Method and apparatus for determining a weight of a payload

• US 6,518,519 B1
• Filed: 08/30/2000
• Issued: 02/11/2003
• Est. Priority Date: 08/30/2000
• Status: Expired due to Fees

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Duffy, Joseph, Crane, Carl D. III
• Primary Examiner(s): Gibson, Randy W.
• Application Number:
  US09/651,173
• Time in Patent Office: 895 Days
• Field of Search: 177/136, 177/139, 177/141, 702/174, 701/50
• US Class Current: 177/136
• CPC Class Codes: E02F 9/264 Sensors and their calibration for indicating the position of the work tool

Abstract

Methods and apparatuses for determining a mass of a payload in a work machine. The work machine has a chassis, a cab coupled with the chassis, and a boom coupled with the cab. A first actuator is coupled with the boom and the cab and moves the boom relative to the cab. The work machine has a stick coupled with the boom, and a second actuator coupled with the stick and the boom that moves the stick relative to the boom. The work machine also has a bucket operable to receive the payload. The bucket is coupled with the stick, and a third actuator is coupled with the bucket and the stick and moves the bucket relative to the stick. A first joint angle of the boom relative to the cab is determined at at least two instances in time. A second joint angle of the stick relative to the boom is determined at at least two instances in time. A third joint angle of the bucket relative to the stick is determined at at least two instances in time. A first actuator force exerted on the first actuator is determined at at least two instances in time. A second actuator force exerted on the second actuator is determined at at least two instances in time. A third actuator force exerted on the third actuator is determined at at least two instances in time. A plurality of physical characteristics of the work machine is determined. The mass of the bucket and payload is determined as a function of the first joint angles, the second joint angles, the third joint angles, the first actuator forces, the second actuator forces, the third actuator forces, and the plurality of predetermined physical characteristics.

Claims

1. An apparatus for determining a mass of a payload in a work machine, the work machine having a chassis, a cab coupled with the chassis, a boom coupled with the cab, a first actuator coupled with the boom and the cab and operable to move the boom relative to the cab, a stick coupled with the boom, a second actuator coupled with the stick and the boom and operable to move the stick relative to the boom, a bucket operable to receive the payload, the bucket coupled with the stick, and a third actuator coupled with the bucket and the stick and operable to move the bucket relative to the stick, the apparatus comprising:

a first sensing device coupled with the boom and operable to transmit a boom angle signal as a function of a boom angle of the work machine;

a second sensing device coupled with the stick and operable to transmit a stick angle signal as a function of a stick angle of the work machine;

a third sensing device coupled with the bucket and operable to transmit a bucket angle signal as a function of a bucket angle of the work machine;

a fourth sensing device coupled with the first actuator and operable to transmit a first actuator force signal as a function a first force exerted on the first actuator;

a fifth sensing device coupled with the second actuator and operable to transmit a second actuator force signal as a function a second force exerted on the second actuator;

a sixth sensing device coupled with the third actuator and operable to transmit a third actuator force signal as a function a third force exerted on the third actuator; and

a processing device coupled with the first through sixth sensing devices to receive the respective transmitted signals at at least two instances in time, the processing device operable to determine a mass of the bucket and payload as a function of the received signals and a plurality of predetermined physical characteristics of the work machine.

2. The apparatus of claim 1 wherein the processing device is operable to analytically determine the mass of the bucket and payload.

3. The apparatus of claim 1 wherein the processing device is operable to non-empirically determine the mass of the bucket and payload.

4. The apparatus of claim 1 wherein the processor is operable to determine the mass of the bucket and payload while at least one of the boom, the stick, and the bucket is in motion.

5. The apparatus of claim 1 wherein the processing device is operable to determine the mass of the bucket and payload using a least squares approach.

6. The apparatus of claim 1 wherein the plurality of predetermined characteristics comprises a plurality of:

a mass of the cab;

a mass of the boom;

a mass of the stick;

a mass of the bucket;

a location of center of mass of the cab;

a location of center of mass of the boom;

a location of center of mass of the stick;

a location of center of mass of the bucket;

a moment of inertia of the cab;

a moment of inertia of the boom;

a moment of inertia of the stick;

a moment of inertia of the bucket; and

a plurality of geometries of the work machine.

