Instantaneous Deceleration Research Articles

A Practical Deceleration Control Method, Prototype Implementation and Test Verification for Rail Vehicles

Currently, the theoretical braking force control mode, characterized by actual deceleration as an unstable open-loop output, is the most widely used brake control mode in trains. To overcome the shortcomings of non-deceleration control modes, a deceleration control mode is proposed to realize the closed-loop control of train deceleration. First, a deceleration control algorithm based on parameter estimation was derived. Then, the deceleration control software logic was designed based on the existing braking system to meet the engineering requirements. Finally, the deceleration control algorithm was verified through a ground combination test bench with real brake control equipment and pneumatic brakes. The test results show that the deceleration control can make the actual braking deceleration of the train accurately track the target deceleration in the presence of disturbances, such as uncertain brake pad friction coefficients, line ramps, vehicle loads and braking force feedback errors, as well as their combined effects, and does not affect the original performance of the braking system. The average deceleration in the deceleration control mode is relatively stable, and the control error of instantaneous deceleration is smaller.

Validation of an elevator safety gear equipped with a clamp sliding mechanism to supress maximum instantaneous deceleration of the car

Validation of an elevator safety gear equipped with a clamp sliding mechanism to supress maximum instantaneous deceleration of the car

Investigation into the braking performance of high-speed trains in the complex braking environment of the Sichuan-Tibet Railway

The Sichuan-Tibet Railway is an east-west rapid plateau railway under construction from Chengdu to Lhasa. One of its most remarkable features is the high altitude and notable altitude fluctuations. High altitudes will result in low atmospheric pressures and temperatures. The freezing caused by low temperatures will lead to low wheel-rail adhesions. Altitude fluctuations will generate complex spatial railway tracks. To investigate the braking performance of a train in such a complex braking environment, a train spatial dynamics model, a model of a direct pneumatic brake system and a model of a braking control strategy are constructed. A comprehensive analysis model for investigating the braking performance of high-speed trains in a complex braking environment is proposed based on the constructed train spatial dynamics model, direct pneumatic brake system model and braking control strategy model. A simulation computation platform for train braking performance analysis on the Sichuan-Tibet Railway is established based on SIMPACK, AMESim, Simulink and their interfaces. The braking performance under the different altitudes, different spatial railway tracks and low adhesions are analysed in detail and summarized. Computation time are compared in different altitudes and track conditions. Computational efficiencies of the dynamic model with multi-thread parallel computation are discussed. The results indicate that an increasing altitude and the alteration of railway track conditions have a remarkable influence on the braking distance, brake cylinder pressure, instantaneous deceleration, maximum wheel-load reduction rates and maximum longitudinal impact forces of high-speed trains. The track conditions in the dynamic model have a greater impact on the computation speed. Compared to single-thread parallel computation, the computational efficiency using 2-thread parallel computation can be promoted by 22.97%. These results will provide a reference for the Sichuan-Tibet Railway design and the optimization of train braking systems.

An intelligent method for controlling the ECP braking system of a heavy-haul train

Abstract An intelligent control method is proposed for the electronically controlled pneumatic (ECP) braking system of a heavy-haul train. The gradient of the ramp is estimated using a Kalman filter in real time and the braking force is adjusted by the backstepping method, so that vehicles on different gradients change their brake pressure with the change in the gradient to keep the instantaneous deceleration of each vehicle consistent, thus reducing the longitudinal impact between vehicles. The longitudinal impact of heavy-haul trains with and without intelligent control under different gradients, initial braking speeds, loads and complex terrains are simulated and analysed. The results show that when the intelligent control is applied, each vehicle can adjust its brake pressure in time according to the change of gradient. The intelligent control method can effectively alleviate the longitudinal impact of vehicles, and the reduction rate remains greater than 40% under the influence of various factors.

