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To address the issues of leveling difficulties and poor stability of crawler combine harvesters in hilly and mountainous regions, this research analyzed the mechanical causes of overturning instability in crawler combine harvesters and designed an omnidirectional attitude adjustment chassis based on a five-bar mechanism. A 3D model was developed in SolidWorks, and coupled rigid-flexible simulations were performed using RecurDyn. Results showed that the chassis could achieve an overall lift, lateral adjustments and longitudinal adjustments (0-100 mm, -5.18° to 5.55° and -4.06° to 5.15° respectively), with maximum dynamic stress occurring on the left front and left rear rotational arms. A dynamic stress testing system was established to conduct response surface experiments. Field test results revealed that the primary factors affecting the maximum stress of the left front rotational arm were the grain tank loading mass, lateral adjustment angle, and longitudinal adjustment angle. For the left rear rotational arm, the order was the longitudinal adjustment angle, lateral adjustment angle, and grain tank loading mass. Validation tests showed that at a lateral adjustment angle of 3.61°, a longitudinal adjustment angle of 3.20°, and a grain tank load of 350 kg, the average maximum stresses were 483.19 MPa for the left front rotational arm and 188.95 MPa for the left rear rotational arm, with corresponding structural safety factors of 1.61 and 4.31, meeting strength requirements. This work provides methods for optimizing the design and reliability testing of agricultural machinery chassis with attitude adjustment functions in hilly terrains.

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The motion process of legged robots contains not only rigid-body motion but also flexible motion with elastic deformation of the legs, especially for heavy loads. Hence, the characteristics of the flexible components and their interactions with the rigid components need to be considered. In this paper, a hierarchical control strategy for robots with rigid–flexible coupling characteristics is proposed. This strategy involves (1) leg force prediction based on real-time motion trajectories and feedforward compensation for the error caused by flexible components; (2) building upon the centroid dynamics model of the rigid-body chassis, the centroid trajectories (centroid angular momentum (CAM) and centroid linear momentum (CLM)) and the body trajectory are taken into account to derive the optimal drive torque for maintaining body stability; (3) finally, the precise force control of the hydraulic drive units is achieved through the sliding mode control algorithm, integrating the dynamic model of the flexible legs. The proposed methods are validated on a giant hexapod robot weighing 3.5 tons, demonstrating that the introduced approach can reduce the robot's vibrations. [ABSTRACT FROM AUTHOR]

In order to study the dynamic characteristics of flap transmission mechanism with clearance joints, based on an improved nonlinear normal impact force model with variable stiffness, and the elastic factor of connecting rod, the angular velocity and angular acceleration of the steering gear are simulated and analyzed with the conditions of different clearance joints （c=0、c=δ and c=1.6δ） , and different friction parameters （0.06、0.08 and 0.1）. The dynamic output angular velocity and angular acceleration of the flap transmission exhibit obvious oscillation, and the amplitude of the angular acceleration is larger than that of the angular velocity oscillation; at the same time, when the driving load changes, the angular velocity and angular acceleration fluctuate greatly, but the fluctuation degree in the case of c=0 is greater than that with clearance; in addition, the higher the friction coefficient at the clearance joint is, the greater the amplitude of angular velocity and angular acceleration oscillation are, accompanied by high-frequency oscillation and delay phenomenon.

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In view of high-speed working characteristics of four-bar beating-up system, the simulation study was carried out under the influence of joint clearance and beating-up resistance. The discontinuous contact model with two-state was applied to clearance modeling of crank bearing. A rigid flexible coupling model of double side four-bar beating-up system was set up by ADAMS/View which on the basis of mechanism design and analysis of beating-up principle. The beating-up resistance from sley was transformed into an equivalent torque on rocking shaft by use of step function. The results of contact dynamics simulation with different clearance states show that there are obvious differences between flexible body simulation and rigid body simulation, and the former can better reflect the real situation of beating-up; The clearance of 0.03 mm and 0.06 mm has a great influence on sley vibration which is not conducive to reduce vibration and noise for loom system; 0.09 mm clearance will not only cause high-frequency reaction force on main shaft bearing, but also aggravate contact and collision between crank and connecting rod; There are many overlaps between centroid trajectory of flexible main shaft with clearance and ideal trajectory, because of that, multi-point contact collision occurs in the crank bearing. The study is helpful to explore mechanical characteristics and working mechanism of the four-bar beating-up system with clearance.

