Vehicle load weighing system and load cells for such systems

• US 20040226755A1
• Filed: 05/13/2003
• Published: 11/18/2004
• Est. Priority Date: 05/13/2003
• Status: Active Grant

• Current Assignee: Dynamic Datum LLC
• Original Assignee: Dynamic Datum LLC
• Inventors: Inalsingh, Amar, Pottebaum, James R.
• Granted Patent: US 7,009,118 B2
• Time in Patent Office: Days
• US Class Current: 177/25.13
• CPC Class Codes: G01G 19/12 having electrical weight-sensitive devices
• CPC Class Codes: G01G 23/3735 using a digital network
• CPC Class Codes: Y10S 177/09 Scale bearings

Abstract

The present invention relates to a load cell operable with a vehicle having a chassis and a container carried by the chassis, with the load cell supported by the chassis and supporting the container for measuring the weight of the container and any load therein, and to a system having a plurality of these load cells on a vehicle, and to a method of executing weight measurements of loads in a container of a vehicle. The load cell includes a plurality of strain gauges and coupling elements in a floating mount configuration for coupling the load cell to the container and to the chassis in a dual shear beam loading configuration, while limited translational movement is permitted of the load cell relative to the container or the chassis. The load cell also has an electrical interface for receiving analog output data from the strain gauges, adaptively filtering this data and outputting a digital signal representative of the weight of the container and any load therein. This invention permits measurement of incremental loads with sufficient accuracy to permit customer billing based on the measurements.

Claims

1. A high precision load cell comprising:

a. a housing,

b. a plurality of Wheatstone bridges each comprising four strain gauges, each Wheatstone bridge having input terminals and output terminals, the inputs of said plurality of Wheatstone bridges being connected to a reference voltage and a ground plane and the output analog signals being indicative of strain applied to said load cell,

c. a plurality of amplifiers receiving and amplifying output from said plurality of Wheatstone bridges respectively,

d. an analog-to-digital converter receiving and converting output of said amplifiers into a digital format indicative of said strain,

e. a programmable read only memory,

f. a network interface,

g. a microprocessor receiving outputs from said analog-to-digital converter, read only memory and network interface,

h. software programs resident in said programmable read only memory for adaptively filtering digital data and for executing at least one of the routines of;

(i) adjusting digital data for factory setting,

(ii) adjusting for coarse gain correction, and

(iii) compensating for non-linearity,

wherein;

said microprocessor executes said software programs which adaptively filters said digital data and executes at least one of the following routines;

adjusts said digital data for said factory zero, performs said coarse gain adjustment, performs non-linearity compensation on said digital data, and averages said filtered and compensated strain data from said four strain gauges of each of said Wheatstone bridges, and

said microprocessor outputs said filtered and compensated digital data using said network interface.

2. A high precision load cell according to claim 1, further comprising a temperature sensor for measuring the temperature of said load cell, said software programs further including a program for compensating for temperature changes in said load cell by performing temperature compensation for zero on said filtered digital data.

3. A high precision load cell according to claim 1 wherein said software programs including a program which averages said digital data from said strain gauges before said data is filtered.

4. A high precision load cell according to claim 1, wherein said plurality of Wheatstone bridge strain gauges comprises four Wheatstone bridge strain gauges mounted on said load cell in a dual shear beam configuration.

5. A high precision load cell according to claim 1 further comprising a plurality of analog-to-digital converters which convert each of said analog signals indicative of strain to a digital format from each of said strain gauges respectively before each of said signals is amplified.

6. A high precision load cell according to claim 1, wherein said software program for adaptively filtering digital data is modifiable by parameters received via said network interface.

7. A high precision load cell according to claim 1, wherein said network interface is a controller area network interface.

8. A high precision load cell according to claim 1, wherein said load cell further comprises:

a. a position locating resistor,

b. a chassis connector, and

c. a unique resistor located in said chassis connector external to said high precision load cell, wherein;

(i) said position locating resistor forms a voltage divider with said unique resistor located in said chassis connector,

(ii) said voltage divider generates a unique voltage based on the position of said load cell on the truck,

(iii) said unique voltage is measured by said analog-to-digital converter,

(iv) said measured unique voltage is read by said microprocessor,

(v) said microprocessor compares said measured unique voltage to entries on a look-up table, and

(vi) said microprocessor issues a message on said network interface identifying said load cell location on said truck.

