METHOD FOR CONTROLLING CREEP TORQUE OF A VEHICLE

• US 20120150384A1
• Filed: 06/21/2011
• Published: 06/14/2012
• Est. Priority Date: 12/08/2010
• Status: Active Grant

• Current Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Original Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Inventors: Jung, Jae Won, Kwon, Soon Woo, Lee, Kyu Il, Yoon, Sung Gone, Chung, Sung Jin
• Granted Patent: US 8,958,944 B2
• Time in Patent Office: Days
• US Class Current: 701/31.1
• CPC Class Codes: B60L 15/2063 for creeping
• CPC Class Codes: B60L 2240/12 Speed
• CPC Class Codes: B60L 2240/14 Acceleration
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 2240/642 Slope of road
• CPC Class Codes: B60L 2260/44 by parameter estimation
• CPC Class Codes: B60L 3/0038 relating to sensors
• CPC Class Codes: B60L 3/08 Means for preventing excessive speed of the vehicle
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2520/105 Longitudinal acceleration
• CPC Class Codes: B60W 2540/12 Brake pedal position
• CPC Class Codes: B60W 2552/15 Road slope, i.e. the inclination of a road segment in the longitudinal direction
• CPC Class Codes: B60W 2710/0666 Engine torque
• CPC Class Codes: B60W 30/18063 Creeping
• CPC Class Codes: B60W 30/18118 Hill holding
• CPC Class Codes: B60W 50/0205 Diagnosing or detecting failures; Failure detection models
• CPC Class Codes: B60W 50/029 Adapting to failures or work around with other constraints, e.g. circumvention by avoiding use of failed parts
• CPC Class Codes: B60W 50/14 Means for informing the driver, warning the driver or prompting a driver intervention
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y02T 90/16 : Information or communication technologies improving the operation of electric vehicles

Abstract

The present invention provides a technique for controlling creep torque to prevent a vehicle from rolling backward on an upward slope. In particular, a gradient of a road is calculated in real time from a detection value of a sensor and vehicle acceleration. A maximum creep torque for preventing roll-back caused by gravity according to the gradient is calculated using the gradient and vehicle information. A first creep torque reference is calculated based on the maximum creep torque and the vehicle speed. A second creep torque reference is calculated based on the maximum creep torque and the vehicle acceleration. A torque command value according to an operation state of a brake is calculated based on the first creep torque reference value and the second creep torque reference value and the gradient. In response, a torque output of a driving motor is controlled according to the calculated torque command value.

Claims

1. A method for controlling creep torque to prevent a vehicle from rolling backward on an upward slope, the method comprising:

calculating, by a controller, in real-time, a gradient of a driving road from a detection value of a sensor and vehicle acceleration;

calculating, by the controller, a maximum creep torque for preventing rolling-back caused by gravity according to the gradient using the gradient and vehicle information;

calculating, by the controller, a first creep torque reference according to a vehicle speed based on the maximum creep torque and the vehicle speed;

calculating, by the controller, a second creep torque reference according to vehicle acceleration based on the maximum creep torque and the vehicle acceleration;

calculating, by the controller, a torque command value according to an operation state of a brake based on the first creep torque reference value and the second creep torque reference value, and the gradient; and

generating, by the controller, a creep torque by controlling a torque output of a driving motor according to the calculated torque command value.

2. The method of claim 1, wherein the step of calculating the first creep torque reference value comprises calculating the first creep torque reference value from a creep torque-vehicle speed map representing a relation between the maximum creep torque and the vehicle speed.

3. The method of claim 2, wherein, in the creep torque-vehicle speed map, a creep torque increment to be applied to a vehicle speed section in which rolling-back of the vehicle occurs and a vehicle speed section to a predetermined creep medium speed in a state where the vehicle acceleration changes into a positive (+) value is set to a value according to the maximum creep torque and the vehicle speed.

4. The method of claim 1, wherein the step of calculating the second creep torque reference value comprises calculating the second creep torque reference value according to the vehicle acceleration from a creep torque-vehicle acceleration map representing a relation of the maximum creep torque and the vehicle acceleration.

5. The method of claim 4, wherein, in the creep torque-vehicle acceleration map, a creep torque increment to be applied to a section of vehicle acceleration smaller than a predetermined medium acceleration is set, and in the section of the vehicle acceleration smaller than the predetermined medium acceleration, the second creep torque reference value is obtained from a sum of the maximum creep torque and the creep torque increment.

6. The method of claim 5, wherein the creep torque increment is obtained according to the maximum creep torque and the vehicle speed from the creep torque-vehicle speed map for calculating the first creep torque reference value.

7. The method of claim 1, further comprising determining whether the G-sensor is faulty based on the first creep torque reference value 1 and the second creep torque reference value 2, and the vehicle acceleration and operating a warning unit to inform of a fault state.

8. The method of claim 7, wherein, if the vehicle acceleration is equal to or greater than a predetermined limit value, and a difference between the first creep torque reference value and the second creep torque reference value is equal to or greater that a predetermined reference value, the G-sensor is determined as faulty.

9. The method of claim 8, wherein, when the G-sensor is faulty, an emergency operation that generates a creep torque of the driving motor is performed using a creep torque value considered as a flat having a gradient of about 0 percent as a torque command value.

10. The method of claim 1, wherein the step of calculating the torque command value comprises finally determining a minimum value of the first creep torque reference value and the second creep torque reference value as a creep torque reference value, and calculating a torque command value according to a brake depth from a brake depth-torque map representing a relation among the creep torque reference value, the brake depth, and the gradient.

11. The method of claim 10, wherein the brake depth-torque map is set such that the brake depth at which the creep torque is released (creep torque equals to 0) when a brake pedal is depressed varies according to the gradient.

12. The method of claim 11, wherein the brake depth at which the creep torque is released is set greater as the gradient increases.

13. A system controlling creep torque to prevent a vehicle from rolling backward on an upward slope, the method comprising:

a sensor configured to detect a gradient of a driving road on which the vehicle is traveling;

a first unit configured to calculate the speed of the vehicle;

a second unit 13 configured to detect a brake depth according to operation of a brake pedal; and

a controller configured to calculate, in real-time, the gradient of the driving road from the detection value of the sensor and vehicle acceleration, calculate a maximum creep torque for preventing roll-back caused by gravity according to the gradient using the gradient and vehicle information, calculate a first creep torque reference based on the maximum creep torque and the calculated vehicle speed, calculate a second creep torque reference based on the maximum creep torque and the vehicle acceleration, calculate a torque command value according to an operation state of a brake based on the first creep torque reference value and the second creep torque reference value and the gradient, and generate a creep torque by controlling a torque output of a driving motor according to the calculated torque command value.