In order to ensure the safety of tower crane construction and prolong the service life of tower crane, the fatigue life of tower crane was evaluated. Firstly, taking a certain type of tower crane as the research object, SolidWorks was used to conduct three-dimensional modeling, the typical working conditions of the tower crane were analyzed. The Workbench was used to determine the maximum stress position of the tower crane’s static analysis results. Then ANSYS APDL was combined with ADAMS to conduct rigid-flexible coupling dynamics simulation, and the load spectrum of the working cycle under the working conditions was obtained. Finally, the fatigue five-block diagram of NCODE Design Life was used to analyze the fatigue of tower crane under this working condition. The results show that the most frequent fatigue failure location is near the connecting position between the upper chord of the sixth crane and the outer connecting rod, and the maximum damage of each cycle of the tower crane lifting arm is 3.598×10-6 and the minimum number of cycles is 2.799×105 under this working condition, which meets the design requirements of the tower crane. It provides reference value for fatigue life evaluation and design of tower crane in service, and can be used as the basis for maintenance and replacement of tower crane parts. [ABSTRACT FROM AUTHOR]

In order to study the vibration characteristics of gun barrel under the action of moving projectile in gun launching process, taking an artillery gun for example, based on the Euler-Bernoulli beam theory, the coupled equations of vibration of a moving projectile elastic tube coupled with the initial deflection of the tube body are established. Using the finite element software ABAQUS and the dynamic analysis software ADAMS, the rigid flexible coupling dynamic model considering the initial deflection is established, and the numerical results are verified. On the basis of the model, the law of the muzzle velocity and the mass of the projectile affecting the muzzle vibration characteristics are analyzed. The results show that the initial deflection of the tube body has a great influence on the vibration analysis results, and can not be ignored. In the case of the initial deflection of the tube, the larger the projectile velocity is, the larger the muzzle vibration amplitude is. When the velocity is constant, the larger the projectile mass is, the larger the muzzle vibration amplitude is.

