2019 Flexpoint Seat Occupancy & Belt Reminder Technology Application
Flexpoint developed this system for Intertek Industrial’s Protek ambulance system. Using an “A” surface and a “B” surface sensor depending on which seat or squad bench was utilized.
Flexpoint system would use for development a Bluetooth enabled PCB assembly
- Seat status would be reviewed live during testing and thresholds would be established for desired seat performance
- Firmware would then be updated with self-calibrating routines and established thresholds for production, no “trimming” resistors necessary would also compensate for the trim tensioning as well as wear of the seat itself.
- Production PCB assemblies would not have the Bluetooth populated on the board.
The Flexpoint system could be designed around venting and heating elements of the seat. Little will need to change in the existing designs to accommodate the Flexpoint Bend Sensor. Additional functionality can be integrated without significant cost to the sensor and PCB assembly including full OCS capability.
There are other solutions like SCHERDEL SBR Sensor which however must be placed in that way into the seat system that connectors, cables, metal brackets etc. are not impacting or interfering in the function. Flexpoint Bend Sensor is designed so that standard noise factors do not impact function.
Flexpoint Sensor is incorporated in the PROTEK System for Advanced Restraint Harness and Seat Sensor, both of which are monitored by a microprocessor in the Control Box. The Control Box connects to the vehicle power, ignition power and vehicle transmission.
It monitors three critical functions:
- Passenger occupies a seat and locks the seatbelt.
- Passenger occupied seat, but harness is NOT locked.
- Passenger occupied seat, locks harness behind them, then gets out of the seat.
The PROTEK system can be tied to a Vehicle Data Recorder (VDR) monitoring system which records emergency vehicle events. The PROTEK system has a 4-bit multiplexed TTL output, allowing the system to record up to 16 total events that pertain to the status of each seat. Any VDR system installed would “Poll” the outputs at a rate fast enough to read each seat byte and update an external recording system.
The PROTEK System components, seat and buckle sensors are continuously monitored, with visual feedback provided to the emergency vehicle operators. The operator will know when the attendants are properly secured with the harnesses, and the position of the attendant, either in or out of the seat. This enables them to take the appropriate precautions while driving. The system also provides a multiplexed output signal to interface with third party monitoring equipment.
The Seat Bend Sensor® comes with 3’ of lead wire with the connector attached for easy installation; termination pins and connectors are provided in the PROTEK kit for internal wire harness. The sensor has a sticky-back to adhere to the foam surface under the seat cover. Placement of the sensor should be approximately centered in the seat. Determine the position of the sensor prior to removal of the sticky-back cover. Once position is determined, mark it, remove the backing on the sensor and press firmly till the sensor is fastened to the seat surface. A hole can be created to feed the sensor leads down through the seat to an accessible termination area.
Flexpoint has numerous Domestic and Foreign Patents. Few Bend Sensor® Competitive Advantages.
- Single layer construction
- No sensor ventilation needed
- Excellent in harsh environments.
- Impervious to dust, dirt, liquids & temperature.
- Durability (life cycled > 30 MM without failure)
- Design Flexibility
- Reduced Material Usage
- Thinner, Lighter, Easier to Package
Application of bend sensor for seat occupancy detection has been validated for Aging / Fatigue Effects and Seat Level Durability Testing. Based on assumption of using a sensor mat consisting of a matrix of 16 sensors located in the center section of the seat bottom (no electronics). Weight of Sensor Mat only (no carrier) is Approx. 15 grams and that of Sensor Mat with Carrier: Approx. 62 grams. The OCS was developed to the point of DV testing. All sensor mat level, seat durability testing, and clinic level testing was completed.
For more information contact designhmi@gmail.com or contact Flexpoint https://www.flexpoint.com/.
Bend Sensor Seat Occupant / Child Detection
Flexpoint uses a coating that bonds extremely well to its substrate material. The carbon/polymer-based coating is very hard and very brittle and upon bending, the coating breaks forming many micro-cracks. The ink maintains its integrity in shape and continues to have a very high bond to the substrate material. When the material is bent over a given radius, it repeatedly returns to its original value, within the same curve of resistance per distance
The coatings are custom manufactured by Flexpoint and new coatings and products are constantly being developed.
