Dynamic Analysis Of Mechanical Systems Research Articles

Kinematic and Dynamic Analysis of Eccentric Balanced Positive Torque Pumping Unit

Beam pumping units have numerous energy transfer links, significant net torque fluctuations and negative net torque in gear boxes, which lead to a high installed power and low system efficiency. In order to improve the efficiency of the pumping unit, in this paper, an eccentric balanced positive torque pump unit was designed based on the principle of eccentric balance that is small in size and adopts a flexible energy transfer system instead of a rigid structure to significantly reduce the energy transfer link. The kinematics and dynamics of the eccentric balanced positive torque pumping unit were analyzed and the ability to operate with positive torque over the entire cycle was verified using theoretical computations. And the results of the theoretical calculation were verified by using the virtual prototype simulation and analysis software ADAMS (Automatic Dynamic Analysis of Mechanical Systems); the pumping unit was optimized for relevant parameters such as the balance crank angle λ and the counterweight center of mass offset angle δ. Indoor testing and comparative field application have demonstrated that the installed power has been reduced by 80%, the weight of the entire prototype has decreased by 25% and the system efficiency has reached 24.3%. Additionally, electricity savings of over 50% have been achieved. These results indicate that the pumping unit has been designed correctly, has high reliability and has significantly improved system efficiency while also providing an obvious energy-saving effect.

Extended component mode synthesis method for dynamic analysis of mechanical systems with local nonlinearities

Engineering structures are generally designed based on linear elasticity assumptions. However, it is difficult to describe the connected structures using a simple linear system, due to factors such as sliding and friction at interfaces, and variations in contact areas during vibration processes. Therefore, it is necessary to develop an approach to tackle such systems with interface nonlinearities. In this paper, we proposed an extended free-interface component mode synthesis method. According to the proposed method, the substructures are separated at the nonlinear interfaces. Then the component mode synthesis procedure is carried out. By reasonably neglecting the contributions of higher order modes to the damping and inertia terms, it is demonstrated that the nonlinear interface forces and their time derivatives can be expressed as functions of themselves, as well as modal displacements and velocities. This characteristic facilitates the synthesis of the reduced order models for substructures in the state space. Also owing to this operation, the original properties of nonlinear interface forces can be preserved as much as possible, without any linearization. This method is suitable for non-proportionally damped structures with local nonlinearities such as mechanical structures with nonlinear spring and dashpot connections, rotor-bearing systems and so on. It also may be an alternative for the dynamic analysis of jointed structures with contact nonlinearities. Two numerical examples are presented to demonstrate the capability of the proposed method: (1) an eighteen degrees of freedom spring-dashpot-mass system with cubic spring and cubic dashpot interface connections is studied and (2) a more complex mechanical structure: a dual-rotor system with deep-groove ball bearing inter-shaft support. The numerical simulation results indicate that the dynamic responses of the reduced order model match very well with that of the full model, revealing the high accuracy of the proposed method with low computational costs.

Non-linear stochastic dynamics analysis of mechanical systems using non-intrusive polynomial chaos method: application to pole vaulting

Non-linear stochastic dynamics analysis of mechanical systems using non-intrusive polynomial chaos method: application to pole vaulting

Modeling and validation of a novel tracked robot via multibody dynamics

AbstractThis article focuses on a multibody model of a new passive articulated suspension tracked robot. The model of the vehicle is developed using the multibody software MSC Adams (acronym for automatic dynamic analysis of mechanical systems) in conjunction with the Adams Tracked Vehicle toolkit. The various subsystems that make up the vehicle assembly are described, with particular attention to the modeling strategies of the swing arms that constitute the suspension system and the characterization of the track belt. The multibody model allows the system performance to be evaluated in advance for fine-tuning of the design parameters and using different configurations, for example, with active and locked suspension. Efforts are also presented to validate the multibody twin against the real prototype, showing a good agreement with field experiments. Once validated, the digital twin is used to assess the performance of the innovative suspension system in various challenging environments.

