Multi-link Mechanism Research Articles

Enhancing Spraying Performance with Active Stability Control in Multi-Link Mechanisms

This study proposes an active stability control method for the multi-link mechanism of spraying equipment to enhance its spraying performance. Traditional spraying operations typically focus on protecting only the tops of crops, whereas the multi-link mechanism can adjust the angle and position of the nozzles in coordination, achieving comprehensive protection for the crops. However, the characteristic of uneven output speed in the multi-link mechanism results in variations in the spraying amount at different positions. To address this issue, this study developed a method for actively adjusting the stability of the output end speed. First, a differential equation was established to relate the input speed to the output speed using vector methods, implicit function transformation to explicit functions, and regression analysis. The feasibility of this method was verified through simulations using MATLAB Simulink R2018a and Adams 2018. Prototype test results indicate that this speed adjustment method improved the stability of the output angular velocity, reducing the coverage rate variation between the upward, sideways, and downward of the leaves by 12.53% during the spraying process. Therefore, the method proposed in this study can enhance the uniformity of spraying, further improving the utilization of pesticides, which is beneficial for the green ecological sustainable development in the agricultural field. Additionally, this control method is also applicable to other types of link mechanisms, providing a reference for improving the output stability of link mechanisms.

Nonlinear dynamic analysis and optimization of planar flexible multi-link mechanism with clearance considering the thermal deformation effect of kinematic pair

Nonlinear dynamic analysis and optimization of planar flexible multi-link mechanism with clearance considering the thermal deformation effect of kinematic pair

Design of a Bionic Spider Robot with a Two-Degrees-of-Freedom Leg Structure and Body Frame

Spiders have unique biological characteristics and excellent maneuverability, making them an ideal model for bionic robot design. However, traditional bionic spider robot designs usually have multiple degrees of freedom and confront many challenges. These challenges include complex control requirements, higher energy consumption, larger size and weight, higher risk of failure, and higher cost. This study proposes a leg design with two degrees of freedom to reduce its control and manufacturing costs. It can better control leg movement and improve leg force through a multi-link mechanism and a dual-motor system. In addition, the triangular gait and hexagonal body structure align the weight of the body with the support point, thereby enhancing stability. This study offers a comprehensive and organized approach to bio-inspired robot design, providing a valuable reference for future bionic robot development.

Study on hydrodynamic performance of multi-link cycloidal propeller

Cycloidal propellers are special propellers that can obtain a wide range of thrust in any direction without changing the propeller rotation speed or requiring the assistance of a rudder. They are typically installed on ships with high-mobility requirements. The implementation of pure cycloidal blade pitch control is complex, and there are a few control mechanisms capable of realizing these blade pitch motions. In this paper, a multi-link mechanism is designed to control the movement of the blades, and the relationships between blade pitch angle, linkage lengths, and their adjustment angles are established. The linkage lengths and their adjustment angles are solved using a genetic algorithm. The blade pitch angle controlled by the multi-link mechanism matches well with the pure cycloidal pitch angle after adjusting the linkage lengths and adjustment angles. The layout of linkages for the six-blade cycloidal propeller is designed to ensure that there is no motion interference between the linkages and their supporting shafts during operation. The open water hydrodynamic performance of the cycloidal propeller controlled by the multi-link mechanism and pure cycloidal pitch motion is analyzed using computational fluid dynamics. The simulation results indicate that the cycloidal propeller can achieve similar performance with different control mechanisms.

Effect of over-expansion in a cycloidal rotary engine

An over-expanded (Atkinson cycle) reciprocating internal combustion engine is a crucial component of hybrid and range-extended electric vehicles. The realization of the over-expansion cycle with high efficiency in novel power devices with a compact, simple design, such as cycloidal rotary engines, is a promising alternative. The cycloidal rotary engine is an internal combustion engine that operates four strokes without a reciprocating mechanism and valve train. The over-expansion cycle is implemented in the cycloidal rotary engine by asymmetrical intake and exhaust port arrangements, resulting in open and closure timings. This study aimed to establish inherent characteristics of the over-expansion cycle in gasoline-fueled rotary engines with spark ignition. A numerical simulation of the gas exchange and combustion process in a wide range of over-expansion ratios was conducted. It was concluded that the over-expansion cycle is realized without typical piston engine methods such as variable valve timing and multilink mechanism. The thermal conversion efficiency is a peak function of the over-expansion ratio. In the over-expansion range of 1.1–1.2, the thermal conversion efficiency of the cycloidal rotary engine increased up to 32.7–34.5%. The benefits of fuel economy and carbon oxide emission can also be achieved within the specified range of over-expansion ratio.