One application for which Flexpoint Bend Sensor has been tested and validated for last few years is as Seat Occupancy and Classification Sensor. It has distinct advantages over normal FSR or Capacitive both in cost & reliability.
The above is applications Bend Sensor has been evaluated for and tested. It is ideally suited both for feature improvement and cost reduction. Ideal for next generation Autonomous Vehicles.
Belted Child Seat Vs. Small Adult Decision
The Flexpoint system discriminates between tightly belted child seats and small adults. The system identifies child seats by their pattern. If the pattern is that of a child seat the system will automatically respond with a “Suppress” decision. Small adults do not have the pattern of a child seat, and therefore the system will automatically proceed to looking at the DU value of the occupant.
The Flexpoint system discriminates between tightly belted child seats and small adults by determining weight and pattern.
The system identifies child seats by their pattern. If the pattern is that of a child seat the system will automatically respond with a “Suppress” decision.
Small adults do not have the pattern of a child seat, and therefore the system will automatically proceed to looking a weight of the occupant
Bend Sensor is manufactured by a screen print process:
- Bend Sensor printed and cured.
- Silver ink printed and cured
- Part is conditioned to induce micro-cracks in parts.
- Protective over-laminate applied.
- A variety of over-laminates can be applied to suit the needs of any application.
- Part is Die-Cut
- End of line functional test performed
- Process is very flexible
- Sensor geometry is limited only by the press size
- Flexpoint currently manufactures sensors from 3/8” to 67” long
In addition, following seats have had Flexpoint Weight Based Suppression Systems installed for testing:
- Chevrolet Blazer
- Ford Taurus
- Saturn
- Isuzu
- Cadillac
- Saab
- Opel
- Lear Innovations Van (Modified Chrysler Mini-Van)
- BMW Z3
- Chrysler Sebring
- Dodge Shadow
Environmental Test Summary
During various automotive development projects, the Flexpoint bend sensor or a system incorporating the bend sensor have been tested to and passed the following test profiles:
Power Temperature Cycling: 855 cycles of 85°C to –40°C (55 min per cycle)
Thermal Shock: 10 cycles of 85°C to –40°C with a transition time of 2 minutes and a 30-minute dwell
High Temperature Endurance: 400 hours @ 90°C
High Altitude Test: 3 cycles of 7 hours @ 12,200 m (2.7psi, -57°C) and 30 minutes @ 14.5psi and 85°C
Biased Humidity Test: 168 hours @ 65°C and 95% RH
Salt Fog Test: 96 hours of exposure to a salt fog
Water Submersion Test: 72-hour submersion at room temperature
Fluid Pour Test: Various liquids (ex: coffee, cola, alcohol, ammonia cleaner, urine) poured on the system
Mechanical Shock: 3 @ 20g peak acceleration half sine shocks in each of 6 axis (18 total shocks)
Drop Test: 1 m drop in each of 6 axis
Crush Test: Apply 110 N force to a 13mm diameter for 1 sec
Vibration: 107 cycles of 4.5g 10 Hz vibration
Random Vibration: 2 hours of 3.2g RMS random vibration in each of 3 axis (6 total hours)
Actuation Testing:
Horn: Actuated 10,000 @ ambient, 5,000 @ -40°C, and 5,000 @ 85°C
Seat Sensor: 300,000 cycles of Jounce and Squirm Testing
54,000 cycles of Sliding Entry (Ingress/Egress)
3000 cycles of knee load testing
Summary as of Aug 1st, 2018:
All results indicate this new approach to Occupant Classification yields similar performance to existing system. By utilizing ratio metrics the system is essentially self-calibrating
Benefits
- Calibration is not needed
- Serviceability – In field calibration is not needed
- Demonstrates better performance at RH and temperature extremes.
- Physical humidity compensation not needed
- Reference sensor immobilizers are no longer needed
For more information contact Flexpoint – www.flexpoint.com
