Occupant detection and classification sensing in vehicles

Abstract

An occupant detection and classification for use in vehicles. The occupant detection and classification system transmits signals through a conductor. The system then takes measurements from the receiver, the transmitter drive, and the transmitter inductor peak. The measurement data from each signal measured is processed. The processed data is used to determine information about the occupant of a seat.

Description

Docket No.: 648-1-1 PCOCCUPANT DETECTION AND CLASSIFICATION SENSING IN VEHICLES

[0001] This Application claims the benefit of U.S. Provisional Application Serial No. 63 / 701 ,895 filed October 1 , 2024, and U.S. Provisional Application Serial No. 63 / 770,330 filed March 11 , 2025, the contents of the aforementioned applications incorporated herein by reference.FIELD

[0002] The disclosed systems and methods relate in general to the field of sensors and more particularly occupant detection and classification sensors.BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The foregoing and other objects, features, and advantages of the disclosure will be apparent from the following more particular description of embodiments as illustrated in the accompanying drawings in which reference characters refer to the same parts throughout the various views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating principles of the disclosed embodiments.

[0004] FIG. 1 is a high-level illustration of an occupant detection seat sensor.

[0005] FIG. 2 is a high-level illustration of one embodiment of the invention showing connections of a heater and sensor.

[0006] FIG. 3 is a diagram of connections within one embodiment of seat platform.

[0007] FIG. 4 is a block diagram of an embodiment of the seat platform.

[0008] FIG. 5 is another block diagram of an embodiment of the seat platform providing more details of the connection between the electronics and the seat.

[0009] FIG. 6 is yet another block diagram of an embodiment of the seat platform showing a heating path.

[0010] FIG. 7 is a simplified block diagram of an embodiment of the seat platform showing a heating path.

[0011] FIG. 8 is a further block diagram of an embodiment of the seat platform illustrating a sensor path.Docket No.: 648-1-1 PC

[0012] FIG. 9 is another block diagram of an embodiment of the seat platform illustrating a sensor path.

[0013] FIG. 10 is a simplified block diagram of an embodiment of the seat platform illustrating a sensor path.

[0014] FIG. 11 is a diagram of the development SOC platform.

[0015] FIG. 12 is view of the chip used in the OD / OC system.

[0016] FIG. 13 is a view of the ECU main functionality.

[0017] FIG. 14 is a view of the platform signal chain.

[0018] FIG. 15 is a diagram showing primary data input.

[0019] FIG. 16 shows a graph of peak data at different temperatures.

[0020] FIG. 17 shows a close-up view of a peak.

[0021] FIG. 18 is a diagram of an ODS.

[0022] FIG. 19 is a diagram of an ODS.

[0023] FIG. 20 is a diagram of an ODS.

[0024] FIG. 21 is a diagram of seat architecture.

[0025] FIG. 22 shows an embodiment of an ODS implementing two receiving conductors (antennas) and two transmitting conductors (antennas).

[0026] FIG. 23 shows a cross-sectional view of an embodiment of an ODS with receiving conductors (antennas) and one transmitting conductors (antennas).

[0027] FIG. 24 shows a diagram of an embodiment of an ODS with one receiving conductors (antennas) and one transmitting conductors (antennas).

[0028] FIG. 25 shows a cross-sectional view of an embodiment of an ODS with heater conductors and transmitting / receiving conductors (antennas) located adjacent the heater conductors.

[0029] FIG. 26 shows a diagram of an embodiment of an ODS with one receiving conductors (antennas) and two transmitting conductors (antennas).

[0030] FIG. 27 shows a diagram of an embodiment of an ODS with two receiving conductors (antennas) and two transmitting conductors (antennas).

[0031] FIG. 28 shows a diagram of an embodiment of an ODS with multiple sensors embedded therein.

[0032] FIG. 29 shows a diagram of antennas embedded in a vehicle seat and a close-up view of the conductors in the seat.Docket No.: 648-1-1 PC

[0033] FIG. 30 shows a cross-sectional view of a car seat and placement of conductors.

[0034] FIG. 31 shows a cross-sectional view of a car seat and placement of conductors using a dual function heater conductor with dual zones.

[0035] FIG. 32 shows a cross-sectional view of a car seat and placement of conductors using a dual function heater conductor with a single zone.DETAILED DESCRIPTION

[0036] In various embodiments, the present disclosure is directed to sensing systems that are able determine the presence of an object or individual within environments. In general, the sensing systems described herein can sense both objects and people within certain environments. For example, in an embodiment, the sensing system is able to the determine the presence, movement, and position of passengers and objects within a vehicle.

[0037] Referring to Fig. 1 , an occupant detection system (ODS) 100 is shown that employs a multifunctional seat mat 10 configured to provide both sensing and heating capabilities. In one embodiment, the mat 10 incorporates conductive elements arranged such that they can operate as heating elements while also functioning as sensing conductors for occupant detection. In a preferred configuration, the conductors are metallic heater wires embedded within the mat structure, thereby serving a dual role of thermal comfort and detection.

[0038] The ODS 100 may utilize copper or other conductive wire materials as the basis for the heater / sensor conductors. In some embodiments, these conductive materials are sourced from a third-party original equipment manufacturer (OEM). The conductive elements are integrated into the vehicle seat structure, where they provide resistive heating functionality while simultaneously enabling occupant sensing capabilities. The ODS 100 is designed to support both occupant classification and detection, including highly sensitive use cases such as the reliable identification of a one-year-old infant secured in a child safety restraint system. This dual-purpose integration reduces the need for separate sensing hardware while maintaining compliance with occupant safety standards.

[0039] In an embodiment, the ODS 100 comprises three functional components. The first component is a sensor layer, embodied in the seat mat 10, thatDocket No.: 648-1-1 PC physically interacts with the occupant or child seat through the integrated conductors. The second component is an analog front end (AFE), which is responsible for acquiring electrical signals from the mat and conditioning them for further processing. The third component comprises data-processing algorithms configured to interpret the conditioned signals and generate occupant classification outputs. These algorithms may be implemented in dedicated hardware, such as an application-specific integrated circuit (ASIC), to support low-cost, long-term deployment in vehicles and other transportation environments where reliability and durability are critical.

[0040] The CDS 100 operates through the use of the multifunctional seat mat 10, which in many embodiments provides both heating and sensing capabilities. However, the sensing architecture is not limited to operation with heating elements. Although the use of heater conductors is advantageous from a cost and integration standpoint, since the same physical element serves two functions, the underlying detection methodology can operate independently of heating functionality. Accordingly, the CDS 100 may be implemented in vehicle seats with or without integrated heating features, allowing flexibility across a wide range of vehicle classes and configurations.

[0041] In certain embodiments, the ODS 100 is adapted to utilize a seat mat 10 supplied by a third-party OEM. However, the system is not limited to this configuration. The ODS 100 is compatible with a variety of alternative conductive structures that may be substituted for a third-party seat mat. Such alternatives include, but are not limited to, metal strips, whip antennas, or other conductive elements arranged in predetermined topologies and affixed to a vehicle seat according to design specifications. This adaptability allows the ODS 100 to be implemented across diverse seating architectures and manufacturing environments while maintaining consistent occupant detection performance.

[0042] Referring to Fig. 2, shown is an embodiment of ODS 100. In this embodiment, a seat heater 1 is positioned in both the seat back 2 and the seat bottom 4. A block diagram further depicts the general wiring configuration, wherein the conductors extend to an electronic control unit (ECU) 5. The wiring is arranged such that the ECU 5 interfaces with a sensor circuit 3 connected to the same conductors used by the heater. In addition, heater voltage is supplied through a heater control 6, also coupled to the conductors. Switches are incorporated into the ODS 100 toDocket No.: 648-1-1 PC selectively activate either the heating function or the sensing function. The ECU 5 coordinates these functions by controlling heater activation and sensor sampling. Specifically, when the heater is active, the ECU 5 momentarily disconnects the heater to acquire sensor samples, thereby enabling occupant detection without interference from heating currents.

[0043] The sensor circuit 3 is configured to remain connected to the same wiring as the heater control 6, facilitating shared use of the conductors for dual functionality. In one embodiment, a negative temperature coefficient (NTC) thermistor (not shown) is embedded in the seat to provide a control loop for regulating heating output. The inclusion of such a thermistor, however, is optional and intended primarily for illustrative clarity when describing the integration of heating and sensing functions. The ODS 100 can be powered by various sources, including a standard automotive supply, a laptop, or an external 230-volt power supply. Importantly, the ODS 100 does not require the presence of a thermistor to operate. The system is capable of detecting and compensating for thermal drift and seat temperature variations independently, without relying on thermistor-based feedback.

[0044] Additional thermal sensing methodologies or feedback mechanisms may be integrated into the circuit topology if desired. However, the sensor circuit does not require a thermistor, a heater control module, or external computing resources such as a laptop to function. Instead, the sensing functionality may be executed directly by the ECU 5, by an application-specific integrated circuit (ASIC), or through softwarebased processing solutions, thereby allowing flexible implementation across multiple vehicle platforms.

