2.5. OPTIMIZATION RESULTS AND ANALYSIS 19
Aggressive Style
Driving Style
Selection
Other Performance
Check
Exploration and
Optimization
Optimized
Parameters
Aggressive
Profile
SMC
Controller
Acceleration and DecelerationScenario Selection
Model Selection
Featured
Performance
Dynamic Performance
Ride Comfort
Trade Off
(acc time, brk time, energy)
ig, β, k
smc
Moderate Style
Moderate
Profile
Active
Damping
Controller
Acceleration and Deceleration
Ride Comfort, Dynamic Performance
Energy Efficiency
Trade Off
(jerk, acc time, and brk time)
ig, β, K
P
, K
I
Conservative Style
Conserv
Profile
Active
Damping
Controller
Acceleration and Deceleration
Ride Comfort, Energy Efficiency
Dynamic Performance
Trade Off
(jerk, energy)
ig, β, K
P
, K
I
+ + +
Figure 2.7: e proposed co-design optimization flow for the vehicle with three driving styles.
2.5.1 OPTIMIZATION RESULTS FOR THE AGGRESSIVE DRIVING
STYLE
Since the optimization problem under the aggressive driving style is formulated as a trade-off
between vehicle dynamic performance and energy efficiency with a much greater weight on the
side of dynamic performance, during optimization the interactive effects of the values of the
SMC gain, the gear ratio, and BFD on the dynamic performance of 0–50 km/h acceleration
and regenerated braking energy are explored.
According to the exploration results shown in the subplots (a) and (b) of Fig. 2.8, the
positive gain K of the SMC controller tends to be small, while the gear ratio prefers a larger
value in favor of a better acceleration performance. For the regenerative braking performance,
the variation of the gear ratio barely affects the overall regenerated energy, although BFD needs
to select a smaller value to reach a higher efficiency according to the exploration results. is is
due to the fact that more braking torque demand will be distributed to the front axle, which is
the driven axle, indicating a larger proportion taken up by the regenerative braking among the
overall braking torque.
2.5.2 OPTIMIZATION RESULTS OF THE MODERATE DRIVING STYLE
Based on the multiple optimization objectives under the moderate driving style, the trade-off
between ride comfort and acceleration performance is considered. Taking the exploration sce-
nario under a fixed value of the gear ratio at 8.3 as an example, and according to the results
shown in the subplots (c) and (d) of Fig. 2.8, the selection of the gains in the linear PI con-
troller for active damping has a great impact on the control performance of the vehicle jerk.
With selection of K
P
and K
I
at 1.5 and 3.0, respectively, the maximum vehicle jerk during a
50–0 km/h deceleration process is over 10.0 m/s
3
. While setting the two parameters to 0.5 and
2.0, the maximum jerk can be reduced to about 8.0 m/s
3
, improving ride comfort effectively.
20 2. CO-DESIGN OPTIMIZATION FOR CYBER-PHYSICAL VEHICLE SYSTEM
0–50 km/h Acc Time (S)
Regenerated Energy (J)
Max Vehicle Jerk (m/s
3
)
Acceleration Time (s)
Maximum Jerk (m/s
3
)
Regenerated Energy (J)
SMC
K
K
P
(i
g
= 8.3)
(K
P
= 1.2, K
I
= 2.5)
(i
g
= 8.3)(i
g
= 8.3)
BFD
β
i
g
K
I
K
P
K
I
BFD
β
i
g
K
P
K
I
i
g
(a) (b)
(c) (d)
(e) (f )
Conservative
Moderate
Aggressive
Figure 2.8: Performance exploration results of the three driving style.
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