9. A high precision load cell according to claim 3, wherein said plurality of Wheatstone bridge strain gauges comprise four Wheatstone bridge strain gauges mounted on said load cell in a dual shear beam configuration.

10. A high precision load cell according to claim 3, wherein said network interface is a controller area network interface.

11. A high precision load cell according to claim 3, wherein said software program for adaptively filtering digital data is modifiable by parameters received via said network interface.

12. A high precision load cell according to claim 3, wherein said load cell further comprises:

a. a chassis connector,

b. a position locating resistor, and

c. a unique resistor is located in said chassis connector external to said high precision load cell, wherein;

(i) said position locating resistor forms a voltage divider with a unique resistor located in said chassis connector,

(ii) said voltage divider generates a unique voltage based on the position of said load cell on the truck,

(iii) said unique voltage is measured by said analog-to-digital converter,

(iv) said measured unique voltage is read by said microprocessor,

(v) said microprocessor compares said measured unique voltage to entries on a look-up table, and

(vi) said microprocessor issues a message on said network interface identifying said load cell location on said truck.

13. A high precision load cell according to claim 5, wherein said plurality of Wheatstone bridge strain gauges comprises four Wheatstone bridge strain gauges mounted on said load cell in a dual shear beam configuration.

14. A high precision load cell according to claim 5, wherein said adaptive filter software program receives parameters via the network interface that modify said adaptive filter software operation.

15. A high precision load cell according to claim 5, wherein said network interface is a controller area network interface.

16. A high precision load cell according to claim 4, wherein said load cell further comprises:

a. a chassis connector,

b. a position locating resistor, and

c. a unique resistor is located in said chassis connector external to said high precision load cell, wherein;

(i) the position locating resistor forms a voltage divider with a unique resistor located in said chassis connector,

(ii) said voltage divider generates a unique voltage based on the position of the load cell on said truck,

(iii) said unique voltage is measured by the analog-to-digital converter,

(iv) said measured unique voltage is read by said microprocessor,

(v) said microprocessor compares said measured unique voltage to entries on a look-up table, and

(vi) said microprocessor issues a message on the network interface identifying the load cell location on the truck.

19. The load weighing system according to claim 16 further comprising:

a. a plurality of high precision load cells with position locating resistors, and

b. a truck chassis network harness with unique resistors connecting a pin of said chassis connector to a voltage, wherein said load cells report each load cell position on said truck via said network wiring harness to said system controller.

23. The load weighing system according to claim 19, further comprising a printer, wherein said system controller directs said printer to print the calculated weight measurement on a printable medium.

17. A load weighing system for weighing individual loads put onto a container carried by the chassis of a vehicle comprising:

a. at least three high precision load cells, each including at least one Wheatstone bridge strain gauge,

b. system controller software, network wiring, and a system controller comprising;

(i) processing means,

(ii) programmable read only memory,

(iii) network interface circuit means, and

(iv) user interface means,

wherein;

said high precision load cells are mounted between said vehicle chassis and said vehicle container to provide data from said Wheatstone bridge strain gauges indicative of weight of said container and load thereon,

said high precision load cells and said system controller are connected electronically by said network wiring,

said system controller receives commands from a user on a user interface,

said system controller issues commands using said network interface for directing said load cells to report weight, and

said load cells transmit filtered and compensated digital strain data to said system controller which calculates and displays weight.

18. A load weighing system according to claim 17 further comprising a tilt sensor for indicating tilt of said container, wherein

a. said system controller directs said tilt sensor to report tilt of said container,

b. said tilt sensor reports tilt angles,

c. said system controller calculates weight from load cell weight readings and tilt sensor tilt angle readings, and

d. said system controller displays calculated weight reading.

20. The load weighing system according to claim 17, further comprising:

a. a chassis connector,

b. a plurality of high precision load cells with position locating resistors, and

c. a truck chassis network wiring harness with unique resistors connecting a pin of said chassis connector to a voltage,

wherein;

said load cells report each load cell position on the truck via the network wiring harness to the system controller, and said system controller calculates load weight using load cell weight measurement, load cell position on the truck and tilt sensor tilt angle readings.

21. The load weighing system according to claim 17, further comprising a printer wherein said system controller directs said printer to print the calculated weight measurement on a printable medium.

22. The load weighing system according to claim 18, further comprising a printer, wherein said system controller directs said printer to print the calculated weight measurement on a printable medium.

