Occupant sensor and method for seat belt or other monitoring

Occupant sensors and methods for seat belt or other monitoring applications

This patent application for this invention is entitled to retrospective benefit under 35 USC Section 1 19(e) of US Patent Application Serial No. 60/775,515, filed February 2006.

The present invention relates to occupant detection. In particular, occupant sensors and methods for detecting occupants and methods for using detection are provided.

With respect to detecting an occupant crash, occupant detection determines whether an airbag will be deployed. Various occupant detection systems have been proposed. Ultrasound, infrared electric field, capacitance, weight, or combinations thereof have been used. The occupant detection system uses antennas located at various locations within the vehicle, such as in a windshield, vehicle roof liner, floor mat, or seat. The antenna uses a piezoelectric material, a conductive material, or other structure. For example, conductive fabric or flexible metal electrodes in the seat allow for capacitive or full-length based detection of the occupant. A strain gauge (instrument) or other associated pressure sensing sensor on a flexible electrical material in the base portion of the seat detects the occupant.

To differentiate between different types of content, such as occupants and grocery bags, various sensing techniques have been developed. Frequency variation due to different capacitances from different antennas is one technique. Another technique is complex image processing. Classification from different types of data based on experimental or neutral network processing is another technique. Other techniques include determining the field strength from different distances away from the seating area. However, these systems can be complex to distinguish between the various categories of occupants with respect to reliable use with airbag systems.

Preferred embodiments described below include methods, sensors and systems for detecting an occupant or characteristic or for monitoring a seat belt. Occupant sensors associated with multiple antennas or simple single antenna deployments determine the antenna charging or discharging characteristics. By providing a sensor electronic device with each sensor or antenna, a greater variety of systems can be provided. The electronic devices associated with the sensor are communicated using a bus or other connection to a processor. The processor determines the occupant status based on the received sensor information. Different numbers of sensors can be used in the same system.

By determining the change in the voltage or current of the antenna as a function of time, whether it is an occupant can be detected or characterized. In one embodiment, the sensor response is measured in time it takes to reach a particular voltage level. Using charging or discharging, the time to reach two or more different voltage levels is measured. The sensor outputs an excitation signal and monitors the response of the antenna. A comparison is made between the monitored antenna voltage level and some reference voltage level. A resistor network is used to set the different reference levels. A processor determines the occupant status based on the measured time.

The sensor is used to limit air bag operation or for another purpose. The same or different occupant sensors are used for seat belt warning. A seat belt latch sensor determines if the seat belt is being used. The occupant sensor determines whether a seat belt should be used. The vehicle driver is alerted by the occupant when the seat belt is not being used when it should be used.

In a first aspect, a sensor system is provided for seat belt monitoring or occupant detection. The first antenna is adjacent to an occupant space. A first circuit may be operable to sense to the first antenna. A processor may be operable to determine the occupant status as a function of a first information output by the first circuitry. A communication path is coupled to the first circuitry and the processor and is operable to provide first information from the first circuitry to the processor. the processor is remote from the first circuit

In a second aspect, a method is provided for seat belt monitoring or occupant detection. One or more sensor modules are provided. Each sensor module is operable to detect at least one antenna, or at least one measurement circuit. Each sensor module may be operable to detect the presence of an occupant in the vehicle in response. A common processor may be operable to determine occupancy status as a function of detection from the sensor module. Communication is arranged from each of the sensor modules to the common processor. The common processor may be operated with a different number of sensor modules.

In a third aspect, a sensor system is provided for seat belt monitoring or occupant detection. A first antenna is positioned adjacent to one occupied space. A first circuit is coupled to the first antenna. The first circuit is coupled to the first antenna. The first circuit may be operable to vary the voltage or current applied to the first antenna, and to detect the first antenna response to the change as a function of timing.

In a fourth aspect, a method for seat belt monitoring or occupant detection is provided. Antenna adjacent to one occupant space is charged or discharged. The charge or discharge is measured on a time basis with respect to one reference level. An occupancy state of the occupied space is determined as the timing function.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is described in detail with reference to the accompanying drawings.

1 is a block diagram of one embodiment of an occupant sensor for detecting an occupant;

2 is a diagram illustrating a circuit model of an occupant sensor according to an embodiment.

3 is a diagram of an embodiment of measuring the voltage response of an antenna as a function of time.

4 is a diagram of an embodiment of occupant classification based on a measured antenna response.

5 is a diagram illustrating an embodiment of a vehicle seat having an occupant sensor.

6 is a plan view of an antenna and circuit for occupant detection according to an embodiment.

