Touch-sensitive interface for measuring an intensity of a pressing force

A user interface, comprising:

• a plate, defining a contact surface configured to be touched by an external body;
• at least one actuation transducer, configured to make the plate vibrate, as a function of an activation signal;
• at least one detector configured to detect an amplitude of a vibration of the plate or to generate a detection signal, the detection signal oscillating according to an oscillation amplitude dependent on the detected vibration amplitude;
• an amplification circuit, extending between an input and an output, the input being connected to the detector and the output being connected to the actuation transducer;
• wherein:
• the amplification circuit is configured to be powered by an input signal the input signal being an oscillating signal established from the detection signal;
• the amplification circuit comprises an amplifier, configured to amplify the input signal, by applying an amplification gain, so as to address an output signal to the actuation transducer, the output signal corresponding to the amplified input signal, the output signal forming the activation signal of the actuation transducer;
• the amplification gain depends, nonlinearly, on the input signal;
• the or each detector, the or each actuation transducer, and the amplification circuit form a feedback loop;
• the plate and the feedback loop form a self-sustaining oscillator;
• and wherein the interface comprises a processing unit, powered by a processing signal, the processing signal depending on the input signal or on the detection signal, the processing unit being configured to:
• compare the processing signal with a reference signal;
• generate a force signal, based on the comparison of the processing signal with a reference signal, the force signal being representative of an intensity of a pressing force exerted on the plate by the external body touching the contact surface of the plate.