Drive Testing - rte.de · subjective assessment of noise means the assignment of an evaluation to a...

RTE Akustik + Prüftechnik GmbH Gewerbestr. 26 D-76327 Pfinztal/Germany Tel. +49/721/94650-0 Fax +49/721/94650-50 www.rte.de [email protected]

Drive Testing

Noise and performance test of electric drives in production

Contents

Acoustic testing in production ...................................................................................... 2

1. Introduction .................................................................................................................. 2

2. Requirements .............................................................................................................. 3

3. Quality and quality control ............................................................................................ 3

4. Test values .................................................................................................................. 4

5. Acoustics ..................................................................................................................... 4

6. Types of noise and analysis ......................................................................................... 6

7. Sample applications ..................................................................................................... 7

Tubular drives ..................................................................................................................... 7

Electronic parking brakes .................................................................................................... 7

Gear motors ........................................................................................................................ 8

Convertible top lock ............................................................................................................ 8

8. Testing technology..................................................................................................... 10

Status: March 2010

Doc: RTE APPL NVH drive testers E-100311


Acoustic testing in production

1. Introduction

Electric motors and drives of various sizes and power ratings can be found in practically all de-

vices – beginning with miniature power drives and stepper motors in devices for the household, in

the office, in air conditioning and in cars up to industrial heavy machines.

Even in the private sector, today the customer pays increasing attention to pollution caused by

noise and perceives the noise of a device not only just as disturbing, but even fears a malfunction

or failure due to conspicuous sounds.

Integrated sound and performance testing in production can significantly improve customer satis-

faction and the data can in addition be used for the documentation of the production and devel-

opment to improve the product quality.

The purchaser always has the last word, however. Through continuous monitoring and documen-

tation of production, customer complaints can be reduced to a minimum.

Only a drive?

Today electric motors are no longer used only for the relief of workers with severe physical tasks

(drill, circular saw), but are used to improve the quality of daily life. Think, for example about your

morning routine: After being awoken by your radio alarm clock, you brush your teeth with an elec-

tric tooth brush, you possibly trim your beard with an electric razor, you blow dry your hair and

brew a cup of coffee with freshly ground beans in your new machine.

Now, the noise certainly also includes information needed by man as feedback for a proper func-

tioning of the device. So a mute vacuum cleaner makes us feel it must have low power and must

thus have a low cleaning capacity

So it is not important to create as little noise

as possible, but the right noise. Here one

speaks of “value adequate” noises.

The accompanying chart shows a "noise

corridor", which evaluates the sound as a

whole, both upwards and downwards and

thus showing characteristic distribution of

spectral composition.


2. Requirements With today's high cost pressure, automated mass pro-

duction with high volume requires computerized control,

measurement and testing technology. The reason is not

only the number of pieces or the training of the em-

ployees, but the documentation of test results and rapid

intervention in production, if repeated errors are de-

tected. Production data must be available for evaluation

at all times and under different aspects.

3. Quality and quality control

Documentation, archiving, verification, traceability - these requirements are applicable also to the

noise and vibration assessment of products. However, practical implementation is more difficult

than, for example, measuring physical quantities such as current, voltage or speed and torque. A

challenge here is less the acquisition than the selection of appropriate procedures and the evalu-

ation of the acoustic signals, since only the subjective perceptions and the assessment of the

investigators are available as a reference. The subjective assessment forms the basis for objec-

tive decision by the testing system.

If we cannot rely on the subjective evaluation as a ref-

erence, the built-in learning mode of the SONIC|TC.NVH

software provides a way of statistically creating limits

based on measurement data, acquired in the produc-

tion.


4. Test values

The following table shows the typical sizes of a comprehensive drive test:

test value meaning

high voltage testing protective conductor ground resistance

safety according to VDE 0100

speed stiffness, mounting errors

torque (load simulation) performance test

current stiffness, safety

noise, vibration assembly defects, component failure, sound quality

electronics testing e.g. hall sensors, radio controls and much more

Table 1: Test values of a comprehensive test

5. Acoustics

Basics

The acoustics deals with the description of sound fields and their phenomena (see Table 2).

