Earticle

In this paper, a universal loss calculation model in simulation is established in MATLAB / Simulink which can be used in not only ideal but also non-ideal conditions ( non-sinusoidal load current and grid voltage, unfixed system parameters such as stator resistance for induction motors, unstable DC voltage with fluctuation, aperiodic modulation strategies with unfixed switching frequency, and so on). Considering the influence of dead time, steady operating states of each device can be obtained by the measurement of the load current and gate triggering pulses of every IGBT in a phase arm which can be easily measured in experiment rather than the currents and voltages of devices. Analyses in two-level topology and Neutral-Point-Clamped (NPC) three-level topology were done as examples. In periodic pulse width modulation with sinusoidal modulation wave, consistency among results from the proposed simulation model, the formula commonly used and commercially available loss software provided by power device manufacturer was shown. Through the design of a two-level inverter in hysteretic control, experimental verification of proposed method was applied. Calculating power loss in this method can be adapted to different converter topologies with various control strategies which is not even for ideal conditions.

Targeting at the features of concurrency and mobility, π calculus nowadays could serve as a highly effective tool of modeling and evaluating the software system. After a brief introduction of π calculus, the paper mainly discusses a comparison algorithm based on π calculus which is used frequently in software modeling. Since there are two different ways of data storage: the random storage and the linked list storage of elements, the paper analyzes both, with the special emphasis on the algorithm in the comparison carried on by any two elements.

The trajectory tracking problem of a wheeled omnidirectional robot is addressed in this paper. The proposed controller takes into account the dynamics of the wheeled omnidirectional robot when adaptive linear control with computed torque is utilized for tracking its trajectory. The computed torque method was employed to follow a reference trajectory but there were certain degrees of uncertainties in parameters such as estimation of mass and inertia which caused the performance to deviate from the ideal case. The adaptive linear control method is used to overcome the degradation of the computed torque when there is drift in vehicle parameters. Lyapunov stability criteria was utilized to prove that the proposed adaptive linear control with computed torque method is stable. The proposed strategy was evaluated through numerical simulation which showed the better performance in tracking a reference signal of the adaptive linear control with computed torque method as compared to computed torque method only.

This paper focuses on the path planning for a mobile robot which is operated in indoor environment. Since the layout of indoor environment is a hybrid structure of known and unknown, this paper presents a hybrid algorithm which uses the Max-Q method and the option method together. Firstly, a novel task graph and high level definition are presented to divide sub-tasks. Then, the appropriate definitions of states, actions and options could let a robot fulfill a task. Finally, an angle parameter is employed in the reward function to ensure a robot select a shorter path and adjust orientation timely. In the series of simulations, a robot can arrival any position successfully with random initial positions and directions. Moreover the results show that a robot can overcome the local minimal problem with our hybrid method.

The paper carries a research on the self-propelled farmland levelling machine that not only can level the soil surface but also collect the sundries and designs soil-sundry levelling and collecting device, soil- sundry separating device and levelling control system based on laser and inclination sensor. The hydraulical motor drives the leveling and collecting knife shaft rotate to collect the sundries and roughly level the surface. The separating device separates the sundries and the broken soil through the vibration. The levelling control system adopts inclination sensor and laser emitter as the datum signal to form the datum plane. The hydraulic servo system controls the levelling device to work on the plane that parallels with the datum plane. At the same time, the paper establishes the hydraulic servo system mathematical modal and utilizes MATLAB to analyze, revise and simulate for the system mathematical modal. The test result shows that self-propelled farmland levelling machine is satisfied with the levelling request.

With the development of computer animation and demands for gaming, the motion simulation of trees in wind filed has become one of the research hotspots. In order to better simulate the 3D motion of trees to wind filed in the natural environment, this paper proposes a method to establish real-time animation visualization of trees in the wind. The research focus is making the process of performance of ranches swaying motion become more real, layered modeling was carried out on the branches and combining the theory of fractal iteration for simulation, making the effect of wind field on the branches can carry on the hierarchical structure to analysis and calculation in detailed, so as to achieve good swing results. This paper implements a dynamic simulation demonstration system of trees in the wind based on fractal iteration system to be consistent with branches in the wind with the nature of the scene. Therefore it can generate both satisfied visual effects and dynamic images that meet the real-time requirements.

Drones in flight make a variety of vibration frequencies. Therefore, gimbal system is needed to get clean images from drone-mounted cameras. The system consists of two things: one is a structure to support a camera module, and another is a stabilizer to block outside vibrations and keep the right angle. The purpose of this paper focuses on the system's dynamics model and the application of a traditional PID controller. Furthermore, the paper compares the traditional PID and intelligent-PID without any dynamics model through the simulation made of MATLAB/Simulink.