Applied Mechanics and Materials Vols. 701-702

Abstract: The time-dependent reliability model of Mechanical Component is influenced by many parameters such as stress, load, strength, strength degeneration and lifetime index. This paper builds the time-dependent reliability model when life is measured by the loading numbers. The variety law of mechanical component’s reliability with the lifetime is derived from the built model and simulation of tooth carrier in feed mechanism used in the sewing machine. The result shows that the time-dependent reliability model is effective and the reliability of component decreases obviously with the loading numbers when the strength degeneration is considered.

Abstract: For quadrotor unmanned air vehicles (UAVs) nonlinear control problems under disturbance conditions, a nested loop control approach is presented to realize robust control. The robust control approach is proposed to solve the stabilization and navigation problems in the quadrotor. The robust control strategy is composed of two controllers. A nonlinear backstepping controller is designed for the inner loop to stabilize the attitude angle. A PID controller based on BP neural network is designed for the outer loop in order to generate the reference path for the inner loop. Numerous simulations and flight test experiments have been made to study the performance of controller based on the independently developed quadrotor UAV. The results illustrate that the proposed controller has good stability, maneuverability and robustness.

Abstract: On-orbit service technology can extend the working life of the spacecraft, and improve the ability to perform various tasks. Docking mechanism is the key equipment of the space docking. The cushion performance of the system determines the dynamic characteristics in the docking process, and it is one of the important factors influencing the docking success or not. It is established that mathematical modeling of the new grasping mechanism in the buffering process, due to lack of the experiment equipments, the dynamic simulation on computer is an effective method to test and verify the parameters or evaluate the performance of the buffer system designed. Simulation analysis is conducted to get the corresponding buffer force for four different sets of buffer parameter, and it provides important basis for docking cushioning structure optimization.

Abstract: In this paper, a kind of Linear Synchronous Motor (LSM) with Permanent Magnet (PM) arranged in Halbach array and IronLess Coil (PMH&ILC) is presented for Magnetic Levitation Vehicles (Maglev). First, the propulsion force of this kind of LSM is deduced analytically. Then, the influences of pole spacing, the current in the coil, the width of the motor and the size of the Halbach array on the propulsion force are analyzed mathematically in detail. Based on the results, the design method and basic principle of PMH&ILC-typed LSM are proposed, which shows a better performance with small pole spacing, higher permanent magnet array, optimal value of the width of the permanent magnet Halbach and so on. Finally, a sample LSM system is designed according to the requirements of Maglev propulsion system.

Abstract: To estimate the influences of uncertain factors on the modeling error of maglev vehicles, the single electro-magnet is taken as the object in this paper. Researches on the model-building error are carried out, including factors of the uncertainty of the inductor, the elasticity of the guideway and the coupling between Modules. Also, the model-building errors are analyzed numerically from the view of L_∞ norm. And the calculation results are presented, which shows severe model-building severe error with the simplified model. The results are revelatory to comprehend the phenomena of the vehicle’s vibration, and to search after new methods of levitation control for EMS maglev vehicles.

Abstract: A kind of active balancer using planetary gear train was developed as a solution for dynamic balancing, aiming to balance the mechanisms actively and bring little changes to their original structure and motion. It consists of a two-DOF planetary gear train and a controllable motor. One of the two inputs doubles as the output, connected to the machine to be balanced. The other input is driven by the control motor. The conceptual design of the proposed balancer was discussed. Taking one scheme as example, design procedure of the balancer was introduced. Numerical examples were given to demonstrate the effectiveness of the proposed balancer. The results showed that much more flexibility on the dynamic performance under different working conditions were achieved by selecting suitable input speed trajectories and structural parameters of the planetary gear train of the active balancer.

Abstract: The study investigates the structure and characteristic of Continuously Variable Transmission (CVT) through building the hardware-in-the-loop test bed of the CVT. Matlab/Simulink is utilized to establish a vehicle simulation model and a speed ratio and clamping force coordinated control model. In addition, the speed ratio test, based on the active coupling control strategy, is carried out with the result of contrast curves between coupling control and traditional speed ratio control strategy. The real-time simulation proves a better controlling effect.

Abstract: Opening the almond currently rely on the manual to complete and is unable to meet the requirements of mass production. For the design of almonds opening machine of automatic control device, we determine the morphological changes, vibration characteristics, extrusion force changes and other parameters of the almond of opening moments, so as to provide calculation basis for choosing suitable step motor and determining parameters of circuit’s electrical components. Electromagnetic buzzer as a vibration sensor to detect the vibration signal, the photoelectric sensor to detect the almond’s position signal, the proximity switch sensor to detect the working position and amplified signals to process circuits, under the control of MCU, the step motor driving a load let the almond opening process achieve the automatic.

Abstract: The feed drive system is important functional components which effects on precision and efficiency of transmission and cost of CNC milling machine tools. So the designe of the feed drive system of economical CNC milling machine tool is researched. Firtsly the general design scheme which includes the transmission scheme and basic parameters of CNC milling machine tool is determined. Then according to the milling force calculated during mill processing, linear rolling guide, ball screw and stepping motor of X axis and Y axis of feed drive system are respectively calculated, selected and checked in detail. Using the Solid works software for 3D modeling and assembly of mechanical parts of feed drive system, By the scheme comparison, selecting the CNC system of Huazhong century star HNC-21 and accomplishing the electrical connection of CNC system.The feed drive system of economical CNC milling machine in the desing is high performance and low cost,and meet accuracy requirement.

Abstract: This paper presents the kinematics for 3-PTT parallel machine tools, the kinematic is analytically performed, the forward and inverse position kinematic equations are explicit functions and workspace is derived and there is no singularity configuration and kinematic coupling in the whole workspace. The manipulability analytical of the parallel machine tool is investigated by the Jacobian matrix.