Dynamic Analysis Of Mechanical Systems Research Articles

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.

Design and development of 5-axis robot

Robotics has been developed to ease the works of human beings using assistive robots and robotic arms. This paper is provided with the design and development of such robotic arm. Since the robotic arm is an analogy of human arm, it consists of several rigid links connected and articulated using rotational joints. In this paper, the design and analysis of a simple 5-axis industrial robotic arm is brought forth. The foremost information on the actuators and other electrical components used in this robotic arm is presented. The angular velocity, angular acceleration, and torque at different joints have been calculated and analyzed with the help of the multibody dynamics simulation software ADAMS (Automated Dynamic Analysis of Mechanical Systems). This simulation assisted in determining the stability of the robot and in choosing the appropriate actuators.

Straw/Spring Teeth Interaction Analysis of Baler Picker in Smart Agriculture via an ADAMS-DEM Coupled Simulation Method

In this paper, a new coupling simulation method is proposed for baler picker using automatic dynamic analysis of mechanical systems (ADAMS) and discrete element method (DEM). Field tests are carried out to verify the accuracy of the simulation model. By using the coupling method, not only was it obtained that the forward velocity (FV) and the ground clearance of spring teeth (GCST) are positively correlated with the pick-up loss rate (PLR), but also that the blockage of the picker mainly occurs in the straw pushing area, and an optimization plan is proposed. Through the analysis of the acting force (AF) between the roller and the track groove, we speculate that the structure of the track groove in a certain area is defective. The coupling method and optimization scheme proposed in this paper can provide a reference for the optimal design of the picker.

Performance analysis of a spring-tooth drum pickup of straw baler via coupling simulation

In order to solve the problem of poor working performance due to incidental picking-up loss of a spring-tooth drum pickup, the coupling analysis approach of Automated Dynamic Analysis of Mechanical Systems (ADAMS) and Discrete Element Method (DEM) was proposed to reveal its motion characteristics. The coupled ADAMS-DEM method was used to construct the pickup simulation model with rice straw as the object. The validation tests were carried out in the field with different operating forward speeds and straw coverages. The results showed that when the baler worked with a rake, the straw loss rate tended to rise with the increase of the operating speed and the straw coverage. Tests results indicated periodic peaks and valleys of the forces between the rollers and the track chute, which could increase the wear of the track chute. In addition, the movement and variation of the straw and the distribution of different straw lengths after picking up were analyzed. The research results can provide a reference for the design and optimization of a pickup in the later period. Keywords: ADAMS-DEM coupling, loss rate, pickup, straw coverage, straw baler DOI: 10.25165/j.ijabe.20211404.6576 Citation: Wang Q Q, Jiang Y C, Li L H, Qin J W, Chen L Q. Performance analysis of a spring-tooth drum pickup of straw baler via coupling simulation. Int J Agric & Biol Eng, 2021; 14(4): 159–165.

Variable universe fuzzy control of the lateral stability of forklift trucks based on roll grading

Based on the structural analysis and the roll mechanisms of counterbalanced forklift truck, a novel type of 3-link hydraulic supporting mechanism is designed as an actuator for forklift anti-rollover control. A rollover grading control strategy of the lateral stability of counterbalanced forklift truck is proposed, which is used to design a variable universe fuzzy controller. The variable universe fuzzy control of the first-order roll is utilized when the forklift is in the first-order roll, whereas the variable universe fuzzy control of the second-order is used when the forklift is in the second-order roll. A virtual prototype model of forklift is built in Automatic Dynamic Analysis of Mechanical Systems (ADAMS). The co-simulations and vehicle tests are implemented, the results indicate that the lateral stability and active security of the forklift could be improved effectively by using the variable universe fuzzy control strategy of the lateral stability of forklift truck based on roll grading.

