Adaptive Control Strategy

Adaptive Control Strategy (previously named Real-Time Control Strategy)

Role of subsystem in vehicle
The Adaptive Control Strategy (ACS) for a parallel hybrid considers both fuel economy and emissions in its choice of operating points. ACS attempts to optimize at each time step the torque distribution between the electric motor and the engine

Description of modeling approach
Over the valid range of operating torques, ACS normalizes five competing metrics (energy use, HC, CO, NOx, and PM emissions) by using user- and standards-based weightings of time-averaged fuel economy and emissions performance determine an overall impact function. The Adaptive Control Strategy has the following characteristics:

The instantaneous efficiencies of the engine, exhaust removal, motor, and batteries are all included in the vehicle optimization.
The ACS adjusts its behavior based on driving conditions: e.g. engine, motor and battery temperatures and amount of available regenerative braking. The amount of ‘free regenerative energy’ is calculated as the vehicle drives.
There are user-definable fuel economy and emissions targets.
For each operating point (e.g. a given speed), ACS looks at all the entire range of possible motor-engine torque combinations to determine optimum operation point.
Performance is weighted sum of instantaneous mpg and g/mi by minimizing Impact Function.

The ACS calculations follow the 6-step path described in the figure below.

A sample Impact function is shown below.

For detailed information on the implementation, see the paper and presentation presented at FutureCar Congress (April, 2000).

Variables used in subsystem
There are 13 variables that determine the operation of the Adaptive Control Strategy.

**Adaptive Control Strategy Variables**
Variable	Description
cs_hi_soc	highest desired battery state of charge
cs_lo_soc	lowest desired battery state of charge
cs_soc_range	SOC index for cs_scale_factor
cs_scale_factor	Scale factor by which to multiply electrical energy cost. Allows for SOC balancing
cs_regen_avg_time	Averaging time for looking at free regenerative braking
cs_mph_avg_time	Averaging time for looking at vehicle speed (which is used in determining operating performance with respect to desired metrics)
K_Energy	Weight for energy usage, cannot be zero, may be >=1
K_Emis	Weight for emissions [HC CO NOx PM] in picking operating point. 0=ignore that emission, >0(e.g. 1)=include analysis of that emission
mpg_desired	Desired fuel economy (affects weighting in the performance function)
hc_desired	Desired HC emissions
co_desired	Desired CO emissions
nox_desired	Desired NOx emissions
pm_desired	Desired PM emissions

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Last Revised: 02/08/01:VHJ