Abstract:
The capacitance of a shielded capacitive load cell (12, 32) is determined so as to minimize the effect of stray or parasitic capacitance between the load cell (12) and other objects including the shield (32). The load cell conductors are coupled across input and output terminals of an operational amplifier (46) that is tied to a reference voltage. A constant current is applied to the load cell (12), and the resulting rate of change in voltage at the amplifier output is measured as a representation of the load cell capacitance. In a vehicle seat sensor application including an electromagnetic interference shield (32) between the load cell (12) and the seating surface (18), the amplifier output is coupled to the load cell electrode furthest from the shield (32), the amplifier (46) maintains the other load cell electrode at a virtual reference voltage, and the shield (32) is tied to the reference voltage.
Abstract:
An occupant of a motor vehicle seat (10) is characterized for purposes of air bag suppression based on the seated weight of the occupant, the variation of the seated weight, and the occupant's apparent longitudinal center-of-mass. The method distinguishes between an adult and a child seat, distinguishes between forward-facing and rearward-facing child seats, and detects cinching of a child seat.
Abstract:
A seat frame-based occupant weight estimation load cell (20) transfers the seat force to a floor bracket (16) through a spherical ball (30) and a ball actuator (32). The ball (30) is in contact with the force sensor (28) and has minimal contact area with either the ball actuator (32) or the force sensor (28) so that the transfer of forces not functionally related to occupant weight is minimized. The ball actuator (32) is coupled to the seat frame (12), and a sensor bracket (34) aligns the ball actuator (32) with respect to the sensor (28). The sensor bracket (34) is domed to securely anchor the seat (10) to the floor bracket (16) in the event of an inverse overload. A spring (36) disposed between the ball actuator (32) and the dome of the sensor bracket (34) biases the ball (30) against the force sensor (28) to preload the force sensor (28) for enabling off-loading detection.
Abstract:
A dual-electrode occupant (12) detection system (10) configured to determine an occupant (12) presence on a seat assembly (32). The system (10) includes two electrodes (20, 28) that each generates an electric field in response to an applied excitation signal (50). The two electrode signals arising therefrom can be measured individually and/or combined to detect more reliably an occupant (12). Such a configuration advantageously avoids the added expense and complication of an electrode arrangement that relies on an underlying shield layer to reduce electrode signal (24) degradation caused by a seat heater element.
Abstract:
A circuit board (28) is inserted into an open-ended housing (10) and potting material (56) is dispensed onto the exposed face of the circuit board (28) in a single step to seal the circuit board (28) to the housing (10). One or more electrical interconnects such as a connector header (50) or a ribbon cable (42) attached to the circuit board (28) extend upward through the potting material (56) so that the potting material (56) also forms an environmental seal around the electrical interconnects (42/50).
Abstract:
A capacitive load cell (12) includes upper and lower capacitor plates (30, 28) and an intermediate array of dielectric pads (22a) formed of silicone-impregnated open-cell urethane foam (i.e., gel pads). The silicone essentially displaces air that would otherwise be trapped in the foam, contributing to a dielectric (22) having minimal humidity-related variability. The upper capacitor plate is defined by an array of individual charge plates (30), the lower capacitor plate defines a ground plane conductor (28) common to each of the charge plates (30), and the dielectric pads (22a) are disposed between the ground plane conductor (28) and each of the charge plates (30), leaving channels (32) between adjacent dielectric pads (22a). When occupant weight is applied to the seat (10), the dielectric pads (22a) transmitting the weight distend laterally into the channels (32) to reduce the separation between the respective upper and lower capacitor plates (30, 28), and the consequent change in capacitance is detected as a measure of the applied force and the force distribution (14).
Abstract:
A sealed electronic module includes a housing (10) having an open end for receiving a circuit board (26), and a slotted side wall (14) for receiving a connector header (34) mounted on the circuit board (26). The connector header (34) fits snugly in the side wall slot (32) and includes an integral trough (44) that engages the interior face of the side wall (14) to form a U-shaped channel that surrounds the sides and bottom of the slot (32). The housing (10) is positioned with its open end upward, and potting material (52) is dispensed onto the exposed surface of the circuit board (26) in a single step to seal the circuit board (26) to the housing (10). A portion of the potting material (52) flows into and fills the U-shaped channel to seal the connector header (34) to the housing (10).
Abstract:
The capacitance of a shielded capacitive load cell (12, 32) is determined so as to minimize the effect of stray or parasitic capacitance between the load cell (12) and other objects including the shield (32). The load cell conductors are coupled across input and output terminals of an operational amplifier (46) that is tied to a reference voltage. A constant current is applied to the load cell (12), and the resulting rate of change in voltage at the amplifier output is measured as a representation of the load cell capacitance. In a vehicle seat sensor application including an electromagnetic interference shield (32) between the load cell (12) and the seating surface (18), the amplifier output is coupled to the load cell electrode furthest from the shield (32), the amplifier (46) maintains the other load cell electrode at a virtual reference voltage, and the shield (32) is tied to the reference voltage.
Abstract:
A system (10), controller (20), and method (400) for detecting moisture on a windshield (12) that uses an isolated electrode (16) coupled to a windshield (12). The isolated electrode (16) is configured to exhibit an electrical impedance indicative of moisture present on a surface of the windshield (12). The controller (20) is configured to determine an electrode impedance value corresponding to the electrical impedance exhibited by the isolated electrode (16) for detecting moisture on the windshield (12). By using an isolated electrode (16), the system (10) is simpler and less expensive than other systems that have at least one electrode providing a return path for another electrode. Also, a way to use the isolated electrode (16) for both detecting moisture on the windshield (12), and heating the windshield (12) is described.
Abstract:
An occupant presence sensor apparatus (12) disposed in a seat (10) includes first and second substantially non-compliant force translation plates (22, 24) generally parallel to the seating surface (18) of the seat (10), an elastomeric mat (26) disposed between the first and second force translation plates (22, 24), and a switch mechanism (28) disposed between the first and second force translation plates (22, 24) within an opening (52) formed in the elastomeric mat (26). The elastomeric mat (26) includes a distributed array of hollow protuberances (50a, 50b) that extend toward and contact the force translation plates (22, 24), and the mat (26) has a stiffness that normally provides a clearance between the switch mechanism (28) and one of the force translation plates (22, 24). When an occupant of specified or higher weight sits on the seating surface (18), the protuberances (50a, 50b) collapse and the force translation plates (22, 24) activate the switch mechanism (28).