Synthesis Of Mechanisms Research Articles

Kinematic synthesis and simulation of a vegetable pot seedling transplanting mechanism with four exact task poses

To obtain a picking and planting integrated transplanting mechanism (PITM) with ideal trajectory shape, reasonable operating attitude, and compact structure for vegetable pot seedling transplanting, a symmetrical structural PITM composed of two planetary carriers and driven by a cam–noncircular gear combination mechanism was proposed in this paper. In accordance with the requirements of transplanting agronomy, the shape of the motion trajectory and the attitude of the end tip of the clamping claw at several specific positions (the starting and end points of picking seedling, the starting point of pushing seedling, and a special point on the return segment) were planned. To make the clamping claws of PITM pass through a set of prescribed positions, the mechanism was simplified to an open-chain 3R mechanism. An accurate four-position-based method for solving the open-chain mechanism model was adopted to obtain the curves of its fixed hinge point (central point) and dynamic hinge point (circle point). The ratio of adjacent bars’ lengths was analyzed to determine the feasible interval of the central and circle point curves and the reasonable link length. A desired closed transplanting trajectory that goes through the given points and the corresponding transmission ratio model of the open-chain mechanism was established. After the transmission ratio of each stage of gear and cam pairs was calculated and distributed, the prototype of PITM was designed and manufactured. Lastly, the effectiveness and feasibility of the design were verified through a preliminary experiment of the prototype. Keywords: kinematic synthesis, transmission ratio, non-circular gear, planetary carrier DOI: 10.25165/j.ijabe.20231602.6739 Citation: Sun L, Xu H C, Zhou Y Z, Shen J H, Yu G H, Hu H F, et al. Kinematic synthesis and simulation of a vegetable pot seedling transplanting mechanism with four exact task poses. Int J Agric & Biol Eng, 2023; 16(2): 85-95.

Обґрунтування механізму функціонування мехатронної системи склоочищення автомобіля

The four-link mechanism of the car's mechatronic windshield cleaning system is substantiated using different ratios of links and analysis of their kinematic and dynamic characteristics. A mathematical model of the glass cleaning mechanism in the Matlab/Simulink environment is presented and its kinematic synthesis is carried out. A mathematical model of the movement of the brush on the glass was developed for the case of close to uniform pressure distribution along the length of the brush, taking into account the unevenness of the law of movement associated with the operation of the transmission mechanism. The influence of the material properties of the rubber element on the quality of glass cleaning and the obtained values of the values characterizing the elastic and dissipative properties of the neck in the limit modes of the system are considered. The possibility of regeneration self-oscillations is shown when the dissipative properties of the neck are reduced as a result of wear or an aggressive environment. The processes of dry friction and hydraulic movement resistance occurring in the system are clarified, the limits of possible visually noticeable self-oscillations depending on the parameters of the friction mode and system operation are shown. It was found that the presence in the system of the possibility of regenerative self-oscillations in critical operating modes requires the introduction of micro-oscillations into the law of movement of the brush on the glass, which can effectively reduce the amplitudes of these self-oscillations. Analytical dependencies are proposed for calculating the parameters of the software, which implements the management of the dynamic characteristics of the system by superimposing the law of motion of micro-oscillations. The necessary hardware and software requirements for the controller are shown, as well as the possibility of saving the windshield wiper control unit as a functional unit of the mechatronic system for ensuring the comfort of movement.

A new family of twentieth order convergent methods with applications to nonlinear systems in engineering

A new family of iterative methods with a strong converging order of twenty to solve nonlinear equations and systems is presented in this study. A simple strategy of blending some existing methods is used to develop the proposed family. The theoretical order of convergence is derived by employing Taylor’s series. The performance of the iterative methods in the proposed family is examined by applying the methods on real-world engineering problems. A nonlinear equation modeled by NASA for launching “Wind” satellite and some other complex applied systems, such as combustion problem, tank-reactor problem, kinematic synthesis mechanism, neurophysiology application and one boundary-value problem, have been solved to check the performance of the proposed family against other methods under similar test conditions. All the numerical results show that the proposed family converges very fast in complex and difficult problems as compared to other well-known methods. The methods in the proposed family have an efficiency improvement of 11.99% over the classical Newton method for scalar nonlinear equations.

Development of a Novel Low-profile Robotic Exoskeleton Glove for Patients with Brachial Plexus Injuries.

