Method for tracking lifting events at a construction site

1. A method for monitoring lift events at a construction site comprising:

accessing a first timeseries of load values output by a load sensor, coupled to a crane hook, during a first time period;

deriving a set of characteristics of an object carried by the crane hook during the first time period based on the first timeseries of load values;

selecting a load handling specification for the object based on the set of characteristics of the object;

selecting a buffer distance for the object based on the set of characteristics of the object;

accessing a georeferenced boundary of a no-fly zone proximal the construction site; and

during a second time period succeeding the first time period:

accessing a second timeseries of load values output by the load sensor;

accessing a sequence of geospatial locations of the object, output by a position sensor coupled to the crane hook, during the second time period;

in response to the second timeseries of load values deviating from the load handling specification, activating an object motion alarm for the object; and

in response to a geospatial location, in the sequence of geospatial locations of the object, falling within the buffer distance of the georeferenced boundary of the no-fly zone, activating an object location alarm.

2. The method of claim 1 , further comprising, during the second time period:

detecting a pitch orientation of the object relative to the crane hook;

detecting a yaw rate of the object based on a second timeseries of motion values;

detecting a pendulum amplitude of the crane hook based on the second timeseries of motion values;

calculating a probability of partial loss of the object based on the pitch orientation, the yaw rate, and the pendulum amplitude; and

adjusting the buffer distance proportional to the probability of partial loss of the object.

3. The method of claim 1 :

wherein deriving the set of characteristics of the object based on the first timeseries of load values comprises deriving a first lifting profile, representing transition of a first weight of the object to the crane hook over a first loading duration, from the first timeseries of load values;

further comprising:

accessing a first timeseries of motion values output by a motion sensor, coupled to the crane hook, during the first time period;

deriving a sloshing frequency of the object from the first timeseries of motion values;

identifying the object as a concrete hopper based on the first loading duration and the sloshing frequency; and

wherein selecting the load handling specification for the object comprises selecting the load handling specification, from a set of load handling specifications, for concrete hoppers in response to identifying the object as the concrete hopper;

wherein selecting the buffer distance for the object comprises selecting the buffer distance of a first magnitude for the object in response to identifying the object as the concrete hopper; and

further comprising:

accessing the second timeseries of load values output by the load sensor during a third time period;

accessing a second timeseries of motion values output by the motion sensor during the third time period;

deriving a second lifting profile, representing transition of a second weight of a second object to the crane hook over a second loading duration, from the second timeseries of load values;

deriving a natural frequency of the second object from the second timeseries of motion values;

identifying the second object as rebar based on the second loading duration and the natural frequency; and

selecting a second load handling specification, from the set of load handling specifications, for rebar in response to identifying the object as rebar; and

selecting a second buffer distance of a second magnitude, greater than the first magnitude, for the second object in response to identifying the object as rebar.

4. The method of claim 1 :

wherein activating the object motion alarm for the object comprises, in response to the second timeseries of load values deviating from the load handling specification:

transmitting a first notification for the object motion alarm to a crane operator command center; and

transmitting a second notification for the object motion alarm to mobile devices associated with rigging personnel at the construction site; and

wherein activating the object location alarm comprises, in response to the geospatial location falling within the buffer distance of the georeferenced boundary of the no-fly zone:

transmitting a third notification for the object location alarm to the crane operator command center; and

transmitting a fourth notification for the object motion alarm to a computing device associated with a site manager at the construction site.

5. A method for monitoring lift events at a construction site comprising:

accessing a first timeseries of load values output by a load sensor, coupled to a crane hook, during a first time period;

accessing a first timeseries of motion values output by a motion sensor, coupled to the crane hook, during the first time period;

deriving a lifting profile from the first timeseries of load values;

deriving an oscillation characteristic from the first timeseries of motion values;

identifying a type of an object carried by the crane hook during the first time period based on the lifting profile and the oscillation characteristic;

selecting a load handling specification for the object based on the type of the object;

accessing a second timeseries of motion values output by the motion sensor during a second time period succeeding the first time period; and

in response to the second timeseries of motion values deviating from the load handling specification, activating an object motion alarm for the object during the second time period.

