Crane motion control
Methods of detection and prevention for snags or off center lifts, and auto-centering a crane over a load. Snag detection includes monitoring angular deflection of the load with respect to an at-rest position, and halting movement of the crane in a direction of increasing angular deflection. Controlling off center lifting includes detecting a side load condition for a load, and preventing a hoist operation when the side load condition is detected. Auto-centering a load includes determining a position of a block coupled to the load with respect to a trolley of the crane, and centering the trolley over the block prior to a moving operation. Centering includes comparing a position of a block marker using a trolley camera to a known centered position of the marker with respect to the camera, and moving the trolley to match the determined position of the marker to its known centered position.
1. A crane motion detection system, comprising:
a camera configured to mount on a trolley of a crane;
a marker configured to mount on a block of the crane within a field of view of the camera; and
a controller coupled to the camera to receive data from the camera, and coupled to the crane to control operation of the crane in response to camera data;
wherein the controller is configured to control operation of at least one of detecting and preventing off center lifts with the block, detecting and preventing snagging of a block, and auto-centering the crane over a block.
2. The crane motion detection system of claim 1 , wherein the marker is a fiducial marker.
3. The crane motion detection system of claim 1 , wherein the marker is a reflective marker.
4. The crane motion detection system of claim 1 , wherein the marker is a pattern.
5. The crane motion detection system of claim 1 , wherein the controller is configured to control detecting and preventing off-center lifts with the block by:
detecting a side load condition on a block of the crane; and
preventing a hoist operation when the side load condition is detected.
6. The crane motion detection system of claim 5 , wherein the controller is further configured to detect a side load condition by determining a displacement of the block of the crane between a known at-rest position of the block and a current position of the block of the crane.
7. The crane motion detection system of claim 6 , wherein the controller is further configured to determine a displacement by capturing, with the camera, an image of the block in its current position, and comparing the current position to a known at-rest position of the block.
8. The crane motion detection system of claim 6 , wherein the controller is configured to estimate a known at-rest position by determining a distance of the block from the camera by comparing a size of a fiducial marker image associated with the block with results of a mathematical function or functions that relate the distance of the block from the camera to the size of a fiducial marker image associated with the block.
9. The crane motion detection system of claim 6 , wherein the controller is configured to estimate the known at-rest position by determining a distance of the block from an image capture element by comparing a size of a fiducial marker image associated with the block with results of a calibration that relates the distance of the block from the image capture element to the size of a fiducial marker image associated with the block.
10. The crane motion detection system of claim 9 , wherein the calibration is obtained using a mathematical function or functions related to a size of the fiducial marker image at two known distances from the image capture element.
11. The crane motion detection system of claim 1 , wherein the controller is configured to prevent a hoist operation when a displacement of a block of the crane between a known at-rest position of the block and a current position of the block exceeds a predetermined threshold.