Hand held pointing device with roll compensation

Abstract

A pointing device includes accelerometers and rotational sensors that are coupled to a processor. The processor samples the accelerometers and rotational sensors to detect gravity and pointing device motion and uses algebraic algorithms to calculate roll compensated cursor control signals. The processor transmits the cursor control signals to a receiver that is coupled to an electronic device that moves the cursor on the visual display.

What is claimed is: 
     
         1 . A pointing system for controlling movement of a cursor on an electronic display comprising:
 a first rotational sensor providing a first rotational velocity signal R X  for rotational movement about a first axis;   a second rotational sensor providing a second rotational velocity signal R Z  for rotational movement about a second axis;   a first accelerometer providing a first acceleration signal A X  in response to a acceleration in a first direction along the first axis;   a second accelerometer providing a second acceleration signal A Z  in response to a acceleration in a second direction along the second axis; and   a processing unit that calculates roll-compensated cursor movement signals X comp  and Y comp  from R X , R Z , A X  and A Z , wherein the processing unit does not use any trigonometric computation in the calculating steps.   
     
     
         2 . The pointing device of  claim 1  further comprising:
 a receiver associated with the electronic display; and 
 a transmitter for transmitting signals to the receiver. 
 
     
     
         3 . The pointing system of  claim 1  further comprising:
 a sampling system for receiving a plurality of reading for each of R X , R Z , A X  and A Z  and processing the plurality of reading for each of R X , R Z , A X  and A Z  before the processing unit receives R X , R Z , A X  and A Z  from the sampling system. 
 
     
     
         4 . The pointing system of  claim 1  further comprising:
 a sampling system for receiving a plurality of reading for each of R X , R Z , A X  and A Z  and discarding some of the plurality of reading for each of R X , R Z , A X  and A Z  before the processing unit receives R X , R Z , A X  and A Z  from the sampling system. 
 
     
     
         5 . The pointing system of  claim 1  further comprising:
 a sampling system for receiving a plurality of reading for each of R X , R Z , A X  and A Z  and discarding suspect readings from the plurality of reading for each of R X , R Z , A X  and A Z  that are a highest reading or a lowest reading from the plurality of reading for each of R X , R Z , A X  and A Z  before the processing unit receives R X , R Z , A X  and A Z  from the sampling system. 
 
     
     
         6 . The pointing system of  claim 1  further comprising:
 a sampling system for receiving a plurality of reading for each of R X , R Z , A X  and A Z  and calculates averages readings from the plurality of reading for each of R X , R Z , A X  and A Z  before the processing unit receives the averages of R X , R Z , A X  and A Z  from the sampling system. 
 
     
     
         7 . The pointing system of  claim 1  wherein the sampling system receives a plurality of reading for each of R X , R Z , A X  and A Z , and the sampling system discards some of the plurality of reading for each of R X , R Z , A X  and A Z . 
     
     
         8 . The pointing system of  claim 1  further comprising:
 a memory coupled to the processing unit for storing correction offsets for the first rotational sensor and the second rotational sensor. 
 
     
     
         9 . The pointing system of  claim 8  wherein the correction offsets for the first rotational sensor and the second rotational sensor are calculated from error signals from the first rotational sensor and the second rotational sensor that are detected when the first accelerometer signal A X  from the first accelerometer and the second acceleration signal A Z  from the second accelerometer are steady output signals. 
     
     
         10 . The pointing system of  claim 1 , wherein the processing unit is a 16 bit reduced instruction set computer processor (RISC). 
     
     
         11 . The pointing system of  claim 1 , wherein the processing unit operates at a frequency of 4 MHz or less. 
     
     
         12 . The pointing system of  claim 1 , further comprising:
 a pair of 1.5 volt AA or AAA size battery for providing electrical power to the processing unit.   
     
