SYSTEM AND METHOD FOR DETERMINING CLUTCH GAINS IN A TRANSMISSION DURING A POWER DOWNSHIFT

• US 20130245904A1
• Filed: 03/15/2012
• Published: 09/19/2013
• Est. Priority Date: 03/15/2012
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Thor, Todd J.
• Granted Patent: US 8,744,705 B2
• Time in Patent Office: Days
• US Class Current: 701/55
• CPC Class Codes: B60W 10/115 with planetary gears
• CPC Class Codes: B60W 2050/0011 Proportional Integral Differential [PID] controller
• CPC Class Codes: B60W 30/19 Improvement of gear change, e.g. by synchronisation or smoothing gear shift
• CPC Class Codes: F16D 2500/10412 Transmission line of a vehicle
• CPC Class Codes: F16D 2500/1085 Automatic transmission
• CPC Class Codes: F16D 2500/3024 Pressure
• CPC Class Codes: F16D 2500/30406 Clutch slip
• CPC Class Codes: F16D 2500/30415 Speed of the input shaft
• CPC Class Codes: F16D 2500/30421 Torque of the output shaft
• CPC Class Codes: F16D 2500/30806 Engaged transmission ratio
• CPC Class Codes: F16D 2500/70252 Clutch torque
• CPC Class Codes: F16D 2500/70276 Slip
• CPC Class Codes: F16D 2500/70406 Pressure
• CPC Class Codes: F16D 2500/70436 Input shaft speed
• CPC Class Codes: F16D 2500/70442 Output shaft speed
• CPC Class Codes: F16D 2500/70605 Adaptive correction; Modifying control system parameters, e.g. gains, constants, look-up tables
• CPC Class Codes: F16D 2500/70626 PID control
• CPC Class Codes: F16D 48/06 Control by electric or electronic means, e.g. of fluid pressure
• CPC Class Codes: F16H 2061/0078 Linear control, e.g. PID, state feedback or Kalman
• CPC Class Codes: F16H 2061/0096 using a parameter map
• CPC Class Codes: F16H 2061/0492 : for high engine torque, e.g. during acceleration or uphill driving
• CPC Class Codes: F16H 61/061 : using electric control means

Abstract

A method of controlling an offgoing clutch in a transmission during a power downshift includes detecting the downshift, reducing a pressure command to the offgoing clutch, and introducing a calibrated error value to a pressure command for the offgoing clutch during the inertia phase. The method also includes synchronizing the speed of the offgoing and an oncoming clutch during the torque phase, determining the offgoing clutch pressure and torque after synchronizing clutch speeds, and then recording a clutch gain as a function of the offgoing clutch pressure and torque. The recorded clutch gains are used to control a subsequent power downshift of the transmission. A controller using proportional-integral-derivative (PID) control logic introduces the error as PID error in a pressure control signal, and controls slip across the offgoing clutch. A transmission is also disclosed having an offgoing clutch and controller configured to execute the above method.

Claims

1. A method of controlling an offgoing clutch in an automatic transmission during a power downshift, the method comprising:

detecting initiation of the downshift;

reducing a pressure command to the offgoing clutch to a threshold level;

introducing a calibrated error value to a pressure control command for the offgoing clutch during the inertia phase of the downshift;

synchronizing the offgoing clutch speed with the oncoming clutch speed during the torque phase of the downshift;

determining the offgoing clutch pressure and offgoing clutch torque after a calibrated duration of the synchronizing of the clutch speeds;

recording a clutch gain as a function of the offgoing clutch pressure and the offgoing clutch torque; and

using the recorded clutch gain to control a subsequent power downshift of the transmission.

2. The method of claim 1, further comprising:

calculating a shift energy value; and

recording the clutch gain in a [1×

X] lookup table indexed by the calculated shift energy value.

3. The method of claim 2, wherein calculating the shift energy value occurs only during the inertia phase of the downshift.

4. The method of claim 1, further comprising:

averaging the offgoing clutch torque during the torque phase;

averaging the offgoing clutch slip speed during the torque phase; and

recording the clutch gain in a lookup table indexed by the offgoing clutch slip and the offgoing clutch torque.

5. The method of claim 1, wherein introducing a calibrated error value to a pressure control command for the offgoing clutch is conducted using proportional-integral-derivative (PID) control logic of a controller.

6. The method of claim 4, wherein synchronizing the offgoing clutch speed with the oncoming clutch speed is performed by the controller using the PID control logic.

7. A method of controlling an offgoing clutch of an automatic transmission during a power downshift, the method comprising:

detecting initiation of the downshift;

reducing a pressure command to the offgoing clutch to a threshold level;

introducing a calibrated error value to a pressure control command for the offgoing clutch via proportional-integral-derivative (PID) control logic of a transmission shift controller during the inertia phase of the downshift;

synchronizing the offgoing clutch speed with the oncoming clutch speed via the PID control logic during the torque phase of the downshift;

waiting a calibrated duration after synchronizing the offgoing and oncoming shift speeds;

determining the offgoing clutch pressure and offgoing clutch torque after the calibrated duration has elapsed;

measuring a slip speed of the offgoing clutch;

calculating a shift energy value as a function of slip speed of the offgoing clutch and torque of the offgoing clutch;

recording a clutch gain in a [1×

X] lookup table indexed by the calculated shift energy value as a function of the offgoing clutch pressure and the offgoing clutch torque; and

using the recorded clutch gain to control a subsequent downshift of the transmission.

8. The method of claim 7, wherein calculating the shift energy value occurs only during the inertia phase of the downshift.

9. The method of claim 7, further comprising:

averaging the offgoing clutch torque during the torque phase;

averaging the offgoing clutch slip speed during the torque phase; and

recording the clutch gain in another lookup table indexed by the offgoing clutch slip and the offgoing clutch torque.

10. The method of claim 9, further comprising:

calculating the clutch gain as weighted average of the recorded clutch gains from each of the tables;

wherein using the recorded clutch gain includes using the calculated clutch gain.

11. An automatic transmission comprising:

a clutch that is used as an offgoing clutch during a downshift; and

a controller in communication with the clutch;

wherein the controller includes proportional-integral-derivative (PID) control logic and is configured to;

detect initiation of the downshift;

reduce a pressure command to the offgoing clutch to threshold level according to a calibrated profile;

introduce a calibrated error value, via the PID control logic, to a pressure control command for the offgoing clutch during the inertia phase of the downshift;

synchronize the offgoing clutch speed with the oncoming clutch speed during the torque phase of the downshift;

wait a calibrated duration after synchronizing the offgoing and oncoming shift speeds;

determine the offgoing clutch pressure and offgoing clutch torque after the calibrated duration has elapsed;

record a clutch gain as a function of the offgoing clutch pressure and the offgoing clutch torque; and

use the recorded clutch gain to control a subsequent downshift of the transmission.

12. The vehicle of claim 11, wherein the controller is further configured to:

calculate a shift energy value; and

record the clutch gain in a [1×

X] lookup table indexed by the calculated shift energy value.

13. The vehicle of claim 12, wherein the controller is configured to calculate the shift energy value only during the inertia phase of the downshift.

14. The vehicle of claim 11, wherein the controller is configured to:

average the offgoing clutch torque during the torque phase;

average the offgoing clutch slip speed during the torque phase; and

record the clutch gain in a lookup table indexed by the offgoing clutch slip and the offgoing clutch torque.

15. The transmission of claim 11, wherein the transmission is one of a 6-speed transmission and an 8-speed transmission.