A Test Facility for the Measurement of Torques at the Shaft to Seal Interface in Brush Seals

An important factor in the performance of brush seals for a wide range of gas turbine applications is the rate of wear at the seal to shaft interface, which is dependent on the contact pressure that exists between the bristles and rubbing surface. This is dependent on a variety of effects. Principally, these are the aerodynamic forces bending the bristles onto the rubbing surface, frictional effects within the bristle pack and at the backing ring that arise with the application of pressure differential, geometrical changes due to centrifugal and thermal growths, and transient differential movements of the rotor that develop in flight manoeuvres. In order to investigate the effect of these phenomena on contact pressure, a test facility has been devised in which the torque exerted by a brush seal on a rotating shaft is used as an indirect measurement of contact pressure. This has necessitated the design of a test facility in which all system torques can be fully calibrated. Consequently, a pressure balanced design has been adopted in which applied seal differential and pressure levels have a minimal effect on axial loads at the rotor bearing assembly. The primary method of torque measurement is the instantaneous deceleration of the rotor. Thus, measurements over a wide speed range are acquired with high frequency instrumentation. The means whereby small parasitic torques are evaluated and corrected is given. Results demonstrating the dependence of contact pressure on seal differential and pressure levels are presented.

Successive deceleration in Boltzmann-like traffic equations

When modeling the slowing-down process in kinetic traffic flow equations the assumption of an instantaneous deceleration is usually made. In this paper we consider a successive slowing-down process, where drivers react on traffic conditions ahead of them in a more moderate manner. From this modified interaction we derive macroscopic traffic equations. Although the present model equations seem to be rather similar to a traffic model presented recently [C. Wagner et al., Phys. Rev. E 54, 5073 (1996)], the changes result in qualitatively different behavior of the velocity variance when a traffic cluster builds up, i.e., the velocity variance decreases, whereas it increases in the preceding ``free driving region.'' This dynamical behavior is supported by empirical data and is complementary to the behavior found in former macroscopic models.

Properties of the electromagnetic field with the instantaneous acceleration of charged disks

The space-time evolution of the electromagnetic field with instantaneous acceleration of charges is considered and it is shown that it differs from that with instantaneous deceleration of charges.

Swimming Energetics of Striped Bass (Morone Saxatilis) and Bluefish (Pomatomus Saltatrix): Hydrodynamic Correlates of Locomotion and Gill Ventilation

ABSTRACT Swimming patterns of striped bass and bluefish were monitored using a miniature accelerometer to record instantaneous acceleration and instantaneous deceleration during tail-thrusts over a wide range of swimming speeds. In addition, ventilatory excurrent flow patterns were visualized in swimming striped bass by injecting milk via a buccal catheter. Both species accomplish steady swimming with both symmetric and asymmetric thrusts; other transient swimming patterns were observed as well. Over the transition range from active branchial to ram gill ventilation, no measurable change in forward acceleration amplitude occurred with adoption of ram gill flow in both species; this can only occur if drag does not change over the ventilatory transition. From metabolic measurements and from implications about swimming drag deduced from acceleration amplitude, the cost of active ventilation just prior to adoption of ram gill ventilation was estimated to be 8-i % and 8-4% of total metabolism for striped bass and bluefish respectively. Ventilatory effluent flow patterns during cyclic ventilation in swimming striped bass induce substantial turbulence and probably boundary layer separation. Flow patterns during ram ventilation result in streamlined flow over most of the length of the fish. The results show that transfer from active to branchial to ram gill ventilation provides important hydrodynamic advantages to these fishes at cruising velocities.

Experimental Study on the Effect of Deceleration on the Vertical Sequence of Sedimentary Structures in Silty Sediments

ABSTRACT Experiments have been carried out in a circular flume in which silt-sized sediments were allowed to be deposited from a decelerating suspension current of density between 1.044 to 1.013. The sediment was first thrown into complete suspension at a high flow speed. An instantaneous deceleration caused rapid deposition of a graded bed. Depending on the rate of subsequent deceleration, various kinds of incomplete Bouma-type sequences were produced. Slow deceleration produced the following sequence (bottom upwards): graded bed-parallel laminae-ripple laminae--sinusoidal ripple laminae-suspension blanket. Moderate deceleration produced a similar sequence but without sinusoidal ripple laminae. Rapid deceleration caused deposition of a graded bed followed by parallel lami ae and topped by a suspension blanket. Very rapid deceleration produced a single graded bed with a suspension blanket on top. When the speed was decreased gradually, no graded bed was formed. Instead, the sequence produced was either, (1) upstream-dipping laminae (antidune cross-stratification)--ripple laminae-suspension blanket or, (2) parallel laminae-ripple laminae-suspension blanket. It was noted that the celerity of ripple and the upward building rate of the deposited layer were functions of the rate of deceleration. Average grain size and sorting of the deposit were also found to be affected by varying deceleration.