Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2002-01-02
2003-12-09
Le, N. (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
Reexamination Certificate
active
06661239
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to the field of capacitive sensing, and in particular, to capacitive sensing methods and systems having increased resolution and automatic calibration, suitable for use in a wide variety of products and objects, including, but not limited to, toys and robotic apparatus.
BACKGROUND OF THE INVENTION
In the rapidly expanding universe of interactive toys, robotic devices and other objects, it has long been desirable to provide sensing that enables “intelligent” responses from the object and interactivity with the user. For example, toy manufacturers have long sought to provide baby dolls with “life-like” behavior. One simple approach has involved the use of pushbuttons or contact switches to sense presence or activity, such as squeezing, shaking, patting and the like. Interactive toys such as dolls, simulated animals or other creatures typically contain pushbuttons or squeeze switches to provide tactile sensing.
However, pushbuttons or similar switches suffer from a variety of limitations. They are not natural looking or feeling, and in a doll or toy setting, inhibit natural interaction (imagine, for example, a baby doll with pushbuttons). In addition, many sensing systems typical of the prior art cannot reliably detect touch through several layers of fabric or stuffing or plastics, and leave metallic or other potentially dangerous components exposed on the outside of the toy or other object. Still further, existing switching systems add complexity, cost and reliability problems.
In addition to pushbuttons, various other methods have been proposed for providing presence, contact or activity sensing in toys and other objects. Some examples are described in the following U.S. patents, incorporated herein by reference:
U.S. Pat. No. 4,272,916 Giordano et al.
U.S. Pat. No. 4,879,461 Philipp
U.S. Pat. No. 5,413,518 Lin
U.S. Pat. No. 5,682,032 Philipp
U.S. Pat. No. 5,730,165 Philipp
U.S. Pat. No. 6,039,628 Kusmiss et al.
Among these are a number of capacitive sensing techniques. For example, in U.S. Pat. No. 4,272,916 to Giordano et al. and U.S. Pat. No. 5,413,518 to Lin, capacitive sensing is applied to toys to enable proximity sensing. Examples of capacitive sensing elements and devices are available from Quantum Research Group, Ltd. of Pittsburgh, Pa. (“QProx”). In a “white paper” available at www.qprox.com/background/white_paper.shtml, and in the above-referenced U.S. Pat. Nos. 4,879,461; 5,682,032 and 5,730,165, all incorporated herein by reference, QProx describes various techniques, including a charge-transfer technology incorporated into specialized, single-purpose integrated circuits for capacitive sensing.
From a practical standpoint, however, while capacitive sensing is well-known, the components required by prior art methods and systems have generally been too expensive and complex for deployment in toys and other low-cost objects.
Accordingly, it would be desirable to provide simple, reliable, low-cost capacitive sensing methods and systems suitable for use in a wide range of toys, robotic devices or other objects.
It is also desirable to provide systems and methods that (for toys and dolls) can reliably detect touch through several layers of fabric or stuffing or plastic; do not require metallic or other potentially dangerous components exposed on the outside; present a natural “look” and “feel”, and enable a natural, non-mechanical interaction.
Still further, in many applications it is also desirable to provide methods and systems capable of detecting not only touch, but patterns of touch, such as tickle, pet, bounce, burp, slap, or other. For example, it would be desirable to enable a toy to be able to detect and respond not only to whether the child is playing with the toy, but how the child is playing with the toy.
More particularly, it is desirable to provide advanced signal processing that supports the creation of virtual sensors (e.g., a proximity sensor; a tickle sensor; a pet sensor) that compile and synthesize a wide range of information from one or more simple physical sensors. This functionality would further support recognition and “learning” of signal patterns or signatures. In a toy example, this would provide a powerful interactivity capability, since the toy would know how it is being played with (pet, slap, etc.) and even learn the interactivity patterns of its owner.
It is also desirable to provide such functionality inexpensively, using existing components where possible, with high resolution and automatic and continuous calibration, and with noise rejection to reduce the incidence of false positives (e.g., false detection of touch or touch patterns).
SUMMARY OF THE INVENTION
The present invention provides and enables the foregoing features, benefits, and advantages, among others. In one aspect, the invention comprises low-cost methods and systems for capacitive proximity and contact sensing, using a simple sensor (which may be a conductive fiber or pattern of conductive ink) integrated with a microcontroller, with advanced digital signal processing that provides resolution enhancement, automatic and continuous calibration, noise reduction, and pattern recognition.
Basic Hardware Configuration
In one aspect, the capacitive sensing system includes a power source to supply electrical charge; a microcontroller, in communication with the power source and having at least one digital logic input/output (I/O) pin; a conductive sense element (which may be a plate, surface, wire, thread or conductive ink pattern) coupled to the port, and a resistance element coupled to the sense element. A variable capacitor configuration is formed by the sense plate and an object (such as a human hand) in proximity to the sense plate, and the capacitance thereof is representative of the proximity of the object to the sense element. After the conductive sense element is charged by a voltage placed on the I/O pin, the time (or other parameter) necessary to discharge the sense element through the resistance element can be measured to determine the capacitance, and thus the proximity of an object to the sense element. By digitally processing the signals on the I/O pin, the system can provide resolution enhancement, automatic and continuous calibration, noise reduction and pattern recognition. In particular, the system can be made sensitive to very small changes of capacitance, despite large sensor offsets; relatively insensitive to random sensor noise caused, for example, by nearby electrical circuitry; self calibrating at the factory to compensate for variations in chip specifications and other manufacturing tolerances; and auto-calibrating to compensate for drift over time.
Measurement
In one aspect of the invention, capacitance is measured by measuring the time required to discharge the capacitance through a resistance using the above-described configuration of microcontroller I/O pin, sense element and resistor. In accordance with this aspect, a method includes: setting the I/O pin to OUTPUT mode with its state HIGH, thus charging the capacitor to the supply voltage of the microcontroller; then setting the I/O pin to INPUT mode (referred to hereinafter as changing the direction of the I/O pin or turning around the I/O pin); and then measuring the time required for the voltage measured at the pin (V.pin) to fall below the threshold voltage of the microcontroller. The measured discharge time is approximately proportional to the resistance of the resistor (R.discharge) times total capacitance (C). Since the microcontroller uses a stable clock, digital signal processing techniques are employed to make high-resolution measurements of time. In this way, small changes in capacitance (C) can be reliably measured.
In another aspect of the invention, capacitance is measured by counting pulses required to discharge the capacitance through a resistance. By counting pulses of fixed magnitude, a measure of capacitance is obtained. The digital signal processing techniques described herein are equally applicable to capacitance me
He Amy
iRobot Corporation
Le N.
Lucash, Gesmer & Updegrove, LLP
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