[0045] Fig. 3 illustrates the wiring connections employed in the occupant detection system (ODS) 100. This figure provides a reference for documenting how the system components may be interconnected. In one embodiment, the sensor functionality is integrated with the heater functionality within a single structural layer of the seat. In this configuration, the sensing function is not implemented as a separate layer or dedicated circuit; rather, the heater conductor itself is time-multiplexed to perform as both a heater and a sensing element. Accordingly, the seat mat 10 performs a dual role, utilizing the same conductive wiring network for occupant detection and thermal comfort.Docket No.: 648-1-1 PC

[0046] In one embodiment, a single conductor provides dual functionality across separate operational cycles. During a heating cycle, the conductor is energized by the heater control circuit to deliver resistive heating to the seat structure. During a sensing cycle, the same conductor is repurposed as a sensor input line for the occupant detection system. The electronic control unit (ECU) coordinates these functions by employing controlled switching mechanisms. For example, when occupant sensing is required, the ECU momentarily disconnects the heating voltage source and couples the conductor to the sensor circuit. This switching sequence is performed at predefined intervals or synchronized with low-duty cycles to ensure uninterrupted heating while allowing accurate sensing. The conductor may be fabricated from copper, alternative metallic materials, or conductive composites such as carbon fiber. Regardless of the selected material, the wiring is configured to maintain stable resistance characteristics suitable for both heating uniformity and reliable signal acquisition.

[0047] To ensure accurate sensing, the ECU manages signal isolation between heating and sensing operations. In one implementation, filtering circuits and analog front ends are employed to suppress residual heater currents and electromagnetic interference when the conductor is switched into the sensing mode. Timing logic within the ECU (or an application-specific integrated circuit, ASIC) controls pulse widths, duty cycles, and sampling windows to minimize noise coupling. Although the conductive element is depicted in the context of an CDS 100 that also provides heating, the heater function is not required for sensing operation. The occupant detection capability can operate independently of heating, enabling deployment in vehicle seats without integrated heating systems. This flexibility allows the CDS 100 to adapt across diverse platforms, while the coordinated ECU switching and isolation techniques ensure reliable performance regardless of whether heating is present.

[0048] Fig. 4 illustrates a schematic diagram of an occupant detection system (CDS) 100 that combines heating and sensing functionality into a single integrated system. The CDS 100 may also be referred to as an occupant classification system (OCS). As used herein, the terms CDS and OCS are intended to be interchangeable unless a distinction is explicitly stated. Accordingly, references to either CDS or OCS should be understood to encompass both occupant detection and occupant classification functionalities.Docket No.: 648-1-1 PC

[0049] In one embodiment, the ODS 100 implements a dual-purpose architecture in which the same conductive elements are utilized for both heating and sensing during alternating operational cycles. The ECU 5 generates a specific excitation signal that is transmitted through the conductors, while return signals are received at sensor circuit 3. Sensor circuit 3 comprises the same conductors integrated into the seat back and seat bottom structures, enabling distributed sensing across the seating surface. A transmitter circuit is also included. In the embodiment shown in Fig. 4, the transmitter is realized using a pulse-width modulation (PWM) circuit 8 embedded within an ARM Cortex microcontroller 7, which generates drive signals at specific frequencies. These PWM-generated signals are conditioned by a transmit operational amplifier (Tx Op-Amp Drive 14) and then applied to a transmit inductor 12 connected in series with sensor 3. The inductor-conductor combination forms part of a resonant network, sensitive to impedance variations induced by occupant presence.

[0050] The ODS 100 monitors three distinct sensing points within this circuit topology: (i) the sensor 3 itself, (ii) the output of the transmit inductor 12 (TxL), and (iii) the junction between the Tx Op-Amp Drive 14 and the Tx inductor 12 (TxD). Collecting data from multiple locations enables a comprehensive view of system dynamics. In this embodiment, comprehensive sensing functionality includes the ability to (a) detect the presence of an occupant or object, (b) measure proximity or approach of an occupant or object, and (c) classify the occupant or object based on its electrical signature.

[0051] Signals collected from the sensing points are digitized by a 12-bit analog- to-digital (A / D) converter 9, although converters with higher or lower resolution may also be used depending on cost and performance requirements. The digitized data is then processed using algorithms that may include spectral decomposition techniques such as Fast Fourier Transform (FFT). These algorithms may be executed directly on microcontroller 7 or, alternatively, implemented in a dedicated digital signal processor (DSP) or ASIC optimized for real-time processing in automotive environments.

[0052] The ODS 100 interfaces with external vehicle systems through established communication protocols. In automotive applications, the ECU exchanges data with other modules via Controller Area Network (CAN) or Local Interconnect Network (LIN) buses. In non-automotive implementations, communication may beDocket No.: 648-1-1 PC established using USB or other standardized digital interfaces, enabling integration with laptops, diagnostic equipment, or centralized monitoring systems.

[0053] In one embodiment, PWM serves as the primary mechanism for frequency generation. However, the invention is not limited to PWM techniques. Alternative methods such as direct digital synthesis (DDS), sine-wave oscillators, or waveform generators capable of producing square, triangular, or arbitrary waveforms may also be employed to excite the transmit circuit. PWM is one of several viable approaches.

[0054] The transmitted excitation frequencies may range broadly, from tens of kilohertz into the megahertz spectrum. In one embodiment, the system operates within a range of approximately 50 kHz to 400 kHz, balancing sensitivity with practical circuit design constraints. Nonetheless, this frequency range is exemplary and not limiting, as application-specific requirements may dictate alternative operating ranges.

[0055] In one embodiment, frequency transmission is achieved using a timedivision multiplexing approach, whereby the system sequentially excites the circuit at different frequencies and analyzes the response at each frequency band. In another embodiment, a composite waveform comprising multiple frequencies is generated and transmitted simultaneously, with post-processing algorithms decomposing the received signal into its constituent frequency responses.

[0056] Multiplexing strategies are not limited to time-division methods. In further embodiments, frequency-division multiplexing (FDM) or code-division multiplexing (CDM) techniques may be applied to transmit multiple signals concurrently. These methods enable broader spectral coverage and improved detection performance under complex seating conditions.

[0057] In one embodiment, sensor 3 comprises conductive antenna structures that double as both heating and sensing elements. These conductors may take the form of heater wires, metallic strips, or carbon-fiber threads integrated into the seat mat. Their arrangement provides both uniform heat distribution and broad sensing coverage.

[0058] The ODS 100 advantageously incorporates three sensing points for data collection rather than relying on a single measurement node. Each point yields distinct information about circuit behavior under varying occupant conditions. In alternativeDocket No.: 648-1-1 PC embodiments, one or two sensing points may suffice, but use of all three points provides maximum accuracy and redundancy.

[0059] Electrically, sensor 3 can be modeled as a multiport network whose impedance varies dynamically with occupant presence, posture, or environmental changes. When an external transmission signal interacts with this variable impedance environment, the load presented to the transmit circuitry changes. These changes in load manifest as measurable variations in voltage and current waveforms at the monitored nodes.

[0060] In one embodiment, the sensing environment comprises the seat back 2, seat bottom 4, conductors 1 , and any occupants or objects placed thereon. Variations in this environment alter the overall impedance of sensor 3. By monitoring both the Tx Op-Amp Drive 14 output (TxD) and the transmit inductor 12 output (TxL), the system captures these variations, which correlate to occupancy state and classification.

[0061] Data collected from the three sensing points may be combined to generate a comprehensive assessment of the system’s response. In some embodiments, all three points are analyzed in parallel, while in others, subsets of the data may be used depending on computational or cost constraints. Each location produces signals with distinct amplitude, phase, and spectral characteristics, thereby enriching the overall classification accuracy.

[0062] Changes in impedance within the sensing environment generate unique responses at each measurement node. In a purely resistive environment, responses at different points would remain strongly correlated. However, the seat environment introduces complex impedance effects, including capacitance and inductance contributions, which create variations in response across frequencies and sensing points.

[0063] The CDS 100 detects and interprets these impedance variations to classify objects and occupants. For example, a child safety seat, a small pet, or an adult occupant may produce distinct impedance profiles. The receive (Rx) signals captured from sensor 3 may differ significantly from the transmit drive signals (TxD or TxL), enabling the system to distinguish between object types and refine classification accuracy.Docket No.: 648-1-1 PC

[0064] In one embodiment, the collected signals are analog in nature and digitized by A / D converters before further processing. Measurement of the signal directly between the PWM circuit 8 and the Tx Op-Amp Drive 14 is generally unnecessary, as this point does not yet reflect interaction with the impedance network formed by sensor 3 and the seat environment.

[0065] Valuable information is obtained from both the pre-inductor (TxD) and post-inductor (TxL) signals in the transmit circuit. The configuration of the transmit opamp may be tailored to optimize the fidelity of monitored signals. For example, inverting, non-inverting, or trans-impedance amplifier topologies may be employed, each influencing gain characteristics, signal-to-noise ratio, and sensitivity to impedance changes. Circuit variations at these stages directly affect the utility of the collected data and can be optimized for specific vehicle applications.

[0066] Referring to Figs. 5-10, Fig. 5 illustrates a schematic block diagram showing signal wire connections and their respective roles in achieving the functionality of the occupant detection system (CDS) 100. In one embodiment, fieldeffect transistors (FETs) 19 are employed as electronic switches to control current flow and to provide electrical isolation between heating and sensing circuits. This arrangement enables the system to support two distinct operational modes — heating and sensing — using the same conductor without requiring separate wiring layers.

[0067] In one embodiment, conductor 1 may be implemented as part of a seat mat 10, a whip antenna, or another metallic conductor integrated into the seat assembly. In the embodiment depicted, conductor 1 corresponds to elements located within both the seat bottom 4 and the seat back 2. FETs 19 are used to isolate signals within the circuitry, such that the transmit inductor 12 can be selectively coupled to conductor 1 while simultaneously providing a connection path to the receive circuit. A 12-volt power source is applied to the FETs 19, which enables continuous monitoring of the receive circuitry even during non-sensing periods. These connection points are designed to tolerate elevated voltages and currents generated during heating mode operation. The receive circuit, while remaining electrically connected, remains dormant until sensing mode is engaged.