This paper presents the design and development of a novel, low-profile, exoskeleton robotic glove aimed for people who suffer from brachial plexus injuries to restore their lost grasping functionality. The key idea of this new glove lies in its new finger mechanism that takes advantage of the rigid coupling hybrid mechanism (RCHM) concept. This mechanism concept couples the motions of the adjacent human finger links using rigid coupling mechanisms so that the overall mechanism motion (e.g., bending, extension, etc.) could be achieved using fewer actuators. The finger mechanism utilizes the single degree of freedom case of the RCHM that uses a rack-and-pinion mechanism as the rigid coupling mechanism. This special arrangement enables to design each finger mechanism of the glove as thin as possible while maintaining mechanical robustness simultaneously. Based on this novel finger mechanism, a two-finger low-profile robotic glove was developed. Remote center of motion mechanisms were used for the metacarpophalangeal (MCP) joints. Kinematic analysis and optimization-based kinematic synthesis were conducted to determine the design parameters of the new glove. Passive abduction/adduction joints were considered to improve the grasping flexibility. A proof-of-concept prototype was built and pinch grasping experiments of various objects were conducted. The results validated the mechanism and the mechanical design of the new robotic glove and demonstrated its functionalities and capabilities in grasping objects with various shapes and weights that are used in activities of daily living (ADLs).

Representation of random media in acoustic scattering calculations

Turbulence, internal waves, surface roughness, and other environmental variations in the atmosphere and ocean randomly scatter sound. Realistic representation of these variations is important for numerical wave propagation calculations. In principle, there are two primary approaches to create these representations: (1) physics-based, dynamical models for the atmosphere or ocean and (2) kinematic synthesis of random fields with prescribed statistical properties that do not necessarily capture the medium dynamics. The most common kinematic approach involves synthesizing fields from randomly phased Fourier modes. For statistically inhomogeneous media, the Fourier modes generalize to empirical orthogonal functions. An alternative kinematic approach, called filtered Poisson processes, distribute spatially localized functions with randomized positions and orientations. Quasi-wavelets (QWs) are a filtered Poisson process intended for turbulence and other self-similar media. While both the Fourier and QW approaches can be formulated to reproduce specified second moments of the random field, if the representations are constructed too sparsely, higher-order moments such as the kurtosis will be unrealistic. The kinematic approaches also underlie phase screen methods, which can be quite useful when the Markov approximation is valid.

Optimal synthesis of crank-rocker mechanisms with optimum transmission angle for desired stroke and time-ratio using genetic programming

Dimensional synthesis of crank-rocker mechanisms applied to provide some desired values of stroke and time ratio, is of utmost importance for designing an efficient mechanism. In the synthesis and manufacturing of crank-rocker mechanisms, the designers are further challenged by other design criteria, such as quality of motion. In this study, a novel approach based on genetic programming (GP) is proposed for dimensional synthesis of planar crank-rocker mechanisms with optimum transmission angle over the desired stroke and time-ratio. An analytical approach is elaborated which leads to an interesting relationship of length of the coupler and rocker links. It is, therefore, advised that by adopting equal lengths for coupler link and rocker link, one can guarantee the optimality of the transmission angle’s deviation ([Formula: see text]), ensuring the Grashof condition. Consequently, through an inverse modeling approach, GP method is utilized to construct some explicitly mathematical formulas to represent all the sizes and dimensions of the crank-rocker mechanism based on the any desired values of both stroke and time-ratio. In this way, an input-output data set consisting of all the dimensions and the sizes of the links as the input variables and both the stroke and time-ratio as output variables is first constructed using the pertinent mathematical equations. Indeed, such approach of inverse modeling using GP simplifies greatly the synthesis of the crack-rocker mechanisms for any desired values of both stroke and time-ratio. The proposed approach has been applied for kinematic synthesis of a crank-rocker mechanism. A comparison between the obtained results of this work and the analytic method, clearly illustrates the efficiency of the proposed approach.

Utilization of Function Generation Synthesis on Biomimetics: A Case Study on Moray Eel Double Jaw Design.

Throughout history, humans have observed living or non-living things in nature and then imitated them in relation to these observations. This is due to the fact that the energy found in nature is generally consumed at an optimal level in order for it to endure. Biomimetic inspiration in many designs and applications is widely displayed, including within the field of engineering. In this paper, we were inspired by the double set of jaws found in the moray eel, which gives this fish a huge advantage while hunting, with a mobile pharyngeal jaw that works together with its oral jaw in order to overcome ineffective suction capabilities. A procedure that mimics the hunting motion of the moray eel was utilized by considering the overall movement as a single degree of freedom with multiple outputs on account of the repeating motion that is required during hunting. This procedure includes structural and dimensioning synthesis, wherein the latter was utilized with analytic kinematic synthesis for each linkage transfer. The flexibilities in parameters were taken into account with a novel multiple iterative kinematic synthesis algorithm that resulted in various mechanisms with the same purpose. Among the excessive number of resultant mechanisms, the optimization was carried out by considering the highest torque transmission ratio at critical timings that were specified as bio-constraints. In the end, the kinematic movement validation was utilized.

