04 Safety Sensors Flashcards
Different sensor types for active safety (5)
- Vehicle control (Braking, Accelerator Pedal)
- Kinematics (Acceleration, Angle)
- Lateral external (LIDAR, RADAS)
- Longitudinal external (LIDAR, RADAS)
- Others (eye/head tracker, Driver Monitoring System DMS)
What is a sensor?
“A device which is used to record that something is present or
that there are changes in something”
Shortform meaning: ADAS, OEM, Tier 1 supplier, RADAR, LIDAR, CAN, SLAM
- ADAS – Advanced Driver Assistance System. A term subsuming active safety.
- OEM – Original Equipment Manufacturer. Typically vehicle manufacturers (selling to consumers)
- Tier 1 supplier – a supplier that supplies directly to the OEMs (Tier 2 supplies to Tier 1, etc.)
- RADAR – Radio Detection and Ranging
- LIDAR – LIght Detection And Ranging
- CAN – Controller Area Network. In-vehicle electronic bus system
- SLAM – Simultanious Localization And Mapping
Vehicle-control sensors: Angular/rotary position
Measures rotation
Typical resolution: ~0.5deg – 0.01deg
Several approaches
* “Encoder” based
* Resistance based (potentiometers)
* Magnetic
* Hall effect sensors
Vehicle-control sensors: Linear position
Measures linear position [typically mm]
Example: ”draw wire”
Vehicle kinematics sensors: Accelerometers
- Measures acceleration [m/s2 or g (gravity ~10m/s2)]
- Often 3-axis (x/y/z). X most often forward in automotive applications.
- Range should be 1g to 4g and around 0.01m/^2
- Rotation can be misinterpreted (centripetal)
Vehicle kinematics sensors: Accelerometers - Calculation
Range: 4,915g / 35g
Data resolution: 16bit / 8bit
LSB=”Resolution” = (4.915* 2) / 2^16 = 0.00015 g =0.0015 m/s2
-> good for active safety
LSB=”Resolution” = (35 * 2) / 2^8 = 0.27 g = 2.7 m/s2
-> good for crash
Vehicle kinematics sensors: Angular rate
Measures how fast something rotates [radians / second]
* 1-3 axis sensors
* Integration gives angle, but integration sensitive to drift!
Vehicle kinematics sensors: Angle
- Measures absolute angle (e.g., pitch or roll [deg or rad]
- Acceleration problematic – rotation affects value
- Integration of angular rate problematic - integration errors
”Longitudinal” sensors
- RADAR – Radio Detection and Ranging
- LIDAR – Light Detection and Ranging
- Vision – Different types of camera-based sensor solutions
”Longitudinal” sensors Comparison
Range, Angle, Velocity accuracy, Night, All-weather, Object classification
Vision / LIDAR / RADAR
* Range (-/+/+)
* Angle (+/+/-)
* Velocity accuracy (-/-/+)
* Night (-/+/+)
* All-weather (-/-/+)
* Object classification (+/+-/-)
RADAR – what is the task(s)?
- Observation of objects
- Observation of road /lanes
- Ego vehicle (estimate parameters)
RADAR basics
- Radio waves are created and transmitted. Focused as a lobe (with sub lobes). Reflections are received and interpreted.
- Time of flight and phase (for example with the Doppler effect)
- Different frequencies, e.g. 24, 77 and 79GHz -> higher is more narrow beam
- Rang up to 200m
LIDAR principle + difference
- Light emission – time of flight gives distance
- Static LIDAR
- Moving LIDAR (Scanning frequency important 20Hz)
- 1D, 2D and 3D LIDARs
LIDAR and RADAR differences
- LIDAR often has moving parts
- LIDAR often better angular resolution
- LIDAR so far more expensive (scanning)
- Velocity by Doppler effect in RADAR (today
“not possible” with LIDAR) - LIDAR has more weather issues
LSB
least significant bit
