Method and apparatus for synchronizing a vehicle lift

• US 20030192744A1
• Filed: 04/12/2002
• Published: 10/16/2003
• Est. Priority Date: 04/12/2002
• Status: Active Grant

• Current Assignee: Rotary Lift
• Original Assignee: Rotary Lift
• Inventors: Porter, David P., Green, Steven D.
• Granted Patent: US 6,763,916 B2
• Time in Patent Office: Days
• US Class Current: 187/277
• CPC Class Codes: B66F 7/20 by several jacks with means for maintaining the platforms horizontal during movement
• CPC Class Codes: F15B 11/22 Synchronisation of the movement of two or more servomotors
• CPC Class Codes: F15B 15/283 using a cable wrapped on a drum and attached to the piston
• CPC Class Codes: F15B 9/17 with electrical control means

Abstract

A vehicle lift control maintains multiple points of a lift system within the same horizontal plane during vertical movement of the lift engagement structure by synchronizing the movement thereof. A vertical trajectory is compared to actual positions to generate a raise signal. A position synchronization circuit synchronizes the vertical actuation of the moveable lift components by determining a proportional-integral error signal.

Claims

21. A control system for a vehicle lift, said vehicle lift having a first pair formed of a first vertically moveable superstructure and a second vertically moveable superstructure, said control system comprising:

a. a first position sensor operable to sense a vertical position of the first vertically moveable superstructure;

b. a second position sensor operable to sense a vertical position of the vertically moveable superstructure; and

c. a position synchronization circuit responsive to the first and second position sensors and operably configured to synchronize vertical actuation of the pair of the first and second posts.

1. A controller for a vehicle lift, said vehicle lift having a first pair formed of a first vertically moveable superstructure and a second vertically moveable superstructure, each of said first and second vertically moveable superstructures having respective vertical positions which vary when said first and second vertically moveable superstructures are respectively moved, said controller comprising:

a. an interface configured to receive a first position signal indicative of the vertical position of said first vertically moveable superstructure and a second position signal indicative of the vertical position of said second vertically moveable superstructure;

b. a position synchronization circuit responsive to said first and second position signals and operably configured to synchronize vertical actuation of said first and second vertically moveable superstructures.

2. The controller of claim 1, wherein the position synchronization circuit is configured to synchronize vertical actuation of said first pair by determining a proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures.

3. The controller of claim 1, wherein the controller further comprises a lowering circuit operably configured to generate at least one lowering signal for said first and second vertically moveable superstructures.

4. The controller of claim 3, wherein the position synchronization circuit is configured to synchronize vertical actuation of said first pair by determining a proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures.

5. The controller of claim 4, wherein said controller is configured to generate a first movement control signal for lowering said first vertically moveable superstructure and to generate a second movement control signal for lowering said second vertically moveable superstructure, in response to said proportional-integral error signal and said at least one lowering signal.

6. The controller of claim 1, wherein the controller is further configured to generate a vertical trajectory signal.

7. The controller of claim 6, further comprising a raise circuit responsive to said first and second position signals and to said vertical trajectory signal and operably configured to generate a first raise signal for said first vertically moveable superstructure and to generate a second raise signal for said second vertically moveable superstructure.

8. The controller of claim 1, further comprising a raise circuit responsive to said first and second position signals and to a vertical trajectory signal and operably configured to generate a first raise signal for said first vertically moveable superstructure and to generate a second raise signal for said second vertically moveable superstructure.

9. The controller of claims 7 or 8, wherein the position synchronization circuit is configured to synchronize vertical actuation of said first pair by determining a proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures.

10. The controller of claim 9, where in said controller is configured to generate a first movement control signal for raising first vertically moveable superstructure in response to said proportional-integral error signal and said first raise signal, and to generate a second movement control signal for raising said second vertically moveable superstructure in response to said proportional-integral error signal and said second raise signal.

11. The controller of claim 1, wherein said vehicle lift includes a second pair formed of a third vertically moveable superstructure and a fourth vertically moveable superstructure, each of said third and fourth vertically moveable superstructures having respective vertical positions which vary when said third and fourth vertically moveable superstructures are respectively moved, wherein:

a. said interface is configured to receive a third position signal indicative of the vertical position of said third vertically moveable superstructure and a fourth position signal indicative of the vertical position of said fourth vertically moveable superstructure;

b. said position synchronization circuit is responsive to said third and fourth position signals and operably configured to synchronize vertical actuation of said third and fourth vertically moveable superstructures.