Combining Uneliminated Algebraic Formulations With Sparse Linear Solvers to Increase the Speed and Accuracy of Homotopy Path Tracking for Kinematic Synthesis

Abstract The method of kinematic synthesis requires finding the solution set of a system of polynomials. Parameter homotopy continuation is used to solve these systems and requires repeatedly solving systems of linear equations. For kinematic synthesis, the associated linear systems become ill-conditioned, resulting in a marked decrease in the number of solutions found due to path tracking failures. This unavoidable ill-conditioning places a premium on accurate function and matrix evaluations. Traditionally, variables are eliminated to reduce the dimension of the problem. However, this greatly increases the computational cost of evaluating the resulting functions and matrices and introduces numerical instability. We propose avoiding the elimination of variables to reduce required computations, increasing the dimension of the linear systems, but resulting in matrices that are quite sparse. We then solve these systems with sparse solvers to save memory and increase speed. We found that this combination resulted in a speedup of up to 250 × over traditional methods while maintaining the same accuracy.

New Iterative Schemes to Solve Nonlinear Systems with Symmetric Basins of Attraction

We present a new Jarratt-type family of optimal fourth- and sixth-order iterative methods for solving nonlinear equations, along with their convergence properties. The schemes are extended to nonlinear systems of equations with equal convergence order. The stability properties of the vectorial schemes are analyzed, showing their symmetric wide sets of converging initial guesses. To illustrate the applicability of our methods for the multidimensional case, we choose some real world problems such as kinematic syntheses, boundary value problems, Fisher’s and Hammerstein’s integrals, etc. Numerical comparisons are given to show the performance of our schemes, compared with the existing efficient methods.

Analytical Modeling of a New Compliant Microsystem for Atherectomy Operations.

This work offers a new alternative tool for atherectomy operations, with the purpose of minimizing the risks for the patients and maximizing the number of clinical cases for which the system can be used, thanks to the possibility of scaling its size down to lumen reduced to a few tenths of mm. The development of this microsystem has presented a certain theoretical work during the kinematic synthesis and the design stages. In the first stage a new multi-loop mechanism with a Stephenson’s kinematic chain (KC) was found and then adopted as the so-called pseudo-rigid body mechanism (PRBM). Analytical modeling was necessary to verify the synthesis requirements. In the second stage, the joint replacement method was applied to the PRBM to obtain a corresponding and equivalent compliant mechanism with lumped compliance. The latter presents two loops and six elastic joints and so the evaluation of the microsystem mechanical advantage (MA) had to be calculated by taking into account the accumulation of elastic energy in the elastic joints. Hence, a new closed form expression of the microsystem MA was found with a method that presents some new aspects in the approach. The results obtained with Finite Element Analysis (FEA) were compared to those obtained with the analytical model. Finally, it is worth noting that a microsystem prototype can be fabricated by using MEMS Technology classical methods, while the microsystem packaging could be a further development for the present investigation.

Kinematic analysis and synthesis of cutter movement of slotting machine

The kinematic characteristics of the links and individual points of the mechanism are determined by the method of closed geometric contours and the method of designing plans. The forces of interaction between the links of the mechanism are determined by the method of kinetostatics, and the balancing moment by considering the dynamic equilibrium of the crank and the method of power balance. The drawbacks of the structural scheme of the mechanism are revealed and the ways of their elimination are offered.
 The results of research are presented in the form of graphical dependences of the kinematic parameters of the cutter, reactions or hodographs of forces in kinematic pairs. The moments of resistance forces and inertia forces are determined and the dynamic and mathematical models of the movement of the mechanism are constructed. The technology of determining the power of the electric motor is shown, and its stable area of operation is approximated by a straight line.
 Kinematic synthesis was performed and a modernized mechanism was obtained in which the cutter can move according to a predetermined law, in particular, without soft shocks at the boundaries of the kinematic cycle and with quasi-constant speed (error up to 5%) in the middle of the kinematic cycle

Computing saddle graphs via homotopy continuation for the approximate synthesis of mechanisms