7 is a flowchart of one embodiment of a method for detecting an occupant;

8 is a flowchart of one embodiment of a method for seat belt monitoring.

9 is a diagram illustrating a modular sensor and associated measurement electronics.

10 is a diagram of another embodiment of a measurement electronic device based on a sensor.

11 is a circuit diagram of one embodiment of an electronic device within a processor for determining an occupant status or characteristic.

12 is an embodiment circuit diagram and associated discharge timing for processing liquid adjacent to the sensor.

The response of an antenna is measured as a function of time to changes in voltage or current applied to the antenna. A response, such as integration of the discharging or charging characteristics of the antenna, is mapped to one occupant class. An occupant classification includes no occupant, one occupant, an object (such as a car seat), an occupant of a certain size (eg, 5% female or older, 6 years old or older, or another grouping group), or other classification.

In one embodiment of the occupant sensor system, a sensing circuit within a sampled full-length range uses the sensor's response to one step voltage to determine the sensor's lump capacitance and resistance. A micro-controller excites the antenna. The microcontroller also includes an analog-to-digital controller to determine the voltage measured at the antenna. In order to minimize power consumption and cost, the micro-controller operates at a low frequency with respect to the charge and discharge cycle, and operates with a low ADC bandwidth. The discharge or charge waveform is digitized by aliasing the high frequency content into the pass-band of the converter using under-sampling.

In another embodiment, the electronic device at the sensor output outputs when a specific charge or discharge occurs in the antenna. The time to reach the charge or discharge is used to determine the charge or discharge response. 9-12 are examples of such an embodiment.

1-8 use an occupant sensor system. 9-12 use another embodiment. Occupant sensors or different occupant sensors using the charge or discharge response are used for seat belt monitoring or airbag operation limiting. For example, a full-length base occupant sensor determines the presence of an occupant in a seat that distinguishes between an occupant and an object, or between a 6-year-old size and an even smaller size from a larger occupant. The seat belt latch sensor determines if the seat belt is being used. If the seat belt is not in use, but an occupant is detected (eg 6 years old or larger), a seat belt alert is generated.

1 illustrates one embodiment of an occupant sensor for detecting an occupant or object occupant or feature. The occupant sensor includes a sensor or antenna 12, a voltage step circuit 14, a voltage sense circuit 16, and a series of resistors R0. Additional different or fewer components may be provided. Examples include additional resistors, capacitors, and inductors. As another example, a current step and sense circuit is used in addition to the voltage. As another example, the voltage step circuit 14 is operated more gradually when charging or discharging. More than one antenna 12 with a multiplexer or additional circuitry 14, 16 may be used.

The antenna 12 is an electrode, a loop conductor, a pattern conductor, a linear conductor, or an antenna to be developed next. A single layer or multiple layer antenna may be used. In one embodiment, the antenna 12 is a single loop antenna, but separate transmit and receive antennas may be used.

The antenna 12 is located in the occupant space. For example, the antenna may be located on a window, on a steering wheel, on a dashboard, in a seat, on a seat back, on a seat base, on the floor of a vehicle, or other location. The same antenna 12 may extend to several of these locations, or multiple antennas 12 may be provided for different locations. In one embodiment, a single antenna 12 is positioned on the back of a normally seated adult occupant in a position on a surface adjacent to the occupant space, such as under the fabric, on a seat base or seat. located in the back). For example, the antenna 12 is in a part of the car seat base adjacent to the occupant space and located in the car seat or the like. The seat may be a passenger, driver, bench, bucket or other vehicle seat. Other setting seats may be used, such as movie theater seats.

The voltage step circuit 14 is a voltage or current source coupled to the antenna 12 . The voltage step circuit 14 is a current or later developed device for applying a voltage or current change to a power supply, digital-to-analog converter, or other antenna 12 and a waveform generator such as a transistor or switch. The voltage step circuit 14 outputs only a single step. Optionally, the voltage or current change is repeated, such as by applying a continuous square wave. In one embodiment, the voltage step circuit 14 is a transistor for generating a unipolar square wave between 0 and 5 volts. Even larger or smaller amplitudes, and/or non-square waves (such as sine waves) may be used.

In one embodiment, increasing the voltage portion of each pulse in the pulse train is different from decreasing the pulse portion. For example, the increasing voltage causes the amplitude to gradually reduce electromagnetic interference. Optionally, the rising and falling portion is gradual, the rising portion is stepwise, and the falling portion is gradual.

