MOBILE MACHINES, ELECTRIC DRIVE SYSTEMS, AND METHODS FOR TESTING ELECTRIC DRIVE SYSTEMS

• US 20200132009A1
• Filed: 10/29/2018
• Published: 04/30/2020
• Est. Priority Date: 10/29/2018
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Landers, Sean C., Sonth, Sangameshwar
• Granted Patent: US 10,808,641 B2
• Time in Patent Office: Days
• CPC Class Codes: B60L 15/2009 for braking
• CPC Class Codes: B60L 2240/12 Speed
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60W 10/188 hydraulic brakes
• CPC Class Codes: B60W 20/40 Controlling the engagement or disengagement of prime movers, e.g. for transition between prime movers power-up or power-down of the driveline B60W30/192
• CPC Class Codes: B60W 2300/125 Heavy duty trucks
• CPC Class Codes: B60W 30/1882 characterised by the working point of the engine, e.g. by using engine output chart
• CPC Class Codes: B60Y 2200/411 Bulldozers, Graders
• CPC Class Codes: F02D 2250/18 Control of the engine output torque
• CPC Class Codes: F02D 2250/24 by using an external load, e.g. a generator
• CPC Class Codes: F02D 41/021 Introducing corrections for particular conditions exterior to the engine conjoint control of vehicle sub-units for propelling the vehicle B60W30/18
• CPC Class Codes: F02D 41/221 relating to the failure of actuators or electrically driven elements
• CPC Class Codes: F02D 41/2438 Active learning methods
• CPC Class Codes: F02D 41/3076 with special conditions for selecting a mode of combustion, e.g. for starting, for diagnosing
• CPC Class Codes: G01M 15/044 by monitoring power, e.g. by operating the engine with one of the ignitions interrupted; by using acceleration tests
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

A method for testing power of an electric drive system includes setting the electric motor of the electric drive system to a desired speed and applying a brake load to the system. The method also includes increasing the brake load until an engine of the electric drive system is fully loaded. After the engine is fully loaded, the method includes maintaining the brake load until the acceleration remains between the upper predetermined threshold and the lower predetermined threshold for the predetermined period of time, which indicates that the engine has stabilized at full power. Once the engine is at full power, the commanded power of the electric drive system required for stabilizing the engine at full power is averaged, and the average power is compared to a predetermined pass/fail threshold to determine if the electric drive system has sufficient power.

Claims

1. A mobile machine, comprising:

a main frame;

an undercarriage having one or more drive members; and

a drive system for providing power to the one or more drive members of the unercarriage, the drive system comprising;

an engine;

one or more motors operatively connected to the one or more drive members of the undercarriage; and

a power converter operatively connected to the engine, wherein the power converter is configured to convert mechanical energy from the engine to energy for providing to the one or more motors;

one or more controllers in circuit communication with at least one of the engine, the power converter, and the one or more motors, wherein the one or more controllers are configured to;

set the one or more motors to a desired commanded speed;

apply an initial commanded brake load to the drive system;

increase the initial commanded brake load until the engine is fully loaded;

stabilize the engine at full power after the engine is fully loaded;

calculate an average power of the drive system after the engine is stabilized at full power.

2. The mobile machine according to claim 1, wherein the drive system is an electric drive system, wherein the one or more motors comprise an electric motor, wherein the power converter is a generator that is configured to convert mechanical energy from the engine to electrical energy for providing to the one or more motors, and wherein the electric drive system further comprises power electronics configured to control the electrical energy that is provided to the electric motor by the generator.

3. The mobile machine according to claim 1, wherein the drive system is a hydrostatic drive system, and wherein the power converter comprises one or more pumps configured to convert mechanical energy from the engine to fluid energy for providing to the one or more motors.

4. The mobile machine according to claim 1, wherein the one or more controllers are configured to increase the initial commanded brake load until the engine is fully loaded by increasing the commanded brake load until the speed of the engine decreases below a first predetermined threshold.

5. The mobile machine according to claim 4, wherein the one or more controllers are configured to stabilize the engine at full power by maintaining the brake load after the speed of the engine decreases below the first predetermined threshold at least until the speed of the engine increases above a second predetermined threshold.

6. The mobile machine according to claim 5, wherein the one or more controllers are configured to calculate the average power of the drive system after the engine is stabilized at full power by averaging a power of the one or more motors for a predetermined period of time after the speed of the engine increases above the second predetermined threshold.

7. The mobile machine according to claim 6, wherein the one or more controllers are further configured to compare the average power of the drive system to a predetermined pass/fail threshold and determine a result based on the comparison between the average power and the predetermined pass/fail threshold.

8. The mobile machine according to claim 1, wherein the one or more controllers are configured to increase the initial commanded brake load until the engine is fully loaded by increasing the commanded brake load until the power of the drive system increases above a predetermined threshold.

