Writing system
A Micro Inertial Measurement Unit (IMU) which is based on MEMS accelerometers and gyro sensors is developed for real-time recognition of human hand motions, especially as used in the context of writing on a surface. Motion is recorded by a rate gyro and an accellerometer and communicated to a Bluetooth module, possibly to a computer which may be 20 to 30 feet or more from the sensor. The motion information generated and communicated is combined with appropriate filtering and transformation algorithms to facilitate a complete Digital Writing System that can be used to record handwriting on any surface, or on no surface at all. The overall size of an IMU can be less than 26 mm×20 mm×20 mm, and may include micro sensors, a processor, and wireless interface components. The Kalman filtering algorithm is preferably used to filter the noise of sensors to allow successful transformance of hand motions into recognizable and recordable English characters. The immediate advantage is the facilitation of a digital interface with both PC and mobile computing devices and perhaps to enable wireless sensing.
1. A writing system comprising:
a housing;
a three dimensional accelerometer, supported by said housing, for of detecting acceleration of the accelerometer in any direction, and having an accelerometer output;
a three dimensional rate gyroscope, supported by said housing, for detecting angular position orientation changes along all planes, and having a gyroscope output;
a microcontroller having an input connected to said accelerometer output and said gyroscope output and configured to convert said accelerometer output and said gyroscope output into a two dimensional line path as a representation of a path of said housing during writing, and
a surface detect sensor, supported by said housing and connected to said input for indicating a start and a finish of said two dimensional line path as a beginning and ending of writing.
2. The writing system as recited in claim 1 wherein said microcontroller includes an input for indicating a start and a finish of said two dimensional line path as a beginning and ending of writing.
3. The writing system as recited in claim 2 and further comprising a switch connected to said input for indicating a start and a finish of said two dimensional line path as a beginning and ending of writing.
4. The writing system as recited in claim 1 and further comprising transmitter supported by said housing for transmitting a representation of said two dimensional line path to a location remote with respect to said housing.
5. The writing system as recited in claim 4 wherein said transmitter is a Blue tooth module.
6. The writing system as recited in claim 5 wherein said microcontroller includes a UART module and communicates with said Blue tooth module utilizing a universal asynchronous receiver transmitter protocol.
7. The writing system as recited in claim 5 wherein said Blue tooth module includes a USART module and communicates with said microcontroller module utilizing a universal synchronous asynchronous receiver transmitter protocol.
8. The writing system as recited in claim 1 and wherein said microcontroller is configured to filter said accelerometer output and said gyroscope output utilizing Kalman filtering.
9. The writing system as recited in claim 8 and wherein said microcontroller is configured to compensate for rotation of said accelerometer output and said gyroscope output before utilizing said Kalman filtering.
10. The writing system as recited in claim 1 and wherein said microcontroller is configured to compensate said accelerometer output and said gyroscope output to create a zero bias output signal.