7. The apparatus of claim 1 wherein the processing device is operable to determine the mass of the bucket and payload (M₄) as a function of:

$A=\left[\begin{array}{cc}{H}_1& J_1\\ H_2& J_2\\ \mathrm{⋮<br><br>}& \mathrm{⋮<br><br>}\\ H_n& J_n\end{array}\right],x=\left[\begin{array}{c}{p}_M\\ \frac{1}{M_4}\end{array}\right],b=\left[\begin{array}{c}-K_1\\ \begin{array}{c}-K_2\\ \mathrm{⋮<br><br>}\\ -K_n\end{array}\end{array}\right]$ 

x_opt=(A^TA)<sup>−

1</sup>A^Tb

wherein n is the number of instances in time that the processing device receives the respective transmitted signals.

8. The apparatus of claim 1 wherein the processing device is further operable to determine the mass of the payload as a function of the predetermined physical characteristics of the work machine.

9. The apparatus of claim 1 wherein each of the first, second, and third actuators comprise hydraulic cylinders, and each of the fourth, fifth, and sixth sensing devices comprises:

a respective first pressure sensor operable to transmit a respective first pressure signal as a function of a respective first pressure at a first location in the respective first, second, and third cylinders, the first location being at one of a head end and a rod end of the cylinder;

a respective second pressure sensor operable to transmit a respective second pressure signal as a function of a respective second pressure at a second location in the respective first, second, and third cylinders, the second location being at the other of the head end and the rod end of the cylinder; and

a respective sensor processing circuit coupled with the respective first and second pressure sensors to receive the respective first and second pressure signals, the respective sensor processing circuit operable to transmit the respective first, second, and third actuator force signals as a function of the respective first and second pressure signals.

10. The apparatus of claim 1 wherein the first, second, and third forces acting on the respective first, second, and third actuators respectively comprise a first, second, and third net force.

11. The apparatus of claim 1 wherein the first, second, and third actuators comprise at least one of:

a hydraulic cylinder; and

a motor.

12. The apparatus of claim 1, further comprising:

a seventh sensing device operable to transmit an inclination angle signal as a function of an inclination angle of the work machine, the processing device operable to receive the inclination angle signal and to determine the mass of the bucket and payload as a further function of the inclination angle signal.

13. The apparatus of claim 1 wherein the cab of the work machine is operable to rotate about the chassis, and further comprising:

an eighth sensing device operable to transmit a yaw angle signal as a function of a yaw angle of the work machine, the processing device coupled with the eighth sensing device to receive the yaw angle signal at at least two instances in time and being further operable to determine the mass of the bucket and payload as a function of the yaw angle signals.

14. The apparatus of claim 13 wherein the processor is further operable to determine the mass of the bucket and payload while the cab is in motion relative to the chassis.

15. A method for determining a mass of a payload in a work machine, the work machine having a chassis, a cab coupled with the chassis, a boom coupled with the cab, a first actuator coupled with the boom and the cab and operable to move the boom relative to the cab, a stick coupled with the boom, a second actuator coupled with the stick and the boom and operable to move the stick relative to the boom, a bucket operable to receive the payload, the bucket coupled with the stick, and a third actuator coupled with the bucket and the stick and operable to move the bucket relative to the stick, the method comprising:

determining a first joint angle of the boom relative to the cab at at least two instances in time;

determining a second joint angle of the stick relative to the boom at at least two instances in time;

determining a third joint angle of the bucket relative to the stick at at least two instances in time;

determining a first actuator force exerted on the first actuator at at least two instances in time;

determining a second actuator force exerted on the second actuator at at least two instances in time;

determining a third actuator force exerted on the third actuator at at least two instances in time;

determining a plurality of physical characteristics of the work machine; and

determining a one of a mass of the bucket and payload as a function of the first joint angles, the second joint angles, the third joint angles, the first actuator forces, the second actuator forces, the third actuator forces, and the plurality of predetermined physical characteristics.

16. The method of claim 15 wherein determining the mass of the bucket and payload comprises analytically determining the mass of the payload.

17. The method of claim 15 wherein determining the mass of the bucket and payload comprises non-empirically determining the mass of the payload.

