Dynamic Analysis Of Mechanical Systems Research Articles

Motion Analysis of the Hydraulic Ladder

This paper is aimed at a dynamic analysis of a hydraulically lifted ladder by means of analytical and numerical calculations. The solutions used in the dynamic analysis of mechanical systems were used in the analytical solution. A numerical model was created to verify the achieved results of the solved mechanical system with simulation of its motion.

Design and Analysis of a Swashplate Control System for an Asymmetric Axial Piston Pump

Abstract Based on the previously developed fixed-displacement asymmetric axial piston pump, a variable displacement asymmetric axial piston pump (VDAAPP) with three independent suction/delivery ports is proposed. A basic linear model of VDAAPP is established to get open-loop bode diagram. Based on open-loop Bode diagram features and design requirements, P-controller is determined for VDAAPP. Then VDAAPP's performance is investigated by advanced modeling environment for performing simulations of engineering systems (AMESim) and automatic dynamic analysis of mechanical systems (ADAMS) joint simulation, and some key design parameters are obtained. Next, a VDAAPP prototype with a maximum displacement of 40 cc/rev is designed and manufactured, ratio of flow rates at ports A, B and T is 1:0.6:0.4. Due to hard limitations of the test bench, the performance only under the conditions of the opposite passive loads is tested. Preliminary test results indicate that VDAAPP prototype works normally and meets the design requirements for flow ratio, and the maximum rise time of the test pressure is about 0.32 s. However, due to special design of VDAAPP valve plate, the swash plate torque severely limits system dynamic response. Therefore, an improved swashplate control system based on asymmetric-valve-controlled asymmetric-piston scheme is presented as well, it is found to be an effective way to suppress the negative impact of swash plate torque on system dynamic performance. This provides a direction for the optimization of the swashplate control system for asymmetric axial piston pumps in the future.

Analysis and Verification of Finite Time Servo System Control with PSO Identification for Electric Servo System

Electric servo system (ESS) is a servo mechanism in a control system of an aircraft, a ship, etc., which controls efficiency and directly affects the energy consumption and the dynamic characteristics of the system. However, the control performance of the ESS is affected by uncertainties such as friction, clearance, and component aging. In order to improve the control performance of the ESS, a control technology combining particle swarm optimization (PSO) and finite time servo system control (FTSSC) was introduced into ESS. In fact, it is difficult to know the uncertain physical parameters of the real ESS. In this paper, the genetic algorithm (GA) was introduced into PSO and the inertia weight was improved, which increased the parameter optimization precision and convergence speed. A new feedback controller is proposed to improve response speed and reduce errors by using FTSSC theory. The performance of the controller based on PSO identification algorithm was verified by co-simulation experiments based on Automatic Dynamic Analysis of Mechanical Systems (ADAMS) (MSC software, Los Angeles, CA, USA) and matrix laboratory (MATLAB)/Simulink (MathWorks, Natick, MA, USA). Meanwhile, the proposed strategy was validated on the servo test platform in the laboratory. Compared with the existing control strategy, the control error was reduced by 75% and the steady-state accuracy was increased by at least 50%.

Research on innovative design of a new rope knotter

Aiming at the complex structure and high manufacturing process requirements of traditional knotter, this article proposes a new rope knotting method. Based on the knotting method, a knotter is designed to use a new mechanism which is made up of two new incomplete gear mechanisms to drive rope clamping mechanism and rope hooking and griping mechanism. First, a kinematic cycle diagram of the knotter is determined, and the structures of each key mechanism are designed. Then, a virtual prototype of the knotter is established by Unigraphics and imported into Automated Dynamic Analysis of Mechanical Systems to analyze the kinematic of each key mechanism. The success rate is 98.4% through 500 physical tests on the physical model of the knotter. The results indicate that the knotting method is reliable. The knotter can meet the requirements of structure, posture, and coordination during knotting process. The new knotter has no separate mechanism for cutting rope and tripping out of the rope buckle. Therefore, the structure is simplified and reduces the design and manufacturing difficulties. Furthermore, the new incomplete gear mechanism solves the problem that in the conventional incomplete gear mechanism, the driven gear can swing at a large angle or even cannot be locked in the case when the locking arc of the passive gear is too short.

