Capacitive sensor systems and methods with increased resolution and automatic calibration

• US 6,661,239 B1
• Filed: 01/02/2002
• Issued: 12/09/2003
• Est. Priority Date: 01/02/2001
• Status: Active Grant

• Current Assignee: iRobot Corporation
• Original Assignee: iRobot Corporation
• Inventors: Ozick, Daniel N.
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): He, Amy
• Application Number:
  US10/038,111
• Time in Patent Office: 706 Days
• Field of Search: 324/658, 324/663, 324/678, 324/686, 324/76.66, 345/173, 345/163, 738/623.37
• US Class Current: 324/658
• CPC Class Codes: G01D 18/006 Intermittent recalibration
• CPC Class Codes: G01D 18/008 with calibration coefficients stored in memory
• CPC Class Codes: G01D 5/2405 by varying dielectric
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2217/94026 Automatic threshold calibration; e.g. threshold automatically adapts to ambient conditions or follows variation of input

Abstract

Methods and systems for capacitive proximity and contact sensing employ one or more simple sensors (which may be a conductive fiber or pattern of conductive ink) in communication with a microcontroller. Digital signal processing executed by the microcontroller enables resolution enhancement, automatic and continuous calibration, noise reduction, pattern recognition and the configuration of virtual sensors capable of detecting how an object incorporating the sensors is being manipulated.

Claims

1. A capacitive sensing system comprising:

a microcontroller, operable to receive electrical power from an electrical power source, and having at least one digital logic input/output (I/O) port;

a conductive sense element in electrical communication with the port; and

a resistance element in electrical communication with the sense element to form an electrical pathway from the sense element to an electrical discharge point;

wherein the microcontroller is further operable to;

at a first time, charge the sense element by causing a selected voltage to be place on the port;

at a second time, cease placing the selected voltage on the port;

thereafter, measure voltage at the port, the voltage at the port being representative of voltage at the sense element; and

measure a parametric value required for voltage at the sense element to decline to a value below a threshold value, the parametric value being representative of an effective capacitance formed by at least the sense element and a first object that may be in contact or proximity with the sense element, whereby the parametric value is representative of contact or proximity between the sense element and the first object; and

wherein the microcontroller is further operable to perform digital signal processing on signals derived from the sense element, such signal processing including pattern recognition comprising the synthesis of at least one virtual sensor capable of detecting selected patterns of contact or proximity between the first object and the sense element; and

wherein the selected patterns of contact or proximity include any of activity, hold, squeeze, tickle, pet, slap, rhythm or bounce patterns; and

wherein the capacitive sensing system is adapted for embedding in a second object.

2. A capacitive sensing system comprising:

a microcontroller, operable to receive electrical power from an electrical power source, and having at least one digital logic input/output (I/O) port;

a conductive sense element in electrical communication with the port; and

a resistance element in electrical communication with the sense element to form an electrical pathway from the sense element to an electrical discharge point;

wherein the microcontroller is further operable to;

at a first time, charge the sense element by causing a selected voltage to be placed on the port;

at a second time, cease placing the selected voltage on the port;

thereafter, measure voltage at the port, the voltage at the port being representative of voltage at the sense element; and

measure a parametric value required for voltage at the sense element to decline to a value below a threshold value, the parametric value being representative of an effective capacitance formed by at least the sense element and a first object that may be in contract or proximity with the sense element, whereby the parametric value is representative of contact or proximity between the sense element and the first object;

wherein the microcontroller is further operable to perform digital signal processing on signals derive from the sense element, the signal processing including automatic calibration; and

wherein the microcontroller is further operable to

detect, at power-up, a first stable value at the sense element;

designate that first detected stable value as an initial calibration value;

increment, at a fixed interval, the initial calibration value;

thereafter, continuously examine detected values; and

when a new stable value lower than a current calibration value is detected, replace the current calibration value with the new stable value.

3. The A method of capacitive sensing, the method comprising:

providing a microcontroller, operable to receive electrical power from an electrical power source, and having at least one digital logic input/output (I/O) port;

providing a conductive sense element in electrical communication with the port, and

providing a resistance element in electrical communication with the sense element to form an electrical pathway from the sense element to an electrical discharge point; and

configuring the microcontroller to;

at a first time, charge the sense element by causing a selected voltage to be placed on the port;

at a second time, cease placing the selected voltage on the port;

thereafter measure voltage at the port, the voltage at the port being representative of voltage at the sense element; and

measure a parametric value required for voltage at the sense element to decline to a value below a threshold value, the parametric value being representative of an effective capacitance formed by at least the sense element and a first object that may be in contact or proximity with the sense element, whereby the parametric value is representative of contact or proximity between the sense element and the first object; and

configuring the microcontroller to perform digital signal processing on signals derived from the sense element, such signal processing including pattern recognition comprising

synthesizing at least one virtual sensor capable of detecting selected patterns of contact or proximity between the first object and the sense element wherein the selected patterns of contact or proximity include any of activity, hold, squeeze, tickle, pet, slap, rhythm or bounce patterns; and

adapting the capacitive sensing method for embedding in a second object.