18. The method of claim 15 wherein determining the mass of the bucket and payload occurs while at least one of the boom, stick, and bucket is in motion.

19. The method of claim 15 wherein determining the mass of the bucket and payload comprises determining the mass of the payload using a least squares approach.

20. The method of claim 15 wherein the plurality of predetermined physical characteristics comprises a plurality of:

a mass of the cab;

a mass of the boom;

a mass of the stick;

a mass of the bucket;

a location of center of mass of the cab;

a location of center of mass of the boom;

a location of center of mass of the stick;

a location of center of mass of the bucket;

a moment of inertia of the cab;

a moment of inertia of the boom;

a moment of inertia of the stick;

a moment of inertia of the bucket; and

a plurality of geometries of the work machine.

21. The method of claim 15 wherein determining the mass of the bucket and payload (M₄) comprises solving the following equation for M₄:

$A=\left[\begin{array}{cc}{H}_1& J_1\\ H_2& J_2\\ \mathrm{⋮<br><br>}& \mathrm{⋮<br><br>}\\ H_n& J_n\end{array}\right],x=\left[\begin{array}{c}{p}_M\\ \frac{1}{M_4}\end{array}\right],b=\left[\begin{array}{c}-K_1\\ \begin{array}{c}-K_2\\ \mathrm{⋮<br><br>}\\ -K_n\end{array}\end{array}\right]$ 

x_opt=(A^TA)<sup>−

1</sup>A^Tb

wherein n is the number of instances in time that the first, second, and third joint angles and first, second, and third actuator forces are determined.

22. The method of claim 15, further comprising determining the mass of the payload as a function of the predetermined physical characteristics of the work machine.

23. The method of claim 15 wherein each of the first, second, and third actuators comprise hydraulic cylinders, and determining the first, second, and third forces exerted on the actuator comprises:

determining a respective first pressure as a function of a respective first pressure at a first location in the respective first, second, and third cylinders, the first location being at one of a head end and a rod end of the cylinder;

determining a respective second pressure as a function of a respective second pressure at a second location in the respective first, second, and third cylinders, the second location being at the other of the head end and the rod end of the cylinder; and

determining a respective first, second, and third actuator forces as a function of the respective first and second pressures.

24. The method of claim 15 wherein the first, second, and third forces acting on the respective first, second, and third actuators respectively comprise a first, second, and third net force.

25. The apparatus of claim 15, further comprising:

determining an inclination angle of the work machine, and wherein determining the mass of the bucket and payload is further a function of the inclination angle.

26. The method of claim 15 wherein the cab of the work machine is operable to rotate about the chassis, and further comprising:

determining a yaw angle of the work machine at at least two instances in time and wherein determining the mass of the bucket and payload is further a function of the yaw angle.

27. The method of claim 26 wherein determining the mass of the payload comprises determining the mass of the bucket and payload while the cab is in motion relative to the chassis.

28. An apparatus for determining a mass of a payload in a work machine, the work machine having a chassis, a cab coupled with the chassis, a boom coupled with the cab, a first actuator coupled with the boom and the cab and operable to move the boom relative to the cab, a stick coupled with the boom, a second actuator coupled with the stick and the boom and operable to move the stick relative to the boom, a bucket operable to receive the payload, the bucket coupled with the stick, and a third actuator coupled with the bucket and the stick and operable to move the bucket relative to the stick, the apparatus comprising:

a first sensing device coupled with the boom and operable to transmit a boom angle signal as a function of a boom angle of the work machine;

a second sensing device coupled with the stick and operable to transmit a stick angle signal as a function of a stick angle of the work machine;

a third sensing device coupled with the bucket and operable to transmit a bucket angle signal as a function of a bucket angle of the work machine;

a fourth sensing device coupled with the first actuator and operable to transmit a first actuator force signal as a function a first force exerted on the first actuator;

a fifth sensing device coupled with the second actuator and operable to transmit a second actuator force signal as a function a second force exerted on the second actuator;

a sixth sensing device coupled with the third actuator and operable to transmit a third actuator force signal as a function a third force exerted on the third actuator; and

a processing device coupled with the first, second, and fourth through sixth sensing devices to receive the respective transmitted signals at at least two instances in time, and coupled with the third sensing device to receive the bucket angle signal at at least one instance in time, the processing device operable to determine a mass of the bucket and payload as a function of the received signals and a plurality of predetermined physical characteristics of the work machine while the bucket is relatively immobile with respect to the stick.