Optimal Feet-Forces’ and Torque Distributions of Six-Legged Robot Maneuvering on Various Terrains

SUMMARYAn analytical model with coupled dynamics for a realistic six-legged robotic system locomoting on various terrains has been developed, and its effectiveness has been proven through computer simulations and validated using virtual prototyping tools and real experiment. The approach is new and has not been attempted before. This study investigated the optimal feet-forces’ distributions under body force and foot–ground interaction considering compliant contact and friction force models for the feet undergoing slip. The kinematic model with 114 implicit constraints in 3D Cartesian space has been transformed in terms of generalized coordinates with a reduced explicit set of 24 constrained equations using kinematic transformations. The nonlinear constrained inverse dynamics model of the system has been formulated as a coupled dynamical problem using Newton–Euler method with realistic environmental conditions (compliant foot–ground contact, impact, and friction) and computed using optimization techniques due to its indeterminate nature. One case study has been carried out to validate the analytical data with the simulated ones executed in MSC.ADAMS® (Automated Dynamic Analysis of Mechanical Systems), while the other case study has been conducted to validate the analytical and simulated data with the experimental ones. In both these cases, results are found to be in close agreement, which proves the efficacy of the model.

Investigation on multi-body dynamics based approach to the toolpath generation for ultraprecision machining of freeform surfaces

This article presents an innovative approach to toolpath generation for ultraprecision machining of freeform optic surfaces based on the principle of Automatic Dynamics Analysis of Mechanical Systems. As components with freeform surfaces often have non-rotational symmetry, there are potential challenges facing their ultraprecision machining through single-point diamond turning, such as the projected points in complex large sag surfaces, which likely find it difficult to communicate with the control system and, thus, do not perform successfully. In ultraprecision machining, to achieve the highest performance in freeform surface resolution, the factors of dynamics, material and mechanical stiffness, frictions, tooling and accuracy of the servo component should be considered. The investigation is focused on an integrated approach and the associated scientific understanding of precision engineering design, ultraprecision machining and metrology of freeform surfaces as well as their application perspective. In this approach, the toolpath for very complex freeform surfaces can be generated using the Newton–Raphson method to solve the kinematics and dynamics equations of motion. The effect of friction and contact force are also investigated for accurate toolpath curve generation. Moreover, the Gear stiff (GSTIFF)/ Wielenga stiff (WSTIFF) integrator for solving the non-linear equations of motion is employed, and the result shows the time step size, playing a critical role in generating toolpath curves with a higher accuracy and resolution.

Structural model and dynamic analysis of six-axis Cartesian coordinate robot for sheet metal bending

Bending is an important procedure for processing sheet metals, while it is a key link in the realization of automatic processing of sheet metal. To improve the efficiency and accuracy of bending processing, this article proposed a structure model and a prototype of a six-axis Cartesian coordinate robot for sheet metal bending to replace workers completing automatic bending processes. Based on the analysis of overall structure schemes of the robot, kinematic simulation is conducted by using the automatic dynamic analysis of mechanical system (ADAMS). Furthermore, the dynamic performance of the structural model of the robot for sheet metal bending is analysed and design optimization is performed. A prototype of the robot based on the optimal structural model of six-axis Cartesian coordinate robot for sheet metal bending is made. Finally, under the work conditions, the efficiencies and accuracies of sheet metal bending by a worker and the robot are compared and tested. The structural model of six-axis Cartesian coordinate robot for sheet metal bending presented in this article is found to be applicable to sheet metal bending robot and improves the stability of sheet metal bending machine. The laboratory testing and experimental results verified the feasibility of the proposed robot.

Kinetic Simulation of Lifting Mechanism of Personnel Airlock in Nuclear Power Plants

In order to ensure the rationality of the structural design for personnel airlock lifting mechanism in nuclear power plants, the dynamic characteristics of the sealing door during the opening and closing process are analyzed. This paper adopts Automatic Dynamic Analysis of Mechanical Systems(ADAMS) software to analyze the airlock dynamics and kinematic performance, including the kinematic simulation of the driving box and the dynamic simulation of the transmission screw. The analysis indicates that the initial installation position of the driving box in the lifting mechanism is the key factor leading to the insufficiency of lifting height. By resetting the initial installation position of the driving box and revolving the velocity and runtime of the screw, the lifting height can meet the design requirement (60mm). Also, the dynamic simulation results of the screw show that the radial force imposed on the screw can be neglected, which would not cause the rupture of the screw.