Research on dynamics of bouncing ball in triboelectric nanogenerator

Bouncing ball based Triboelectric Nanogenerator (BB-TENG) can be used to harvest vibrational energy and sense signal for self-powered sensor in the non-resonant zone because of its non-spring vibration system. The energy harvesting efficiency and sensing effectiveness are significantly affected by the dynamics of the bouncing ball. However, due to the chaotic and nonlinear mechanics, the dynamics of the bouncing ball inside BB-TENG and the corresponding influencing factors have not yet been revealed, which restricts the development of high-efficiency BB-TENG. In this work a method based on dynamics simulation and test bench experiment is to be proposed and the ‘Takeoff’, ‘Well-Contact’, ‘Self-Spin’, and ‘Rich-Contact’ of the bouncing ball with the plate electrodes will be investigated. The kinetic model established based on the Automatic Dynamic Analysis of Mechanical Systems (ADAMSs) is verified through experiments to confirm the reliability of the simulation results. It is found that ‘Well-Contact’ of the bouncing ball makes BB-TENG harvest energy efficiently. The factors for ‘Well-Contact’ and their influence are investigated, and the critical frequencies for ‘Well-Contact’ of the bouncing ball at each vibration excitation amplitude are obtained. ‘Self-Spin’ of the bouncing ball produced by unbalanced excitation torque is found to increase energy harvesting, and the excitation frequency significantly determines the energy of the ‘Self-Spin’. When the external excitation acceleration reaches a critical value, the ‘Rich-Contact’ of the bouncing ball is found, and the amount of charge transfer for BB-TENG will not increase, which is termed saturated condition. Therefore, the results of this work help improve the design and application of high-efficiency BB-TENG.

Design and simulation research of the double-spin folding mechanism based on a suspended missile

Based on the suspension of a missile using folding rotary wings and airbags, in order to improve the basic parameters and motion characteristics of the rotor during the unfolding process and analyze the aerodynamic characteristics of the entire device in the suspension state, after proposing a scheme of double-spin mechanism, the main folding and unfolding mechanism, initial driving device, rotating driving device, and locking mechanism were designed, and the simulation research is studied by the Automatic Dynamic Analysis of Mechanical System and Ansys Fluent Fluid Simulation software, respectively. The results show that the rotation rate was controlled at 41.8 mm/s, the various motion parameters are reasonable, and the operation process is relatively smooth, with high reliability. The speed and pressure value at the tip of the rotor are higher and the aerodynamic disturbance is obvious, which has a great influence on the aerodynamic performance. The speed and pressure distribution of the surrounding flow field is stable, the lift provided is 46 N, and the lift coefficient is 0.55, which can ensure the long-time suspension state of the missile. This paper puts forward a valuable design idea and has practical reference value for the research of the suspended missile.

Optimal Design of High-Voltage Disconnecting Switch Drive System Based on ADAMS and Particle Swarm Optimization Algorithm

This paper focuses on the analysis of the stability of the GW17 high-voltage disconnecting switch drive system. Firstly, the optimization model of the disconnector is established, and the simulation analysis is carried out by ADAMS (Automatic Dynamic Analysis of Mechanical Systems) and the simulation results are verified by experiments. Afterwards, ADAMS optimization design and particle swarm optimization algorithm (PSO) are used to optimize the drive system of the disconnector, and the results are verified on the experimental platform. After optimization, the space rod is reduced by 15 mm, the minimum corner angle of the lower conductive rod is reduced by 71.0%, the minimum folding arm angle is reduced by 88.7% and the maximum force of the ball pair is reduced by 35.7%, which realizes the lightweight of the rod, reduces the wear of the ball pair, and improves the stability of the equipment operation.

