I was asked to look into designing and building a joystick controlled steering system for a 2700lb electric vehicle(I am mechanical engineer). I started thinking servo or stepper motor turning the shaft on the rack and pinion right away. Then I started to complicate it. I thought the tire should not only turn with the movement of the joystick but also match the velocity. I also thought if the joystick was released the tires should return to center. I know that is should be doable. I figure that I need a analog joystick, a controller/driver,a servomotor and possibly some limit switches, oh and a little programming.

Why am I posting this? I am a mechanical engineer. I'm not as smart as you electrical guys/gals. I don't want to reinvent the wheel if it is not necessary. I know that joystick systems already exist for car but they are expensive. This is a prototype vehicle. I rather not burn through the budget on this. Any recommendations on components would be greatly appreciated. If you are familiar with any user friendly controller that would work for this application, I would be delighted. I'm not great at programming but I am capable.

I would like to thank you all ahead of time. I look forward to spit balling this with you all.

I have 12V, 24V, and 48V systems as possible power supply.

 

I did that one time on a giant fork lift for hauling boats. A replacement steering gear was no longer available so I used the existing hydraulics with a left - right valve with a long handle so it wouldn't be too sensitive.
Even at slow fork lift speeds, it was very awkward and hard to control.
It might have been better with a return to center feature.
Edited to say:
After thinking about this, it didn't follow the position of the lever. It just jogged the angle of the steering left or right and was easy to overshoot the angle that you wanted.

 

Firstly, you may want to consider the application, and any implied safety guidelines or mandates. A simple DC motor with positioning feedback to a referenced driver will do the job. If your joystick self centres upon release, the drive will follow that reference. The motor in turn could drive a ball screw, a closed loop hydraulic pump, etc.

 

I hadn't really considered an electric over hydraulic system. There are currently no hydraulics on the vehicle. The power steering is an electric system.

Ultimately, I am concerned with the overall functionality. I can make the tires turn, no doubt. Mirroring the response of the joystick, both in speed and position, is the crux of the matter. I think a return to center is a must to prevent constant oversteering, as you mentioned DNA.

I had planned to use a standard analog joystick. I am a little concerned that an analog input may not be smart but the other options are a little out of my wheelhouse. I never done anything but analog inputs.

I can get it done. Any advice on hardware components like controllers/drivers, joysticks, hell even motors would be welcome. Later today, I'm going to dive a little deeper in this. Hopefully, I should have real numbers.

Again, thanks for any input.

 

Now I'm confused. Is there already an electric power steering system in place?

Matching the velocity of the joystick is a function of the power of the steering motor. If you are replacing something with a steering wheel that takes at least a couple of turns limit-to-limit, it is not reasonable to expect the steering to keep up with the velocity of a joystick which can easily be at least an order of magnitude, possibly two, greater than anything you'd ever accomplish with a wheel, even with a spinner knob. Keeping up with a joystick is a recipe for rolling the vehicle.

 

You're right, matching the speed would be a bad idea, but a proportional safe varying speed maybe? I would just like to mimic the feel and response you would get with a standard steering wheel.

Yes, there is an electric power steering unit. It uses a torque sensor of some sort. I considered using the motor/gearing but decided against it. The power steering only reacts to the torque on the shaft, it has no way of knowing where it is at in space.

 

Don't know what your vehicle is, but most wheeled vehicles use caster to return them to center and keep them centered while moving. Caster is a common setting for wheel alignment.