     
         13 . The pointing system of  claim 1 , wherein the first acceleration signal A X  is corrected for rotational acceleration of the first accelerometer about the second axis by the equation: A Xcorrected =A X −ΔR Z /Δtime*l X  and the second acceleration signal A Z  is corrected for rotational acceleration of the second accelerometer about the first axis by the equation:
     A   Zcorrected   =A   Z   −ΔR   X /Δtime* l   Z  and
 
 
       wherein ΔR X /Δtime is a rotational acceleration about the first axis, ΔR Z /Δtime is a rotational acceleration about the second axis, l X  is a perpendicular length between a line through the first accelerometer in the first direction and the second axis and l Z  is a perpendicular length between a line through the second accelerometer in the second direction and the first axis. 
     
     
         14 . The pointing system of  claim 1 , wherein the processing unit calculates a vector sum A XZ  of A X  and A Z  and roll-compensated cursor movement signals X comp  and Y comp  with the equations:)
     X   comp   =[A   X   *R   X   +A   Z   *R   Z   ]/A   XZ ; and       Y   comp   =[A   X   *R   Z   −A   Z   *R   X   ]/A   XZ .   
     
     
         15 . A pointing system for controlling movement of a cursor on an electronic display comprising:
 a first rotational sensor providing a first rotational velocity signal R X  for rotational movement about a first axis;   a second rotational sensor providing a second rotational velocity signal R Z  for rotational movement about a second axis;   a first accelerometer providing a first acceleration signal A X  in response to a acceleration in a first direction along the first axis;   a second accelerometer providing a second acceleration signal A Z  in response to a acceleration in a second direction along the second axis;   a third accelerometer providing a third acceleration signal A Y  in response to a acceleration in a third direction along a third axis, and a processing unit that calculates pitch-and-roll-compensated cursor movement signals X comp  and Y comp  from R X , R Z , A X , A Y , and A Z , wherein the processing unit does not use any trigonometric computation in the calculating steps.   
     
     
         16 . The pointing system of  claim 15  further comprising:
 a receiver associated with the electronic display; and 
 a transmitter for transmitting signals to the receiver. 
 
     
     
         17 . The pointing system of  claim 15  further comprising:
 a sampling system for receiving a plurality of reading for each of R X , R Z , A X , A Y  and A Z  and processing the plurality of reading for each of R X , R Z , A X , A Y  and A Z  before the processing unit receives R X , R Z , A X , A Y  and A Z  from the sampling system. 
 
     
     
         18 . The pointing system of  claim 15  further comprising:
 a sampling system for receiving a plurality of reading for each of R X , R Z , A X , A Y  and A Z  and discarding some of the plurality of reading for each of R X , R Z , A X , A Y  and A Z  before the processing unit receives R X , R Z , A X , A Y  and A Z  from the sampling system. 
 
     
     
         19 . The pointing system of  claim 15  further comprising:
 a sampling system for receiving a plurality of reading for each of R X , R Z , A X , A Y  and A Z  and discarding suspect readings from the plurality of reading for each of R X , R Z , A X , A Y  and A Z  that are a highest reading or a lowest reading from the plurality of reading for each of R X , R Z , A X , A Y  and A Z  before the processing unit receives R X , R Z , A X , A Y  and A Z  from the sampling system. 
 
     
     
         20 . The pointing system of  claim 15  further comprising:
 a sampling system for receiving a plurality of reading for each of R X , R Z , A X , A Y  and A Z  and calculates averages readings from the plurality of reading for each of R X , R Z , A X , A Y  and A Z  before the processing unit receives the averages of R X , R Z , A X , A Y  and A Z  from the sampling system. 
 
     
     
         21 . The pointing system of  claim 15  wherein the sampling system receives a plurality of reading for each of R X , R Z , A X , A Y  and A Z , and the sampling system discards some of the plurality of reading for each of R X , R Z , A X , A Y  and A Z . 
     
     
         22 . The pointing system of  claim 15  further comprising:
 a memory coupled to the processing unit for storing correction offsets for the first rotational sensor and the second rotational sensor. 
 
     
     
         23 . The pointing system of  claim 22  wherein the correction offsets are calculated from error signals from the first rotational sensor and the second rotational sensor that are detected when the first accelerometer signal A X  from the first accelerometer, the second acceleration signal A Z  from the second accelerometer and the third acceleration signal A Y  from the third accelerometer are steady output signals. 
     