24. The load weighing system according to claim 20, further comprising a printer, wherein said system controller directs said printer to print the calculated weight measurement on a printable medium.

25. A load weighing system according to claim 17, wherein:

a. a user issues an instruction on said user interface means for the load weighing system to start an incremental pick-up,

b. said system controller receives said load cell and said tilt sensor data,

c. said system controller calculates a start weight based on said load cell and tilt sensor start weight data,

d. said system controller waits for a user command,

e. said user issues an instruction on said user interface means for the load weighing system to complete an incremental pick-up,

f. said system controller receives said load cell and said tilt sensor data,

g. said system controller calculates a complete weight based on said load cell and said tilt sensor complete weight data,

h. said system controller calculates incremental load pick-up weight by subtracting said start weight from said complete weight, and

i. said system controller displays said incremental load pick-up weight.

26. The load weighing system according to claim 25, further comprising a printer and a printer interface, wherein the system controller directs said printer to print said calculated weight measurements on a printable medium.

27. The load weighing system according to claim 25, wherein said system controller further comprises a non-volatile memory, and wherein said system controller stores weight measurement data and customer data in said non-volatile memory.

28. The load weighing system according to claim 26, further comprises a printer and said system controller further comprising a printer interface wherein said system controller directs said printer to print load measurements and cumulative weight readings on a printable medium.

29. The load weighing system according to claim 26, wherein said system controller further comprises a non-volatile memory, and wherein said system controller stores weight measurement data and customer data in said non-volatile memory.

30. The load weighing system according to claim 28, wherein said system controller stores weight measurement data, customer data, and cumulative weight data in said non-volatile memory.

31. The load weighing system according to claim 25, wherein:

a. said system controller issues commands to said load cells and said tilt sensor requesting load weight data after said user issues an instruction to start an incremental pickup, and

b. said system controller issues commands to said load cells and said tilt sensor requesting load weight data after said user issues an instruction to complete an incremental pickup.

32. A load weighing system according to claim 25, further comprising:

a. a global positioning system receiver,

b. a non-volatile memory,

c. a system controller interface for said global positioning system receiver, wherein;

(i) said system controller receives the vehicle location from said global positioning system receiver, and said system controller stores said vehicle location and vehicle load measurements in said non-volatile memory.

33. A method of measuring a weight using a load cell comprising:

a. generating a plurality of voltages indicative of strain on a dual shear beam strain gauge,

b. digitizing said plurality of voltages with an analog to digital converter,

c. reading said plurality of digitized voltages with a microprocessor,

d. averaging said plurality of digitized voltages with said microprocessor,

e. performing at least one of the following routines;

(i) compensating said averaged, digitized voltages for a factory zero setting,

(ii) adjusting a coarse gain of said compensated, averaged, digitized voltages,

(iii) compensating for temperature zero setting based on factory established calibration constants of said adjusted, compensated, averaged, digitized voltages,

(iv) compensating said adjusted, compensated, averaged, digitized voltages for strain gauge non-linearity to obtain a current compensated measurement,

f. filtering the compensated strain gauge reading, and

g. outputting the filtered, compensated measurement.

34. The method of measuring weight according to claim 33, further comprising filtering the compensated strain gauge reading by:

a. establishing a window around the previous filtered, compensated measurement by adding and subtracting a tolerance value to said previous filtered, compensated measurement,

b. comparing current compensated measurement to a previous filtered, compensated measurement,

(i) if the current compensated measurement is outside the window, decreasing the filter factor,

(ii) if the current compensated measurement is within said window, increasing said filter factor,

c. calculating a new current filtered, compensated measurement by subtracting the previous filtered, compensated measurement divided by said filter factor from said previous filter factor and adding the current compensated measurement divided by the current filter factor to obtain a current filtered, compensated measurement, and

d. replacing the previous filtered, compensated measurement with the current filtered, compensated measurement.

36. The method of claim 33, further comprising:

a. sending to said load cell updated parameters for processing said plurality of digitized voltages, and

b. processing said plurality of digitized voltages in accordance with the updated parameters.

35. A method of measuring the weight of a load in a truck container supported by a plurality of load cells which are supported by a truck chassis, comprising:

a. initiation by an operator of the load weight measurement before a load is added to said container,

(i) receiving data from said plurality of load cells reflecting weight on said plurality of load cells,

(ii) receiving data from a tilt sensor reflecting two axes of tilt of said truck container, and

(iii) calculating the initial truck container weight from said data from said plurality of load cells and from said tilt sensor, and

b. initiation by an operator of a load weight measurement after said load is added,

(i) receiving data from said plurality of load cells reflecting weight on said plurality of load cells,

(ii) receiving data from said tilt sensor reflecting two axes of tilt of said truck container,

(iii) calculating the initial truck container weight from said data from said plurality of load cells and from said tilt sensor, and

(iv) displaying the load weight on an operator display.