[0068] During occupant sensing operation, the heater circuit 6 is electrically isolated, and conductor 1 ceases to conduct the relatively high heating currents that typically range from approximately 4 A to 12 A. Designing a circuit capable of reliablyDocket No.: 648-1-1 PC handling both high-current heating and low-level sensing signals presents a technical challenge. Low-cost FETs 19 can introduce parasitic resistances, capacitances, and inductances into the circuit, which may affect accuracy and sensitivity. Nonetheless, the use of FETs allows effective isolation of the sensing function, while maintaining a sufficiently high impedance barrier to prevent unwanted heating current flow into the sensing path. This configuration enables accurate detection without interference from residual heater currents.

[0069] Although other switching technologies such as bipolar junction transistors (BJTs) or solid-state relays may be used to perform similar functions, FETs 19 are preferred in this embodiment due to their superior switching speed and efficiency. The high switching speed reduces interference with heater operation by enabling rapid transitions between heating and sensing cycles. In addition, FETs exhibit lower parasitic capacitance and resistance compared to alternative switching devices, which improves fidelity of the sensing measurements. These attributes make FETs well suited for high-power applications such as motor drives, power converters, and power regulators, where efficient, high-speed switching is critical. Leveraging these same characteristics in the ODS 100 ensures cost-effective and reliable performance. While other switch types may be substituted, FETs 19 offer an advantageous balance of availability, cost, and electrical performance for dual- purpose heating and sensing circuits.

[0070] The receive circuitry of ODS 100 is engineered to tolerate exposure to high voltage levels, even though its primary function is to detect signals at millivolt or microvolt amplitudes. In one embodiment, the receive circuit is capable of withstanding voltage spikes up to approximately 14 V, which may occur depending on the state of the vehicle’s battery charging system. Protective circuitry, such as clamping diodes, transient voltage suppression (TVS) devices, or surge arresters, is integrated into the receive path to mitigate excessive voltage exposure. These protective elements ensure reliable operation of the receive circuit by safeguarding sensitive analog frontend components from transient overvoltage conditions, thereby maintaining accuracy and extending system longevity.

[0071] Fig. 6 illustrates current flow in the occupant detection system (ODS) 100 when the heating function is active. In this operational mode, the field-effect transistors (FETs) 19 configure the circuit such that current from the 12-volt powerDocket No.: 648-1-1 PC source is directed through the seat mat 10 associated with the seat bottom 4. The current is routed through a designated connection point within the electronic control unit (ECU) 5 before continuing through the seat mat 10 associated with the seat back 2 and ultimately returning to ground. This closed loop forms the active heating circuit.

[0072] During heating operation, the circuit typically carries a current load ranging from approximately 4 amperes to 10 amperes, depending on factors such as seat design, conductor material, and desired heating intensity. The FETs 19 are biased into a conductive state to support low-resistance current flow while maintaining circuit stability and minimizing thermal losses.

[0073] Importantly, while the heating mode is active, the transmit (Tx) and receive (Rx) monitoring nodes of the CDS 100 remain electrically connected to the circuit. This configuration allows the system to maintain readiness for sensing operations and to optionally capture baseline electrical characteristics of the conductors during heating. These baseline measurements can later be used for calibration, drift compensation, or noise characterization when the system transitions into sensing mode.

[0074] Fig. 7 illustrates the electrical behavior of the ODS 100 when the heater is active. In this operational state, the sensing circuitry is configured to present a very high input impedance relative to the heating circuit. As a result, the sensing path is effectively isolated from the high currents flowing through the heater conductors. Any leakage currents into the sensing circuit are negligible, typically in the nanoampere to microampere range, and therefore have no measurable impact on either heating performance or sensing circuit stability.

[0075] The primary current pathway during this mode is confined to the heating elements of the seat mat 10, which operate as though the sensing circuit were not present. The high-impedance state ensures that the sensing nodes remain electrically connected but do not load or distort the heating current. This arrangement provides electrical transparency between the heating and sensing subsystems, allowing the heater to deliver its designed power output without interference while keeping the sensing system poised for rapid activation when the ECU initiates a sensing cycle.

[0076] Fig. 8 illustrates the sensing operation of the occupant detection system (ODS) 100. In this mode, pulse-width modulation (PWM) transmit frequencies generated by the ECU are applied to the conductive material of the seat mat. In theDocket No.: 648-1-1 PC embodiment shown, conductor 1 , located within the seat bottom 4, serves as the excitation pathway. The applied PWM signals stimulate the conductor to create an electromagnetic field whose interaction with the occupant and surrounding environment alters the impedance characteristics of the circuit.

[0077] Three monitoring pathways are employed to capture these variations. The first monitoring point is located before the transmit inductor 12 (TxD), the second is located after the transmit inductor 12 (TxL), and the third is positioned at the seat back wiring (Rx2). Each of these nodes provides a unique view of the system’s impedance response. By observing all three locations, the ODS 100 is able to detect not only the presence of an occupant but also classify the occupant based on distinct electrical signatures.

[0078] Signals from these nodes are received by receivers 16, which in this embodiment are implemented as operational amplifier (op-amp) receivers. The received signals may then be digitized using an analog-to-digital (A / D) converter 9 for further computational analysis. In the embodiment shown across Figs. 5-6 and 8-10, three receivers 16 are employed, each connected to one of the designated sensing points. This distributed monitoring arrangement enhances accuracy, redundancy, and noise rejection by ensuring that impedance variations are captured from multiple perspectives within the circuit topology.

[0079] Fig. 9 illustrates the operation of field-effect transistors (FETs) 19 during the sensing mode of the occupant detection system (ODS) 100. In this configuration, the FETs 19 are biased into a non-conductive state to disconnect the 12-volt power source from the heating circuit. This action effectively opens the current path that normally drives heating through the seat bottom 4 and seat back 2 conductors. By isolating the heater wiring in this manner, the FETs 19 prevent high-current heating flows from coupling into the sensing circuitry.

[0080] This electrical isolation ensures that impedance measurements are performed under controlled, low-current conditions without interference from residual heating currents. Because the sensing process is highly sensitive to small variations in impedance — often influenced by occupant presence, posture, or objects on the seat — any parasitic current from the heating supply could distort measurements or mask subtle signal changes. By maintaining a high-impedance separation during sensing, the FETs 19 allow the conductors of the seat bottom 4 and seat back 2 toDocket No.: 648-1-1 PC function solely as sensing elements, thereby preserving signal fidelity and improving classification accuracy.

[0081] Fig. 10 demonstrates the effect of field-effect transistor (FET) isolation on the sensing functionality of the occupant detection system (ODS) 100. When the FETs are properly switched into a non-conductive state, the heater circuit presents a high impedance and effectively appears electrically absent from the perspective of the sensing path. In this configuration, the seat conductors operate exclusively as sensing elements without interference from heating currents.

[0082] Although small leakage currents and parasitic capacitances may still be present, these effects are minimized through careful circuit design strategies, such as the use of low-leakage FETs, optimized gate drive control, and filtering or shielding techniques. Such measures reduce the influence of parasitic effects and help preserve the integrity of the measured impedance signals.

[0083] This controlled transition between heating and sensing modes exemplifies the dual-function architecture of the ODS 100. By allowing a single conductor network to alternate between high-current heating and high-sensitivity sensing roles, the system achieves operational flexibility and efficiency while reducing component count, wiring complexity, and overall seat stack thickness.

[0084] Referring now to Fig. 11 , an embodiment of the occupant detection system (ODS) 100 is shown implemented within a seat heater control system. In this embodiment, processing functions are integrated into a Cortex-based System-on-Chip (SoC), rather than a conventional stand-alone electronic control unit (ECU). For illustrative purposes, the embodiment depicted in Fig. 11 utilizes a development platform in place of a dedicated automotive ECU. This approach demonstrates system functionality and allows for evaluation of computational and signal-processing features in a flexible environment.

[0085] The embodiment shown in Fig. 11 includes features that may be optional in a production system. By way of example, the development platform integrates additional sensing elements such as an inertial measurement unit (IMU) and audio sensors. These auxiliary components may or may not be implemented in commercial deployments, depending on application requirements. However, the inclusion of such devices highlights the adaptability of the system architecture to accommodate multimodal sensing. The core computational elements of the architecture remain centralDocket No.: 648-1-1 PC and applicable across implementations, regardless of whether optional sensors are employed.

[0086] The processing unit of this embodiment executes frequency-domain analysis for occupant detection and classification. In one configuration, the processor performs Fast Fourier Transforms (FFT) to decompose time-domain signals into their frequency components. Alternative frequency-processing methodologies may also be employed, such as Goertzel transformations, wavelet analysis, or other spectral estimation techniques, depending on performance and resource constraints. The system architecture thus provides flexibility in selecting the most efficient processing method for a given application. In the embodiment shown, the computational structure comprises a Cortex-A9 processor that handles general-purpose processing tasks, while FFT execution is accelerated through dedicated hardware blocks integrated within the SoC. This combination enables efficient, real-time signal analysis suitable for automotive occupant detection applications.

[0087] Fig. 12 illustrates a physical printed circuit board (PCB) that may be employed in embodiments of the occupant detection system (ODS) 100. The PCB includes a central processing element implemented as a Cortex-A9 processor, which coordinates computational tasks and system control. The board further incorporates interfaces for connection to additional sensors and peripheral circuits. The supporting integrated circuits on the PCB may consist of custom-designed devices, commercially available off-the-shelf components, or a combination of both, depending on cost, performance, and manufacturing considerations.