Ａｉｍｉｎｇ ａｔ ｔｈｅ ｐｒｏｂｌｅｍ ｔｈａｔ ｆａｔｉｇｕｅ ｌｉｆｅ ｏｆ ｆｏｏｔ￣ｓｕｐｐｏｒｔｅｄ ｍｅｃｈａｎｉｓｍ ｉｓ ｕｓｅｄ ｉｎ ｌｏｎｇ￣ｔｅｒｍꎬ ｔｈｅ ｍｅｔｈｏｄ ｆｏｒ ｆａｔｉｇｕｅ ｌｉｆｅ ａｎａｌｙｓｉｓ ｂａｓｅｄ ｏｎ ｒｉｇｉｄ￣ｆｌｅｘｉｂｌｅ ｃｏｕｐｌｉｎｇ ｗａｓ ｐｕｔ ｆｏｒｗａｒｄ ｗｉｔｈ ｔｈｅ ｒｅｓｅａｒｃｈ ｏｎ ｉｎｔｅｎｓｉｔｙꎬｍｅｃｈａｎｉｃａｌ ｃｈａｒａｃｔｅｒｉｓｔｉｃｓꎬ ｆａｔｉｇｕｅ ｌｉｆｅ. Ｆｉｒｓｔ ｔｈｅ ｔｈｒｅｅ￣ｄｉｍｅｎｓｉｏｎａｌ ｍｏｄｅｌ ｗａｓ ｂｕｉｌｔ ｂｙ ｓｏｆｔｗａｒｅ Ｓｏｌｉｄｗｏｒｋｓ ａｎｄ ｔｈｅ ｍｏｄｅｌ ｗａｓ ｉｍｐｏｒｔｅｄ ｔｏ ｔｈｅ Ａｎｓｙｓ/ Ｗｏｒｋｂｅｎｃｈ ｂｙ ｆｏｒｍａｔ ｏｆ Ｐａｒａｓｏｌｉｄ. Ｔｈｅｎ ｔｈｅ ｆｉｎｉｔｅ ｅｌｅｍｅｎｔ ｍｏｄｅｌ ｗａｓ ｅｓｔａｂｌｉｓｈｅｄ ｔｏ ｂｅ ａｎａｌｙｓｅｄ ｔｏ ｍａｋｅ ｓｕｒｅ ｔｈｅ ｄａｎｇｅｒｏｕｓ ｐａｒｔ ｉｎ Ａｎｓｙｓ/ Ｗｏｒｋｂｅｎｃｈ. Ａｆｔｅｒ ｔｈｅ ｍｏｄｅ ｎｅｕｔｒａｌ ｆｉｌｅ ｏｆ ｄａｎｇｅｒｏｕｓ ｐａｒｔ ｗａｓ ｂｕｉｌｔ ｉｎ Ａｎｓｙｓꎬｔｈｅ ｒｉｇｉｄ￣ｆｌｅｘｉｂｌｅ ｃｏｕｐｌｉｎｇ ｍｏｄｅｌｉｎｇ ｗａｓ ｂｕｉｌｔ ｃｏｍｂｉｎｅ ｗｉｔｈ ｔｈｅ ｍｕｌｔｉｂｏｄｙ ｄｙｎａｍｉｃｓ ｔｏ ａｎａｌｙｓｅ ｔｈｅ ｍｅｃｈａｎｉｃａｌ ｐｅｒｆｏｒｍａｎｃｅｓ ａｎｄ ｔｈｅ ｌｏａｄ ｓｐｅｃｔｒｕｍｓ ｏｆ ｔｈｅ ｄａｎｇｅｒｏｕｓ ｐａｒｔ ｉｎ ｋｅｙ ｎｏｄｅ ｗｅｒｅ ｏｂｔａｉｎｅｄ. Ｔｈｅｎ ｔｈｅ ｒｅｓｕｌｔｓ ｗａｓ ｍａｄｅ ｆｏｒ Ｓ￣Ｎ ｏｆ ｆａｔｉｇｕｅ ｉｎ ｎＣｏｄｅ Ｄｅｓｉｇｎ￣Ｌｉｆｅ ｔｏ ｐｒｅｄｉｃｔ ｔｈｅ ｓｔｒｅｓｓ ｆａｔｉｇｕｅ ｌｉｆｅ ｂａｓｅｄ ｏｎ ｔｈｅ ｍｏｄｉｆｉｅｄ Ｐ￣Ｓ￣Ｎ ｃｕｒｖｅ. Ｆｉｎａｌｌｙꎬｔｈｅ ｐｒｏｔｏｔｙｐｅ ｗａｓ ｍａｄｅ ａｎｄ ｔｅｓｔｅｄ ｂｙ ｆａｔｉｇｕｅ ｔｅｓｔ ｄｅｖｉｃｅｓ . Ｔｈｅ ｒｅ￣ ｓｕｌｔｓ ｉｎｄｉｃａｔｅ ｔｈａｔ ｔｈｅ ｄａｎｇｅｒｏｕｓ ｆａｔｉｇｕｅ ｆａｉｌｕｒｅ ｐｏｓｉｔｉｏｎ ｈａｐｐｅｎ ｉｎ ｂｅｎｄꎬｂｕｔ ｔｈｅ ｍｉｎｉｍｕｍ ｌｉｆｅ ｏｆ ｔｈｅ ｎｏｄｅｓ ｓａｔｉｓｆｙ ｔｈｅ ａｐｐｌｉｃａｔｉｏｎ ｒｅｑｕｉｒｅ￣ ｍｅｎｔｓꎬａｎｄ ｉｔ ｖｅｒｉｆｙ ｔｈｅ ｍｅｔｈｏｄｏｌｏｇｙ ｉｓ ｈｅｌｐｆｕｌ ｔｏ ｆａｔｉｇｕｅ ａｎａｌｙｓｉｓ ａｎｄ ｓｉｍｕｌａｔｉｏｎ ｂｙ ｔｅｓｔ. [ABSTRACT FROM AUTHOR]