37. The method of claim 35, further comprising printing said load weight on a printing apparatus.

38. The method of claim 37, further comprising storing said load weight data in a non-volatile memory.

39. A method of measuring the weight of a load in a truck container supported by a plurality of load cells which are supported by a truck chassis, comprising:

a. initiation of the load weight measurement before a load is added to said container,

(i) receiving data from said plurality of load cells reflecting weight on said plurality of load cells,

(ii) receiving data from a tilt sensor reflecting two axes of tilt of said truck container,

(iii) calculating the initial truck container weight from said data from said plurality of load cells and from said tilt sensor, and

b. initiation of a load weight measurement after said load is added,

(i) receiving data from said plurality of load cells reflecting weight on said plurality of load cells,

(ii) receiving data from said tilt sensor reflecting two axes of tilt of said truck container,

(iii) calculating the initial truck container weight from said data from said plurality of load cells and from said tilt sensor, and

(iv) displaying the load weight on an operator display.

40. A load weight measuring system comprising:

a. a plurality of load cells with serial communications capability to transmit measurements of weight, and

b. a controller to receive weight measurements from said plurality of load cells,

wherein said plurality of load cells transmits weight measurements to said controller and said controller calculates the weight.

41. A load weight measuring system comprising:

a. a plurality of load cells with serial communications capability and a first resistor which is connected to a second resistor in a serial communications bus which has a unique value and said first resistor is also connected to a voltage,

b. a system controller to receive weight measurement and position data from said load cell, wherein each load cell determines said load cell position in the system by measuring the unique voltage generated by the connection of a voltage to said first resistor and the division of said voltage between said first and second resistor, and communicates that position to said system controller.

50. A load cell according to claim 41 further comprising for each of said engaged support elements and force contact areas, a translational limiting means for allowing limited lengthwise and transverse motion of said load cell relative to said supports.

51. A load cell according to claim 50 further comprising for each of said engaged support elements and force contact areas means for allowing limited vertical motion of said load cell relative to each of said supports.

52. A load cell according to claim 50 wherein each of said translational limiting means comprises a lengthwise directed first tongue and groove structure on said slip surface and support element respectively, and a transverse direction second tongue and groove structure on said slip surface and support element respectively.

53. A load cell according to claim 52 wherein said tongue element for both lengthwise and transverse direction is formed on said load cell force contact area, and said groove element for both lengthwise and transverse directions is formed on said support element.

54. A load cell according to claim 51 wherein said means for allowing limited vertical motion comprises a bolt extending between each of said supports and said load cell block.

42. A load cell operable with a vehicle having a chassis part and a container part carried by said chassis part, said load cell supported by said chassis part and supporting said container part for measuring the weight of said container part and any load therein, said load cell comprising:

a. a block having top and bottom surfaces, first and second ends in the lengthwise direction, front and rear sides, first and second force contact areas spaced apart in the lengthwise direction on one of said bottom and said top surfaces of said block, and a third force contact area on the other of said bottom and top surfaces situated in said lengthwise direction between said first and second force contact areas,

b. first and second coupling means for coupling said first and second force contact areas respectively to one of said container and chassis parts to receive a downward or upward force respectively therefrom, and third coupling means for coupling said third force contact area to the other of said container and chassis parts to receive a downward or upward force respectively therefrom, thus establishing a dual shear beam loading configuration,

c. at least one strain gauge mounting area on said front side of said block, positioned lengthwise between said first and third force contact areas,

d. at least one strain gauge mounted to each of said at least one strain gauge mounting areas,

e. at least one of said first, second and third coupling means comprising an engaging surface which is slidable for lengthwise and transverse movement relative to the force contact area it engages on said block, while a vertical force is applied between said coupling means and the force contact area it engages, and

f. electrical interface means for receiving analog output data from said at least one strain gauge and outputting a digital signal representative of said weight of said container and any load therein.