Analysis and Test of the Tillage Layer Roll-Type Residual Film Recovery Mechanism

With the extensive use of plastic film mulching in planting, the amount of residual plastic film in soil has been increasing, causing soil and water pollution, harming crop growth, and reducing agricultural product quality and yield. In response to this issue, this study proposes a roll-type residual film recovery mechanism using the tillage layer method. The structure and operation principles of this system are discussed, and a detailed analysis of its key components and working process is provided. The lifting cutter operates at a speed of 22.37 rad/s, the pick-up drum at 4.58 rad/s, the roll forward rotation picks up the film at 13.74 rad/s, and the roll reverse film rotation unloads the film at 17.57 rad/s, with the unloading wheel rotating at a speed of 4.5 rad/s. ADAMS (software of automatic dynamic analysis of mechanical systems) Version No.2019 is used for modeling and analysis, and the displacement and velocity change patterns of MARKER_499, MARKER_500, and MARKER_505, which are marked points of the spring-tooth tips and are found to be the same. The maximum resultant displacement of MARKER_499 and MARKER_500 is 22.146 mm when picking up plastic film and 17.047 mm when unloading plastic film. Meanwhile, the maximum resultant displacement of MARKER_500 and MARKER_505 is 231.715 mm in the film-picking area and 234.028 mm in the film-unloading area. After analyzing the velocity of MARKER_499 during picking and unloading of the film, it was determined that the absolute velocity for the picking direction was 79,809.407 mm/s, and for the unloading direction it was 10,2266.168 mm/s. Bench tests show a tillage gathering rate of 71.6% and a surface gathering rate of 83.4%, meeting the performance requirements of the roller-type residual film recovery mechanism. These findings provide a theoretical basis for the design of the structure and operational parameters for the roll-type residual film recovery mechanism using the tillage layer method.

A bivariate subinterval method for dynamic analysis of mechanical systems with interval uncertain parameters

Dynamic analysis involving interval uncertainties can provide accurate reference to performance evaluation and reliability optimization. However, methodologies for dynamic problems under high dimensional interval uncertainties in mechanical systems need further exploration and development. To this end, this paper proposes a bivariate subinterval method (BSM) to handle interval dynamic problems, in which multiple uncertain parameters with small uncertainty levels in mechanical systems are involved. The BSM is developed by combining the subinterval technique and the bivariate decomposition of response functions expanded by the second-order Taylor series. Additionally, the subinterval-division-based bivariate subinterval method (SBSM) is developed to obtain a tight bound for the dynamic analysis of mechanical systems considering interval parameters with large uncertainty levels. To verify the efficiency and accuracy of the developed methods, numerical examples and engineering applications with consideration of interval uncertainties are employed and discussed. Results show that compared with the existing bivariate Chebyshev method, the BSM presents a better tradeoff between the accuracy of results and computational cost, which is more suitable to interval dynamic problems for the analysis of mechanical systems with uncertainties of high dimensions and small uncertainty levels. Furthermore, the SBSM can obtain a tight bound of dynamic responses for the interval dynamic problems with uncertain parameters of low dimensions and large uncertainty levels in mechanical systems.

Simulation evaluation of underwater robot structure and control system based on ADAMS

Abstract The twenty-first century is the century of marine resources. The ocean is a treasure of biological resources, energy, water resources and mineral resources, and it would gradually become the “second space” of mankind. In the next few years, it would be more and more relevant to human life. Many scholars have realized the importance of the ocean and began to vigorously develop and use the ocean. Underwater robot is a means for human beings to explore and develop the ocean, and it would be widely used in this field. The development and promotion of underwater vehicles are of great significance to resource development, economic development, and national security. With the increasing shortage of land resources, the development and utilization of marine resources have received increasing attention. The direct exploitation of marine resources by humans would have adverse effects, so the underwater robot technology has developed rapidly in recent years. However, at present, most underwater robots are driven by electric turbines. The underwater working environment requires that the underwater motor has good sealing performance, so its structure is complex and expensive, and it is rarely used in ordinary underwater operations. In recent years, intelligent robots have been used more and more, but because of the complexity and uncertainty of the underwater working environment, there are many uncertain factors. Therefore, it is very meaningful to carry out stability control for it. The research results showed that the displacement, stability, and other corresponding test curves of each component can be obtained by establishing a simple model with software and through ADAMS (Automatic Dynamic Analysis of Mechanical Systems) simulation analysis. This can simulate the movement of real objects in the real environment and find the existing problems, so as to provide a reference for the actual underwater robot design. In this way, the development cycle and production costs can be reduced. This article analyzed the structure and control system of the underwater vehicle based on ADAMS simulation. The results showed that the dynamic stability of the underwater vehicle based on ADAMS simulation analysis was improved by 4.67% compared with the underwater vehicle before optimization.