The voltage sensing circuit 16 is an analog-to-digital converter and voltage and current measurement circuit or processor. In one embodiment, the voltage sensing circuit 16 is a microcontroller that is also used for the voltage step circuit 12 . For example, the voltage sensing circuit 16 has an analog-to-digital converter (ADC) channel, an internal oscillator, and a low voltage consuming device. The circuit is powered from the RC 232 serial port or other port. The output drive capacity of the microcontroller is sufficient to provide a charge pulse to the capacitive load. For ADC5, the reference used above is an external voltage supply sourced by a linear regulator. Other micro-controllers may be used with the same or different features. Optionally, separate devices are provided. For example, an external oscillator is provided. As another example, one external voltage source is an ADC reference.

The voltage sense circuit 16 includes an occupant detection circuit operable to detect an occupant. In an embodiment of the voltage sense circuit 16, such as a processor, the processor characterizes or classifies the occupants as a function of sensed voltage or current. In an optional embodiment, a separate processor or micro-controller is provided to characterize or classify the state of the seat (eg, whether occupied by a person, occupied by a 6-year-old or older person). do.

The voltage sensing circuit 16, voltage step circuit 14 or antenna 12 may be a circuit board, or flexible circuit material, and may be connected with a cable. When the capacitance is measured, the capacitance from the ground plane at the occupant sensor is subtracted from the final value. A metal box or other structure may be used to house the occupant sensor circuitry 14, 16, and plastic, potting, some housing or other housing material may be provided. In one embodiment, copper traces and fills adjacent to the interface are eliminated or reduced. The occupant sensor is guard-banded. A surface mount, flip chip, or other mounting is used for the component.

Fig. 2 shows the occupant sensor model of Fig. 1; V0 is the excitation voltage from the voltage step circuit 14. R0 is the series resistance here. R5 is the circuit lump series resistance minus the sensor and excitation source. Rp is the lumped parallel resistance of the sensor. Cp is the parallel capacitance of the sensor. Vs is the measured response of the sensor. The voltage sense circuit 16 measures V8. The general formula for the capacity that can be known by the sensor is as follows.

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Other formulas for this dose may be used. Other models for the occupant sensor may be used.

The response of the antenna 12 is a function of the antenna 12 capacity. For example, with or without the occupant, the antenna 12 has a capacitive load of 200 pF or less. To distinguish different loads adjacent to the antenna 12, the voltage sensing circuit 16 resolves the change in capacitance to 1 pF. Other dose change resolutions may be provided. The change in the capacitance value is proportional to the delay loop implemented by the system. One upper boundary may be approximately 150 pF, and the lower boundary may be approximately 3 fF. These values are the microcontroller firmware function, the number of cycles per instruction and the internal clock speed of the microcontroller, other values may be used.

The voltage circuit 16 is classified as a function of the antenna 12 response to voltage or changes in the circuit. The voltage sense circuit 16 is operable to measure a response at the antenna 12 as a function of time in response to a first change in voltage or current supplied by the voltage or current step circuit 14 . For example, the voltage step circuit 14 applies a step at a voltage equal to the leading or trailing edge of a square wave. In response to a change in the applied voltage or current, the voltage or current at the antenna 12 is changed. The rate of change varies as a function of time based on the capacity.

Figure 3 shows the antenna 12 voltage over three periods of the applied square wave. The change in voltage changes exponentially due to capacitance. The capacitance generates a gradual voltage change in response to a more abrupt change in the applied voltage. The change is the measured voltage. For example, a change in voltage as the voltage (charging voltage) increases is measured. As another example, the change in the voltage (discharge voltage) as the voltage decreases is measured. The noise effect on the power supply can be measured by measuring the waveform discharge edge. Both the charging and discharging voltage of the antenna 12 can be measured. Optionally, current charging and discharging are measured. In another embodiment, the time to reach a predetermined level is measured.

In one embodiment, the change is measured over a single period. Different measurements from different periods are averaged and filtered. In another embodiment, the measurement circuit samples the change in repetition of the applied voltage period to account for low bandwidth measurement devices. 3 shows a sampling of voltage waveforms at the capacitance of the antenna 12 capacitor. In time, each sample is taken at T+(Δt xn), at which point the corresponding voltage is measured and stored. When rebuilt, each of the n data is Δt with respect to the start of charging or discharging.<b></b>Only time is separated. Data points from multiple periods represent one complete waveform of length T. The voltage is quantified with reduced bandwidth requirements, resulting in increased sensitivity to smaller capacitance values.