12. The controller of claim 11, wherein the controller is further configured to synchronize the first and second pairs relative to each other by determining a lift proportional-integral signal for a sum of the vertical positions of said first and second vertically moveable superstructures relative to a sum of the vertical positions of said third and fourth vertically moveable superstructures.

13. The controller of claim 12, wherein said position synchronization circuit is operably configured to synchronize vertical actuation of said first pair by determining a first pair proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures and is operably configured to synchronize vertical actuation of said second pair by determining a second pair proportional-integral error signal relative to the respective vertical positions of said third and fourth vertically moveable superstructures.

14. The controller of claim 11, further wherein the controller comprises a lowering circuit operably configured to generate at least one lowering signal for said first, second, third and fourth vertically moveable superstructures.

15. The controller of claim 11, wherein the controller is further configured to generate a vertical trajectory signal.

16. The controller of claim 15, further comprising a raise circuit responsive to said first, second, third and fourth position signals and to said vertical trajectory signal and operably configured to generate a first raise signal for said first vertically moveable superstructure, to generate a second raise signal for said second vertically moveable superstructure, to generate a third raise signal for said third vertically moveable superstructure and to generate a fourth raise signal for said fourth vertically moveable superstructure.

17. The controller of claim 11, further comprising a raise circuit responsive to said first, second, third and fourth position signals and to a vertical trajectory signal and operably configured to generate a first raise signal for said first vertically moveable superstructure, to generate a second raise signal for said second vertically moveable superstructure, to generate a third raise signal for said third vertically moveable superstructure and to generate a fourth raise signal for said fourth vertically moveable superstructure.

18. The control of claims 16 or 17, wherein the controller is further configured to synchronize the first and second pairs relative to each other by determining a lift proportional-integral signal for a sum of the vertical positions of said first and second vertically moveable superstructures relative to a sum of the vertical positions of said third and fourth vertically moveable superstructures.

19. The controller of claim 18, wherein the position synchronization circuit is configured to synchronize vertical actuation of said first pair by determining a first pair proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures and is configured to synchronize vertical actuation of said second pair by determining a second pair proportional-integral error signal relative to the respective vertical positions of said third and fourth vertically moveable superstructures.

20. The controller of claim 19, wherein said controller is configured to generate a first movement control signal for raising said first vertically moveable superstructure in response to said lift proportional-integral error signal, said first pair proportional-integral error signal and said first raise signal, to generate a second movement control signal for raising said second vertically moveable superstructure in response to said lift proportional-integral error signal, said first pair proportional-integral error signal and said second raise signal, to generate a third movement control signal for raising said third vertically moveable superstructure in response to said lift proportional-integral error signal, said second pair proportional-integral error signal and said third raise signal, and to generate a fourth movement control signal for raising said fourth vertically moveable superstructure in response to said lift proportional-integral error signal, said second pair proportional-integral error signal and said fourth raise signal.

22. The controller of claim 21, wherein the position synchronization circuit is configured to synchronize vertical actuation of said first pair by determining a proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures.

23. The controller of claim 21, wherein the controller further comprises a lowering circuit operably configured to generate at least one lowering signal for said first and second vertically moveable superstructures.

24. The controller of claim 23, wherein the position synchronization circuit is configured to synchronize vertical actuation of said first pair by determining a proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures.

25. The controller of claim 24, wherein said controller is configured to generate a first movement control signal for lowering said first vertically moveable superstructure and to generate a second movement control signal for lowering said second vertically moveable superstructure, in response to said proportional-integral error signal and said at least one lowering signal.

28. The controller of claim 21, further comprising a raise circuit responsive to said first and second position signals and to a vertical trajectory signal and operably configured to generate a first raise signal for said first vertically moveable superstructure and to generate a second raise signal for said second vertically moveable superstructure.

31. The controller of claim 21, wherein said vehicle lift includes a second pair formed of a third vertically moveable superstructure and a fourth vertically moveable superstructure, each of said third and fourth vertically moveable superstructures having respective vertical positions which vary when said third and fourth vertically moveable superstructures are respectively moved, wherein:

a. said interface is configured to receive a third position signal indicative of the vertical position of said third vertically moveable superstructure and a fourth position signal indicative of the vertical position of said fourth vertically moveable superstructure;

b. said position synchronization circuit is responsive to said third and fourth position signals and operably configured to synchronize vertical actuation of said third and fourth vertically moveable superstructures.

