Operational feedback using capacitive sensing
Disclosed devices may include a membrane, a first electrode supported by the membrane, a second electrode, a capacitance sensor configured to determine a capacitance measurement between the first electrode and the second electrode, and a controller configured to control an electrical potential applied between the electrode and the second electrode. The controller may be configured to modify the electrical potential based on the capacitance measurement. Example devices may include one or more flexible membranes that may, at least in part, define an enclosure that is at least partially filled with a dielectric fluid. Examples also include associated methods and systems.
1. A device, comprising:
a membrane;
a first electrode supported by the membrane;
a weakly electrically conductive layer disposed on an inner surface of the first electrode;
a second electrode;
a dielectric fluid located between the weakly electrically conductive layer and the second electrode;
a sensor configured to measure a capacitance between the first electrode and the second electrode; and
a controller configured to control, based on the capacitance measured by the sensor, an electrical potential between the first electrode and the second electrode,
wherein:
the electrical potential induces an electrical polarization in the weakly electrically conductive layer; and
the controller is configured to adjust the electrical potential to:
exclude at least a portion of the dielectric fluid from between the weakly electrically conductive layer and the second electrode due to an electrostatic attraction therebetween; and
modify a resistance to a displacement of the membrane.
2. The device of claim 1 , wherein the electrical potential induces a movement of the first electrode towards the second electrode.
3. The device of claim 2 , further comprising an enclosure that is at least partially filled with the dielectric fluid, wherein the movement of the first electrode towards the second electrode urges the dielectric fluid from between the first electrode and the second electrode.
4. The device of claim 3 , wherein the capacitance is responsive to an area of the device in which the portion of the dielectric fluid is displaced from between the first electrode and the second electrode.
5. The device of claim 1 , wherein the device comprises an actuator, and the electric potential induces the displacement of at least a part of the actuator.
6. The device of claim 5 , wherein the controller is configured to determine the displacement based on the capacitance.
7. The device of claim 1 , wherein the device is a wearable device.
8. The device of claim 7 , wherein:
the device is a haptic device to be worn by a user; and
the device is configured to provide a perceptible tactile sensation to the user in response to the electrical potential when the device is worn by the user.
9. The device of claim 7 , wherein the device comprises a wristband or a glove.
10. The device of claim 1 , wherein the weakly electrically conductive layer has a resistivity of between 10 10 ohm.cm and 10 12 ohm.cm.
11. The device of claim 1 , wherein the electrical polarization induces the electrostatic attraction between the weakly electrically conductive layer and the second electrode or a layer thereon.
12. The device of claim 1 , wherein:
the device further comprises a second weakly electrically conductive layer disposed on the second electrode; and
the electrical polarization induces the electrostatic attraction between the weakly electrically conductive layer and the second weakly electrically conductive layer.
13. The device of claim 1 , wherein the controller is further configured to determine an external applied force exerted on the membrane based on the capacitance.
14. The device of claim 13 , wherein the controller is further configured to:
determine a preload on the device based on the external applied force; and
modify the electrical potential based on the preload.
15. A method, comprising:
applying an electric potential determined by a controller between a first electrode and a second electrode of a device comprising a membrane to induce a displacement of the membrane,
wherein
the first electrode is disposed on the membrane,
a weakly electrically conductive layer is disposed on an inner surface of the first electrode, and
a dielectric fluid is located between the weakly electrically conductive layer and the second electrode;
measuring a capacitance between the first electrode and the second electrode to determine the displacement of the membrane; and
modifying the electric potential based on the capacitance, wherein:
the electrical potential induces an electrical polarization in the weakly electrically conductive layer; and
the controller is configured to adjust the electrical potential to:
exclude at least a portion of the dielectric fluid from between the weakly electrically conductive layer and the second electrode due to an electrostatic attraction therebetween; and
modify a resistance to displacement of the membrane.
16. The method of claim 15 , wherein the device is an actuator, and the actuator is configured to provide a haptic signal.
17. A method comprising:
applying an electric potential determined by a controller between electrodes comprising a first electrode and a second electrode separated by a dielectric fluid to induce an electrostatic attraction between the electrodes and formation of a zipped state in which the dielectric fluid is excluded from between the electrodes;
measuring a capacitance between the electrodes to determine an area of the zipped state; and
modifying the electric potential to adjust the area of the zipped state, wherein:
a weakly electrically conductive layer is disposed on an inner surface of the first electrode;
the first electrode is supported on a membrane;
the electrical potential induces an electrical polarization in the weakly electrically conductive layer; and
the controller is configured to adjust the electrical potential to:
exclude at least a portion of the dielectric fluid from between the weakly electrically conductive layer and the second electrode due to the electrostatic attraction; and
modify a resistance to a displacement of the membrane.
18. The method of claim 17 , wherein the method comprises controlling an actuator, the actuator comprising the membrane having the displacement based on the area of the zipped state.
19. The method of claim 17 , further comprising:
providing a first membrane resistance to an external force when the displacement is less than a predetermined threshold displacement; and
providing a second membrane resistance to the external force when the displacement is greater than the predetermined threshold displacement.