Complex Positioning System for the Control and Visualization of Photovoltaic Systems

This paper presents a proposal of a complex mechatronic system that enhances the effectivity of obtaining energy from renewable resources. The main focus is on the photovoltaic energy system, which obtains electricity from the conversion of solar radiation through photovoltaic crystalline silicon-based panels. The design of the complex mechatronic system consists of several steps. The structural design of the photovoltaic panel positioning unit in the form of a three-dimensional model is made in the selected modelling programming environment. Subsequently, a propulsion system is proposed for the designed structure, the functionality of which is verified in the programming environment Automated Dynamic Analysis of Mechanical Systems. The control system design using a programmable logical controller is also presented. The corresponding control algorithm is designed in the programming environment Step7 and covers the optimal positioning of photovoltaic panels. The developed application in the WinCC environment provides a visualization of the positioning control process. The conclusion is devoted to the assessment of the obtained results for the proposed complex mechatronic system for photovoltaic panel positioning in comparison with photovoltaic panels in fixed installation. The presented results were obtained by simulations.

Moment Lyapunov exponents and stochastic nonstability of a circular cylindrical shells

The paper investigates the stochastic stability conditions of circular cylindrical shells, compressed by time-dependent stochastic membrane forces. The main contribution of the paper is the determination of the moment Lyapunov exponents of the linear cylindrical shell for the first time. The moment and almost-sure stochastic stability of a three-degree-of-freedom coupled continuous system, under parametric excitation of white noise, are investigated. It is assumed that the system possesses a small damping. This type of a shell structure model requires a specific scheme for determining the moment Lyapunov exponents. The system of stochastic differential equations of motion is decoupled by using the contact transformation method with the obtained appropriate symplectic matrix of the system. Then a scheme for determining the moment Lyapunov exponents is presented which contains an analytical procedure. The largest Lyapunov exponent is calculated through its relation with the moment Lyapunov exponent. The moment and almost-sure stability boundaries are obtained analytically. These results are important and useful in engineering applications as an example of a procedure for dynamic analysis of mechanical systems with coupled stochastic oscillators.

Numerical Method of Designing an Automotive Driving Simulator for Training Drivers of Motor Vehicles

The paper presents the results of numerical simulation and design of an automotive driving simulator for training drivers of motor vehicles, which includes a six-stage dynamic mobility platform and an integrated system of virtual 3D models of real terrain using the software and hardware system “Route”. On the basis of the developed mathematical model of the dynamic platform, optimization of geometric parameters was performed, various configurations of the plat-form were analysed. Optimization was performed using the PSO (Particle Swarm Optimization) heuristic algorithm. A digital twin of the platform has been developed in the MSC Adams (Automated Dynamic Analysis of Mechanical Systems) software package. The resulting digital twin has the properties of complete identity with the real prototype. A prototype of an automotive driving simulator is presented, which is equipped with a system of virtual 3D models of real terrain. The results of mathematical modelling, as well as experimental studies of the prototype are presented, which made it possible to evaluate its capabilities and characteristics.

Modeling and driving function optimization of tree climbing robot

To ensure the tree-climbing robot can complete the up-tree or down-tree process, its arms need to adjust the displacement of the push rod in real-time according to the diameter size of the tree trunk so that the tire can smoothly bypass the smaller tree pile. However, the irregular shape of the trunk surface makes the inflatable tire vibrate during rolling, which will reversely affect the performance of the push rod. Based on this, the three-dimensional model of the tree-climbing robot is established by Solid Works software, and the kinematics simulation model of the tree-climbing robot is established by Automatic Dynamic Analysis of Mechanical Systems (ADAMS). The kinematics simulation analysis is carried out. According to the tire displacement curve of the tree-climbing robot, the optimal solution of the push rod driving function is solved. Under the condition of ensuring the trajectory of the spiral rise is unchanged, the mean square deviation of the distance between the two arms of the tree-climbing robot is the smallest, and the push rod is the least affected by the reverse effect of the tire. The simulation results show that under the condition of the optimal solution, the frequency distribution and amplitude of the four springs are basically the same. The force of the four springs is uniform, and the reverse influence of the tires on the two push rods is minimized, which is conducive to the improvement of the stability of the tree climbing robot.

