Content uploaded by Enwei Chen
Author content
All content in this area was uploaded by Enwei Chen on May 05, 2019
Content may be subject to copyright.
Vibration and noise analysis for a motor of pure electric vehicle
Bao Meng
1,a
,Chen Enwei
2,b
,Lu Yimin
3,c
,Liu Zhengshi,Liu Shuai
School of Mechanical and Automotive Engineer,Hefei University of Technology,Hefei,China
a
hpu1909bam@163.com,
b
cew723@163.com,
c
yimin_lu@163.com
Keywords: Pure electric vehicles, Motor, Noise, Modal, Finite element
Abstract: To control the pure electric vehicle motor’s vibration and noise, the dynamic
characteristics of the motor are analyzed. Dynamic characteristic include the natural frequency and
response characteristics of different parts of the motor’s structural member. This paper uses
three-dimensional software Pro/E modeling of the motor: By making appropriate assumptions and
equivalent treatment of the motor’s stator, rotor core and coil winding, establish the finite element
simulation model of the various components .Using the finite element analysis software Workbench
analyzes the windings and motor model modal analysis, to get natural frequency of each mode. To
make a modal analysis test, we can use hammering method done on the motor. By using real-time
signal analyzer AWA6291 make spectral analysis of the motor online, comprehensive comparative
analysis of the results and used to guide motor design.
Introduction
Currently, pure electric vehicles is mostly drove by permanent magnet motor, in some parts of
the working area, permanent magnet motor vibration may cause serious noise pollution, affect ride
comfort, and more importantly it will decrease its performance. Stator comprises a stator core and
casing mainly in close contact with an interference fit. The structure of stator is relatively complex,
its model has a great impact on the simulation results[4-5]. To simplify the analysis, early studies
generally view winding as an additional mass of the stator core, to consider the windings effects of
the motor modal. Later, it was discovered that winding kept in close contact with the stator core not
only has the effect on motor modal as added mass, but also the effect of stiffness. Therefore, the
equivalent model of the windings is very important of the stator modal calculation[3]
.
M.Benbouzid and others’ research indicates that the tightness of the stator core and a winding will
have a significant role in the natural frequency of stator structure[1-3]. The spectrum analysis of
motor’s noise and vibration can prove the correctness of modal analysis results to some extent[6].
In this paper, Pro/E software is used for the three-dimensional modeling of the motor,
establishing a simplified model of the motor’s main components. Then import the finite element
analysis software Workbench, go on modal analysis, whereby the dynamic performance of the
motor. Prototype uses hammering method to have a modal test, and get the actual natural frequency
of the motor. Finally AWA6291-based real-time signal analyzer has been used to test the motor’s
sound pressure and vibration online. Comprehensive comparison , it may guide the design of the
motor.
Finite element has been used for pure electric vehicle motors modal analysis
1.1 The finite element model of the motor structure
By simulating the whole structure of the stator structure and modal finite element, analyzing the
structural components of the motor‘s dynamic characteristics.
Advanced Materials Research Online: 2014-04-09
ISSN: 1662-8985, Vols. 915-916, pp 98-102
doi:10.4028/www.scientific.net/AMR.915-916.98
© 2014 Trans Tech Publications, Switzerland
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-17/05/16,00:12:14)
Fig. 1 Model of motor structure Fig. 2 FEM model of steel core-winding structure
1.2 The theory of modal analysis
Finite element modal analysis can reflect the structural of vibration motor theoretically, it can
detailed analysis the vibration of natural frequency of each type particularly. It provides a basis and
reference for optimize the design and improve the processing technology. The problems of actual
production the motor’s noise and vibration can also be solved.
