DMecS Test Benches

Power Pack Test Benches (PPTB)

With our highly dynamic test benches realistic hardware-in-the-loop (HiL) testing of powerpacks can be conducted. Possible devices under test (DUT) include

• electro-mechanical steering systems (EPS)
• electro-hydraulic braking systems (EBKV)
• torque feedback steering systems
• wheel hub drives

A different operating mode allows for parameter identification and model validation of the DUT such as

• mechanical and electrical parameters
• torque-speed characteristic for entire speed range
• reference transfer behavior of torque/current control
• torque ripple for variety of loads and speeds

Innovative and high-performance controllers as well as highly dynamic actuators and sensors ensure the feasibility of a realistic testing environment while the modular and flexible design of the test bench setup and control offer a remarkable wide range of application. Executed on a modular dSPACE system the implementation of individual testing sequences and HiL models with possible integration into a complete vehicle model can be conducted. The components to be tested and therefore the results remain uninfluenced by the test bench dynamics.
An overview is given by PPTB Overview Presentation.

HiL Tests

An example of the application of HiL testing is given with an
EPS control unit and motor. The realistic results of the highly dynamic test are ensured by

• realistic environment of EPS motor with sophisticated model of steering system and vehicle dynamic model
• realistic parameter sets for every model
• highly dynamic torque control for HiL actuator

The development of a modular setup allows for the universal application even for the production of EPS ECUs / motors. The high performance of the power pack test bench is proven by conduction of standardized road tests with highly dynamic excitation of the EPS system.

Parameter Identification

The automated parameter identification and model validation are presented using an EPS control unit and motor. The EPS-PPTB software provides model-based algorithms to estimate unknown physical values. Automated procedures with statistically confirmed results are available for

• test bench control and measurement
• determination and evaluation of required parameters and characteristics

Identified parameters such as moment of inertia and viscous friction are used for

• control of the cutting torque
• determination of the air gap torque

That allows for the calculation of the frequency response for the torque/current control reference transfer behavior of the device under test (DUT). The torque ripple can be precisely determined even at high speeds and without disturbing test bench vibrations which enables the development and validation of torque ripple compensation.

Customer Applications

The power pack test benches developed by DMecS have been successfully applied in many customer projects for the testing of customer powerpacks. These include

• system identification of a power pack motor regarding
  the torque generation dynamic
• impact reduction of cogging torque induced torque ripple
  on torsion bar torque / drivers hand torque
• automated testing of motor for a torque feedback
  steering system
• parameter identification for differential lock actuators
  and servo drives