Object Detection (B3T)
Object Detection Description and Operation (B3T)
Pedestrian Impact Detection System Description and Operation
The pedestrian impact detection systems primary function is to provide supplemental protection to vulnerable road users involved in vehicle impacts. The pedestrian impact detection system is also known as the active pedestrian protection system. The pedestrian impact detection system is a functional system for raising the hood to provide sufficient vertical deformation space under the hood. In Europe and Japan an active pedestrian impact detection system is necessary for vehicles which do not provide the required deformation space under the hood. The pedestrian impact detection system includes the following components
* Pedestrian Impact Detection Module
* Discrimination Sensor (Front Upper Beam Sensor)
* Safing Sensor (Rear Upper Beam Sensor)
* Two Hood Hinge Actuators
The pedestrian impact detection system will sense and discriminate vulnerable road user impacts and deploy the hood hinge actuators in a timely manner to protect the pedestrian. The term "deployment" applies to the activation of the hood via the hood actuators. The pedestrian impact detection system is designed to sense and discriminate road user impacts (eg. pedestrian, cyclist) from other types of impacts in order to properly deploy the hood actuators. No actions or inputs are required from the driver or passenger to trigger this device. The pedestrian impact detection module uses the safing and discrimination sensor to get acceleration and force information needed for the deployment of the hood hinge actuators. The pedestrian impact detection module deploys the hood actuators using two deployment loops. The pedestrian impact detection system only operates at vehicles speeds between 27 km/h (16 mph) to 45 km/h (27 mph). The pedestrian impact detection module detects internal and interface faults and commands the Service Pedestrian Protection System message in the DIC to indicate a system fault.
After a deployment event, the vehicle operator is able to reset the hood to its normal driving position. After resetting the hood, the pedestrian impact detection system is not required to be fully functional. For full functionality, it is necessary to replace system component(s) at an approved service facility.
Safing Sensor
The safing sensor provides vehicle acceleration information to the pedestrian impact detection module. The safing sensor uses an independent electronic safing method acting through an independent logic circuit such that no single point failure can lead to an unwanted actuation of the hood. The pedestrian impact detection module provides a two wire current loop interface to the safing sensor. The pedestrian impact detection module also provides power and ground to the safing sensor over the same two wire discrete interface.
Discrimination Sensor
The discrimination sensor provides discrete force information to the pedestrian impact detection module. The pedestrian impact detection module uses measurable pedestrian impact data sent from the discrimination sensor to determine the severity of the impact. The pedestrian impact detection module provides a two wire current loop interface to the discrimination sensor. The pedestrian impact detection module also provides power and ground to the discrimination sensor over two separate discrete circuits.
Hood Hinge Actuators
The pedestrian hood actuators deploy only when a valid signal whose energy is capable of triggering deployment of the hood is present. The pedestrian hood actuators only deploy in those events where the activation of the hood is expected. The hood actuator is not expected to deploy in low severity event where the risk of injury is low or in a high severity event like car to car crash. During a frontal pedestrian impact of sufficient force, the pedestrian impact detection module will allow current to flow through the deployment loops in order to deploy the hood hinge actuators. The pedestrian impact detection module also performs continuous diagnostic tests on the deployment loops to check for proper circuit continuity, shorts to ground and shorts voltage. In order to prevent unwanted deployment of the actuator during service, the hood hinge actuator contains 2 shorting bars that will short both high and low circuit pins when disconnected. The pedestrian impact detection module only issues a deployment command when a valid safing signal or confirmation has been generated. No inadvertent deployments will occur in any deployment loop due to a single point fault.