Development of Subcarangiform Bionic Robotic Fish Propelled by Shape Memory Alloy Actuators

In this paper, a shape memory alloy (SMA) actuated subcarangiform robotic fish has been demonstrated using a spring based propulsion mechanism. The bionic robotic fish developed using SMA spring actuators and light weight 3D printed components can be employed for under water applications. The proposed SMA spring-based design without conventional motor and other rotary actuators was able to achieve two-way shape memory effect and has reproduced the subcarangiform locomotion pattern. The positional kinematic model has been developed and the dynamics of the proposed mechanism were analysed and simulated using Automated Dynamic Analysis of Mechanical Systems (ADAMS). An open loop Arduino-relay based switching control has been adopted to control the periodic actuation of the SMA spring mechanism. The undulation of caudal fin in air and water medium has been analysed. The caudal fin and posterior body of the developed fish prototype have taken part in undulation resembling subcarangiform locomotion pattern and steady swimming was achieved in water with a forward velocity of 24.5 mm/s. The proposed design is scalable, light weight and cost effective which may be suitable for underwater surveillance application.

Adaptive fuzzy backstepping control of underactuated multi-cable parallel suspension system with tension constraint

Multi-cable parallel suspension system (MCPSS) is designed to lift a heavy object with rapid development of deep resources exploitation. An adaptive fuzzy backstepping control strategy combining with nonlinear disturbance observer is studied to synthetically control the posture for the underactuated MCPSS with tension constraint in this article. Firstly, a theoretical modelling of the MCPSS with boundary constraints is derived by the extended Hamilton’s Principle. Secondly, the parameter uncertainties and time-varying disturbances are compensated by the fuzzy system and nonlinear disturbance observer, respectively. Thirdly, an adaptive fuzzy backstepping feedback controller based on the reference model is proposed to suppress vibration and control posture of the suspension platform. Finally, an Automatic Dynamic Analysis of Mechanical Systems (ADAMS) simulation and a numerical calculation are used to illustrate the theoretical model and the proposed control performance.

Performance analysis of a spring-tooth drum pickup of straw baler via coupling simulation

In order to solve the problem of poor working performance due to incidental picking-up loss of a spring-tooth drum pickup, the coupling analysis approach of Automated Dynamic Analysis of Mechanical Systems (ADAMS) and Discrete Element Method (DEM) was proposed to reveal its motion characteristics. The coupled ADAMS-DEM method was used to construct the pickup simulation model with rice straw as the object. The validation tests were carried out in the field with different operating forward speeds and straw coverages. The results showed that when the baler worked with a rake, the straw loss rate tended to rise with the increase of the operating speed and the straw coverage. Tests results indicated periodic peaks and valleys of the forces between the rollers and the track chute, which could increase the wear of the track chute. In addition, the movement and variation of the straw and the distribution of different straw lengths after picking up were analyzed. The research results can provide a reference for the design and optimization of a pickup in the later period. Keywords: ADAMS-DEM coupling, loss rate, pickup, straw coverage, straw baler DOI: 10.25165/j.ijabe.20211404.6576 Citation: Wang Q Q, Jiang Y C, Li L H, Qin J W, Chen L Q. Performance analysis of a spring-tooth drum pickup of straw baler via coupling simulation. Int J Agric & Biol Eng, 2021; 14(4): 159–165.

Type Synthesis and Dynamics Performance Evaluation of a Class of 5-DOF Redundantly Actuated Parallel Mechanisms

This paper presents a five degree of freedom (5-DOF) redundantly actuated parallel mechanism (PM) for the parallel machining head of a machine tool. A 5-DOF single kinematic chain is evolved into a secondary kinematic chain based on Lie group theory and a configuration evolution method. The evolutional chain and four 6-DOF kinematic chain SPS (S represents spherical joint and P represents prismatic joint) or UPS (U represents universal joint) can be combined into four classes of 5-DOF redundantly actuated parallel mechanisms. That SPS-(2UPR)R (R represents revolute joint) redundantly actuated parallel mechanism is selected and is applied to the parallel machining head of the machine tool. All formulas of the 4SPS-(2UPR)R mechanism are deduced. The dynamic model of the mechanism is shown to be correct by Matlab and automatic dynamic analysis of mechanical systems (ADAMS) under no-load conditions. The dynamic performance evaluation indexes including energy transmission efficiency and acceleration performance evaluation are analyzed. The results show that the 4SPS-(2UPR)R mechanism can be applied to a parallel machining head and have good dynamic performance.

