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Simulating a Hybrid Drive

Application Area

In a hybrid electric vehicle (HEV), a conventional internal combustion engine is combined with electric motors in one propulsion system. The HIL test system for the propulsion control performs combined simulation of a combustion engine, electric motors, and transmission to represent the longitudinal dynamics of a hybrid drive.

All torques, one for each drive, are computed from the ECU signals and then coupled via a transmission model to form a single drive torque. This loose form of coupling has the advantage that the submodels are computed on separate processor boards, so that real-time conditions can be achieved for each ECU independently.

Important Aspects

Electric motors can reach 90% of their maximum torque in only a few milliseconds, necessitating a very high sampling rate. Thus, typical ECUs for electric machines have cycle times of approx. 60 to 200 microseconds. This requires a precise data acquisition and turnaround time for the model of the electric machines that is far less than approx. 60 microseconds.

dSPACE Solutions

The throughput time for simulating an electric motor and its associated I/O signals on a dSPACE Processor Board is typically less than 15 microseconds. This speed is achieved in conjunction with fast I/O computing components such as the dSPACE DS5202 EMH Solution, which has been optimized for this application area. The motor angle and the required current are determined in the electric motor model and fed back to the ECUs via the DS5202 EMH Solution. Unlike the simulators for combustion engines, the electric motor simulators do not fetch the signals from the actual connections to the drive electronics. Instead, the control loop is closed directly via the control signals of the power electronics. This avoids having to run the entire real-time model at a high sample rate and also reduces computational effort.

With the dSPACE HIL simulator, different hybrid powertrain configurations can be set up, for example:

  • Micro hybrid (starter/generator)
  • Mild hybrid
  • Full hybrid

As well as

  • Parallel hybrid
  • Serial hybrid
  • Power split hybrid

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