www.seipub.org/ve Vehicle Engineering (VE), Volume 3, 2015 doi: 10.14355/ve.2015.03.004
Multimodal Braking System Based on Deceleration Control Wu Mengling*1, Zhu Lu2, Wang Xiaodong3 1. Institute of Rail Transit, Tongji University, Shanghai 201804, China; 2. CSR QINGDAO SIFANG CO., LTD., Qingdao 266111, China *1
wuml_sh@163.com; 2tczhulu@hotmail.com; 3sf‐wangxiaodong@cqsf.com
Abstract This paper proposes a “Multimodal Braking System based on Deceleration Control” with deceleration as braking control objective, including dynamic brake, permanent magnetic track brake and electro‐pneumatic brake. Respectively, the validity of permanent magnetic track brake and deceleration control is analyzed in detail. The result shows permanent magnet track brake can achieve multilevel control by changing the angle of magnetic axis so that service braking can be realized, which can provide the deceleration of 0.56m/s2; compared with the traditional braking system, the steady‐state error of braking system based on deceleration control is less than 0.062m/s2. Keywords Deceleration Control; Permanent Magnetic Track Brake; Braking System;
Introduction Traditional braking system is composed of air brakes and dynamic brakes, whose braking capacity cannot meet braking requirements of high‐speed train due to the fact that it will decrease with the increase of train speed[1,2]. Therefore, the non‐adhesion braking emerges, such as Eddy‐current Brake is applied on Japan’s Shinkansen series 100, 300 and 700; Linear Magnetic Track Brake is applied on Germany series ICE1 and ICE2; and Eddy Current Brake is applied on ICE3[3]. However, eddy‐current brake and linear magnetic track brake need large amounts of electricity to generate the excitation current[4], while the magnetic track brake can switch to working state without any energy. To realize the multicontrol of permanent magnet track brake, this paper proposes to use servomechanism to control the rotation angle of magnetic axis so that it can be coordinated with electro‐pneumatic brake for service braking. In addition, without accounting for uncertainties in the traditional braking control mode, difference between the actual deceleration and target deceleration is too large to ensure the utilization rate of braking force. Therefore, it is necessary to develop a new type of braking system, which can make use of non‐adhesion brakes and adopt its new control mode and can enhance adaptability of uncertainties. Control of braking system refers to keeping track of braking state variables, including deceleration, velocity and displacement[5,6]. Nankyo has certain impact on the study of tracking of train deceleration[7,8]. However, their theories are based on linear system which does not consider the influence of uncertainties. According to deceleration control proposed by Nankyo, this paper will use adaptive approach to estimate the uncertainties and improve the control accuracy. Control Logic of Multimodal Braking System Based on Deceleration Control This braking system is based on bogie control, which has two sets of control unit. Control units can be divided into two categories: the main control unit (GBCU) and the dependent control unit (SBCU). Control logic of the new braking control system is shown as below Fig.1. Firstly, the brake signal is transmitted to each train’s GBCU and decoded soon. Then the corresponding target deceleration can be calculated. Secondly, according to the axle speed, load signal and brake cylinder pressure, on working out the target braking force, GBCU sends request signal of dynamic brake and permanent magnetic brake.
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After receiving the feedback signal of electric and permanent magnetic braking force, target air braking force can be achieved. Air braking force of each bogie will be transmitted to SBCU by CAN. Receiving control signals, SBCU can achieve the actual brake cylinder pressure. Uncertainties can be updated constantly in the deceleration control mode due to the detection of brake cylinder pressure and angular velocity of each axle, so that the coherence between actual deceleration and target deceleration can be realized.
FIG.1. WORKING LOGIC OF THE BRAKING CONTROL SYSTEM
Permanent Magnetic Track Brake Linear permanent magnetic brake is consisted of brake body, wear plate, force transmission columns, rotating mechanism and suspension device. Magnetic axis rotates in the brake box under driving force from rotation mechanism, and forms a closed loop of magnetic field lines between magnetic axis and rail; attraction generated from which will create pressure between wearing plate and rail, which will create friction further for providing required braking force. Using magnetic track brakes structure of high‐speed EMU as a prototype, relationship between axis rotation angle and attraction force is analyzed through simulation by ANSOFT. Result is shown as Fig.2 (rotation angle is 0° under braking condition and turns to be 90°under releasing condition).