Analysis on fatigue life of overhead travelling crane girder under impact load for sustainable transport system

As the main bearing structure of the crane, the girder structure determines its service life. While the girder structure meets the strength, stiffness, and stability, its fatigue life should be paid more attention. A strong impact will be caused by the overhead travelling crane running through the uneven track joint. Based on SolidWorks and automated dynamic analysis of mechanical systems, the virtual prototype of 480 t overhead travelling crane operation is established in this study. The operation simulation of various track height differences is carried out. Compared with the theoretical calculation of GB and ISO, the virtual prototype is verified. Through the strain test and finite-element calculation of stress of girder under the two working conditions including the main car with a load of 433 t running to the mid-span and span end of the girder, the stress concentration in the transition rounded corner of the girder is found. On the basis of the simulation load spectrum and finite-element static stress analysis, combined with the S–N curve of material, the fatigue damage and life prediction model of the 480 t overhead travelling crane girder is established. The minimum life of the dangerous part is obtained, providing a basis for the design and maintenance.

Modelling and analysis of a novel mechanical‐variable‐flux IPM machine with rotatable magnetic poles

In this study, a novel mechanical-variable-flux interior permanent magnet motor (MVF-IPMM) is presented, which employs rotatable magnetic poles and a mechanical flux-adjusting device placed on both sides of the rotor. The device can regulate the magnetic circuit by rotating magnetic poles and adjusting the angle of the magnetisation direction relative to the d-axis. Consequently, the flux-weakening capability is enhanced. The configuration and additional mechanical devices of the MVF-IPMM are introduced, respectively. Then, the operation principle and flux-adjusting mechanism are deeply investigated by using analytical models, whose parameters are computed by automatic dynamic analysis of mechanical system and finite-element analysis. Based on the simulation results, an electromechanical model is established to predict the performance of the motor. In addition, the electromagnetic characteristics of the mechanical-variable-flux- and conventional interior permanent magnet machines are compared. Finally, the effectiveness of the design is successfully proven by experimenting with a prototype.

Dynamic analysis of mechanical system considering radial and axial clearances in 3D revolute clearance joints

In the dynamic modeling and simulation of mechanical system with revolute clearance joint, it is usually assumed that the revolute joint is planar joint with radial clearance, but the axial clearance is ignored. In this article, the dynamic responses of a mechanical system considering both radial and axial clearances in 3D revolute clearance joint are investigated using a computational methodology. First, the mathematic model of 3D revolute clearance joint is established considering the radial and axial clearances. The definitions of the radial and axial clearances, the potential contact modes, contact conditions, and contact detection for 3D revolute clearance joint are presented. Furthermore, the normal and tangential contact force models are established to describe the contact phenomenon and determine the contact forces in revolute clearance joints. Finally, two demonstrative application examples are presented to illustrate the dynamic characteristics of mechanical systems considering both radial and axial clearances in revolute clearance joints. A slider-crank mechanism with planar motion and a double pendulum with spatial motion are investigated. Different cases are presented to analyze the dynamic characteristics of a mechanical system considering radial and axial clearances in 3D revolute clearance joints.

Influence of control device on store separation from an open cavity

The influence of a flow control device on store separation from an internal cavity is examined using a wind-tunnel drop-test (WTDT) method, which is based on dynamic similarity. In the wind-tunnel test, an open cavity with a length-to-depth ratio of R=7.76 is employed. An ejection mechanism driven using two cylinders is designed using the CATIA software and is virtually simulated using automatic dynamic analysis of mechanical systems (ADAMS). The store is designed using the light Mach scaling method. Conditions involving a cuboid control device (CCD) and no control device (NCD) for the open cavity are compared. Furthermore, both the scaled and higher ejection forces are employed in the test. The results indicate that a CCD installed in front of the cavity can effectively improve the aerodynamic characteristics of the flow field, which is beneficial for the store to rapidly pass through the interferential flow field of the cavity. Owing to the pitching moment acting on the internal store, the head of the store exhibits a nose-up configuration under both the CCD and NCD conditions; however, the value of the pitching moment coefficient in the CCD case is smaller than in the NCD case.