Any change properties may be used. For example, a voltage difference at two or more different times indicates an occupant state. The change, rate of change, one value at a particular time in relation to the period or the other characteristic of the antenna charging or discharging response is used. In one embodiment, the measuring circuit or voltage sensing circuit 16 incorporates changes as a function of time at the antenna. The reconstructed charge or discharge waveform region may be less sensitive to noise effects than other characteristics. The area is calculated by integrating using standard numerical techniques such as the trapezoidal rule simplified to arbitrary unit time steps. Both such charging or discharging and charging are integrated. Harmonization of change characteristics can be used. The properties can be filtered. Timing or other sampling is used to evaluate the integral, or to avoid the integral.

A processor, such as a voltage sensing circuit 16, allows to characterize the occupant as a function of the response of the antenna 12. Different values of the response characteristic represent different occupant characteristics. For example, FIG. 4 shows the discharge integral values for an antenna positioned at the seat base near the back. The data space is within a certain specific domain or scale as a function of measurement increment or period time. One absolute time scale may be used. These values differentiate between two or more occupant states, and allow the empty state to be distinguished from all other states. These values can distinguish occupants 6 years or younger from other occupants. Data cluster technology group data allows to separate information based on occupant class and related categories. It can contain one or more types of values. In FIG. 4 , the grounding state corresponds to an occupant's contact with a grounding object in the vehicle. The ungrounded state corresponds to the occupant not directly contacting a grounded object in the vehicle.

A similar group may be used for timing determination. Different occupant states are associated with different rates of charging or discharging.

Data prior to classification or classification can be filtered. In one embodiment, a judgment lock or other filtering disclosed in US Patent Publication No. 2003-0204295 is used, which publication is incorporated herein by reference. Optionally, no additional filtering or decision locking is provided.

5 shows an occupant sensor in the seat 20 of a motor vehicle. The sensor circuits 14 and 16 are circuit boards. Optionally, a flexible circuit is used. 6 is a flexible circuit positioned on the seat 20 and shows an embodiment including an antenna 12 and sensor circuits 14 and 16 . The antenna 12, voltage step circuit 14 and voltage sensing circuit 16 may be implemented on different circuit boards or flexible circuits.

6 shows a flexible circuit material. The flexible circuit includes a flexible film 52 . The flexible film 52 is a flexible circuit material for use as a polymide (Kapton (R)) film, a PET polyester (Mylar (R)) film, PEN polytylene naphthalite, or other known flexible circuit boards. The flexible circuit material may be an active or passive circuit element integrated into the material, or the flexible film 52 has no active or passive circuit components.

The flexible film 52 is one or more antennas 54 and associated signal traces formed in the material. The antenna 54 may be a copper, conductive electrode, tension gauge, pressure sensor, radio frequency antenna, piezoelectric film, semiconductor film based diode or light detector, a combination thereof, or other sensor known to detect the presence or characteristic of an occupant, etc. am. The antenna 54 is intended for use with capacitive or full-length or capacitive based sensing, although weight or other sensors may be used.

The antenna 54 is used by the sensor circuit 58 . The sensor circuit 58 is formed as a flexible circuit on the tail 56 of the flexible circuit material 52 . The signal trace connects the antenna loop 54 or antenna region to the sensor circuitry. The traces are all the same or different material, such as antenna loop 54, such as deposited, etched or rolled annealed copper or other flexible metal or conductive material.

The tail 56 has a length, such as a few inches to a yard. The antenna loop 54 is in the seat 20 . The tail 56 extends from the antenna loop 54 to a location for connection to one connector and another processor device, such as an air bag processor or seat belt warning. For example, the tail 56 extends for connection under one seat.

The flexible film 52 is a solid material, but may include holes in the section containing or remote from the antenna 54 . For example, one or more apertures may be provided for other purposes, allowing greater flexibility, airflow, drainage, and/or drainage. For example, the holes make it easier for the flexible film 52 to conform to the molded sheet structure.

Additional components may be formed and connected to the flexible material 10 . For example, a temperature, humidity or temperature and humidity sensor is coupled to the flexible material 52 or integrated as part of the sensor circuit 58 . In one embodiment, one of said additional sensors known from US Pat. No. 6,816,077 is provided.

In an alternative embodiment, the sensor circuit 58 is on a separate circuit board, such as a two-layer circuit board. Two layers of flexible circuits may also be provided. One layer acts as a ground plane. The ground plane also provides a low transfer impedance ground structure and is isolated to RF. Optionally, no ground plane or shield is used.

