Arduino controlled wheelchair

[woodygb]

http://www.teamtornado.co.uk/ssheet.htm
download this http://www.teamtornado.co.uk/data/motors.zip it includes a wheelchair motor in the examples.

[jcka22]

Okay I think I'm getting a better idea of what's necessary now.

I looked at some P&G controllers on eBay but they were around $100 and that wasn't with the joystick controls. Buying a different wheelchair control system and hacking the joystick doesn't seem like the most efficient way of doing this.

It seems like what I need is a good motor controller. And if I am going to get one, I'm probably going to need something more like this: http://www.robotshop.com/en/sabertooth- ... river.html

What do you all think? 60A continuos and 120A max should be sufficient. Something as small as 40A continuous would probably work, as long is it had a high max rating (~100A) right? Obviously this is a little pricey for me but if I could find something similar for a little less I could probably swing it.

It has over-current and thermal protection, are over-current protection and current limiting two different things?

Also, the previous PWM frequency was 20kHz, will there be any problem using something with a higher or lower frequency, like 16-24 kHz?

Maybe two of these could work? http://www.robotshop.com/en/cytron-sing ... oller.html

[woodygb]

One last try ...
http://www.ebay.com/itm/Penny-Giles-VSI ... 234ed70922

I've used the Sabertooth in my feather weight robot of 13kg .... it went pop.

[woodygb]

B.T.W the VSi is an all in one controller and joystick.

[Burgerman]

Not sure what you are using it for but non of these robot controllers have a suitable tank steer setup. Even the Roboteq required this script to make it steer correctly and be controllable and predictable:

http://www.wheelchairdriver.com/BM3-con ... Script.txt

Now I susspect that to get full control you would need that even on a robot. Or its all spin and zoom about. And turning depends on motor acc rates etc. Meaning you have to have acc/dec set up way faster than you will move the sticks or it has a mond of its own. That script works on the 150A per channel roboteq, as well as the smaller dual channel ones. And you will find out that you need this eventually...

[jcka22]

Okay, that listing doesn't really have much information, the controller looks pretty old, how can I be sure it will work for what I want to do? How do I know it's the right specs for my motors?

I'm assuming some of ya'll have used this controller in the past. The joystick is analog? So it would be relatively easy to program an Arduino to mimic the joystick signals and control the motors that way? Has anyone done this before?

[woodygb]

I have made an interface for the VSi ...both R/C and Android phone via Bluetooth .

Specs ...ask the seller ...

Suitability for your motors ... well it's I.M.O. more suitable than your other choices and can be reprogrammed .

[Burgerman]

Okay, that listing doesn't really have much information, the controller looks pretty old, how can I be sure it will work for what I want to do? How do I know it's the right specs for my motors?

I'm assuming some of ya'll have used this controller in the past. The joystick is analog? So it would be relatively easy to program an Arduino to mimic the joystick signals and control the motors that way? Has anyone done this before?
jcka22 Posts: 10Joined: 16 Feb 2015, 21:00

It is and Yes, yes and yes.

It also has proper control logic rather than simple tank steer which wont actually work for you, although you haven't found out why yet, and can be reprogrammed and configured. And includes such essentials as motor compensation so you get almost max torque at low input signals without requiring feedback from the motors etc, and will give controlled turns and speed independently. It also has current limiting and 101 other things you can set up and will require. You just need to program it with the software that's available free if you ask...

[DougL]

Hi,

I am new to this forum. I am looking to interface an Arduino board into an electric wheelchair. I found a little information on this site but couldn't find any information on actually setting this up and getting it working.

I'm not sure the brand of chair but it uses a Shark power module and control system. I know these chairs have a ton of safety features which makes it difficult to do projects like this.

Is it possible to keep the existing wheelchair circuit boards and somehow use an Arduino to control the wheelchair? Or would it be easier to just scrap all the control boards and start from scratch, keeping just the motors and batteries of the chair?

Any advice would be much appreciated !

Thanks,

Jack

Jack, I too went down this road and was not satisfied with getting into the physical joystick signaling so I built a logic analyzer from an FPGA board(Papilio - http://store.gadgetfactory.net/papilio-pro/ ) and figured out the protocol for the GC2 controller. What I like about this solution is it leverages the forward/reverse _and_ turning configuration built into the firmware on the GC2 controller. I just have to give it commands to move a percentage(0-100) forward, backwards, left and/or right or a combination. The controller firmware handles the _tank_ steering.