32. The controller of claim 31, wherein the controller is further configured to synchronize the first and second pairs relative to each other by determining a lift proportional-integral signal for a sum of the vertical positions of said first and second vertically moveable superstructures relative to a sum of the vertical positions of said third and fourth vertically moveable superstructures.

33. The controller of claim 32, wherein said position synchronization circuit is operably configured to synchronize vertical actuation of said first pair by determining a first pair proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures and is operably configured to synchronize vertical actuation of said second pair by determining a second pair proportional-integral error signal relative to the respective vertical positions of said third and fourth vertically moveable superstructures.

34. The controller of claim 31, further wherein the controller comprises a lowering circuit operably configured to generate at least one lowering signal for said first, second, third and fourth vertically moveable superstructures.

35. The controller of claim 31, wherein the controller is further configured to generate a vertical trajectory signal.

36. The controller of claim 35, further comprising a raise circuit responsive to said first, second, third and fourth position signals and to said vertical trajectory signal and operably configured to generate a first raise signal for said first vertically moveable superstructure, to generate a second raise signal for said second vertically moveable superstructure, to generate a third raise signal for said third vertically moveable superstructure and to generate a fourth raise signal for said fourth vertically moveable superstructure.

37. The controller of claim 31, further comprising a raise circuit responsive to said first, second, third and fourth position signals and to a vertical trajectory signal and operably configured to generate a first raise signal for said first vertically moveable superstructure, to generate a second raise signal for said second vertically moveable superstructure, to generate a third raise signal for said third vertically moveable superstructure and to generate a fourth raise signal for said fourth vertically moveable superstructure.

38. The control of claims 36 or 37, wherein the controller is further configured to synchronize the first and second pairs relative to each other by determining a lift proportional-integral signal for a sum of the vertical positions of said first and second vertically moveable superstructures relative to a sum of the vertical positions of said third and fourth vertically moveable superstructures.

39. The controller of claim 38, wherein the position synchronization circuit is configured to synchronize vertical actuation of said first pair by determining a first pair proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures and is configured to synchronize vertical actuation of said second pair by determining a second pair proportional-integral error signal relative to the respective vertical positions of said third and fourth vertically moveable superstructures.

40. The controller of claim 39, wherein said controller is configured to generate a first movement control signal for raising said first vertically moveable superstructure in response to said lift proportional-integral error signal, said first pair proportional-integral error signal and said first raise signal, to generate a second movement control signal for raising said second vertically moveable superstructure in response to said lift proportional-integral error signal, said first pair proportional-integral error signal and said second raise signal, to generate a third movement control signal for raising said third vertically moveable superstructure in response to said lift proportional-integral error signal, said second pair proportional-integral error signal and said third raise signal, and to generate a fourth movement control signal for raising said fourth vertically moveable superstructure in response to said lift proportional-integral error signal, said second pair proportional-integral error signal and said fourth raise signal.

25-1. The controller of claim 21, wherein the controller is further configured to generate a vertical trajectory signal.

27. The controller of claim 26, further comprising a raise circuit responsive to said first and second position signals and to said vertical trajectory signal and operably configured to generate a first raise signal for said first vertically moveable superstructure and to generate a second raise signal for said second vertically moveable superstructure.

29. The controller of claims 27 or 28, wherein the position synchronization circuit is configured to synchronize vertical actuation of said first pair by determining a proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures.

30. The controller of claim 29, wherein said controller is configured to generate a first movement control signal for raising first vertically moveable superstructure in response to said proportional-integral error signal and said first raise signal, and to generate a second movement control signal for raising said second vertically moveable superstructure in response to said proportional-integral error signal and said second raise signal.

41. A hydraulic fluid control system for a vehicle lift comprising:

a. at least one source of hydraulic fluid;

b. a first hydraulic actuator configured to move a first vertically moveable superstructure, said first hydraulic actuator being in fluid communication with said at least one source of hydraulic fluid;

c. a second hydraulic actuator configured to move a second vertically moveable superstructure, said second hydraulic actuator being in fluid communication with said at least one source of hydraulic fluid;

d. a first proportional flow control valve interposed between said at least one source of hydraulic fluid and said first hydraulic actuator;

e. a second proportional flow control valve interposed between said at least one source of hydraulic fluid and said second hydraulic actuator;

f. said first proportional flow control valve and said second proportional flow control valve each being independently controllable relative to each other; and

g. a controller connected to said first and second proportional flow control valves for controlling flow of said hydraulic fluid to said first and second hydraulic actuators.

