Electronic traction control system

• US 6,631,320 B1
• Filed: 11/27/2002
• Issued: 10/07/2003
• Est. Priority Date: 11/27/2002
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Jensen, Jeffrey E., Holt, Bradford J., Marks, Scott A., Marathe, Sameer
• Primary Examiner(s): Camby, Richard M.
• Application Number:
  US10/305,619
• Time in Patent Office: 314 Days
• Field of Search: 180/197, 180/235, 180/244, 303/122.07, 303/123, 701/82, 701/83, 701/84, 701/90, 701/91
• US Class Current: 701/83
• CPC Class Codes: B60K 17/20 in which the differential movement is limited
• CPC Class Codes: B60K 23/04 for differential gearing
• CPC Class Codes: B60T 8/175 Brake regulation specially adapted to prevent excessive wheel spin during vehicle acceleration, e.g. for traction control safety devices for propulsion unit control responsive to, or preventing, skidding of wheels B60K28/16
• CPC Class Codes: B60W 2050/0011 Proportional Integral Differential [PID] controller
• CPC Class Codes: B60W 2300/17 Construction vehicles, e.g. graders, excavators
• CPC Class Codes: B60W 2520/22 Articulation angle, e.g. between tractor and trailer
• CPC Class Codes: B60W 2520/28 Wheel speed
• CPC Class Codes: B60W 2530/10 Weight
• CPC Class Codes: B60W 2540/12 Brake pedal position
• CPC Class Codes: B60Y 2200/41 Construction vehicles, e.g. graders, excavators
• CPC Class Codes: B62D 11/24 Endless track steering specially adapted for vehicles having both steerable wheels and endless track
• CPC Class Codes: B62D 12/00 Steering specially adapted for vehicles operating in tandem or having pivotally connected frames steering endless tracks or the like B62D11/00; steering specially adapted for trailers B62D13/00
• CPC Class Codes: E02F 9/0841 Articulated frame, i.e. having at least one pivot point between two travelling gear units tractor-trailer combinations B62D53/00
• CPC Class Codes: E02F 9/2083 Control of vehicle braking systems
• CPC Class Codes: E02F 9/225 Control of steering, e.g. for hydraulic motors driving the vehicle tracks steering in general B62D
• CPC Class Codes: E02F 9/2253 Controlling the travelling speed of vehicles, e.g. adjusting travelling speed according to implement loads, control of hydrostatic transmission
• CPC Class Codes: E02F 9/24 Safety devices , e.g. for preventing overload E02F9/226 takes precedence

Abstract

An articulated work machine has a front frame and a rear frame connected for pivotal movement therebetween for steering the machine by an articulation joint. Each of the front and rear frames has two driven wheels, spaced laterally, each having a brake associated therewith. As the machine articulates during steering, one or more of the wheels may lose traction and slip. An electronic traction control system receives measured wheel speed signals and an articulation angle signal, calculates a desired wheel speed responsive to the wheel speed and articulation angle signals, and selectively applies the brakes until the measured wheel speed is equal to the desired wheel speed.

Claims

1. An electronic traction control system for a work machine having a front frame, a rear frame, and an articulation joint connecting the front and rear frames, the system comprising:

an articulation sensor adapted to provide an articulation angle signal;

at least two wheels, with each wheel adapted to provide a wheel speed signal;

a brake associated with the work machine;

an electronic control module adapted to receive the articulation angle and wheel speed signals;

calculate an articulation rate responsive to the articulation angle signal;

determine a desired wheel speed having at least one of;

an articulation-caused linear velocity component calculated responsive to the articulation rate, articulation angle, and wheel speed signals, and a transient articulation-caused velocity component calculated responsive to the articulation rate, articulation angle, and wheel speed signals; and

responsively produce a brake signal to control the brake.

2. The electronic traction control system of claim 1, including a load sensor which produces a load signal and wherein the electronic control module also determines the desired wheel speed relative to the load signal.

3. The electronic traction control system of claim 1, wherein the brake signal controls one or more of the brakes to apply braking forces to at least one wheel having a speed greater than the desired wheel speed.

4. The electronic traction control system of claim 1, wherein the electronic control module calculates a wheel speed error value responsive to the wheel speed signals and the desired wheel speed, and a magnitude of the brake signal is dependent on, and directly proportional to, a magnitude of the wheel speed error value.

5. The electronic traction control system of claim 1, wherein the electronic control module calculates a reference value based on the articulation angle signal, the articulation rate calculated responsive to the articulation angle signal, and a machine speed calculated responsive to the wheel speeds.

