Page 277 - Design for Six Sigma a Roadmap for Product Development

Axiomatic Design 247

DP 2 top gear ratio
DP 3 structural characteristics
DP 4 torsional damping
DP 5 control strategy
DP 6 torque converter
The design equation can be written as 0

{ } [ 0 A 22 0 0 0 0 ][ ] (8.4)
A 11 0
0
A 13 0
FR 1
DP 1
FR 3
DP 2
0
A 31 A 32 A 33 0
DP 6
A 36
FR 2

0
0
0
A 43 A 44 0
DP 4
FR 4
A 51 0
FR 5
0
0
0
0 0 A 53 0 A 55 0 DP 3
FR 6 6
1 A 66 6
6 DP 5 6
1
where A ij is a nonzero entry (sensitivity). This equation exhibits two
serious coupling issues. These coupling issues are that FR 1 (launch per-
formance) and FR 2 (fuel economy) are coupled in DP 5 (control strategy)
and DP 6 (torque converter). Otherwise, a decoupled design formulation
results. It was concluded that these coupling issues can’t be solved in the
short term because of technological limitations. The only option is to
reduce the degree of coupling. This formulation was further decomposed
using the zigzagging process to yield the following FRs and DPs.
■ Second-level FRs
FR 1.1 engine torque multiplication at launch
FR 2.1 engine torque multiplication at cruise
FR 6.1 engine transmission decoupling
FR 6.2 engine torque multiplication
FR 4.1 engine torque filtration
FR 3.1 engine power transmission
FR 3.2 holds oil
FR 3.3 support component
FR 5.1 torque multiplication scheduling
FR 5.2 shift quality control
FR 5.3 pump pressure control
FR 5.4 converter slip control
FR 5.5 component lubrication
■ Second-level DPs
DP 1.1 low gear ratio
DP 1.2 final drive ratio
DP 1.3 transfer chain ratio
DP 1.4 torque converter ratio
DP 2.1 high gear ratio