Method and apparatus for controlling an actuatable protection device with rough terrain and airborne detection

A vehicle safety system for a vehicle, comprising:

• an actuatable controlled restraint (ACR) including a seatbelt for restraining a vehicle occupant, the ACR being actuatable to control payout and retraction of the seatbelt;
• and
• a controller configured to determine operating conditions of the vehicle and to control the actuation of the ACR in response to the determined operating conditions of the vehicle,
• wherein:
• the ACR has a normal restraint condition and an enhanced restraint condition;
• the controller is configured to implement a longitudinal acceleration airborne metric that evaluates vehicle longitudinal accelerations measured along a vehicle X-axis over time, the longitudinal acceleration airborne metric defining a threshold having a predetermined bandwidth that extends above and below a zero of the longitudinal acceleration, wherein the longitudinal acceleration airborne metric is configured to determine that the vehicle is in a vehicle airborne condition in response to a magnitude of the longitudinal acceleration exceeding and falling back within the threshold, the longitudinal acceleration airborne metric maintaining the vehicle airborne condition determination while the longitudinal acceleration remains within the threshold;
• the controller is configured to implement a lateral acceleration airborne metric that evaluates vehicle lateral accelerations measured along a vehicle Y-axis over time, the lateral acceleration airborne metric defining a threshold having a predetermined bandwidth that extends above and below a zero of the lateral acceleration, wherein the lateral acceleration airborne metric is configured to determine that the vehicle is in the vehicle airborne condition in response to a magnitude of the lateral acceleration exceeding and falling back within the threshold, the lateral acceleration airborne metric maintaining the vehicle airborne condition determination while the lateral acceleration remains within the threshold;
• the controller is configured to implement a roll acceleration airborne metric that evaluates vehicle roll accelerations measured about the vehicle X-axis over time, the roll acceleration airborne metric defining a threshold having a predetermined bandwidth that extends above and below a zero of the roll acceleration, wherein the roll acceleration airborne metric is configured to determine that the vehicle is in the vehicle airborne condition in response to a magnitude of the roll acceleration exceeding and falling back within the threshold, the roll acceleration airborne metric maintaining the vehicle airborne condition determination while the roll acceleration remains within the threshold;
• the controller is configured to implement a vertical acceleration airborne metric that evaluates vehicle vertical accelerations measured along a vehicle Z-axis over time, the vertical acceleration airborne metric defining a threshold having a predetermined bandwidth that extends above and below a zero of the vertical acceleration, wherein the vertical acceleration airborne metric is calibrated to compensate for the effects of gravity, wherein the vertical acceleration airborne metric is configured to determine that the vehicle is in the vehicle airborne condition in response to the vertical acceleration crossing into the threshold, the vertical acceleration airborne metric maintaining the vehicle airborne condition determination while the vertical acceleration remains within the threshold, and
• the controller is configured to actuate the ACR from the normal restraint condition to the enhanced restraint condition in response to determining that the vehicle is in the vehicle airborne condition.