WheelchairDriver

Hi, I am currently a Year 3 Student doing a Final Year Project that requires us to hack the P&G VSI 50A controller and I was wondering anyone here has the schematic or joystick connect for it. I was also wondering how to hack the controller as we are replacing it with another control.

Define "hack"?

What exactly are you attempting to achieve?

And to DO what? With what?

In a nutshell, I am trying to hijack the signal of the controller so I can replace it with a sensor. What this project is trying to do is help people with cerebral palsy gain motorized control of their powered wheelchair, and in order to do so we have to replace the joystick as people with CP have lack of hand movement and control so replacing it with an alternate controller will help them learn how to drive a wheelchair with more ease and convenience. So I am trying to find either the schematic of the controller or joystick of P&G VSI 50A in order to hijack the signal and replicate a similar signal to the alternate controller.

The VSI almost surely uses one or another serial protocol to communicate with the rest of the system and hacking that may be a tall order. It may be much simpler to make an adapter that connects to the same leads as the joystick pot and mimics the joystick output. Do a search here for postings by woodygb to see how he's done that for using RC controllers to mimic other joystick controllers - yours will be similar. Years ago I had done something similar just using 4066 ICs connected to head and foot switches to select among a set of simple voltage dividers, but Woody's way is a much more flexible solution.

I would agree w/ Lrobbins about the easiest method being to mimic the joystick.

I'd also point out that while I am not sure what is available for the VSI series (which are pretty much the 'lowest grade' controllers for use on low-end chairs, w/ 50A being really low-end) there are a lot of existing alternative input devices available for the better series of controllers like R-net, etc....

While possibly interesting as a 'learning exercise' I'm not sure how practically useful this would be as a project.... It seems likely to me that a CP (or other disability) user with enough functional challenges not to be able to use a regular joystick is probably going to be needing a more sophisticated (i.e. multiple seating controls) rehab chair than the very basic sort of chair the VSI series controllers are designed for.

ex-Gooserider

For e.g. These things and others are all compatible with the r-net system. And other high end fully programable rehab control systems.

http://switchit-inc.com/wp-content/uplo ... atalog.pdf

ex-Gooserider wrote:I would agree w/ Lrobbins about the easiest method being to mimic the joystick.

I'd also point out that while I am not sure what is available for the VSI series (which are pretty much the 'lowest grade' controllers for use on low-end chairs, w/ 50A being really low-end) there are a lot of existing alternative input devices available for the better series of controllers like R-net, etc....

While possibly interesting as a 'learning exercise' I'm not sure how practically useful this would be as a project.... It seems likely to me that a CP (or other disability) user with enough functional challenges not to be able to use a regular joystick is probably going to be needing a more sophisticated (i.e. multiple seating controls) rehab chair than the very basic sort of chair the VSI series controllers are designed for.

ex-Gooserider

I am asking for the specific schematic of the P&G VSI 50A as this model of controller is already built into the powered wheelchair my polytechnic is purchasing. So I'm just wondering how do I hack it and replace it. I am part of the motor control aspect and 2 of my other teammates will be researching on which controller will suit patients with CP best, one of them is doing digital controller while other is doing analog.

I cant help and I doubt anyone can. They dont publish such things.

I can tell you though that any powerchair with that controller is going to be unsuitable for a user with CP. Or in fact any serious disability.

This part baffles me.

I was also wondering how to hack the controller as we are replacing it with another control.

Then do exactly that. Throw it away its a toy. Fit something better. What is it about that that needs "hacking"...?

What does one doing digital and one doing analog mean?
All controllers are pulse width control of current to motors since halfway through last century. And most mobility controllers use dc and analog for joystick input. What EXACTLY are you trying to do?

And why are you wanting us to do your homework for you?

Maybe tell your polytechnic not to waste its cash on this chair and buy one that's more likely to be currently in everyday use. That way somebody might actually benefit from your research.

It also wont need "hacking" whatever that actually means as there are various inputs on add on modules that allow an external device to control a chair. Such as the Omni device, or the IOM which allows me to drive by RC etc.

greybeard wrote:Maybe tell your polytechnic not to waste its cash on this chair and buy one that's more likely to be currently in everyday use. That way somebody might actually benefit from your research.

Guys, this specific wheelchair model that includes the P&G VSI 50A is the one CPAS (Cerebral Palsy Alliance) uses at their center daily for their patients, so we are purchasing the similar wheelchair the patients uses and is trying to make improvements (aka replacing the P&G VSI Controller).