FIG.2 RELATIONSHIP BETWEEN AXIS ROTATION ANGLE AND ATTRACTION FORCE
From the above curve: changing the magnetic axis rotation angle can adjust the attraction force. At present, theory on precise control of rotating mechanism has been widely used in other engineering fields, thus the magnetic axis rotation angle control can also be achieved. Different from traditional model of permanent magnetic brake which is applied in emergency braking only, permanent magnetic brake can achieve multicontrol and service braking can be realized. Deceleration Control Nowadays, the main braking control modes used by high‐speed train include theoretical braking force control and speed‐adhesion control (collectively called non‐deceleration control in this paper), whose control flow diagram is
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shown as Fig. 3(a). Under this control mode, electric braking force and brake cylinder pressure can be precisely controlled, but it does not take uncertainties into consideration (usually the friction coefficient of the brake shoe is set as constant of 0.3~0.35 and gradient resistance as 0), which can lead to deviation of deceleration.
(a)
Flow diagram of non‐deceleration control
(b)
Flow diagram of deceleration control
FIG.3 FLOW DIAGRAM OF NON‐DECELERATION AND DECELERATION CONTROL
Adaptive Approach (flow diagram is shown as Fig.3(b)) used in this paper estimates the uncertainties and constantly updates value of brake cylinder pressure, thus error between actual deceleration and target deceleration could be reduced. What is different from the non‐deceleration control is that the deceleration control needs to collect data, such as the brake force and train speed, before calculating the target braking force and target brake cylinder pressure. According to these data, the value of uncertainties can be estimated constantly, so that the target braking force and target brake cylinder pressure can be calculated. Comparative braking efficiency analysis Theoretical calculation The multimodal braking system based on deceleration control not only can make full use of adhesive force, it also can improve the whole braking efficiency. It is known from basic structure of the permanent magnetic track brake that the weight of each permanent magnetic brake is 27.32kg and maximum attraction force is 73kN. Determination of the coefficient of friction is according to the empirical formula of the Soviet Experiment[9]: Dry rail: 0.19
10.8v 100 21.6v 100
Since mass of a single car is 50t, deceleration that the permanent magnetic brake can provide is defined by the following:
a
F 73000 4 10.8v 100 1.1072 (1) 3 m 50 10 27.32 4 21.6v 100
Traditional braking system takes advantage of adhesive force. Since the adhesive coefficient is one of the key parameters which can influence the braking efficiency, many countries have carried out research for it[10]. E.g. adhesive coefficient of Japan Tokaido Shinkansen is: Dry rail: 1
27.2 v 85
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Corresponded braking deceleration is defined by the following:
a1 1 * g 9.78
27.2 (2) v 85
The adhesive coefficient formula of China is: Dry rail: 2 0.0624
45.6 v 260
Corresponded braking deceleration is defined by the following:
a2 2 * g 0.6103
446.88 (3) v 260
According to the equation (1)‐(3), when v=200km/h, the deceleration is followed: a=0.566m/s2, a1=0.933m/s2, a2=1.582m/s2; when v=300km/h, the deceleration is a=0.562m/s2, a1=0.691m/s2, a2=1.408m/s2; so permanent magnetic track brake can produce the deceleration of 0.56 m/s2. Simulation and analysis To verify the efficiency of the multimodal braking system based on deceleration control, the different performance between two braking system mentioned before has been simulated by deceleration test bench when considering the influence of brake shoe friction coefficient. The test simulated two conditions compared with default value of friction coefficient. The one is 0.25 and another is 0.45, while the default value in the traditional braking system is 0.35. This test demonstrated the efficiency of deceleration control under influence of brake shoe friction coefficient. The compared result (with deceleration control or not) under smaller brake shoe friction coefficient has been given in Fig.4; and the compared result under larger brake shoe friction coefficient has been given in Fig.5.