43. A load cell according to claim 42 further comprising

a. a second strain gauge mounting area on said front side of said block, positioned lengthwise between said third and second force contact areas,

b. a second strain gauge mounted to said second strain gauge mounting area;

c. said interface means adapted for receiving and averaging said output data from said first and second strain gauges and outputting a digital signal representative of said weight of said container and any load therein.

44. A load cell according to claim 42 further comprising:

a. a third strain gauge mounting area on said rear side of said block positioned behind and opposite said first strain gauge mounting area,

b. a third strain gauge being mounted to said third strain gauge mounting area,

c. said interface means adapted for receiving and averaging said output data from said first and third strain gauges and outputting a digital signal representative of said weight of said container and any load therein.

45. A load cell according to claim 43 further comprising:

a. third and fourth strain gauge mounting areas on said rear side of said block positioned behind and opposite said first and second strain gauge mounting areas respectively,

b. third and fourth strain gauges being mounted to said third and fourth strain gauge mounting areas respectively,

c. said interface means adapted for receiving and averaging said output data from said first, second, third and fourth strain gauges and outputting a digital signal representative of said weight of said container and any load therein.

46. A load cell according to claim 45 wherein each of said load cells comprises a Wheatstone bridge of four strain gauges, each mounted at a 45°

angle with respect to the lengthwise axis of said block and each oriented at a 90°

angle with respect to the adjacent strain gauges.

47. A load cell according to claim 44 wherein said first strain gauge mounting area is formed as a recess extending inwardly from said front side toward said rear side, and said third strain gauge mounting area is formed as a recess extending inwardly from said rear side toward said front side, said first and third recesses extending toward but not reaching each other, the bottoms of these recesses defining between them a first internal wall extending in a vertical plane in said lengthwise direction and having front and rear faces, one of said strain gauges mounted on each of said front and rear faces respectively of said first internal wall.

48. A load cell according to claim 47 wherein said second and fourth strain gauge mounting areas are formed as recesses, similarly as said recesses on said first and third strain gauge mounting areas, the bottom of these recesses defining between them a second internal wall similar to said first internal wall with strain gauges mounted on said front and rear faces respectively of said second internal wall, said interface means adapted for receiving and averaging said output data from said first, second, third and fourth strain gauges and outputting a digital signal representative of said weight of said container and any load therein.

49. A load cell according to claim 42, wherein said first and second coupling means comprise first and second support elements respectively fixed to said chassis, wherein each of said first and second force contact areas of said load cell comprises a slip surface which engages one of said support elements and allows said lengthwise and transverse movement of said slip surface relative to said support element it engages.

55. A load cell according to claim 48 wherein said first and second coupling means comprises first and second support elements respectively fixed to said container, wherein each of said first and second force contact areas of said load cell comprises a slip surface which engages one of said support elements and allows lengthwise and transverse movement of said slip surface relative to said support element it engages.

56. A load cell according to claim 55 further comprising for each of said engaged support elements and force contact areas means for allowing limited vertical motion of said load cell relative to each of said supports.

57. A load cell according to claim 45 further comprising sealant in each of said recesses for sealing said array of strain gauges therein.

58. A load vehicle weighing system comprising a plurality of at least three load cells as defined in claim 43, said load cells being spaced apart for supporting said container and being electrically coupled.

59. A vehicle load weighing system according to claim 43 wherein said vehicle is a truck and said plurality of load cells comprises three load cells situated at the front, middle and rear on the right side respectively of said chassis and three additional load cells situated at the front, middle and rear on the left side respectively of said chassis.

60. A load cell according to claim 43 wherein said interface means is adapted to receive and amplify analog signals indicative of strain from said strain gauges and to convert said amplified analog signals to digital format, and to adaptively filter said digital data.

61. A load cell according to claim 60 wherein said microprocessor adaptively filters said digital data by at least one of the following:

a. adjusts said digital data relative to a factory setting,

b. adjusts for coarse gain connection,

c. compensates for temperature effects, and

d. compensates for non-linearity.

62. A method of enhancing the environment by increasing the amount of recyclable waste that is recycled instead of being, disposed of with other non-recyclable waste, comprising the steps of:

a. creating greater incentive for persons and businesses to separate recyclable from non-recyclable waste and to arrange the former to be recycled by,

b. providing an on-board weighing system on a waste pick-up vehicle,

c. adapting said on-board weighing system to measure incremental loads with accuracy to the nearest one pound, and

d. providing a billing system for charging customers for the waste removed according to the weight measured by said on-board weighing system to the nearest pound.