Burgerman wrote:I cant help and I doubt anyone can. They dont publish such things.

I can tell you though that any powerchair with that controller is going to be unsuitable for a user with CP. Or in fact any serious disability.

This part baffles me.

I was also wondering how to hack the controller as we are replacing it with another control.

Then do exactly that. Throw it away its a toy. Fit something better. What is it about that that needs "hacking"...?

What does one doing digital and one doing analog mean?
All controllers are pulse width control of current to motors since halfway through last century. And most mobility controllers use dc and analog for joystick input. What EXACTLY are you trying to do?

And why are you wanting us to do your homework for you?

First off, I was trying my luck by posting if anyone had the schematic.

Secondly I did not say I was using that controller for the patient with CP. Patients with severe physical disability or CP does not have the fine motor skill to control a joystick, thereby we are REPLACING IT with a alternate controller (4 button switch)

What needs hacking? I can't simply "throw it away" and put a new controller on it. I have to find the exact signal the P&G gives out to the motor module so I can replicate that signal to the new controller.

What exactly am I trying to do? Well my team and I are trying to tackle this problem statement "Alternate Drive controller (ability switches to drive powered wheelchair)". We are trying to replace the joystick with a controller that proves more suitable and easier for patients with CP to learn and in short, provide a enhanced opportunity for patients deemed infeasible to learn powered motor control.

Lastly, if you think I am asking you to do my homework, that's just outright hilarious. I am here on a forum to learn more about my project and ask for advice. If it comes across as "asking you to do my homework", you may leave. No one is forcing you to reply to this discussion or post. Thanks.

If you are not careful, you may be the one to leave!

You were already told how to do that alternate input above by several others. Many here have done it in order to drive by radio control etc including myself. You wont get hold of any better information as it doesent exist outdside of PGDT. And they certainly wont give you it.

What you need already exists. Including the four button switch input. Its called the R-net omni. It allows digital, or analog external inputs,very customisable programming inc latched etc, and is designed for exactly what you are doing. Theres also an IN/OUT module. For similar external custom control systems. You are reinventing the wheel. And trying to do it to the wrong low end control system. The easiest solution and the best in the end is to explain to those that chose this wheelchair that its the wrong one. And to select one that uses a R-net control system so that an external custom controller such as your 4 switches can be easily integrated. And have far greater programability with the controls too. And adequate power to boot.

What you want is one of these. http://sunrise.pgdrivestechnology.com/m ... 813-07.pdf It does exactly what you need. Already. Only with 20 years development and refinement built in. Theres a pilot plus Omni, an Rnet old style omni and a newer very compact one. All plug and play alternative inputs.

The newVSI controller pictured is an all in one brain and joystick pod. No talking backwards and forwards from it to a separate controller.

I'm guessing you are in Singapore where this appears to be the commonly used control.

The simplest version of what it sounds like you want to achieve is 4 buttons:
1. Forward - both motors forwards
2. Backward - both motors backwards
3. Rotate the front of the chair to the right - left motor forwards
4. Rotate the front of the chair to the left - right motor forwards

I would have all buttons only work by themselves. Push one for a command to happen. Push two or more and nothing happens.

It may be better to have the left and right aiming send a time limited burst of power to the motor so one click turns 5 degrees for example rather than having the chair rotate forever if the button is held down.

One thing you need to be very aware of in an example where the driver doesn't have full ability is that an electric wheelchair can exert a lot of force on the person in a situation where they catch their leg against furniture or the wall. Broken bones happen very fast and heal very slowly.

Burgerman wrote:If you are not careful, you may be the one to leave!

You were already told how to do that alternate input above by several others. Many here have done it in order to drive by radio control etc including myself. You wont get hold of any better information as it doesent exist outdside of PGDT. And they certainly wont give you it.

What you need already exists. Including the four button switch input. Its called the R-net omni. It allows digital, or analog external inputs,very customisable programming inc latched etc, and is designed for exactly what you are doing. Theres also an IN/OUT module. For similar external custom control systems. You are reinventing the wheel. And trying to do it to the wrong low end control system. The easiest solution and the best in the end is to explain to those that chose this wheelchair that its the wrong one. And to select one that uses a R-net control system so that an external custom controller such as your 4 switches can be easily integrated. And have far greater programability with the controls too. And adequate power to boot.

