ASPECTS OF BRAKING EFFICIENCY CRITERIA FOR FREIGHT WAGONS UNDER THE LATEST RULES OF HOST 34434-18

The paper deals with the analysis of the braking efficiency criteria for freight trains formed with wagons that have increased axle load up to 294.3 kN (30 ts) when moving at speeds up to 120 km/h inclusive. Increasing the efficiency of freight trains by increasing the technical and economic performance of cars by increasing the axial load to 294.3 kN (30 ts) and train speeds up to 160 km/h led to the development of technical requirements and rules for braking systems set out in HOST 34434-18. According to the new rules and requirements, the following are accepted as criteria for the braking efficiency of freight wagons, that is, up to the maximum values of the braking distances of the freight train on the site in the specified intervals of speeds of axial loads; calculated coefficients of force of pressing of composite blocks on wheels at braking; the pressing force of the composite pads on the axis in terms of cast iron pads. The calculation of the maximum allowable value of the braking distance of the freight train is performed based on the actual pressing forces and the actual friction coefficients. The paper shows that the specific braking forces obtained using the actual pressing forces exceed the calculated specific braking forces using the calculated coefficients. Based on the above-mentioned, it is concluded that the braking efficiency criteria with reference to the maximum allowable values of the braking distances and the calculated coefficients of the pressing force have a significant discrepancy between each other. It is proposed to use the actual pressure force coefficients instead of the calculated coefficients to assess the braking efficiency of the freight train. The paper presents the permissible values of the actual force values of pressing the pads on the wheels for wagons with axial load (230.5 - 294.3) kN at speeds up to 120 km/h inclusive, for which the braking distance criterion of the freight train is observed. Key words: criterion, braking efficiency, freight train, axial load, braking distance, specific braking force, calculated coefficients, actual coefficient.

Optimal strategy of sEMG feature and measurement position for grasp force estimation

Grasp force estimation based on surface electromyography (sEMG) is essential for the dexterous control of a prosthetic hand. Nowadays, although increasing the number of sEMG measurement positions and extracting more features are common methods to increase the accuracy of grasp force estimation, it will increase the computational burden. In this paper, an approach based on analysis of variance (ANOVA) and generalized regression neural network (GRNN) for optimal measurement positions and features is proposed, with the purpose of using fewer measurement positions or features to achieve higher estimation accuracy. Firstly, we captured six channels of sEMG from subjects’ forearm and grasp force synchronously. Then, four kinds of features in time domain are extracted from each channel of sEMG. By combining different measurement position sets (MPSs) and feature set (FSs), we construct 945 data sets. These data sets are fed to GRNN to realize grasp force estimation. Normalized root mean square error (NRMS), normalized mean of absolute error (NMAE), and correlation coefficient (CC) between estimated grasp force and actual force are introduced to evaluate the performance of grasp force estimation. Finally, ANOVA and Tukey HSD testing are introduced to analyze grasp force estimation results so as to obtain the optimal measurement positions and features. We obtain the optimal MPSs for grasp force estimation when different FSs are employed, and the optimal FSs when different MPSs are utilized.

Force tracking control for electrohydraulic servo system based on adaptive neuro-fuzzy inference system (ANFIS) controller

PurposeThe purpose of this paper is to apply a intelligent algorithm to conduct the force tracking control for electrohydraulic servo system (EHSS). Specifically, the adaptive neuro-fuzzy inference system (ANFIS) is selected to improve the control performance for EHSS.Design/methodology/approachTwo types of input–output data were chosen to train the ANFIS models. The inputs are the desired and actual forces, and the output is the current. The first type is to set a sinusoidal signal for the current to produce the actual driving force, and the desired force is chosen as same as the actual force. The other type is to give a sinusoidal signal for the desired force. Under the action of the PI controller, the actual force tracks the desired force, and the current is the output of the PI controller.FindingsThe models built based on the two types of data are separately named as the ANFIS I controller and the ANFIS II controller. The results reveal that the ANFIS I controller possesses the best performance in terms of overshoot, rise time and mean absolute error and show adaptivity to different tracking conditions, including sinusoidal signal tracking and sudden change signal tracking.Originality/valueThis paper is the first time to apply the ANFIS to optimize the force tracking control for EHSS.

Problems and solutions in the operation of belt conveyors in the river port RTC Luka Leget

The paper presents a case study of gravel transshipment in RTC Luka Leget in Sremska Mitrovica, R. Serbia. Problems that led to the incorrect operation of conveyors used in the transshipment of gravel from barges to the separation plant were analyzed. They included activation the safety switch of the conveyor drive, backward movement of the material on the belt, fracture of the connection tension pulley - axle, etc. It was found that ignorance of the actual force in the conveyor belt leads to most of the problems and the need of a solution for this problem was highlighted. At the end, proposed solutions were given in order to establish the normal operation of the plant and to prevent delays in gravel transshipment.

