Orientation sensor

Abstract

The device is a miniature, self-contained solid state orientation sensor. The unit utilizes three magnetometers and three accelerometers to calculate pitch, roll, and yaw (compass heading) angles relative to the earth's magnetic and gravitational fields. The three orientation angles are output in digital RS232 or optional multi-drop RS485. The device can also be programmed to provide raw accelerometer and magnetometer data in true physical units. The device is capable of measuring angles from 0 to 360 degrees on the yaw axis, 0 to 360 degrees on the pitch axis, and −70 to +70 degrees on the roll axis. The yaw output is compensated for errors due to pitch and roll using embedded algorithms. Applications include fast solid state compassing, robotics, virtual reality, down-hole well drilling, and body position tracking for biomedical and multimedia applications.

We claim:  
     
         1 ) A solid state orientation sensor with 360 degree measurement capability, for use in a number of different structural and medical applications, comprising: 
 primary means comprising a plurality of magnetic field measurement sensors;    secondary means comprising a plurality of response accelerometers; and    a microprocessor having first means for scaling sensors with calibration coefficients, and further having second means for quadrant checking for calculating the absolute angle from accelerometers.    
     
     
         2 . A solid state orientation sensor with 360 degree measurement capability, according to  claim 1 , wherein: 
 said plurality of magnetic field sensors comprises using at least three magnetic sensors.    
     
     
         3 . A solid state orientation sensor with 360 degree measurement capability, according to  claim 1 , wherein: 
 said plurality of magnetic field sensors having analog filtering means on the output of said magnetic field sensors.    
     
     
         4 . A solid state orientation sensor with 360 degree measurement capability, according to  claim 1 , wherein: 
 said plurality of magnetic field sensors further having digital filtering means on the output of said magnetic field sensors.    
     
     
         5 . A solid state orientation sensor with 360 degree measurement capability, according to  claim 1 , wherein: 
 said sensors having amplification means on the output of said sensors.    
     
     
         6 . A solid state orientation sensor with 360 degree measurement capability, according to  claim 1 , wherein: 
 said plurality of response accelerometers having two digital low pass filters with different cutoff frequencies for being applied to the outputs of each sensor.    
     
     
         7 . A solid state orientation sensor with 360 degree measurement capability, according to  claim 6 , wherein: 
 said microprocessor comprises means for monitoring the output of both filters and determines which filter to apply to the calculation based on the first derivative of the output of said magnetic field measurement sensors.    
     
     
         8 . A solid state orientation sensor with 360 degree measurement capability, according to  claim 1 , wherein: 
 said plurality of response accelerometers comprise using at least three of said response accelerometers.    
     
     
         9 . A solid state orientation sensor with 360 degree measurement capability, according to  claim 1 , wherein: 
 said primary means and said secondary means having networking means for allowing for said first means and said second means for use on a two wire bus.    
     
     
         10 . A solid state orientation sensor with 360 degree measurement capability, according to  claim 1 , wherein: 
 said microprocessor further comprises means for monitoring the orientation of said device and direct which sensors are used in the calculations based upon the orientation as determined by said accelerometers.