Design and Research of a Novel Piezostack-Driven Jetting Dispenser With a Diamond Spring

A novel piezoelectric jetting dispenser is proposed for microelectronic packaging in this article. It adopts a piezoelectric drive, a lever displacement amplifier, and a recovery system with double springs in a staggered position. The automatic dynamic analysis of mechanical systems (ADAMSs) simulation model of the dispenser is established and first applied to the study of the high-frequency response performance. The displacement curve and the velocity curve of the impactor are obtained at the frequency of 200 and 500 Hz. The test results prove that the ADAMS model is feasible. Based on dispensing experiments, the volume and the volume error of a drop at different dispensing frequencies are studied. The volume of a drop is 8.5 nL at the frequency of 800 Hz. The maximum relative error of the droplet volume is less than ±7.2% at the frequency of 200, 300, and 400 Hz.

Design and Research of a Harvesting Actuator for Camellia oleifera Flowers during the Budding Period

The collection of Camellia oleifera flowers is a key foundation of Camellia oleifera flower pollen extraction. Due to the current problems of low efficiency, high labor intensity and the high cost of manual collection of Camellia oleifera flowers, a harvesting actuator was designed. By analyzing the inherent characteristics of the Camellia oleifera flower and the harvesting method, a harvesting structure using a combination of friction roller twisting harvesting and pipeline pneumatic conveying was designed. The geometric model of the Camellia oleifera flower was established and the motion analysis of the flower was carried out, which indicated that the Camellia oleifera flower would tend to a stable state for easy picking after entering the actuator. Using Automatic Dynamic Analysis of Mechanical Systems 2015 software (ADAMS, MSC. Software Corporation, Santa Ana, CA, USA) to simulate the process of Camellia oleifera flower picking, a mechanical analysis was performed in the contact plane to prove the theoretical feasibility of friction roller picking these flowers, and the main influencing factor was obtained as the speed of the friction roller. The test prototype for Camellia oleifera flower picking was built, and the picking experiment was implemented to study the effect of motor speed on the picking time of single Camellia oleifera flowers and the effect of the success rate of the flower picking. The test results show that when the motor speed is 400 r/min, the picking success rate is 96%, the picking time of a single flower is 1.2 s, and the speed of the machine collection of Camellia oleifera flowers is 2.3 times that of manual collection, which proves the realistic feasibility of this picking actuator. This paper provides an important reference and basis for the research and development of a flower harvesting actuator.

Construction and Simulation of Biomechanical Model of Human Hip Joint Muscle-Tendon Assisted by Elastic External Tendon by Hill Muscle Model.

Based on the Hill muscle model (HMM), a biomechanical model of human hip muscle tendon assisted by elastic external tendon (EET) was preliminarily established to investigate and analyze the biomechanical transition between the hip joint (HJ) and related muscle tendons. Using the HMM, the optimal muscle fiber length and muscle force scaling variables were introduced by means of constrained optimization problems and were optimized. The optimized HMM was constructed with human parameters of 170 cm and 70 kg. The biomechanical model simulation test of the hip muscle tendon was performed in the automatic dynamic analysis of mechanical systems (ADAMS) software to analyze and optimize the changes in the root mean square error (RMSE), biological moment, muscle moment distribution coefficient (MDC), muscle moment, muscle force, muscle power, and mechanical work of the activation curves of the hip major muscle, iliopsoas muscle, rectus femoris muscle, and hamstring muscle under analyzing the optimized HMM and under different EET auxiliary stiffnesses from the joint moment level, joint level, and muscle level, respectively. It was found that the trends of the output joint moment of the optimized HMM and the biological moment of the human HJ were basically the same, r2 = 0.883 and RMSE = 0.18 Nm/kg, and the average metabolizable energy consumption of the HJ was (243.77 ± 1.59) J. In the range of 35%∼65% of gait cycle (GC), the auxiliary moment showed a significant downward trend with the increase of EET stiffness, when the EET stiffness of the human body was less than 200 Nm/rad, the biological moment of the human HJ gradually decreased with the increase of EET stiffness, and the MDC of the iliopsoas and hamstring muscles gradually decreased; when the EET stiffness was greater than 200 Nm/rad, the increase of the total moment of the extensor muscles significantly increased, the MDC of the gluteus maximus and rectus muscles gradually increased, and the gluteus maximus and hamstring muscle moments and muscle forces gradually increased; the results show that the optimized muscle model based on Hill can reflect the law of human movement and complete the simulation test of HJ movements, which provides a new idea for the analysis of energy migration in the musculoskeletal system of the lower limb.

