Motorcycle Airbag System

About the Motorcycle Airbag System

  • Introduction
  • Development Objective
  • Development History
  • Research and Development Methodology
  • System Composition and Functionality
  • System Operational Flow

System Composition and Functionality

The Motorcycle Airbag System is made up of the following main components:

  • The airbag module, containing the airbag and inflator, positioned in front of the rider
  • The airbag ECU, positioned on the right side of the airbag module, which analyzes impacts and determines whether or not to inflate the airbag
  • Four crash sensors, attached on both sides of the front fork to detect changes in acceleration caused by frontal impacts
Inflated Airbag

Inflated Airbag

Location of Principal Components

Location of Principal Components

Airbag module

Stored in front of the rider, the airbag module is comprised of the following components:

  • The airbag, which inflates to absorb some of the rider's kinetic energy
  • The inflator, which causes the airbag to inflate
  • A lid, which covers the other components stored in the airbag module, and which opens when the airbag is deployed
  • A retainer box, which contains and secures the airbag and inflator
Airbag module

Airbag module

Airbag

The airbag is made of the same type of material as automobile airbags: a strong nylon with an inner coating of silicon. Reaching a volume of some 150 liters when filled with the nitrogen gas used in deployment, the airbag is designed with a V-shaped back to help secure the rider in position. To prevent the airbag from going forward along with the rider, it is secured to the motorcycle with tethers. And to further cushion the impact of the airbag with the rider, deflation vents are located on each side of the back of the airbag.

Inflator

Similar in structure to the inflator used in a passenger-side automobile airbag, the inflator is a metal container and encloses an electronic ignition device, ignition agent, nitrogen gas ignition agent and other components. The inflator instantaneously responds to an electronic impulse from the airbag ECU, initiating the flow of nitrogen gas to inflate the airbag.

Lid

The lid is on the surface of the motorcycle and covers the airbag system components stored in the retainer box. During deployment, the pressure of the gas released by the inflator causes this lid to open.

Airbag ECU

The airbag ECU continuously monitors the data received from the crash sensors, and by comparing this data to standard vehicle behavior determines whether or not it is necessary to deploy the airbag. The data from each of the two sets of two sensors is evaluated independently, and if, according to the data of both sets of sensors, vehicle behavior deviates from standards to a certain predetermined degree, an electronic signal is sent to the airbag inflator, which causes the airbag to inflate. This design endows the airbag system with a high degree of reliability. In the event of an accident, even if power to the airbag ECU is completely or partially disrupted, a backup power source and circuitry are available to help maintain the system's functionality.

In addition, the airbag ECU has a diagnostic function that enables it to detect faults in the system. In case a problem is detected, a light located adjacent to the instrument gauges illuminates to alert the rider.

Crash Sensors

The crash sensors are attached to the front fork for earliest possible frontal impact detection. No alteration of the structure of the motorcycle is needed. To optimize the accuracy of collision detection, a set of four sensors are arranged-two on each side of the front fork. Thus mounted, these sensors are designed to detect acceleration changes with a high degree of precision and reliability even when a collision is accompanied by swerving.

In the unlikely event that one of the sensors malfunctions, the other sensors can provide backup functionality to help prevent unnecessary deployment of the airbag. When the motorcycle's ignition switch is on, the crash sensors continuously measure acceleration and relay this data to the airbag ECU.

Airbag ECU

Airbag ECU

Crash Sensors

Crash Sensors

Collision Recognition Process

Collision Recognition Process

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