6. The electronic traction control system of claim 5, wherein the electronic control module calculates a wheel speed error value responsive to at least one of the wheel speed signal and to the desired wheel speed and compares the reference value to the wheel speed error value, wherein the brake signal is responsively controlled to bring the wheel speed error value closer to the reference value when the wheel speed error value is greater than the reference value.

7. The electronic traction control system of claim 1, including a differential lock having a differential lock engagement value and wherein the electronic control module controls the differential lock to bring the differential lock engagement value to a predetermined maximum engagement value.

8. An electronic traction control system for a work machine having front and rear frames connected by an articulation joint for relative pivotal movement, each frame having at least one driven wheel, comprising:

an articulation sensor associated with the articulation joint and adapted to produce an articulation angle signal;

a wheel speed sensor associated with each wheel, each adapted to produce a wheel speed signal;

an electronic control module adapted to receive the articulation angle signal and the wheel speed signals, determine a measured wheel velocity value responsive to each wheel speed signal, determine an articulation rate value responsive to the articulation angle signal, calculate an articulation-caused linear velocity value for each wheel responsive to the articulation angle, articulation rate, and wheel speed signals and a transient articulation-caused velocity value for each wheel responsive to the articulation angle, articulation rate, and wheel speed signals, calculate a desired wheel velocity value for each wheel responsive to the articulation-caused linear velocity value and the transient articulation-caused velocity value, calculate an error value responsive to the measured wheel velocity value and the desired wheel velocity value, and produce a brake signal for each wheel responsive to the error value; and

a brake associated with each wheel adapted to receive the brake signal and actuate responsively thereto.

9. The electronic traction control system of claim 8, wherein the brake is controlled by the brake signal using a proportional-integral-derivative control.

10. The electronic traction control system of claim 8, including a load sensor adapted to measure a variable load carried by the work machine and produce a load signal, and wherein the desired wheel velocity value is also calculated responsive to the load signal.

11. The electronic traction control system of claim 8, including a differential lock associated with at least one wheel and having a differential lock engagement value, wherein an engagement of the differential lock is controlled responsive to the differential lock engagement value being less than a maximum.

12. A method of controlling wheel slip of an articulated work machine, comprising:

comparing the relative positioning of a front frame and a rear frame of the work machine and responsively producing an articulation angle signal;

sensing a speed of at least one wheel associated with at least one of the front and rear frames and responsively producing a wheel speed signal;

receiving the articulation angle signal and each wheel speed signal;

producing a wheel speed value responsive to each wheel speed signal;

determining a rate of change of the articulation angle signal and responsively producing an articulation rate value;

producing an articulation-caused linear velocity value responsive to the articulation angle signal, the articulation rate value, and each wheel speed signal;

producing a transient articulation-caused velocity value responsive to the articulation angle signal, the articulation rate value, and each wheel speed signal;

producing a desired wheel speed value based on the articulation-caused linear and transient articulation-caused velocity values;

comparing the wheel speed value to the desired wheel speed value;

producing a brake signal responsive to the difference between the actual wheel speed value and the desired wheel speed value; and

controlling a brake associated with each wheel responsive to the brake signal.

13. The method of claim 12, wherein the step of producing the actual wheel speed value includes the steps of:

producing a articulation-caused linear velocity value responsive to the articulation angle signal and a calculated steady-state angular velocity value;

producing a transient articulation-caused velocity value responsive to the articulation angle and articulation rate signals; and

producing the desired wheel speed value as a sum of the articulation-caused linear velocity value and the transient articulation-caused velocity value.

14. The method of claim 12, including the step of sensing a variable machine load and responsively producing a load signal, and wherein the step of producing the desired wheel speed value includes calculating the desired wheel speed value responsive to the load signal.

15. The method of claim 12, including the step of sensing a differential lock engagement and controlling the differential lock to bring the differential lock engagement to a predetermined maximum engagement.

16. An electronic traction control system for a work machine having a front frame, a rear frame, and an articulation joint connecting the front and rear frames, the system comprising:

an articulation sensor adapted to provide an articulation angle signal θ

_ART;

four wheels, with each wheel adapted to provide a wheel speed signal V_ACTRR, V_ACTRF, V_ACTLR, or V_ACTLF;

a brake associated with the work machine;

an electronic control module adapted to receive the articulation angle and wheel speed signals θ

_ART, V_ACTRR, V_ACTRF, V_ACTLR, and V_ACTLF;

calculate an articulation rate using ω

_ART=dθ

_ART/dt;

determine a desired wheel speed V_DES; and

responsively produce a brake signal to control the brake, wherein the desired wheel speed V_DES for each wheel is calculated using the following equations;