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Traction Control

2022-03-06T00:54:02Z

Yessamgerg:

[[Engine Control]]

==Rationale==
[[File:Tire slip and grip.PNG|none|middle|thumb|Grip Coefficient vs Slip]]

<a class="image"><img alt="" src="/images/d/da/Tire_slip_and_grip.PNG" decoding="async" class="thumbimage" width="300" height="273"></a> <a class="internal" title="Enlarge"></a>Grip Coefficient vs Slip

<a class="image"><img alt="" src="/images/d/da/Tire_slip_and_grip.PNG" decoding="async" class="thumbimage" width="300" height="273"></a> <a class="internal" title="Enlarge"></a>Grip Coefficient vs Slip
Tire generates most longitudinal grip (good stuff) when slightly slipping (see pic). Need complex system of electronics and mind tricks to enable this condition at all possible times. This will enable go fast more.

This should not be confused with lateral traction which is controlled by the dark wizards in the fourth dimension who demand virginal sacrifices. Depending on the driver's skill, how much lateral load is carried by the tires, the surface conditions, the setup of the chassis etc. the targeted slip will differ.

==Basic Principles ==
In order to ensure the the tire is working in the intended slip ratio, we first must determine what the slip of the tire is. There are a variety of ways to calculate slip but all versions basically come down to how much faster or slower the tire contact patch is traveling relative to the ground. In order to create a consistent, high performance traction control system, an accurate velocity estimation is critical.
===Velocity Estimate===
In a rear wheel drive vehicle, a reasonable first pass would be to take the average of the two front wheels speeds. Because these wheels are un-driven, they are generally going to be traveling the same speed as the ground. Further considerations need to be taken for an AWD vehicle sense the lack of un-driven wheels means that wheel speeds alone can't be used to determine how fast the vehicle is going. In these cases a variety of solutions such as integrating the longitudinal acceleration can be used to fill in periods where the wheels are slipping.

The same AWD considerations apply in the case of an RWD EV with regen since while braking the front wheels will be in slip.
===Slip Estimation===
Once the vehicle velocity is determined, it is possible to determine the amount of slip that the tire is experiencing.

It is important to also consider the effects of the different corner radii that the inside vs outside and front vs rear wheels travel while the vehicle is turning.
===Slip Target===
In a basic system, the slip target can be set to the slip at which the tire produces it's peak torque. If the velocity estimate is robust and the traction control regulation is well tuned, this will provide good acceleration performance in a straight line while aiding stability in a corner. Further improvements can be made by modifying the slip targets when the vehicle is turning, since with increasing slip angle the slip ratio for peak longitudinal force tends to reduce.
===Combustion Engine Control===
The spin of the wheels is managed by speeding them up or slowing them down. This can either be done by the engine, clutch, or brakes. Dont do brakes because thats insane [citation needed]. Clutch modulation is often present/inherent in motorcycle clutches, but do not trasnlate well to this application.
* engine
** spark
** fuel
* clutch?
* not sure if anyone does some other crazy shit like brakes or smth

===EV Motor Control===
idk what yall EEs do like voltage control or smth
==Failure Modes==
Since traction control is able to reduce (or completely eliminate) motor torque, it is important to consider the failure modes of the system. This can be as simple as providing the driver a switch to disable traction control, or more complex where either through electrical or model based checks of the plausibility of sensor values. In either case its possible that the driver may not realize that a loss of torque is caused by traction control, so some feedback mechanism to tell the driver when traction control is active is worth considering.
==Launch Control==
launch control stops burnouts which is more faster but less cool
* algo

==Mid Corner Traction Control==
rwd snap oversteer bad
* algo
[[Category:Electric Vehicle]]

[[Category:Internal Combustion]]

Traction Control

2022-03-06T00:50:02Z

Yessamgerg: WIP vel est, slip est, slip target, failure modes summaries

[[Engine Control]]
==Rationale==
[[File:Tire slip and grip.PNG|none|middle|thumb|Grip Coefficient vs Slip]]

<a class="image"><img alt="" src="/images/d/da/Tire_slip_and_grip.PNG" decoding="async" class="thumbimage" width="300" height="273"></a> <a class="internal" title="Enlarge"></a>Grip Coefficient vs Slip
Tire generates most longitudinal grip (good stuff) when slightly slipping (see pic). Need complex system of electronics and mind tricks to enable this condition at all possible times. This will enable go fast more.

This should not be confused with lateral traction which is controlled by the dark wizards in the fourth dimension who demand virginal sacrifices. Depending on the driver's skill, how much lateral load is carried by the tires, the surface conditions, the setup of the chassis etc. the targeted slip will differ.