Ｉｎ ｏｒｄｅｒ ｔｏ ｓｏｌｖｅ ｔｈｅ ｐｒｏｂｌｅｍ ｔｈａｔ ｔｈｅ ｂｅａｒｉｎｇ ｏｆ ｔｒａｎｓｍｉｓｓｉｏｎ ｃａｎ ｎｏｔ ｂｅ ｄｉａｇｎｏｓｅｄ ｉｎ ｔｉｍｅ ａｎｄ ａｃｃｕｒａｔｅｌｙ, ｔｈｅ ｒｉｇｉｄ ｆｌｅｘｉｂｌｅ ｃｏｕｐｌｉｎｇ ｄｙｎａｍｉｃｓ ｓｉｍｕｌａｔｉｏｎ ｔｅｃｈｎｏｌｏｇｙ ｗａｓ ａｐｐｌｉｅｄ ｔｏ ｔｈｅ ｆａｕｌｔ ｄｉａｇｎｏｓｉｓ ｏｆ ｇｅａｒｂｏｘ ｂｅａｒｉｎｇ. Ｆｉｒｓｔｌｙ, ｔｈｅ ｔｈｅｏｒｙ ｏｆ ｄｏｕｂｌｅ ｉｍｐａｃｔ ｏｆ ｂｅａｒｉｎｇ ｗａｓ ｂｒｉｅｆｌｙ ａｎａｌｙｚｅｄ, ｔｈｅｎ ａｃｃｏｒｄｉｎｇ ｔｏ ｔｈｅ ａｃｔｕａｌ ｐａｒａｍｅｔｅｒｓ ｏｆ ａｒｍｏｒｅｄ ｖｅｈｉｃｌｅｓ ｇｅａｒｂｏｘ ｂｅａｒｉｎｇ ｂｅａｒｉｎｇ ｉｓ ａ ｒｉｇｉｄ ｆｌｅｘｉｂｌｅ ｃｏｕｐｌｉｎｇ ｄｙｎａｍｉｃ ｍｏｄｅｌ ｏｆ ＡＤＡＭＳ ｂａｓｅｄ ｏｎ ｆｏｕｒ ｄｉｆｆｅｒｅｎｔ ｓｉｚｅｓ ｏｆ ｔｈｅ ｂｅａｒｉｎｇ ｏｕｔｅｒ ｒｉｎｇ ｆａｕｌｔ ｗｅｒｅ ｓｉｍｕｌａｔｅｄ. Ｔｈｅ ｏｕｔｅｒ ｒａｃｅ ｆａｕｌｔ ｂｅａｒｉｎｇ ｗｅｒｅ ａｎａｌｙｚｅｄ ｂｙ ｔｉｍｅ-ｆｒｅｑｕｅｎｃｙ ｃｈａｒａｃｔｅｒｉｓｔｉｃ ｏｆ ｖｉｂｒａｔｉｏｎ ｓｉｇｎａｌｓ ｏｆ ｄｉｆｆｅｒｅｎｔ ｓｉｚｅｓ ｕｎｄｅｒ ｔｈｅ ｆａｕｌｔ. Ｔｈｅ ｖａｌｉｄｉｔｙ ｏｆ ｔｈｅ ｒｉｇｉｄ ｆｌｅｘｉｂｌｅ ｃｏｕｐｌｉｎｇ ｍｏｄｅｌ ａｎｄ ｓｉｍｕｌａｔｉｏｎ ｐｒｏｃｅｓｓ ｗａｓ ｖｅｒｉｆｉｅｄ ｂｙ ｔｈｅ ｅｘｐｅｒｉｍｅｎｔａｌ ａｎａｌｙｓｉｓ. Ｔｈｅ ｓｉｍｕｌａｔｉｏｎ ａｎｄ ｅｘｐｅｒｉｍｅｎｔａｌ ｒｅｓｕｌｔｓ ｓｈｏｗ ｔｈａｔ ｄｏｕｂｌｅ ｉｍｐａｃｔ ｐｈｅｎｏｍｅｎｏｎ ｏｃｃｕｒｓ ｉｎ ｔｈｅ ｔｉｍｅ ｄｏｍａｉｎ ｓｉｇｎａｌ ｗｉｔｈ ｔｈｅ ｉｎｃｒｅａｓｅ ｏｆ ｆａｕｌｔ ｓｉｚｅ, Ａｃｃｏｒｄｉｎｇ ｔｏ ｔｈｅ ｔｉｍｅ ｉｎｔｅｒｖａｌ ｏｆ ｔｈｅ ｄｏｕｂｌｅ ｉｍｐａｃｔ ｉｎ ｔｈｅ ｔｉｍｅ ｄｏｍａｉｎ ｓｉｇｎａｌ, ｔｈｅ ｓｉｚｅ ｏｆ ｔｈｅ ｃｏｒｒｅｓｐｏｎｄｉｎｇ ｏｕｔｅｒ ｒｉｎｇ ｏｆ ｔｈｅ ｂｅａｒｉｎｇ ｃａｎ ｂｅ ｊｕｄｇｅｄ. Ｔｈｅ ｒｅｓｕｌｔｓ ｐｒｏｖｉｄｅ ｔｈｅ ｈｅｌｐ ｆｏｒ ｇｒａｓｐｉｎｇ ｔｈｅ ｆａｉｌｕｒｅ ｏｆ ｔｈｅ ｇｅａｒｂｏｘ ｏｆ ｔｈｅ ａｒｍｏｒｅｄ ｖｅｈｉｃｌｅ ｉｎ ｔｉｍｅ ａｎｄ ｒｅａｌｉｚｉｎｇ ｔｈｅ ｓａｆｅ ｏｐｅｒａｔｉｏｎ ｏｆ ｔｈｅ ａｒｍｏｒｅｄ ｖｅｈｉｃｌｅ. [ABSTRACT FROM AUTHOR]