Characteristic parameter change of circuit breaker under closing spring fatigue

Closing spring fatigue faults of high voltage circuit breakers affect the timing parameters in closing operations and reduce the closing performance of the circuit breaker. Traditional tests of timing parameter based on travel curve cannot be applied online, and sensor installation is complicated. In this paper, a new method to extract key circuit breaker timing parameters from the vibration signal under closing spring fatigue fault is proposed. First, the travel curve of the circuit breaker under closing spring fatigue is simulated in Automatic Dynamic Analysis of Mechanical Systems (ADAMS). Results indicate that the time intervals between key points of the travel curve can be used as fault features. Then, according to the working principle of the circuit breaker’s spring operating mechanism, the vibration event caused by component impact in the closing operation is analyzed. The corresponding timing parameters are extracted from the vibration signal using the double threshold method based on the short-time energy to entropy ratio. Finally, comparison of experimental measurements with ADAMS simulation results and vibration extraction provides the change law of the fault feature. The correctness of the proposed method is verified. This paper presents a new method for online monitoring of circuit breaker closing spring fatigue.

Design and simulation of an integrated end-effector for picking kiwifruit by robot

The harvesting of fresh kiwifruit is a labor-intensive operation that accounts for more than 25% of annual production costs. Mechanized harvesting technologies are thus being developed to reduce labor requirements for harvesting kiwifruit. To improve the efficiency of a harvesting robot for picking kiwifruit, we designed an end-effector, which we report herein along with the results of tests to verify its operation. By using the established method of automated picking discussed in the literature and which is based on the characteristics of kiwifruit, we propose an automated method to pick kiwifruit that consists of separating the fruit from its stem on the tree. This method is experimentally verified by using it to pick clustered kiwifruit in a scaffolding canopy cultivation. In the experiment, the end-effector approaches a fruit from below and then envelops and grabs it with two bionic fingers. The fingers are then bent to separate the fruit from its stem. The grabbing, picking, and unloading processes are integrated, with automated picking and unloading performed using a connecting rod linkage following a trajectory model. The trajectory was analyzed and validated by using a simulation implemented in the software Automatic Dynamic Analysis of Mechanical Systems (ADAMS). In addition, a prototype of an end-effector was constructed, and its bionic fingers were equipped with fiber sensors to detect the best position for grabbing the kiwifruit and pressure sensors to ensure that the damage threshold was respected while picking. Tolerances for size and shape were incorporated by following a trajectory groove from grabbing and picking to unloading. The end-effector separates clustered kiwifruit and automatically grabs individual fruits. It takes on average 4–5 s to pick a single fruit, with a successful picking rate of 94.2% in an orchard test featuring 240 samples. This study shows the grabbing–picking–unloading robotic end-effector has significant potential to facilitate the harvesting of kiwifruit.

Effects of Connection Type between Surface Vessel and Submersible Propeller on Motion Performance of Wave Glider

Wave Glider is an autonomous surface vehicle that directly uses wave energy to generate forward power and has been widely used in marine survey and observation. Wave Glider is composed of surface vessel, submersible propeller and the connection structure between them. Connection types are thought to be related to the performance of Wave Glider closely. In this paper, the effects of the connection structure between the surface vessel and the submersible propeller on the motion performance of the Wave Glider are studied. Several connection types such as rigid rod, cable, multi-link chain and elastic rod are applied to connect the surface vessel and the submersible propeller. The models of connection structures are developed respectively. Among them, cable model is established with a finite number of small cylinders, which connected by spring and damping elements; multi-link chain can be seen as hinged by multiple rigid rods; elastic rod model can be looked on as several segments linked with elastic components. Considering the connection characteristics, the integrated dynamic models are established by applying multi-body dynamics software ADAMS (Automatic Dynamic Analysis of Mechanical Systems) with consideration of the hydrodynamic forces on different components of Wave Glider. The propulsion performance of the Wave Glider is calculated by using numerical method, and the simulation results showed that the difference of propulsion performance with different connection types of the Wave Glider is slightly. But serious impacts can occur on the connections of rigid rod and multi-link chain. They can lead to serious extra load on the structure of Wave Glider. From the engineering practice of Wave Glider application, the cable connection is more convenient to transport, deploy, recover and store. It is also the generous connection type for wave glider.

