Hydraulic motor having controlled output based on machine slippage model

• US 20130313033A1
• Filed: 05/22/2012
• Published: 11/28/2013
• Est. Priority Date: 05/22/2012
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Elliott, Christopher
• Granted Patent: US 9,849,782 B2
• Time in Patent Office: Days
• US Class Current: 180/197
• CPC Class Codes: B60K 28/16 responsive to, or preventing, skidding of wheels brake control systems for vehicle drive stability B60T8/1755; arrangements responsive to a speed condition for adjusting wheel braking force B60T8/32; control of vehicle driving stability otherwise than by controlling the propulsion unit only B60W30/02; preventing wheel slippage by reducing power in rail vehicles B61C15/00
• CPC Class Codes: B60W 2050/0031 Mathematical model of the vehicle
• CPC Class Codes: B60W 2720/26 Wheel slip
• CPC Class Codes: B60Y 2200/25 Track vehicles
• CPC Class Codes: B60Y 2200/411 Bulldozers, Graders
• CPC Class Codes: F16H 61/47 for achieving a target output speed
• CPC Class Codes: F16H 61/475 for achieving a target power, e.g. input power or output power

Abstract

A method of managing operation of a machine is described herein. The machine includes drive components that supply a propulsive force exerted by the machine on a traveled surface. The machine includes a programmed controller that controls power output by a motor to the drive components of the machine, in accordance with a slippage model, to actively manage excessive slippage at a physical interface between the machine and the traveled surface. The programmed controller determines a track force indicative of the propulsive force exerted by the machine on the traveled surface. The programmed controller further determines a modeled slippage based, at least in part, upon the track force and the slippage model. The machine conditionally causes a reduction of the power output by the motor based upon a comparison, by the programmed controller, between the modeled slippage and a slippage limit.

Claims

1. A method of managing excessive slippage at a physical interface between a machine and a traveled surface, the method comprising:

determining a track force, the track force being indicative of a propulsive force exerted by the machine on the traveled surface;

determining a modeled slippage based, at least in part, upon the track force and a slippage model; and

conditionally causing a reduction of power output to drive components, by a motor, based upon a comparison between the modeled slippage and a slippage limit.

2. The method of claim 1, further comprising:

receiving a signal indicative of a normal force upon the traveled surface; and

calculating a ratio of the track force and the normal force,

wherein the modeled slippage is determined by applying the ratio to the slippage model.

3. The method of claim 2, wherein the slippage model relates the ratio to the modeled slippage, and

wherein a slippage value for the modeled slippage is defined, at least in part by, a ratio between:

(1) a slip velocity, consisting of a difference between a non-slip velocity and an actual velocity of the machine; and

(2) the non-slip velocity of the machine.

4. The method of claim 3 wherein the slippage is defined as a slip percentage.

5. The method of claim 1 wherein the motor is a hydraulic motor, and the conditionally causing a reduction of power output to drive components comprises reducing a speed of the hydraulic motor.

6. The method of claim 2 wherein the normal force upon the traveled surface is determined according to the expression:

(machine weight)×

cosine(traveled slope).

7. The method claim 1 wherein the motor is a hydraulic motor, and wherein the track force is determined according to the expression:

Ft=[Dm×

(delta)P×

GRFD/Rs]−

[machine mass×

a]

where;

Dm is the hydraulic motor displacement;

delta P is the differential pressure across the hydraulic motor;

GRFD is the gear ratio of the final drive;

Rs is the radius of the sprockets driving the continuous track; and

“

machine mass×

a”

is the force due to instantaneous acceleration of the machine.

8. The method of claim 1 further comprising:

determining an actual velocity of the machine in a forward direction;

determining a non-slip velocity of the machine based upon a speed of a propulsive drive component of the machine;

calculating a current slippage, wherein the current slippage is defined, at least in part, by a current slip ratio between;

(1) a difference between the non-slip velocity and the actual velocity of the machine; and

(2) the non-slip velocity of the machine; and

updating the slippage model based, at least in part, upon the current slippage and the track force.

