SMC6 - 6DOF Motion Simulator

Hi Guys,

I wanted to share with you the latest Sim I have been building

I have called it the SMC6 - basically it can control up to 6 actuators using one board

The Board is a Teensy 4.1 which is very powerful and has plenty of inputs and outputs
its speed is 600 mhz compared to an Arduino at 16 mhz !
it can be overclocked to 1GHZ if you use a chip cooler !

The motors are indexed using shaft encoders for very high accuracy
the encoders are 1440 ppr and are attached to the motor not the output arm
combined with the gearbox of the motor there is some very fine resolution available

the default resolution on full range is 16bit - or 65,535 steps !

The motors on this sim are Brushed DC motors from an electric tow tug
Brushed motors have greater stall torques than brushless motors and are very much suited to motion sims

Something i found with building my previous driving sims is that not all the actuators do as much work as the others, some of them draw much more current - this is just the way the motors are loaded on a driving sim
I decided to use a mix of different gear ratios so the motors doing the most work can have more torque
The SMC6 firmware measure the acceleration and speed of the actuators and can make them run faster or slower so having different gear ratios does not matter.

the gearbox ratios are

2 x 60:1
2 x 40:1
2 x 30:1

The motor drivers are 200A each and are buffered by 2x 12v batteries - there is around 1600 amps available from the batteries. I do not think you would be able to power this sim using single phase house electricity

In testing we have seen over 1000 mm / sec on this sim ! - no one has been brave enough to sit on it during a test yet !

There is a PC configuration program that i have written also that lets you test the actuators and also configure the PID control for each motor
Test modes include sine wave, square wave, step up and step down.
I am working on a tool that lets you draw a test cycle and then make the actuators replay it

you can see the first test here

more videos will be available when I am ready to release them

i am also building 6 dof with wormgear , can you share more ?

What questions do you have ?

Do you have a build thread ?

Hi,

I am researching my first build, and came across your earlier build, and now this one. I like your earlier build.

After looking at your video, can I ask:

1. Is the battery powering only the motors, and the electronics are powered by power supply on LH side of cabinet?
2. What type of motor controllers are they please? Top of cabinet, 3x units - does each one control 2x motors?
3. Do you have a diagram for how you connected the Teensy 4.1 please?

Thank you.

Second question - This is a 100A driver for two motors, like this:

Yes these are the motor drivers

They can handle 200 A for short periods of time

I suggest you use a cooling fan on them

Hi Fifi

attached is a wiring diagram for the Teensy 3.6 / 4.1

the software and firmware is not open source

There are several power supplies

24V - keeping the batteries charged
12V - powering the encoders and the main isolation relay
5v - powering the electronics and motor drivers
3.3v - used to supply 3.3v at the board level

the batteries power the DC motors and also work as buffers for the regenerative power from the motors

Today I implemented the ability to create a custom test or waveform

basically you can have a text file that has 3600 entries and the software will read them one at a time and send them as a stream of positions to the selected actuators



next step is to install simtools and get it working with LFS

Thank you for the replies. It is very handy for me to be able to research different options before building.

@noorbeast can you confirm I have the correct settings for simtools

My Sim uses the protocol

TGT65536,65536,65536,65536,65563,65536

Basically TGTAxis1,Axis2,Axis3,Axis4,Axis5,Axis6

The start and stop positions are TGT32768,32768,32768,33768,32768,33768

Pic attached of current config

the board can respond to many different commands

TGT is designated Target- each actuator is sent a position between 0 and 65536

a string like this is sent "TGT10000,20000,30000,40000,50000,60000"

i have simtools v2.5.x installed and it beeps when i try and enable output testing

however - using a serial port sniffer I can not see simtools is sending any data

I designed and wrote the code for the device - so if it does not work I can make it work

can Simtools transmit a line of data like this ?

"TGT10000,20000,30000,40000,50000,60000"

Yes with a 16bit decimal value output it does go from 0 to 65535, i get.

Code:

I received: TGT0,0,0,0,0,0
I received: TGT0,0,0,0,0,0
I received: TGT0,0,0,0,0,0
I received: TGT0,0,0,0,0,0
I received: TGT9945,9945,9945,9945,9945,9945
I received: TGT32130,32130,32130,32130,32130,32130
I received: TGT45899,45899,45899,45899,45899,45899
I received: TGT52530,52530,52530,52530,52530,52530
I received: TGT56610,56610,56610,56610,56610,56610
I received: TGT58905,58905,58905,58905,58905,58905
I received: TGT64260,64260,64260,64260,64260,64260
I received: TGT65535,65535,65535,65535,65535,65535
I received: TGT65535,65535,65535,65535,65535,65535

TGT<Axis1a>,<Axis1a>,<Axis1a>,<Axis1a>,<Axis1a>,<Axis1a>S as output string in simtools engine.

And this little snippet of code for hardware side.

Code:

  
if (Serial2.available() > 0) {
int BUFFER_SIZE = 100;
char buf[BUFFER_SIZE];
    int rlen = Serial2.readBytesUntil('S', buf, BUFFER_SIZE);

    // prints the received data
    Serial.print("I received: ");
    for(int i = 0; i < rlen; i++)
      Serial.print(buf[i]);

      Serial.println("");
  }

every character number or comma seems to be a byte in this case.

Code:

T[0] G[1] T[2] 6[3] 5[4] 5[5] 3[6] 5[7] ,[8] 6[9] 5[10] 5[11] 3[12] 5[13] ,[14] 6[15] 5[16] 5[17] 3[18] 5[19] ,[20] 6[21] 5[22] 5[23] 3[24] 5[25] ,[26] 6[27] 5[28] 5[29] 3[30] 5[31] ,[32] 6[33] 5[34] 5[35] 3[36] 5[37]

Thanks for the info

But sim tools does not seem to be outputting anything at all

Is it because the simtools version is demo and can only output 2dof ?

I tried the protocol TGT<Axis1a>,<Axis1a>,<Axis1a>,<Axis1a>,<Axis1a>,<Axis1a>S

Does the S tell simtools its a string ?

Should we be using square brackets or < > ?

No i have the demo version, so that shouldn't be a problem.
If everything checks out, com port Baud speed etc. you should be able to receive data when output testing is turned on. And axis are assigned off course.

The S is just for a easy end byte to check for.
used here.
Serial2.readBytesUntil('S', buf, BUFFER_SIZE);
But this generally bad practice because readBytesUntil() is blocking the rest of the code when reading. At least with the arduino family.

You should have something in place for the difference in array length with decimal. Or use Binary, in that case you get 2 bytes for each value. first byte X 256 + second byte is the value. in that case you could count up.
with simtools binary you know how many bytes will be received because of the output format.
TGT is 3 bytes[0][1][2].
So value 1 would be
(byte[3] X 256) + byte[4] = value 1
value 2
Byte[5] = ","
(byte[6] X 256) + byte[7] = value 2
etc..

But you could also use start bytes and end bytes off course, because A == 65 ASCII And when you are checking for A and the value of the axis is 65 your code handles it like an A. So A(byte 65) would be bad. With decimal this problem is solved. if you use ascci values above 9. The total of bytes are different with values 0 or 65535. 1 byte or 5 bytes in this case. So then you would create a string so you can add the numbers until "," then convert your string to an int. Do this for every value.

for simple testing you could use another uart and read with one and print with the other byte for byte.
so something like

if(Serial2.available() > 0)
{
Serial.print(Serial2.read());
}

this way you could find out how you want to approach it.

this is some nice information on how to do it in an none blocking way.

https://forum.arduino.cc/t/serial-input-basics-updated/382007/3