Study On Control System Development And Test Of Active Seatbelt

With the rapid development of automobile active safety,"Pre-crash" system which integrated active and passive safety technology can significantly improve driving safety,reduce collision accident and occupant injury.Active seatbelt(AS)tighten the seatbelt webbing during the pre-crash stage by receiving the warning signals of active safety systems,eliminate slack of seatbelt webbing effectively or reposition occupants,provide more efficient protection for occupants.However,the studies on product development and experiment research of active seatbelt are very scarce.There is no standard on product performance requirements and test methods for active seatbelt.Based on the above reasons,this paper developed an electric motor driven active seatbelt which is activated by advanced driver assistant systems(ADAS).The control strategy of control system was determined according to the function definition of active seatbelt.Completed software design of the control system based on the 16-bit microcontroller MC9S12G48.Communication protocol between AS system and ADAS was designed based on CAN bus.Seatbelt webbing was retracted by activating the electric motor attached to the seatbelt retractor after receiving warning signals.Completed software design of CAN bootloader system to implement software download,debug and update online.Active and passive safety integrated system of AS and ADAS was constructed to verify AS function response performance.Signal conversion ECU was designed to convert forward collision warning system LZADAS’s RS232 signal into CAN signal for AS,integrated system’s communication protocol was designed based on system function matching definition,real vehicle test results under passenger car environment showed that AS function response accuracy was 100%.AS-Mobileye integrated system was constructed under bus environment,AS system accessed to the vehicle CAN bus directly for signal reception,AS function response accuracy was 100%.AS system can realize real-time signal reception,identification and processing,and further implementation of the corresponding AS function.Product performance experiments were conducted to obtain preload performance parameters,including determination test of control parameter setting range,motor operating current test,belt forces test,belt velocity test and durability test.Retractor output forces were 31.8N to 546.1N,shoulder belt forces were 27.5N to 460.7N.Belt velocity was 0.111m/s to 0.393m/s.Maximum tension in shoulder belt completed its retraction at about 252ms under maximum belt velocity.The performance parameters of active seatbelt developed in this paper can meet the design requirement.Volunteer tests were conducted to define the best shoulder belt force to eliminate slack of seatbelt webbing without uncomfortable and the minimum force that causes the volunteers to be uncomfortable,the best shoulder belt force to eliminate slack were 32.62N to 64.15N,the mean is 46.87N,and there is no gender difference.Gender difference occurred in the minimum force that causes uncomfortable,the shoulder belt force of male were 90.96N to 180.4N,the mean is 133.69N,female were 75.57N to 92.34N,the mean is 83.08N.One-month real vehicle test was conducted by a volunteer driver using a car fitted with the AS-LZADAS integrated system,test results verified the stability and reliability of active seatbelt.However,high response frequency of active seatbelt would affect driver’s comfort,and high shoulder belt force would have a negative impact on the driver’s comfort under non-crash period.