that represents assistive apparatus in the physical therapy for children with cerebral palsy.There are two basic ways for the neck realization of the robots. The first is based on low backlash mechanisms that have high stiffness and the second one based on the viscoelastic elements having variable flexibility. We suggest low backlash differential gear mechanism that requires small actuators. Based on the kinematic-dynamic requirements a dynamic model of the robots upper body is formed. Dynamic simulation for several positions of the robot was performed and the driving torques of neck mechanism are determined.Realized neck has 2 DOFs and enables movements in the direction of flexion-extension 100°, rotation ±90° and the combination of these two movements. It consists of a differential mechanism with three spiral bevel gears of which the two are driving and are identical, and the third one which is driven gear to which the robot head is attached. Power transmission and motion from the actuators to the input links of the differential mechanism is realized with two parallel placed gear mechanisms that are identical.Neck mechanism has high carrying capacity and reliability, high efficiency, low backlash that provide high positioning accuracy and repeatability of movements, compact design and small mass and dimensions

Development of the multi-segment lumbar spine for humanoid robots

The paper presents development of multi-segment lumbar structure based on the human spine. The research is performed within the project based on development of socially acceptable robot named "SARA". Two approaches for spine realization of humanoids exist: multi-joint viscoelastic structures (5-10 joints) that have variable flexibility and structures that consist of one joint - torso/waist joint, which has low elasticity and high stiffness. We propose multi-joint flexible structure with stiff, low backlash and self-locking mechanisms that require small actuators. Based on kinematic-dynamic requirements dynamical model of robot is formed. Dynamical simulation is performed for several postures of the robot and driving torques of lumbar structure are determined. During development of the lumbar structure 16 variant solutions are considered. Developed lumbar structure consists of three equal segments, it has 6 DOFs (2 DOFs per segment) and allows movements of lateral flexion ±30° and torsion ±45°, as well as the combination of these two movements. In development phase the movements of flexion/extension are excluded, for the bending of the body forward to an angle of 45° is achieved by rotation in the hip joints. Proposed solution of the lumbar structure is characterized by self-locking of mechanisms (if for any reason actuators stop working, lumbar structure retains current posture), low backlash (high positioning accuracy and repeatability of movements), compactness, high carrying capacity and small dimensions. [Projekat Ministarstva nauke Republike Srbije, br. III44008 and by Provincial secretariat for science and technological development under contract 114-451-2116/2011