[0088] In one embodiment, frequency-domain processing such as Fast Fourier Transform (FFT) computation is executed using a dedicated application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA), which operates in conjunction with the Cortex-A9 processor. In another embodiment, the processing unit comprises a commercially available programmable device configured to function as a masked device, thereby mimicking the behavior of a fixed-function ASIC. This masked implementation ensures that once programmed, the device permanently executes FFT or other spectral analysis functions with high efficiency. In yet another embodiment, FFT execution logic is implemented in Verilog Register Transfer Level (RTL) code, specifically optimized for the ODS application. While FFT is used as an illustrative technique, the system is not limited to FFT-based analysis; alternativeDocket No.: 648-1-1 PC algorithms, including Goertzel filters, wavelet transforms, or other spectral estimation methods, may be substituted depending on system requirements.

[0089] Flexibility in algorithm selection is a key aspect of the ODS architecture. The system pipeline is adaptable to accommodate different frequency-processing methodologies, allowing tuning of complexity, speed, and computational efficiency for a given application. In certain embodiments, FFT computations may be fully integrated within the Cortex-A9 processor itself, demonstrating the adaptability of the architecture and reducing reliance on external hardware accelerators when computational loads are lower.

[0090] The system architecture further supports modularity and scalability, enabling optimizations tailored to production environments. For example, in large- scale manufacturing scenarios, the entire processing pipeline — including ARM-based processing cores and frequency-analysis algorithms — may be consolidated into a single ASIC. This approach reduces bill-of-material costs, improves processing efficiency, and enhances reliability by eliminating discrete components. Conversely, for prototyping or low-volume applications, FPGA- or SoC-based solutions may be employed to provide flexibility while maintaining core functionality. Such modularity ensures that the ODS 100 can be adapted across a wide spectrum of use cases, from development platforms to mass-production automotive systems.

[0091] Fig. 13 illustrates the elements that may be employed for system operation and the functionality of the respective elements in one embodiment of the occupant detection system (ODS) 100. The system includes a power management stage comprising supply, filtering, and protection circuits. These circuits provide transient voltage suppression, reverse-polarity protection, and power conditioning to ensure robust operation under automotive electrical environments. Multiple supply rails, such as regulated 5-volt and 12-volt lines, may be generated and distributed to support the requirements of digital logic, analog front-end circuits, and powerswitching components.

[0092] In one embodiment, the system further incorporates dedicated signal transmission and conditioning mechanisms to maintain stable interfacing with the sensing conductors. These mechanisms may include transmit signal generation, transmit filtering, and transmit amplification stages that prepare and deliver excitation signals to the sensing elements. On the receive side, the system may include receiveDocket No.: 648-1-1 PC filtering, receive amplification, and signal conditioning circuits designed to preserve low-level sensing signals in the presence of electrical noise or parasitic coupling. The conditioned receive signals are then routed to subsequent processing stages for analysis and interpretation.

[0093] In another embodiment, the architecture integrates a complete analog front-end (AFE) chain consisting of amplification, filtering, and analog-to-digital conversion (ADC) stages. The amplification ensures that weak sensing signals are elevated to usable levels, filtering removes unwanted noise or harmonics, and the ADC converts the conditioned analog signals into digital form for further processing by the microcontroller, SoC, or ASIC. This layered approach to signal processing enhances accuracy, stability, and reliability of occupant detection and classification under varying operating conditions.

[0094] Fig. 14 provides a schematic representation of the signal path in one embodiment of the occupant detection system (CDS) 100. Frequency content signals are generated using pulse-width modulation (PWM) or equivalent signal-generation methods and are interfaced with the sensing conductors integrated into the seat structure. The response signals from the sensing element are routed through operational amplifiers (op-amps) for conditioning and amplification, after which they are digitized by a 12-bit analog-to-digital converter (ADC) operating at a sampling rate of approximately 500 kHz.

[0095] The schematic further illustrates the wiring connections within the signal path. The conditioned output from the op-amp is directly connected to the input of the ADC, thereby ensuring proper signal flow for digitization. Once digitized, the signals undergo frequency-domain transformations, such as Fast Fourier Transform (FFT) computations, to extract spectral features. These features are analyzed to determine occupant classification, presence, proximity, or other application-specific metrics. The FFT approach may be adapted to optimize memory utilization, computational efficiency, or implementation feasibility depending on the hardware platform.

[0096] In one embodiment, the system supports multiple computational topologies for FFT execution. For example, in-place FFT computation can be employed to minimize memory overhead in resource-constrained environments. The disclosed framework operates on an event-driven basis, wherein low-level tasks are executed in response to hardware events. Such tasks may include capturing analog-Docket No.: 648-1-1 PC to-digital data, transmitting collected information, aggregating signals into direct memory access (DMA) buffers, and structuring the acquired data for higher-level algorithmic processing.

[0097] The event-driven system is further designed to accommodate orthogonal frequency division (OFD) techniques. This enables the system to transmit and receive signals across multiple frequencies while maintaining synchronization with modem microcontroller units (MCUs). Such synchronization supports multiplexed sensing operations and enhances detection reliability in noisy or dynamic environments.

[0098] The occupant detection and classification (OD / OC) system employs both classical and advanced analysis methodologies. Classical techniques include FFT-based spectral analysis and Goertzel algorithms for narrowband detection. These may be complemented by heuristic rules and classification-based methods for posture recognition or object identification. In certain embodiments, machine learning algorithms are incorporated to further refine detection, classification, and postural analysis. Results are communicated to external systems via multiple communication media — such as CAN, LIN, or USB — depending on client or customer requirements.

[0099] Selection between Goertzel and FFT processing is determined by the number of channels under observation and computational efficiency considerations. In one embodiment, the processing pipeline follows a structured loop that includes: (i) receiving and capturing signals, (ii) performing sensing operations, (iii) acquiring and digitizing data, (iv) executing frequency-domain processing, (v) transmitting processed data packets, and (vi) compiling results for occupant detection and classification.

[0100] In one embodiment, the disclosed system operates at a “bare-metal” level, meaning execution occurs without the use of a real-time operating system (RTOS) or general-purpose operating system (such as Linux). This direct hardware interaction allows optimized, time-sensitive execution of frequency-analysis tasks without the latency overhead of additional software layers. However, it should be understood that, in alternative embodiments, an RTOS or higher-level operating system may be implemented on top of the hardware abstraction to support expanded features or system-level integration.

[0101] The integrated ADCs within the system are optimized for executing highspeed signal capture and computational tasks but are less efficient in managing highspeed peripheral interactions. To address this, the event-driven processingDocket No.: 648-1-1 PC methodology ensures deterministic execution of frequency analysis and data acquisition. Furthermore, the architecture supports alternative processing methods, including dedicated hardware accelerators, application-specific integrated circuits (ASICs), or FPGA-based implementations. Goertzel-based processing may also be used in scenarios where channel counts are limited and computational efficiency is prioritized.

[0102] System selection between Goertzel and FFT is therefore applicationspecific. For low-channel applications or cases where computational resources are constrained, the Goertzel algorithm provides a highly efficient solution. Conversely, for multi-channel applications or where hardware acceleration is available, FFT implementations are preferred, offering broader spectral coverage and faster execution. This flexibility ensures that the ODS 100 can be tailored to a variety of performance, cost, and integration requirements.

[0103] Referring to Fig. 15, illustrated are variations in peak values observed across different frequency bins during system operation. The figure demonstrates that the highest spectral peak alternates between different bins over time. These variations result from dynamic impedance changes within the sensing environment, such as occupant movement, posture adjustments, or the introduction of objects into the seat. Such changes cause frequency responses to shift, with the dominant peak frequently migrating by one, two, three, or more bins relative to its prior position.

[0104] Accurate tracking of the active peak value can involve continuously identifying the frequency bin that contains the highest magnitude at any given moment. The system does not rely on a fixed bin assignment — for example, permanently designating bin number five as the peak bin. Instead, the detection algorithm dynamically evaluates the spectral data in real time, selecting whichever bin currently exhibits the maximum amplitude. This adaptive approach ensures robust and accurate tracking of occupant-related impedance variations across the frequency spectrum, regardless of peak drift or bin migration.

[0105] Fig. 16 illustrates the data processing methodology across multiple frequencies and time intervals, highlighting the primary data inputs and transmission mechanisms of the occupant detection system (ODS) 100. The disclosed graph demonstrates a structured and computationally efficient approach to frequency-Docket No.: 648-1-1 PC domain analysis and signal processing, particularly suited for resource-constrained embedded environments.

[0106] Fig. 16 also presents a comparative analysis that expands on a subset of the frequency bins shown in Fig. 15. This zoomed-in perspective emphasizes the upper range of frequency variations and demonstrates that the dominant peak alternates between different signals over time. Under certain conditions, a third signal may also emerge as the leading peak, further illustrating the dynamic nature of impedance-driven frequency responses.

[0107] The figure further depicts the concept of peak tracking. In particular, the RX2 peak represents the highest observed signal across time. When examining the top five or six bins associated with RX2, it becomes evident that the dominant peak migrates between different bins rather than remaining confined to a single frequency. This fluctuation confirms that the peak value dynamically shifts within the frequency spectrum as impedance conditions evolve.

