Abstract:
A miniaturized, ruggedized, field-deployable Portable Exposure Assessment System (PEAS) is used to remotely monitor workers and provide real-time warning of exposure to musculoskeletal injury conditions via alarm and smart-phone transmission. The PEAS unit wirelessly acquires exposure data from sensors; conducts initial data analysis; triggers proximal and remote alarms; sends out text messages with abnormal data, GPS locations, and time stamps to a safety office; and saves data for more extensive assessment. Sensor technology is used in this field-deployable system to simultaneously measure and collect the body loads and awkward postures imposed by package handling as well as driving-related, low-frequency vibration exposures. Wireless technology is used to set up wireless communication links between the sensors and a data logger and between the data logger and a smart phone with GPS, date/time stamp and text messaging capabilities.

Description:
REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. Provisional Patent Application Ser. No. 61/599,525, filed Feb. 16, 2012, the entire content of which is incorporated herein by reference. 
    
    
     GOVERNMENT INTEREST 
     The invention described herein may be manufactured, used, and licensed by or for the United States Government. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to systems for measuring worker safety and, in particular, to a portable, field-based, remotely deployed system and method to monitor and provide early warning of exposure to conditions that might lead to musculoskeletal injury. 
     BACKGROUND OF THE INVENTION 
     Any worker who lifts and carries objects—such as packages for delivery, construction materials, manufactured goods, or patients—is at risk of musculoskeletal injury. Various methodologies exist that analyze lifting tasks to quantify musculoskeletal risks, such as the National Institute for Occupational Safety and Health (NIOSH) method. One system for applying the NIOSH equation is described in U.S. Pat. No. 5,621,667. This patent describes an instrumented analysis system based on a retractable cable and potentiometer system which can determine the NIOSH equation multipliers indicative of physical parameters related to a lifting task under analysis. However, the system is difficult to implement in a normal working environment since it requires a dedicated space to set up the instrumentation and experienced personnel to operate the system. As such, the system of the &#39;667 Patent is more suited to a laboratory environment than a regular work environment. 
     Published U.S. Patent Application No. 2007/0250286 describes a motion analysis system that can be used to alert a worker that their current motion is not optimal, upon detection of a specified criterion being exceeded during a performed task. Such a criterion can be calculated by applying common work place safety assessment tools, such as the NIOSH equation, or other similar measures previously mentioned using the collected data. Sensor elements attached to movable body segments record movement parameters including angular velocity and acceleration. A control device receives the movement parameters and determines an overall motion of the movable body segments. The overall motion is analyzed against an acceptable motion model to determine whether the overall motion is within acceptable limits. The sensor elements and control device are lightweight and can be worn during normal movement activities, thereby allowing monitoring of work-based activities, such as lifting or typing. 
     While it is claimed that the system described in the &#39;286 Application can be used in a number of applications previously relegated to laboratory spaces and dedicated laboratory equipment, the system and method have various shortcomings. As one example, the alarm system is limited and could benefit from other modalities, including wireless transmissions. Further, a more appropriate application of gyroscopes and accelerometers could be deployed to measure body vibrations, spine angle, body posture sway and instability. 
     U.S. Pat. No. 8,149,126 relates to a system for monitoring the behavior of a subject to detect an incidence of unsafe lifting strategy use or high-risk movement. The system includes a wearable trunk sensor, a wearable thigh sensor, and a portable computing device. The computing device may receive the data from the trunk sensor and/or the thigh sensor via a wireless transceiver. Based on the received data, the computing device determines trunk angle and a thigh angles using a combination of accelerometer and gyroscope data received from the trunk and thigh sensors. Trunk rotation is determined by comparing rotation data obtained from the trunk sensor with data obtained from the thigh sensor. The trunk angle, thigh angle, and/or trunk rotation values are used to calculate a risk level associated with the subject&#39;s movement. The system may include additional sensors, such as a weight sensor, to determine the weight of an object being lifted, for example for inclusion in the risk level assessment algorithm. The weight sensors may be shoe borne pressure sensors or pressure sensors mounted into surfaces upon which the subject stands, e.g., a floor, ramp, platform, or truck bed. While the system described in the &#39;126 patent may be useful in some circumstances, the assessments do not take into account hand or arm movements, vibration, or other more sophisticated modalities or computations. 
     SUMMARY OF THE INVENTION 
