Advanced Materials Research Submitted: 2014-05-28 ISSN: 1662-8985, Vols. 989-994, pp 3335-3339 Accepted: 2014-05-30 doi:10.4028/www.scientific.net/amr.989-994.3335 Online: 2014-07-16 2014 Trans Tech Publications, Switzerland An Analysis of Electric Inertia Simulation Method On The Test Platform of Electric Bicycle Brake Force Zhaoxu Yu 1,a, Hongbin Yu 2,b 1,2 School of Mechanical Engineering, Tianjin Polytechnic University, Tianjin, China, 300387 a 836665408@qq.com, b hongbinyu@aliyun.com Keywords: Electric bicycle brake force; Electric inertia simulation; Test platform Abstract. This paper analyzes the electric inertia simulation method deeply. By analyzing the brake torgue in the braking process, this paper makes a conclusion about the relationship between the moter s torgue in the braking process and the simulation of inertia. The test uses the method of combining the mechanical simulation and electrical simulation. In this method, it invites the test platform of electric bicycle brake force, and realizes the inertia simulation. On the test platform, the results showed: by using the electric inertia simulation, the performance of the system is obviously better than the one on the test platform which using flywheel groups. This method improves the degree of automation on the test platform. Introduction As the call of low carbon and environmental protection, National restrictions on private cars, the utilization rate of Electric bicycle is higher and higher. Safety requirements for electric bicycles will be too high as well. Therefore the braking performance requirements are very high. Brake manufacturer needs to perform various quality inspection and comprehensive evaluation of performance of the brake [1]. The ways to evaluate braking performance of electric bicycle are usually divided into three categories: (l)obtaining data of Electric bicycle in the practical road test to evaluate the electric bicycle brake performance. This can truly reflect the braking performance of electric bicycle. (2)Set the electric bicycle brake force test platform of electric bicycle brake function of various parameters related. In the process of test, Take the different experimental methods according to the different test items test platform. To simulate a variety of road conditions of various parameter data and the electric bicycle brake performance assessment. (3)Mathematical models are established according to the various test parameters. Simulation of dynamic process of electric bicycle braking simulation method by use of computer, then evaluating electric bicycle braking performance through the simulation data. At present, brake bench test platform is commonly used as the traditional mechanical method. Through the rotary inertia large inertia wheel to simulate the mechanical inertia electric bicycle in motion process. But the torgue of inertia can hardly be continuously adjusted in the large inertia, and manufacturing cost is higher and not convenient to install. In view of the problems, with the design idea to develop an electric inertia simulation of mechanical inertia of the electric bicycle brake performance testing platform. According to certain control algorithm by motor output torque and rotational speed to simulate the mechanical inertia. Such devices occupy less space and money, and it can be continuously adjusted and convenient debugging. Firstly, the traditional mechanical inertia simulation methods are briefly introduced. Then according to the principle of electric bicycle mechanical inertia of the electric simulation technology to make up the expression of the dynamic wheel in detail. Finally design the dynamic test platform and test platform for electric simulation system. Traditional Mechanical Inertia Simulation Method The use of mechanical inertia flywheel group to simulate is widely used traditionally. Using the test platform to simulate the electric bicycle mechanical inertia fly wheel. The fly wheel is made up of All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (ID: 130.203.136.75, Pennsylvania State University, University Park, USA-06/03/16,18:49:09)
3336 Materials Science, Computer and Information Technology multiple sizes of the flywheel. The test device combines with the main rolling chassis dynamometer through the clutch [2]. By controlling the number, size of the flywheel to simulate different inertia. The method has the advantages of simple operation, but the defects are showed as follows:its quality fixed once flywheel finished, This means that a testing platform once assembled, the simulation of quality fixed, unless the flywheel replaced, otherwise it cannot realize the diversification of demand; The flywheel mass is greater, the higher requirements of design and manufacturing, This will increase the cost of the whole system; Flywheels will produce large noise and vibration in the operation process. Once a mechanical fault, it may pose a threat to the surrounding the safety of equipment and personnel; The inertia of the flywheel equipment system is huge normally, and needs higher installation accuracy, thus the installation and replacement of the flywheel will take a long time. Analyze The Technical Principle of Simulating A Electric Bicycle s Electric Inertia Instead of Mechanical Inertia The core content determination of mechanical inertia use electrical