[0108] The data in Fig. 16 were collected across a wide temperature range, from approximately -40 °C to +85 °C, as well as under controlled room -temperature conditions. This comprehensive dataset validates that peak frequency-bin variation is attributable not only to occupant- and object-induced impedance changes but also to environmental factors such as temperature drift. The tracking algorithm ensures that, at any given instant, the highest peak value is recorded regardless of its bin location, thereby maintaining robustness against environmental and system variations.

[0109] As further shown in Fig. 15, the system acquires data through a frequency sweep, with each sweep encompassing numerous discrete frequency bins. The processing algorithm identifies the maximum value from each sweep, independent of which bin the maximum originates from. By focusing on peak magnitude rather than fixed bin assignment, the algorithm guarantees reliable peak tracking despite variations in frequency response.

[0110] In Fig. 16, the time-series representation of peak-bin selection is illustrated. This depiction demonstrates that at each time interval, the system identifies the bin with the highest magnitude across the sweep. Peak tracking is therefore independent of bin number or frequency index, and instead consistently reflects the most significant spectral response observed at any given time.Docket No.: 648-1-1 PC

[0111] The TxD peak value shown in Fig. 16 is particularly useful for temperature-compensation analysis. Surrounding “skirt” bins of the TxD peak exhibit relatively stable trends, providing reference points for distinguishing true impedance- driven variations from environmental or thermal fluctuations. These skirt bins serve as a baseline, enabling the system to filter out transient or temperature-related drift. The trace in Fig. 16 further demonstrates that the presence of an external object, such as a seat occupant, produces a measurable shift in peak values. While the TxD base — representing the skirt region of the TxD peak — remains stable, the displacement of the dominant peak highlights occupant-induced impedance effects, thereby confirming the system’s ability to discriminate between environmental noise and true occupancy events.

[0112] Fig. 17 illustrates the effect of reference bins on temperaturecompensation strategies within the occupant detection system (ODS) 100. By leveraging skirt bins — those frequency bins located adjacent to the dominant peak — the system can mitigate the influence of temperature-induced fluctuations and maintain a stable frequency response. In particular, the RX2 base and TXL base signals serve as reference points for this compensation process. Without correction, the trace exhibits undesirable shifts in frequency response as temperature varies. Through the application of skirt-bin compensation, the trace is effectively stabilized, aligning the response with the baseline and improving system accuracy under variable thermal conditions.

[0113] Fig. 17 further demonstrates the role of baseline correction in signal stabilization. In this embodiment, the TXL reference bin functions as a correction factor for the sensed signal. The algorithm applies the reference data derived from this bin to normalize deviations across the frequency spectrum, ensuring that the processed output remains within an acceptable operational range. This approach enables the ODS 100 to differentiate between impedance variations caused by environmental drift and those attributable to occupant presence, thereby enhancing detection reliability.

[0114] Figs. 15-17 collectively depict frequency-sweep data collected during real-time occupancy detection. As shown, the amplitude and frequency “fingerprint” of the system changes dynamically as objects or occupants enter and exit the detection zone. Each frequency sweep, which in one embodiment comprises approximately 60 frequency bins, provides a comprehensive snapshot of the system’s impedanceDocket No.: 648-1-1 PC behavior at that moment in time. However, it should be understood that the number of bins may vary depending on system design. A greater number of bins can provide finer resolution and a more detailed overview of system behavior, while fewer bins may reduce computational requirements and support cost-sensitive implementations.

[0115] In one embodiment, the occupant detection system (ODS) 100 continuously monitors frequency sweeps over time to characterize the impedance environment of the seat conductors. The ODS 100 differentiates between transient variations — such as electrical noise or short-term disturbances — and sustained changes in peak values that are indicative of occupant presence or posture. This filtering ensures that the peak-tracking mechanism maintains accuracy and reliability even in highly dynamic environments.

[0116] The advanced peak-tracking methodology adapts to impedance fluctuations caused by occupant interaction as well as to temperature-induced variations in circuit behavior. To improve stability, the system incorporates reference bins and skirt bins, which act as compensating factors for drift and environmental noise. This approach enhances robustness for real-time signal analysis by normalizing data across operating conditions. By analyzing the entire frequency spectrum, the system identifies and processes the frequency bin exhibiting the maximum peak magnitude at each sweep.

[0117] Once peak data is obtained, the process is repeated across successive time samples. Through this iterative approach, the ODS 100 builds a comprehensive temporal representation of peak magnitudes for the receive (Rx), transmit drive (TxD), and transmit inductor (TxL) nodes. In addition to identifying the dominant peak, the system captures surrounding bins located above and below the peak frequency. Tracking this local neighborhood of bins ensures accurate data acquisition and provides additional information for occupant detection and classification.

[0118] Peak detection begins with a complete frequency sweep across all available bins, from which the system identifies the initial peak bin. Once the initial bin is established, subsequent sweeps dynamically track peak location and magnitude. In certain implementations, the system further performs summation of bin values across a defined range around the peak, creating a composite measure of peak strength. While this methodology is applied here to occupant detection, the underlying sensorDocket No.: 648-1-1 PC operation — dynamic impedance monitoring through spectral peak analysis — forms the basis for performing classification and detection functions.

[0119] The ODS 100 captures peak magnitude data from three principal sensing nodes: Seat Back Rx, Tx Drive (TxD), and Tx Inductor (TxL). For each node, the system monitors the maximum bin magnitude and tracks N adjacent bins above and below the identified peak. The highest magnitude bin within this neighborhood is selected as the peak bin for subsequent raw-data capture. This adaptive approach allows the system to follow peak migration caused by impedance changes over time, ensuring continuous alignment with the dominant spectral response.

[0120] Identification of the initial bin for Seat Back Rx, TxD, and TxL is achieved by sweeping all bins and selecting the bin with the greatest amplitude. Thereafter, the system tracks peak SUM data by aggregating N bins above and below the peak. To account for environmental effects such as temperature variation, peak or peak SUM magnitudes are compensated using skirt bins. Skirt bins are defined as bins located outside the immediate vicinity of the peak, typically more than 16 bins away, though in some cases they may be as close as ±1 bin from the peak. The behavior of these skirt bins provides additional reference information regarding the seat environment and may be leveraged to distinguish true occupant-related impedance variations from environmental drift.

[0121] In one embodiment, one or several skirt bins may be employed for data processing. Calculations may involve direct addition or subtraction of selected skirt bin values, ratios of skirt bin values, or other mathematical relationships relative to the Seat Back Rx peak magnitude. Various combinations of values can be utilized to generate information for occupant detection and classification. This information may be correlated with other measured data to enhance prediction accuracy and occupant position determination.

[0122] For example, Seat Back Rx2 peak magnitude in combination with Tx Inductor bin 1 may provide a measurement indicative of occupant presence or classification. In another embodiment, Seat Back Rx2 peak magnitude combined with the ratio of Seat Back Rx2 peak magnitude to Seat Back Rx2 skirt bin provides a measurement useful for occupant determination. In yet another embodiment, Seat Back Rx2 peak magnitude adjusted with a lookup table value, as a function of the ratio of Tx Drive peak to Tx Drive bin 1 , provides a classification result. These examplesDocket No.: 648-1-1 PC illustrate that peak values, ratios, and lookup-based adjustments can be selectively combined to derive occupant detection outputs.

[0123] In one embodiment, Seat Back Rx, Tx Drive, and Tx Inductor peak or peak SUM magnitudes are temperature compensated through the use of a temperature sensor associated with ECU 5. The temperature sensor may be an on- chip microcontroller (MCU) temperature sensor, whose readings are applied through linear equations, piecewise linear equations, lookup tables, or other mathematical models to correct the raw Seat Back Rx, Tx Drive, and Tx Inductor values. After temperature compensation, adult / child occupancy classification is determined using these adjusted magnitudes.

[0124] The system may also detect fault conditions such as open circuits or short circuits in the wiring connections. When such conditions occur, abnormal or excessive data results are observed at one or more of the Seat Back Rx, Tx Drive, and Tx Inductor sensing locations. In one embodiment, fault scenarios are identified by comparing measurements against predefined thresholds. Exceeding these thresholds indicates a potential open, short, or other fault condition requiring corrective action or system notification.

[0125] Heater activation impacts the sensing data, producing measurable effects at Seat Back Rx, Tx Drive, and Tx Inductor sensing points. In one embodiment, these heater-induced effects are removed by applying correction values directly to the sensing data, either as fixed offsets or through a thermal time constant compensation curve. The correction values may also be temperature-adjusted using ECU 5 sensor data applied via linear equations, piecewise linear functions, lookup tables, or other mathematical models.

[0126] In one embodiment, a correction value of 200 units is directly added or subtracted when the heater is activated. For example, the correction may be expressed as 200 units + F(ECU Temp), where the function F(ECU Temp) represents a temperature-dependent adjustment. In another embodiment, a thermal time constant correction is applied, gradually transitioning from 0 to the peak correction value (200 units + F(ECU Temp)) when the heater is activated, and from 200 units + F(ECU Temp) back to 0 when the heater is deactivated. Example equations are provided below:Docket No.: 648-1-1 PC

[0127] Value(Heater On(tO), ECU Temp) = Value(last sample) + [ (200 unit + F(ECU Temp)) * (1 - e(-t / T))].

[0128] Value(Heater Off(tO), ECU Temp) = Value(last sample) + [ (200 unit + F(ECU Temp)) * e(-t / T)].

