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The low backlash planetary gearbox as a substitute for a harmonic drive in humanoid robotics, is presented in this paper. After analysis of the contemporary designs of the low backlash coaxial toothed gearboxes, a concept of planetary gearbox with taper gears has been chosen. A synthesis of a planetary mechanism which satisfies the prescribed kinem...
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In this paper the authors present the newest designs of worm gear drives which allow to adjust or decrease the amount of backlash. This effect is achieved with innovative designs of worms and worm wheels. The designed drives are aimed to find their application in systems for precise positioning of measurement assemblies, precise drives of technolog...
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... Sajin et al. [42] used the planetary gear train for fishing boat propulsion. Borovac et al. [43] developed a low backlash planetary gearbox for human-robot applications. The EGT layouts whose d.o.f > 3 are found to be so large in number that it becomes practically impossible to derive all of them in a reasonable period without the aid of a fast computer. ...
Epicyclic Gear Transmission Systems (EGTs) find a wide variety of applications in automatic transmission systems due to their flexibility to deliver a variety of speed ratios. The design of EGT involves the enumeration of all possible layouts, typically called structural synthesis. Thus, the structural synthesis of an EGT consists of defining a topology for EGT with coupled planetary gear trains (PGTs) along with constraining elements such as connections, brakes, and clutches while delivering a definite transmission ratio between the input and output shafts. Given the number of PGTs, permanent connection, clutches, and brakes, the methodology systematically introduces these elements of PGTs to deliver the given number of distinct speed ratios. Determining the number of distinct speed ratios for a given combination of brakes and clutches has been expressed as a transformation of a graph representation of the EGT layout. A computer program has been developed for the structural synthesis of EGTs and validated against the 3 epicyclic, 6-speed EGT systems. The viability aspects of the synthesized structure are carried out. Also, an isomorphism test is addressed in the synthesis methodology to detect unique EGT structures at every synthesis stage.
... This problem is further complicated by the fact that different batches of products differ in permissible deviations in the dimensions of assembly objects [1]. Therefore, initially, it is necessary to improve the accuracy of assembly, as noted in [2]. The most important is to ensure the reliability of the assembly in the conditions of mass production, which uses assembly lines of various types [3]. ...
... Let us apply pressure p 2 to this element and compose the equilibrium equation for the selected element in projection onto the external normal. As a result, we get: 2 ...
In modern production, automation of assembly processes is achieved by using industrial robots with high positioning accuracy, as well as with elements of tactile adaptation and expensive software. The article proposes an alternative approach to solving the problem of reducing the cost of assembly processes. This approach consists of using production tooling in the form of a soft adaptive assembly module that is mounted on the robot arm. The proposed assembly module allows not only for compensating for errors in the relative orientation of assembly objects, but also excludes the possibility of damage to fragile assembly components or for assembly objects with a thin protective coating of a chemical or galvanic nature. This effect is achieved due to the use of elastic corrugated chambers in the module structure, which, when compressed air is supplied to them, correct the position of one of the assembly objects. The article offers a description of the new design of the assembly module, as well as offers analytical dependencies for calculating the design parameters of the module. The results of modeling the parameters of the assembly module are presented. The main economic effect is to reduce the cost of technological equipment for industrial robots while maintaining the ability to adapt to the conditions of the assembly process.
... In the case of universal toothed gearboxes as explained clearly [6], level of the backlash is not very important, but it has great importance for low backlash gearboxes low backlash between meshed gears is necessary for the required positioning accuracy. ...
... Low backlash planetary gearboxes with spur gears are the ones most commonly used, since they are very compact, simple, and cheap, as well as having a small arc backlash. Low backlash is achieved with precise manufacturing and selection [6]. ...
... Simulation as well as experimental results are presented to show the applicability of this hybrid control approach. Penčić et al. [6] performed low backlash planetary gearbox as a substitute for a harmonic drive After analysis of the contemporary designs of the low backlash coaxial toothed gearboxes, a concept of planetary gearbox with taper gears has been chosen. ...
