GM Research and Development CenterZ. Sun and K. Hebbale
Automotive Transmission Control and Driveline Dynamics
Zongxuan Sun and Kumar Hebbale
Research and Development CenterGeneral Motors Corporation
GM Research and Development CenterZ. Sun and K. Hebbale
Automotive Transmission Technologies
• Step gear automatic transmission
• Manual transmission
• Starting clutch/friction launch transmission
• Automated manual transmission
• Continuously variable transmission
• Electrical variable transmission
GM Research and Development CenterZ. Sun and K. Hebbale
Step Gear Automatic Transmission
• Increasing number of speeds• Migrate to clutch to clutch shift
4 Speed Transmission 6 Speed Transmission
Torque ConverterClutch
Planetary Gear SetClutchesTorque Converter
GM Research and Development CenterZ. Sun and K. Hebbale
Starting Clutch/Friction Launch Transmission
• For better fuel economy and possible lower cost, a starting clutch is used to replace the torque converter
• Clutch slip control is critical to achieve desirable drivability
)(PfVslip =
),( PfT µ= TorqueT : tcoefficienFriction:µ
speedSlipVslip : P:Pressure
GM Research and Development CenterZ. Sun and K. Hebbale
Continuously Variable Transmission
• Better fuel economy and drivability
• Unique actuation challenges– Belt drive CVT– Chain drive CVT– Toroidal drive CVT
• Control challenges: enable fast and smooth ratio change while maintain required torque capacity
GM Research and Development CenterZ. Sun and K. Hebbale
Electrical Variable Transmission
• New transmission for hybrid electrical vehicles
• Better fuel economy and emission
• Potential control challenges
• Coordination between engine, motor and generator
• Power recirculation issues• Smooth shift
PlanetaryGear Set
Engine
Motor
Generator
Vehicle
Two Mode Hybrid Transmission
OutputEngine
Motor/Gen
Motor/Gen
PlanetaryGear Set
PlanetaryGear Set
GM Research and Development CenterZ. Sun and K. Hebbale
Clutch Fill Control
• The fill process
• Over fill and under fill
• Potential remedies
P is to n
R e tu rn S p rin g
C lu tc h P a c kH y d ra u lic F lu id In le t
P is to n
R e tu rn S p rin g
C lu tc h P a c kH y d ra u lic F lu id In le t
Oncoming Clutch Pressure Command
Commanded Fill Time
Under fill
Fill Pressure Command LevelShift Pressure
Correct fill
Over fill
Oncoming Clutch Pressure Command
Commanded Fill Time
Under fill
Fill Pressure Command LevelShift Pressure
Correct fill
Over fill
GM Research and Development CenterZ. Sun and K. Hebbale
Effect of Clutch Over Fill on Upshift
Power-On Upshift
0
100
200
300
400
500
600
700
3.5 4 4.5 5 5.5 6Time (s)
0
300
600
900
1200
1500
1800
2100
Engine Speed
Output Torque
Offgoing Pressure
Oncoming Pressurecommand & actual
GM Research and Development CenterZ. Sun and K. Hebbale
Clutch Slip Control
Objective: To reduce fuel consumption and provide driveline damping by clutch slip control
Clutch slip control is essential for many different transmissiontechnologies:
• Starting clutch/Friction launch
• Dual clutch transmission
• Electrical converter clutch control (ECCC)
CB1R
C456
C1234
C35R CB26
F1
S1
S2S3
Out
R12R3
In
Friction Launch Clutch
Engine To Vehicle
GM Research and Development CenterZ. Sun and K. Hebbale
Effect of Clutch Slip Control
Upshift with No Control Damping
0
100
200
300
400
500
600
700
4.5 5 5.5 6 6.5 7
Time (s)
0
300
600
900
1200
1500
1800
2100
Engine Speed
Output Torque
Upshift with Control Damping
0
100
200
300
400
500
600
700
6 6.5 7 7.5 8 8.5
Time (s)
0
300
600
900
1200
1500
1800
2100
Engine Speed
Output Torque
Oncoming Pressure
Offgoing Pressure
Oncoming Pressure
Offgoing Pressure
GM Research and Development CenterZ. Sun and K. Hebbale
Transmission Control Calibration
• Challenge: number of calibration variables goes up quickly with more gear ratios and new powertrain features
• Approaches: systematic approach for calibration
– Automated tuning
– Model based control
– Adaptive learning
• Issues: complexity vs robustness
– Non-model based control: compatible with traditional calibration process, but may not reduce the complexity drastically.