4. A method of capacitive sensing, the method comprising:

providing a microcontroller, operable to receive electrical power from an electrical power source, and having at least one digital logic input/output (I/O) port;

providing a conductive sense element in electrical communication with the port, and

providing a resistance element in electrical communication with the sense element to form an electrical pathway from the sense element to an electrical discharge point; and

configuring the microcontroller to;

at a first time, charge the sense element by causing a selected voltage to be placed on the port;

at a second time, cease placing the selected voltage on the port;

thereafter, measure voltage at the port, the voltage at the port being representative of a voltage at the sense element; and

measure a parametric value required for voltage at the sense element to decline to a value below a threshold value, the parametric value being representative of an effective capacitance formed by the at least one sense element and a first object that may be in contact or proximity with the sense element, whereby the parametric value is representative of contact or proximity between the sense element and the first object; and

configuring the microcontroller to perform digital signal processing on signals derived from the sense element, the signal processing including continuous calibration; and

configuring the microcontroller to

detect, at power-up, a first stable value at the sense element;

designate that first detected stable value as an initial calibration value;

increment, at a fixed interval, the initial calibration value;

thereafter, continuously examine detected values; and

when a new stable value lower than a current calibration value is detected, replace the current calibration value with the new stable value.

5. A capacitive sensing system comprising:

a microcontroller, operable to receive electrical power from an electrical power source, and having at least one digital logic input/output (I/O) port;

a conductive sense element in electrical communication with the port; and

a resistance element in electrical communication with the sense element to form an electrical pathway from the sense element to an electrical discharge point;

wherein the microcontroller is further operable to;

at a first time, charge the sense element by causing a selected voltage to be place on the port;

at a second time, cease placing the selected voltage on the port;

thereafter, measure voltage at the port, the voltage at the port being representative of voltage at the sense element; and

measure a parametric value required for voltage at the sense element to decline to a value below a threshold value, the parametric value being representative of an effective capacitance formed by at least the sense element and a first object that may be in contact or proximity with the sense element, whereby the parametric value is representative of contact or proximity between the sense element and the first object; and

wherein the microcontroller is further operable to perform digital signal processing on signals derived from the sense element, such signal processing including pattern recognition comprising the synthesis of multiple virtual sensors from a single sense element, each virtual sensor being capable of detecting selected patterns of contact or proximity between the first object and the sense element; and

wherein the selected patterns of contact or proximity include any of activity, hold, squeeze, tickle, pet, slap, rhythm or bounce patterns; and

wherein the capacitive sensing system is adapted for embedding in a second object.

6. A capacitive sensing system comprising:

a microcontroller, operable to receive electrical power from an electrical power source, and having at least one digital logic input/output (I/O) port;

a conductive sense element in electrical communication with the port; and

a resistance element in electrical communication with the sense element to form an electrical pathway from the sense element to an electrical discharge point;

wherein the microcontroller is further operable to;

at a first time, charge the sense element by causing a selected voltage to be placed on the port;

at a second time, cease placing the selected voltage on the port;

thereafter, measure voltage at the port, the voltage at the port being representative of voltage at the sense element; and

measure a parametric value required for voltage at the sense element to decline to a value below a threshold value, the parametric value being representative of an effective capacitance formed by at least the sense element and a first object that may be in contract or proximity with the sense element, whereby the parametric value is representative of contact or proximity between the sense element and the first object;

wherein the microcontroller is further operable to perform digital signal processing on signals derive from the sense element, the signal processing including continuous calibration; and

wherein the microcontroller is further operable to

detect, at power-up, a first stable value at the sense element;

designate that first detected stable value as an initial calibration value;

increment, at a fixed interval, the initial calibration value;

thereafter, continuously examine detected values; and

when a new stable value lower than a current calibration value is detected, replace the current calibration value with the new stable value.

7. A method of capacitive sensing, the method comprising:

providing a microcontroller, operable to receive electrical power from an electrical power source, and having at least one digital logic input/output (I/O) port;

providing a conductive sense element in electrical communication with the port, and

providing a resistance element in electrical communication with the sense element to form an electrical pathway from the sense element to an electrical discharge point; and

configuring the microcontroller to;

at a first time, charge the sense element by causing a selected voltage to be placed on the port;

at a second time, cease placing the selected voltage on the port;

thereafter measure voltage at the port, the voltage at the port being representative of voltage at the sense element; and

measure a parametric value required for voltage at the sense element to decline to a value below a threshold value, the parametric value being representative of an effective capacitance formed by at least the sense element and a first object that may be in contact or proximity with the sense element, whereby the parametric value is representative of contact or proximity between the sense element and the first object; and

configuring the microcontroller to perform digital signal processing on signals derived from the sense element, such signal processing including pattern recognition comprising

synthesizing multiple virtual sensors from a single sense element, each virtual sensor being capable of detecting selected patterns of contact or proximity between the first object and the sense element wherein the selected patterns of contact or proximity include any of activity, hold, squeeze, tickle, pet, slap, rhythm or bounce patterns, and

adapting the capacitive sensing system for embedding in a second object.

8. A method of capacitive sensing, the method comprising:

providing a microcontroller, operable to receive electrical power from an electrical power source, and having at least one digital logic input/output (I/O) port;

providing a conductive sense element in electrical communication with the port, and

providing a resistance element in electrical communication with the sense element to form an electrical pathway from the sense element to an electrical discharge point; and

configuring the microcontroller to

at a first time, charge the sense element by causing a selected voltage to be placed on the port;

at a second time, cease placing the selected voltage on the port;

thereafter, measure voltage at the port, the voltage at the port being representative of a voltage at the sense element; and

measure a parametric value required for voltage at the sense element to decline to a value below a threshold value, the parametric value being representative of an effective capacitance formed by the at least one sense element and a first object that may be in contact or proximity with the sense element, whereby the parametric value is representative of contact or proximity between the sense element and the first object; and

configuring the microcontroller to perform digital signal processing on signals derived from the sense element, the signal processing including continuous calibration; and

configuring the microcontroller to

detect, at power-up, a first stable value at the sense element;

designate that first detected stable value as an initial calibration value;

increment, at a fixed interval, the initial calibration value;

thereafter, continuously examine detected values; and

when a new stable value lower than a current calibration value is detected, replace the current calibration value with the new stable value.