I’m trying to better an all mechanical steering assembly by utilizing a high speed linear servo. This would eliminate a notorious weak point in the linkage. Parameters;
Servo needs to be fast
Around 10 inch throw
Around 50 lbs force is required
It needs to communicate with a steering column -180 to 0 to 180.
I look forward to your responses and I’m sure you’ll need addition info, I’m just not sure what to provide.
I forgot to mention, it will be ran off a 12vdc system. Thanks!
Did I post this in the wrong section?! I figured this would have had 10 suggestions by now.
@silverlake951Welcome to the RobotShop Community. To confirm, when you mention “linear servo”, you are looking for a closed-loop geared stepper motor with a lead screw? At the moment RobotShop doesn’t really offer these. The only comparable would be geared DC motor based linear actuators, and some include linear potentiometer feedback:
In terms of “communicating” with a steering column, this seems like it might require some additional explanation as most passenger vehicles which are made to be autonomous use the existing steering and rotate the steering wheel, rather than modifying anything internally. Automotive companies and their research partners (ex. university research programs) are able to adapt existing motorized steering on modern cars, though it’s again rare that they replace any existing components.
One of the main reasons you have not had many responses here is that people with experience modifying passenger vehicles is far less than those looking to learn about, say, creating a 2WD desktop rover.
Thanks for the response! Thus far, here’s what I’ve come up with. I think I’m going to use a servo motor rather rather than stepper. Initially I was thinking along the lines of a linear motion, but I’m not entirely sure that’s necessary. I’m going to pair that with a potentiometer and arduino. I won’t be modifying the currently steering column, I just need a way to input the analog signal from the column to the servo so that the servo moves when the steering moves. You can tell I haven’t done much of this work, trying to learn. Ultimately , the servo will be slave to the steering column, mirroring its movements.
Can you perhaps give more information about the project itself?
Absolutely, it for a Jetski. There is mechanical linkage from the handle bars to the nozzle. In short, the handlebars are firmly fastened to the steering column, and semi flexible steering cable attaches the steering nozzle and steering column. This cable passes through a bulkhead and meanders thought the engine bay. The cable is what fails. I want a potentiometer to read at the steering column and relay the handlebar position to the servo. The servo will be mounted where the cable passes through the bulkhead, I will replace the cable with a rod. The rod will connect the nozzle and the servo. Hopefully this paints a much clearer picture. Thank you
How much waterproofing is needed? Rather than force, you’ll need to calculate torque for a servo. Provided you’re not changing the throttle setup, it seems relatively safe if there’s a failure (you lose steering, but it won’t stay at full throttle for example).
It’s as safe as when the linkage breaks in its current state haha. It happened three times this past summer. I will say, it needs to be pretty waterproof. It will be sitting low in the hull and these machines inherently take on lots of water.
That becomes problematic using DC motors; corrosion, short circuiting etc. You’ll need to think that one through since simply sealing it might also trap the heat. Last, keep in mind most DC motors have a low duty cycle of around 25%.
A thought for sure, but Rc boats use dc servos without issue.
I might be wrong, but the handle bar does not produce a linear motion in it’s standard setup. More like a sinewave?
It would be a weird steering experience, if you’d read the handle bar angle and control the servo 1:1
just my 2 cent
o_lampe