1.3 Determine the properties of model materials
The core structure of vehicle synchronous motor is a combination of the orthotropic silicon
layers, which can not do as uniform continuous elastic body do. However it has obvious layered
structure, laminations plane direction can be considered isotropic. E is lower than silicon steel in the
direction of perpendicular to the silicon. Currently, how to select the elastic modulus of laminated
structure has not been standard clearly. According to the experience, the laminated elastic modulus
of the plane usually in the range of 1.36e11—2.15e11Pa. Normal lamination plane of elastic
modulus is difficult to value, which affected by Core is a whole piece or slice punching, laminating
coefficient, whether painted. Since the model of stator relative idealized, and windings stiffness is
not as large as the actual copper. Winding stiffness depends on the winding tankful ratio, the value
of E decided by the gap between two turns of connected winding copper wire. Motor’s shell is used
in die-cast aluminum. Shear modulus G
23
and G
13
are equal.G
12
is not the same situation, which can
be determined by orthotropic materials,G
23
and G
13
are slightly less than the silicon. Winding can be
considered as a fiber, which is a combination of wire and the insulating layer. The overall is
orthotropic, we assumed winding and the stator teeth keep in close contact when modeling, but in
fact the stiffness of windings is much lower than copper, on top of this, the issues of slot fill factor
also should take into consideration. Assuming all directions Poisson's ratio is 0.3. Material
properties are shown in Table 2.
Tab. 1
Material properties of stator
Property Steel Laminate structure Cooper Chassis Windings
ρ/(kg/
m3)
7800 6960 8900 2650 3045
E
2
=E
3
/Pa 2.058e11
2.058e11
1.2e11
2.0e11
9.5e10
E
1
/Pa 2.058e11
1.5e11
1.2e11
2.0e11
1.4e10
G
13
=G
23
/Pa 8.0e11
7.3e10
4.6e10
7.6e10
4.6e9
G
12
/Pa 8.0e10
8e10
4.6e10
7.6e10
5.4e9
ν
12
=ν
13
=ν
23
0.28 0.3 0.3 0.3 0.3
1.4 Solving and post-processing
Stator core assembly can ensure the quality of the grid by Sweep of refined mesh networks, etc.
Workbench’s build-in can be used for the complete machine smart sub-network. Then refine
locally, since the analysis of free modal, therefore do not need to add any load or boundary
conditions. Set solver can solve this issue. Finally, you need to do some processing on the graphics
to get the results style we want.
Advanced Materials Research Vols. 915-916 99
Finite element simulation results: on the left of Fig. 3 is an overall view of motor’s structure
vibration type, the right is the winding core view of the motor structure vibration type.
(a)the 2
nd
order 3
rd
order
4
th
order 5
th
order
Fig. 3 FEM results of mode shapes for the motor
1.5Analysis
During the course, motor is mainly affected by the unbalanced force of rotor and the
electromagnetic exciting force, rotor unbalance excitation force frequency range is generally 0 ~
100Hz. Electromagnetic exciting force frequency range is 0~2000Hz[8]. This paper calculated the
fourth-order modal shape, two models are corresponding to the main natural frequencies of
vibration mode and mode shapes shown in Table 3. That is, the natural frequency of the motor away
from the unbalance excitation force frequency of the motor rotor and the excitation force frequency
of the motor electromagnetic, so it will not cause resonance.
Tab. 2 Modal frequency results for the sample motor Hz
order winding core’s natural frequency motor’s natural frequency Vibration map
2 1748.9 2292.9
Fig
3 a
3 2133.2 4806.2
Fig
3 b
4 2446.7 5000.3
Fig
3 c
5 2768.3 6080.9
Fig
3 d
Motor experimental modal analysis
2.1 Experimental process
In order to verify the drive motor finite element modal analysis is correct, in this paper,
experimental modal analysis uses hammering method. Based on the suspension way of modal
experimental [16], to obtain the boundary conditions of the drive motor consisted with and finite
element, we need to use rubber rope to hung up the drive motor tested, simulate free modal analysis.
Specific experimental process diagram is as follows:
Fig 4 Test system diagram
100 Advanced Engineering Research
Take the appropriate location and number of excitation points, do some appropriate processing of
the motor at the same time (Such as removing some of the motor’s damping mechanism spring
washers, etc.), in order to obtain relatively accurate experimental data. The force hammer and the
data logger are connected with the acceleration sensor, each of the exciting force signal and the
impulse response signal is transmitted to a data logger, and then passed by the data collection
instrument into the signal analysis system. By analyzing and processing response signal, obtain the
frequency response function of each monitoring point.
2.2 Analysis
According to the pilot testing of the drive motor transfer function curves in Figure 5 and the
coherent function curve in Figure 6, we can determine the natural frequency and vibration mode of
the system. In this paper, hammering method measured mode shapes only have two order modals,
its acceleration response curve was shown below, the figure shows natural frequencies is roughly
2200Hz under 2nd order, which has little error with simulation results.