29. The apparatus of claim 28 wherein the processing device is operable to analytically determine the mass of the bucket and payload.

30. The apparatus of claim 28 wherein the processing device is operable to non-empirically determine the mass of the bucket and payload.

31. The apparatus of claim 28 wherein the processor is operable to determine the mass of the bucket and payload while at least one of the boom and the stick is in motion.

32. The apparatus of claim 28 wherein the processing device is operable to determine the mass of the bucket and payload using a least squares approach.

33. The apparatus of claim 28 wherein the plurality of predetermined characteristics comprises a plurality of:

a mass of the cab;

a mass of the boom;

a mass of the stick;

a mass of the bucket;

a location of center of mass of the cab;

a location of center of mass of the boom;

a location of center of mass of the stick;

a location of center of mass of the bucket;

a moment of inertia of the cab;

a moment of inertia of the boom;

a moment of inertia of the stick;

a moment of inertia of the bucket; and

a plurality of geometries of the work machine.

34. The apparatus of claim 28 wherein the processing device is operable to determine the mass of the bucket and payload (M₄) as a function of;

$A=\left[\begin{array}{cc}{H}_1& J_1\\ H_2& J_2\\ \mathrm{⋮<br><br>}& \mathrm{⋮<br><br>}\\ H_n& J_n\end{array}\right],x=\left[\begin{array}{c}{p}_M\\ \frac{1}{M_4}\end{array}\right],b=\left[\begin{array}{c}-K_1\\ \begin{array}{c}-K_2\\ \mathrm{⋮<br><br>}\\ -K_n\end{array}\end{array}\right]$ 

x_opt=(A^TA)<sup>−

1</sup>A^Tb

wherein n is the number of instances in time that the processing device receives the respective transmitted signals from the first, second, and fourth through sixth sensing devices, and the terms corresponding to motion of the bucket relative to the stick are nulled out.

35. The apparatus of claim 28 wherein the processing device is further operable to determine the mass of the payload as a function of the predetermined physical characteristics of the work machine.

36. The apparatus of claim 28 wherein each of the first, second, and third actuators comprise hydraulic cylinders, and each of the fourth, fifth, and sixth sensing devices comprises:

a respective first pressure sensor operable to transmit a respective first pressure signal as a function of a respective first pressure at a first location in the respective first, second, and third cylinders, the first location being at one of a head end and a rod end of the cylinder;

a respective second pressure sensor operable to transmit a respective second pressure signal as a function of a respective second pressure at a second location in the respective first, second, and third cylinders, the second location being at the other of the head end and the rod end of the cylinder; and

a respective sensor processing circuit coupled with the respective first and second pressure sensors to receive the respective first and second pressure signals, the respective sensor processing circuit operable to transmit the respective first, second, and third actuator force signals as a function of the respective first and second pressure signals.

37. The apparatus of claim 28 wherein the first, second, and third forces acting on the respective first, second, and third actuators respectively comprise a first, second, and third net force.

38. The apparatus of claim 28 wherein the first, second, and third actuators comprise at least one of:

a hydraulic cylinder; and

a motor.

39. The apparatus of claim 28, further comprising:

a seventh sensing device operable to transmit an inclination angle signal as a function of an inclination angle of the work machine, the processing device operable to receive the inclination angle signal and to determine the mass of the bucket and payload as a further function of the inclination angle signal.

40. The apparatus of claim 28 wherein the cab of the work machine is operable to rotate about the chassis, and further comprising:

an eighth sensing device operable to transmit a yaw angle signal as a function of a yaw angle of the work machine, the processing device coupled with the eighth sensing device to receive the yaw angle signal at at least two instances in time and being further operable to determine the mass of the bucket and payload as a function of the yaw angle signals.

41. The apparatus of claim 40 wherein the processor is further operable to determine the mass of the bucket and payload while the cab is in motion relative to the chassis.

