Control device with an accelerometer system

1. A control device comprising:

a two-dimensional inertial system configured to measure acceleration of the control device;

a control circuit coupled to the two-dimensional inertial system wherein the control circuit is configured to:

receive acceleration information for the acceleration measured by the two-dimensional inertial system,

integrate the acceleration information to calculate a velocity of the control device,

determine if the velocity of the control device becomes zero along one or both of the two dimensions for which the two-dimensional inertial system is configured to measure acceleration, and

correct a drift in the velocity if the control circuit determines that the velocity is zero along one or both of the two dimensions, and

a vibration detection system configured to detect a vibration of the control device as the control device moves across a surface,

wherein one or both of an amplitude and frequency of the vibration are correlated to the velocity of the control device,

wherein the control circuit is configured to average a weighted sum of the velocities determined from the one or more of the amplitude and the frequency of the vibration and the velocity determined by the control circuit from the acceleration information,

wherein the control circuit is configured to weight more the velocity determined from the one or more of the amplitude and the frequency of the vibration if the acceleration is at or below a threshold acceleration, and

wherein the control circuit is configured to weight more the velocity determined by the control circuit from the acceleration information if the acceleration is above the threshold acceleration.

2. The control device of claim 1 wherein the velocity along one or both of the two dimensions is zero if the control device changes a direction of motion under user control.

3. The control device of claim 1 wherein the inertial system includes microelectromechanical systems (MEMS) accelerometers operable to measure acceleration of the control device along the two dimensions.

4. The control device of claim 1 wherein the two dimensions are parallel to a bottom of the control device.

5. The control device of claim 1 wherein the control device is a mouse or a remote control.

6. The control device of claim 1 wherein the control circuit is configured to correct the drift of the velocity if the control circuit detects that one or more of an amplitude and a frequency of the vibration falls below a preset value.

7. The control device of claim 6 wherein if the velocity determined from the vibration is the same as the velocity determined by the control circuit, the control circuit is configured to correct the drift of the velocity determined by the control circuit from the acceleration information.

8. A method comprising:

receiving acceleration data corresponding to an acceleration of a control device measured by a two-dimensional inertial system;

calculating a first velocity of the control device based on the acceleration data;

receiving vibration data from a vibration detection system configured to detect a vibration of the control device as the control device moves across a surface,

determining a second velocity of the control device based on one or both of an amplitude and frequency of the vibration; and

determining an average velocity of the control device based on the first and second calculated velocities,

wherein the control circuit weights more the second velocity if the acceleration data indicates that the acceleration of the control device is at or below a threshold acceleration, and

wherein the control circuit weights more the first velocity if the acceleration data indicates that the acceleration of the control device is above the threshold acceleration.

9. A control device comprising:

a control circuit;

a two-dimensional inertial system coupled to the control circuit and configured to measure an acceleration of the control device, wherein the control circuit calculates a first velocity based on the measured acceleration of the two-dimensional inertial system;

a vibration detection system coupled to the control circuit and configured to detect a vibration of the control device as the control device is moved along a work surface, wherein the control circuit calculates a second velocity based on at least one of an amplitude or frequency of the vibration,

wherein the control circuit calculates an average of a weighted sum of the first and the second velocities,

wherein the control circuit weighs the first velocity more than the second velocity if the measured acceleration is above a predetermined threshold acceleration, and

wherein the control circuit weighs the second velocity more than the first velocity if the measured acceleration is at or below the predetermined threshold acceleration.