42. The hydraulic fluid control system of claim 41, wherein said at least one source of hydraulic fluid comprises a first and second source of hydraulic fluid, said first hydraulic actuator being in fluid communication with said first source and said second hydraulic actuator being in fluid communication with said second source.

43. The hydraulic fluid control system of claim 41, wherein no hydraulic fluid between either of said first proportional flow control valve and said first hydraulic actuator and said second proportional flow control valve and said second hydraulic actuator is bled off.

44. The hydraulic fluid control system of claim 41, wherein control of the flow of hydraulic fluid to said first and second hydraulic actuators is controlled solely by said first and second proportional flow control valves, respectively.

45. A hydraulic fluid control system for a vehicle lift comprising:

a. a first hydraulic actuator configured to move a first vertically moveable superstructure, said first hydraulic actuator being in fluid communication with a source of hydraulic fluid associated with said first hydraulic actuator;

b. a first pump having a first discharge, said first discharge being in fluid communication with said first hydraulic actuator;

c. a second hydraulic actuator configured to move a second vertically moveable superstructure, said second hydraulic actuator being in fluid communication with an associated source of hydraulic fluid;

d. a second pump having a second discharge, said second discharge being in fluid communication with said second hydraulic actuator; and

e. a controller connected to said first and second pumps for controlling the respective speeds of said first and second pumps variably, whereby flow of said hydraulic fluid to said first and second hydraulic actuators is controlled.

46. The vehicle lift of claim 45, wherein said source of hydraulic fluid associated with said first hydraulic actuator and said source of hydraulic fluid associated with said second hydraulic actuator are the same source.

47. A controller for a vehicle lift, said vehicle lift having a first vertically moveable superstructure and a second vertically moveable superstructure, each of said first and second vertically moveable superstructures having respective vertical positions which vary when said first and second vertically moveable superstructures are respectively moved, said controller comprising:

a. an interface configured to receive a first position signal indicative of the vertical position of said first vertically moveable superstructure and a second position signal indicative of the vertical position of said second vertically moveable superstructure;

b. a raise circuit responsive to said first and second position signals and to a vertical trajectory signal and operably configured to generate a first raise signal for said first vertically moveable superstructure and to generate a second raise signal for said second vertically moveable superstructure.

48. The controller of claim 47, further comprising a position synchronization circuit operably configured to synchronize vertical actuation of said first and second vertically moveable superstructures by determining a proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures.

49. The controller of claim 47, wherein said controller is operably configured to generate a vertical trajectory signal for said first and second vertically moveable superstructures.

50. A vehicle lift having a first pair formed of a first vertically moveable superstructure and a second vertically moveable superstructure, each of said first and second vertically moveable superstructures having respective vertical positions which vary when said first and second vertically moveable superstructures are respectively moved, said vehicle lift comprising:

a. a first circuit operably configured to generate a first position signal indicative of the vertical position of said first vertically moveable superstructure;

b. a second circuit operably configured to generate a second position signal indicative of the vertical position of said second vertically moveable superstructure

c. a third circuit operably configured to generate a first raise signal for said first vertically moveable superstructure and to generate a second raise signal for said second vertically moveable superstructure, said first and second raise signals respectively being functions of said first and second position signals and a vertical trajectory signal.

51. The vehicle lift of claim 50, comprising:

a. a first position sensor operable to sense the vertical position of said first vertically moveable superstructure; and

b. a second position sensor operable to sense the vertical position of said second vertically moveable superstructure.

52. The vehicle lift of claim 50, further comprising a fourth circuit operably configured to synchronize vertical actuation of said first and second vertically moveable superstructures by determining a proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures.

53. The vehicle lift of claim 52, further comprising a fifth circuit operably configured to generate a first movement control signal for raising first vertically moveable superstructure in response to said proportional-integral error signal and said first raise signal, and to generate a second movement control signal for raising said second vertically moveable superstructure in response to said proportional-integral error signal and said second raise signal.

54. The vehicle lift of claim 50, further comprising a fourth circuit operably configured to generate at least one lowering signal for said first and second vertically moveable superstructures.

55. The vehicle lift of claim 54, further comprising a fifth circuit operably configured to synchronize vertical actuation of said first pair by determining a proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures.

56. The vehicle lift of claim 55, further comprising a sixth circuit operably configured to generate a first movement control signal for lowering said first vertically moveable superstructure and to generate a second movement control signal for lowering said second vertically moveable superstructure, in response to said proportional-integral error signal and said at least one lowering signal.

