Active Rear Wing Control System. Help Needed

[maddox10]

Hi there,

I ment that an old school end switch/relay based setup would be large and heavy, offsetting most advantages the idea can have. One of the reasons active wing control ain't that much used.

After looking several youtube's with cars with active wing control I'm almost sure the GLA linaks will come up short.

These just don't have the grunt/speed for the demands imposed on them for an effective active wing.

Nicks remarks stay to the point. I'm curious how custom build you want to go. Building 4000Nm linaks with speeds up to 1m/sec isn't rocket science.

[overkill]

Have to agree about a custom actuator and it might not be much work. Using that GLA4000 as an example, it only has a 50 watt motor and I'd bet you a pint of Guinness that is fairly low RPM as well. By changing the motor for one with 4 or 5 times the RPM and maybe 100 to 200 Watts power, you would get the required force and speed without having to make an actuator from scratch.

Some random thoughts:

Using two actuators is probably LESS reliable than using one larger one. If a motor or gear fails, it will lock the actuator solid and the other actuator will be trying to twist the wing - either something mechanical will break of the 2nd motor will burn out quickly.

If you use an Arduino, this motor control shield might be a good match:http://tinyurl.com/bmp4lmy. It uses automotive motor control chips that have temperature & current limiting and should handle high power actuators. It will work with very little programming and has advanced features you could use at a later date.

What sort of budget are we working with - penniless student or rich sponsored/factory team?

The forces acting on the push rod and actuator are always going to be compressive, which is exactly how actuators are meant to be used. For the push rod, I'd be using a wider tube rather than a thin solid rod as it will deflect less in compression for the same weight. Add a million style points if you can use a carbon fibre tube.

[Peadar]

Have to agree about a custom actuator and it might not be much work. Using that GLA4000 as an example, it only has a 50 watt motor and I'd bet you a pint of Guinness that is fairly low RPM as well. By changing the motor for one with 4 or 5 times the RPM and maybe 100 to 200 Watts power, you would get the required force and speed without having to make an actuator from scratch.

Some random thoughts:

Using two actuators is probably LESS reliable than using one larger one. If a motor or gear fails, it will lock the actuator solid and the other actuator will be trying to twist the wing - either something mechanical will break of the 2nd motor will burn out quickly.

If you use an Arduino, this motor control shield might be a good match:http://tinyurl.com/bmp4lmy. It uses automotive motor control chips that have temperature & current limiting and should handle high power actuators. It will work with very little programming and has advanced features you could use at a later date.

What sort of budget are we working with - penniless student or rich sponsored/factory team?

The forces acting on the push rod and actuator are always going to be compressive, which is exactly how actuators are meant to be used. For the push rod, I'd be using a wider tube rather than a thin solid rod as it will deflect less in compression for the same weight. Add a million style points if you can use a carbon fibre tube.

Hi all,
Apologies for the lack of replies, I have been mad busy lately.
I received the actuators, they are very very small and light.
After considering a lot of your input (and others from various backgrounds) i have decided to make several changes to the design.

1. Use only one actuator, it seems this is a logical step for reliability and also aerodynamics. The actuator I have can handle 2300N so that will be ok on its own.
In the future i can upgrade my motor to be more powerful/quicker

2. The actuator and wing will be mounted to a subframe as such in the boot. The boot lid will play no role in suporting the wing, it will just act as a cover. The car has gone to get a role cage this week so the work will be completed then.

3. The actuator will act in the centre of the wing between the two mounts.

4. The wing has been increased in size to 1700x400mm
Here are the latest calculations after these changes...

Thats 125kg @100mph! Happy days


I'll try to keep here updated, thanks all for the input, it has been an eye opener to some aspects. I hope to be working on the mechanical construction for the next 3 weeks so I won't be focusing on the aspect at hand here. But once the wing is completed I'll have photos up for all to see and then I can concentrate on the controls aspect.

Thanks again,
Peter

[Peadar]

Also, @overkill
I am most definitely a poor student haha

[Peadar]

Hi all,
I have the wing nearly built now so its nearly time to move onto the control side as my main focus.
I have re read all of the posts here just to make sure I am up to date.
First off, I have decided to use only one of the actuators. So that will reduce some of the work load.

Assuming I am to use an Arduino or othe MCU what do I need otherwise.
The actuator I have chosen (maybe foolishly) have no feedback or limit to stop it from running beyond its maximum range. So a potentiometer or some sort of feedback is required? Is this then feed into the MCU? Just trying to get an idea of what more I will need to complete this project

As you can probably tell I am not much of an electronics head so apologies if I seem totally lost here.

[overkill]

It would be better to use a pair of microswitches rather than a potentiometer - they are easier to interface and much less affected by heat and dirt. You will need to find a convenient spot to mount the switches, probably on the actuator or nearby. You arrange the switches so that the actuator switches them on at each end of it's travel.

