High speed electric powertrain NVH test bench, driveline testing


High speed electric powertrain NVH test bench includes pure electric passenger vehicle (saloon car, MPVs, SUVs) reducer, passenger vehicle AT (automatic transmission), DCT (dual clutch transmission), AMT (automatic manual transmission), CVT ( continuously variable transmission) performance test, system calibration, reliability endurance test and other research and development tests.

High speed electric powertrain NVH test bench reserves passenger vehicle hybrid transmission fatigue test extension configuration, pure electric powertrain (including drive motor, reducer, differential and other components) and single motor test.

In addition, the system is also equipped with an early fault diagnosis system for the test piece early failure diagnosis and analysis. The test bench can perform early failure warning and analysis on the rotating parts of the gear and bearing of the test piece.

Small diameter permanent magnet synchronous drive dynamometer

 

Model**Rated power (kW)Rated torque (Nm)Rated speed (rpm)Max. speed (rpm)
PMSM-013156005,01320,000
PMSM-022505004,77520,000
PMSM-032834506,00516,000
PMSM-041904004,53616,000
PMSM-052504505,30510,000

** Shaft height: 132mm

 

Test bench system architecture

 

The high speed electric powertrain NVH test bench consists of the power zone, test zone and monitoring zone. The power zone is mainly composed of motor control inverter and electric control cabinet. The test zone is mainly composed of AC dynamometer, measurement sensors, AC dynamometer cooling system, tested transmission, test rig, tooling and shock absorbing installation platform. The monitoring zone is mainly composed of the main control computer and electric control cabinet.

Power zone

The frequency converter of the power zone is responsible for controlling the drive motor and the load motor of the dynamometer. The drive motor simulates the power source (motor or engine) of the transmission under test, and the load motor simulates the road load. When the drive motor is used as the speed control, it is generally in the electric state, and the load motor is in the power generation state. The electric energy generated by the load motor passes through the DC bus of the inverter and is fed back to the drive motor to form an internal electric enclosed structure. When an emergency occurs, the kinetic energy of the motor can be dissipated through the braking resistor. The drive motor and the load motor can have various control modes, and various control modes can be flexibly switched, and both drive control and load control can be performed.

 

Test zone

The test zone is used for the test of the test piece. The dynamometer in the test area can be used for speed and torque control to simulate road load. The load simulation methods include: constant torque control, road spectrum input, calculation of road spectrum and user-defined load spectrum and other methods.

Monitoring zone

The monitoring zone is composed of the main control computer, data acquisition system, sensor signal processing system, real time controller and an operation console. The main control computer and the dynamometer drive communicate via Ethernet and other communication methods to realize load simulation. The data acquisition system is responsible for the data acquisition of each sensor on the site. The data acquisition system transmits the data to the host computer in real time, and the main control computer reads the data from the real time controller in real time. The monitoring system saves, displays and performs various calculations on the data. The system monitors the vibration state of the motor under test, the test bed bearing seat and the dynamometer in real time through the vibration sensor. Once the system is abnormal, the main control computer takes corresponding measures to stop the dynamometer and the motor under test to prevent deep fault damage and record at the same time. All data before the shutdown, the user can call the analysis. The main control computer reserves 2 CAN bus interfaces to communicate with the TCU of the tested transmission. The system develops the CAN communication protocol for the user, and the user can customize the editing.

 

Test monitoring room layout rendering

 

The monitoring room is composed of the industrial computer, display, console, control cabinet, etc. and is the control center of the entire test bench. The operation console is equipped with an emergency stop button, operation buttons and indicator lights. The console is generous, mainly through software operation through the human machine interface. The frequency conversion control system is designed with an emergency stop button on the operation table, the frequency conversion cabinet and the test bench, and has an emergency stop function.

The main control cabinet is equipped with control electric appliances, which are composed of various electrical circuits. They are responsible for accepting the instructions of the industrial computer, controlling the lower computer, and feeding back the signal from the site to the upper computer. The control cabinet adopts the frame structure and is elegant.

 

 

High speed electric powertrain NVH test items

 

  • Over-speed test
  • Transmission efficiency test
  • Differential test performance test
  • Differential reliability test
  • Speed-torque characteristic test
  • Powertrain efficiency test (efficiency map, DC bidirectional power supply and power analyzer for pure electric or hybrid powertrain)
  • Speed control accuracy test (for pure electric or hybrid powertrain)
  • Torque control accuracy test (for pure electric or hybrid powertrain)
  • Speed response time test (for pure electric or hybrid powertrain)
  • Torque response time test (for pure electric or hybrid powertrain)
  • Accelerated performance test
  • Motoring operation condition test (supporting DC bidirectional power supply and power analyzer for pure electric or hybrid powertrain)
  • Power generation operation condition test (supporting DC bidirectional power supply and power analyzer for pure electric or hybrid powertrain)
  • Vibration measurement
  • Noise measurement
  • Road spectrum simulation test
  • Fatigue test
  • Dynamic sealing test

 

 

High speed electric powertrain NVH test types include

 

  • Development test, endurance test and control unit calibration of the powertrain.
  • Simulating vehicle road load. It can simulate roads (different road surfaces, curvatures and slopes) to assess the function and performance of the entire powertrain under different road conditions and driving conditions.
  • The actual road load spectrum reproduction test can run the load cycle to achieve the endurance assessment of the powertrain road load spectrum.