(a) Without deceleration control (b) With deceleration control
FIG.4. CONTROL EFFECT (ACTUAL VALUE 0.25, DEFAULT VALUE 0.35)
(a)
Without deceleration control (b) With deceleration control
FIG.5. CONTROL EFFECT (ACTUAL VALUE 0.45, DEFAULT VALUE 0.35)
Through the test results, we can come to the following conclusions:
Without deceleration control, the actual deceleration is more susceptible to brake shoe coefficient so that controlling deviation will be larger (‐0.12m/s2~0.09m/s2);
With deceleration control, the actual deceleration can fulfill the follow performance, whose steady‐state error is less
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than 0.062m/s2. Conclusion Multimodal braking system based on deceleration control mainly contains permanent magnetic track brake which can be applied on service braking and deceleration control mode that considers the influence of uncertainties. A linear magnetic track brake with 27.32kg and maximum attraction force of 73kN can provide a deceleration of 0.56m/s2. Under influence of friction coefficient of brake shoe, the maximum deceleration steady‐state error is less than 0.062m/s2. REFERENCES
[1]
Zhang Jianbai, Peng Huishui, Ni Dacheng, et al. Review of high‐speed train brake technologies[J]. Locomotive Electric Drive, 2011(4):1‐4.
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Peng Huishui, Ni Dacheng. Review of high‐speed train brake technologies[A]. Symposium of the Second Railway Transportation Safety Management and Technical Equipment Seminar[C].2011.
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Liu Yuxiang, Fang Changzheng, Wan Jianbing. Technical situation and development trend of train brake system[J]. Electric Locomotives and Urban Railway Vehicles, 2014(5):1‐4.
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Dong Ximing. Working principles and characteristics of high‐speed EMU[M]. Beijing: China Railway Press, 2007,12.
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Khalil, H.K. Nonlinear systems, third edition. New Jersey: Prentice‐Hall;2002.
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Sastry, S. Nonlinear systems: analysis, stability and control. New York: Springer‐Verlag;1999.
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Nankyo, M.,Ishihara, T., Inooka, H. Feedback control of braking deceleration on railway vehicle. ASME J Dyn, Sys, Meas, Control.2006; 128(2):244‐250.
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Nankyo, M., Nakazawa, S., Nonaka, T., Yoshikawa, H. Development of a braking system equipment with deceleration feedback control. RTRI Rep.2009; 23(4):41‐46.
[9]
N.C Taryov[the former Soviet Union] written, Ren Yaoxian, Jia Jijun translated. Electrical Science[M]. Beijing: Mechanical Industry Press, 1981.
[10] Rao Zhong. Train Brake[M].Beijing: China Railway Press, 2010.2 Mengling Wu, born in 1959 in Hangzhou, Zhejiang Province, received B. Sc. Degree in 1981 and M. Sc. degree in 1988 both from former Shanghai Railway University (now Tongji University), and obtained doctor degree from Tongji University in 2006. Now, he is a professor, doctoral supervisor and the director of Braking Technology Institute, Research Institute of Rail Transit, Tongji University. His current research focuses on rail vehicle braking and security technology. He has guided more than 30 graduated students and published more than 40 papers and written some books: Structure and Design for Railway Vehicle (Beijing, China: China Railway Pulishing House, 2009), Urban Mass Transit Vehicle (Beijing, China: China Railway Pulishing House, 2000). Prof. Wu has involved in many key state‐founded researches and got the 1st class reward of National Technology Advancement and Outstanding of Science and Technology of China Railway Society. Through many years’ research and create, Prof. Wu has owned a number of patents and firstly designed Microcomputer‐based electro‐pneumatic brake system which fulfill the domestic blank. Lu Zhu, born in 1990 in Wuhan, Hubei Province, received B. Sc. degree in 2012 from Wuhan University of Science and Technology. She is currently a Ph.D. candidate in Tongji University. Her current research focuses on fault characteristic extraction technology of rail vehicle braking system. Xiaodong Wang, born in 1977 in Shanghai, China, received B. Sc. degree from former Shanghai Railway University (now Tongji University). Now he is a senior engineer in Product Development Department of CSR QINGDAO SIFANG CO., LTD.
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