System and method for calculation of capacity charts at a locked counterweight position

1. A method for determining a capacity of a boom combination for a crane having a variable position counterweight in a locked position, the method comprising:

using a processor configured to implement computer executable instructions to perform the steps of:

determining a boom combination of the crane;

determining a maximum capacity of the crane at a hook position for the boom combination;

determining a maximum target value for an operating condition dependent on a balance of the crane between the variable position counterweight at a first distance from a center of rotation of the crane and a load on the hook;

receiving an indication of the locked counterweight position at a second distance from the center of rotation that is different than the first distance;

establishing at least one new target value for the operating condition dependent on the balance of the crane between the variable position counterweight at the second distance and the load on the hook; and,

calculating a new capacity of the crane by decrementing the maximum capacity of the crane proportionally to a difference in the maximum target value and the at least one new target value.

2. The method of claim 1 , further comprising preventing the variable position counterweight from moving to the locked position when at least one of (a) the new target value of the operating condition is greater than the maximum target value of the operating condition and (b) the new capacity of the crane is less than a minimum capacity.

3. The method of claim 1 , wherein determining the boom combination comprises receiving a user input identifying a boom combination.

4. The method of claim 1 , wherein determining the boom combination comprises detecting, by a sensor, at least one component making up the combination.

5. The method of claim 1 , wherein determining the maximum capacity comprises looking up a load chart for the determined boom combination.

6. The method of claim 1 , wherein the operating condition comprises a moment calculated about a fixed point on the crane.

7. The method of claim 6 , wherein the moment comprises summing a load moment of at least one of a counterweight support beam supporting the variable position counterweight and a rotating bed supporting the variable position counterweight, a load moment of a mast hinge supporting at least one of a fixed mast and a live mast, and a load moment of a boom hinge supporting a boom.

8. A crane control system comprising:

a processor configured to implement computer executable instructions;

a first input interface in communication with the processor and configured to receive an indication of a locked position of a variable position counterweight;

a second input interface in communication with the processor and configured to receive an input corresponding to an operating condition indicative of a balance between a load on a crane boom and a variable position counterweight;

a first output interface in communication with the processor and configured to output a control signal for controlling the position of the variable position counterweight;

a second output interface in communication with the processor and configured to output an indication of a new capacity of the crane; and,

a computer memory in communication with the processor and storing data representing a load chart and computer executable instructions, that when implemented by the processor cause the processor to perform functions comprising:

calculate the control signal for controlling the position of the variable position counterweight based on keeping the input received at the second input interface at or below a maximum target value for the operating condition dependent on a balance of the crane between the variable position counterweight at a first distance from a center of rotation of the crane and a load on the hook;

determine a maximum capacity of the crane at a hook position for the boom combination;

calculate at least one new target value for the operating condition based on the indication of the locked counterweight position received over the first interface and dependent on the balance of the crane between the variable position counterweight at a second distance that is different than the first distance and the load on the hook;

calculate a new capacity of the crane by decrementing the maximum capacity of the crane proportionally to a difference in the maximum target value and the at least one new target value; and,

output an indication of the new capacity over the second output interface.

9. The crane control system of claim 8 , wherein the processor further performs functions comprising prevent the variable position counterweight from moving to the locked position when at least one of (a) the new target value of the operating condition is greater than the maximum target value of the operating condition and (b) the new capacity of the crane is less than a minimum capacity.

10. The crane control system of claim 8 , wherein the operating condition comprises a moment calculated about a fixed point on the crane.

11. The crane control system of claim 10 , wherein the moment comprises summing a load moment of at least one of a beam counterweight support beam supporting the variable position counterweight and a frame rotating bed supporting the variable position counterweight, a load moment of a mast hinge supporting at least one of a fixed mast and a live mast, and a load moment of a boom hinge supporting a boom.

12. The crane control system of claim 8 , further comprising a third input configured to receive an indication of a boom combination.

13. The crane control system of claim 12 , wherein the function determine the maximum capacity comprises looking up the load chart for the determined boom combination.

14. A crane comprising:

an upper works;

a boom mounted to the upper works at a first end and having a hook at a second end;

a variable position counterweight horizontally extendable from the upper works;

a counterweight movement device configured to move the variable position counterweight relative to the upper works; and

a crane control system, comprising:

a processor configured to implement computer executable instructions;

a first input interface in communication with the processor and configured to receive an indication of a locked position of a variable position counterweight;

a second input interface in communication with the processor and configured to receive an input corresponding to an operating condition indicative of a balance between a load on a crane boom and a variable position counterweight;

a first output interface in communication with the processor and configured to output a control signal for controlling the position of the variable position counterweight;

a second output interface in communication with the processor and configured to output an indication of a new capacity of the crane; and,

a computer memory in communication with the processor and storing data representing a load chart and computer executable instructions, that when implemented by the processor cause the processor to perform functions comprising:

calculate the control signal for controlling the position of the variable position counterweight based on keeping the input received at the second input interface at or below a maximum target value for the operating condition dependent on a balance of the crane between the variable position counterweight at a first distance from a center of rotation of the crane and a load on the hook;

determine a maximum capacity of the crane at a hook position for the boom combination;

calculate at least one new target value for the operating condition based on the indication of the locked counterweight position received over the first interface and dependent on the balance of the crane between the variable position counterweight at a second distance that is different than the first distance and the load on the hook;

calculate a new capacity of the crane by decrementing the maximum capacity of the crane proportionally to a difference in the maximum target value and the at least one new target value; and,

output an indication of the new capacity over the second output interface.

15. The crane of claim 14 , wherein the processor further performs functions comprising prevent the variable position counterweight from moving to the locked position when at least one of (a) the at least one new target value of the operating condition is greater than the maximum target value of the operating condition and (b) the new capacity of the crane is less than a minimum capacity.

16. The crane of claim 14 , the operating condition comprises a moment calculated about a fixed point on the crane.

17. The crane of claim 16 , wherein the moment comprises summing a load moment of at least one of a beam counterweight support beam supporting the variable position counterweight and a frame rotating bed supporting the variable position counterweight, a load moment of a mast hinge supporting at least one of a fixed mast and a live mast, and a load moment of a boom hinge supporting a boom.

18. The crane of claim 14 , further comprising a third input configured to receive an indication of a boom combination.

19. The crane of claim 14 , wherein the function determine the maximum capacity comprises looking up the load chart for the determined boom combination.