Dynamic characteristics analysis of multi-link mechanism with clearances considering uncertain parameters

As a typical multi-body system, multi-link mechanisms are widely used in industry. Inevitably, there are joint clearances in multi-link mechanisms. Besides under the conditions of manufacturing, assembly and wear, the parameters of the multi-link mechanism can create uncertainty, and joint clearances and uncertain parameters of the multi-link mechanisms deteriorate the dynamic characteristics, this directly leads to a reduction in working accuracy of the mechanisms. At present, the research focus on multi-link mechanism with clearance considering certain parameters, and relatively few research on the multi-link mechanism with clearance considering uncertain parameters, the existing research on uncertain parameters mainly focus on the uncertainty of single parameter, while the research on the dynamic response of the mechanism with multi-clearances considering the uncertainty of multiple parameters is very less. The main purpose of this article is to provide a novel feasible method for studying the dynamic characteristics of multi-link mechanisms with joint clearances under the consideration of interval uncertain parameters and random parameters. Therefore, the dynamic characteristics of mechanism with multiple clearances considering uncertain parameters, which includes interval parameters and random parameters, are investigated in this article. Taking the 6-bar mechanism as the research object, considering clearances, Poisson’s ratios, stiffness coefficients, and driving speed as the uncertain parameters, the dynamic models of 6-link mechanism with multiple clearances considering interval parameters and random parameters are developed respectively. Using Chebyshev polynomial to solve interval parameters and polynomial chaos to solve random parameters, the effects of uncertain parameters such as clearances, Poisson’s ratios, stiffness coefficients, and driving speed on the dynamic response of the mechanism are analyzed, respectively. This research can not only provide a basis for studying the essential dynamic characteristics of multi-link mechanism with uncertain parameters, but also lay the foundation for dynamic optimization design of the real mechanisms.

Research on vibration isolation optimization design technology for the articulated link mount of turbofan engine

As an important structure connecting the aircraft and the engine, the turbofan engine mount often adopts a hinged multi-link mechanism, and its dynamic performance directly affects the transmission of engine vibrations to the fuselage. To study and improve the vibration isolation performance of this type of mount system, this paper proposes an optimization strategy based on modal design ideas, which takes the minimum distance between the natural frequencies of the mount system and the excitation frequency as the optimization objective, seeks the parameter solution that maximizes the optimization objective, and uses genetic algorithms to carry out optimization analysis. The results show that through optimization analysis, the effective vibration isolation range of the system is increased by approximately 125% near the excitation frequency of the low-pressure rotor; at the excitation frequency of the low-pressure rotor, the system transfer rate is reduced by approximately 58.4%; after optimization, due to the overall frequency deviation of the installation section system from the excitation frequency, the impact of small perturbations of the main parameters on its transfer rate is generally lower, with a maximum decrease of approximately 17.3%, greatly improving the robustness of the system.

Design of Bionic Landing Gear with Multi-Link Mechanism for UAVs in Desert Terrain

The terrain in desert areas is rugged and uneven, lacking suitable landing points for unmanned aerial vehicles (UAVs). In addition, sand and dust in the desert can easily damage the internal circuits of propellers through vortexes. To address the high demands for hardness and smoothness of landing sites for vertical takeoff and landing (VTOL) aircraft, as well as the low level of intelligence of traditional landing gear, an optimized biomimetic leg-type terrain-adaptive landing gear based on a multi-link hybrid mechanism was developed for landing in desert areas. First, the design configuration of a single leg was optimized, and the length of each link was calculated accordingly, followed by motion simulations. Secondly, the overall design was developed, and slope landing simulations were conducted on the four-leg mechanism. Research results showed that the optimized multi-link hybrid mechanism terrain-adaptive landing gear was better suited for adapting to desert terrain and could land on sand dune slopes, effectively improving the adaptability of VTOL aircraft in desert areas.

