Wheelchair guidance

ArduRover Miscellaneous
#21

Thank you, that is extremely helpful! Watching your videos now.

Rnet equipped chairs could use the PWM values as you described.

People willing to open up their non-Rnet wheelchair joysticks could add DPDT switches to select between the OEM wheelchair analog joystick module, or ArduPilot output with the low pass filtered PWM lines. Or in some cases, a pair of digital potentiometers.

With real outputs for throttle and steering servos, ANY chair with a physical joystick could use actual servos to move the joystick. As in this video RC Servo Controller for Power Wheelchair - YouTube with less precision of course.

It would be convenient for all these different use cases to share identical scripts, but a variation for specific digital pot is probably necessary.

#22

Donā€™t confuse the poorly named servo PWM output with the duty cycle based signals that are more accurately described by the PWM moniker.

ArduPilotā€™s throttle PWM outputs cannot simply be run through a low pass filter to approximate an analog voltage. They are servo/RC PWM signals, typically referenced by pulse width values in microseconds.

The video shows a method that could be connected directly to autopilot output.

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#23

Good catch.

I should have clarified in my case the line above refers to the Beagle Bone Blue motor outputs (2 pin, not servo) which I think are the kind of PWM which you can low pass filter to approximate an analog voltage. I could be wrong.

Digital pots would require yet a different wired interface depending on the chosen pot. I2C, SPI, UART, GPIO up/down

Then familiar hobby servo outputs with ā€˜not PWM, PWMā€™. Does anyone call that PDM(Pulse Duration Modulation)?

Iā€™m not clear on how these values are all interrelated inside ArduPilot software or Lua scripts, learning now.

It would be a somewhat trivial arduino project to make a peripheral translator board which converts between the different output formats. Of course, if doing that, I may as well make @ppoirier PWM/CAN translator too. But, with chips hard to get, and all the signal lines available on a FC, such a translator is redundant.

#24

I gotcha. I thought I might be over explaining but figured it might help others as well (there are several active topics with the same confusion).

The servo/RC signal protocol is almost always referred to as PWM, and itā€™s up to the user/use case to make the distinction.

I use such an Arduino on yet another project. It works well.

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#25

Sub decimeter GPS denied navigation will be useful, or required for negotiating elevators and doorways, so Iā€™ll keep an eye on your work. Is there anything critical to your work which you cannot lay hands on?

#26

When I refer to PWM , I generally mean the std RC signal (900-2000 msec)

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#27

It just occurred to me that the path through the code which was created by removing ToshibaCAN support could be reversed programatically and used to create a generic API for adding similar devices.

Not saying that would be useful for ArduPilot, I just never realized in general how prior code commits removing features could be a reverse engineering tool for adding features.

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#28

Indeed, as do I. Unfortunately, it becomes confusing to new users, especially those with basic familiarity with hobby microcontrollers, hence my pedantic explanation above.

#29

No offense, this is indded confusing,.
I think that canbus motor controllers offers a great opportunity for enhancing the ArduRover platform and opening the field of commercial robotic application, like AMR for example.

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#30

Absolutely agree. Thrilled to see this project moving forward, and hopefully using CAN!

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#31

Hi Dustin

Thank you

I managed to order most from Ebay and Aliexpress in January and am still waiting for components.

What I am waiting for are the motor mounts but am going to make some for the time being.

Just be careful the Beagleā€™s power side is a lot different from a PX4 etc

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#32

Hi All,
New to this thread and reading up on it now. I learned about it from slomobile on a YouTube discussion. I have been experimenting with a 6wd robot using wheel chair motors, and would like to add functionality to it. It is currently RC controlled and uses 6 Spark Max controllers to drive the dc gear motors. I also have other wheel chair and wheel chair parts, so I could possible help slomobile on this concept.
Scott