Improving headgear wear: why force level and direction of traction matter

Summary Background Empiric data on headgear wear are scarce. The aim was to examine a possible discrepancy between the duration of wearing and force application, and whether such a difference is influenced by force level or direction of traction. Materials and methods In this retrospective analysis, 122 consecutive patients were included. All were treated with headgear (three subgroups: high-pull headgear [n = 60], cervical-pull headgear [n = 32], and high-pull headgear in combination with an activator [n = 30]) and were monitored for three successive months using an electronic module. The device recorded chronographically the measured force magnitude and temperature, allowing to differentiate between the duration of headgear wear (recorded body temperature) and actual force application (recorded force). Results For all subgroups, the average recorded force application was lower than wear time (mean inactivity during wear: 15.9 ± 22.8 minutes/night). The direction of traction significantly influenced the extent and length of wear time without force application (P < 0.001): patients with cervical-pull headgear were more prone to inactive wear time (27.7 minutes/night) than patients with high-pull headgear (13.7 minutes/night) or with headgear–activator (7.8 minutes/night). The observed inter-individual variability of inactive wear time was considerable (0–134 minutes/night). The mean applied force was highly significantly associated with inactive wear time (correlation coefficient: −0.575; P < 0.001), and force levels below 250 g seem particularly related to episodes of inactivity. Conclusions There is a clear incongruity between the duration of headgear wear and the duration of force application. Inactive wear time is influenced by the direction of traction and force level applied. Clinicians should be aware of the likelihood of periods of inactive wear time and researchers should search for options to reduce or even eliminate these periods.

Plato and Aristotle in the Academy

This chapter considers Aristotle’s criticisms of Plato. Among these are (1) Aristotle raises doubts about and rejects aspects of Plato’s theory of Forms, (2) Aristotle dismisses Plato’s soul-body dualism, and (3) Aristotle expresses severe reservations about the tenability of Plato’s political philosophy. In an effort to come to appreciate some otherwise easily overlooked problems in Plato’s theory of Forms, the chapter focuses on one of Aristotle’s criticisms of Plato, one that seems initially intended to land Plato in a straightforward and inescapable contradiction. In the process of determining the actual force of Aristotle’s criticism, it is shown that this is less straightforward than it initially appears, and that Plato need hardly be bowed before it. By understanding Aristotle’s criticisms of his teacher in the context of their mutual association in the Academy, we will thus also come to appreciate that Aristotle has much of consequence to teach us about Plato.

SIMULASI DAN EKSPERIMEN KONTROL AUTOMATIC TURRET GUN

This research presented Active Force Control (AFC) as a control method which is applied to Automatic Turret gun (ATG) in ground combat vehicles This method compares the reference force conducted by actuator with actual force of the mechanical systems that arise due to disturbances. The advantage of AFC method is its ability to handle disturbances effectively without complicated mathematical calculations. The AFC method uses Crude Approximation (CA) in the internal loop controller AFC as inertia matrix estimator as an important part in the control loop. Simulation without load on the azimuth movement shows PID controller produces the best precision with MSE of 0 degrees while RACAFC and RAC method provide MSE 0.267 degrees. In simulation on the elevation movement, the RAC method showed the best results with an estimated MSE of the targets shot of 2.42 degrees, while the PID and RACAFC method are 2.5 and 2.46 degrees. When simulation is conducted with additional load RACAFC method gives the best precision with a MSE of 0.267 and 2:46 degrees, while the PID method was 4.24 and the 10.52 degrees. RAC method produces MSE of 0.7 and 2.87 degrees. With the added load the performance of PID controller decreases. In the experiment on the constructed rig, RAC and RACAFC scheme produce smoother movement trajectory and minimum oscillation compared to the PID controller. In loaded conditions these methods are able to maintain their performance. However, these three methods can still achieve a reference point with or without load in the end of travel time

Experimental study on dynamic load measurement of a tilting mechanism of a railway vehicle using two hydraulic cylinders

A tilting train is primarily designed to achieve increased speed in a curved section without causing discomfort to passengers. Ensuring the safety of the tilting control system is one of the most important factors in such a train. This paper presents the development of a hydraulic tilting system that can measure the force in real time to find the cause of overcurrent occurring often in an actuator of a Korean tilting train. To smoothly realize tilting motion of the Korean tiling train using hydraulic actuators, the developed hydraulic tilting mechanism was designed such that synchronization control of two hydraulic cylinders installed in opposite directions was possible; furthermore, a cooling system was developed to ensure a test environment with an appropriate temperature. The actual force acting on the two hydraulic cylinders was measured and analyzed for various tilting speed of the Korean tilting train. The experimental results show that the hydraulic tilting actuator system developed for the Korean tilting train is valid. Furthermore, it is shown that two actuator loads are detected successfully acting on the hydraulic tilting system.