simulation technology of electric has 2 points. First, to determine the mechanical inertia of bicycle. Second, electric simulation technology need to adopt electric drive system and make precise control of output torque, because different bicycle have difference inertia. Through the different tests results of a same t bicycle o adjust the speed and acceleration of the electric bicycle in the deceleration process. The above parameters can be measured by the torque, so the core problem of electric simulation technology of mechanical inertia is the control of torque [3]. The mechanical inertia simulation is the use of inertial rotation of the flywheel stored energy, in the test bed frame simulating various models of electric bicycle of equivalent quality on the road. 2 Torgue J( kgim ) of inertia simulation test bench calculated as follows: η 2 J = (m1+ 0.071m) rk 1+ η (1) Where η is Electric bicycle wheel braking force distribution ratio before and after, m1 is the rated quality of electric bicycle, m is electric bicycle vehicle quality, rk is the wheel diameter of electric bicycle. The spindle speed of inertia test platform by the following formula n = 2.645 v / r k (2) Where v is the initial velocity of electric bicycle test. The brake is loaded in pure flywheel inertia test platform, the relationship between its braking torque and inertia fly wheel and the rotational speed is as follows: = d ω α M j = dt J (3) Where α j is the test platform frame spindle angular speed reduction. M is braking torque. ω is test platform frame spindle angular velocity. By Eqs. (3), When the torgue of inertia J unchanged, braking deceleration is only related to braking torque. So the essence of the inertia brake test is to test the deceleration of the inertial system features, and then simulate the process of electric bicycle brake to slow down. Among them, torgue of inertia J is only for storing kinetic energy. If replace fly wheel stored kinetic energy with motor output energy, and keep the relationship between braking torque and speed reduction, can be used for simulating the mechanical inertia, called electrical inertia simulation. Electric inertia simulation process can be expressed as dω M = M1 + J0 dt (4) Where M 1 is the output torque in the process of motor brake. J 0 is the mechanical inertia of test platform that Including servo motor rotor, shaft coupling, main shaft and a fixed wheel inertia. M is a measured values, and can be used as a control volume.
Advanced Materials Research Vols. 989-994 3337 By Eqs. (3), Substituting (dω/dt)=(m/j) into Eq. (4) and we can get the equation J J0 M1 = ( ) M J (5) J and J 0 are known in Eqs. (4). Therefore, the so-called electric simulation is through control the output torque of motor M 1 and make the tested brake have the same deceleration (dω/dt) with purely mechanical simulation system. In known braking deceleration (dω/dt), the relationship between the brake on the brake torque M and the output torque of the motor M 1 the total inertia J and the basic inertia J 0 as follows: When J=J 0, the mechanical inertia simulation of inertia is equal to the system, is the mechanical simulation system, the output torque of the motor is zero. When J<J 0, M 1 is negative, the motor output brake torque, the direction of torque and rotate is opposite. When J>J 0, M 1 is positive, the motor output Driving torque, the direction of torque and rotate is uniform. Electrical analog control steps are as follows. First, measure the braking torque M. Second, calculate the output torque M 1 of the motor in the brake according to Eqs.(5). Third, By D/A conversion output electric inertia means the output torque M 1 of the motor in the brake. The sampling interval from the measurement to the output is short, it depends on the calculation speed of the computer and generally no more than 50ms. A Structure Design For Braking Test Platform In order to give full play to the function of electric bicycle testing existing test platform, electric inertia test platform on the basis of existing test bench can classify the function and design. Brake test system consists of test machine and computer control system. Test system Schematic diagram of the host structure is shown in Fig. 1, it can describe electric inertia test platform of the whole machine structure. Control system structure is shown in Fig. 2. Fig. 1.Test system Schematic diagram of the host structure Fig. 2.Control system structure
3338 Materials Science, Computer and Information Technology The test system comprises a servo motor, inertia flywheel, transducer, encoder, sensor, PLC etc. In the development of the electric bicycle brake test-bed design combined with mechanical and electrical simulation method. During the test, the measured brake clamp on the test bed according to the installation as the electric bicycle. Motor drive shaft rotates, when it reaches to the speed of simulated electric bicycle. The control force is applied to the brake control force, making brake braking torque, forcing spindle stop [5]. DC speed regulating device to control the rotation of the DC motor. The encoder will dynamic speed feedback to the device and computer DC speed regulation, form a closed-loop control system. Applying pressure to the brake of the brake control force for a given organization is the pneumatic servo system controlled by computer, it