0 1000 2000 3000 4000 5000 6000
0
0.5
1
1.5
2
2.5
3
3.5
The transfer function curv e of the m otor
f Hz
a(m/s
2
)
0 1000 2000 3000 4000 5000 6000
0
0.2
0.4
0.6
0.8
1
1.2
Motor coherence function
f Hz
Real component of motor coherence function
Fig 5 The transfer function curves of the motor Fig 6 The coherence function curve of the motor
3. The noise analysis of prototype in certain operating conditions
3.1 The noise spectrum measurement of prototype
In this paper AWA6228 Real-Time Signal Analyzer was used to test the noise and vibration
spectrum of the motor online. AWA6228 type real-time signal analyzer might analysis the noise
spectrum and amplitude after installing S6291-00404. Using the microphone MPA201 measure the
sound power of the motor in the field.
Measurement the conditions of the motor when its running: speed of 6000 rev / sec，load
torque 24 N・m. The vibration and noise measurement results of the motor are as follows:
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
30
35
40
45
50
55
60
65
70
75
80
The noise spectrum of the motor(4000r/min)
f Hz
dB
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
0
1
2
3
4
5
6
The vibration response plot (4000r/min)
Hz
m/s
2
Fig 7 The noise spectrum of the motor Fig 8 The vibration response plot.
By testing the noise characteristics of the motor, the noise of the motor is common, which can
be found at the start-up phase. The noise has a significantly increasing nearing 6,000 rpm. The chart
shows the vibration response it has a severe vibration when the motor start up to 2000 rpm.
Advanced Materials Research Vols. 915-916 101
Followed by an obvious vibration fitfully, and weak vibration when running smoothly. It indicates
that the motor occurred resonance in these peak points, and particularly evident around 2000 rpm.
Therefore, it is necessary to take reasonable means to weaken the vibrations of the motor at these
peak points in the design of the motor
Conclusion
In this paper, an electric vehicle drive motor is used as the research object, established the
three-dimensional simulation model of the various motor’s structure components, after analysis and
experiments, the following conclusions:
(1) Simplified model of the motor and windings, using the modal analysis of the motor structure,
can accurately predict the natural frequency of motor vehicle structure;
(2) For the complex structure of the vehicle motor, it is difficult to obtain many modal shapes of
experimental modal by hammering method. This paper, using the method of noise spectrum test,
verified the prediction of the natural frequency of the motor structure is correct indirectly
Acknowledgments
This work was financially supported by the National Natural Science Foundation of China (№.
51305115) and the Fundamental Research Funds for Central Universities (2011HGQC1035).
References
[1] Tetsuya H，Katsuyuki N，Takashi Y，et al．Modeling Method of Vibration Analysis Model
for Permanent Magnet Motor Using Finite Element Analysis[C]//International Conference on
Electrical Machines and Systems．Tokyo，Japan：IEEE，2009：1-6．
[2] Benbouzid M E H，Reyne G，Derou S，et al．Finite Element Modeling of a Synchronous
Machine：Electromagnetic Forces and Mode Shapes [J]．IEEE Transactions on Magnetics，1993
，29(2)：2014-2018．
[3] Wu Jianhua. The Research of Switched Reluctance Motor Stator Modal and Natural Frequency
Based on the Physical Mode[J]．China Electrical Engineering, 2004, 24(8): 110-114.
[4] Zhang Juntang，Avoki M，Omekanda，et al．Young’s Modulus for Laminated Machine
Structures with Particular Reference to Switched Reluctance Motor Vibrations[J]．IEEE Trans. on
Industry Application，2004，40 (3):748-755．
[5] Zhang Juntang ． Vibration Analysis and Reduction in Switched Reluctance Motors[D]．Ph.
D. Thesis，Clarkson University，2002．
[6] Yoon T Y．Magnetically Induced Vibration in a Permanent-magnet Brushless DC Motor with
Symmetric Pole-slot Configuration[J] ．IEEE Transactions on Magnetics ，2005 ，41(6) ：
2173-2179．
[7] Zhang Li. Modal Analysis and Experiment [M]. Beijing: Tsinghua University Press,
2011:24-39.
[8] Zhong Yan, Ding Yan, Feng Haijun. Vibration Test for Induction Motors. CSIC. No. 704
Research Institute. (2011)05-0165-03.
102 Advanced Engineering Research
