Applied Mechanics and Materials Vols. 220-223

Abstract: Speed limit control is of great importance in freeway traffic control. This study aims to determine the reasonable speed limit through the application of a fuzzy inference method. Firstly, the components of a fuzzy logic controller are formulated. Then the influential factors of speed limit control are analyzed and the speed limit controller based on fuzzy logic is designed according to such information as the number of vehicles on the freeway, the road grade, and the weather conditions. Gauss, g-bell and triangle curves are used for the membership functions of the fuzzy variables. The rule base including 45 fuzzy rules is also established. Finally, the speed limit controller is simulated. Simulation results show that the speed limit values are reasonable. Fuzzy inference method provides a novel and practical way to realize speed limit control.

Abstract: A control scheme of direct DC electro-mechanical actuator based on discrete-time variable structure controller with Kalman filter is designed. In order to improve the perfect of the mechanical actuator mathematical model, the hinge moment is considered, and the coefficients of its transfer function are appropriately amended. For practical application, the Kalman filter is introduced to reduce the white noise in control process. The calculative results show that the precision of track and control is improved obviously.

Abstract: As a result of the non-linear characteristics and the uncertain disturbances in high-power AC servo system, it is difficult to construct an accurate mathematical model. In order to solve this problem, this article proposes a system identification method based on wavelet neural network. It makes full use of the advantages of the wavelet which combines neural network good time-frequency localization property and volatility of wavelet function and the nonlinear mapping capacity, self-learning and adaptive capacity of neural networks to solve the problem of non-unique RBF neural network approximation function expression. The simulation results show that the convergence rate, robustness and approximation accuracy of this method are better than the traditional neural network.

Abstract: In this paper the design and experiments of image sensor controlling circuit using in wireless endoscopic MEMS was studied. Through comparing the excellency and deficiency of various types of image sensors, and considering the working environment and requirements in the human body, it is pointed out that the CMOS image sensor with high integration density, low power consumption, small dimension and analog image signal output is suitable for the wireless endoscopic MEMS. By theoretically analyzing, the controlling circuits of two typical image sensors were designed successfully. The images captured in the animal experiments prove the validity of the designed circuits for the wireless endoscopic MEMS.

Abstract: To make the circuit self-start swiftly in the environment with much disturbance, according to the principle of being propitious to simplify state equation and output equation, assigned a next state for each bound term on Karnaugh map, and the next state must be a state of the valid cycle, at last tested the method by simulation. In the simulation, imitated the disturbance by the set pin or reset pin of flip-flop. The simulation based on electronics workbench 5.0C shows the effectiveness and feasibility of the method.

Abstract: This paper has introduced electromechanical coupling characteristics in the lower extremity exoskeleton systems, considered model ,according to legs supporting gait when people walking, established the load torque compensation model , and a mathematical model of knee position control system which is made of the servo valve, hydraulic cylinders and other hydraulic components, designed hydraulic cylinder position control loop in case of existing load force interference compensation, and used the method of combining the PID and lead correction network for frequency domain design ,ensured system to meet a certain stability margin. The simulation results show that this position control method can servo on the knee angular displacement of normal human walking, reached a certain exoskeleton boost effect, at the same time, met the needs of human-machine coordinated motion.

Abstract: The present work deals with a method for the modeling of a three-way servo-proportional valve actuated by a proportional solenoid. The model incorporates the primary nonlinear phenomenon exist in the solenoid, such as the hysteresis, nonlinear inductance and counter-electromotive force. Two ways are employed to simplify the model for the purpose of controller design. Firstly, the relations of current supply vs. flux linkage and flux linkage vs. electromagnetic force under different displacements of armature are captured by curve fitting and interpolation, with the advantage of keeping the nonlinear characteristics. Then the linearization method around the null-position of the spool is implemented, where the solenoid is modeled as a 1-order system, and the body of valve is treated as mass-spring 2-order system. Then the test-bed for the identification of main parameters and verification of the model is designed. The parameters are obtained from the experimental results where the armature and spool are locked at different positions. Finally, the model is verified as the dynamic responses of current supply and displacement of spool obtained from the simulation model agree well with the experimental results when the armature and spool are unlocked.

Abstract: Focus on the problem of steering trajectory tracking, a tracking control law based on dynamic surface is proposed. Other than existing methods, this paper considers combined lateral position and yaw synchronously control. The first order low pass filter is used to obtain the differential items of the lateral position and yaw, so as to eliminate the high order derivative from the final expression of the close loop law. This characteristic is very useful especially in real applications. The Lyapunov approach is employed to analysis the stability of the tracking system, and the convergence of the system is achieve. Simulation result validates the outstanding effectiveness of the proposed method for steering trajectory tracking.

Abstract: The magnetic flywheel is widely used in energy storage and spacecraft, and it needs to reduce the system’s power consumption effectively when designing the controller. Always, the magnetic bearing system’s performance depends on the tracking performance of the desired force signal. In order to balance the two goals between reducing magnetic system’s power consumption and guaranteeing its performance, a current power allocation way was proposed, and a static current optimization was given based on the way. According to the simulation and experimental results, this method can reduce the magnetic bearing system’s power consumption significantly and keep the tracking performance of force signal well on the same time.

Abstract: Two different car traction control methods were studied and some dynamic characteristics were found. Firstly, a new electric rear driving car with two DC motors driving independently is controlled by a combined system. The combined system consists of a feed-forward control, a feedback control and a SRC. Secondly, a built-in permanent magnet synchronous motor is selected as its driving motor. A motor driving system with a current loop and a speed loop was developed. The current loop consists of maximum torque per ampere control and field weakening control. Some simulation work was done based on MATLAB/Simulink software. The simulation study showed the control system can make the electric vehicle work well.