can accurately simulate the brake operating force in actual driving. Test to measure the brake shoe temperature using thermocouple, thermocouple installed in the brake disc or drum brake shoe of the specified location. Brake temperature rise, and flooding after all can produce braking efficiency of the recession, it makes a strong impact on the safety performance in actual driving. So required by the test of brake blowing wind speed is accurately controlled by computer. In the water recession test, water spray for the brake can also be accurately controlled by computer. QC/T654-2005 Standard specified the test initial conditions, the braking original speed and braking deceleration, initial temperature, etc, which can be set whether the different models of the brake. A Design for Electrical Simulation System of The Test Platform When designing electric bicycle brake test bench, the first to determine the types and specifications of motor, its torque characteristics can be found from the product manual or the samples. Fig. 3 is the torque characteristic curve of the 30 kw DC motor. As can be seen from the Fig. 3, the motor base speed is 600 r/min, the maximum speed is 1500 r/min. In the base speed zone, the maximum torque that motor can output is constant, the output power linearly increase gradually, so the base speed area is known as the constant torque area;when the motor speed exceeds the base speed, the maximum output power of the motor is constant, the maximum output torque curve gradually decline, so this area is called the constant power area. And the maximum torque corresponding to a speed point is the velocity and the corresponding power point torque value, can be 9550P M1 = calculated by the formula n. (6) Substituting it into equation (5) can take: P I M = 9550 ( ) n I I0. (7) Practice proves that the combined system consisting of several additional inertia flywheel (as shown in Fig. 1), can expand the inertia simulation scope of platform. A combination of both can eliminate the differential, and reduce the test volume, improve simulation accuracy. Electric bicycle inertia of Brake test bench simulated by flywheel system. The inertia wheel system is consist of 3 inertial wheel and 2electromagnetic clutch that mounted on the spindle, the quantity of combination flywheels is one, the activity flywheels is two. The inertia wheel is selected by the computer according to the parameters of set brake and electric bicycles, at the start of the experiment through the electromagnetic clutch automatic select inertia wheel [6]. The inertia wheel simulated inertia difference by electric inertia simulation compensation. The inertia wheel simulated inertia difference shall be compensated by the differential electrical inertia simulation.
Advanced Materials Research Vols. 989-994 3339 Fig. 3.The torque characteristic curve of the DC motor The test uses the method of combining the mechanical simulation and electrical simulation. Precision of pure electric inertia simulation precision is low, and it uses Large capacity motor, Motor speed control device is of great capacity, These all will increase the cost. Simple mechanical inertia simulation requires many different inertia wheel in different combinations, and always exist analog differential, at the same time this makes the test bed volume very large. The combination of the two can eliminate the differential, reduces volume, improves the accuracy of the simulation and Save the cost. The testing system can simulate electric bicycle driving inertia in the series of 50 to 250. Conclusion The relationship between braking torque, the motor in the brake output torque and inertia simulation is given in this article through the analysis of the braking process of braking torque. The proposed method can effectively identify and optimize the mechanical inertia of the flywheel hybrid simulation system and driving motor matching relationship. Electric bicycle brake test platform that has been designed realized the simulation of inertia with the Methods of mechanical simulation and electrical simulation combined. References [1] GIULIANO A, MICHELE C. Microarray image gridding with stochastic search based approaches[j]. Image and Vision Computing, 2007, 25(2):155-163. [2] Sahoo P K, So ltani S, Wong A K C, eta. l A survey of thresholding techniques[j]. Computer Vision Graphics Image Processing, 1988, 41:233-260. [3] CHEN Jian-jun, Control to electric simulation of mechanical inertia of brake testing system[j], Hoisting and Conveying Machinery, 2007, 12, P27-30(Ch). [4] James K, A M. Inertia Simulation in Brake Dynamometer Testing, SAE Technical Paper Series, 2002. 01. 2601. [5] Michael A., Sartori and Panos J. Anteaklis,Implementation of learning control system using neural networks[j], IEEE CSM,1992 [6] James K, ThomPson, Aaron Marks, Denis Rhode. Inertia Simulation in Brake Dynamometer Testing[J]. SAE International, 2002. 10.
Materials Science, Computer and Information Technology 10.4028/www.scientific.net/AMR.989-994 An Analysis of Electric Inertia Simulation Method on the Test Platform of Electric Bicycle Brake Force 10.4028/www.scientific.net/AMR.989-994.3335 DOI References [1] GIULIANO A, MICHELE C. Microarray image gridding with stochastic search based approaches[j]. Image and Vision Computing, 2007, 25(2): 155-163. 10.1016/j.imavis.2006.01.023