Machine control system having multi-blade position coordination

1. A control system for a machine, comprising:

a first blade mountable to the machine and configured to engage a ground surface below the machine;

at least a first actuator configured to move the first blade;

a second blade mountable to the machine and configured to engage the ground surface below the machine;

at least a second actuator configured to move the second blade; and

a controller in communication with an input device configured to be manipulated by an operator to select at least one of a semi-autonomous or completely autonomous mode of operation of the machine, the at least a first actuator, and the at least a second actuator, the controller being configured to:

determine a second position of the second blade; and

upon selection by the operator of the semi-autonomous mode of operation, responsively and autonomously cause the at least a first actuator to move the first blade to a first position based on the second position of the second blade, wherein the second position is a second depth to which the second blade is pushed into the ground surface, and the first position is a first depth to which the first blade is pushed into the ground surface, and the first depth is less than the second depth and the first depth is determined based on factors that include a detected elevation of the first blade from the second blade, an elevation of the first blade from a final planned contour of the ground surface, and an elevation of the first blade from the ground surface.

2. The control system of claim 1 , wherein the second position is determined based on a command to move the at least a second actuator.

3. The control system of claim 2 , wherein the controller is further configured to automatically generate the command to move the at least a second actuator.

4. The control system of claim 3 , wherein the controller is configured to:

automatically cause the at least a first actuator to move the first blade to perform a rough cut during an excavation pass; and

automatically cause the at least a second actuator to move the second blade to perform a final cut during the excavation pass.

5. The control system of claim 2 , wherein the command to move the at least a second actuator is manually generated by an operator of the machine.

6. The control system of claim 1 , further including a sensor configured to generate a signal indicative of the second position, wherein the controller is configured to determine the second position based on the signal.

7. The control system of claim 1 , wherein:

the first blade is a dozing blade; and

the second blade is a moldboard blade.

8. The control system of claim 7 , wherein:

the at least a first actuator is configured to lift the dozing blade; and

the at least a second actuator is configured to lift the moldboard blade.

9. The control system of claim 8 , wherein the at least a second actuator is further configured to pivot the moldboard blade about a first vertical axis that is normal to the ground surface.

10. The control system of claim 1 , wherein the controller is configured to automatically cause the at least a first actuator to move the first blade to the first position based on the second position of the second blade during operation in a first mode, and based on an electronic contour plan stored in the controller and indicative of a desired contour of the ground surface during operation in a second mode.

11. The control system of claim 10 , wherein the controller is further configured to automatically cause the at least a first actuator to move the first blade to the first position based on a distance of an edge of the first blade from the ground surface located below the first blade during operation in a third mode.

12. A method of controlling a machine, comprising:

determining a ground surface position;

determining a planned contour position;

determining a second position of a second ground-engaging blade of the machine;

determining a mode of operation of the machine; and

responsive to the mode of operation of the machine, automatically causing a first ground-engaging blade of the machine to move to a first position, wherein the second position is a second depth to which the second blade is pushed into the ground surface, and the first position is a first depth to which the first blade is pushed into the ground surface, and the first depth is less than the second depth and the first depth is determined based on factors that include a detected elevation of the first blade from the second blade, an elevation of the first blade from a final planned contour of the ground surface, and an elevation of the first blade from the ground surface.

13. The method of claim 12 , wherein determining the second position includes determining the second position based on a command to move the at least a second actuator.

14. The method of claim 13 , wherein the command is automatically generated.

15. The method of claim 13 , wherein the command is manually generated.

16. The method of claim 12 , further including:

automatically causing the first ground-engaging blade to move to perform a rough cut during an excavation pass; and

automatically causing the second ground-engaging blade to move to perform a final cut during the excavation pass.

17. The method of claim 12 , wherein determining the second position includes sensing the second position.

18. The method of claim 12 , wherein:

automatically causing the first ground-engaging blade of the machine to move to the first position includes automatically causing the first ground-engaging blade of the machine to move to the first position based on a distance from the second position during operation in a first mode; and

the method further includes automatically causing the first ground-engaging blade of the machine to move to the first position based on a distance from an edge of the first ground-engaging blade to the planned contour position during operation in a second mode.

19. The method of claim 18 , further including automatically causing the first ground-engaging blade to move to the first position based on a distance from an edge of the first ground-engaging blade to the ground surface position during a third mode.

20. A machine, comprising:

a front frame having a steerable front wheel;

a rear frame having a driven rear wheel and being pivotally connected to the front frame;

a moldboard blade suspended from the front frame, between the steerable front wheel and the driven rear wheel;

a second hydraulic actuator configured to move the moldboard blade relative to the front frame;

a dozing blade mounted to the front frame forward of the steerable front wheel;

a first hydraulic actuator configured to move the dozing blade relative to the front frame;

a second sensor configured to generate a second signal indicative of a position of the moldboard blade;

a first sensor configured to generate a first signal indicative of a position of the dozing blade; and

a controller in communication with an input device configured to be manipulated by an operator to select at least a completely autonomous mode of operation of the machine, the first hydraulic actuator, the second hydraulic actuator, the first sensor, and the second sensor, the controller being configured to:

automatically cause the second hydraulic actuator to move the moldboard blade based on the second signal; and

automatically cause the first hydraulic actuator to move the dozing blade based on the first and second signals, wherein the position of the dozing blade is a first depth to which the dozing blade is pushed into a ground surface, and the position of the moldboard blade is a second depth to which the moldboard blade is pushed into the ground surface, and the first depth is less than the second depth and the first depth is determined based on factors that include a desired ratio of material that should be removed by each of the moldboard blade and the dozing blade, a known position of a final planned contour of the ground surface, and a detected position of the ground surface.