9. The mobile machine according to claim 8, wherein the one or more controllers are configured to stabilize the engine at full power by maintaining the brake load after the power of the motor increases above the predetermined threshold at least until the speed of the motor decreases below a predetermined threshold.

10. The mobile machine according to claim 9, wherein the one or more controllers are configured to stabilize the engine at full power by maintaining the brake load after the speed of the motor decreases below the second predetermined threshold at least until the acceleration of the engine remains between an upper predetermined threshold and a lower predetermined threshold for a predetermined period of time.

11. The mobile machine according to claim 10, wherein the one or more controllers are configured to calculate the average power of the drive system after the engine is stabilized at full power by averaging a commanded power of the motor for a second predetermined period of time after the acceleration remains between the upper predetermined threshold and the lower predetermined threshold for the predetermined period of time, and wherein the one or more controllers are further configured to compare the average power of the drive system to a predetermined pass/fail threshold and determine a result based on the comparison between the average power and the predetermined pass/fail threshold.

12. The mobile machine according to claim 1, wherein the drive system is an electric drive system, and wherein the one or more controllers are configured to calculate the average power of the electric drive system by calculating the average of at least one of a power of a motor shaft of the motor, a motor AC power, a DC bus power, a power of a generator shaft, and a generator AC power.

13. An electric drive system for a mobile machine, the electric drive system comprising:

an engine;

an electric motor operatively connected to one or more drive members of the mobile machine; and

a generator operatively connected to the engine, wherein the generator is configured to convert mechanical energy from the engine to electrical energy for providing to the electric motor;

power electronics configured to control the electrical energy that is provided to the electric motor by the generator;

one or more controllers in circuit communication with at least one of the engine, the generator, and the electric motor, wherein the one or more controllers are configured to;

set the electric motor to a desired commanded speed;

apply an initial commanded brake load to the electric drive system;

increase the initial commanded brake load until the engine is fully loaded;

stabilize the engine at full power after the engine is fully loaded;

calculate an average power of the electric drive system after the engine is stabilized at full power.

14. The electric drive system according to claim 13, wherein:

the one or more controllers are configured to increase the initial commanded brake load until the engine is fully loaded by increasing the commanded brake load until the power of the motor increases above a predetermined threshold;

the one or more controllers are configured to stabilize the engine at full power by maintaining the brake load after the power of the motor increases above the predetermined threshold at least until the speed of the motor decreases below a second predetermined threshold;

the one or more controllers are configured to stabilize the engine at full power by maintaining the brake load after the speed of the motor decreases below the second predetermined threshold at least until the acceleration of the engine remains between an upper predetermined threshold and a lower predetermined threshold for a predetermined period of time;

the one or more controllers are configured to calculate the average power of the electric drive system after the engine is stabilized at full power by averaging a commanded power of the motor for a second predetermined period of time after the acceleration remains between the upper predetermined threshold and the lower predetermined threshold for the predetermined period of time; and

the one or more controllers are further configured to compare the average power of the electric drive system to a predetermined pass/fail threshold and determine a result based on the comparison between the average power and the predetermined pass/fail threshold.

15. The electric drive system according to claim 13, wherein the one or more controllers are configured to calculate the average power of the electric drive system by calculating the average of at least one of a power of a motor shaft of the motor, a motor AC power, a DC bus power, a power of a generator shaft, and a generator AC power.

16. A method of testing power of an electric drive system having an engine and an electric motor, the method comprising:

setting the electric motor to a desired commanded speed;

applying an initial brake load to the electric drive system;

increasing the initial brake load until the engine is fully loaded;

stabilizing the engine at full power after the engine is fully loaded; and

calculating an average power of the electric drive system after the engine is stabilized at full power.

17. The method according to claim 16, wherein the initial brake load is increased by a controller that is in circuit communication with at least one of the engine and the electric motor.

18. The method according to claim 16, wherein:

the increasing the initial brake load until the engine is fully loaded includes increasing the initial brake load until the power of the motor increases to a predetermined threshold;

the stabilizing the engine at full power after the engine is fully loaded includes maintaining the brake load after the power of the motor increases above the predetermined threshold at least until the speed of the motor decreases below a second predetermined threshold;

the stabilizing the engine at full power after the engine is fully loaded includes maintaining the brake load after the speed of the motor decreases below the second predetermined threshold at least until the acceleration of the engine remains between an upper predetermined threshold and a lower predetermined threshold for a predetermined period of time.

19. The method according to claim 16, further comprising comparing the average power of the electric drive system to a predetermined pass/fail threshold and determining a result based on the comparison between the average power and the predetermined pass/fail threshold

20. The method according to claim 16, wherein the calculating the average power of the electric drive system comprises calculating the average of at least one of a power of a motor shaft of the motor, a motor AC power, a DC bus power, and a generator AC power.