Trail Capable Mobility Vehicle

I’ve built a mobility vehicle utilizing two drive wheels, each with its own motor and brake (photos attached). The throttles are hall-effect “triggers” mounted adjacent to conventional brake levers, so each hand simultaneously controls a throttle and a brake to allow forward motion, skid-steering and braking. While effective, it’s proven too difficult for some to drive and I’d like to convert it to joystick control. Several people have suggested that I look into controlling it with an Arduino. I have little experience with electronics, and none whatsoever with Arduinos, so I’m seeking feedback here before investing time and money in that direction.

Apparently there are some issues with using a joystick. The 36v motor controllers are designed for 4v hall effect input, while the 12v linear actuator uses a 10k potentiometer. Furthermore, apparently what I want the joystick to do is not common… straight forward on the Y-axis would increase the throttle of both motors, but as the joystick is simultaneously moved on the X-axis it would reduce the speed of one or the other motor (skid-steer) while at the same time operating the linear actuator. In other words, motor speed would have to be controlled by both axes. I have a cumbersome mechanical solution that would use the existing hall effect sensors and pot, but I have a feeling an Arduino would make it much easier in the long run.

I’ve tried to find a consultant in northern New England who could spec everything for the conversion, but I haven’t had any luck. If this is a feasible application for an Arduino, is there enough support on this forum to get somebody with my limited knowledge and experience up and running?

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Furthermore, apparently what I want the joystick to do is not common... straight forward on the Y-axis would increase the throttle of both motors, but as the joystick is simultaneously moved on the X-axis it would reduce the speed of one or the other motor (skid-steer) while at the same time operating the linear actuator.

Except for operating the linear actuator, that is quite common skid steer behavior.

What does the linear actuator do?

If this is a feasible application for an Arduino

It is.

is there enough support on this forum to get somebody with my limited knowledge and experience up and running?

That depends on how much effort you are willing to invest, or pay for. Getting help with the code will be no problem. Trying the code will be up to you, since it is very unlikely someone here will have the same hardware to try the code on.

The rear wheels act as casters, swiveling nearly 180 degrees, and allow the vehicle to pivot around the contact patch of one front wheel. Unfortunately, the ability to swivel also makes the vehicle unstable as it wants to swap ends, particularly at high speeds, and will easily flip. I've built caster angle into the pivots and used gas springs to both center and damper the rear wheels, but it's just not enough to make it stable. The linear actuator will stabilize the vehicle, steering in conjunction with the skid steer of the front tires. I haven't tried eliminating the skid steer capability, but I'm quite certain it would significantly reduce the vehicle's maneuverability.

As for effort and expense, I have a full machine shop / fabricating facility and will purchase whatever components are necessary. But I need to know what to buy and how to program it.

FORD automotive has a speed sensitive power steering.
at low speed it is as sensitive and responsive as rack and pinion.

at highway speed you have to move the wheel quite a bit to change lanes.

if you ever get a chance to drive a Ford with this and then a rack and pinion, you will instantly notice the reason for this and how well the solution work.

if you added some sort of dampening on the casters, they could be very hard to change direction at higher speed and allow for that 'spin on a dime' dexterity that is desired when navigating hallways inside.

The rear wheels act as casters, swiveling nearly 180 degrees, and allow the vehicle to pivot around the contact patch of one front wheel. Unfortunately, the ability to swivel also makes the vehicle unstable as it wants to swap ends, particularly at high speeds, and will easily flip. I've built caster angle into the pivots and used gas springs to both center and damper the rear wheels, but it's just not enough to make it stable. The linear actuator will stabilize the vehicle, steering in conjunction with the skid steer of the front tires. I haven't tried eliminating the skid steer capability, but I'm quite certain it would significantly reduce the vehicle's maneuverability.

I think you have underestimated the requirements for a "trail capable mobility vehicle".
For starters, we can do nothing with the limited information you have provided. It is much too early to even talk about software as that is something that cannot be addressed until the hardware has been designed and fabricated. There is absolutely NO "Design Criteria" per se so your concept has not even reached the Feasibility Study stage, let alone the POC (Proof of Concept ) stage.
The sequence is as follows:
1- Create a "DESIGN CRITERIA" (it is pointless to proceed to the Feasibility Study stage without the Design Criteria because the whole purpose of the Feasibility Study is to ascertain if the Design Criteria can be met. No DC, no FS. No FS, no POC.
2- Feasibility Study : Research whether the Design Criteria can be met
3- POC: Design and build a Proof of Concept prototype for testing (per Design Criteria)
The fact that you have a vehicle says nothing about whether or not that vehicle meets the criteria,
as the criteria do not exist (have not been presented by you in any formal manner. Posting on the forum not constitute a Design Criteria. You can post the DC when you have created it. "Trail capable vehicle" does not constitute a Design Criteria. It is for you to define what "Trail capable vehicle " means by designing a test against which any possible candidate can be included or excluded. I don't see that yet so that description is essentially useless for all engineering purposes. Your idea of a " trail capable vehicle " may not meet any reasonable realistic criteria. That remains to be seen.