Dynamic Performance Analysis of Cage in Four-Point Contact Ball Bearing

Due to the special structure of double-half inner rings, four-point contact ball bearings are prone to uneven forces in the inner raceway during movement, which affects the dynamic performance of the rolling element and cage, and even leads to cage sliding. Dynamic performance of the cage is an important factor affecting the working stability of bearings. In this paper, in order to grasp the operation law of the cage so as to guide the application of four-point contact ball bearings, the dynamic model of four-point contact ball bearings is established by the secondary development of Automatic Dynamic Analysis of Mechanical Systems (ADAMS). The dynamic performance of the cage is analyzed and evaluated with the indexes of vortex radius ratio and vortex velocity deviation ratio of the cage centroid trajectory. The results show the following: the cage stability increases and then decreases to a certain degree with rotating speed-rise; it increases and then decreases with the increase in the pure axial load; under a combination of axial and radial load, the cage moves more smoothly with smaller radial force. Rotating speed has little effect on cage stability, while radial force has a great influence on cage stability, followed by axial load. In order to verify the simulation results, a test bench for rolling bearing cages is developed, and the accuracy of the simulation results is verified by the test results.

Kinematics and dynamics simulations of cold orbital forging machines based on ADAMS

The vibration of cold orbital forging (COF) machines is detrimental to the quality of the forged part. Therefore, it is necessary to carry out kinematics and dynamics analyses, study the vibration of the COF machine, and provide effective methods for reducing the vibration. In terms of kinematics and dynamics analyses, the mathematical modeling and model solving processes are complicated, and it takes a long time to obtain the kinetic and vibration performances of the COF machine. In this study, the kinematics and dynamics models of the COF machine were investigated. Subsequently, automatic dynamic analysis of mechanical systems (ADAMS) was applied to conduct kinematics and dynamics simulations. The simulation process was convenient and time-saving, and the simulation of the COF machine was effectively verified by conducting an experiment. Based on the simulation results, the kinetic and vibration performances of the COF machine were studied. In addition, a structure optimization method for the COF machine is proposed. Based on the singularity stability theory, the Hopf bifurcation and chaos phenomena are less likely to occur on the optimized COF machine, and therefore the vibration of the optimized COF machine is stable. Meanwhile, the structure optimization method was proven to be effective in reducing the vibration of the COF machine, which improves the quality of the forged part.

Simulation Technology Development for Dynamic Analysis of Mechanical System in Deep-Seabed Integrated Mining System Using Multibody Dynamics

The deep-seabed mining system for mining resources consists of a mining vessel, lifting riser, lifting pump, buffer system, flexible riser, and mining robot. Because this system is exposed to extreme environments such as fluid resistance, high water pressure, and deep water, a considerable amount of time and cost is consumed in the design and test evaluation of equipment. To tackle these problems, the deep-seabed mining system in an extreme environment requires simulation-based technology. In particular, due to the large movement caused by marine energy, vibration caused by the operation of the mechanical system, and driving resistance of mining robot by the subsea soft soil, it is very important in the mining system design to analyze the dynamic effects of the various elements that constitute the deep-seabed mining system in a single integrated environment. This paper introduces the development of an integrated dynamic simulation method for deep-seabed mining systems and discusses the results.