6. The method of claim 5 , further comprising:

estimating a payload size of the object based on the first timeseries of load values;

recording a first geospatial location of the crane hook during the first time period;

accessing a third timeseries of load values output by the load sensor during a third time period succeeding the second time period;

detecting unloading of the object from the crane hook during the third time period based on the third timeseries of load values;

recording a second geospatial location of the crane hook during the third time period;

populating a lift event record for the object with the type of the object, the payload size of the object, a pickup location at the first geospatial location, and a drop-off location at the second geospatial location; and

in response to the second timeseries of motion values deviating from the load handling specification, writing a motion control flag to the lift event record for the object.

7. The method of claim 5 :

further comprising:

estimating a payload size of the object based on the first timeseries of load values;

accessing an altitude, output by an altimeter coupled to the crane hook, during the second time period; and

predicting a line length, carrying the crane hook, based on the altitude;

wherein selecting the load handling specification for the object comprises calculating a pendulum motion amplitude threshold for the object:

proportional to the line length; and

inversely proportional to the payload size of the object; and

further comprising calculating a magnitude of lateral oscillation of the object during the second time period based on the second timeseries of motion values; and

wherein activating the object motion alarm comprises activating the object motion alarm in response to the magnitude of lateral oscillation of the object exceeding the pendulum motion amplitude threshold during the second time period.

8. The method of claim 5 , wherein activating the object motion alarm for the object during the second time period comprises, during the second time period, in response to the second timeseries of motion values deviating from the load handling specification:

transmitting the object motion alarm to a crane operator command center; and

transmitting the object motion alarm to a mobile device associated with a site manager at the construction site.

9. The method of claim 5 :

wherein deriving the lifting profile from the first timeseries of load values comprises deriving the lifting profile, representing transition of a weight of the object to the crane hook over a loading duration, from the first timeseries of load values;

wherein deriving the oscillation characteristic from the first timeseries of motion values comprises deriving a sloshing frequency from the first timeseries of motion values;

wherein identifying the type of the object comprises identifying the object as a concrete hopper based on the loading duration and the sloshing frequency; and

wherein selecting the load handling specification for the object comprises selecting the load handling specification, from a set of load handling specifications, for concrete hoppers based on the type of the object.

10. The method of claim 9 :

wherein selecting the load handling specification for the object comprises:

estimating a fill level of the concrete hopper proportional to the sloshing frequency; and

selecting the load handling specification specifying a first pendulum amplitude threshold and a first pitch threshold inversely proportional to the fill level;

further comprising:

interpreting a first pendulum amplitude of the object during the second time period based on the second timeseries of motion values; and

interpreting a first pitch amplitude of the object during the second time period based on the second timeseries of motion values; and

wherein activating the object motion alarm for the object during the second time period comprises activating the object motion alarm in response to one of:

the first pendulum amplitude of the object exceeding the first pendulum amplitude threshold; and

the first pitch amplitude of the object exceeding the first pitch threshold.

11. The method of claim 10 , further comprising:

accessing a third timeseries of load values output by the load sensor during a third time period;

accessing a third timeseries of motion values output by the motion sensor during the third time period;

deriving a second lifting profile, representing transition of a second weight of a second object to the crane hook over a second loading duration greater than the first duration, from the third timeseries of load values;

deriving a natural frequency of the second object, greater than the sloshing frequency, from the third timeseries of motion values;

identifying the second object, carried by the crane hook during the third time period, as an elongated structural member based on the second loading duration and the natural frequency of the second object;

in response to identifying the second object as the elongated structural member, selecting a second load handling specification for the second object specifying:

a second pendulum amplitude threshold less than the first pendulum amplitude threshold; and

a pitch angle threshold;

accessing a fourth timeseries of motion values output by the motion sensor during a fourth time period succeeding the third time period;

tracking a pitch angle of the second object during the fourth time period; and

issuing a second object motion alarm for the second object during the fourth time period in response to one of:

the second pendulum amplitude of the second object exceeding the first pendulum amplitude threshold; and

the pitch angle of the second object exceeding the pitch angle threshold.