==Basic Principles ==

In order to ensure the the tire is working in the intended slip ratio, we first must determine what the slip of the tire is. There are a variety of ways to calculate slip but all versions basically come down to how much faster or slower the tire contact patch is traveling relative to the ground. In order to create a consistent, high performance traction control system, an accurate velocity estimation is critical.
==='''Velocity Estimate'''===
In a rear wheel drive vehicle, a reasonable first pass would be to take the average of the two front wheels speeds. Because these wheels are un-driven, they are generally going to be traveling the same speed as the ground. Further considerations need to be taken for an AWD vehicle sense the lack of un-driven wheels means that wheel speeds alone can't be used to determine how fast the vehicle is going. In these cases a variety of solutions such as integrating the longitudinal acceleration can be used to fill in periods where the wheels are slipping.

The same AWD considerations apply in the case of an RWD EV with regen since while braking the front wheels will be in slip.
===Slip Estimation===
Once the vehicle velocity is determined, it is possible to determine the amount of slip that the tire is experiencing.

It is important to also consider the effects of the different corner radii that the inside vs outside and front vs rear wheels travel while the vehicle is turning.
===Slip Target===
In a basic system, the slip target can be set to the slip at which the tire produces it's peak torque. If the velocity estimate is robust and the traction control regulation is well tuned, this will provide good acceleration performance in a straight line while aiding stability in a corner. Further improvements can be made by modifying the slip targets when the vehicle is turning, since with increasing slip angle the slip ratio for peak tractive force tends to reduce.
==Combustion Engine Control==
The spin of the wheels is managed by speeding them up or slowing them down. This can either be done by the engine, clutch, or brakes. Dont do brakes because thats insane [citation needed]. Clutch modulation is often present/inherent in motorcycle clutches, but do not trasnlate well to this application.
* engine
** spark
** fuel
* clutch?
* not sure if anyone does some other crazy shit like brakes or smth

==EV Motor Control==
idk what yall EEs do like voltage control or smth
====
==Failure Modes==
Since traction control is able to reduce (or completely eliminate) motor torque, it is important to consider the failure modes of the system. This can be as simple as providing the driver a switch to disable traction control, or more complex where either through electrical or model based checks of the plausibility of sensor values. In either case its possible that the driver may not realize that a loss of torque is caused by traction control, so some feedback mechanism to tell the driver when traction control is active is worth considering.
==Launch Control==
launch control stops burnouts which is more faster but less cool
* algo

==Mid Corner Traction Control==
rwd snap oversteer bad
* algo
[[Category:Electric Vehicle]]

[[Category:Internal Combustion]]

G-g Diagram

2020-05-16T16:41:34Z

Yessamgerg:

[[File:GGDiagram.PNG|right|middle|thumb|Figure 1 - FSAE Winton 2019]][[File:OpitmumG-G-G-diagram.jpg|right|middle|thumb|Figure 2 - An enhanced GG Diagram, made by OptimumG]]A '''g-g Diagram''' is a chart that graphs the lateral and longitudinal acceleration. This chart is an important indicator of the performance of any racecar. During a race, the vehicle should be accelerating at all times; either laterally (turning), longitudinally (accelerating and braking), or some combination of both. Engineers and drivers should try to maximize the acceleration at all times.
==The Concept==
The most basic concept of car handling is that a tyre exerts a force on the road. The grip available under braking is virtually the same as the grip available during cornering. This grip can be measured in terms of acceleration (m/s2or G). Assuming a car capable of 15m/s2(as shown in Figure 1), this turns out to be a graph of what is approximately a circle. The car can turn left at up to15m/s2, brake at up to15m/s2or turn right at up to15m/s2, limited primarily by the grip between the tyres and the road surface. The suspension does have an effect in all this, but it's main function here is to help the tyres generate the grip they are potentially capable of.
==Notes==
Figure 2 demonstrates this behaviour again, but in G forces. Either practice is fine, with 1 G = 9.81m/s2.

The solid line around the edge of the chart represents the "g-g" boundary and indicates the maximum acceleration the vehicle is capable of if driven perfectly.

[[Category:Vehicle Dynamics]]

Thread:Category talk:Vehicle Dynamics/Subcategories that make sense/reply (11)

2020-05-15T15:23:07Z

Yessamgerg: Reply to Subcategories that make sense

I'd argue that suspension should only contain mechanical design topics, and that all tire modeling, kinematics, spring/arb/damper tuning etc should be contained under the vehicle dynamics category. I'd also say that the same should apply to much of the aerodynamics mass vs drag vs downforce, the powertrain power vs mass vs efficiency trade-offs & the differential selection and tuning.