Human power amplifier for lifting load with slack prevention apparatus

• US 6,886,812 B2
• Filed: 04/16/2003
• Issued: 05/03/2005
• Est. Priority Date: 05/13/1999
• Status: Expired due to Fees

• Current Assignee: Gorbel Inc
• Original Assignee: Hamayoon Kazerooni
• Inventors: Kazerooni, Hamayoon
• Primary Examiner(s): Matecki, Kathy
• Assistant Examiner(s): KIM, SANG K
• Application Number:
  US10/414,897
• Publication Number:
  US 20030189197A1
• Time in Patent Office: 748 Days
• Field of Search: 254/266, 254/270, 254/264, 254/274, 254/331, 254360-362, 414/2, 414/4, 414/5, 212/330, 212/331, 212/338, 212/285
• US Class Current: 254/270
• CPC Class Codes: B66C 1/0212 Circular shape
• CPC Class Codes: B66C 1/0243 Separate cups
• CPC Class Codes: B66C 1/0256 Operating and control devices
• CPC Class Codes: B66C 1/0275 actuated by lifting action
• CPC Class Codes: B66D 3/18 Power-operated hoists

Abstract

A human power amplifier includes an end-effector that is grasped by a human operator and applied to a load. The end-effector is suspended, via a line, from a take-up pulley, winch, or drum that is driven by an actuator to lift or lower the load. The end-effector includes a force sensor that measures the vertical force imposed on the end-effector by the operator and delivers a signal to a controller. The controller and actuator are structured in such a way that a predetermined percentage of the force necessary to lift or lower the load is applied by the actuator, with the remaining force being supplied by the operator. The load thus feels lighter to the operator, but the operator does not lose the sense of lifting against both the gravitation and inertial forces originating in the load.

Claims

1. A hoist system improving responsiveness of a hoist that includes an end-effector held by an operator and connected to a load to be lifted, a sensor in the end-effector sensing operator-applied force during lifting and sending a signal representing operator-applied force to a controller, and a hoist actuator varying speed of movement of a line transmitting tensile force from the actuator to the end-effector to assist the operator in lifting the load, the hoist system comprising:

a. a load force estimator that sends a signal to the controller representing load force; and

b. the controller controlling the actuator as a function of the estimated load force signal and the operator-applied force signal.

2. The hoist system of claim 1, wherein actuator speed is controlled as a function of the estimated load force signal and the operator-applied force signal according to the equation:

v=GK(f+f_up)+GQp+S(f+p)

wherein v represents end-effector velocity, G represents an actuator transfer function, K represents a transfer function of the controller operating on f, f represents operator-applied force, f_up is a constant, Q represents a controller transfer function operating on p, p represents estimated load force, and S represents actuator sensitivity transfer function.

3. The hoist system of claim 1, wherein the load force estimator is a force sensor.

4. The hoist system of claim 3, wherein the force sensor estimates load force as a function of tensile force on the line.

5. The hoist system of claim 3, wherein the force sensor estimates load force as a function of strain on the hoist.

6. The hoist system of claim 1, wherein the load force estimator uses current consumed by the actuator to estimate the load force.

7. The hoist system of claim 6, wherein the load force estimator includes a sensor that detects electric current flow to the actuator.

8. The hoist system of claim 1, wherein the controller is programmed so that during movement of the load the operator always bears some of the load force so that the operator feels the load during lifting movements.

9. The hoist system of claim 1, wherein the controller is programmed so that variations in lifting speed, operator-applied force and load force are functionally interrelated to require changes in lifting speed or operator-applied force in response to changing load force.

10. The hoist system of claim 1, wherein the controller responds to detection of lack of tensile force in the line by preventing unreeling of the line in response to a downward operator-applied force.

11. A method of improving the responsiveness of a hoist that includes an end-effector held by an operator and connected to a load to be lifted, a sensor in the end-effector that measures operator-applied force and sends a signal representing operator-applied force to a controller, and a hoist actuator varying speed of movement of a line transmitting tensile force from the actuator to the end-effector to assist the operator in lifting the load, the method comprising:

a. estimating load force with a load force estimator;

b. transmitting a load force signal from the load force estimator to the controller; and

c. programming the controller to control actuator speed as a function of the load force signal and the operator-applied force signal.