Modeling and co‐simulation based on Adams and AMESim of pivot steering system

The pivotal steering ability of vehicles is important in the case of narrow steering space. In this study, a pivot steering system for the rescue vehicle is designed, and the 1D + 3D co-simulation model is established based on automatic dynamic analysis of mechanical systems (Adams) and advanced modelling environment for performing simulation of engineering systems (AMESim). The dynamic analysis of the pivot steering system has been compared with the theoretical calculations, which proved the correction of the model. In addition, through the simulation, the authors can hold the conclusion that the tyre cornering stiffness has a great influence on the pivot steering system.

Implementation of a ball inverted pendulum with omnidirectional moving ability using a robust fuzzy control strategy

A robust fuzzy controller (RFC) is proposed for a ball inverted pendulum (BIP) system control problem. A Mamdani-type fuzzy controller and a compensated control technique are combined in the proposed control system. This controller is used for real-world control of a BIP with unknown system uncertainties. Using this method, the approximation error caused by the trial-and-error fuzzy control design procedure is minimized. Moreover, the decoupled technique provides a simple method for achieving asymptotic stability control for angle and position of a BIP control system. The concept of this approach is to decouple the entire system into two subsystems. Next, the primary subsystem combines the information provided by the secondary subsystem. And then a control force is generated to drive both subsystems toward their targets, respectively. Thus, the platform can move to any position without constraints. The stability of RFC, which is based on the Lyapunov stability theorem, is guaranteed. Furthermore, to verify the effectiveness of the control algorithm, several numerical simulations and dynamic simulation in the automatic dynamic analysis of mechanical systems (ADAMS) environment with MATLAB are implemented. Finally, the efficiency of the RFC is verified with real-time implementation of the BIP.

A model-free control method for estimating the joint angles of the knee exoskeleton

This article describes a model-free adaptive control method for knee joint exoskeleton, which avoids the complexity of human–exoskeleton modeling. An important feature of the proposed controller is that it uses the input and output data of the knee joint angle to control the exoskeleton. Furthermore, discrete sliding mode control law and prior torque are introduced to improve the accuracy and robustness of the system. Prior torque of knee joint is obtained through the walking simulation of human–exoskeleton modeling. Specially, the experiment is carried out by using the co-simulation automatic dynamic analysis of mechanical systems and MATLAB. Data from these assessments indicate that the proposed strategy enables the knee exoskeleton to track the trajectory of angle well and has a good performance on walking assistance.

Analysis influence of journal radius and length of bearing on dynamics of a slider-crank mechanism with two sliders and revolute clearance joints

This article investigates influence of clearances, journal radius and length of bearing on the dynamic response of a slider-crank mechanism with two sliders and imperfect revolute joints in dry contacting condition. The mechanism was designed by Solid Works and analyzed by finite element method in ANSYS. The simulation results revealed that the velocity of two sliders were oscillated and acceleration of two sliders were obvious shaky with high peaks comparing with the ideal joint when clearance size is equal to 0.3 mm and at different length of bearing and journal radius. This reasons are due to a suddenly increase of contact force when the journal impacts into the bearing in imperfect revolute joints. It demonstrated that clearance, length of bearing and journal radius play an important role in dynamics analysis of mechanical systems.

Modeling and analysis of friction including rolling effects in multibody dynamics: a review