Search my name/ID and look at my posts. I've not yet setup a blog on this but plan to do so soon. I'm presenting to the local robotic club on this tomorrow night so there will be a fire under my butt to move on the blog.

Doug

[jcka22]

Okay burgerman/woody, what software? I would love to hear about it, thanks!

Doug, you did this with Arduino ? Or something else?

[DougL]

Doug, you did this with Arduino ? Or something else?

Yes, Arduino. An Adafruit Trinket Pro 5V to be exact and plugged directly into the 4 pin joystick pigtail off the base/controller.

[jcka22]

Doug - I don't think I have the type of wheelchair where I can do that.

I think my chair uses an inductive joystick, it's either that or Hall effect but I'm not sure how to tell. There are 4 coils like below on each side.

control board

IMG_4008.JPG (89.23 KiB) Viewed 16129 times

Why is it not possible to hack a joystick like this? Doesn't it still have to send some type of voltage signal to the processor based on the position of the joystick? Wouldn't it be possible to simulate this voltage? I can't figure out how this joystick sends the signals that dictate it's position. I've measured every chip on this thing and nothing changes voltage whether it's still or moving.

Does anyone know if it's possible to hack an inductive joystick?

[DougL]

If it is a hall effect type joystick then the signals for X and Y movement will be in the millivolts and a good amplifier would need to be used to see it on a general purpose multimeter. I could not find anything on the GSM555108 number I thought I could see in the picture.

What model number is on the joystick controller itself?

[LROBBINS]

The problem is not inductive vs. Hall effect, but whether it is an analog-output or digital-output joystick. I have both inductive (which yours is) and Hall effect analog sticks and they can be hacked in the same way. There are some controllers, however, (if I recall correctly the Dynamic Shark is one) that use a joystick with digital output (again, memory only here, SPI, but might be I2C). That is, the conversion from analog to a basic digital signal takes place inside the joystick. These two could be read with an Arduino, but you'd have to first figure out what SPI or I2C protocol is being used (clock rate and a few other things) and for that you'll need an oscilloscope or digital signal analyzer. For example, if it's SPI, you would program an Arduino (or other) with the same SPI protocol and connect 4 leads to the same points the stick is connected to in the pod. Most often those connections are called CS, MOSI, MISO and SCLK - you might even find those labels near your joystick's connections.
Ciao,
Lenny

[DougL]

if it were digitial then there would be something seen on a DMM even if it didn't make sense because it would most likely be TTL logic or CMOS(3v) logic. It would be easily seen on an O'Scope. The analog joysticks I read about many hacking generally were 0-5v with 2.5v center on both X and Y axis. So that would be easily identified. Now if it's hall effect type with sensing circuit off the joystick it can be tough to see the signals.

I'm not sure what the advantages would be to hacking directly into the joystick output as opposed to bypassing the joystick controller all together. At least on the low end joystick controllers with just 'dumb' battery level indicators, speed knob and a few buttons. All that can be replaced with an Arduino at the joystick pigtail since there is the raw battery connections there, the Prog/Inhibit line and the JSig/Ctl line. A DPDT relay could be used to switch in/out the either the Arduino control or the original joystick controller.

Doug

[jcka22]

Doug - You keep mentioning that you are bypassing your joystick. If you are doing this I am guessing yours does not use CAN communication? Since mine does wouldn't it would be nearly impossible to figure out how to communicate with the chair in this fashion?


Lenny - YES! That is exactly what mine has. See the picture below:

bottom of controller

IMG_4015 (1).JPG (57.51 KiB) Viewed 16099 times

How do I determine whether it's SPI or I2C? And once I know this, how do I go about programming the Arduino with the same protocol?

Thanks!

[jcka22]

Okay based on what I've read it seems to be SPI. Still not sure where to begin on how to program the Arduino. Am I going to need an Oscilloscope ?

[DougL]

Doug - You keep mentioning that you are bypassing your joystick. If you are doing this I am guessing yours does not use CAN communication? Since mine does wouldn't it would be nearly impossible to figure out how to communicate with the chair in this fashion?