[0129] Heater activation and deactivation sequences require that the prior timeconstant correction value be used as the starting point for subsequent decay or accumulation curves. This ensures smooth transitions between heating states without introducing discontinuities into the sensing data. In certain embodiments, heater activation may exhibit a delayed interaction with the sensing locations, creating transient artifacts. Such delayed impacts can be mitigated by applying a time-constant function to the additive or subtractive correction values, thereby gradually compensating for heater-induced disturbances.

[0130] The mathematical operations described herein form the basis of the occupant detection process. These operations enable the system to determine whether a seat is occupied or unoccupied under varying environmental and operational conditions. Once magnitude and phase data are captured from the sensing conductors, they undergo spectral processing. The resulting processed data are then input into the detection algorithm, which applies classification and decision logic to generate an occupancy determination.

[0131] The methodology of the occupant detection system further addresses temperature compensation by distinguishing between two primary sources of variation: ambient temperature changes and seat heater activation. Each source of variation introduces unique effects into the sensing data. Accordingly, different compensation techniques are selectively applied depending on whether the seat heater is engaged, ensuring that both environmental and operational influences are appropriately corrected.

[0132] Sensing locations are stimulated through signals originating from the Tx Drive and Tx Inductor nodes. The Tx Drive signals sweep across a defined frequency range composed of multiple frequency bins. The Rx locations — such as the Seat Back, Tx Drive, and Tx Inductor — capture responses across these bins. Spectral processing is then applied to extract in-phase / quadrature (l / Q) data as well as magnitude and phase information for each Tx frequency. For example, a transmit frequency at X may be processed across a range from X - 200 kHz to X + 300 kHz. In one embodiment,Docket No.: 648-1-1 PC spectral processing is implemented using a Fast Fourier Transform (FFT) to produce l / Q and magnitude / phase outputs. In another embodiment, a Goertzel algorithm is employed to generate magnitude and phase data with reduced computational complexity.

[0133] Heating operation is achieved by activating all FETs 19, thereby allowing currents of approximately 6-12 amperes to flow through the seat conductors, as shown in Fig. 7. In contrast, sensing operation is performed by switching the FETs 19 to a non-conductive state and driving the seat conductors with a specified transmit frequency. Data are captured across the designated frequency range during this transmission window. In some embodiments, sensing may be delayed briefly after FET deactivation to allow residual currents to dissipate. Additionally, in certain embodiments, heating may be automatically disabled if the seat temperature exceeds a predefined safety threshold.

[0134] In another embodiment, the system may operate exclusively in sensing mode without integrated heating functionality. In such a configuration, the ECU 5 may omit temperature compensation circuitry, and FETs 19 would not be required to toggle between heating and sensing states. Similarly, heater-related compensation algorithms would not be implemented. This embodiment provides a simplified architecture for applications where heating is unnecessary but occupant detection remains critical.

[0135] In yet another embodiment, sensing may be performed using an inductive element incorporated into the receive antenna (conductor) path. The inductor may be connected in parallel with the antenna conductor, in series with the antenna conductor, or in other configurations combining passive or active components. Such arrangements allow the system to tailor impedance characteristics of the receive path to enhance sensitivity, improve selectivity, or provide noise rejection under specific operational conditions.

[0136] Figs. 18 and 19 introduce an alternative ODS 200 wherein the ODS 200 operates using a sensing-only approach. In such an embodiment, heater compensation is not required, as the system does not incorporate a heating element. Instead, conductive material alone is utilized for occupant detection.

[0137] In an embodiment, the ODS 200 includes two transmitting conductors (antennas) 11 and 13, and two receiving conductors (antennas) 17 and 29. However,Docket No.: 648-1-1 PC it should be appreciated that the system is not limited to this configuration. Equivalent functionality can be achieved using a greater number of transmitting and / or receiving conductors. In some embodiments, a functional ODS may be realized with only a single transmitting conductor paired with a single receiving conductor. In yet another embodiment, occupant detection may be accomplished with only a transmitting conductor and without a dedicated receiving conductor, relying on feedback and coupling effects for sensing..

[0138] A particularly advantageous configuration involves the TxD / TxL arrangement, wherein measurement is performed at the transmitter drive (TxD) 14 and the transmitter inductor (TxL) 12. Under certain conditions, this configuration has demonstrated improved performance compared to arrangements that employ additional receiving conductors, such as a secondary receiver (RX2).

[0139] Figure 20 schematically depicts a further embodiment in which the receiving side includes additional RX components equipped with receiver inductors 15. These inductors provide supplementary sensing points, thereby enhancing detection resolution and system robustness.

[0140] Figure 21 illustrates an example of a seat architecture in which the ODS can be implemented. As shown, a seat back 20 incorporates a single sensor conductor (wire). Data collected from the seat back 20 is transmitted to an electronic control unit (ECU) controller 25 for processing. A seat bottom 22 is also provided, in which a sensor stack 30 is integrated. The sensor stackup 30 comprises multiple layers, including: a trim cover 34, a heater / sensor wire layer 33 (also referred to as a conductor layer), and underlying seat foam 31 . The wire layer 33 is bonded to the foam 31 via an adhesive layer 32. This construction provides structural integration of the sensing conductor within the seat assembly while maintaining occupant comfort and durability.

[0141] Several insights that will be apparent to one of ordinary skill in the art in view of the foregoing are worth reiterating. First, a class of frequency-based sensors have heretofore been described as having a transmitter, a transmit conductor (antenna), a receiver, and a receive conductor (antenna). In the class of prior frequency-based sensors, spectral processing is performed on the signals received, and magnitude and / or phase data for each of those frequencies is placed in a plurality of corresponding bins. In an embodiment of the present invention, signals from theDocket No.: 648-1-1 PC transmit side locally provide information concerning the state of the sensor-- specifically, signals between the transmit amplifier and a transmit inductor, and / or signals between the transmit inductor and transmit conductor. The insight leading to the use of these signals is that it appears the effect of a sensed object not only alters signals as they are received on a receive antenna, but it also affects and thus alters signals on the transmit side. Moreover, such an effect may be measurable at various points between the amplifier and the transmit conductor. The placement of an electronic component (e.g., inductor, or a capacitor or resistor) causes the measurable effect to differ on the transmit side--thus, in an embodiment, the sensor gathers signal from: (i) between the transmit amplifier and an inductor (TxD); (ii) between the inductor and a conductor (TxL); and (iii) on the receive side (Rx). Any one or two of these signals may provide sufficient information for sensing. In an embodiment of a seat sensor combined with a seat heater--where each is run for a portion of the time--the combination of all three provide substantial data from which changes in the sensed space may be realized.

[0142] Separately, as is frequently done in spectral processing for the prior class of sensors, a peak bin is identified and used. Another insight of the work leading to the inventions described and claimed herein is that the peak may change based on a variety of factors, including, e.g., heat (which is especially a concern in the combined heater / sensor described). The tracking of the peak bin, rather than assigning of the peak bin provides a robust system. In an embodiment, the system requires no ongoing calibration. In an embodiment, the sensor requires less calibration. In an embodiment, the tracking of the peak bin allows self-calibration for certain environmental changes (e.g., heat).

[0143] Turning to Figs. 22-32, shown are alternative embodiments of occupancy detection systems that can be implemented in vehicle seats. Figure 22, for example, depicts an ODS including a seat back sensor 40 having two receive conductors integrated with a heater mat. A heater mat controller 41 is also provided for regulating heater operation. Further shown is an orthogonal frequency division (OFD) controller 43, which includes both a transmit analog front end and a receive analog front end for system signal processing. Additionally, a seat bottom sensor 42 is depicted, the seat bottom sensor incorporating two transmit conductors.Docket No.: 648-1-1 PC

[0144] Figure 23 illustrates a cross-sectional view of an occupant detection system embodiment incorporating both receiving conductors (antennas) and transmitting conductors (antennas). The seat back foam 40 is shown, and positioned above the foam are successive layers including a felt layer 48 and an adhesive layer 44. Affixed to these layers are a heater wire 47 and a set of receiving conductors 49. In the embodiment depicted, the receiving conductors 49 are physically distinct from, and not integrated with, the heater wire 47. This separation can be advantageous in reducing electrical interference between heating functions and occupant sensing functions, thereby improving the reliability of the detection signal.

[0145] Also illustrated is the seat bottom foam 42. Above the seat bottom foam 42 are corresponding layers of felt 48 and adhesive 44, to which a heater wire 47 and transmitting conductors 46 are attached. In this configuration, the transmitting conductors 49 are associated with the seat bottom foam 42, while the receiving conductors 49 are associated with the seat back foam 40. This orientation allows the transmitted signals from the seat bottom to be captured by the receiving conductors in the seat back, providing cross-sectional coverage that enhances occupant detection sensitivity.

[0146] It should be appreciated that the arrangement of transmitting and receiving conductors is not limited to the configuration shown. In alternative embodiments, the transmitting conductors 46 may be positioned within the seat back foam 40 while the receiving conductors 49 are disposed within the seat bottom foam 42, or vice versa. By varying conductor placement between the seat bottom and seat back, the system designer may optimize electric field distribution, minimize noise coupling from heater wires, and tailor the sensing profile to specific seat geometries and materials. Such flexibility enables robust occupant detection across a range of vehicle seating designs while maintaining thermal comfort provided by the heater wire layer.