     This invention resides in a portable, field-based, remotely deployed tool to monitor and provide early warning of the exposure of workers to conditions that have a high likelihood of musculoskeletal injury, specifically through the lifting or carrying of items that are too heavy or bulky given the environmental conditions or the body of the worker. Such conditions are known to be associated with high incidence of subsequent slip, trip, and fall injuries, both as a result of injury to the soft tissues of the body and as a result of direct exposure to excess loads. Further injury conditions monitored by the system include those generated by continued exposure to low-level vibrations, as experienced by truck drivers and machinery operators. 
     The systems, called the Portable Exposure Assessment System (PEAS) is used to remotely monitor workers to instantaneously determine and provide warning of exposure to these injury conditions. The apparatus provides real time notification via alarm and smart-phone transmission, of injury-risk conditions that are likely to lead to musculoskeletal injury, as well as exposure to slip-, trip-, and fall-related traumatic injury. The device is miniaturized, ruggedized, and field deployable, such that it can be worn at worksites without interfering with workers&#39; regular tasks. The portable unit, including a data logger, is approximately the size of a cellular telephone and will use comparable technology. Both the worker and any monitoring station can be notified by the alarm. 
     The PEAS unit acquires exposure data from sensors; conducts initial data analysis; triggers proximal and remote alarms; sends out text messages with abnormal data to a safety officer, GPS locations, and time stamps; and saves data for more extensive assessment. Sensor technology is used in this field-deployable system to simultaneously measure and collect the body loads and awkward postures imposed by package handling as well as driving-related, low-frequency vibration exposures. Wireless technology will be used to set up wireless communication links between the sensors and a data logger and between the data logger and a smart phone with GPS and text messaging capabilities. 
     The smart phone may be programmed to (1) wirelessly receive commands from the data logger to dial a number and send a text message containing the exposure data that exceed the safety thresholds, the GPS location, the date/time stamps, and the corresponding safety message; and (2) wirelessly receive and store data transmitted from the data logger and transfer these data and the corresponding GPS locations and time stamps to a computer, via a proper computer interface, for further data analysis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a system block diagram of a preferred embodiment of the invention; 
         FIG. 2  is a first block diagram of a gyroscope hand position sensor; 
         FIG. 3  is a second block diagram of a gyroscope hand position sensor; 
         FIG. 4  is a third block diagram of a gyroscope hand position sensor; 
         FIG. 5  is a first block diagram of a gyroscope torso angular sensor; 
         FIG. 6  is a second block diagram of a gyroscope torso angular sensor; 
         FIG. 7  is a block diagram of an accelerometer torso vibration sensor; 
         FIG. 8  is a first block diagram of a foot force sensor; and 
         FIG. 9  is a second block diagram of a foot force sensor. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIG. 1 , the PEAS comprises (1) gyroscope position sensors on the upper and lower arms to measure the worker&#39;s hand (wrist) positions; (2) gyroscope angular sensor on the worker&#39;s torso to measure torso angle; (3) an accelerometer-based torso vibration sensor to measure the vibration experienced by the worker while operating a truck; (4) foot force sensors to measure the load distribution experienced by the worker while carrying packages; (5) a data logger to collect all measured data, conduct necessary real time data processing by comparing the data to predefined safety thresholds stored in memory, save and transfer the data and results of the analysis, and communicate with a smart phone; and (6) a smart phone to (a) wirelessly receive commands from the data logger and send out text messages with abnormal exposure data to a safety officer, GPS location, and date/time information and (b) wirelessly receive the data transmitted from the data logger, store these data with correspondent GPS locations and date/time stamps, and transfer these data. GPS locations and date/time stamps to a computer via a proper computer interface, such as a USB interface. 
     Referring now to  FIG. 2 , the hand (wrist) position sensor is composed of two triaxial gyroscopes (G 1  and G 2 ) to measure the angular velocities of the upper arm and lower arm, two microcontrollers to calculate the elbow position relative to the shoulder joint and the wrist position relative the elbow joint, and two radio frequency (RF) transceivers to transmit the elbow and wrist position data to the data logger and receive commands from the logger. The data logger receives these position data and calculates the wrist position relative to the shoulder joint. Two sets of hand position sensors are mounted on the worker&#39;s left and right arms to measure the positions of the left and right wrists. 
     To measure the wrist positions relative to the shoulder joint, G 1  is mounted near the elbow of the upper arm and G 2  is mounted near the wrist of the lower arm. First, G 1  measures the elbow&#39;s pitch, yaw and roll angular velocities. The microcontroller connected with G 1 &#39;s output in the sensor calculates the elbow&#39;s pitch, yaw and roll angles by computing the integral of G 1 &#39;s pitch, yaw and roll angular velocities ( FIG. 3 ). The microcontroller consecutively converts the pitch, yaw and roll angles into the spherical elevation and azimuth angles, and calculates the elbow position relative to the shoulder joint using Equations 1, 2, and 3:
 
