Applied Mechanics and Materials Vols. 670-671

Abstract: The grinding temperatures were measured with half-cylindrical thermocouple which made by grinding method and measrued with foil thermocouple which made by rolling method respectively when grinding brittle granite with an Al₂O₃ wheel. Experimental results include average grinding zone temperatures and grains’ temperatures were analysed. The deviation of average grinding zone temperatures measured by them were within 6%. The foil thermocouples do not easily to lap due to the brittleness of the workpiece which usually makes the joint of thermocouples disconnected. But half-cylindrical thermocouples are more convenient to be prepared and be used than foil ones. However, the periodic “flash” impulses which reflect the grains’ temperature measured by half-cylindrical thermocouple were about 51% lower than the others. According to time constant, the thickness of the thermocouple less than 0.007mm is a necessary condition for measure the grains’ temperatures without distortion. The half-cylindrical thermocouple is too thick to have a momentary response time thus makes it out of the measurement accuracy range when it is used to measure the temperature of the grains. Therefore, foil thermocouple has an optimum thickness of 0.007mm is suitable for measuring the grains’ temperature while half-cylindrical thermocouple with average thickness less than 0.12mm is suitable for measuring the average grinding zone temperature.

Abstract: Cognitive radio can improve the spectrum utilization efficiency of spectrum band. So spectrum sensing is the key technology in cognitive radio network. Our main task is to design a cyclic detector with better detection performance than energy detector. This paper studies single-user spectrum detector in cognitive radio networks, including cyclic spectrum detector and energy detector. We firstly analyzed the energy spectrum sensing mathematic model for comparison, then we proposed the new simulation model and detailed simulation steps of this cyclic spectrum sensing detector. Simulation results demonstrate that the cyclic spectrum detector has better performance than energy detector while the SNR of channel condition is low.

Abstract: There is a bias drift of silicon microgyroscope when power on which limits its application in higher precision field. This paper analyzes and validates the main cause of bias drift, combined with theoretical analysis of demodulation and experimental results, which has a great significance for improving the performance of silicon microgyroscope. First of all, operating principle of silicon microgyroscope is introduced and theoretical analysis on bias drift is made on the basis of DC output voltage of microgyroscope. Secondly, demodulated signals’ amplitude and phase are analyzed in Matlab with the experimental data. By contrasting theoretical and experimental bias drift, the accuracy of theoretical formula is verified. It turns out that, the relative error of bias drift from 2-hours value to stable value is 5.5%, it’s 6.6% for 1-hour value to stable value and for beginning it’s just 1.7%. Experimental results agrees well with the theoretical analysis, which verifies that the main cause of bias drift of silicon microgyroscope is the phase difference between Vds and Vsense. This conclusion can provide some guidance for structure design optimization and circuits improving.

Abstract: To improve the anti-vibration capability of silicon mcrogyroscope, making it works well under the vibration environment, this paper analyzes the dual-mass silicon mcrogyroscope and did the following works. First of all, the operating principle, analysis parameters of silicon microgyroscope and the vibration condition are introduced. Secondly, this paper proposes a vibration analysis method base on the signal conversion between time domain and frequency domain and establishes a Simulink demodulation model according to circuits of silicon microgyroscope. Finally, we get the conclusion that under the condition of vibration, composition with the same frequency of Vds in Vsense signal is the main influence factor of bias stability by analyzing experimental data. This has a great significance for improving the anti-vibration capability and guiding the interior structure design of silicon microgyroscope.

Abstract: This paper describes the Quadcopter’s body structure; principles of flight, hardware configuration, and analyzes the process of attitude algorithm adopting the complementary filter algorithm as well as the flight control algorithms.

Abstract: For a weakly nonlinear autonomous systems, the nonlinear coordinate transformation is provided in the form of power series expansions and the mathematical transformation from the physics system coordinate to the modal coordinate is presented. And then, according to the relations between physics system coordinate and modal coordinate, a method of nonlinear modal superposition is obtained. Using this method, the general solution of the vibration under any initial condition can be answered. In order to explain the applications of the method, numerical examples are presented in this paper.

Abstract: This paper present a pedestrian following mobile robot with binocular vision sensor. Because Kinect is one of the most inexpensive devices of depth-cameras, it is used in our application. Human skeleton is extracted by using Kinect, and the location of human is checked by projecting the three-dimensional (3D) pose of skeleton onto 2D screen. This 2D screen is separated into three parts, left, middle and right. Mobile robot rotates and translates according to the corresponding location of pedestrian. To make the robot move forward and backward, the distance between spine point and mobile robot is calculated. Finally, a real experimental result is used to validate our proposed method.

Abstract: This paper is devoted to vehicle movement control method based on the natural energy recovery [1] and position-path control approach [2,3,4]. This method ensures the fullest use of kinematic energy of the controlled vehicle. Method is applied for path profile with variable height. Vehicle velocity is changed to minimize kinematic energy losses. The time of the path passage is accounted in the designed method. In this report typical profiles of the controlled vehicle are considered. In general case the vehicle velocity program is developed on base of solutions for typical profiles. The vehicle velocity program is changing while vehicle is moving. The developed method is applied for control of trains implemented with electrical power drives. On base of train model studying it is proved that optimal mode of trains acceleration is maximal traction. The maximal traction ensures minimum energy consumption of train drives. But the traction of trains is extreme function of the speed wheel slip [5, 6]. Therefore the new extreme control for the train drives is developed. This method supports trains traction in extreme value. The developed method is implemented in simulator based on Matlab and Universal Mechanism. Movement of a freight train on a real track section is simulated.

Abstract: The article expounds the square steel tube straightening machine which is given priority to with PLC (Siemens S7-200) of the control system use testing car`s sensor to test square steel tube`s bending. Then, according to the curve`s size and location of the peaks and troughs of the curvature degree of square steel tube straightening machine control correct device again find square steel tube`s position of the peaks and troughs, and the peaks and troughs in the use of hydraulic cylinder for the opposite direction of compression. The hydraulic cylinder travel sizes are set to peak and trough values and tests again, until they meet the requirements. This control system can meet the control demands of square steel tube straightening machine, reflected the applicability, convenience, safety and reliability.

Abstract: This paper presents a method to track and follow target person. A laser range finder (LRF) is used to measure highly accurate distance of objects with the range of 180 degrees. First of all, the erroneous data are excluded due to the error of LRF. Then all the raw sensor data are separated into many groups when the difference of the measuring distances of two adjacent laser points are beyond a limited value. For each group, the width is calculated, and it is considered as human legs if the defined conditions are satisfied. Finally, a real-time human following experiment with a SICK LRF and PIONEER mobile robot is done to validate our proposed method.