Friction exists in most mechanical systems, and it can have a major influence on their dynamic performance and operating conditions. As a consequence of frictional contact phenomena, energy is dissipated and the state of a system can change slowly and rapidly, depending on the nature of the contact, continuous or impact condition. Other effects associated with friction in mechanical systems are the vibration and noise propagation of the system components, nonlinear systems’ behavior and wear. Overall, the knowledge of the friction regimen, as well as the frictional forces developed at the interface of mechanical parts in contact with relative motion, is crucial for the dynamic analysis of mechanical systems, and has consequences in the design process. Thus, this work is a review of the modeling and analysis of frictional effects in multibody systems with the purpose of better understanding and obtaining accurate responses. In this process, pure dry sliding friction, stick–slip effect, viscous friction, Stribeck effect, and frictional lag are some of the main phenomena associated with friction, which are addressed in depth. Overall, the friction models can be divided into two main groups, namely the “static friction models” and the “dynamic friction models”. The static models describe the steady-state behavior of the relation friction-force/relative-velocity, while the dynamic models allow for the capturing of more physical responses and properties by using extra state variables. In a simpler manner, the static and dynamic friction models differ mostly in the modeled frictional effects, implementation complexity, and computational efficiency. Hence, this research is aimed at analyzing in detail the role of friction modeling in the dynamic response of multibody system, as well as addressing the importance of friction models selection for accurately describing the friction related phenomena. Demonstrative application examples, which include friction in ideal mechanical joints and systems involving contact–impact events, including an example of rolling contact will be considered and investigated to illustrate the main assumptions and procedures adopted in this work. The results from this study indicate that in most cases, a static friction model, which accounts for static friction and avoids the discontinuity at zero velocity, is a suitable choice. A more advanced dynamic friction model has to be developed to be utilized for systems containing high variations of normal load, namely with impact conditions.

A Comparative Study of Four Kinds of Adaptive Decomposition Algorithms and Their Applications

The adaptive decomposition algorithm is a powerful tool for signal analysis, because it can decompose signals into several narrow-band components, which is advantageous to quantitatively evaluate signal characteristics. In this paper, we present a comparative study of four kinds of adaptive decomposition algorithms, including some algorithms deriving from empirical mode decomposition (EMD), empirical wavelet transform (EWT), variational mode decomposition (VMD) and Vold–Kalman filter order tracking (VKF_OT). Their principles, advantages and disadvantages, and improvements and applications to signal analyses in dynamic analysis of mechanical system and machinery fault diagnosis are showed. Examples are provided to illustrate important influence performance factors and improvements of these algorithms. Finally, we summarize applicable scopes, inapplicable scopes and some further works of these methods in respect of precise filters and rough filters. It is hoped that the paper can provide a valuable reference for application and improvement of these methods in signal processing.

Effects of material characteristics and clearance size on dynamics of a slider-crank mechanism with two sliders and revolute clearance joints

This article presents influences of clearance size and material parameters on the dynamic response of a slider-crank mechanism with imperfect revolute joints in dry contacting condition. The mechanism was created by Solidworks and a finite element method in ANSYS software was used to analyze the effects which presented and discussed. The simulation results revealed that the acceleration of two sliders was obviously shaking with high peaks when the clearance size equal to 0.3 mm which differ from the ideal joint. Moreover, the smaller Young’s modulus material of journals indicated the significant effects on acceleration of mechanical systems. The reasons are due to a suddenly increase of contact force when the journal impacted into the bearing in imperfect revolute joints. The simulation results for the clearance size equal to 0.1 mm, 0.2 mm and 0.4 mm were close to an ideal joint. It demonstrated that clearance size and material characteristic played an important role in dynamics analysis of mechanical systems.

Design Optimization of Steering Mechanisms for Articulated Off-Road Vehicles Based on Genetic Algorithms

Two cylinders arranged symmetrically on a frame have become a major form of steering mechanism for articulated off-road vehicles (AORVs). However, the differences of stroke and arm lead to pressure fluctuation, vibration noise, and a waste of torque. In this paper, the differences of stroke and arm are reduced based on a genetic algorithm (GA). First, the mathematical model of the steering mechanism is put forward. Then, the difference of stroke and arm are optimized using a GA. Finally, a FW50GLwheel loader is used as an example to demonstrate the proposed GA-based optimization method, and its effectiveness is verified by means of automatic dynamic analysis of mechanical systems (ADAMS). The stroke difference of the steering hydraulic cylinders was reduced by 92% and the arm difference reached a decrease of 78% through GA optimization, in comparison with unoptimized structures. The simulation result shows that the steering mechanism optimized by GA behaved better than by previous methods.

Dinamička analiza mehanizma kretanja stubne dizalice

It is offered the new approach to complex dynamic analysis of mechanical systems with use of a certain set of modern computer systems. This approach provides high level of dynamic analysis of mechanical systems, including and presentation of received results. It is especially important at the earliest design stages of mechanical systems.