An approach for approximate kinematic synthesis of mechanisms is proposed in this paper which computes a graph that identifies minima of an objective function as vertices and connections between them as edges. Such a graph is interactively presented to a designer, whereby edges are continuously traversed to navigate families of design candidates in between minima. Candidates are evaluated continuously according to auxiliary considerations for the exploration of design trade-offs. Relevant design specifications tend to be particular per application and are either unclear as how to incorporate into an objective, or clear but with great consequence to the complexity of function evaluation. Computing the aforementioned graphs begins with finding all minima and saddles of an objective function through polynomial homotopy continuation. Connections between minima that minimize their maximum objective value must pass through a saddle to do so. Therefore, after gathering saddles, each is perturbed both ways in its least eigendirection to seed gradient descent paths which connect two minima when pieced together. Discovered connections between minima are organized into a graph, where edges correspond to gradient descent paths.

A synthesis method of spatial over-constrained mechanisms based on kinematics of serial manipulators

AbstractThis paper proposes a modular method based on the kinematics of serial manipulators to synthesize over-constrained mechanisms. Because the PPP manipulator has an unlimited work space, its end-effector can be constrained to trace a trajectory identical to those of another open-chain manipulator, including a P joint single link and an RR dyad. In doing so, two open-chain manipulators can be concatenated to form closed-loop mechanisms, including PPPP, PPPRR, or PPCR mechanisms. To design over-constrained mechanisms efficiently, the Denavit–Hartenberg convention is adopted to describe the PPP manipulator kinematically, and the Euler angles are utilized to derive geometric constraints of synthesized over-constrained mechanisms. Next, kinematic equations of the PPP manipulator can be modularized and applicable to analyze different closed-loop mechanisms. At last, by adjusting link lengths, twisted angles, and joint angles of the synthesized PPPRR and PPCR mechanisms to form other over-constrained mechanisms configurationally. The novelty of this research lies in modularizing the over-constrained mechanism into two movable serial manipulators whose end-effectors share identical trajectory and orientation. Thus, defining geometrical constraints of the over-constrained mechanism can be transformed into finding angular parameters describing the orientation of these two serial manipulators such that the end-effector coordinate system of two manipulators can properly be aligned. Angular parameters of the serial manipulators can be easily determined by means of Euler angles, which yields an advantage of easy calculation since it only involves the computation of Euler angles parameters. The presented method can be extended to the kinematic synthesis and analysis of more spatial closed-loop mechanisms.

Innovative design method for planar mechanism configuration based on component similarity discrimination

Abstract. Obtaining new models of mechanical equipment to conduct mechanical innovative design through kinematic chain configuration synthesis is an effective method. However, in practice, due to the existence of similar components, existing innovative design methods easily produce redundant design schemes, which require extensive isomorphic discrimination operations, and the design process is complex. In view of existing problems, this study analyzes a method for discriminating between similar components of mechanisms from the perspective of graph theory and then applies it to the specialization of topological graphs to solve the problem of redundant design schemes. Finally, using the innovation of a drilling rig drilling arm mechanism as an example, 52 feasible schemes without redundancy are obtained. This paper provides a reference for the innovation of the configuration of planar mechanisms without design redundancy.

Optimal Design of an In-flight Refueling Door Mechanism

In this study, the preliminary design of an in-flight refueling door mechanism is performed. A systematic design methodology is introduced and used in the design of the refueling door mechanism. The design is divided into two sub-functions: door opening and actuation. Nine different mechanism concepts are created for the door opening function and eight different concepts are created for the actuation function. Pugh decision matrix method is used to evaluate and select the most feasible options. Six experienced engineers scored the option set, resultantly two concepts for the door opening and three concepts for the actuation sub-function are selected. Kinematic synthesis of these concepts is performed and used to determine the upper and lower bounds during optimization. Kinematic and force analysis of the concepts are performed and utilized for the constraints and cost function calculations of the optimization algorithm. Multi-objective Genetic Algorithm optimization technique is used to optimize the parameters of the selected mechanisms. The best mechanism for each sub-function is selected and combined to reach the final design. It was shown that through optimization, the required input torque decreased approximately 20% for the door opening mechanism and the required input force decreased approximately 42% for the actuation mechanism when compared to the graphical synthesis results.