Design and testing of a crop growth sensor aboard a fixed-wing unmanned aerial vehicle

• A set of crop growth sensors mounted on a fixed-wing UAV were developed. The system can obtain crop canopies and growth indices, such as LNC and LAI, on-line and in a convenient, high-throughput manner while ensuring that theUAV's airflow does not disturb the crop canopies below. • Flight dynamics computer simulation analysis of the fixed-wing UAV was conducted by the ADAMS software to obtain the deflection angle of the UAV during flight. A ball rolling-type sensor support was designed to ensure that the crop growth sensor is always aimed vertically downwards in-flight. • Due to the adjustment of the sensor support, the system has good dynamic stability and measurement accuracy within the working height range of the sensor. The aim of this study is to overcome disturbance of downwash flow field caused by the low-altitude operation of a multirotor unmanned aerial vehicle (UAV) on crop canopies and interference in spectral reflection information of canopies. For this purpose, a crop growth sensor aboard a fixed-wing UAV was developed through flight dynamics simulation analysis of a fixed-wing UAV. This sensor can collect index data on-line and in real-time including: the ratio vegetation index (RVI) of crop leaves, leaf area index (LAI), leaf dry weight (LDW), and leaf nitrogen content (LNC). Flight dynamics simulation analysis of the fixed-wing UAV was conducted by the automatics dynamic analysis of mechanical system (ADAMS) software to obtain the deflection angle of the UAV during flight. According to the flight characteristics and load on the UAV, a ball rolling-type sensor support was designed to ensure that the crop growth sensor is always aimed vertically downwards in-flight. The field test results show that the crop growth sensor aboard the fixed-wing UAV has good dynamic stability and high measurement accuracy. The RVIs measured by the onboard crop growth sensor in the plots and field were fitted with the results measured by a FieldSpec HandHeld 2 spectroradiometer (ASD, Analytical Spectral Device Co., USA). By analysing the fitted results, the coefficients of determination ( R 2 ) are 0.763 and 0.833 and the root mean square errors (RMSEs) are 0.16 and 0.17, respectively. By linearly fitting RVIs measured by the UAV with rice growth indices including LAI, LDW, and LNC, the coefficients of determination ( R 2 ) are 0.633, 0.581, and 0.528 and RMSEs are 0.18, 0.18, and 0.21, respectively.

Kinematics analysis and gait planning for a hemiplegic exoskeleton robot

Background: As the world's aging population increases, the number of hemiplegic patients is increasing year by year. At present, in many countries with low medical level, there are not enough rehabilitation specialists. Due to the different condition of patients, the current rehabilitation training system cannot be applied to all patients. so that patients with hemiplegia cannot get effective rehabilitation training. Methods: Through a motion capture experiment, the mechanical design of the hip joint, knee joint and ankle joint was rationally optimized based on the movement data. Through the kinematic analysis of each joint of the hemiplegic exoskeleton robot, the kinematic relationship of each joint mechanism was obtained, and the kinematics analysis of the exoskeleton robot was performed using the Denavit-Hartenberg (D-H) method. The kinematics simulation of the robot was carried out in automatic dynamic analysis of mechanical systems (ADAMS), and the theoretical calculation results were compared with the simulation results to verify the correctness of the kinematics relationship. According to the exoskeleton kinematics model, a mirror teaching method of gait planning was proposed, allowing the affected leg to imitate the movement of the healthy leg with the help of an exoskeleton robot. Conclusions: A new hemiplegic exoskeleton robot designed by Shenzhen Institute of Advanced Technology (SIAT-H) is proposed, which is lightweight, modular and anthropomorphic. The kinematics of the robot have been analyzed, and a mirror training gait is proposed to enable the patient to form a natural walking posture. Finally, the wearable walking experiment further proves the feasibility of the structure and gait planning of the hemiplegic exoskeleton robot.

Bionic design and analysis of a multi-posture wheelchair

Abstract. Posture transformation is an essential function for multi-posture wheelchairs. To improve the natural motion in posture transformation that is a popular problem in the design of multi-posture wheelchairs because the current wheelchair's posture transformation mechanism cannot remain consistent between the rotation center of the wheelchair and the rotation center of the human body joints. This paper proposes a sitting–standing–lying three-posture bionic transformation mechanism for a smart wheelchair. A human–wheelchair coupling model is described and analyzed according to the biomechanical characteristics of the posture transformation of human beings and their functional requirements. The configuration of the transformation mechanism is chosen by comparing the trails of the wheelchair rotation centers and the corresponding human joint rotation centers. The kinematics of the optimized configuration are discussed in detail to obtain the most bionic motion performance using the multivariable nonlinear constraint optimization algorithm. Finally, the mechanism is designed, and its posture transformation performance is simulated and verified using Adams (Automatic Dynamic Analysis of Mechanical Systems) software.