Copyright of Journal of the Tianjin Polytechnic University / Tianjin Gongye Daxue Xuebao is the property of Journal of Tianjin Polytechnic University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The rigid flexible coupling system with a payload at non-tip position of the flexible beam is studied in this paper. Using the theory about mechanics problems in a non-inertial coordinate system and the subsystem modeling principle, the dynamic equations of the rigid flexible coupling system with dynamic stiffening are established via material mechanics and the angular momentum principle. This paper elucidates that dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beam and the transverse vibration deformation of the beam. First, the payload at non-tip position is incorporated into the continuous dynamic equations of the system by means of the Dirac function and the Heaviside function. Then, the constrained modes of the flexible beam are analyzed. According to the boundary conditions of the constrained modes, a reasonable position interval of the payload is proposed. It corrects the inaccurate understandings in some papers. Finally, based on the conclusions of orthogonalization about the normal constrained modes, the finite dimensional state space model suitable for controller design is obtained. In addition, in order to make the finite dimensional dynamic model established more practical, based on the common constrained modes, the dimensionless variables and parameters are introduced, and the dimensionless finite dimensional dynamic model of the system is derived. The numerical simulation results show that: dynamic stiffening is included in the first-order dynamic model established in this paper, therefore, it can indicate the dynamic responses of the rigid flexible coupling system with large overall motion accurately; the payload has a softening effect on the dynamic behaviors of the flexible beam, and the effect would be more obvious when the payload has a larger rotary inertia or a larger mass, or lies closer to the tip of the beam. [ABSTRACT FROM AUTHOR]

A symmetric flexible rotating spacecraft can be modeled as a distributed parameter system of a rigid hub attached to two flexible appendages with tip masses. First, Hamilton's extended principle is utilized to establish a general treatment for deriving the dynamics of multi-body dynamical systems to establish a hybrid system of integro-partial differential equations that model the evolution of the system in space and time. A Generalized State Space (GSS) system of equations is constructed in the frequency domain to obtain analytic transfer functions for the rotating spacecraft. This model does not include spatial discretization. The frequency response of the generally modeled spacecraft and a special case with no tip masses are presented. Numerical results for the system frequency response obtained from the analytic transfer functions are presented and compared against the classical assumed modes numerical method with two choices of admissible functions. The truncation-error-free analytic results are used to validate the numerical approximations and to agree well with the classical widely used finite dimensional numerical solutions. Fundamentally, we show that the rigorous transfer function, without introduction of spatial discretization, can be directly used in control law design with a guarantee of Lyapunov stable closed loop dynamics. The frequency response of the system is used in a classical control problem where the Lyapunov stable controller is derived and tested for gain selection. The correlation between the controller design in the frequency domain utilizing the analytic transfer functions and the system response is analyzed and verified. The derived analytic transfer functions provide a powerful tool to test various control schemes in the frequency domain and a validation platform for existing numerical methods for distributed parameters models. The same platform has been used to obtain the frequency response of more complex beam models following Timoshenko beam theory and the control problem for such models can be pursued in future works. [ABSTRACT FROM AUTHOR]