Gears are the machine elements used widely for transmission of torque and motion it follows that transmission of power. In applications the main aim is to transmit torque gears usually rotate unidirectional whereas in applications where main aim is to transmit motion gears usually rotate bidirectional. In both cases, even if rotates unidirectional or bidirectional, a certain amount of space (free angular movement usually called “backlash”) between meshing teeth flanks are allowed for functional reasons. Backlash is a need for proper gear mesh also a defect if it is not controlled closely. One of the gear drive types used in robot, like critical applications is planetary gearbox. Therefore, establishing backlash value in planetary gearboxes is a practical problem for critical industries. In this thesis, pertinent parameters effecting backlash of a planetary gearbox will be determined and relations between each parameter and backlash will be formed. Assuming that an assembly line of a pair of gears are supplied with hundreds of driving and driven gears each of which was measured, and all measured data are stored in a data base. The software will estimate likely maximum and minimum backlash of a pair selected. Thus, a method of assembly procedure will be performed a range of backlash for planetary gearboxes. Such selected pairs with targeted backlash range is predicted via the software and it will help speed up the assembly process and reduce the number of rejected for planetary gearboxes assemblies.
... So, the orientation of flat parts had been already described in some studies [9], a model of mixing parts was proposed, in which flat parts are periodically thrown by a simple throwing surface with one degree of freedom, captured and allowed to settle the parts in the desired position. Studies [10] prove the positive effect of increasing assembly accuracy on the efficiency and load capacity of robotic mechanisms. Improving assembly accuracy is especially important in the context of mass production, which is based on assembly lines of various types [11]. ...
... The coefficients for paired interaction of factors 1 3 x x and for triple interaction of factors 1 2 3 x x x in equation (10) after checking the significance of the coefficients of the regression equation using the Student's t-test turned out to be insignificant. Therefore, they were excluded from the regression equation (10). ...
... The coefficients for paired interaction of factors 1 3 x x and for triple interaction of factors 1 2 3 x x x in equation (10) after checking the significance of the coefficients of the regression equation using the Student's t-test turned out to be insignificant. Therefore, they were excluded from the regression equation (10). The resulting regression model for the assembly of precision parts allows one to study the influence of independent factors of the response function on the optimization parameter, i.e. assembly time. ...
At present, robotization of assembly processes is achieved through the use of industrial robots with high positioning accuracy in conjunction with tactile means of adaptation to the conditions of assembly of precision parts. The cost of such robots is many times higher than the cost of simple robots with low positioning accuracy of the robot arm. The research in this article is aimed at reducing the cost of assembly processes for precision parts by applying the position correction of the connected parts not by the robot hand, but by an additional technological module that is installed on the manipulator of a simple robot and performs high-speed stochastic mismatch scan of assembly objects. The article presents the results of a full factorial experiment of the process of joining precision cylindrical parts with a gap of no more than 3...5 microns. A regression model of this process is proposed, a formula for calculating the quasi-optimal modes of precision assembly and graphanalytical dependences of the assembly time on the scanning modes of the misalignment of assembly objects are given. The proposed high-speed method for compensating for the positioning error of an industrial robot makes it possible to assemble precision parts in a very short time within 1...3(s). The main economic effect of the research results is that the device for scanning the misalignment of assembly objects, which is installed on the arm of an inexpensive robot with a low positioning accuracy, can significantly increase the assembly speed and reduce capital investments in robotic assembly of high-precision parts.
... A remarkable construction of a biomechanical arm with seven degrees of freedom and original drives was proposed in [14]. This technical solution illustrates the effectiveness of the use of anthropomorphic designs of robots to perform technological operations. ...