57. The vehicle lift of claim 52, further comprising a fifth circuit operably configured to generate a first movement control signal for raising first vertically moveable superstructure in response to said proportional-integral error signal and said first raise signal, and to generate a second movement control signal for raising said second vertically moveable superstructure in response to said proportional-integral error signal and said second raise signal.

58. The vehicle lift of claim 50, further comprising a second pair formed of a third vertically moveable superstructure and a fourth vertically moveable superstructure, each of said third and fourth vertically moveable superstructures having respective vertical positions which vary when said third and fourth vertically moveable superstructures are respectively moved, and further comprising a fourth circuit operably configured to synchronize the first and second pairs relative to each other by determining a proportional-integral signal for a sum of the vertical positions of said first and second vertically moveable superstructures relative to a sum of the vertical positions of said third and fourth vertically moveable superstructures.

59. The vehicle lift of claim 58, further comprising a fifth circuit operably configured to synchronize vertical actuation of said first pair by determining a first pair proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures and operably configured to synchronize vertical actuation of said second pair by determining a second pair proportional-integral error signal relative to the respective vertical positions of said third and fourth vertically moveable superstructures.

60. A controller for a vehicle lift, said vehicle lift having a first pair formed of a first vertically moveable superstructure and a second vertically moveable superstructure, each of said first and second vertically moveable superstructures having respective vertical positions which vary when said first and second vertically moveable superstructures are respectively moved, said controller comprising:

a. a first feedback control loop operably configured to command said first and second vertically moveable superstructures to a vertical trajectory; and

b. a first differential feedback control loop operably configured to synchronize movement of said first and second vertically moveable superstructure.

61. The controller of claim 60, wherein said first feedback control loop is operably configured to generate a first command signal for said first vertically moveable superstructure and to generate a second command signal for said second vertically moveable superstructure, said first and second command signals respectively being functions of the vertical positions of said first and second vertically moveable superstructures and said vertical trajectory.

62. The controller of claim 60 further configured to generate a constant command signal for lowering said first and second vertically moveable superstructures.

63. The controller of claim 60, wherein said first differential feedback control loop is configured to synchronize vertical actuation of said first pair by generating a synchronization command signal which comprises a proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures.

64. The controller of claim 63, wherein said vehicle lift includes a second pair formed of a third vertically moveable superstructure and a fourth vertically moveable superstructure, each of said third and fourth vertically moveable superstructures having respective vertical positions which vary when said third and fourth vertically moveable superstructures are respectively moved, wherein said controller includes a second differential feedback control loop operably configured to synchronize movement of said first and second pairs.

65. A vehicle lift comprising:

a. a first vertically moveable superstructure having a variable vertical position;

b. a second vertically moveable superstructure having a variable vertical position;

c. a controller operably configured to generate a vertical trajectory signal for said first and second vertically moveable superstructures.

66. The vehicle lift of claim 65, wherein said controller is operably configured to generate in response to said vertical trajectory signal a first raise signal for said first vertically moveable superstructure and a second raise signal for said second vertically moveable superstructure.

67. The vehicle lift of claim 65, wherein said controller is operably configured to synchronize vertical actuation of said first and second vertically moveable superstructures by determining a proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures.

68. A vehicle lift comprising:

a. a first vertically moveable superstructure having a variable vertical position;

b. a second vertically moveable superstructure having a variable vertical position;

c. a controller operably configured to synchronize vertical actuation of said first and second vertically moveable superstructures by determining a proportional-integral error signal relative to the respective vertical positions of said first and second vertically moveable superstructures.

69. The vehicle lift of claim 68, wherein said controller is operably configured to generate in response at least to said proportional-integral error signal a first movement control signal for raising first vertically moveable superstructure, and a second movement control signal for raising said second vertically moveable superstructure.

70. A controller for a vehicle lift, said vehicle lift having a first pair formed of a first vertically moveable superstructure and a second vertically moveable superstructure, each of said first and second vertically moveable superstructures having respective vertical positions which vary when said first and second vertically moveable superstructures are respectively moved, said controller comprising:

a. an interface configured to receive a first position signal indicative of the vertical position of said first vertically moveable superstructure and a second position signal indicative of the vertical position of said second vertically moveable superstructure; and

b. a first circuit operably configured to generate a vertical trajectory signal for said first and second vertically moveable structures

71. The controller of claim 70, further comprising a raise circuit responsive to said vertical trajectory signal and operably configured to generate a first raise signal for said first vertically moveable superstructure and to generate a second raise signal for said second vertically moveable superstructure.