12. The method of claim 11, including programming the controller to control actuator speed as a function of the load force signal and the operator-applied force signal according to the equation:

e=K(f−

f_up)+Qp

wherein e represents controller output, K represents a transfer function of the controller operating on f, f represents operator-applied force, f_up represents a constant, Q represents a controller transfer function operating on p, and p represents estimated load force.

13. The method of claim 11, including estimating the load force using a force sensor.

14. The method of claim 13, including using a sensor that measures line tensile force to estimate load force.

15. The method of claim 13, including using a sensor that measures mechanical strain on the hoist to estimate load force.

16. The method of claim 11, including estimating the load force using a device that measures energy consumed by the actuator in lifting the load.

17. The method of claim 11, including programming the controller to make the actuator hold the load in a stationary position when a deadman switch on the end-effector is inactive.

18. A system for improving hoist responsiveness to operator input, wherein the hoist includes an end-effector held by an operator and connectable to a load to be lifted, a sensor in the end-effector detecting operator-imposed force during lifting and sending to a controller a signal representing operator-imposed force, a hoist actuator having an operating speed set by the controller, and a line transmitting tensile force between the actuator and the end-effector to assist the operator in lifting the load, the system comprising:

a. a load force estimator that determines a force on the line caused by a load being lifted;

b. the load force estimator sending a load force signal to the controller; and

c. the controller varying lifting speed in response to the operator-imposed force as a function of the load force signal.

19. The system of claim 18, wherein the load force signal includes a force on the line caused by the end-effector.

20. The system of claim 18, wherein the load force estimator measures tensile force on the line.

21. The system of claim 18, wherein the load force estimator measures mechanical strain on the hoist.

22. The system of claim 18, wherein the load force estimator measures energy consumed by the actuator in supporting the load.

23. A hoist system giving an operator a realistic sense of a lifting task that the operator indicates by operator-applied force to an end-effector connected to a load and connected to a hoist by a line, a signal representing operator-applied force during the lifting task being implemented by a controller, operating an actuator connected to the end-effector by the line, the system comprising:

a. a load force measurer supplying a load force signal to the controller;

b. the controller operating the actuator to implement an operator-indicated lifting task variably in response to the load force signal and the operator-applied force signal; and

c. the controller being programmed so that the operator must exert a greater operator-applied force for a heavier load than is required to raise a lighter load at the same speed.

24. The system of claim 23, wherein the load force estimator is a force sensor arranged to detect load force.

25. The system of claim 23, wherein the load force estimator derives the load force signal from current required by the actuator to support the end-effector and the load connected to it.

26. The system of claim 23, wherein for a given operator-applied downward force, an increase in load weight leads to an increased load lowering speed.

27. The system of claim 23, wherein a load weight increase without a change in load movement speed requires more operator-applied force for load raising and less operator-applied force for load lowering.

28. A method of controlling a hoist so that hand input by a hoist operator and signaling a lifting task is implemented by the hoist to give the operator a realistic sense of a mass of a load being lifted, the method comprising:

a. producing a load force signal representing force caused by being lifted; and

b. using the load force signal to drive the hoist so that the operator must increase operator-applied force to raise a heavier load at the same speed as a lighter load.

29. The method of claim 28, including deriving the load force signal from current required for the hoist to support the load.

30. The method of claim 28, including deriving the load force signal from a force sensor.

31. The method of claim 28, including reducing the operator-applied force required to lower a heavier load at the same speed as a lighter load.

32. The method of claim 28, wherein a load weight increase without a change in operator-applied force causes reduced load raising speed and increased load lowering speed.

33. The method of claim 28, wherein a load weight increase without a change in load movement speed requires more operator-applied force for load raising and less operator-applied force for load lowering.

34. An improved hoist control comprising:

a. load force estimator producing a signal as a function of the force of a load supported by the hoist; and

b. a controller driving an actuator of the hoist to vary hoist assist to the operator so that as load force increases, a given operator-applied force causes reduced load raising speed and increased load lowering speed.

35. The improvement of claim 34, wherein the load force signal is derived from current required for the actuator to support the load.

36. The improvement of claim 34, wherein the load force signal is derived from energy consumed by the actuator to support the load.

