Search Results

Current performance specifications of seat belt pretensioners include web retraction and belt load. These criteria may adequately represent the performance requirements of a pretensioner in a restraint system. However, by themselves, they are inadequate to evaluate potential design modifications to improve efficiency levels and thus increase energy output of the pretensioner. This paper demonstrates a non-linear phenomenon associated with web retraction and the belt load during pretensioning. It is this non-linear behavior that promotes the insensitivity for use of web retraction in predicting the energy output of a pretensioner with design modifications. This paper proposes an energy measuring method that can be used to more accurately measure the energy output of a pretensioner and then be used to evaluate the effects on output of a pretensioner due to design modifications.

Conventional restraint systems designed to meet US FMVSS standards only have one level of operation. The seat belt imparts a restraint force to the occupant reflective of belt stiffness characteristics and the airbag is either inflated or not inflated. The system is tuned to one crash scenario, typically a 30 mph (48 kph) barrier crash with an unbelted 50th%ile MHIII dummy. Situations involving other occupants, crash speeds or belt usage conditions may result in tradeoffs to maintain acceptable results for all conditions. Currently, there is considerable interest in adaptive restraint systems that can detect various crash conditions and adjust the restraint system to provide increased levels of protection. There is also a great deal of interest in systems that can detect an out of position occupant and adjust the airbag deployment to lessen the possibility of deployment induced injuries.