Conveyor belt structure of belt dryer: Analysis and optimization

The chain drive conveyor belt (CDCB) of the belt dryer is prone to generate impact load during operation, and the conveyor belt bedplate (CBB) will cause fatigue damage and fracture. This study presents an approach for calculating fatigue life, which combines the automatic dynamic analysis of mechanical systems (ADAMS), finite element analysis software (ANSYS), fatigue analysis software (FE-SAFE), and experimental stress analysis. The virtual prototype model for simulation of the CDCB is established, and its motion stability, contact impact force and motion trajectory are analyzed. The study shows that the chain drive polygon effect will cause periodic changes in velocity, and the motion trajectory has very good similarity. The stress experiment results show that the stress was considerable during the chain drive meshing process. The finite element analysis results show that the maximum stress of the old CBB is higher than the yield strength of the material, and the equivalent stress of the new CBB is lower than that of the old CBB. The area of the maximum stress of old CBB presents a fracture, which indicates the fatigue failure of the old CBB. The finite element calculation results were imported into FE-SAFE for fatigue life analysis, which compared the fatigue cycle number and safety factor of the old CBB and the new CBB. The results show that the new CBB can extend the service life of the belt dryer. The proposed analytical method for fatigue life is simple and effective and can serve as a reference for the fatigue life analysis of the key components of the belt dryer.

Synthesis and Verification of Finite-Time Rudder Control with GA Identification for Electric Rudder System

The electric rudder system (ERS) is the executive mechanism of the flight control system, which can make the missile complete the route correction according to the control command. The performance and quality of the ERS directly determine the dynamic quality of the flight control system. However, the transient and static characteristic of ERS is affected by the uncertainty of physical parameters caused by nonlinear factors. Therefore, the control strategy based on genetic algorithm (GA) identification method and finite-time rudder control (FTRC) theory is studied to improve the control accuracy and speed of the system. Differently from the existing methods, in this method, the difficulty of parameter uncertainty in the controller design is solved based on the ERS mathematical model parameter identification strategy. Besides, in this way, the performance of the FTRC controller was verified by cosimulation 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). In addition, the advantages of the proposed method are verified by comparing with the existing strategy results on the rudder test platform, indicating that the control accuracy is improved by 70% and the steady-state error is reduced by at least 50%.

Performance Analysis of Super Twisting Sliding Mode Controller by ADAMS–MATLAB Co-simulation in Lower Extremity Exoskeleton

Lower extremity exoskeleton is a kind of wearable robot and is used both in medical and industrial applications for different purposes. In the medical field it is used as a piece of therapeutic equipment and in the industry especially in defense, to carry heavy loads. This paper deals with the analysis of the performance of super twisting sliding mode controller (STSMC) on tracking the motion of the wearer by the lower extremity exoskeleton using automatic dynamic analysis of mechanical systems (ADAMS)–MATLAB co-simulation during walking and step climbing and the results are compared with a conventional PID controller. The model of the lower extremity exoskeleton is developed by solid-works software and the model of the human body is done with ADAMS software. Super twisting sliding mode controller (STSMC) is designed and simulated with Simulink. This paper also aims to develop a mathematical model of the system and analyze the performance of STSMC to control hip, knee, and ankle movements and also to point out the advantages of the ADAMS–MATLAB co-simulation over the conventional methods of modeling and simulation analysis of the controller to control the exoskeleton. Stability analysis of the controller is also done.