What you want is one of these. http://sunrise.pgdrivestechnology.com/m ... 813-07.pdf It does exactly what you need. Already. Only with 20 years development and refinement built in. Theres a pilot plus Omni, an Rnet old style omni and a newer very compact one. All plug and play alternative inputs.

So in order to hack the signal I have to use radio control? How exactly would I do that since my teammates motor control switches are DIY, do I get a adapter?

foghornleghorn wrote:The newVSI controller pictured is an all in one brain and joystick pod. No talking backwards and forwards from it to a separate controller.

I'm guessing you are in Singapore where this appears to be the commonly used control.

The simplest version of what it sounds like you want to achieve is 4 buttons:
1. Forward - both motors forwards
2. Backward - both motors backwards
3. Rotate the front of the chair to the right - left motor forwards
4. Rotate the front of the chair to the left - right motor forwards

I would have all buttons only work by themselves. Push one for a command to happen. Push two or more and nothing happens.

It may be better to have the left and right aiming send a time limited burst of power to the motor so one click turns 5 degrees for example rather than having the chair rotate forever if the button is held down.

One thing you need to be very aware of in an example where the driver doesn't have full ability is that an electric wheelchair can exert a lot of force on the person in a situation where they catch their leg against furniture or the wall. Broken bones happen very fast and heal very slowly.

Thanks for your advice and yes I am from SG.

No, you don't need to use RC. What you have to figure out are the X and Y voltage swings of the joystick pot inside the controller and make a circuit that mimics that. (One exception to this that I know of is the Dynamic Shark series which uses an digital rather than analog joystick pot.) That will be MUCH easier than trying to hack the serial digital signal (which may be of any one of a number of different protocols with a proprietary "dictionary" for the messages).

I might add that once you figure out how to immitate the stock joystick dc voltage swings, reference voltage etc, to be able to control the chair without the joystick. That you will need to be able to interface with the your new control system, then you will come across several new problems.

ONE of these is that that in order to travel in straight lines and go where intended, rather than influenced by where the casters are pointing or need to change position, or influenced by carpet pile, or lateral slopes outdoors for water drainage on footpaths and roads, that you will need either a finely tuned gyro system, or a wheel encoder setup. Because it certainly will not go straight just because you tell it to do so. The stock motor load compansation algo isnt capable of this. The R-net system you should have started with, already has all required modules and firmware/software available to do this as part of its more advanced system. These are very much required if your system is to be any real help to an end user with only 4 buttons and no ability for steer correction in the usual way. Dont believe me? Try using a MANUAL wheelchair along a road edge. And THEN you will understand the problem. Right now you dont.

https://www.cw-industrialgroup.com/Prod ... ions/R-net System.
https://www.cw-industrialgroup.com/Prod ... -Interface omni for your speciality input control system.
https://www.cw-industrialgroup.com/Prod ... der-Module encoder module for accurate straight line tracking regardless of obstacles and wheel load.
https://www.cw-industrialgroup.com/Prod ... yro-Module gyro, acomplishes much the same thing.

All the settings and programming of these parts (modules) is built in to the system and can be configured with the OEM level programmer.

This is one of the many reasons that you are starting with the wrong system... Just for information. Your project has rather a long way to go to match what you should already be using as a starting point. I suspect a lot more than a couple of years at school as a project will accomplish.

LROBBINS wrote:No, you don't need to use RC. What you have to figure out are the X and Y voltage swings of the joystick pot inside the controller and make a circuit that mimics that. (One exception to this that I know of is the Dynamic Shark series which uses an digital rather than analog joystick pot.) That will be MUCH easier than trying to hack the serial digital signal (which may be of any one of a number of different protocols with a proprietary "dictionary" for the messages).

Well the controller that I am trying to hack is analog as it has speed changes and also how exactly do I figure out? Do I use a multimeter and oscilloscope to gauge the voltages and the graph?

Burgerman wrote:I might add that once you figure out how to immitate the stock joystick dc voltage swings, reference voltage etc, to be able to control the chair without the joystick. That you will need to be able to interface with the your new control system, then you will come across several new problems.