What might be even easier to set up is three switches that indicate the positions of the wing since the up & down positions of the wing are essentially the same as the actuator's limits. The middle switch indicates the neutral position and you just need to adjust the switch positions on the bracket to fine-tune the wing position.

The switches will be connected to three digital input pins on the MCU and the software will use the switch inputs to know when the actuator is in the right position.

[Peadar]

It would be better to use a pair of microswitches rather than a potentiometer - they are easier to interface and much less affected by heat and dirt. You will need to find a convenient spot to mount the switches, probably on the actuator or nearby. You arrange the switches so that the actuator switches them on at each end of it's travel.

What might be even easier to set up is three switches that indicate the positions of the wing since the up & down positions of the wing are essentially the same as the actuator's limits. The middle switch indicates the neutral position and you just need to adjust the switch positions on the bracket to fine-tune the wing position.

The switches will be connected to three digital input pins on the MCU and the software will use the switch inputs to know when the actuator is in the right position.

Thanks for the reply overkill,
I had initially thought i could go about it that way as it seemed straight forward and simple. It might be tricky to make up a mounting bracket to house the microswitches. I could have a small tab as such on the connecting rod from the actuators which as you say, trips the limit switches one by one. One difficulty is that the movement of the actuator is only 50mm so the switches would need to be mounted quite accurately.
Would anything else be required other than the limit switched and an MCU which can take 5 inputs?

[overkill]

Not much; the main items will be a couple of relays (or a single DPDT relay) and a simple circuit to drive them as an MCU output doesn't have the capacity to drive a relay directly. Alternatively, you can use an 'H bridge' which essentially does the same job as the relays but its all electronic with no moving parts. You will also need a DC to DC power supply to drop the car's 12 volts down to 5V or 3.3V for the MCU. almost all that stuff is "off the shelf", I or the other furum members can probably whip up a circuit and a shopping list if you need it.

[Peadar]

Not much; the main items will be a couple of relays (or a single DPDT relay) and a simple circuit to drive them as an MCU output doesn't have the capacity to drive a relay directly. Alternatively, you can use an 'H bridge' which essentially does the same job as the relays but its all electronic with no moving parts. You will also need a DC to DC power supply to drop the car's 12 volts down to 5V or 3.3V for the MCU. almost all that stuff is "off the shelf", I or the other furum members can probably whip up a circuit and a shopping list if you need it.

That sounds great, if I could see what I actually need it would be easier to work from and also easier to approach lectures in college if I need help as then I'd have something to work with. Really appreciate the help

[overkill]

No Problems, I need a bit of a break from robots today. Do you prefer to control the motor with relays or with electronics. The main differences are that the relays will be a bit cheaper but will need more custom wiring. Using a solidstate H bridge might be a bit more compact as it can fit right on the arduino board

[Peadar]

No Problems, I need a bit of a break from robots today. Do you prefer to control the motor with relays or with electronics. The main differences are that the relays will be a bit cheaper but will need more custom wiring. Using a solidstate H bridge might be a bit more compact as it can fit right on the arduino board

This is a break? haha

Correct me if I'm wrong anywhere here!

Thats 2 options then:
1. Relays using physical contact as feedback as such? Seems fairly simple to set the limits of movements/set points
2. H bridge, how are the limits of movement set? and the set points, this is where my total lack of knowledge towards electronics is blatantly obvious!

But in both cases i need:
1. DC to DC power supply
2. Arduino

Any ideas of a very vague cost to get this system up and going? Projects cost about €300 so far

[overkill]

The motor drive with relays or an H-bridge is completely separate from the position sensing, with the MCU in the middle to take the position and driver switches and translate that into turning the motor in the right direction. All the relays (or H-bridge) does is power the motor; they don't have anything to do with feedback.

The DC supply would just be 3 or 4 small components to step the 12V down to 5V; they can be soldered onto a small piece of veroboard with basic skills or a pre-built item can be sourced (we call them a 'BEC' for battery eliminator circuit). Since the project has few inputs and outputs, you really only need the most basic Arduino board probably the Arduino Uno at around 18 pounds. I don't know many suppliers in the UK, so unless you have a favourite, I will use Element 14 or RS-Components as a reference.

[overkill]

Before I go designing the wrong solution, are you up for any electronics soldering? The relay option is looking cheaper than than the H-bridge but its more work to construct, while the bridge is very plug & play.

[Peadar]

Before I go designing the wrong solution, are you up for any electronics soldering? The relay option is looking cheaper than than the H-bridge but its more work to construct, while the bridge is very plug & play.

Hi again overkill,
I would be able to solder no problem but i dont have much time so plug and play is the way to go!

chatting to a lecturer today in college and he reckon arduino is the way to go, as it will be the most straight forward option for me so i dont get too tied up in the electronics. also recommended using a motor shield, im heading out to a supplier today to hear what they have to say.

What do you think of the arduino and motor shield option?

[Peadar]

Got the arduino uno and motor shield.
This motor rus at 32A at max load and 72A so i think i will need to operate a relay with the arduino?
any ideas?