The occupant sensor is used for airbag control. For example, the air bag may not be deployed against small children, small adults, or inanimate objects. In another embodiment, the occupant sensor is a sensor system for seat belt monitoring. 5 shows an embodiment for seat belt monitoring. The seat 20 includes an occupant sensor (antenna 12 and sensor circuitry 14, 16), a seat belt latch sensor 24, and a processor 26. Additional different or fewer components may be provided.

The seat belt latch sensor 24 is a conductive switch sensor. When the metal latch of the seat belt is inserted or latched, a conductive path is formed. If the metal latch is not inserted, an open circuit is formed. The seat belt latch sensor 24 detects an open circuit or conduction path based on voltage or current through the seat belt latch device. Other novel seat belt latch sensors 24 may also be used.

The occupant sensor includes an antenna (12). The antenna 12 is for electric field, capacitive, other radio frequency based sensing, infrared, optical, acoustic or other transmitting field sensing. For example, the acoustic sensor may include the antenna 12 and sensor circuitry 16 discussed above in FIG. 1 , 2 , 3 , or 4 . In another embodiment, the voltage sense circuit 16 is a processor, amplifier, filter, application specific integrated circuit, field programmable gate array, digital component, combination thereof, or other novel device for determining the presence or characteristic of an occupant. . For example, the occupant sensor uses pattern recognition or other processing for optical, acoustic or infrared sensing. In another embodiment, one of the occupant detection circuits known in U.S. Patent Nos. 5,406,627, 5,948,031, 6,161,070, 6,329,913, 6,329,914, 6,816,077, and 6,696,948 is used, which is incorporated herein by reference. or used to determine the existence or character of an occupant, such as an inanimate occupant. A loading current or other characteristic associated with the propagation of the radio frequency wave is used to determine the occupant information. Optionally, transmission from the antenna and reception at another antenna are used. Other electric field or capacitive sensing circuits may be used as circuits to determine the occupant effect capacitance, frequency change, current magnitude, voltage magnitude, or other characteristic for the field or capacitive value.

The occupant sensor can distinguish between an occupant and an inanimate object. The occupant sensor makes it possible to distinguish between different classes, such as between at least two different sized occupants. The position, height, posture, weight, head position, and other occupant characteristics of the occupant may additionally and selectively be used based on the position and number of sensors or electrodes.

The processor 26 is the processor of the sensor circuits 14 and 16, the seat belt latch sensor 24, or the separation processor. For example, the processor 26 may be a general purpose processor, digital signal processor, application specific integrated circuit, long programmable gate array, digital circuit, or other development device for generating a warning signal as a function of an input. The processor 26 generates a seat belt alert in response to detection of an occupant by the occupant sensor and in response to detection of a seat belt latch member by the seat belt latch sensor. For example, the occupant sensor detects an occupant in the rear seat of a vehicle, but the seat belt latch sensor does not detect the use of a seat belt in the rear seat position. An audible or visible indication warns the driver and warns the detected occupant. The warning is for the seat position in the vehicle.

The seat belt warning differentiates between occupants of different sizes. For example, a seat belt warning would not be issued for occupants aged 6 years or younger. Car seats may use a latch system rather than a seat belt, and seat belt warnings are avoided for small occupants within the car seat. The division may be different for different seat positions, and there is no size distinction for driver or front passenger seat positions.

7 shows a method for sensing an occupant. Additional, different or fewer actions may be used. The above operations are performed in the order shown or in a different order.

In action 62, a change in voltage or current is applied to the antenna adjacent to the occupant space. One step or more gradual changes are applied. For example, a source of voltage or current is connected or disconnected to or from the antenna. As another example, a waveform generator applies a waveform with a voltage or current amplitude change. The change is an increase or decrease, such as decreasing the voltage or current applied from the waveform generator. The change can be repeated, such as applying a square wave. In one embodiment, the addition or increase of voltage or current is gradually performed to avoid electromagnetic interference. After gradually charging the antenna, the voltage or current is removed more rapidly, discharging the antenna more rapidly than charging the antenna. In other embodiments, the discharging is more gradual, and the charging and discharging are rapid or a step function, or both the charging and discharging are gradual.

In action 64, the response of the antenna is measured as a function of time. The response is to a change in voltage or current applied to the antenna. Due to the capacitance associated with the antenna, the voltage or current of the antenna varies differently or more slowly than the applied waveform. The antenna capacity is a function of the adjacent load. The antenna acts as a capacitive plate and the vehicle or other conductor acts as a ground plate. By measuring the voltage or current at the antenna as a function of time, the influence of an occupant adjacent to the sensor is measured. For example, the discharge response or the antenna characteristic is measured. The property as a function of time represents one or more properties of an occupant. In another embodiment, the response is measured by comparing the voltage or current at the antenna to a predetermined value. To reach the current predetermined value (eg 1/3, 2/3 ), the applied The time from a predetermined value, such as at the beginning of the waveform change, is measured.

