Determining pile height for autonomous pile driving system

1 . A method comprising:

measuring, by a range finder of an autonomous quality control system, a horizontal distance between the range finder and a first pile installed at a first location;

iteratively tilting, by the autonomous quality control system, the range finder upwards until the range finder no longer detects the first pile;

determining, by the autonomous quality control system, an angle of the range finder relative to horizontal when the range finder no longer detects the first pile;

determining, by the autonomous quality control system, a first height of the first pile based on the horizontal distance and the determined angle; and

installing, by a pile driving system, a second pile at a second height within a threshold height of the first height.

2 . The method of claim 1 , wherein the range finder is coupled to a chute for stabilizing a pile as the pile is being driven into the ground, and wherein the method further comprises:

positioning the chute at a second location where the second pile is to be installed, wherein the horizontal distance to the first pile installed at the first location is measured by the range finder while the chute is positioned at the second location.

3 . The method of claim 2 , wherein the chute is further coupled with an inertial measurement unit (IMU), and wherein the method further comprises:

determining the angle of the range finder using an output of the IMU.

4 . The method of claim 2 , further comprising:

accessing a pile-to-pile height difference threshold indicating a maximum permissible installed height difference between the first pile and the second pile;

accessing a target height of the first pile at the first location per a pile plan;

accessing a target height of the second pile at the second location per the pile plan; and

determining the second height of the second pile to be installed at the second location based on the target height of the first pile and the second pile, the first height of the first pile installed at the first location, and the pile-to-pile height difference threshold.

5 . The method of claim 1 , wherein iteratively tilting the range finder upwards comprises:

iteratively incrementing a pitch angle of the range finder starting from horizontal by a predetermined coarse measurement step to identify an overshoot angle where the range finder overshoots the first pile and an undershoot angle immediately preceding the overshoot angle where the range finder detected the first pile.

6 . The method of claim 5 , wherein iteratively tilting the range finder upwards further comprises:

iteratively incrementing the pitch angle of the range finder starting from the undershoot angle by a predetermined fine measurement step to identify the angle of the range finder relative to horizontal when the range finder no longer detects the first pile, wherein a step size of the predetermined fine measurement step is smaller than a step size of the predetermined coarse measurement step.

7 . The method of claim 1 , wherein the angle of the range finder relative to horizontal when the range finder no longer detects the first pile is an angle that corresponds to a top of the first pile installed at the first location.

8 . An autonomous pile driving system, comprising:

a pile driver for driving piles into the ground;

a chute for stabilizing the piles as the piles are being driven into the ground;

a range finder coupled to the chute; and

a controller configured to:

autonomously measure, using the range finder, a horizontal distance between the range finder and a first pile installed at a first location;

iteratively tilt the range finder upwards until the range finder no longer detects the first pile;

autonomously determine an angle of the range finder relative to horizontal when the range finder no longer detects the first pile;

autonomously determine a first height of the first pile based on the horizontal distance and the determined angle; and

autonomously install, using the pile driver, a second pile at a second height within a threshold height of the first height.

9 . The autonomous pile driving system of claim 8 , wherein the controller is further configured to:

autonomously position the chute at a second location where the second pile is to be installed, wherein the horizontal distance to the first pile installed at the first location is measured by the range finder while the chute is positioned at the second location.

10 . The autonomous pile driving system of claim 9 , further comprising an inertial measurement unit (IMU), and wherein the controller is further configured to:

autonomously determine the angle of the range finder using an output of the IMU.

11 . The autonomous pile driving system of claim 9 , wherein the controller is further configured to:

access a pile-to-pile height difference threshold indicating a maximum permissible installed height difference between the first pile and the second pile;

access a target height of the first pile at the first location per a pile plan;

access a target height of the second pile at the second location per the pile plan; and

autonomously determine the second height of the second pile to be installed at the second location based on the target height of the first pile and the second pile, the first height of the first pile installed at the first location, and the pile-to-pile height difference threshold.

12 . The autonomous pile driving system of claim 8 , wherein the controller configured to iteratively tilt the range finder upwards comprises the controller configured to:

iteratively increment a pitch angle of the range finder starting from horizontal by a predetermined coarse measurement step to identify an overshoot angle where the range finder overshoots the first pile and an undershoot angle immediately preceding the overshoot angle where the range finder detected the first pile.

13 . The autonomous pile driving system of claim 12 , wherein the controller configured to iteratively tilt the range finder upwards comprises the controller further configured to:

iteratively increment the pitch angle of the range finder starting from the undershoot angle by a predetermined fine measurement step to identify the angle of the range finder relative to horizontal when the range finder no longer detects the first pile, wherein a step size of the predetermined fine measurement step is smaller than a step size of the predetermined coarse measurement step.

14 . The autonomous pile driving system of claim 8 , wherein the angle of the range finder relative to horizontal when the range finder no longer detects the first pile is an angle that corresponds to a top of the first pile installed at the first location.