– Model based control: greatly reduce or potentially eliminate thecalibration complexity, but system robustness highly depends on the fidelity of the model
GM Research and Development CenterZ. Sun and K. Hebbale
Shift Schedule
• Objective: Optimize the fuel economy while maintaining drivability
• Traditional way of scheduling shifts– Throttle angle– Vehicle speed
• New trend in shift scheduling– Shift business avoidance– Dynamic programming, fuzzy
logic, learning control
Signals from Navigation System
Sensor Signals
Fuzzy Logic Gear Shift Scheduling
Preview Information
Vehicle Motion
Driver Intervention
GM Research and Development CenterZ. Sun and K. Hebbale
Hardware Development
• Sensing level– Torque sensor– Pressure sensor
• Actuation level– Fast hydraulic control valve– Alternative clutch actuation device
• System level– Mechatronic transmission (gear-
box integrated electronics)
GM Research and Development CenterZ. Sun and K. Hebbale
Alternative Clutch Actuation Device
• Electrical motor driven clutch actuation– Require some type of gearing– Limited power density
• Smart material based clutch actuation– Electrorheological (ER) and
magnetorheological (MR) material based clutch
– Torque capacity and durability
Objective: To replace the electro-hydraulic clutch actuation system
Benefits: Reduced fuel consumption and enhanced clutch controllability and bandwidth
InputOutput
Gap
Coil
GM Research and Development CenterZ. Sun and K. Hebbale
Transmission Control and Driveline Dynamics
Potential sources for exciting driveline resonance:
• The engine dynamics: Disturbance from engine torque• The road condition
Objective: Improve fuel economy while maintaining good drivability
GM Research and Development CenterZ. Sun and K. Hebbale
System Block Diagram
Control objective:
• Damp out the driveline resonances• Shape the toque transmitted to the vehicle
Engine ActuationDevice
Gear Box Vehicle
eT
cT
lT
ew tw
Control Variable
Potential Disturbance
Potential Disturbance
GM Research and Development CenterZ. Sun and K. Hebbale
Controllability of the System
ceee TTwJ −=�
lctt TTwJ −=�
ex θ=1 ewx =2 tx θ=3 twx =4
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the controllability matrix is:
which is not full rank.
If the only control variable is cT
This means one can not control both engine speed and transmission speed by controlling the clutch alone.
GM Research and Development CenterZ. Sun and K. Hebbale
Controllability of the System (cont’d)
This means one can control the slip across the clutch by controlling the clutch alone.
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Define
we then have:
If the control variable is the controllability matrix is:
which is full rank.
cT
GM Research and Development CenterZ. Sun and K. Hebbale
System Block Diagram
Engine ActuationDevice
Gear Box Vehicle
eT
cT
lT
ew tw
Controller
Control objective:
• Damp out the driveline resonances• Shape the toque transmitted to the vehicle
GM Research and Development CenterZ. Sun and K. Hebbale
Control Design Challenges
• Nonlinearity of the actuation device
• Time varying nature of the input and output disturbances
• System robustness requirement
GM Research and Development CenterZ. Sun and K. Hebbale
Hardware Design Challenges
• Torque capacity
• Bandwidth requirement
• Sensors
• Cost
GM Research and Development CenterZ. Sun and K. Hebbale
Frequency Domain Based Control Design
Control objective:• Damp out the driveline resonances• Shape the torque transmitted to the vehicle
)(1 outinnotchc wwHHT −=
notchH
1H used to shape the transmitted torque
used to damp the resonance
GM Research and Development CenterZ. Sun and K. Hebbale
Summary
Key drivers for automotive transmission development:
• Fuel economy and emission• Market trend• Cost
Research and development in both control design methodology and hardware are needed to further advance the automotive transmission technology