The article presents a fundamentally new design of an anthropomorphic walking device for a mobile robot. The novelty of the proposed design lies in the fact that each part of the leg of the robot is made in the form of four corrugated pneumatic chambers that are mounted on spherical hinges. This design allows the robot to move in an angular coordinate system, which is typical for humans. A mathematical model of an elastic walking device is proposed and analytical dependences are given for calculating the geometric and strength parameters. The results of mathematical modelling and recommendations for the design of anthropomorphic walking mechanisms are given. The engineering formulas and diagrams for calculating power loads described in the article allow you to create various modifications of walking robots that have the property of adapting to an arbitrary surface topology for moving a mobile robot. The stated research results allow us to expand the technological capabilities of mobile robots.
Keywords: industrial robots, walking mechanisms, climbing robots, anthropomorphic devices, robots’ design.
... Therefore, the power transmission from the actuatormotor with integrated gearhead, to the output link of the waist joint/mechanism is performed through an additional high-power gear reducer with a high reduction ratio, such as multi-stage epicyclic gearboxes, planetary roller screws and high-power harmonic drives. In addition to the high load capacity, the advantage of these mechanisms is high efficiency, compact design and low backlash ensuring high positioning accuracy and repeatability of the robot movement, which is of great importance for motion control [23]. ...
The paper presents the dynamic analysis and motion simulation of the waist mechanism meant for humanoids. The proposed waist mechanism has a total of 3 DOFs, allowing movements of the robot’s upper trunk around the pitch, roll and yaw axes. Within the dynamic analysis, the decomposition of the waist mechanism is performed and for each link of the mechanism, motion equations are formed. Reactions in the mechanism links are determined by using D’Alembert’s principle and based on those, the equations for calculating of the driving forces are defined. Finally, the dynamic model of the waist mechanism was formed and a motion simulation for several scenarios was performed. Based on the analysis of the results, it was concluded that the waist mechanism requires small driving torques and therefore less and cheaper actuators, which is an important advantage of this solution.
... For example, planetary reduction gears may be used to operate a two rope grab as pointed out in [1]. Furthermore, harmonic drives in humanoid robots may be successfully substituted by a low backlash planetary gear box [2]. PGTs as a whole, and especially compound multicarrier PGTs represent a very extensive area of technical knowledge [3], and therefore compound PGTs are usually divided into simple and higher [3]. ...
Planetary gear trains (PGTs) offer numerous benefits when compared to conventional gear trains, e. g. multi-carrier planetary gear trains may be built by linking the shafts of different component planetary gear trains. A two-carrier two-speed PGT consisting of two coupling shafts and four external shafts is a special type of multi-carrier PGT. This type of compound gear train has many important characteristics, the most notable being the possibility to change the transmission ratio under load. This paper presents a method for quick determination of the structure and important basic parameters of two-speed planetary gear trains that meet the predefined transmission requirements. A computer program developed for the examination of two-speed planetary gear trains DVOBRZ is used for this purpose. A numerical example of the procedure is provided, dealing with the application of a two-speed PGT as a fishing boat reduction and reversing gearbox.
... These robots have a waist joint/structure with 1, 2 or 3 DOFs allowing trunk movements around the pitch, roll and yaw axes. Modern waist joint/structures contain reliable and low backlash mechanisms, such as epicyclic gear trains, harmonic planetary gears, harmonic drives and cycloidal reducers, enabling high positioning accuracy and repeatability of movements which is essential for motion control [19]. However, deficiency of these mechanisms is a very high price that limits their use. ...
The paper presents the kinematic analysis and motion simulation of the waist mechanism for humanoid robots. The waist mechanism with total 3 DOFs is proposed. It consists of two interconnected spatial mechanisms that allow movements around the pitch and roll axes, while the third is planar mechanism for movements around the yaw axis. Due to the structure of links, spatial mechanisms can function independently and/or simultaneously. By kinematic analysis of the waist mechanism, the kinematic parameters are defined and based on that, a kinematic model is formed. Motion simulation of the waist mechanism for initial movements of flexion, extension, lateral flexion and rotation is performed. For the corresponding movement and range of motion, the waist mechanism reaches the kinematic parameters of the human lumbar spine region, which was the basic requirement for realization.