9. The method of claim 8 further comprising the step of:

processing a stream of accelerometer signal values to render the actual velocity of the machine.

10. The method of claim 9 wherein the processing step comprises applying a filter to the stream of accelerometer signal values.

11. The method of claim 8 wherein updating the slippage model comprises applying a filter to the current slippage when incorporating the current slippage into the slippage model.

12. A non-transitory computer-readable medium including computer executable instructions for managing excessive slippage at a physical interface between a machine and a traveled surface, the computer-executable instructions, when executed by a programmed controller, facilitating performing the steps of:

determining a track force, the track force being indicative of the propulsive force exerted by the machine on the traveled surface;

determining a modeled slippage based, at least in part, upon the track force and a slippage model; and

conditionally causing a reduction of power output to drive components, by a motor, based upon a comparison between the modeled slippage and a slippage limit.

13. The non-transitory computer-readable medium of claim 12, further comprising computer-executable instructions for:

receiving a signal indicative of a normal force upon the traveled surface; and

calculating a ratio of the track force and the normal force,

wherein the modeled slippage is determined by applying the ratio to the slippage model.

14. The non-transitory computer-readable medium of claim 13, wherein the slippage model relates the ratio to the modeled slippage, and

wherein a slippage value for the modeled slippage is defined, at least in part by, a ratio between:

(1) a slip velocity, consisting of a difference between a non-slip velocity and an actual velocity of the machine; and

(2) the non-slip velocity of the machine.

15. The non-transitory computer-readable medium of claim 12 wherein the motor is a hydraulic motor, and wherein the track force is determined according to the expression:

Ft=[Dm×

(delta)P×

GRFD/Rs]−

[machine mass×

a]

where;

Dm is the hydraulic motor displacement;

delta P is the differential pressure across the hydraulic motor;

GRFD is the gear ratio of the final drive;

Rs is the radius of the sprockets driving the continuous track; and

“

machine mass×

a”

is the force due to instantaneous acceleration of the machine.

16. The non-transitory computer-readable medium of claim 12 further comprising computer-executable instructions for:

determining an actual velocity of the machine in a forward direction;

determining a non-slip velocity of the machine based upon a speed of a propulsive drive component of the machine;

calculating a current slippage, wherein the current slippage is defined, at least in part, by a current slip ratio between;

(1) a difference between the non-slip velocity and the actual velocity of the machine; and

(2) the non-slip velocity of the machine; and

updating the slippage model based, at least in part, upon the current slippage and the track force.

17. A machine including:

a propulsive force source for driving the machine on a traveled surface; and

a programmed controller including a slippage control module including computer-executable instructions for managing excessive slippage at a physical interface between a machine and a traveled surface, the computer-executable instructions, when executed by the programmed controller, facilitating performing the steps of;

determining a track force, the track force being indicative of the propulsive force exerted by the machine on the traveled surface;

determining a modeled slippage based, at least in part, upon the track force and a slippage model; and

conditionally causing a reduction of power output to drive components, by a motor, based upon a comparison, by the programmed controller, between the modeled slippage and a slippage limit.

18. The machine according to claim 17 wherein the propulsive force source is a hydraulic motor.

19. The machine according to claim 18 further comprising a continuous track driven by the hydraulic motor.

20. The machine according to claim 17 wherein the slippage control module further comprises computer-executable instructions for:

determining an actual velocity of the machine in a forward direction;

determining a non-slip velocity of the machine based upon a speed of a propulsive drive component of the machine;

calculating a current slippage, wherein the current slippage is defined, at least in part, by a current slip ratio between;

(1) a difference between the non-slip velocity and the actual velocity of the machine; and

(2) the non-slip velocity of the machine; and

updating the slippage model based, at least in part, upon the current slippage and the track force.