Virtual braking system for hydrostatically driven vehicle

• US 20040074691A1
• Filed: 06/11/2003
• Published: 04/22/2004
• Est. Priority Date: 12/11/2000
• Status: Abandoned Application

• Current Assignee: Camoplast Solideal Incorporated (Compagnie Generale DES Etablissements Michelin SCA)
• Original Assignee: Camoplast Solideal Incorporated (Compagnie Generale DES Etablissements Michelin SCA)
• Inventors: Todd, Andre, Bombardier, Joel
• Application Number:
  US10/450,160
• Publication Number:
  US 20040074691A1
• Time in Patent Office: Days
• US Class Current: 180/307
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2720/10 Longitudinal speed
• CPC Class Codes: F16H 59/18 dependent on the position of the accelerator pedal
• CPC Class Codes: F16H 59/54 dependent on signals from the brakes, e.g. parking brakes
• CPC Class Codes: F16H 61/4157 Control of braking, e.g. preventing pump over-speeding when motor acts as a pump
• CPC Class Codes: F16H 61/433 Pump capacity control by fluid pressure control means
• CPC Class Codes: F16H 61/46 Automatic regulation in accordance with output requirements
• CPC Class Codes: F16H 61/472 for achieving a target output torque

Abstract

A hydrostatic vehicle drive system features a “virtual” braking system designed to emulate the braking response of a mechanically driven vehicle equipped with an automatic transmission and disk or drum brakes. A microprocessor controls output of the pumps used to power the hydraulic motors, and causes the power output to decrease independently and gradually according to a declaration ramp, rather instantaneously with changes in fuel pedal position.

Claims

1. A drive system for a hydrostatically driven vehicle, comprising:

a hydrostatic motor capable of providing motive power to the vehicle in proportion to a flow rate of hydrostatic fluid through said hydrostatic motor;

a speed command input member capable of generating a speed command input value; and

a controller, in communication with said speed command input member, capable of receiving said speed command input value and regulating said flow rate to control the motive power provided by said hydrostatic motor based on said speed command input value;

wherein said controller regulates said flow rate so that

     1) said flow rate is directly proportional to said speed command input value when said speed command input value is in a steady state condition, and

     2) in response to a decrease in said speed command input value, said flow rate decreases at a rate that is not directly proportional to the decrease in said speed command input value.

2. The drive system of claim 1, wherein in response to a decrease in said speed command input value, said flow rate decreases at a rate that is independent of the decrease in said speed command input value.

3. The drive system of claim 1, wherein said speed command input member comprises a vehicle fuel pedal and said speed command input value is proportional to a position of said vehicle fuel pedal.

4. The drive system of claim 1, further comprising a braking command input member capable of generating a braking command input value,

wherein said controller, in communication with said braking command input member, receives said braking command input value and modifies the rate at which said flow rate decreases in accordance with said braking command input value.

5. The drive system of claim 4, wherein said braking command input member comprises a vehicle brake pedal and said braking command input value corresponds to a position of said vehicle brake pedal.

6. The drive system of claim 1, further comprising a panic stop command input member capable of generating a panic stop command input,

wherein said controller, in communication with said panic stop command input member, receives said panic stop command input and terminates the flow rate substantially instantaneously.

7. The drive system of claim 6, wherein said panic stop command input member comprises a panic switch.

8. The drive system of claim 7 further comprising a vehicle brake pedal, wherein said panic switch is positioned so as to be actuated upon complete depression of said vehicle brake pedal.

9. The drive system of claim 1, further comprising a pump which causes hydrostatic fluid to circulate through said hydrostatic motor.

10. The drive system of claim 9 wherein said pump is a variable displacement pump and said drive system further comprises a valve which regulates output of said variable displacement pump, said controller regulating said flow rate by controlling a setting of said valve.

11. The drive system of claim 1, wherein the vehicle has two independent propulsion assemblies, said drive system comprising a pair of independent hydrostatic motors and a pair of independent controllers.

12. A hydrostatically driven vehicle, comprising:

a propulsion-providing assembly; and

a drive system operatively connected to the propulsion-providing assembly including;

a hydrostatic motor capable of providing motive power to the propulsion-providing assembly in proportion to a flow rate of hydrostatic fluid through said hydrostatic motor,

a speed command input member capable of generating a speed command input value; and

a controller, in communication with said speed command input member, capable of receiving said speed command input value and regulating said flow rate to control the motive power provided by said hydrostatic motor based on said speed command input value;

wherein said controller regulates said flow rate so that

     1) said flow rate is directly proportional to said speed command input value when said speed command input value is it a steady state condition, and

     2) in response to a decrease in said speed command input value, said flow rate decreases at a rate that is not directly proportional to the decrease in said speed command input value.

13. The vehicle of claim 12, wherein in response to a decrease in said speed command input value, said flow rate decreases at a rate that is independent of the decrease in said speed command input value.

14. The vehicle of claim 12, wherein said speed command input member comprises a vehicle fuel pedal and said speed command input value is proportional to a position of said vehicle fuel pedal.

15. The vehicle of claim 12, further comprising a braking command input member capable of generating a braking command input value,

wherein said controller, in communication with said braking command input member, receives said braking command input value and modifies the rate at which said flow rate decreases in accordance with said braking command input value.

16. The vehicle of claim 15, wherein said braking command input member comprises a vehicle brake pedal and said braking command input value corresponds to a position of said vehicle brake pedal.

17. The vehicle of claim 12, further comprising a panic stop command input member capable of generating a panic stop command input,

wherein said controller, in communication with said panic stop command input member, receives said panic stop command input and terminates the flow rate substantially instantaneously.

18. The vehicle of claim 17, wherein said panic stop command input member comprises a panic switch.

19. The vehicle of claim 18, further comprising a vehicle brake pedal, wherein said panic switch is positioned so as to be actuated upon complete depression of said vehicle brake pedal.

20. The vehicle of claim 12, further comprising a pump which causes hydrostatic fluid to circulate through said hydrostatic motor.

21. The vehicle of claim 20, wherein said pump is a variable displacement pump and said drive system further comprises a valve which regulates output of said variable displacement pump, said controller regulating said flow rate by controlling a setting of said valve.

22. The vehicle of claim 12, wherein the vehicle has two independent propulsion-providing assemblies, said drive system comprising a pair of independent hydrostatic motors and a pair of independent controllers.

23. A method of operating a hydrostatically driven vehicle, said vehicle comprising a) a hydrostatic motor capable of providing motive power to the vehicle in proportion to a flow rate of hydrostatic fluid through said hydrostatic motor, and b) a speed command input member capable of generating a speed command input value, said method comprising:

regulating said flow rate such that said flow rate is directly proportional to said speed command input value when said speed command input value is in a steady state; and

regulating said flow rate when said speed command input value decreases such that said flow rate decreases at a rate which is not directly proportional to the decrease in said speed command input value.

24. The method of claim 23, wherein when said speed command input value decreases, said flow rate is regulated such that said flow rate decreases at a rate which is independent of the decrease in said speed command input value.

25. The method of claim 23, wherein the vehicle further comprises a braking command input member capable of generating a braking command input value, said method further comprising modifying the rate at which said flow rate decreases in accordance with said braking command input value.

26. The method of claim 23, wherein the vehicle further comprises a panic stop signal generating member capable of generating a panic stop signal, said method further comprising decreasing said flow rate to zero substantially instantaneously upon generation of a panic stop signal.