... transmission ratio i of the worm pair is calculated and has value i = 14. Such transmission ratio ensures high reduction of the torque as well as increased number of the teeth in the mesh thus having positive effect on the minimization of the backlash which is essential for motion control [18]. Using Eq. (9), coefficient of efficiency of the worm pair is η = 0.75. ...
Having in mind that humans use non-verbal communication extensively is very important to enable social robots with this capacity. There are two basic ways how it can be expressed. First one is by facial expressions by appropriate moving face parts, like eyebrows, eyeballs, eyelids, lips, either as manufactured real parts or by presenting them on screen—combining them is also possible. The second way of non-verbal communication is by gestures. This paper presents the kinematic-dynamic analysis of shrug mechanism for humanoid robots. Based on the set requirements, the cam-worm mechanism that has 1 DOF and enables the simultaneous shrug of both shoulders is proposed. It consists of a worm which is meshed with two worm gears whose directions of rotation are opposite and the two cam mechanisms whose input links—cams, are rigidly attached to the worm gears. Within the kinematic-dynamic analysis, the cam profile and the worm parameters are defined and the torque on the cam/worm gear and the driving torque of the complete cam-worm mechanism are determined. The cam mechanism has a high efficiency in all positions because the values of the pressure angle are within the prescribed ones during the entire movement. Worm mechanism enables a significant reduction of the driving torque and has acceptable efficiency. The rotation range of worm gear/cam is small and the movement of mechanism is very fast wherefore the shrug speed is large, which was one of the main requirement for realization. © 2018, Springer International Publishing AG, part of Springer Nature.
... Due to mechanical, sensing and control complexity, compliance control is still an open and very challenging research topic. Recent progress in the development of soft and humanoid robots (including robots with multiple and cooperating arms), especially their extensive implementation in complex tasks with intensive human-robot physical interaction as well as in constrained motion tasks where precise morphing of the robot taskspace stiffness is essential for successful task execution -increase the importance of compliance research, [4], but also backlash in joint actuation system [5]. New understanding of underlying phenomena and consequently, new extensions, or at least refinements of the already existing theory are necessary, [6]. ...
... Contrary to the nonredundant robot mechanism, the inverse kinematics of a kinematically redundant robot has a more general solution, which is composed of two components: the nonhomogeneous member, i.e., particular solution δq P of the nonhomogeneous linear system (5), and the homogeneous member, i.e., the solution δq N which is related to the nullspace of Jacobian matrix, (11) and analytically defined by (12). This leads to the definition of the generalized virtual displacement which can be analytically expressed by the following relation: (13) where: J + (q) is the generalized inverse of the Jacobian matrix J(q) which satisfies Moore-Penrose least norm condition, δq 0 is an arbitrary vector from the robot configuration space, and P c N(J) is the complementary projector, i.e., an operator which projects the vector δq 0 to the nullspace of Moore-Penrose generalized inversion J + (q) of the Jacobian matrix. ...
When the robot endpoint compliance is dominantly influenced by theflexibility of its joints, the robot taskspace generalized stiffness matrix canbe mapped onto jointspace using appropriate congruence transformation. Thus produced, the jointspace stiffness matrix is generally nondiagonal. Off-diagonal elements can be generated by redundant actuation only(polyarticular actuators). Although this kind of actuation is widely presentin biological systems, its practical implementation in engineering systemsis very difficult. To overcome this problem, use of kinematic redundancy isproposed. This two-part paper presents an approach to the control ofrobot endpoint compliance, i.e., elasto-mechanical interaction between arobot and its environment using kinematic redundancy instead of actuationredundancy. In Part I this approach is developed by proposing theConfiguration-based Stiffness Control (CSC) method for kinetostaticallyconsistent control of robot compliant behaviour, based on the gradientprojection of the cost function which minimizes the norm of off-diagonalelements of the jointspace matrix.