Nonlinear dynamic analysis of multi-link mechanism considering the wear effect of kinematic pair

Nonlinear dynamic analysis of multi-link mechanism considering the wear effect of kinematic pair

Dynamic error modeling, analysis and compensation of planar flexible multilink mechanism for high-speed precision presses considering the thermal expansion effect of sliding and angular contact ball bearings

Dynamic error modeling, analysis and compensation of planar flexible multilink mechanism for high-speed precision presses considering the thermal expansion effect of sliding and angular contact ball bearings

Development of a spatial orientation model for the actuator of a mechatronic system

Purpose. Development of a control system for a mechatronic system, taking into account the geometric solution of the inverse kinematics problem. The methods. The research was based on the principles of theoretical and applied mechanics, as well as the Denavit-Hartenberg transformation model. The formation of graphical computational models and kinematic diagrams simplified the development of the mathematical model of the dynamic system without considering the forces acting on the mechanism links. The possibility of using matrix transformations to simplify the search for generalized coordinates and transition to the local disposition of each link was explored for further integration of the obtained results into automation and control systems. Findings. The obtained results, determining the trajectory of the gripper using inverse kinematics models, allowed the development of algorithms for determining the position of mechanism links with the possibility of software implementation of the control system. Identifying patterns for determining accurate position coordinates by the matrix method allows the application of open-source software for real-time position calculations. The originality. The use of modern technologies for visual assessment of the external environment and coordinating control impulses of the executive body drive was first achieved based on the mathematical model of the inverse kinematics of a multi-link mechanism. This automated the determination of local coordinates for each link within its degrees of freedom and algorithmized this process. Combining the mathematical models of mechanism kinematics and the matrix form of coordinate search allows investigating the influence of the displacement of the i-th link of the mechatronic technical complex on the overall system, considering the acting force systems and the specified spatial orientation of both the executive body and intermediate links. Practical implementation. The implementation of obtained kinematic models using the matrix method enables the software realization of algorithms for searching the coordinates of the i-th mechanism link, automating the control process with the task of final positions, determining the level of integral error during the displacement of the initial link, and providing the possibility of programming autonomous mechatronic systems with open-source code. As a result, the introduction of semi or fully autonomous technical complexes will automate technological processes in various industries.

A New Type Bionic Foldable Wing Design for High Maneuverable Unmanned Aerial Vehicle

With the improvement of aircraft requirements in civil and military fields, aircraft are developing towards the direction of high efficiency and multi-mission. Foldable wing aircraft with large deformation capability will be able to meet flight requirements and performance under different conditions. Based on the bionic design concept, a feather-like foldable morphing wing based on a multi-link mechanism from the flight characteristics of birds was designed. In order to validate the feasibility of the proposed morphing wing conception, a UAV with bionic foldable wings was fabricated. The aerodynamic performance of the prototype model was tested under different working conditions by wind tunnel test and flight test. The simulation and wind tunnel experimental test showed that the prototype has excellent longitudinal and transverse directional aerodynamics. When the wing is symmetrically morphing, the optimal lift-to-drag ratio can be maintained under different flow velocities. When the wing is asymmetrically morphing, it can replace the aileron to achieve an efficient roll maneuver.

Dynamic response and nonlinear characteristics of multi-link mechanism with clearance joints

Dynamic response and nonlinear characteristics of multi-link mechanism with clearance joints

Dynamics research and chaos identification of rigid-flexible coupling multi-link mechanism with irregular wear clearances

Dynamics research and chaos identification of rigid-flexible coupling multi-link mechanism with irregular wear clearances

A versatile end effector for grabbing and spreading of flaky deformable object manipulation

Abstract. It is a conundrum to use robots to complete the intelligent operation of leather and clothing fabrics; this is mainly reflected in the design of an end effector that can realize this function. We have determined the design requirements and objectives of the end effector by observing the action of manually grabbing and spreading leather, and put forward an end effector composed of a reconfigurable multi-link mechanism and roller-type fingertip, which can be used to grab and spread flaky deformable object manipulation. At the same time, the reconfigurable multi-link mechanism and roller-type fingertip are introduced and analyzed in detail. By setting up the prototype of the end effector and completing the grabbing experiment of three kinds of soft pieces, we verified and tested the rationality of the prototype design. The result shows that the grabbing success rate will be affected by many factors, and further exploration is needed to further improve the performance of the end effector.