 

 

Overview of the system design

 

The high speed electric powertrain NVH test bench consists of the load dynamometer system, test drive motor, battery simulator, unit under test system (UUT), monitoring and protection system, measurement system and UUT cooling system.

 

  • Load dynamometer system: It consists of AC dynamometer, dynamometer inverter, etc., to provide resistance during the test.
  • Test drive motor: It is used for transmission assembly and reducer assembly test to simulate the function of the vehicle drive motor. It can also be used for motor drive system test as the load dynamometer.
  • Battery simulator: It is suitable for the structure of the integrated powertrain structure and motor drive system. It is used to simulate the function of the power battery and provide DC power to the drive motor system. It has the function of charging and discharging the power battery system.
  • Unit under test system (UUT): The motor system consisting of drive motor and motor controller (MCU), an integrated assembly consisting of drive motor, reducer and differential, or separate transmission assembly and reducer assembly.
  • Monitoring and protection system: It consists of two parts: hardware and software. The hardware part mainly consists of operation console, control computer, electrical control loop, communication loop, etc. The software part mainly consists of the dynamometer inverter, AC dynamometer, UUT, control of the cooling system, monitoring, and protection of the entire test system.
  • Measurement system: It consists of speed torque sensor, power analyzer, data acquisition and conditioning device and a series of temperature and pressure sensors. The main measurement parameters include speed torque measurement, voltage and current measurement, flow temperature and pressure measurement. The measurement system is integrated with the monitoring and protection system through the software system.
  • UUT cooling system: It consists of the water cooler and oil cooler. The main function of the water cooler is to cool the motor controller and the drive motor. The main function of the oil cooler is to cool the transmission lubricant.

 

Test drive motor

 

The test drive motor uses a high speed small permanent magnet synchronous motor with center height 132 mm and rotational inertia less than 0.1 kg.m2. The drive motor bearing is maintenance free with service life more than 20,000 hours. We can use the monitoring software for timing statistics.

 

 

Drive motor mounting base

 

The driving motor speed reaches 20,000 rpm. At the same time, in order to adapt to different center heights testings, it is required to install the driving motor conveniently with high centering precision. Therefore, the motor mounting base adopts an integrated structure, and the motor and the tested components are mounted on the same base. The installation accuracy is guaranteed.

For the driving speed 20,000 rpm, the centering accuracy needs to reach 0.01~0.03mm. Otherwise the vibration may be too hig resulting in excessive heating of the motor bearing and the test piece bearing, reducing the service life and affecting the test results.

In addition to ensuring the alignment accuracy, the dynamic balance accuracy of the driveline also needs to reach high level. For the rotating parts such as the connecting flange, G1 dynamic balance is required. After the driveline is installed, on-site dynamic balancing is required for reaching G1 level accuracy. The connection bolts on the flange need to be symmetrically weighted. The position of the bolt assembly and the flange hole must be uniquely determined after the dynamic balance in the field accordingly to avoid dynamic balance accuracy reduction after disassembly and reinstallation. The driving motor mounting base is welded with steel plate. After welding, it is subjected to stress relief annealing and machining without deformation.

The high speed bearing seat is installed at the output end of the drive motor. As the transitional support, if the motor to be tested is misaligned or malfunctions, the bearing housing can act as a buffer. However, due to the long term reliable operation of the bearing housing at high speed, there is tough requirement on bearing. At the same time, in order to prevent the shafting resonance, the structure of the bearing housing needs to undergo finite element modal analysis to optimize the structure.

 

Load motor

 

The load motor is used to simulate the vehicle road load. The load motor is cooled by air or water.

 

Load motor mounting base and movement adjustment mechanism

 

The load motor mounting base adopts a steel plate welded structure, which is subjected to stress relief annealing after welding, and then mechanically machined to prevent deformation.

The load motor mounting base can be adjusted in the front, rear, left and right directions. The adjustment mode is manual speed reducer and screw adjustment. After the adjustment is in place, it can be locked by bolts. During adjusting, user can visually check the adjustment position and distance through the ruler marking.

The output shaft side of the load motor is designed with a shaft mechanical locking device, and the locking structure is locked by a positioning pin for the differential test of the transmission.