Acoustics

noise generation by shock, friction or other deviations

sound propagation of structure-borne noise

sound radiation of airborne sound

sound recording sensors, ear

Table 2: Categories of acoustics

We can distinguish different types of noise (see Table 3), which are ultimately defined as elasto-

dynamic oscillations and waves in each medium.

noise types

Structure-borne noise Air-borne noise Liquid-borne noise

oscillation, vibration noise Pulsation

acceleration sensor, force sensor, nerves

microphone, ear pressure sensor, hydro-phone

Table 3: Categories of noise types


For quality control it is particularly important to assess the nature of the sound. In this context the

subjective assessment of noise means the assignment of an evaluation to a product by the hu-

man examiner because of his feeling (to hear and feel). These perceptions are subject to numer-

ous, not exactly determinable factors.

The "objective" assessment is based on acoustic sensors for different types of noise and tries to

minimize the influencing factors respectively to consider them algorithmically.

To perform an evaluation, separable characteristics also have to be found, whose values, indivi-

dually or combined, constitute the evaluation measure [Ropke, Filbert 1995].

acoustic assessment

subjective objective or metrological

• perception and evaluation (due to experience) by man

• sense of hearing

• physical and mental factors

• signal acquisition, processing and classification by a computer / ma-chine

• measured values, calculated cha-racteristics

• technical factors

advantages • recognition of complex noise

• learning new noise

• reproducibility

• documentability

• automatability

• standardization

• known assessment scale

disadvantages • no absolute evaluation

• 85% reproducibility

• 85% confidence level

• no automation

• individual assessment scale

• expenses for small batches

• necessarily identical test conditions

Table 4: Categories of noise evaluation

Noise testing in production means the evaluation of airborne sound, while the vibration analysis

of structure-borne noise signals includes both the vibration of the test piece as well as its coupling

with the surrounding structure.


Conditions

Acoustic testing can only be successfully used in industrial environments if the following condi-

tions are met and the target direction is clearly defined. This requires an accurate task analysis

and design of the entire inspection system.

For a successful sound assessment under production conditions, the influencing factors must be

minimized, and reproducible conditions have to be established in accordance with Table .

Sensors: robust, industrial, influence-poor

Test rig: vibration-isolated from environment, vibration test optimized test

item fixture

Measuring conditions: reproducible, comparable, use of meaningful values

Characteristics determination: differentiable, manageable number, meaningful

6. Types of noise and analysis

For example, the following failures will be detected with appropriate designed sensors and test

system layout by using the noise and vibration test:

type of noise description possible methods of analysis

knocking Low-frequency, periodic excitation of a structure resonant frequency

frequency band within a spectrum, kurtosis, crest factor

hum disharmonious mixture of low fre-quency, modulated components

high resolution spectrum, modulation spectrum

squeak high frequency signal, low-frequency excitation of a resonant structure

sharpness, spectrum

buzz nasal sound in the middle frequency modulation spectrum

howl fluctuating higher engine orders, low-frequency AM modulation

roughness, modulation spectrum

more…

Table 5: Examples of types of noise and possible methods of analysis

This is due, for example, to faulty installation or the use of defective parts (such as tooth mesh-

ing, steering racks with welding beads, brush errors, collector errors).


7. Sample applications

Tubular drives

After assembly, tubular motors for rolling shut-

ters and awnings are subjected to automatic

performance and noise testing. The inspection

stations are loaded manually.

A mechanical load unit is used to simulate the

load conditions during operation.

The vibration test is done parallel to the cur-

rent measurement with the help of accelera-

tion sensors.

Electronic parking brakes

The "electrical brake", which replaces today's

manually operated hand brake, simultaneous-

ly meets the ever-increasing demands on

comfort, functionality, durability and space in

the passenger compartment.

The brakes are tested for unwanted vibra-

tions with a test system SONIC|TC.NVH in the

production line. By evaluating the structure-

borne noise, a comprehensive assessment of

the resonant behavior is carried out.

In extensive engineering in collaboration be-

tween OEMs, suppliers and RTE, the basic

conditions for the optimal measurement were

determined. In the run-up, a comprehensive

series of measurements, among others, was

performed to determine the ideal sensor posi-

tion on the complex housing structure.


Gear motors

Gear motors of different types and designs

are examined on compact fixtures for perfor-

mance and vibration.

A magnetic particle brake simulates the load

conditions of the subsequent installation situ-

ation in the various operating conditions (“up”,

“down”, “open” and “close”).

During the automatic sequence, the worker

produces the next drive.

Through the concept of parallel testing and

production, the worker always has a direct

feedback about his production.