37. The improvement of claim 34, wherein the load force signal is derived from a force sensor.

38. A hoist system controlling load lifting speed responsively to operator input, the hoist system comprising:

a. a controller receiving signals representing load force and operator-applied force;

b. the controller being programmed to control lifting speed as a function of both signals; and

c. the controller being further programmed so that a change in load weight increases and a change in operator-applied force cause a change in load speed according to the equation;

(1+SE+GQE)Δ

v=(GK+S)Δ

f+(S+GQ)(Δ

W)

where S represents an actuator sensitivity transfer function, E represents load dynamics, G represents an actuator transfer function, Q represents a controller transfer function operating on p, Δ

v represents change in end-effector velocity, Δ

f represents change in operator-applied force, K represents a transfer function of the controller operating on f and Δ

W represents change in load weight.

39. The system of claim 38, wherein the controller is programmed so that an operator must apply a greater upward and a smaller downward force for a heavier load than is needed to move a lighter load at the same speed as demonstrated by the equation:

0=(GK+S)Δ

f+(S+GQ)(Δ

W)

where G represents an actuator transfer function, K represents a transfer function of the controller operating on f, S represents an actuator sensitivity transfer function, Δ

f represents change in the force imposed by the operator, Q represents a controller transfer function operating on p, and Δ

W represents change in load weight.

40. The system of claim 38, wherein the controller is programmed so that for a given weight any increase in speed of movement of the load will require additional operator-applied force according to the equation:

(1+SE+GQE)Δ

v=(GK+S)Δ

f

where S represents an actuator sensitivity transfer function, E represents load dynamics, G represents an actuator transfer function, Q represents a controller transfer function operating on p, Δ

v represents change in end-effector velocity, K represents a transfer function of the controller operating on f, and Δ

f represents change in force imposed by the operator.

41. The system of claim 38, wherein for a given operator-applied force a change in load weight will cause a corresponding change in end-effector speed according to the equation:

(1+SE+GQE)Δ

v=(S+GQ)(Δ

W)

where S represents an actuator sensitivity transfer function, E represents load dynamics, G represents an actuator transfer function, Q represents a controller transfer function operating on p, Δ

v represents change in end-effector velocity, and Δ

W represents change in load weight.

42. The system of claim 38, including a load force estimator formed as a force sensor.

43. The system of claim 38, including a load force estimator using current consumed by an actuator to estimate load force.

44. A control system for a hoist having a controller of an actuator and a hoist line extending from the actuator to an end-effector connectable to a load, the control system comprising:

a. a detector signaling the controller whenever absence of tensile force in the line occurs; and

b. the controller preventing the actuator from unreeling line in response to an operator input of downward movement whenever the signal representing absence of tensile force in the line occurs.

45. The control system of claim 44, wherein the detector is a switch in communication with the line.

46. The control system of claim 44, wherein the detector determines absence of line tensile force from detection of load force and operator input.

47. The control system of claim 44, wherein the detector determines absence of line tensile force from current required by the actuator in supporting the line.

48. The control system of claim 44, wherein the detector is capable of generating a binary signal having one state when line tensile force is zero and a second state when line tensile force is not zero.

49. The control system of claim 44, wherein the detector is capable of generating a binary signal having one state when the end-effector is constrained from moving downwardly and a second state when the end-effector is not constrained from moving downwardly.

50. The control system of claim 44, wherein the detector includes a switch that can move to one position when the line is slack and can move to another position when the line is not slack.

51. The control system of claim 44, wherein the controller issues an upward velocity command signal to generate a non-zero tensile force on the line in response to an operator input of upward movement whenever the signal from the detector represents absence of tensile force on the line.

52. A method of preventing a hoist line from becoming slack, the method comprising:

a. detecting absence of tensile force in the line;

b. signaling a controller of an actuator of the hoist whenever the line tensile force is absent; and

c. programming the controller to prevent the actuator from unreeling line in response to operator input of downward movement whenever line tensile force is absent.

53. The method of claim 52 including detecting line tensile force with a switch communicating with the line.

54. The method of claim 52 including detecting a line tensile force from load force and operator input.

55. The method of claim 52 including detecting line tensile force from energy consumed by the actuator in supporting the line.