The base of the drive motor and the load motor can be moved randomly, either as the parallel-shaft transmission test or as the cross-shaft transmission test. The test bench can be flexibly configured.

 

Tooling

 

The test bench is designed with flexible mounting tools which can be adapted to the installation of different types of test pieces, and only the intermediate transfer adapter needs to be replaced. When the test bench is installed and under commissioning, the coaxiality of the tooling hole and the output shaft of the bearing housing have already been adjusted. User only needs to replace the adapter.

 

 

Why transmission test bench is need

 

Today, the development of hybrid transmission and electric reducer vary so much, making the development process difficult to manage. More EV start-ups, more complex powertrain strategies and more interconnected systems inside vehicle requires more efficient development processes. The real electric vehicle powertrains consist mainly of motors and transmissions that are connected by mechanical components. The durability, functionality and performance of these components must be verified.

Shortening the electric vehicle development cycle can only be tested as early as possible through the test bench, rather than actual vehicle prototypes. Therefore, the available components of electric vehicles must be tested as soon as possible to improve durability, function and performance.

The transmission test bench for hybrid or electric vehicles can effectively evaluate any electric vehicle type of reducer combination without confirming the maturity of the electric vehicle motor. Both the shift quality and driving performance of hybrid or electric vehicles can be professionally tested on the reducer or transmission test bench without the need for expensive and difficult prototype vehicles.

 

 

Structure of electric vehicle reducer test bench

 

The key to the configuration of the entire transmission test bench for electric vehicle reducer, motor reduction gearbox is to replace the low inertia drive dynamometer for the original electric vehicle motor. Using DynoEquip’s drive dynamometer with small-diameter, low-inertia permanent-magnet synchronous technology can reduce the shafts center distance for reducer test applications to be as small as 132mm. This drive dynamometer is the ideal choice for harsh transmission test and simulation applications.

In transmission test bench for electric vehicle reducer or motor reduction gearbox, the drive dynamometer simulates the transient behavior of the electric vehicle motor and responds to the control unit commands. The actual load of the transmission test bench can be performed by the output dynamometer just as it is on the road for vehicle testing. This configuration can produce reproducible test results under well-known constant environmental conditions.

The high speed electric powertrain NVH test bench uses the latest developments in computing technology which are faster and more powerful, as well as the advantages of ultra-high performance permanent magnet motor technology and IGBT control. The transmission test bench can run high-resolution models at real-time speed while solving the intricate response problems of EV reducer or motor reduction gearbox specimens.

The design parameters of the driveline, suspension components or mounts can be adjusted in the model and virtual road tests performed in the reducer test stand. Using DynoEquip’s low-inertia, high-transient dynamometer, the response of the simulated vehicle model can be resolved in real-time, providing realistic time-synchronized loads for EV reducer specimens.

In addition, the true dynamometer response can be ensured by introducing HIL feedback and simulating the feedback of the real-time simulated vehicle model directly to the dynamometer control. The high torque and low inertia characteristics of the dynamometer make it ideal for the tires and tire related simulation applications such as simulation of ice cubes and uneven roads. The transmission test bench for electric vehicle reducer can provide powertrain hardware in-loop or real-time simulation tests.




Hybrid transmission test bench for engine simulation

 

Automotive drive transmission and engine technology is about to undergo its most radical change since the development of the automobile. For more than a hundred years the gasoline and diesel engine has reigned supreme. However, in a little over 20 years’ time their reign may well have come to an end.

The major car maker Volvo announced that from 2019 onwards it will only make fully electric or hybrid cars. Norway has set a target of only allowing sales of full electric or plug-in hybrid cars by 2025 – as has the Netherlands – while some federal states in Germany are looking to 2030 for a phase-out. Even India has mooted banning the sale of gasoline or diesel cars by 2030. The UK and France, meanwhile, have both unveiled plans to ban the sale of new diesel and gasoline cars by 2040.

As a consequence, this shift towards full electric or hybrid powertrains will undoubtedly impact the developers of transmission systems. Consequently, transmission test bench for hybrid vehicle engine simulation is now redoubling their efforts to ensure that they can rise to the challenge. The following hybrid transmission test bench is used for hybrid performance development tests, taking into account transmission endurance tests.

