Hello, I have a project in mind that I hope to make a small scale and hopefully deploy it in the real world. I am trying to make an "active aero" rear spoiler for a car. my idea was to have an Arduino in the trunk controlling the whole system. This Arduino has 2 stepper motors connected to it. These steppers are being used to control the physical flap that deploys. The system is supposed to activate under hard braking, highspeed, upon vehicle startup, and maybe under heavy cornering but that can come later since it does need another sensor. the car that I am planning on implementing this is the E36 BMW 3 series. I have only thought about this in my head so I'm not 100% on the exact requirements just yet but maybe you guys could guide me through it. this is my first real Arduino project and I am new to it so bear with me :).
It should go something like this
Arduino in the trunk, this is connected to a pressure switch on the brake pedal to tell the system to deploy. the Arduino controls 2 drivers for a Stepper motor. this stepper motor is connected to the flap which will flip it up at a 45% angle. The system can deploy under hard braking (more than 75% braking) high speeds (75mph) and upon vehicle startup (wing will flip up then come back to rest just for "show"). There is also going to be a cabin switch that when flipped will toggle the active aero to stay up.
I can, of course, explain more specific parts if you guys have any questions because I'm not all too sure where to start. The actual fabrication part is something that I will have to worry about later but for now, I need the mechanics and actual Arduino part working. It seems simple enough but of course, that's what they all say thank you!
ps: I plan to cut the middle of the spoiler deck and attatch the steppers in those almost like a aileron on a airplane wing notice how that moves.
The first thing you probably need to do is get the arduino and a couple pieces of simple test pieces like a multi-meter, wires, a potentiometer, switches, and similar. Then you can start simulating the inputs/outputs in the code you are developing. You might consider using servos instead of stepper motors as they are simple to control.
I have a start kit with me, I will start experimenting with the code. I will check out servos too but I read that Steppers are more percise and quicker? I really need speed here since this is something that must deploy quickly
I would also suggest servo's as being the better option.
They can often be as quick for these tasks as a servo if not quicker depending on the linkage.
A pair of decent size depending on the weight etc of the foil.
Link them to an half decent accelerometer and an Arduino and you almost have the whole project.
For your small scale model, it does not matter what you use to do the physical movement.
For your real life implementation, I suspect that you will need to actuators designed to handle the large loads that will be present.
Your selection of the pivot point will have a big impact on the force required to deploy. It also has an impact on stability. Too far and your spoiler will flutter.
Just a thought - rather than using a physical switch to detect the brakes, why not use the brake light?
the Problem with the brake light is that it only needs to deploy under hard braking. UNLESS the motor doesn’t need too much of a cool down time. If it doesn’t have a problem being deployed very frequently then yeah brake lights could make it even simpler. But how would that work? Does the ardrunio sense a lot electric signal in the brake light then deploys?
Doing it on a real car that will operate on public roads is completely different. You should seek prior written approval from your automobile insurer. I very much doubt that they would give it.
The device might upset the dynamics of your car and make it difficult to control in an emergency, or the device might fly off and kill a bystander.
This will be intended for a closed course on a race track only
The aero dynamics should be fine. This is on a already purpose built wing I am just automaticly lifting it up which it is already designed to do since it is adjustable
I thought F1 and the like had to be manual adjustment.
At any rate, stepper may not have enough grunt.
Then again, you could do as in aircraft and use a servo to drive an "elevator surface" attached within the wing.
Elevator then does all the hard work.
Would need engineering approval though for the "Racetrack..:)".
bluejets:
Then again, you could do as in aircraft and use a servo to drive an "elevator surface" attached within the wing.
Elevator then does all the hard work.
They also have actuators with a LOT OF GRUNT.
B737 has upper wing spoilers about the size of a regular kitchen door. They can open to well over 45° when flying at 200+ kts in a second or two and close just as quickly. IIRC they are even bigger on a 747.
Robin2:
They also have actuators with a LOT OF GRUNT.
B737 has upper wing spoilers about the size of a regular kitchen door. They can open to well over 45° when flying at 200+ kts in a second or two and close just as quickly. IIRC they are even bigger on a 747.
...R
Perhaps, but they still use trim tabs on the elevators and rudder.
Point being, the surface can be moved by a much smaller force if needed.
bluejets:
Perhaps, but they still use trim tabs on the elevators and rudder.
Point being, the surface can be moved by a much smaller force if needed.
Those trim tabs are used to adjust the steady-state attitude of the plane. I don't think that concept would have an application for the OP's problem which, I suspect, needs fast-reacting adjustments.
The speed would be nice but is not required. Maybe if the wing could extend fully in a little over a second. As Long as it fully deploys in under 2 seconds it would work.
Another method could be like struts that can be attached to the point of the wing that needs to lift up. but that is way too big for my needs since it needs to be very compact so that's why a motor might work.
If you need something strong, you might consider a windshield wiper motor. The mechanical design of the flap will dictate what will be needed to drive the flap. I would make it removable for everyday driving, maybe something that attaches to the inside of the existing spoiler between the spoiler top and the trunk deck. The added weight might also negate any added driving advantage.
Two seconds to deploy seems like a long time. Most corners on a race track are above 100 feet per second even the really slow ones are usually 60 miles per hour = 88 FPS. Only a few hairpin turns are slower than 60 MPH. Your brake zones might be marked out to 500 feet but you will often be braking at or below the 200 foot marker unless you are driving a very high powered car travelling above 150 MPH. Autocross racing is slower but time spent on the brakes is even shorter.
I would agree that triggering on the brake light is probably a good idea. The penalty for high downforce during light braking is very minor compared to late deployment during high brake force waiting for an accelerometer to register. (or the sponginess of a brake pedal caused by the volume of brake fluid used in a pressure sensor)
A servo might not be necessary, a simple motor and a limit switch might be sufficient. It sounds like you only have two positions: fully on for high drag / high downforce, and fully off for low drag / normal downforce.
Another option might be to have the motor work against the downforce to move the wing to low drag mode. That way the motor is releasing force when switching to high drag mode. Deployment will be fast. Working against downforce to lower drag will deploy more slowly but you will be driving more slowly since you just finished braking.
