The THE EFFECT OF HUMID TROPICAL CLIMATE ON FRICTION CHARACTERISTIC OF PNEUMATIC CYLINDERS

The pneumatic cylinder is influenced by many various factors at work, including the climate environment. The climatic environment consists of two characteristic factors as temperature (T) and relative humidity (RH), which change according to seasons and different geographical regions. Therefore, changing the climate characteristic factors will affect the friction characteristic of pneumatic cylinders when operating at different speeds. This article presents empirical research on the simultaneous effects of temperature and relative humidity of the environment with the humid tropical climate in Vietnam on the pneumatic cylinder's friction properties. According to experimental planning, the studies were conducted on industrial pneumatic cylinders with two input factors: the temperature of 150C, 320C and 490C and relative humidity of 51%, 75% and 99%, with velocities of 30, 50 and 100 mm/s. The results show that the static friction force and dynamic friction decrease when T, RH increases, and the influence of air relative humidity on friction force is more significant than temperature. The experiment also gives an empirical regression equation on the relationship of friction in the pneumatic cylinder, depending on the two factors of temperature and relative humidity of the humid tropical climate in Vietnam with velocities of 30, 50 and 100 mm/s.

Mathematical modelling of transients in the electric drive of the turnout of the mono-sleeper type with switched-inductor motor

Introduction. The study is devoted to the development of the functionality of a railway track switch by introducing a switched-inductor electric drive. This solution justifies simplifying the mechanical part of the switches by changing the gearbox to a ball-screw and locating the all kinematic line of the switches on the mono-sleeper type. Goal. A study of the mono-sleeper turnout type behaviour to meet modern traffic safety requirements and improve operational reliability factors. Methodology. Based on electric drive theory, a kinematic line of a mono-switch turnout type with nonlinear friction characteristic is presented. Using differential equation theory and Laplace transformation, a mathematic description of a four-phase switched-inductor motor with ball-screw in a mechanical line of a single-mass electromechanical system has been made. A simulation mathematical model of the electric drive of mono-sleeper turnout type as the control system with a switched-inductor motor and nonlinear friction characteristic was built in MATLAB. Results. Simulation modelling of a mathematical model of a mono-sleeper turnout type with a switched-inductor motor and ball-screw gear has been developed and implemented. Studies of dynamics of turnout point movement have shown that, in contrast to the motors used today, the switched-inductor motor makes it possible to simplify the mechanical part of the drive, which leads to reduced time spent on laying and maintenance of turnout points, and therefore makes the design more reliable. The application of PID controller and fuzzy speed controller has shown improved dynamics of turnout point, while the fuzzy PID controller provides better performance of the set values and turnout point movements. Originality. First developed a mathematical model of the electric drive of the mono-sleeper turnout type, taking into account nonlinear friction characteristic, as an object of speed control of turnout point movement, is developed. Practical value. The developed mathematical model of a railway track turnout of the mono-sleeper type with a switched-inductor motor and ball-screw gear enables more efficient use of a microprocessor control system, creation of promising electric motor protection means and control of a turnout point.

Investigation of longitudinal friction characteristics of an omnidirectional wheel via LuGre model

SUMMARY In recent years, omnidirectional wheels have found more applications in the design of automated guided vehicles (AGV). In this work, LuGre friction model is used for an omnidirectional wheel. A test setup that includes a single omnidirectional wheel is designed and constructed to identify the model parameters. With the help of the constructed test setup, the longitudinal friction characteristic of the omnidirectional wheel is obtained, and the model is verified via validation tests. In addition, for the first time, the effect of lateral frictional force on longitudinal motion is examined for an omnidirectional wheel through experiments.

Analysis of the vertical moving table type broaching machine

Broaching is a type of machining that uses a toothed tool similar to a saw. There are several types of broaching machines includes linear broaching machines and hydraulic machines. Early linear broaching machines were driven mechanically by screws. However, hydraulic machines are faster, smoother in operation, and allow for high-speed steel broaches to be used. The purpose of this study is to an analysis of the vertical moving table type in the broaching machine. In this study, finite element analysis was carried out to examine the structural characteristics of broaching machine design. A model was created in CATIA software and analyzed with ANSYS to find the structural characteristics. The friction characteristic of PBT-40 material was also investigated. This material is recommended for guide rail surface lamination to reduce the friction coefficient and ram body wear. The simulation results provide information for the next step of development before physical prototype will be made. The maximum deformation of the workpiece table was 0.0517 mm on the positive Z-axis, and the maximum deformation on the pulling head device was 0.0598 mm on the negative Z-axis. The friction coefficients were between 0.013 and 0.047 in the sliding speed range of 0.06 to 0.34 m/s. The PBT-40 material has a wear coefficient of 1.604x10-13 m3/Nm according to the test. From the ANSYS friction simulation, it can be concluded that the PBT-40 material would not easily wear out during operation of the machine. It can be seen that small frictional stress occurred on the surface ranging from 8.273x10-5 to 8.381x10-5 MPa.