Applied Mechanics and Materials Vols. 138-139

Abstract: Take the trail design of arch bridge with a span of 600m in Part I as the research object, this paper proposes the existing critical problems of the structure, including structure’s static performance, stable problem and dynamic problem. Measures to improve structure’s mechanical performance have been proposed in the respects of structure system, component system and design parameters so as to improve the economy and safety of the structure.

Abstract: As one kind of mobile robots, the automatic guided vehicle (AGV) has been used in more and more applications. Meanwhile, some challenges in this field still exist, which limits the AGV’s further application. One of the greatest challenges is the energy conservation due to AGV’s limited energy-storage capability. Besides, the AGV tracking issue has not been well addressed yet though being studied for over two decades. This work presents an optimal velocity scheme for AGV energy-efficient tracking control, with consideration of both trajectory tracking and energy conservation involved in a nonlinear optimization problem. The proposed controller possesses the easiness for design and universality for kinematics modeling of other wheeled mobile robots. In addition, the controller’s stability and convergence were proved using Lyapunov theory. Finally, the computer simulation results demonstrated the effectiveness of the proposed controller.

Abstract: The heat pump technology which is as an effective energy-saving technology has attracted more and more attentions. A novel solar-air dual-source heat pump system which could synchronously use two heat sources has been provided. In this paper, the mathematical model of the new heat pump system has been built and the calculation accuracy of the mathematical model has been proved. Based on a novel solar-air dual-source heat pump system, the mathematical models of the thermophysical parameters of working fluids, compressor, capillary, condenser, evaporator, and heat pump system have been established. The distribution parameter method has been adopted in the mathematical models of condenser and evaporator. Three operation modes of the novel solar-air dual-source heat pump system have been simulated. The simulated results and the experimental results have been compared. The experiments of the novel solar-air dual-source heat pump system have been accomplished in the constant temperature and humidity laboratory. The compared results show that the error is less than 10%.

Abstract: Cycloid cam speed reducer is a widely used transmission. In practice, there are many kinds influence factors which affect transmission efficiency of cycloid cam speed reducer. In this research, dynamic measurement of the transmission efficiency has carried out by experiment It mainly studies the relationship between speed, load change and transmission efficiency during cycloid cam speed reducer working process. Experiment results show that transmission efficiency of cycloid cam speed reducer could be improved by increasing the load, other methods can also use such as reducing the input rotational speed.

Abstract: In Case-Based Reasoning (CBR), the determination of the weights of case characteristics is the base of the accurate case match, even influences the CBR execution. The current methods of determining the weights of case characteristics include subjective and objective weighting method but, some defects exist in them. In order to decrease subjectivity and increase objectivity of weight determining, the paper presented a new kind of combination weighting method that is the combination of the Analytic Hierarchy Process (AHP) with roughness set theory. The weighting process about AHP, roughness set theory, and combination method was described in detail respectively. An example was given to verify the effectiveness and accuracy of the combination weighting method.

Abstract: According to the engine condition and the complexity, uncertainty and nonlinear of the corresponding parameters, it puts forward an engine failure evaluation model based on the comprehensive decision-making fuzzy inference. This method takes all the corresponding characteristic parameters such as engine oil, vibration, and performance parameters as the study factors. By analyzing the sensitivity degree of these parameters to the change of the engine and its trend over time, different membership functions will be established based on various factors by means of statistical analysis and inference. Entropy-based data fusion and expertise can determine the levels of weight distribution of each factor in the comprehensive evaluation, thus, the engine failure evaluation model based on the comprehensive decision-making fuzzy inference can be established.

Abstract: Constant–current soft starting on induction motor based on fuzzy control is characterized as low system overshoot, fast response and relative stable starting process, so it can better solve the shortcomings existed in traditional methods and PID control methods, and improve the whole system reliability. In this article a special fuzzy control is adopted to complete the starting process, in which thyristor is the main current components and MCU is the control core. And this makes the entire starting process out of current impact.

Abstract: Considering the effects in the gravity, buoyancy, thrust and hydrodynamic on the underwater vehicle, based on the perspective of the dynamic control, established a relatively complete dynamic model of underwater vehicle, analyzed and designed the control system on this base. The control system is consisted of two control loop. Dynamic compensation of the within control loop based on the dynamic characteristic of the vehicle, by the role of the within control loop, the vehicle became an easy to control and a decoupled linear system. Outer control loop achieved a negative feedback control through the use of proportional and differential item on the actual vehicle pose and the posture deviation expected. Adjusted by adjusting the parameter matrix K_d, K_p can get the desired attenuation of the error, which can achieve precise motion control of underwater vehicles. Simulation results show that: the control model, in the paper, can be built for dynamic control of underwater vehicles, there is a strong anti-interference ability, can better realize the theory of time-varying trajectory tracking.

Abstract: In order to apply mathematical mechanization method during trajectory planning for NC machining, a platform framework is put forward which integrates the mathematics mechanization and trajectory planning. The essence and application of mathematical mechanization is analysis. The basic process and the correlation function of trajectory planning are discussed based on mathematical mechanization. The technology system of mathematical mechanization platform is established for the trajectory planning. And the operation flow of the mathematical mechanization platform is defined.

Abstract: The operational ability and mobility of astronaut in spacesuit is an important data for evaluation of the spacesuit, and to know it before use is also a basic data for the design of space station and spaceship. For this reason, mechanical arms were developed to measure the mobility and operational ability of astronaut in spacesuit. However, the mass and motion inertia are always influence the measuring system. This paper studied the dynamics characteristics of the mechanical arms. Dynamics model of the mechanical arms were setup and solved by MATLAB. Angle, angular velocity and angular acceleration of each joint were analyzed. The simulation supply a good basis for the development of the measuring manipulator, and it is helpful for the high accurate measurement.