Items for hybrid transmission test bench

 

Hybrid transmission test function

  • Transmission loss without load (3-motor test bench)
  • Transmission efficiency (4-motor test bench)

 

Hybrid transmission test NVH

  • Transmission contact spot (3-motor test bench)

 

Hybrid transmission test endurance

  • Transmission gear fatigue durability (4-motor test bench)

 

Hybrid transmission test sintering

  • Transmission high-speed sintering test (4-motor test bench)
  • Transmission high-load sintering test (4-motor test bench)
  • Transmission saturated oil temperature measurement (4-motor test bench)
  • Transmission low temperature sintering test (Dynamic load under 4-motor test bench)

 

Hybrid transmission test tightness

  • Transmission dynamic seal test (3-motor test bench)

 

Differential fatigue strength

  • Differential gear meshing fatigue strength (3-motor test bench)

 

Differential sintering

  • Differential sintering test (Dynamic load under 3-motor test bench)
  • Differential sintering limit confirmation test (Dynamic load under 3-motor test bench)

 

Clutch durability

  • Clutch on-off durability (3-motor test bench)

Hybrid transmission test bench operating modes

 

  • EV mode (drive motor side as input, wheel side as loading)
  • Engine drive mode (engine side as input, wheel side as loading)
  • Parallel mode – Medium Speed (engine side as major input, drive motor side as auxiliary input, wheel side as loading)
  • Parallel mode – high speed (drive motor side as major input, engine side as auxiliary input, wheel side as loading)
  • Drive motor power generation (wheel side as input, drive motor as loading)
  • Serial mode – engine power generation (engine side as input, generator side as loading)

 

 

Hybrid transmission test bench overview

 

  • Drive motor side input dynamometer
  • Engine side input dynamometer
  • Load dynamometer x2
  • Torque sensor
  • Dynamometer inverter
  • Dynamometer base, coupling and shaft protection cover
  • Power analyzer (with current sensor)
  • Test bench host control system
  • Data acquisition system (including temperature and pressure sensors)
  • Battery simulator
  • Motor temperature control
  • Transmission temperature control

 

 

Hybrid transmission test bench host control system

 

Test parameter file configuration

  • According to requirement, manual or automatical control test bench and defining relevant test conditions

 

Test bench operation and monitoring

  • Setting related alarm limits and actions and monitoring equipment operation

 

Data acquisition and storage

  • Steady-state measurement channels not less than 300;
  • Using 3 recorders at the same time and each recorder can store 250 parameters;
  • Collecting at least 24 temperatures and at least 16 pressures

 

Device Integration and data analysis

  • Integrating motor temperature control, transmission temperature control, battery simulator

 

Communication

  • Via CAN communicating with VCU/TCU/HCU;
  • Via I/O receiving fire system alarm signal




Transmission and high speed electric powertrain NVH test


There is an increasing supply of hybrid and electric vehicles in the market, and more are being prepared for production. A common misconception among users is that the nature of the electric transmission of these vehicles is highly optimized from the beginning. In fact, this is not the case. There are still many challenges in controlling the acoustic emission of these new technologies.

The sound emitted by electromagnetic phenomena in the transmission may contain high-pitched components that are uncomfortable to the vehicle occupants. The transmission test bench for NVH testing is designed to better predict NVH performance and effectively assess potential design changes at the early stage of design. Parallel development of automotive critical transmission components (internal combustion engines, hybrid engines, reducer or transmission, etc.) requires early testing.

 

 

NVH – Noise, Vibration, and Roughness

 

NVH improvements have become an important vehicle development attribute because it is directly related to legal compliance, product quality, driving pleasure, brand image, and most importantly, customer satisfaction.

The advanced NVH test method is a prerequisite for the rapid development of today’s hybrid and electric vehicle markets to ensure that sound and vibration levels are reduced and that these front-end optimizations are enhanced beyond design, while maintaining a balance with driving performance, system and component performance.

Due to the shortened product development cycle, many automotive manufacturers and their suppliers are integrating transmission NVH testing with other development activities, including road load data collection, transmission performance testing, and calibration development.

 

 

Vibration measurement for transmission NVH testing

 

The NVH phenomenon is identified during the early development process and is effectively avoided in later standard production vehicles. These are done during the development period by loading the powertrain through the transmission test bench to effectively understand NVH conditions. With different configurations, the NVH test bench can test different forms of transmissions or reducers, including special requirements for electric drives and hybrid drives.

The transmission test bench for NVH has a modern high-tech layout. The drive motor driven by carbon fiber hollow shaft can test the most advanced coaxial transmission. In order to avoid the influence of the high-speed drive dynamometer on the measurement, the drive dynamometer is separated by air spring from the rest of the test bench. The balance quality of the high speed drive shaft is 2.5G.

 

 

Hybrid drive and electric drive system NVH test

 

The development of electric vehicles poses new challenges for NVH testing. Due to the electrical drive characteristics, the new transmission test bench for NVH requires low-vibration response, low system response at 20,000 rpm, and low noise emissions. In order to test the electric drive and hybrid drive system, the corresponding components of the electric vehicle or hybrid vehicle need to be simulated on the NVH test bench. The use of a battery simulator is also required.

 

  • Using high torque dynamometer
  • Dynamometer speed up to 20,000 rpm
  • Low noise
  • Battery simulator for input dynamometer (or tested motor)
  • Power analyzer for measuring efficiency
  • Components maintain high balance quality during operation





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