Activity Recognition Using Accelerometer Data

Abstract

A device for recognizing activity of an object. The device comprises a housing configured to be attached to the object and a processing unit disposed in the housing comprising a processor and a movement sensor. The movement sensor measures a signal related to movement of the object during a time window. The processor assigns at least one preliminary activity label to the time window based on at least one numerical descriptor computed from the signal. The processor then determines whether to perform additional analysis dependent upon at least the preliminary activity label. The processor then assigns a final activity label to the time window.

What is claimed is: 
     
         1 . A device for recognizing activity of an object, the device comprising:
 a housing configured to be attached to the object;   a processing unit disposed in the housing comprising a processor, a location module, and a movement sensor;   wherein the movement sensor measures a signal related to movement of the object during a time window and the location module provides location information related to the location of the processing unit during the time window;   wherein the processor assigns at least one preliminary activity label to the time window based on at least one numerical descriptor computed from the measured signal and the location information;   wherein the processor determines whether to perform additional analysis dependent upon at least the preliminary activity label; and   and wherein the processor assigns a final activity label to the time window.   
     
     
         2 . The device of  claim 1 , wherein if the processor does not perform additional analysis, the final activity label is the same as the preliminary activity label. 
     
     
         3 . The device of  claim 1 , wherein the processor assigns the final activity label to the time window based on the preliminary activity label for the time window and at least one final activity label for at least one prior time window. 
     
     
         4 . The device of  claim 1 , wherein the movement sensor is at least one of: an accelerometer, gyroscope, piezoelectric vibration sensor, geographical positioning sensor and a magnetic switch. 
     
     
         5 . The device of  claim 1 , further comprising an emergency notification component. 
     
     
         6 . The device of  claim 1 , wherein the device is an electronic monitoring bracelet. 
     
     
         7 . The device of  claim 1 , wherein the movement sensor collects data at a rate in the range of 1 (one) Hz to 20 (twenty) Hz. 
     
     
         8 . The device of  claim 1 , wherein the length of the time window is in the range of 2 (two) seconds to 10 (ten) seconds and contains a number of samples in the range of 8 to 1024 samples. 
     
     
         9 . The device of  claim 1 , wherein at least two numerical descriptors are computed from the signal. 
     
     
         10 . The device of  claim 2 , wherein the device transmits an alarm signal to a central monitoring system upon determination of a particular final activity label. 
     
     
         11 . The device of  claim 1 , wherein the processor uses a decision tree algorithm to assign the preliminary activity label to the time window. 
     
     
         12 . The device of  claim 1 , wherein the possible activity labels include at least one of: walking, driving, sleeping, sitting, running, eating, and bicycling. 
     
     
         13 . The device of  claim 1 , wherein the performing of additional analysis is also dependent on a device state. 
     
     
         14 . The device of  claim 1 , wherein the additional analysis includes computational escalation including at least one of the following algorithm techniques: neural networks, Bayesian analysis, random forest, support vector machine, and multi-level decision tree. 
     
     
         15 . The device of  claim 1 , wherein the processor determines to perform additional analysis when the preliminary activity label is a commonly confused preliminary activity. 
     
     
         16 . A device for recognizing activity of an object, the device comprising:
 a housing configured to be attached to the object;   a processing unit disposed in the housing comprising a processor, a location module, and a movement sensor;   wherein the movement sensor measures a signal related to movement of the object during a time window and the location module provides location information related to the location of the processing window during the time window;   wherein the processor assigns at least one preliminary activity label and confidence indicator to the time window based on at least one numerical descriptor computed from the measured signal and the location information;   wherein the processor determines whether to perform additional analysis dependent upon at least the confidence indicator; and   wherein the processor assigns a final activity label to the time window.   
     
     
         17 . The device of  claim 16 , wherein if the processor does not perform additional analysis, the final activity label is the same as the preliminary activity label. 
     
     
         18 . The device of  claim 16 , wherein the processor assigns a final activity label to the time window based on the preliminary activity label for the time window and at least one final activity label for at least one prior time window. 
     
     
         19 . The method of  claim 16 , wherein if the confidence indicator is below a predefined threshold, the processor performs additional analysis. 
     
     
         20 . The method of  claim 16 , wherein the processor assigns more than one preliminary activity label with, each preliminary activity label having a confidence indicator within a predefined margin of each other, the processor performs additional analysis.