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Professional Motorsport Data Analysis: Laser Ride Height

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Laser Ride Height

04.35

00:00 - In many situations, calculating the dynamic ride height is done using damper potentiometers.
00:06 This means converting the damper position to wheel position and using some maths to extrapolate the ride height of the positions of interest of the sprung mass which is just another way of saying the chassis.
00:18 This has some advantages in that we can make use of sensors that we already have fitted for another purpose.
00:25 But the downside is it's an approximation that requires a lot of assumptions.
00:30 In cases where the pitch and roll angles and proximity of the floor of the car to the ground is sensitive aerodynamically, then it's often not sufficient to use the damper potentiometers to approximate the ride heights.
00:44 This is because we're only measuring the deflection of the unsprung mass with respect to the sprung mass and not the ground.
00:51 In this case we're not accounting for the vertical deflection of the tyres and we also have areas compounding in the subsequent calculations.
00:59 Sensitivity of the floor height and inclination which is another way of saying pitch and roll, is an issue in most medium and high downforce applications as the floor is often generating a large proportion of the total downforce.
01:14 A common solution is to use a sensor to directly measure the proximity between the sprung mass and the road surface.
01:20 This is most commonly done with laser ride height sensors.
01:24 The measurement principle is a laser beam that is directed from the sensor towards the ground at a known angle, the reflection of this beam from the road surface is measured inside the sensor and the position of the reflection tells the sensor the proximity between the road surface and the sensor.
01:42 Laser ride height sensors can be attached to any part of the car to measure the proximity to the ground.
01:48 This can include attaching them to the wheels themselves via a rotating fixture to more accurately measure the vertical deflection of each tyre.
01:55 With that said, the most common application by far is to mount them to the sprung mass because as we touched on earlier, this allows us to accurately understand the proximity of each part of the sprung mass to the road surface, removing some of the problems when using damper potentiometers to calculate ride height.
02:12 Generally, we treat the floor of the car as a plane mathematically.
02:17 If we can define a plane representing the floor of the car, then assuming the floor is rigid and the road surface is flat, we can calculate the height of any part of the floor above the road surface.
02:27 Mathematically we only need to know the position of 3 points in space, to define a plane and for this reason we generally only use 3 laser ride height sensors attached to the sprung mass.
02:40 Teo at one end of the car and one at the other.
02:43 In most applications, the front of the car is most sensitive to ride height and inclination so it makes sense to mount two sensors up the front and one in the rear.
02:53 The further apart the sensors are fitted, the higher the accuracy of the inclination angle calculation of the floor.
03:00 So you would normally see the front sensors mounted as far outboard and as far forward as practical with the rear one being mounted centrally and as rearward as practical.
03:10 If the sensors are going to be fitted permanently, they need to be integrated with the floor of the car smoothly as they need line of sight to the road surface.
03:19 Depending on how well integrated they are, this can affect the performance of the floor itself.
03:25 If the sensors are only fitted for some specific short term testing which is often the case, they're sometimes mounted on the exterior of the car, say on the outside of the front or rear bumpers.
03:36 Obviously doing this will have its own aerodynamic effects which need to be accounted for.
03:41 The sensors need to be firmly mounted, properly aligned with the road surface, and above all their positions in X, Y and Z with respect to the chassis need to be known.
03:51 Using these known positions, we can translate the proximity measurement of each sensor to the ride height of any point of interest on the car.
03:59 Each brand and model of sensor has specific working ranges within which, the measurement accuracy is trusted.
04:07 This working range is generally in the vicinity of around 50 to 300 mm.
04:12 This range impacts our choice in mounting positions as the face of the sensor and the ground must remain within the manufacturer's stated range at all times for the measurements to be valid.