x1=r1 sin α1 cos β1   (1)
 
y1=r1 sin α1 sin β1   (2)
 
z1=r1 cos α1   (3)
 
where x 1 , y 1 , and z 1  are the position coordinates of the elbow relative to the shoulder joint; r 1  is the length of the upper arm; α 1  and β 1  are elevation and azimuth angles of G 1  ( FIG. 4 ).
 
     Similar to the calculations in G 1 , the microcontroller connected with G 2 &#39;s output calculates the wrist position relative to the elbow joint using Equations 4, 5, and 6:
 
x2=r2 sin α2 cos β2   (4)
 
y2=r2 sin α2 sin β2   (5)
 
z2=r2 cos α2   (6)
 
where x 2 , y 2 , and z 2  are the position coordinates of the wrist relative to the elbow joint; r 2  is the length of the lower arm; α 2  and β 2  are elevation and azimuth angles of G 2  ( FIG. 4 ).
 
     The data logger&#39;s RF transceiver receives the x 1 , y 1  and z 1  position coordinates from G 1 &#39;s RF transceiver and receives the x 2 , y 2  and z 2  position coordinates from G 2 &#39;s RF transceiver and the data logger&#39;s microcontroller calculates the wrist position relative to the shoulder joint using Equations 7, 8, and 9:
 
 x=x 1 +x 2   (7)
 
 y=y 1+ y 2   (8)
 
 z=z 1 +z 2   (9)
 
where x, y, and z are the position coordinates of the wrist relative to the shoulder joint ( FIG. 4 ).
 
     The gyroscope torso angular sensor ( FIG. 5 ) is composed of two triaxial gyroscopes (G 3  and G 4 ) to measure the angular velocities of the vertebras L 1  and S 1 , two microcontrollers to calculate the angles of L 1  and S 1 , and two RF transceivers to transmit L 1  and S 1  angle data to the data logger and receive commands from the logger. 
     To measure the pitch, yaw and roll angular velocities of the torso, G 3  is mounted on vertebra L 1  and G 4  is mounted on vertebra S 1 . After G 3  measures the pitch, yaw and roll angular velocities of vertebra L 1 , the microcontroller connected with G 3 &#39;s output in the sensor calculates the pitch, yaw and roll angles of L 1  by computing the integral of the pitch, yaw and roll angular velocities. The pitch, yaw and roll angles of vertebra S 1  are measured and calculated in the same method. The data logger transceiver receives the L 1  and S 1  pitch, yaw and roll angles from L 1  and S 1  transceivers, and calculates the torso pitch, yaw and roll angles. The torso pitch angle is the difference of the L 1  and S 1  pitch angles, the torso yaw angle is the difference of the L 1  and S 1  yaw angles, and the torso roll angle is the difference of the L 1  and S 1  roll angles ( FIG. 6 ). 
     The torso vibration sensor ( FIG. 7 ) captures the acceleration data on the lower back of the worker while operating a truck. The vibration sensor is composed of an accelerometer (sensitivity range &lt;2 g), a microcontroller, and an RF transceiver. The sensor is positioned at the worker&#39;s vertebra S 1 . The accelerometer measures the low-frequency acceleration of the lower back in real time. The microcontroller calculates the root-mean-square (RMS) values of the acceleration in a short RMS period (such as 1 second) and transmits the RMS acceleration data to the data logger at the end of every RMS period. 
     The foot force sensors ( FIG. 8 ) capture foot force experienced by the worker while carrying packages. The foot force sensors consist of two identical subsensor groups for the force sensing on the left and right feet. Each subsensor group is composed of three strain gauge force transducers, a microcontroller, and an RF transceiver. The force sensors are mounted on the insoles of the worker&#39;s shoes as shown in  FIG. 9 . The force sensors measure the worker&#39;s foot force distribution on the shoe soles in real time. The microcontroller samples the foot force distribution data and transmits the data to the data logger via the RF transceiver. 
     The data logger acts as the controller of the PEAS system. It can be placed anywhere around the worker. It is composed of a microcontroller, a flash memory integrated circuit (IC), an RF transceiver, and a Bluetooth wireless module, which is wirelessly linked to a smart phone. The data logger wirelessly communicates with the hand position sensors, the torso angular sensor, the torso vibration sensor, and the foot force sensors via its RF transceiver. The data logger receives the data transmitted from the sensors, saves the data on its flash memory IC, processes the data, and compares the processed data with the predefined safety thresholds to determine excessive exposures in real time. The data logger wirelessly communicates with the smart phone via its Bluetooth wireless module. 
     The processed data are stored on the data logger&#39;s flash memory IC. These data can be transmitted to the smart phone via the Bluetooth module, and transferred to a computer via computer interface. The smart phone stores the processed data with the corresponding GPS locations and time stamps. After the field data collection is complete, the smart phone transfers the whole set of stored data to a computer via a computer interface, such as a USB interface, for further data analysis. The data logger can wirelessly control the smart phone to dial a number and send an emergency message to safety officer via an alarm mechanism. 
     The alarm mechanism may include an audible/visual alarm group inside the data logger, and the text messaging, GPS and time stamp functions of the smart phone. If one or more real time exposure data exceed the predefined safety threshold(s), the data logger sets off its audible and/or visual alarms. In the meantime, the data logger activates the smart phone via its Bluetooth module to dial an emergency number and send out a text message containing a prerecorded safety message to a safety officer, along with abnormal data, corresponding GPS locations, and time stamps. 
     The anticipated use of the PEAS system will be in the monitoring of industrial tasks that currently are associated with high rates of personal injury and workers&#39; compensation payments from worker exposure to occupational conditions associated with repeated or continual lifting of heavy packages, tools, building materials, and manufacturing items. Targeted industrial sectors include construction, package delivery, manufacturing, healthcare, and trucking. Sources of injury include falls to the same level, lifting-induced musculoskeletal disorders, and vibration-induced injury. It is anticipated that end users will be safety officers within the environmental, safety, and health departments of large corporations with high workers&#39; compensation premiums and employees with responsibility for safety and health within smaller corporations.