Convertible top lock

The electro-mechanical hook of a convertible

top lock is integrated in the roof and thus lo-

cated close to the driver. In this area, any

noise level is very critical.


Using a proportional valve and with the help of

a pneumatic cylinder, the load curve of the

closure motion is simulated. The resulting

sounds are recorded and analyzed.

Comparative measurements in the vehicle and

the test system support the set-up of the pa-

rameters.


8. Testing technology

SONIC|TC - Product diagnosis for production and development

The new generation of test technology with maximum application benefit. The system links the

monitoring level with the field level (“Digital Nerve System” in the context of the Microsoft initiative

“Linking Profit to Production”. The software provides an important module for modern information

and knowledge-orientated enterprises.

SONIC|TC is a powerful PC-based test system that is suitable for many products across different

industries. It is especially used for integrated testing in mass production.

At the same time, both acoustic (frequencies, levels

etc.) as well as performance properties like voltage,

current, force, displacement, etc. are measured and

evaluated. All measured values can be documented in

accordance with ISO 9000.

With its modular, adaptable design SONIC|TC perfectly

meets the requirements of different industries and

working environments. It can be used in manufacturing,

testing and laboratory and can control the test se-

quence of a manual or automatic test station.

SONIC|TC communicates with both the sensors and actuators at the field level as well as with

plant-wide systems. Particular emphasis was placed on SONIC|TC to allow the user a paramete-

rization on a large scale. He formulates and configures his own testing procedures and has all the

tools for application-specific processing available.

Functional properties

Parameter entry for products, test instructions, test processes and documents

Parameter entry for testing different product versions

Measurement values from different test benches can be collected and integrated in one

set

High flexibility through script-based control of test sequence

Calculation of characteristics

Standardized communication and process interfaces via OPC

Analysis and evaluation functions, statistical process control (SPC)

Modular system architecture is easily extendable and adaptable to customer needs

Capability characteristics

Any number of slow measurement categories through the field bus (Profibus, Ethernet...)

Up to eight fast measurement channels e. g. for acoustics

Standard PC with Windows operating system


Fields of Application

Integrated vibration and function testing of components and systems

Process information collection and interconnection

Production and product documentation

Non-destructive, 100% testing in the production cycle

electric motors

gear boxes

valves

white goods

complex components


LC|VIBRO - Acoustic signal processing for products and processes

Noise and vibrations are fast-changing signals that describe the condition of a product or process. Inexpensive, yet po-werful devices and programs of high relia-bility are required for a real-time survey and evaluation for damage detection, monitoring and for acoustic quality control, which can be used in harsh industrial en-vironments.

LC|VIBRO is an industrial signal pro-cessing system for the acoustic process and product monitoring.

LC|VIBRO operates autonomously and requires no ex-ternal control. The measurement and evaluation unit can be placed directly at the measuring point or on the mounting plate in the control cabinet. To increase the reliability, moving parts like hard disks have been avoided. The parameters and the software are stored on a Compact Flash memory card.

Parameter data can be written, read and archived by the service application. For service tasks, an external moni-tor and input devices can be directly connected via a service interface. Additional options are accessed via a remote connection.

Functional properties

acoustic signal analysis

noise and vibration monitoring

continuous measurement with monitoring of thresholds

evaluation of alarm conditions and notifications

product testing

comparison of acoustic characteristics

archiving

test data buffering and transfer to a host system

sequencing system

independent flow control and synchronization with host

data acquisition through the field bus (Profibus, Ethernet...)

up to eight fast measurement channels e. g. for acoustics

embedded platform


Capability characteristics

time domain analysis (RMS, crest factor, kurtosis etc.)

statistical methods (peak counter, threshold peak detection etc.)

frequency domain analysis (frequency spectrum, modulation spectrum)

adjustable frequency bands

equivalent continuous sound pressure level

multiple communication standards (DeviceNet, EtherNet/IP, Profibus, Ethernet (TCP/IP),

EtherCAT, RS232, digital I/O etc.)

others …

Fields of Application

monitoring of assembly operations, machine vibration and process steps

noise and vibration testing of products

condition diagnostics for machine tools and production machinery

force fitting monitoring

others …

Date post:	18-Jul-2018
Category:	Documents
Upload:	phungcong
View:	215 times
Download:	0 times

Drive Testing - rte.de · subjective assessment of noise means the assignment of an evaluation to a...

Documents