ONE of these is that that in order to travel in straight lines and go where intended, rather than influenced by where the casters are pointing or need to change position, or influenced by carpet pile, or lateral slopes outdoors for water drainage on footpaths and roads, that you will need either a finely tuned gyro system, or a wheel encoder setup. Because it certainly will not go straight just because you tell it to do so. The stock motor load compansation algo isnt capable of this. The R-net system you should have started with, already has all required modules and firmware/software available to do this as part of its more advanced system. These are very much required if your system is to be any real help to an end user with only 4 buttons and no ability for steer correction in the usual way. Dont believe me? Try using a MANUAL wheelchair along a road edge. And THEN you will understand the problem. Right now you dont.

https://www.cw-industrialgroup.com/Prod ... ions/R-net System.
https://www.cw-industrialgroup.com/Prod ... -Interface omni for your speciality input control system.
https://www.cw-industrialgroup.com/Prod ... der-Module encoder module for accurate straight line tracking regardless of obstacles and wheel load.
https://www.cw-industrialgroup.com/Prod ... yro-Module gyro, acomplishes much the same thing.

All the settings and programming of these parts (modules) is built in to the system and can be configured with the OEM level programmer.

This is one of the many reasons that you are starting with the wrong system... Just for information. Your project has rather a long way to go to match what you should already be using as a starting point. I suspect a lot more than a couple of years at school as a project will accomplish.

What do you mean I am starting with the wrong system? I am starting with this controller as it is BUILT IN and either way I am replacing it with my teammate's DIY control switches. So you recommend me getting this R NET System for steer correction? Is getting this system a must?

I think we need to accept that this is just a learning project for students rather than an attempt to find a solution to the problems a person with Cerebral Palsy might have when trying to use a powerchair.

nani13, you are trying to make something that already exists. There is already a full system for people with restricted movement. That R-net system has been here for a long time.

He has been tasked with creating a new interface to replace the joystick on the P&G VSI 50A controller. So what exactly does the joystick do? How does it create an output that can be used by the power module? How can that joysticks output be emulated?

Those questions have already been answered in this thread? Once you get it all figured out you should be able to hook up your emulator to use electroencephalography.

Dan wrote:I think we need to accept that this is just a learning project for students rather than an attempt to find a solution to the problems a person with Cerebral Palsy might have when trying to use a powerchair.

nani13, you are trying to make something that already exists. There is already a full system for people with restricted movement. That R-net system has been here for a long time.

He has been tasked with creating a new interface to replace the joystick on the P&G VSI 50A controller. So what exactly does the joystick do? How does it create an output that can be used by the power module? How can that joysticks output be emulated?

Those questions have already been answered in this thread? Once you get it all figured out you should be able to hook up your emulator to use electroencephalography.

I agree that this is a learning project but I think it is as real as it can be. As a team we have met with the CP alliance of Singapore discussing what the patients need/prefer, since their hand movement is limited they need big buttons to push for each direction. But I am also unsure and this might just be a learning project as real solutions exists out there.

I have severe athetoid CP and can use a normal joystick mounted on my right footplate, I can drive the chair with my right foot. The simplest joystick pod for this is the Pilot+ Chin control which has two switch stalks that can be lowered or raised. Some CP users use head switches.

Steve

What do you mean I am starting with the wrong system? I am starting with this controller as it is BUILT IN and either way I am replacing it with my teammate's DIY control switches. So you recommend me getting this R NET System for steer correction? Is getting this system a must?

Not sure what you mean by "built in". Its a ONE PART system. Its JUST the joystick pod. If you unplug that joystick and remove its two mounting screws then its no longer built in! The whole system is in your hand. So when you say you are replacing it with yours, then theres nothing left! Just batteries and motors. So replacing with yours makes no sense!

The problem with it is that:

1. Its all built into the one component. There is just one board. Theres no seperate power module anywhere.
2. Its super low powered. So much so that it will not likely be able to climb a threshold, or turn in place reliably without the user correcting it with manual control corrections. As such you need a better more powerful system for reliable control.
3. It got zero flexibility. No inputs, outputs or any advanced control programming that would allow use of your switches properly.

The R-Net system is designed to have many modules and advanced programming to make use of switches to drive etc. And its got enough power, programability to configure your switches, gyros and encoders etc to make driving with switches work properly. Inc latched control, timers, menu control, etc.

So it depends. Are you doing this to make a proper powerchair for the benefit of the user? In which case you really need a different chair AND a different control system such as the R-Net system. Or at very least fit an r-net control system.

Or are you just messing around to try and complete a student project to pass some exam and or learn stuff? In which case carry on as you are and you will learn all the things that you dont know now. And then you will understand why I say these things. Because doing what you are doing with that cheap basic system will never be useful. It might also be dangerous. You need many fail safe systems in place to prevent a fault or a user driving under a bus or breaking legs.