In one embodiment, the response to each change is measured during one change. In another embodiment, the response is sampled through multiple iterations of the change to determine the response.

The response is measured as voltage or current. Capacitance, resistance, impedance, or other characteristics may be measured. This measure is indicative of occupant status. Optionally, the response is calculated from the measurement. For example, the area of the charge and discharge response is calculated. By integrating the response as a function of time, the effect of noise can be reduced. In another embodiment, the time from a given start time to reach one or more sizes represents the antenna response to a certain occupant load.

In action 66, some occupants are classified as a function of the response. Threshold, pattern match, multiple measure variance, multiple measure type variance, multiple different computation variances, or a combination of these distinguish two or more occupant states. For example, a raw or average region of discharge characteristics distinguishes between at least two size ranges of occupants based on threshold values.

In one embodiment, a common processor is coupled to the modular sensing circuitry. The sensing circuit communicates measurement information such as integration, voltage value, current value, timing, or other measured characteristic to the common processor. The common processor determines the occupant status for an occupant space. The common processor is remote from the sensing circuitry or antenna, either on the seat surface or under the seat with the sensing circuitry and/or the sensing circuitry and antenna on the side. A bus or other communication path allows a configurable number of modular sensing circuits and associated antennas to be used.

8 shows seat belt monitoring. Using the method of Figure 7, seat belt warnings are generated as a function of classification. Other occupant detection methods may be used. Additionally, fewer operations other than those shown in FIG. 8 may be used. The actions are performed in the order shown or otherwise. For example, act 74 is performed concurrently with or before act 72 .

In action 72, the seat belt is latched and detected. The seat belt sensor detects conductivity or other sensing that the seat belt is latching, extended, or tightened. In action 74, the presence of an occupant is detected as a battlefield. Capacitive, current-carrying, optical or other field-based sensing may be used. Optionally, an acoustic or load sensor is used. The occupant detection discriminates between inanimate objects and humans, and discriminates between occupants in at least two size ranges. In action 76, a seat belt warning is generated if the seat belt is not latched and an occupant is present. For example, an audible alarm or visual indication is generated for an occupant of one size range and not another size range. In other embodiments, the timing of charging or discharging, modular sensors, or a combination thereof are used. 9-11 show an embodiment.

9 shows another embodiment of a sensor system for occupant detection. The electronics in the sensor output an indication of when a particular charge or discharge has occurred in the antenna. The time to reach charge or discharge is used to determine the charge or discharge response. The output is on a communication path to the processor away from the sensor circuitry. Modularity and timing of charging or discharging may be used together as shown in the embodiment of FIG. 9 . Optionally, a timing or modular sensor circuit may be used without other circuitry.

The occupant detection sensor system includes an antenna 93 and sensor electronics 100 , a processor 98 , a bus 94 and a power connection 96 . Additional, different, or few components may be provided, such as providing a power connection 96 as part of the bus 94 .

The sensor 92 includes an antenna 93 having two copper layers separated by a thin dielectric. The lower layer of the antenna 93 is between the upper layer and the seat heater structure or other metal structure of the sheet. This lower layer is used as a blocking layer, such as connected to ground or propagation signals. A separate blocking signal may be used. Other antenna structures as described above with respect to FIG. 1 may be used.

Three sensors 92 are shown, and additional or fewer sensors may be used. The sensor 92 is modular and allows connection of different male sensors 92 . The processor 98 is a common processor and contains instructions for operation with different number sensors 92, or different sets of instructions are loaded based on the number of sensors 92 to be used. Different occupant detection systems determine different characteristics or types of occupants. An ever-increasing number of sensors 92 may determine different or multiple characteristics. Fewer sensors 92 may be used to reduce cost. Due to the modular nature of the sensor 92, it can be used in different situations. Rather than different embodiments, the modular nature allows for the production of component parts and allows the assembly of the desired system with any number of antennas 93 .

The sensor 92 includes a sensor electronics 100 . The sensor electronics 100 includes analog, digital or other circuitry for communicating with the processor 98 . A communication path connects the sensor electronics 100 to the processor 98 . In the embodiment shown in FIG. 9 , the sensor electronic device 100 has a multiple drop serial interface (eg, I<sp>2</sp>It contains circuitry for bus communication as in C bus). In an alternative embodiment, a direct or wire connection is provided between the oaths 92 and the processor 98 . For example, the processor 98 includes multiple inputs for optical coupling with one or more sensors 92 .

