Low power adaptive linear resonant actuator driver using accelerometer

Patent metadata

Field	Value
Publication number	US-10868486-B2
Application number	US-201916379228-A
Country	US
Kind code	B2
Filing date	Apr 9, 2019
Priority date	Apr 9, 2019
Publication date	Dec 15, 2020
Grant date	Dec 15, 2020

Abstract

An accelerometer and a linear resonant actuator (LRA) are mechanically coupled, such as by being mounted to the same circuit board. The output of the accelerometer is evaluated in order to select a drive frequency for the LRA. For example, the drive frequency may be varied while measuring the magnitude of acceleration induced by the LRA. The output of the accelerometer may further be used to perform a fitness tracking function, such as counting steps or detecting an activity level.

First claim

The invention claimed is:

1. An apparatus comprising:
an accelerometer;
a linear resonant actuator (LRA) mechanically connected to the accelerometer; and
a controller coupled to the accelerometer and the LRA and programmed to drive the LRA according to an output of the accelerometer;
wherein the controller is programmed to:
(a) increment a current drive frequency;
(b) drive the LRA according to the current drive frequency;
(c) compare a first magnitude of acceleration as measured by the accelerometer while the LRA was driven according to the current drive frequency to a second magnitude of acceleration as measured by the accelerometer while the LRA was driven according to a previous value of the current drive frequency;
(d) if the first magnitude is greater than the second magnitude, repeat from (a); and
(e) if the first magnitude is less than the second magnitude, decrement the current drive frequency and repeat from (b).

2. The apparatus of claim 1 , wherein the LRA and the accelerometer are mounted to a first circuit board.

3. The apparatus of claim 2 , wherein the controller is mounted to a second circuit board different from the first circuit board.

4. The apparatus of claim 1 , wherein the controller is programmed to:
measure variation in magnitude of acceleration as measured by the accelerometer with respect to frequency; and
select a drive frequency for the LRA in accordance with the variation in magnitude.

5. The apparatus of claim 1 , wherein the controller is further programmed to select an initial value for the current drive frequency by driving the LRA according to a range of frequencies and selecting the initial value according to a frequency of the range of frequencies for which a magnitude of acceleration as measured by the accelerometer was largest relative to other frequencies of the range of frequencies.

6. The apparatus of claim 1 , further comprising a pulse width modulation (PWM) driver coupled to the controller and the LRA, the controller being programmed to cause the PWM driver to input a series of pulses approximating a sine wave having the current drive frequency into the LRA.

7. The apparatus of claim 6 , further comprising a half bridge circuit, the PWM driver being coupled to the LRA through the half bridge circuit.

8. The apparatus of claim 6 , wherein a switching frequency of the PWM driver is greater than a cut off frequency of the LRA.

9. An apparatus comprising:
an accelerometer;
a linear resonant actuator (LRA) mechanically connected to the accelerometer; and
a controller coupled to the accelerometer and the LRA and programmed to drive the LRA according to an output of the accelerometer;
wherein the controller is further programmed to perform a fitness tracking function according to the output of the accelerometer.

10. A method comprising:
providing an accelerometer;
providing a linear resonant actuator (LRA);
coupling vibration of the LRA to the accelerometer;
controlling, by a controller coupled to the accelerometer and the LRA, drive input to the LRA according to an output of the accelerometer; and
performing by the controller:
(a) incrementing a current drive frequency;
(b) driving the LRA according to the current drive frequency;
(c) comparing a first magnitude of acceleration as measured by the accelerometer while the LRA was driven according to the current drive frequency to a second magnitude of acceleration as measured by the accelerometer while the LRA was driven according to a previous value of the current drive frequency;
(d) when the first magnitude is greater than the second magnitude, repeat from (a); and
(e) when the first magnitude is less than the second magnitude, decrement the current drive frequency and repeat from (b).

11. The method of claim 10 , wherein coupling vibration of the LRA to the accelerometer comprises mounting the LRA and the accelerometer to a first circuit board.

12. The method of claim 11 , wherein the controller is mounted to a second circuit board different from the first circuit board.

13. The method of claim 10 , further comprising, by the controller:
measuring variation in magnitude of acceleration as measured by the accelerometer with respect to frequency; and
selecting a drive frequency for the LRA in accordance with the variation in magnitude.

14. The method of claim 10 , further comprising, by the controller:
selecting an initial value for the current drive frequency by driving the LRA according to a range of frequencies and selecting the initial value according to a frequency of the range of frequencies for which a magnitude of acceleration as measured by the accelerometer was largest relative to other frequencies of the range of frequencies.

15. The method of claim 10 , further comprising:
generating, by a pulse width modulation (PWM) driver, a series of pulses approximating a sine wave at the current drive frequency; and
inputting the series of pulses into the LRA.

16. The method of claim 15 , further comprising:
inputting the series of pulses into the LRA through a half bridge circuit.

17. The method of claim 15 , wherein a switching frequency of the PWM driver is greater than a cut off frequency of the LRA.

18. A method comprising:
providing an accelerometer;
providing a linear resonant actuator (LRA);
coupling vibration of the LRA to the accelerometer;
controlling, by a controller coupled to the accelerometer and the LRA, drive input to the LRA according to an output of the accelerometer; and
performing, by the controller, a fitness tracking function according to the output of the accelerometer.

Assignees

• Ambiq Micro Inc

Inventors

• Mortazavi Yousof
• Hanson Scott Mclean

Classifications

• H04L67/535

  Tracking the activity of the user (network monitoring arrangements H04L43/00; recording of computer activity G06F11/34) · CPC title

• G01P15/00

  Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration · CPC title

• G06F3/016

  Input arrangements with force or tactile feedback as computer generated output to the user · CPC title

• H02P25/032 Primary

  Reciprocating, oscillating or vibrating motors · CPC title

• G01C22/006

  Pedometers · CPC title