Correct, the Jazzy Select and Jazzy GT models use a 6 byte serial bursts at 38.4K baud to send the x, y, throttle and unknown to the controller. I created a logic analyser from a $85 FPGA dev board( Papillo Pro ) and a $10 level shifter from the same company to do 5V TTL sniffing. The open source software I used OLS has a protocol analyzer plugin builtin which does the serial sniffing. There's I2C and SPI protocol plugins builtin too. I didn't see a CAN protocol plugin.

As for coding the Arduino, there's lots of libraries for Serial, SPI and I2C which probably work. I've used Serial and I2C myself.

Doug

[DougL]

Okay based on what I've read it seems to be SPI. Still not sure where to begin on how to program the Arduino. Am I going to need an Oscilloscope ?

A logic analyzer should do the trick but an O'scope will help you verify the logic levels. What I did was capture some data and look at it and guess at what it was doing. Then move the joystick a bit and capture the data and noticed 2 bytes changed. Move one axis on the joystick to max and notice what byte and value matched the movement. I did the same for the throttle setting. Then I did things like capture stream and the Inhibit line during power on and what they did when the power off occurred. I coded the Arduino to match the power on and power off sequence and sent out the joystick and throttle data at around the same 20mS interval as noticed in the captured data.

Doug

[jcka22]

Well that's good news that this is possible. Unfortunately I don't have a logic analyzer or an oscilloscope... It seems like even the low cost ones aren't cheap.

Would you be willing to share your Arduino code? I'll continue doing some research to see what I can find but it would be really helpful to see the structure of a working Arduino program.

[Irving]

Well that's good news that this is possible. Unfortunately I don't have a logic analyzer or an oscilloscope... It seems like even the low cost ones aren't cheap.

Would you be willing to share your Arduino code? I'll continue doing some research to see what I can find but it would be really helpful to see the structure of a working Arduino program.

Cheap usb logic analyser: http://www.ebay.co.uk/itm/Logic-Analyzer-24MHz-8CH-USB-Logic-Analyzer-/121283670158

Cheap usb scope: http://www.ebay.co.uk/itm/SainSmart-DDS ... 1195417252

These will do pretty much any hobby thing for Arduino or similar development...

[LROBBINS]

I have a Sainsmart DDS140. It's larger bandwidth (40 Mhz instead of 20) makes it suitable also for checking output of a 16MHz crystal oscillator - not enough to see much of a waveform, but at least enough to know it's oscillating. It also has a plug in 9-channel logic analyzer accessory that costs all of $15. By no means a Techtronics, but at $110 for the pair + $5 shipping, good enough for my uses. I've actually used the scope more than the logic analyzer as the logic analyzer alone isn't of too much use for looking at CAN messages, but seeing how clean the bit transitions are has been useful when designing the hardware. In your case, the scope would be useful not just for knowing logic level, but to figure out the SPI clock rate and which of several possible SPI modes is being used, but the logic analyzer would be easier for seeing message content. (Once you know the SPI paramters, however, you can also just use an Arduino to print out the data byte by byte.) CAN is rather different. CAN-HI and CAN-LO are not like tx and rx; it's the difference between the two voltages, or their equality, that says whether a bit is 1 or 0. Moreover, the CAN frame has a lot of bits stuffed in besides the message proper (part of what allows it to be such a robust protocol for safety-critical systems), and with either scope or logic analyser it can be a real chore to decipher frames from an "unknown" transmitter. For this, there are dedicated CAN "sniffers", but given that I know the bit rate of my nodes and they use a protocol that complies with the basic CAN standard, I just use another Arduino to serial.print the arriving data packets. I can, with great pain, actually read the raw binary from a dual oscilloscope trace, but it's certainly not something I'd want to do with any regularity. Cracking a proprietary CAN bus, such as Dynamic uses, would be no mean task.