The difference between us is that I have 60 years of doing this stuff. And a vast store of learned solutions, know a lot of things that you dont already! Because I made all the best mistakes several times over before you were born! You have no experience to call on.

So what you do depends on the real purpose. To help an end user or to learn from a project?

This is ALL there is on that chair. Its self contained. This is both the joystick and the power module. All in one. When you remove it, all thats left are batteries and motors.

At which point you have nothing left to interface your switches to.

That chair probably also has small, low power, 2-pole motors that might not withstand 120A draw and will not produce enough torque at currents they can stand to give good motor compensation (with or without an encoder). That was certainly the case with Rachi's original anemic Fracmo motors, even with caster angle sensors added. Once I'd changed the motors to much better ones, motor compensation worked well even with the sensors removed and even though it's front wheel drive. Turn in place remained a problem because it has far too much weight on the rear casters.

To see what the joystick pot does you have to open the case and find the wires that go from the joystick to the circuit board. If it's an analog joystick pot it will have one that's + supply, one that's ground, one (or two) that's a center tap half way between those, one (or two) for X output and one (or two) for Y output. The "or two" is because some pots have duplicate outputs that are used as a safety check that it's functioning correctly. Some fancier pots also have a separate output that is switched on when the stick is centered. Each output will = the center tap voltage when the stick is neutral and have a swing above and below that when the stick is moved. If there are two outputs for X (and for Y) they may swing in the same direction or swing in opposite directions. Chances are that this controller has the simplest pot available with just 5 wires: +, -, center, X and Y. In any case all you need to find out is a half-way decent voltmeter (and great care not to short anything when you are figuring it out). If there's actually a label on the pot you can search using the label information and probably find a data sheet which will tell you everything you need to know without even doing that. Then you have to design a switch interface that will produce the correct X and Y voltages.

Its unlikely he knows what motor load compensation is or why its essential in what he proposes. He has a plan. And only 2% of the required knowledge and understanding needed. That was one of many reasons I said that its not the right chair. Or controller!

Burgerman wrote:Its unlikely he knows what motor load compensation is or why its essential in what he proposes. He has a plan. And only 2% of the required knowledge and understanding needed. That was one of many reasons I said that its not the right chair. Or controller!

Sorry that I have 2% of required knowledge. I am here to learn thanks. And I already stated that wheelchair I bought that comes with the P&G VSI 50A is the EXACT SAME wheelchair the CP alliance is using for their patients, so what we are trying to do is just improve the controller thats all.

LROBBINS wrote:That chair probably also has small, low power, 2-pole motors that might not withstand 120A draw and will not produce enough torque at currents they can stand to give good motor compensation (with or without an encoder). That was certainly the case with Rachi's original anemic Fracmo motors, even with caster angle sensors added. Once I'd changed the motors to much better ones, motor compensation worked well even with the sensors removed and even though it's front wheel drive. Turn in place remained a problem because it has far too much weight on the rear casters.

To see what the joystick pot does you have to open the case and find the wires that go from the joystick to the circuit board. If it's an analog joystick pot it will have one that's + supply, one that's ground, one (or two) that's a center tap half way between those, one (or two) for X output and one (or two) for Y output. The "or two" is because some pots have duplicate outputs that are used as a safety check that it's functioning correctly. Some fancier pots also have a separate output that is switched on when the stick is centered. Each output will = the center tap voltage when the stick is neutral and have a swing above and below that when the stick is moved. If there are two outputs for X (and for Y) they may swing in the same direction or swing in opposite directions. Chances are that this controller has the simplest pot available with just 5 wires: +, -, center, X and Y. In any case all you need to find out is a half-way decent voltmeter (and great care not to short anything when you are figuring it out). If there's actually a label on the pot you can search using the label information and probably find a data sheet which will tell you everything you need to know without even doing that. Then you have to design a switch interface that will produce the correct X and Y voltages.

thank you so much!

LROBBINS wrote:The VSI almost surely uses one or another serial protocol to communicate with the rest of the system and hacking that may be a tall order. It may be much simpler to make an adapter that connects to the same leads as the joystick pot and mimics the joystick output. Do a search here for postings by woodygb to see how he's done that for using RC controllers to mimic other joystick controllers - yours will be similar. Years ago I had done something similar just using 4066 ICs connected to head and foot switches to select among a set of simple voltage dividers, but Woody's way is a much more flexible solution.

http://greenmobility.com.au/rc-wheelchair-controller/
Is this it?