[0147] Fig. 24 illustrates a diagram of an embodiment of an occupant detection system (ODS). In this embodiment, a heater mat is provided which incorporates a receiving conductor 59 positioned within the mat structure. The integration of the receiving conductor 59 into the heater mat allows the system to simultaneously provide occupant sensing and thermal comfort functions without requiring separate physical layers, thereby reducing overall seat stack thickness and simplifying assembly.Docket No.: 648-1-1 PC

[0148] The system further includes a heater mat controller 51 , which regulates the operation of the heater elements to ensure consistent occupant comfort and thermal safety. An orthogonal frequency division (OFD) controller 53 is also provided. The OFD controller 53 includes both transmit and receive analog front ends configured to manage the excitation of transmitting conductors and the acquisition of return signals from the receiving conductor 59. By employing an OFD architecture, the system can separate heater-related electrical activity from occupant detection signals, thereby mitigating interference and improving the accuracy of detection.

[0149] Also shown in Figure 24 is a seat bottom sensor 52. The seat bottom sensor 52 provides an additional sensing region, enabling cross-referencing of signals from both the heater-integrated receiving conductor 59 and the independent seat bottom sensor. This multi-zone arrangement enhances detection reliability by creating redundant signal paths and improving discrimination between different occupant states, such as distinguishing between a child seat, a lightweight adult, or inanimate objects.

[0150] By integrating sensing functionality directly into the heater mat, this embodiment achieves a compact and efficient design that maintains comfort features while ensuring compliance with safety regulations requiring accurate occupant classification.

[0151] Figure 25 illustrates a cross-sectional view of an embodiment of an occupant detection system (ODS) incorporating heater wires 57 in combination with dedicated sensing conductors. In this configuration, receiving conductors 59 and transmitting conductors 56 are positioned in close proximity to the heater wires 57. The adjacent placement enables the system to share physical layers within the seat architecture, thereby minimizing packaging complexity while maintaining separation of functions to reduce electrical interference.

[0152] The heater wires 57, transmitting conductors 56, and receiving conductors 59 are supported on a felt layer 54, which provides a stable substrate and an intermediate cushion between the conductors and the underlying seat foams. The felt layer 54 also assists in thermal distribution from the heater wires while protecting the conductors from mechanical abrasion during seat use.

[0153] As shown, these functional layers are disposed above seat back foam 50 and seat bottom foam 52. This arrangement allows for integration of occupantDocket No.: 648-1-1 PC detection sensing elements into both the seat back and the seat bottom, thereby creating a distributed sensing field. Such distribution improves system performance by enabling cross-sectional signal coupling between transmitting and receiving conductors, enhancing detection sensitivity to occupant presence, weight, and position.

[0154] By co-locating sensing conductors adjacent to heater wires while maintaining dielectric separation through the felt 54, the design achieves efficient use of seat real estate without compromising signal integrity. This embodiment illustrates a compact and manufacturable seat architecture that combines heating and sensing layers into a unified structure optimized for both comfort and safety compliance.

[0155] Fig. 26 illustrates a diagram of an embodiment of an occupant detection system (ODS). In this embodiment, the ODS employs two transmitting conductors and one receiving conductor. The system is configured to detect the presence of front and rear passengers — including infants, children, pets, and adults — through 16 Hz simultaneous sampling. The ODS enables in-air proximity detection of up to approximately 180 cm and is capable of penetrating child seats to confirm occupant contact. This sensing capability can also be integrated with steering wheel sensors for frequency-based driver hand detection and with console-mounted frequency identification modules for occupant identification.

[0147] The system further incorporates a seat back sensor 60 embedded within the heater mat, which includes a receiving conductor. A heater driver 61 is electrically coupled to a seat bottom sensor 62 comprising transmitting conductors. The integration of receiving and transmitting conductors into the seat back sensor 60 and the seat bottom sensor 62 within the heater mat allows the ODS to simultaneously provide both occupant detection and thermal comfort functions. This dual functionality eliminates the need for separate sensor layers, thereby reducing seat stack thickness, simplifying assembly, and improving manufacturability.

[0148] The ODS additionally includes a heater driver 61 comprising both the heater control and an occupant frequency detection (OFD) controller. The heater control regulates operation of the heating elements to maintain consistent passenger comfort and ensure thermal safety. The OFD controller includes transmit and receive analog front ends configured to excite the transmitting conductors and acquire return signals from the receiving conductor. By employing an OFD-based architecture, the systemDocket No.: 648-1-1 PC separates heater-related electrical activity from occupant detection signals, mitigating interference and enhancing detection accuracy.

[0156] Fig. 27 is a diagram of an embodiment of an ODS. In this embodiment, the ODS employs two transmitting conductors and two receiving conductors. The system is configured to detect the presence of front and rear passengers, including infants, children, pets, and adults, through 16 Hz simultaneous sampling. The ODS enables in-air proximity detection of up to approximately 180 cm and is capable of penetrating child seats to confirm occupant contact. In an embodiment greater than 180 cm distances can be detected. This sensing capability can also be integrated with steering wheel sensors for frequency-based driver hand detection and with consolemounted frequency identification modules for occupant identification.

[0147] The system further incorporates a seat back sensor 70 embedded within the heater mat, which include the receiving conductors. A heater driver 71 is electrically coupled to a seat bottom sensor 72 comprising transmitting conductors. The integration of receiving and transmitting conductors into the seat back sensor 70 and the seat bottom sensor 72 within the heater mat allows the ODS to simultaneously provide both occupant detection and thermal comfort functions. This dual functionality eliminates the need for separate sensor layers, thereby reducing seat stack thickness, simplifying assembly, and improving manufacturability.

[0148] The ODS additionally includes a heater driver 71 comprising both the heater control and an occupant frequency detection (OFD) controller. The heater control regulates operation of the heating elements to maintain consistent passenger comfort and ensure thermal safety. The OFD controller includes transmit and receive analog front ends configured to excite the transmitting conductors and acquire return signals from the receiving conductor. By employing an OFD-based architecture, the system separates heater-related electrical activity from occupant detection signals, mitigating interference and enhancing detection accuracy.

[0157] Fig. 28 is a diagram of another embodiment of an ODS with multiple sensors embedded therein. The ODS can perform an occupant classification via 16 Hz simultaneous sampling of the body in-air, deformation, and contact. The occupant classification can implement 16 Hz sampling, however sampling at greater, or less frequency can also be performed depending on the desired detail of sampling with greater frequency resulting and more frequent determination of the sensingDocket No.: 648-1-1 PC information and therefore the ability to determine relevant information regarding an occupant. The ODS can sense body pose, body contour, body deformation of seat surface, relation to thermal transfer, in-air proximity up to 30 cm, height and weight. The in-air proximity can be paired to the sensors in the steering wheel in order to provide additional information regarding the passenger.

[0158] The ODS in Fig. 28 has a heater driver 81 comprising both the heater control and an occupant frequency detection (OFD) controller. The heater control regulates operation of the heating elements to maintain consistent passenger comfort and ensure thermal safety. The OFD controller includes transmit and receive analog front ends configured to excite the transmitting conductors and acquire return signals from the receiving conductors. By employing an OFD-based architecture, the system separates heater-related electrical activity from occupant detection signals, mitigating interference and enhancing detection accuracy.

[0159] The heater mat 82 in the embodiment shown in Fig. 28 has two headrest conductors, 22 seat back and bottom conductors, and 8 seat bolster conductors. It should be understood that more or less conductors can be implemented depending on the desired detail of the sensing. It should be further understood that the conductors can be dedicated transmitting conductors or dedicated receiving conductors or be able to function as both transmitting and receiving conductors.

[0160] FIG. 29 shows a diagram of conductors 93, 94 embedded in a vehicle seat and a close-up view of the conductors 93, 94 in the seat. There is reinforcement stitching over the conductors 93, 94 at those locations where they cross.

[0161] FIG. 30 shows a cross-sectional view of an occupant detection system embodiment incorporating both receiving conductors 109 and transmitting conductors 106. The seat back foam 101 is shown and positioned above the seat back foam 101 are successive layers including a felt layer 108 and an adhesive layer 104. Affixed to these layers are a heater wire 107 and a set of receiving conductors 109. In the embodiment depicted, the receiving conductors 109 are physically distinct from, and not integrated with, the heater wire 107. This separation can be advantageous in reducing electrical interference between heating functions and occupant sensing functions, thereby improving the reliability of the detection signal.

[0162] Also illustrated is the seat bottom foam 102. Above the seat bottom foam 102 are corresponding layers of felt 108 and adhesive 104, to which a heater wire 107Docket No.: 648-1-1 PC and transmitting conductors 109 are attached. In this configuration, the transmitting conductors 106 are associated with the seat bottom foam 102, while the receiving conductors 109 are associated with the seat back foam 101. This orientation allows the transmitted signals from the seat bottom to be captured by the receiving conductors 109 in the seat back, providing cross-sectional coverage that enhances occupant detection sensitivity.

[0163] It should be appreciated that the arrangement of transmitting conductors 106 and receiving conductors 109 is not limited to the configuration shown. In alternative embodiments, the transmitting conductors 106 may be positioned within the seat back foam 101 while the receiving conductors 109 are disposed within the seat bottom foam 102, or vice versa. By varying conductor placement between the seat bottom and seat back, the system designer may optimize electric field distribution, minimize noise coupling from heater wires, and tailor the sensing profile to specific seat geometries and materials. Such flexibility enables robust occupant detection across a range of vehicle seating designs while maintaining thermal comfort provided by the heater wire layer.

[0164] FIG. 31 shows a cross-sectional view of a car seat and placement of conductors using a dual function conductor with dual zones. This is accomplished by using four conductors, two receiving conductors 119 and two transmitting conductors 116. Fig. 31 shows a cross-sectional view of an occupant detection system embodiment incorporating both receiving conductors 119 and transmitting conductors 116. The seat back foam 110 is shown. Positioned above the seat back foam 110 are successive layers including a felt layer 118 and an adhesive layer 1 14. Affixed to these layers are dual purpose transmitting conductors 116 that function as both transmitting and heating conductors.

