Motion sensing system
A motion sensing system includes a hand-held device and a receiver device. The hand-held device includes a microcontroller, a G-sensor (one 3-axis accelerometer), only one 2-axis gyroscope, and a wireless transmitter. The receiver device is preferably a dongle and includes a microcontroller and a wireless receiver. A first axis of the 2-axis gyroscope is parallel to the Z axis of the hand-held device and the second axis of the 2-axis gyroscope forms an acute angle α with the X axis of the hand-held device. The acute angle α allows the microcontroller of the receiver device to calculate rotational data around each of the three axis of the hand-held device.
1. A motion sensing system comprising;
a motion sensing device having three perpendicular axes, a pointing direction along a first axis of the three perpendicular axes, and only two rotational sensors arranged to form a non-zero acute angle between a second axis of the three perpendicular axes and an axis of a first of the rotational sensors, a 3-axis accelerometer having the axes aligned with the three perpendicular axes, and a first microprocessor coupled to receive output from the 3-axis accelerometer and output from the two rotational sensors; and
a receiver device, the receiver device comprising a wireless receiver and a second microprocessor, wherein the second microprocessor generating rotational data around 3 axes of the motion sensing device according to the non-zero acute angle, the second microprocessor calculating 3-axis angular speeds of the motion sensing device according to
Z _rotation= Wz ×cos θ+( Wxy /sinα)×sinθ
X _rotation=− Wz ×sin θ+( Wxy /sinα)×cosθ
Y _rotation= Wxy /sin(90°−α)
where “W” is the angular speed, “α” is the acute angle, and “θ” is the tilt angle θ.
2. The motion sensing system of claim 1 wherein the motion sensing device further comprises a transmitter coupled to receive output of the first microprocessor.
3. The motion sensing system of claim 2 wherein the wireless receiver is coupled to output to a second microprocessor.
4. The motion sensing system of claim 3 wherein the receiver device is a Universal Serial Bus dongle.
5. The motion sensing system of claim 3 wherein the transmitter is a wireless transmitter.
6. The motion sensing system of claim 1 wherein an axis of a second of the rotational sensors is substantially parallel with a third axis of the three perpendicular axes.
7. A method for operating a motion sensing system, the motion sensing system comprising a hand-held device and a receiver device, the band-held device including a wireless transmitter, a first microprocessor, a 3-axis accelerometer, and only two rotational sensors, an axis of a first of the two rotational sensors forming an acute angle with at least one axis of the 3-axis accelerometer, the receiver device comprising a wireless receiver and a second microprocessor, the method comprising:
the first microprocessor receiving sensed acceleration data from the 3-axis accelerometer and rotational data from the two rotational sensors and outputting the received data to the wireless transmitter;
the wireless transmitter transmitting the received data to the wireless receiver;
the wireless receiver transmitting the received data to the second microprocessor; and
the second microprocessor generating rotational data around 3 axes of the hand-held device according to the acute angle, and calculating 3-axis angular speeds of the hand-held device according to
Z _rotation= Wz ×cosθ+( Wxy /sinα)×sinθ
X _rotation= Wz ×sinθ+( Wxy /sinα)×cosθ
Y _rotation= Wxy /sin(90°−α)
where “W” is the angular speed, “α” is the acute angle, and “θ” is the tilt angle θ.
8. The method of claim 7 further comprising the second microprocessor calculating a tilt angle θ of the hand-held device.
9. The method of claim 8 further comprising calculating the tilt angle θ according to
A·B=|A|×|B |×cos θ
cos θ= A·B /( |A|×|B |)
where “A” is the sensed acceleration data and “B” is a unit vector of a normal vector to a ground plane.
10. The method of claim 7 further comprising outputting game control signals based on the 3-axis angular speeds.