Regenerative Braking Testing on Dynamometer (Part 1 of 4)

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This is the first installment of a four-part article by: Kenneth Mendoza, Project Engineer, HiL Systems, Electronics in Applus IDIADA Fabio Squadrani, Senior Manager, Braking Systems in Applus IDIADA on developing a control module to simulate hybrid regenerative braking on a brake dynamometer.

TROY, Mich. — One of the key technologies used in electrified vehicles is regenerative braking, which allows recovering energy during braking phases by using the electric motor as a generator. In this function mode, energy is transferred from the motion of the wheels to an energy storage device such as a battery and hence the vehicle is decelerated. Regenerative braking has notoriously changed the design, integration and testing of braking systems. The development and integration of new testing tools oriented towards the new technology trends emerging is key.

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The main objective of this project is the development of a control module to simulate hybrid braking on a brake dynamometer. This control module must provide the core functionalities that allow performing brake applications containing regenerative component. To achieve the main objective of this project, several specific objectives need to be accomplished:

  • Regenerative Braking Capabilities Development: adapt the Inertia Simulation module to simulate hybrid braking on brake dynamometer.
  • Vehicle Testing: obtain relevant regenerative braking data from vehicle testing.
  • Validation Tests: validate the developed modules throughout the usage of the data obtained from vehicle testing.

All the stated developments are to be integrated into Applus+ IDIADA’s dbDyno brake dynamometer control system.

dbDyno Introduction

dbDyno consists of a suite of software which integrates all the necessary functions to run a Brake NVH Dynamometer test. That involves the test programming, the test execution, the data logging the data processing and the results exporting.

The above mentioned suite contains the following tools:

  • dbDyno – Control System, which consists in a series of tools for programming and executing a brake dynamometer test.
  • dbDyno – Export Tool, which provides tools for exporting the logged data as desired by the engineering team, as well as performing calculations.
  • dbDyno – Noise Tool, which allows analysing and exporting the NVH data depending on the criterion chosen by the engineering team.
Figure 1 dbDyno Software Suite

Figure 2 dbDyno Software

Inertia Simulation Development

There are two possible ways to introduce and extract energy from the brake dynamometer: in the one hand, the braking system can only extract energy and in the other hand, the electric motor which generally is used to introduce energy can also be used for extracting it. Focusing in the electric motor, the way to introduce energy into the brake dynamometer is generally by controlling the speed of the shaft, thus performing speed control: normal operation implies that before a brake application a certain speed value needs to be achieved, and the electric motor is accelerated in order to meet these requirements. This introduced energy is mainly stored in the inertia flywheels as rotational kinetic energy. During the brake application normally the motor is switched off, and the braking system transforms the rotational kinetic energy into heat until the release speed is achieved.

Figure 3 Brake Dynamometer Energy Flow

Inertia Simulation is to be used during deceleration brake applications and its principle of function is based on the regulation of the torque provided by the electric motor during the brake application either extracting or introducing energy into the dynamometer.

Conceptually when the braking system actuates on the brake dynamometer shaft which is loaded with a series of inertia flywheels, a reaction torque is generated. This reaction torque is proportional to the moment of inertia mounted on the brake dynamometer shaft. In order to compensate the difference between the values of inertia mounted on the brake dynamometer and that of the real vehicle it is required that the electric motor regulates its output torque accordingly.

It can be seen that Inertia Simulation directly depends on the control of the output torque provided by the electric motor. This statement reflects exactly what a regenerative braking system does: Regenerative braking consists in the regulation of the torque of an electric motor in order to provide a certain amount of deceleration.

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About Applus IDIADA

With more than 25 years’ experience and 2,450 engineers specializing in vehicle development, Applus IDIADA is a leading engineering company providing design, testing, engineering, and homologation services to the automotive industry worldwide.

Applus IDIADA has locations in California and Michigan, with further presence in 25 other countries, mainly in Europe and Asia.

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