     
         24 . The pointing system of  claim 15 , wherein the processing unit is a 16 bit reduced instruction set computer processor (RISC). 
     
     
         25 . The pointing system of  claim 15 , wherein the processing unit operates at a frequency of 4 MHz or less. 
     
     
         26 . The pointing system of  claim 15 , further comprising:
 a pair of 1.5 volt AA or AAA size battery for providing electrical power to the processing unit.   
     
     
         27 . The pointing system of  claim 15 , wherein the first acceleration signal A X  is corrected for rotational acceleration of the first accelerometer about the second axis by the equation: A Xcorrected =A X −ΔR Z /Δtime*l X  and the second acceleration signal A Z  is corrected for rotational acceleration of the second accelerometer about the first axis by the equation:
     A   Zcorrected   =A   Z   −ΔR   X /Δtime* l   Z  and
 
 
       wherein ΔR X /Δtime is a rotational acceleration about the first axis, ΔR Z /Δtime is a rotational acceleration about the second axis, l X  is a perpendicular length between a line through the first accelerometer in the first direction and the second axis and l Z  is a perpendicular length between a line through the second accelerometer in the second direction and the first axis. 
     
     
         28 . The pointing system of  claim 15 , wherein the processing unit calculates a vector sum A XZ  of A X  and A Z , a vector sum A XYZ  of A X , A Y  and A Z , and roll-compensated cursor movement signals with the equations:
     X   comp   =[A   X   *R   X   +A   Z   *R   Z   ]/A   XZ   *A   XYZ   /A   XZ ; and       Y   comp   =[A   X   *R   Z   −A   Z   *R   X   ]/A   XZ .   
     
     
         29 . A pointing system for controlling movement of a cursor on an electronic display comprising:
 a processing unit containing executable instructions for: (a) receiving a first rotational velocity signal R X , a second rotational velocity signal R Z , a first acceleration signal A X  in response to an acceleration in a first direction along the first axis and a second acceleration signal A Z  in response to an acceleration in a second direction along the second axis, and (b) calculating roll-compensation cursor movement signals X comp  and Y comp  using roll-compensation algorithms that do not include trigonometry functions and using signals R X , R Z , A X , and A Z  and the vector sum A XZ  as inputs to the roll-compensation algorithms.   
     
     
         30 . The pointing system of  claim 29 , further comprising:
 a receiver associated with the electronic display; and   a transmitter for transmitting signals to the receiver.   
     
     
         31 . The pointing system of  claim 29 , wherein the processing unit is a 16 bit reduced instruction set computer processor (RISC). 
     
     
         32 . The pointing system of  claim 29 , wherein the processing unit operates at a frequency of 4 MHz or less. 
     
     
         33 . The pointing system of  claim 29 , further comprising:
 a pair of 1.5 volt AA or AAA size battery for providing electrical power to the processing unit.   
     
     
         34 . The pointing system of  claim 29 , wherein the first acceleration signal A X  is corrected for rotational acceleration of the first accelerometer about the second axis by the equation: A Xcorrected =A X −ΔR Z /Δtime*l X  and the second acceleration signal A Z  is corrected for rotational acceleration of the second accelerometer about the first axis by the equation:
     A   Zcorrected   =A   Z   −ΔR   X /Δtime* l   Z  and
 
 
       wherein ΔR X /Δtime is a rotational acceleration about the first axis, ΔR Z /Δtime is a rotational acceleration about the second axis, l X  is a perpendicular length between a line through the first accelerometer in the first direction and the second axis and l Z  is a perpendicular length between a line through the second accelerometer in the second direction and the first axis. 
     
     
         35 . The pointing system of  claim 29 , wherein the processing unit calculates a vector sum A XZ  of A X  and A Z  and roll-compensated cursor movement signals X comp  and Y comp  with the equations:
     X   comp   =[A   X   *R   X   +A   Z   *R   Z   ]/A   XZ ; and       Y   comp   =[A   X   *R   Z   −A   Z   *R   X   ]/A   XZ.