A couple comments about trying to mimic an SPI joystick. I think that you will have a fairly steep learning curve ahead of you. I've used SPI for lots of things, but always with the Arduino as host that's interacting with some peripheral. What you will need to do is set up the Arduino as the peripheral (in substitution of the joystick) with the microcomputer in your pod acting as host. I think that can be done, but have never done it. Given that the pod electronics selects the peripheral to interact with by the "chip select" pin that it uses, you will have to break the circuit to the joystick or it will be very confused by having two peripherals (Joystick and Arduino) hooked to the same chip select pin. How hard it will be to find and break that trace on the circuit board I don't know. (The pin from your joystick that's connected to the processor's chip select pin is the one marked RST). Multiple peripherals can use the same MOSI, MISO and SCLK, but each needs its own chip select connection. Unless someone else has already done this, you will have a good bit of learning and work ahead of you. It can be fun, but best figure on some months of full-immersion. You might want to post a query on the Arduino forum, saying that you have a wheelchair joystick pod that has an SPI-output joystick and that you'd like to use an Arduino to mimic that joystick. Perhaps someone will be able to point you in the right direction (it wouldn't be amiss to also attach the photo).

Ciao,
Lenny

[gcebiker]

Ive just ordered a "Bus Pirate" from Dangerous Prototypes.

http://dangerousprototypes.com/bus-pira ... spi-guide/

I am hoping to do semi the same thing,

Sniff the data from factory joystick, then emulate it.

===emulator===
Wireless Nintendo Wii Nunchuck 2.4Ghz and receiver as 'the joystick'

Wii Nunchuck Receiver plugged into Arduino which takes Nunchuck Data and converts it to 'Shark Controller' Language to drive chair.

Ive been using the Wii Nunchucks to drive my Sailability Access Dinghy...run down on that here...http://sailabilitygc.org/wireless-control-for-access-dinghies-and-bigger-boats/
=============

Hopefully i can then use the power chairs motor drivers.

I'm in a power chair and would like to go fishing in a boat...on my own.
I aim to tow a light boat with my power chair to a local ramp, thow myself in the boat and then drive the chair via the Radio Control link up the ramp and park till i come back.
Reverse the process when i get back from fishing, drive the chair and attached boat trailer down to the ramp, load the boat on, get back in the chair and drive home.

[Irving]

Cracking a proprietary CAN bus, such as Dynamic uses, would be no mean task.

I have a PicoScope 3205, 2 channel 300MHz usb scope. ok its a tad more expensive, 300gbp 4y ago, but it has full CAN analysis plus many other protocols built into its software

[DougL]

Have you communicated with this guy( http://gizmosmith.com/ ) or at least checked out his blog on hacking the Shark/Dynamic protocol? He'd got as far as reading the messages and trying to simulate them. He didn't get responses from the base/controller and gave up for completely swapping out the controller but hearing how you want to use your chair, that wouldn't be the best solution. Search his blog for the word (Shark) and you'll find all his blogs on hacking the controller. It doesn't look too unlike what I got on the Jazzy base, ie a burst of a few bytes of data used for control. His problem could be with simulating the initial handshaking. I too had the control stream figured out but my software emulation wouldn't work until I got the initialization sequence correct. To get that, what I did on the Jazzy was to bring just the joystick to my bench, connected the logic sniffer up, set it to record and then gave it power. I recorded that and I recorded what happened when I pushed the power button on the joystick.

Another thing I did to see if my control stream was correct was to bring the control lines to a jump board so I could bring the base controller and joystick up as they naturally expect and after the pair were communicating and working I did a quick swap of the control lines so that my arduino software was now the one sending the control stream. Doing this verified I had the control stream correct and I had to work on just the initialization. But, since you want to keep the joystick on the chair anyways.... you could be done here since you could put in analog switches to switch your remote control system on/off for moving the chair up the ramp. But it might go into auto-off and then you'd need some handshaking to wake it back up to get it back to the water's edge.

Maybe there's something you'll see that he didn't as we know, new sets of eyes on things see different things.

Doug

[gcebiker]

Have you communicated with this guy( http://gizmosmith.com/ )

Doug

Hi Doug, ill definitely check that out.

I had thought to ditch the factory controller (or at least disconnect it) whilst fishing.
...its to tempting to a wandering person ...seeing an unoccupied wheelchair, taking it for a spin and then ditching it

Would you have a post of the Arduino code you used over on the Arduino.cc forums ?

Adapting your code to work wireless is not much of a stretch, I'll just need to snoop the address for the NRF24L01+ or Wii Nunchuck RX so that i can put both on the same I2C bus.

...Or i could use a Pololu Wixel with its built in TX / RX ? Ill need to do a bit more reading to figure out what i'm going to use.