Методы управления манипуляторами на базе трипода при выполнении технологических операций

Parallel-serial (hybrid) structure manipulators are widely used in various sectors of the economy, which makes it possible to take into account the disadvantages and combine the advantages of manipulation systems of parallel and serial structures. Studies of technological processes have shown that they can be performed using manipulators of a parallel-serial structure based on a tripod, the features of which are not fully understood. Whereas it is important to choose a control system and control algorithms that depend on the characteristics of technological operations performed. Manipulator controlling is a complex task that includes positioning of the effector, planning and synthesis of trajectories, setting and moving the effector along a given trajectory. Each technological process can be described by a set of special trajectories, which can be entered in advance into the database of control models. The article formalizes the trajectories of the effector on the example of specific technological operations. Using the techniques of kinematic and dynamic synthesis, analytical algorithms for its movement along these trajectories have been developed. Theoretical studies were tested on the experimental sample of a hybrid structure manipulator with SKF CAHB-21 actuators. The experiments showed that positioning errors did not exceed 2%, and the deviation of the actual movements from the specified ones in the presence of a payload on the gripper did not exceed 5 %.

Mixed Position and Twist Space Synthesis of 3R Chains

Mixed-position kinematic synthesis is used to not only reach a certain number of precision positions, but also impose certain instantaneous motion conditions at those positions. In the traditional approach, one end-effector twist is defined at each precision position in order to achieve better guidance of the end-effector along a desired trajectory. For one-degree-of-freedom linkages, that suffices to fully specify the trajectory locally. However, for systems with a higher number of degrees of freedom, such as robotic systems, it is possible to specify a complete higher-dimensional subspace of potential twists at particular positions. In this work, we focus on the 3R serial chain. We study the three-dimensional subspaces of twists that can be defined and set the mixed-position equations to synthesize the chain. The number and type of twist systems that a chain can generate depend on the topology of the chain; we find that the spatial 3R chain can generate seven different fully defined twist systems. Finally, examples of synthesis with several fully defined and partially defined twist spaces are presented. We show that it is possible to synthesize 3R chains for feasible subspaces of different types. This allows a complete definition of potential motions at particular positions, which could be used for the design of precise interaction with contact surfaces.

Conceptual configuration design of line-foldable deployable space truss structures employing graph theory

From the perspective of the truss as a whole, this research investigates the conceptual configuration design for deployable space truss structures that are line-foldable with the help of graph theory. First, the bijection between a truss and its graph model is established. Therefore, operations can be performed based on graph models. Second, by introducing Maxwell’s rule, maximum clique, and chordless cycle, the principle of conceptual configuration synthesis is analyzed. A corresponding procedure is formed and it is verified by a truss with seven nodes. Third, assisted by some theorems of graph theory, the simplified double-color topological graph of deployable space truss structures is acquired and it also displays the procedure with a case. Finally, based on the above analysis, it obtains the optimal conceptual configurations. This novel research lays the foundation for kinematic synthesis and geometric dimension designs.

Problems of power division between the devices of agricultural machine-tractor units

Purpose. Determination of the rational use of various types of transmissions in the creation of multi-moving agricultural machine-tractor units. Methods. Analysis of technical characteristics of sources of mechanical energy, synthesis of power distribution system using motor-wheels. Results. Based on the analysis of literary sources, proposals were received for the choice of transmissions for multi-moving agricultural machine-tractor units. A kinematic synthesis of an electromechanical transmission for individual propellers for various purposes is proposed. Conclusions 1. The maximum transport speed of modern agricultural tractors is in the range of 40 ÷ 50 km/h, and the minimum technological speed at the maximum power of the traction vehicle (TV) can be within 4 ÷ 5 km/h when working with a soil loosener. 2. Modern agricultural TV should have a ratio of maximum speed to minimum speed up to 10. 3. The nominal range of rotation frequencies of traction electric motors available on the market is not able to overlap the ratio more than 2 ÷ 2.5. 4. The kinematic combination of the rotation frequencies of two electric motors allows you to cover the range of operating speeds of the MTA without mechanical switching of the transmission elements. 5. The proposed autonomous motor-transmission unit allows to compose MTA with the distribution of electrical power between additional engines of technological modules of MTA. Keywords: machine-tractor unit, transmission, traction concept, mover, electric wheel motor.

The effect of the initial size on the height of the crank press die

The expansion of the technical and technological capabilities of forging and stamping machines and equipment can be carried out through the introduction of new designs of actuators with wide functionality. These developments require solving the problems of kinematic synthesis and analysis of mechanisms. In this work a comparative analysis of the endurance indicators of a crank press with the mechanism for transforming the motion of Stephenson II depending on the elastic compliance of the connecting rods and the deformation of the forging was shown. In this regard, the features of the kinematics of a crank press driven by an asynchronous motor taking into account the flexibility of the connecting rods and the workpiece was investigated.