[0165] Also illustrated is the seat bottom foam 112. Above the seat bottom foam 112 are corresponding layers of felt 118 and adhesive 114, to which a dual-purpose receiving conductor 119 is fixed that functions as both receiving conductors and heating conductor.

[0166] It should be appreciated that the arrangement of transmitting conductors 116 and receiving conductors 119 is not limited to the configuration shown. In alternative embodiments, the transmitting conductors 116 may be positioned within the seat back foam 111 while the receiving conductors 119 are disposed within theDocket No.: 648-1-1 PC seat bottom foam 112, or vice versa. By varying conductor placement between the seat bottom and seat back, the system designer may optimize electric field distribution, minimize noise coupling from heater wires, and tailor the sensing profile to specific seat geometries and materials. Such flexibility enables robust occupant detection across a range of vehicle seating designs while maintaining thermal comfort provided by the heater wire layer.

[0167] FIG. 32 shows a cross-sectional view of a car seat and placement of conductors using a dual function conductor with a single zone. This is accomplished by using two conductors, a receiving conductor 129 and one transmitting conductors 126. Fig. 32 shows a cross-sectional view of an occupant detection system embodiment incorporating both a receiving conductor 129 and a transmitting conductor 126. The seat back foam 120 is shown. Positioned above the seat back foam 120 are successive layers including a felt layer 128 and an adhesive layer 124. Affixed to these layers is a dual-purpose transmitting conductor 126 that functions as both transmitting and heating conductors.

[0168] Also illustrated is the seat bottom foam 122. Above the seat bottom foam 122 are corresponding layers of felt 128 and adhesive 124, to which a dual-purpose receiving conductor 129 is fixed that functions as both a receiving conductor and heating conductor.

[0169] It should be appreciated that the arrangement of transmitting conductors 126 and receiving conductors 129 is not limited to the configuration shown. In alternative embodiments, the transmitting conductors 126 may be positioned within the seat back foam 121 while the receiving conductors 129 are disposed within the seat bottom foam 122, or vice versa. By varying conductor placement between the seat bottom and seat back, the system designer may optimize electric field distribution, minimize noise coupling from heater wires, and tailor the sensing profile to specific seat geometries and materials. Such flexibility enables robust occupant detection across a range of vehicle seating designs while maintaining thermal comfort provided by the heater wire layer.

[0170] An aspect of the disclosure is an occupant sensing system operably connected to a vehicle seat, the occupant sensing system having a transmitter adapted to transmit a plurality of frequencies, the occupant sensing system comprising: transmit inductor operatively connected to the transmitter; a first seatDocket No.: 648-1-1 PC conductor and a second seat conductor; switching system having at least two modes, wherein in the first mode, the switching system connects the first seat conductor and the second seat conductor in series, and in the second mode, the switching system operatively connects one of the first seat conductor and the second seat conductor to the transmit inductor, and operatively connects the other of the first seat conductor and the second seat conductor to the first receiver; a first receiver operatively connected to the connection between the transmitter and the transmit inductor; a second receiver operatively connected to the connection between the transmit inductor and the at least one of the first seat conductor and the second seat conductor; a processing system that receives signals from the first receiver and the second receiver and based at least in part thereon determines the vehicle seat occupancy status.

[0171] Another aspect of the disclosure is a sensing system having a signal generator adapted to generate a plurality of frequencies and a transmit amplifier adapted to amplify the plurality of frequencies operatively connected to the signal generator, the sensing system comprising: transmit inductor having a connection to the transmit amplifier and a transmit conductor; a receiver operatively connected to connection between the transmit amplifier and the transmit inductor; a processing system that receives signals from the receiver and based at least in part on those signals determines a sensor status.

[0172] Still yet another aspect of the disclosure is a sensing system having a signal generator adapted to generate a plurality of frequencies and a transmit amplifier adapted to amplify the plurality of frequencies operatively connected to the signal generator, the sensing system comprising: transmit inductor having a connection to the transmit amplifier and a transmit conductor; a receiver operatively connected to connection between the transmit inductor and the transmit conductor; a processing system that receives signals from the receiver and based at least in part on those signals determines a sensor status.

[0173] Another aspect of the disclosure is a sensing system, the sensing system having a signal generator adapted to generate a plurality of frequencies, and a transmit amplifier operatively connected to the signal generator, the transmit amplifier adapted to amplify the plurality of frequencies, the sensing system comprising: transmit inductor having a connection to the transmit amplifier and aDocket No.: 648-1-1 PC transmit conductor; a TxD receiver operatively connected to connection between the transmit inductor and the transmit amplifier; a TxL receiver operatively connected to connection between the transmit inductor and the transmit conductor; a processing system that receives signals from the TxD and TxL receivers and based at least in part on those signals determines a sensor status.

[0174] Still yet another aspect of the disclosure is a sensing system, the sensing system having a signal generator adapted to generate a plurality of frequencies, a transmit amplifier operatively connected to the signal generator, the transmit amplifier adapted to amplify the plurality of frequencies, and a first receiver operatively connected to a receive conductor, the sensing system comprising: transmit inductor having a connection to the transmit amplifier and to a transmit conductor; a second receiver operatively connected to the connection between one of: the transmit inductor and the transmit amplifier, or the transmit inductor and the transmit conductor; a processing system that receives signals from the first and second receiver and based at least in part on those signals determines a sensor status.

[0175] While the invention has been particularly shown and described with reference to an embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims

Docket No.: 648-1-1 PCCLAIMS1. An occupant sensing system operably connected to a vehicle seat, the occupant sensing system having a transmitter adapted to transmit a plurality of frequencies, the occupant sensing system comprising: transmit inductor operatively connected to the transmitter; a first seat conductor and a second seat conductor; switching system having at least two modes, wherein in the first mode, the switching system connects the first seat conductor and the second seat conductor in series, and in the second mode, the switching system operatively connects one of the first seat conductor and the second seat conductor to the transmit inductor, and operatively connects the other of the first seat conductor and the second seat conductor to the first receiver; a first receiver operatively connected to the connection between the transmitter and the transmit inductor; a second receiver operatively connected to the connection between the transmit inductor and the at least one of the first seat conductor and the second seat conductor; and a processing system that receives signals from the first receiver and the second receiver and based at least in part thereon determines the vehicle seat occupancy status.

2. The occupant sensing system of claim 1 , further comprising a third receiver operatively connected to at least one of the first seat conductor and the second seat conductor.

3. The occupant sensing system of claim 2, wherein the processing system determines the vehicle seat occupancy status based on signals received from the first receiver, the second receiver, and the third receiver.Docket No.: 648-1-1 PC4. The occupant sensing system of claim 1 , wherein the transmitter is adapted to transmit a plurality of frequency orthogonal signals.

5. The occupant sensing system of claim 4, wherein the processing system is adapted to identify a bin containing a current peak value for each receiver so that the peak value can be used without regard for the bin in which it exists.

6. The occupant sensing system of claim 5, wherein the processing system is adapted to scan for the bin where a peak value was identified to further determine information regarding an occupant.

7. The occupant sensing system of claim 6, wherein the processing system is adapted to use skirt bins when determining information regarding an occupant.

8. The occupant sensing system of claim 7, wherein measurements of the skirt bins are correlated with temperature to determine information regarding the occupant.

9. The occupant sensing system of claim 5, wherein the processing system is adapted to dynamically determine a bin with a peak value for each scan.

10. The occupant sensing system of claim 1 , wherein the transmitter is operatively connected to a transmit amplifier adapted to amplify the plurality of frequencies transmitted from the transmitter.

11. The occupant sensing system of claim 1 , further comprising field effect transistors.

12. The occupant sensing system of claim 11 , wherein the first seat conductor and the second seat conductor are further adapted to function as seat heaters.

13. The occupant sensing system of claim 12, further comprising a heater control.

14. The occupant sensing system of claim 13, wherein the field effect transistors switch the first seat conductor and the second conductor between the transmitter and the heater control.

15. The occupant sensing system of claim 1 , wherein the transmitter comprises a pulse width modulation circuit.Docket No.: 648-1-1 PC16. A sensing system having a signal generator adapted to generate a plurality of frequencies and a transmit amplifier adapted to amplify the plurality of frequencies operatively connected to the signal generator, the sensing system comprising: transmit inductor having a connection to the transmit amplifier and a transmit conductor; a receiver operatively connected to connection between the transmit amplifier and the transmit inductor; a processing system that receives signals from the receiver and based at least in part on those signals determines a sensor status.

17. The sensing system of claim 16, further comprising another receiver operatively connected to connection between the transmit inductor and a seat conductor.

18. The sensing system of claim 17, wherein the processing system receives signals from the another receiver and based at least in part on those signals determines the sensor status.

19. The sensing system of claim of claim 16, wherein the processing system is adapted to scan for the bin where a peak value was identified to further determine information regarding the occupant.

20. A sensing system having a signal generator adapted to generate a plurality of frequencies and a transmit amplifier adapted to amplify the plurality of frequencies operatively connected to the signal generator, the sensing system comprising: transmit inductor having a connection to the transmit amplifier and a transmit conductor; a receiver operatively connected to connection between the transmit inductor and the transmit conductor; a processing system that receives signals from the receiver and based at least in part on those signals determines a sensor status.

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