42. A method for determining a mass of a payload in a work machine, the work machine having a chassis, a cab coupled with the chassis, a boom coupled with the cab, a first actuator coupled with the boom and the cab and operable to move the boom relative to the cab, a stick coupled with the boom, a second actuator coupled with the stick and the boom and operable to move the stick relative to the boom, a bucket operable to receive the payload, the bucket coupled with the stick, and a third actuator coupled with the bucket and the stick and operable to move the bucket relative to the stick, the method comprising:

determining a first joint angle of the boom relative to the cab at at least two instances in time;

determining a second joint angle of the stick relative to the boom at at least two instances in time;

determining a third joint angle of the bucket relative to the stick at at least one instance in time;

determining a first actuator force exerted on the first actuator at at least two instances in time;

determining a second actuator force exerted on the second actuator at at least two instances in time;

determining a third actuator force exerted on the third actuator at at least two instances in time;

determining a plurality of physical characteristics of the work machine; and

determining a one of a mass of the bucket and payload as a function of the first joint angles, the second joint angles, the third joint angles, the first actuator forces, the second actuator forces, the third actuator forces, and the plurality of predetermined physical characteristics while the bucket is relatively immobile with respect to the stick.

43. The method of claim 42 wherein determining the mass of the bucket and payload comprises analytically determining the mass of the payload.

44. The method of claim 42 wherein determining the mass of the bucket and payload comprises non-empirically determining the mass of the payload.

45. The method of claim 42 wherein determining the mass of the bucket and payload occurs while at least one of the boom and the stick is in motion.

46. The method of claim 42 wherein determining the mass of the bucket and payload comprises determining the mass of the payload using a least squares approach.

47. The method of claim 42 wherein the plurality of predetermined physical characteristics comprises a plurality of:

a mass of the cab;

a mass of the boom,

a mass of the stick;

a mass of the bucket;

a location of center of mass of the cab;

a location of center of mass of the boom;

a location of center of mass of the stick;

a location of center of mass of the bucket;

a moment of inertia of the cab;

a moment of inertia of the boom;

a moment of inertia of the stick;

a moment of inertia of the bucket; and

a plurality of geometries of the work machine.

48. The method of claim 42 wherein determining the mass of the bucket and payload (M₄) comprises solving the following equation for M₄:

$A=\left[\begin{array}{cc}{H}_1& J_1\\ H_2& J_2\\ \mathrm{⋮<br><br>}& \mathrm{⋮<br><br>}\\ H_n& J_n\end{array}\right],x=\left[\begin{array}{c}{p}_M\\ \frac{1}{M_4}\end{array}\right],b=\left[\begin{array}{c}-K_1\\ \begin{array}{c}-K_2\\ \mathrm{⋮<br><br>}\\ -K_n\end{array}\end{array}\right]$ 

x_opt=(A^TA)<sup>−

1</sup>A^Tb

wherein n is the number of instances in time that the first and second joint angles and first, second, and third actuator forces are determined and the terms corresponding to motion of the bucket relative to the stick are nulled out.

49. The method of claim 42, further comprising determining the mass of the payload as a function of the predetermined physical characteristics of the work machine.

50. The method of claim 42 wherein each of the first, second, and third actuators comprise hydraulic cylinders, and determining the first, second, and third forces exerted on the actuator comprises:

determining a respective first pressure as a function of a respective first pressure at a first location in the respective first, second, and third cylinders, the first location being at one of a head end and a rod end of the cylinder;

determining a respective second pressure as a function of a respective second pressure at a second location in the respective first, second, and third cylinders, the second location being at the other of the head end and the rod end of the cylinder; and

determining a respective first, second, and third actuator forces as a function of the respective first and second pressures.

51. The method of claim 42 wherein the first, second, and third forces acting on the respective first, second, and third actuators respectively comprise a first, second, and third net force.

52. The apparatus of claim 42, further comprising:

determining an inclination angle of the work machine, and wherein determining the mass of the bucket and payload is further a function of the inclination angle.

53. The method of claim 42 wherein the cab of the work machine is operable to rotate about the chassis, and further comprising:

determining a yaw angle of the work machine at at least two instances in time and wherein determining the mass of the bucket and payload is further a function of the yaw angle.

54. The method of claim 53 wherein determining the mass of the payload comprises determining the mass of the bucket and payload while the cab is in motion relative to the chassis.