Study on nonlinear dynamics of rigid-flexible coupling multi-link mechanism considering various kinds of clearances

Study on nonlinear dynamics of rigid-flexible coupling multi-link mechanism considering various kinds of clearances

Adaptive nonlinear motion parameters estimation algorithm for digital twin of multi-link mechanism motion trajectory synthesis

Monitoring systems of automated production lines requires high accuracy and processing speed of acquired data. Nowadays digital twin technologies are rapidly developing as part of Industry 4.0. Digital twin is a virtual representation of a physical system that mimics the behaviour of a real object, and is used in real-time control, monitoring and disturbance prediction, without influence on a real object. Digital twin is being used in many fields of application such as: healthcare, manufacturing, education, city development, etc. Nonetheless, despite the rising popularity of digital twin researches, there is no basic approach to digital twin synthesis. Mostly, in state of the art articles, systems with known parameters are considered. In this paper, approach to development of digital twin, based on internal model for multi-link mechanisms with unknown motion parameters, is presented. Described approach intended to ease the task of production line monitoring and extend digital twin technology application field. In this article adaptive controller design, based on internal model, is presented, theoretical explanations of design process are provided, and application of the control algorithm in the task of multi-link mechanism motion trajectory parameters estimation is described. In this work the experimental synthesis of digital twin for Kuka youBot manipulator based on presented approach in real time is described. Adaptive motion parameters estimation was made for two links of the manipulator for the sake of confirmation of presented approach usage in the task of digital twin for systems with unknown parameters. Motion trajectory parameters of the robot links were defined manually with the use of chaotic generators to estimate the accuracy of the adaptive control system. This approach was used in order to calculate the error of reference tracking by comparing the control signal for digital twin with the reference exogenous input for manipulator links. As the results of the experiment, the graphs of the error reference tracking for both links are presented. As the goal of the experiment, the convergence of reference tracking error to the field [–0.005, 0.005] radian was set, and as can be seen from graphs this goal was achieved. There is a small disturbance of the error convergence on the graphs within the desired field which was caused by noised measurements and delays of the chosen modelling environment real-time simulations. In the conclusion of this paper, further work to reduce the influence of mentioned causes is described. The results of this paper can be used in further digital twin technology researches. Presented approach can be implemented in robots remote control tasks, production lines technical condition monitoring and in general motion trajectory parameters estimation tasks for multi-link mechanisms

Dynamics Optimization Research and Dynamics Accuracy and Reliability Analysis of a Multi-Link Mechanism with Clearances

With the development of high-speed and lightweight mechanisms, and the continuous improvement of manufacturing accuracy requirements in industrial production, clearance joints have increasingly become one of the key factors affecting dynamics performance. Poor clearance will seriously compromise stability, accuracy, and dynamics performance. Based on a genetic algorithm, an efficient modeling methodology for the dynamics optimization of a planar complex multi-link mechanism containing multiple clearance joints is put forward. The model comprises a 2-degree of freedom (DOF) nine-bar mechanism that can be used as the main transmission mechanism of a hybrid drive multi-link press, which is taken as the research object. The optimization objective is to minimize the maximum acceleration of the slider and minimize the difference between the actual central trajectory and the ideal trajectory. By optimizing the quality parameters of key components, an optimal solution for the design parameters is obtained, and the effects of the different optimizations of the objective functions on dynamics response are compared and analyzed. At the same time, a new modeling and calculation methodology of the dynamics accuracy and reliability of a complex multi-link mechanism in terms of multiple clearances is proposed, and the effect of optimization on dynamics accuracy and the reliability of the mechanism is analyzed. Based on the optimization results obtained by taking the minimum difference between the actual center trajectory and the ideal trajectory as an optimization objective, the nonlinear characteristics before and after optimization are analyzed through a phase diagram and Poincaré map. A test platform was built to study the dynamics of the mechanism with clearances. Research not only provides a basis for the dynamics optimization of a multi-link mechanism containing clearances but also provides reference significance for the reliability analysis of a multi-link mechanism containing clearances.

Experiment research and dynamic behavior analysis of multi-link mechanism with wearing clearance joint

Experiment research and dynamic behavior analysis of multi-link mechanism with wearing clearance joint

Dynamic modeling and analysis of multi-link mechanism considering lubrication clearance and flexible components

Dynamic modeling and analysis of multi-link mechanism considering lubrication clearance and flexible components