4- If you have a POC (and your photo of your vehicle on a trail is useless by the way) you need to prove it by posting a video of the vehicle navigating some trail. At the moment, the "STABILITY" issue seems to be an impasse. You have not quantified the definition of "stability issue " and the absence of any CLOSE UP PHOTOS OF THE UNDERCARRAIGE of the vehicle make any discussion of the subject heresay and academic. If you are serious about pursuing this you need to post a link to a YOUTUBE video that demonstrates "STABILITY ISSUE". To say that phrase is vague would be an understatement.
You need to first define STABILITY in concrete terms before you can entertain a discussion about any STABILITY ISSUE. What is YOUR criteria for STABILITY ? What is the "ISSUE".
Where is the video showing the "issue" ?

Provide a complete package of photos.
Provide a mechanical drawing with dimensions
Provide side view photos showing a vertical ruler next to some object of known dimensions , such as a golf ball, tennis ball, baseball, bowling ball etc.. to give an idea of the dimensions.
Post a Test Criteria by which any possible design candidate can be evaluated and included or excluded as a possible POC prototype.

As far as I can tell, you are not yet at the POC stage. You have an idea, a goal , a few very distant photos and no engineering criteria to speak of, certainly nothing that even remotely qualifies as "Engineering Specifications".
I really don't know how you expect us to answer the questions you have asked based on nothing.
As a comparison, I would recommend including a photo of YOUR vehicle compared to vehicles that have ALREADY been QUALIFIED a ALL TERRAIN VEHICLES (AKA ATVs) perfoming the test you design by which you intend to qualify YOUR vehicle. Having seen your photos, I would say you have not a clue what is required for a vehicle that is going to be on a "trail". Real "trails" have rocks and tree branches everywhere, not to mention uneven spots. Are you expecting us to accept a definition of "trail" that means a "hard flat dirt path that has been swept of obstacles and anything that might impede a wheel chair " ? To have any hope of success , you need to START with an ATV and modify it to accomodate you. Your vehicle wouldn't make it 10 feet on a "real ' trail. (IMO)

You can insert uploaded images by following these instructions.

Once you insert the images, I'll delete these.

Snapshot 2 (3-9-2015 10-23 AM).png

Snapshot 3 (3-9-2015 10-24 AM).png

Snapshot 4 (3-9-2015 10-26 AM).png

Now people don't have to download them to view them.

vmax:
Furthermore, apparently what I want the joystick to do is not common... straight forward on the Y-axis would increase the throttle of both motors, but as the joystick is simultaneously moved on the X-axis it would reduce the speed of one or the other motor (skid-steer) while at the same time operating the linear actuator. In other words, motor speed would have to be controlled by both axes. I have a cumbersome mechanical solution that would use the existing hall effect sensors and pot, but I have a feeling an Arduino would make it much easier in the long run.

I don't know how the linear actuator is used by you can have a joystick control motors any way you want.

Here's some code from this post showing how the x and y channels of a RC receiver are mixed to control two motors.

if (joystickX != previousJoystickX || joystickY != previousJoystickY) // if joystick has changed compute new speeds
  {
    speedPort = joystickY - joystickX + STOPPED_US;
    speedStarboard = STOPPED_US - (joystickY + joystickX);
    previousJoystickX = joystickX;
    previousJoystickY = joystickY;
    changeFlag = 1;
  }

A few years back I posted a description of how to do a dual-axis joystick controller for skid-steer (aka differential steering). Right below that post the OP of the thread implemented the code for my description and said it worked great.

Now - it didn't have any provision for a linear actuator - so you'd have to add that - but maybe that code can help you get started?

Lastly - I have a friend who might be interested in hearing from you about your chair. I work with him on occasion helping with his non-profit to refurbish and donate out mobility chairs and scooters to those in need. PM me if you are interested...

So "skid steer" (AKA differential steering is what you're calling the method used by tank track vehicles ? (lock one side and drive the other or drive both in opposite directions)
If the OP is trying to pivot then the linear actator is probably a centered vertical shaft that has a spike tip to dig into the dirt creating a pivot point for tge turn and thdn retracting vertically, disengaging with the ground, permitting forward motion.

Thank you to those who left useful feedback. I've decided to just go ahead and build a joystick that will manipulate the existing hall effect sensors and pot.

crOsh, I'll be in touch if I decide to take another look at an arduino solution.

If you don’t do a “reality check”, you’re going to wind up stuck on some trail in the boonies with a dead battery. Vehicles like yours do not belong on trails. I don’t know why you are blind to that. It’s an accident waiting to happen.

DuaneDegn:
You can insert uploaded images by following these instructions.

Once you insert the images, I'll delete these.

Snapshot 2 (3-9-2015 10-23 AM).png

Snapshot 3 (3-9-2015 10-24 AM).png

Snapshot 4 (3-9-2015 10-26 AM).png

Now people don't have to download them to view them.

is that photo now controlled by the forum ? or, if you change the photo will the new one be displayed ?
in FaceBook, only the link to the photo was used, the program pulled the photo from the link each time.
once the hackers found out about this, they would post pictures of puppies and such, then switch the photo and leave the original URL. then viewers were shown whatever the hacker wanted.
something I have been curious about.
also, since I host my photos on imgur, what happens to my photos if I loose the account or they end service ?

raschemmel:
If you don't do a "reality check", you're going to wind up stuck on some trail in the boonies with a dead battery. Vehicles like yours do not belong on trails. I don't know why you are blind to that. It's an accident waiting to happen.

I have to think that the use will be for less than flat trails that are on State Parks and such. places that such a chair can traverse.
and of course there is the manual override, right ?