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1. (WO2017037117) ELECTROACTIVE POLYMER SENSORS AND SENSING METHODS
Nota: Texto obtenido mediante procedimiento automático de reconocimiento óptico de caracteres.
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CLAIMS:

1. A system, comprising:

an electroactive material sensor (22); and

a control system (28) for performing measurements of an electrical characteristic which comprises an impedance or an impedance phase angle of the

electroactive material sensor at at least a first frequency and at a second frequency different from the first frequency,

wherein the control system is adapted to derive from the measurements a temperature at the electroactive material sensor and an external pressure or force applied to the electroactive material sensor.

2. A system as claimed in claim 1, wherein the electroactive material sensor comprises a device which functions both as an actuator and as a sensor.

3. A system as claimed in claim 1 or 2, wherein the first frequency is a resonance frequency at which the electrical characteristic has a maximum or minimum value, such as an anti-resonance frequency.

4. A system as claimed in any preceding claim, wherein the second frequency is a frequency at which the electrical characteristic is constant with respect to load.

5. A system as claimed in any preceding claim, wherein the control system is adapted to apply a drive signal onto which measurement signals of the first and second frequencies are superposed, wherein the drive signal comprises a DC drive level or an AC drive signal with a frequency below the first and second frequencies and wherein optionally the measurement signals each have an amplitude of at most 10% of the amplitude of the drive signal.

6. A system as claimed in any preceding claim, comprising an array of sensors, wherein at least some of the sensors have different first frequencies.

7. A system as claimed in any preceding claim, wherein the controller is adapted to modify the derived external force or pressure based on the derived temperature.

8. A system as claimed in any preceding claim, wherein the electrical characteristic comprises an impedance value such as a series resistance.

9. A system as claimed in any preceding claim, wherein the electroactive material comprises a relaxor ferroelectric.

10. A sensing method using an electroactive material sensor, comprising:

performing measurements of an electrical characteristic which comprises an impedance or an impedance phase angle of the electroactive material sensor at at least first and second different frequencies; and

deriving from the measurements a temperature at the sensor and an external pressure or force applied to the sensor.

1 1. A method as claimed in claim 10, wherein the first frequency is a resonance frequency, such as an anti-resonance frequency, at which the electrical characteristic has a maximum or minimum value and the the second frequency is a frequency at which the electrical characteristic is constant with respect to load applied.

12. A method as claimed in one of claims 9 to 1 1 wherein the electroactive material sensor comprises a device which functions both as an actuator and as a sensor and the method comprising applying a drive signal and superposing measurement signals of the first and second frequencies, wherein the drive signal comprises a DC drive level or an AC drive signal with a frequency below the first and second frequencies.

13. A method as claimed in any one of claims 9 to 12 comprising modifying the derived external force or pressure based on the derived temperature.

14. A method as claimed in any one of claims 9 to 13, comprising performing a calibration operation to determine the first and second frequencies, wherein the calibration operation comprises applying a first frequency sweep with no actuation signal and applying a second frequency sweep with an actuation signal.

15. A system or method as claimed in any of the claims 1 to 14, wherein the electroactive material is chosen from the group consisting of: organic electroactive materials, polymer electroactive materials.