[gcebiker]

This is a wixel https://www.pololu.com/product/1336, i think its basically arduino code, i smoked the first one i bought


Link to Gizmosmith's blog article for those on mobile devices.
Reverse Engineering the Dynamic Controls Shark Joystick
Further Hacking of the Shark

[DougL]

Looks great and seems like it could be a good radio setup to use. There sure looks to be enough digital I/O and analog inputs.

And the Shark hacking link/page clears up the protocol questions by stating it's really just a differential serial link and nothing more. My hacking turned up that 38400 baud, a standard baudrate, was sufficient for bursting the 6 data packets(bytes) protocol used to get the Jazzy Select joystick hack working. Maybe the Shark uses the same methods and it too will accept the 38,400 baudrate messages with just a few changes to the byte sequence and byte count from what I used. I PM'ed you the code.

This is VERY good news and I feel optimistic that a working solution can be found.
And if it does work, I'd like to work on incorporating the new initialization sequence(if there is one) and the new byte/message pattern into my original code so other users can just select a flag at the beginning of the code to select their controller/joystick protocol.

Doug

This is a wixel https://www.pololu.com/product/1336, i think its basically arduino code, i smoked the first one i bought


Link to Gizmosmith's blog article for those on mobile devices.
Reverse Engineering the Dynamic Controls Shark Joystick
Further Hacking of the Shark

[Vitolds]

what for to crack MK 5?
you need
1. Invacare DK-PMC28 Wheelchair Control Module MK6 90 http://www.ebay.com/itm/Invacare-DK-PMC ... 419a727f8c

2. INVACARE JOYSTICK MK6 () http://www.ebay.com/itm/INVACARE-JOYSTI ... 3f4f8d87d3

MK 6 Joystick - 4-wire, simple

[gcebiker]

Looks great and seems like it could be a good radio setup to use. There sure looks to be enough digital I/O and analog inputs.

WoW Doug, a very sincere thank you for the code.

I've spent my day going thru my stockpile of stuff and reading a lot, leaning a little bit (most of it way over my head)

Can i use what i have ?(save a few $ in hardware costs)

Ill try to sum up where i am at so far.
1. Need input device (Wii Nunchuck is nice form factor for this)
2. My brain injury gives me the gift of seizure / passing out when learning. (use available apps where possible to limit sleepy times)
3. Arduino has huge support base, staggering really (Dougs work top of that list for this endeavor.)
4. Arduino (with out faffing about) has one SPI bus (multi spi devices can be used but there's got to be a simpler way ?)
5. Wixel, they have two UART's and built in radio..BUT nothing of the support base the Arduino has, and there own support team advises Programming Noobs to interface an Arduino with their wixels ?? Seems a bit redundant for a company to make a great product but make it so that its not able to access the mind boggling resources of the Arduino world. /shrug /meh


6. An (ultimate) plan comes together (....if i had mad skills)
INPUT = Wired Wii Nunchuck (thumb joy, good form factor, three buttons, accelerometer, SPI)...and there already exists code (and ive used it successfully)
DECODE SERIAL Wii Data = TX Wixel
TX (Transmit) Wixel = Wixel transmit data using inbuilt radio to
RX (Receiver) Wixel = Wixel converts data to Dynamic Wheelchair code

7. I dont have mad skills... (dont reinvent the wheel)
Use what i have on hand http://sailabilitygc.org/servo-city-wireless-joystick-using-nrf24l01-2-4ghz-radios/
Doug's code uses a wired input, so ill do the same (to start off with), wired inputs from Servo City Joystick - Arduino take inputs and output SPI data to Shark Joystick.

8. If i can pull that off, then i start on the wireless version. I'd Love to use the http://gcduino.com/learn/gcduinode/
Then it would be wired input, GCDuiNODE to tx, GCDuiNODE rx , Arduino Nano for RC to SPI conversions (its still a bit messy tho i feel, I wish i could do it with only two Arduino's).

Arduino Master with 1+ spi devices http://forum.arduino.cc/index.php/topic,19770.0.html

For anyone asking the question in their heads - i want to use the chair i am sitting in now
Its my favourite chair (yep been plenty others) and i have the DX software and Dongle here with backups of the program in use.
Software has been tweaked to meet my needs (no safety input lag)
I dont have the luxury of being able to take it appart and a plug into the charging port is much cleaner.

Again thank you Doug, your info has given me a big head start and ill be sharing as i get some solid results.