The bus 94 is I<sp>2</sp>It is a multiple drop serial interface like the C bus. However, other buses may be used. The power connection 96 may be included as part of the bus 94 or may be separate from it. The bus 94 provides control signals to charge and discharge the sensor 92 and to select charging or discharging for measurement. Additional, different or few control signals may be provided. The bus 94 receives trigger or timing signals from the sensor 92 . For example, the sensor 92 outputs measurements for the individual antennas described above with respect to Figures 1-8. In another embodiment, the sensor 92 outputs a phase, capacitance, current, electric field, or other measured value.

The power connection 96 is connected to the battery. The connection is switchable, such as providing power in response to ignition in an automobile or the like.

9 shows an embodiment of a sensor electronic device 100 for measuring discharge or charge. The sensor electronics 100 includes electronics in response to the antenna 93 to output data such as digital information. Analog data can be output. Circuits such as processors, application specific integrated circuits, analog-to-digital converters, analog circuits, digital circuits, or combinations thereof may be used.

In one embodiment, the sensor electronics 100 comprises the upper and lower layers (sensor and shield electronics), an amplifier 106, a resistor network R1, R2, R3, a sense resistor R sense, a voltage input Vcc, a comparator 104, and a connection or antenna connector for an output (timer/counter trigger). Additional different or fewer components may be provided.

10 shows one embodiment of the sensor electronics 100 circuit embodied in part as a microcontroller or other processor. The comparator 104 and the bus interface electronics are provided within the microcontroller. Control of the measurement point is also provided within the microcontroller. Variations of other treatments may be used.

Each sensor is connected to ground. In one embodiment, the ground is a vehicle body ground. A voltage regulator avoids surges in the input power or voltage. In one embodiment, the regulator is a linear regulator. However, other regulators may be used. The voltage is provided as a signal.

The amplifier 106 has a high slew rate, low DC offset voltage, low input bias current, low noise figure, single supply operation and rail-to-rail output operating voltage range. Vaporizers with other characteristics may also be used. Although shown separately in the figures, the amplifier 106 may be integrated into the microcontroller in other embodiments.

A low pass filter LPF is connected between the microcontroller and the analog selector.

The resistors R1, R2, and R3 have a value equal to 10K ohms. Other higher or lower resistances may be used. The resistors are matched. Optionally, the resistors have different resistances. Additional or different resistor networks may be used. The sensor resistor is small enough to minimize noise at the positive input of the comparator 104 . For example, R-sense is 10K ohms, although larger or smaller values may be used.

Referring again to FIG. 9 , the sensor electronics 100 is operated in conjunction with the processor 98 . The processor 98 selects the connection of the input 102 . Optionally, the sensor electronic device 100 selects the connection. A zero, ground, or low voltage connection is specified as zero. The zero connection eventually makes R2 and R1 in parallel. This arrangement allows the comparator 104 to make 2/3 the amplitude of the full charge as a negative or positive input reference voltage. High voltage or full voltage (eg, Vcc) connections are designated as 1. The 1 connection makes R1 and R3 parallel. Such a device makes the voltage or amplitude 1/3 of the total charge as the reference voltage to the input of the comparator 104 . The high impedance connection is designated as X. The X connection eventually results in no current passing through R1. Since R2 and R3 have the same value, 1/2 amplitude or voltage is input to the comparator 104 . Using the input 102 and the resistor network, the sensor electronics 100 measures three different voltage levels for charging or discharging. Other networks or electronic devices may be used to measure the same or different numbers of voltage magnitudes, such as processor 98, which provides a reference voltage for the comparator. Other characteristics such as current may also be measured.

The different sizes are predetermined by the resistor values. Programmable sizes may also be used, such as including additional network components that can be switched to or from the network. All or only some of the possible sizes may be used as a predetermined component in a given implementation.

After selecting the measured voltage or amplitude, the processor 98 or sensor electronics 100 starts a counter. The counter starts at the charging time of the signal applied to the antenna 93 , but may also start at other times (eg when the first predetermined magnitude is reached). The step input is provided to the amplifier 106 , or the charge is discharged by removing the voltage from the amplifier 106 by the processor 98 or the sensor electronics 100 . When the antenna 93 reaches discharging or charging, the comparator outputs a trigger signal. In response, the processor 98 or sensor electronics 100 measures the counter time it takes to reach the point. Real time, time difference, number of cycles, or other temporary indications may be used. In one embodiment, a trigger signal is generated and the common processor 98 determines the time information.