12. The method of claim 11 :

further comprising, during the fourth time period, capturing a video frame from a downward-facing camera coupled to the crane hook; and

wherein tracking the pitch angle of the second object during the fourth time period comprises:

extracting a set of features from the video frame; and

calculating the pitch angle of the second object relative to the crane hook based on the set of features.

13. The method of claim 5 :

wherein deriving the oscillation characteristic from the first timeseries of motion values comprises estimating a natural frequency of the object based on the first timeseries of motion values;

further comprising estimating a payload size of the object based on the first timeseries of load values;

wherein selecting the load handling specification for the object comprises calculating a resonance amplitude threshold at the natural frequency of the object inversely proportional to the payload size of the object;

further comprising calculating a resonance amplitude of the object at the natural frequency during the second time period based on the second timeseries of motion values; and

wherein activating the object motion alarm comprises activating the object motion alarm in response to the resonance amplitude of the object exceeding the resonance amplitude threshold at the natural frequency during the second time period.

14. The method of claim 5 , further comprising:

selecting a buffer distance for the object based on the type of the object;

accessing a georeferenced boundary of a no-fly zone proximal the construction site; and

during the second time period:

accessing a sequence of geospatial locations of the object, output by a position sensor coupled to the crane hook, during the second time period; and

in response to a geospatial location of the object falling within the buffer distance of the georeferenced boundary of the no-fly zone, activating an object location alarm.

15. The method of claim 14 , further comprising:

interpreting a pendulum amplitude of the object during the second time period based on the second timeseries of motion values; and

adjusting the buffer distance proportional to the pendulum amplitude of the object during the second time period.

16. The method of claim 14 :

wherein deriving the oscillation characteristic from the first timeseries of motion values comprises estimating a natural frequency of the object based on the first timeseries of motion values;

further comprising:

estimating a horizontal span of the object based on the type of the object and the natural frequency of the object; and

adjusting the buffer distance proportional to the horizontal span of the object during the second time period.

17. The method of claim 14 , further comprising:

annotating a geospatial map with the sequence of geospatial locations of the object;

flagging a subset of geospatial locations, within the sequence of geospatial locations of the object, that fall within the buffer distance of the no-fly zone; and

generating a lift event record defining the type of the object, indicating the object location alarm for the object, and comprising the geospatial map.

18. A method for monitoring lift events at a construction site comprising:

accessing a first timeseries of load values output by a load sensor, coupled to a crane hook, during a first time period;

deriving a set of characteristics of an object carried by the crane hook during the first time period based on the first timeseries of load values;

identifying a type of the object based on the set of characteristics;

selecting a buffer distance for the object based on the type of the object;

accessing a georeferenced boundary of a no-fly zone proximal the construction site;

accessing a sequence of geospatial locations of the object, output by a position sensor coupled to the crane hook, during a second time period succeeding the first time period; and

in response to a geospatial location, in the sequence of geospatial locations of the object, falling within the buffer distance of the georeferenced boundary of the no-fly zone, activating an object location alarm during the second time period.

19. The method of claim 18 :

further comprising:

accessing a first timeseries of motion values output by a motion sensor, coupled to the crane hook, during the first time period;

extracting an oscillation characteristic from the first timeseries of motion values;

wherein deriving the set of characteristics of the object based on the first timeseries of load values comprises extracting a lifting profile from the first timeseries of load values;

wherein identifying the type of the object comprises identifying the type of the object based on the oscillation characteristic and the lifting profile;

further comprising:

selecting a load handling specification for the object based on the type of the object;

accessing a second timeseries of motion values output by the motion sensor, coupled to the crane hook, during a second time period succeeding the first time period; and

in response to the second timeseries of motion values deviating from the load handling specification, generating a second object motion alarm for the object during the second time period.

20. The method of claim 19 , further comprising:

interpreting a pendulum amplitude of the object during the second time period based on the second timeseries of motion values; and

adjusting the buffer distance proportional to the pendulum amplitude of the object during the second time period.