UWB Radar for Child Presence Detection (CPD)

Introduction : As per protocols defined in EUROPEAN NEW CAR ASSESSMENT PROGRAMME (Euro NCAP), it is mandatory to incorporate child safety regulations by automakers. In order to fulfill requirement of child presence detection (CPD) various techniques have been implemented such as simple weight sensors, instrusive cameras etc. The latest standard is Ultra-Wideband (UWB).

Unlike a camera that “sees” a shape, or a weight sensor that “feels” mass, UWB radar “senses” life. It works by detecting the tiniest movements; specifically, the rise and fall of an infant’s chest while breathing.

How UWB based Child Presence Detection (CPD) System works

Following steps describe how the system works.

• In this system, the UWB sensor is installed in the car cabin. This sensor emits extremely short radio pulses continuously.
• These pulses bounce off everything present in the car including seats, windows, dashboard and passengers.
• The sensor catches the reflections. Static objects (e.g. leather seat) bounce the signal back with constant time delay.
• A sleeping child (if present) is not static. Even in deep sleep, their chest moves by few millimeters.
• The tiny movement changes the Time of Flight (ToF) of reflected signal by microscopic amount.
• If the rhythm matches human vital signs (e.g. 20 to 40 breaths per minute for an infant), the system flags a “Life Detected” event and triggers the local alarm. This will alert the owner to grab attention.
• It the owner is too far to hear the horn, the car utilizes Telematics Control Unit (TCU). With the help of TCU, when UWB sensor flags “critical event”, car’s computer sends data packet to cloud server of manufacturer. The cloud server pushes alert to smartphone app in owner’s mobile phone e.g. check rear seat notification etc.

The Child Presence Detection system uses algorithm. The UWB chip doesn’t just receive a “beep.” It generates a rich data set called the Channel Impulse Response (CIR). Think of the CIR as a 3D topographic map of the car’s interior at a specific split second.

Why UWB Beats Cameras and Ultrasonics

Following table mentions some of the benefits which clearly specifies that why UWB is superior for CPD compared to other techniques. This has become possible due to characteristics of radio waves compared to light or sound.

Summary: As mentioned in this application note, UWB finds the child. Cellular Telematics (IoT) calls the parent.