The process is repeated for different measurement points (eg, 1/3, 1/2, and 2/3), or charging or discharging of the antenna 93 . Even a small number of measurements, such as one, two or three measurements, may be used for each of the sensors 92 . In one embodiment, three measurements for charging, three for discharging, and six measurements are used. Any number of measurements may be used. The sensors 92 are operated sequentially, but may be operated simultaneously. Different timing measurements are used by the processor 98 to determine the occupant status. The timing represents, corresponds to, or substitutes for the area or integral of charging or discharging.

A known dose can be used as a reference to improve the accuracy of the measurement. The analog selector is a switch, transistor, relay, or other device for selecting between the different connections. Instead of connecting to the sensor, a resistor R sense is optionally connected to one or more reference capacitors (eg, C1 and C2). At the start of an operation or other time, a reference dose (eg, C1 or C2) is measured. For example, both known doses C1 and C2 are measured. The result is used to compensate for the value measured from the sensor. A look-up table, function, or other relationship may be used to adjust the measured value, adjust the calculated result, or select a different best component based on the reference measure. By using the reference measurement, it is possible to compensate for the circuit variations or temperature effects.

The sensor electronic device 100 may remove or reduce noise due to current injection. The sensor electronics 100 may be coupled to the processor 98 in series, parallel, or other formats.

The processor 98 may be a general purpose processor, integrated circuit, field programmable gate array, analog circuit, digital circuit, combination thereof, or other advanced device to determine occupant status from sensor measurements. Any occupant status determination may be used, such as a cluster to determine an occupant class.

In one embodiment, the processor 98 is the master controller for the bus 94 . The processor 98 communicates with a determined occupant classification device, such as an air bag controller or seat belt warning system.

11 shows one embodiment of the processor 98 . The processor 98 is a serial bus EEPROM, a microcontroller for a sorting device, and a CAN transceiver for communication with an automotive system.

The processor 98 is on the same circuit board, in one and the same housing, and adjacent the sensor electronics 100 . For example, as long as a tail or wire can accommodate one or more electronic devices connecting the antenna 93 to the electronic device 100, each of the one or more sensor electronic devices 100 in the housing is connected. A backplane or other connector connects the electronic device 100 to the processor 98 in the housing. In another embodiment, the processor 98 is remote from the sensor electronics 100 . For example, the sensor electronic device 100 is a flexible circuit and is located adjacent to the antenna 93 adjacent to the occupant space. The processor 98 is located elsewhere in the vehicle, such as under the seat. The processor 98 is in a separate housing.

In one embodiment, the processor 98 operates for a single occupant space. For each occupant space (eg, seat area), a separate processor 98 is provided. In another embodiment, a processor 98 determines the occupant status for two or more occupant spaces.

The system can operate without specific wet detection. In other embodiments, different sensor connections or combinations may be used to reduce the effect of a liquid or to measure and compensate for the effect of a liquid. In an alternative embodiment, a separate wet sensor is used. Liquid adjacent to the sensor may affect the measurement depending on the shielding, insulating, waterproofing, location or other characteristics of the sensor system. The liquid between the sensor and the load may be susceptible to altering electric field measurements such as capacity. By measuring wetting, the effect can be counteracted by adjusting the measured value, function, threshold or other information.

In one embodiment, the real and imaginary components of the measured signal are separated. By measuring the change in only the real component, any liquid adjacent to the sensor can be detected, or the effect of the liquid can be reduced. The capacitive component is more likely to respond to liquid. Using either the resistive or capacitive component, a sufficient amount of liquid or effect can be detected. Due to the detected liquid, a misleading signal or default output can be generated independent of the measured occupancy. Additionally or alternatively, the measured values are compensated for the measured liquid, such that the measured values are compensated for with a capacitive value based on the resistance value.

In order to separate the real and imaginary components, two discharge paths may be provided. 12 shows an embodiment with two discharge paths. The two discharge paths include selectable discharge resistors RdI and Rd2. The resistive and capacitive components are calculated separately using the resistance value of each path and the corresponding discharge time. Measuring the discharge time (t dchgl, t dchg2) using each path allows the processor to distinguish between C and R. chamberlain:

<img file="KR20080098375A_D0002.tif" />

where Eisf 5 volts, RdI is 46 K ohms, Rd2 is 270 K ohms, and Vt is set to the desired threshold. Other values may also be used.

Although the present invention has been described above with reference to several embodiments, many modifications are possible without departing from the scope of the present invention.