Question Help with my 6DOF RC Simulator Test not working properly.

Hello everybody.
My name is Håkan and I am a total beginner in building my own DIY simulator. I apologize if my English is not good but I hope you all can still understand what I am writing. I ask all of you who may answer that you use simple language and simple terms so that I have a chance to understand what you mean. I learn all the time ...

I have managed to build a small 2DOF RC car simulator with the help of what I managed to read here and there on this forum. I enclose a picture of it and it works quite well. Have tested it on LFS and link is here:






For it I have used the following hardware:
1 x Arduino UNO
2 x XT Generig Mini Servo
1 x 6VDC Power Adapter
Some mixed RC stuff and some wires

Now I want to take the next step and build a 6DOF RC simulator as a test before a real construction of a so-called Stewart platform. I have connected everything on my worktable with the same hardware as in 2DOF. The only difference is that the servos I use now are MG90S Metal Gear Mini Servo with the following specifications.

Modulation: Analog
Torque: 4.8V: 30.60 oz-in (2.20 kg-cm)
6.0V: 34.70 oz-in (2.50 kg-cm)
Speed: 4.8V: 0.11 sec / 60 °
6.0V: 0.10 sec / 60 °
Rotational Range: 180 °
Pulse Cycle: 20 ms
Pulse Width: 400-2400 µs

The code I use which is slightly modified by me to be able to control 6 servos instead of two is further down here in this thread.

In SimTools GameEngine I have the following settings. (Some pictures is attached)

Interface Settings:
ComPort: COM3
BitsPerSecond: 9600
Data Bits: 8
Parity: None
Stop Bits: 1
Output-Bit-Range: 8
Output Type. Decimal.
Interface Output: A <Axis1a> B <Axis2a> C <Axis3a> D <Axis4a> E <Axis5a> F <Axis6a>

I mainly have two problems that I do not understand.
1. If in "Axis Assignments" I have a value higher than 20%, the servo jerks sharply when I in "Output Testing" pull the slider to a low value (to the left side of slider). The higher the%, the earlier the jerk comes.
For example. if I set Axis1a to 22%, the jerk comes at -88% slider value. If I instead set Axis1a to 40%, the jerk will already be at -55% slider value. Positive values are not a problem. This phenomenon applies to all 6 axes, Axis1a to Axis6a.

Why can I not enter a value higher than 20% without getting these twitches? The higher the percentage, the earlier the twitches come. With a low percentage, I also get a much smaller movement on the servo arm than the servo can handle and a simulator that moves much less than I want.



2. The servos start/neutral position that I set in the Arduino code (int actuatorPosition [kActuatorCount] = {90, 90, 90, 90, 90, 90}) is correct as long as the Arduino IDE controls UNO. But as soon as I click on "Turn On" in "Output Testing" all the servos move to some other position that is not in the neutral position and I do not know how or where to correct the neutral position so that it is in the correct starting position.
What am I doing wrong or what do I not understand? Please, can someone guide me on the right path so I can get on with my 6DOF RC Simulator and learn all the settings in SimTools before I spend a lot of money on starting building a "real" motion platform.



Please help me!
Thanks

The code I use, tweeked for my 6DOF RC Servo Sim

//********************************************************************************************
// RC Model Servo
// Original code By EAOROBBIE (Robert Lindsay)
// Completely mangled by aarondc
// For free use for Sim Tool Motion Software
//********************************************************************************************
#include <Servo.h>
//#define DEBUG 1 // comment out this line to remove debuggin Serial.print lines
const int kActuatorCount = 6; // how many Actuators we are handling

// the letters ("names") sent from Sim Tools to identify each actuator
// NB: the order of the letters here determines the order of the remaining constants kPins and kActuatorScale
// const char kActuatorName[kActuatorCount] = { 'R', 'L', 'F', 'V', 'M', 'N' };
const char kActuatorName[kActuatorCount] = { 'A', 'B', 'C', 'D', 'E', 'F' };
//const int kPins[kActuatorCount] = {2, 3, 4, 5, 6, 7}; // pins to which the Actuators are attached
const int kPins[kActuatorCount] = {8, 9, 10, 11, 12, 13}; // pins to which the Actuators are attached
const int kActuatorScale[kActuatorCount][2] = { { 0, 255 } , // 255 original Right Actuator scaling
{ 0, 255 } , // 255 original Left side Actuator scaling
{ 0, 255 } ,
{ 0, 255 } ,
{ 0, 255 } ,
{ 0, 255 }
};
const char kEOL = '~'; // End of Line - the delimiter for our acutator values
const int kMaxCharCount = 3; // some insurance...
Servo actuatorSet[kActuatorCount]; // our array of Actuators
int actuatorPosition[kActuatorCount] = {90, 90, 90, 90, 90, 90};// current Actuator positions, initialised to 90
int currentActuator; // keep track of the current Actuator being read in from serial port
int valueCharCount = 0; // how many value characters have we read (must be less than kMaxCharCount!!

// set up some states for our state machine
// psReadActuator = next character from serial port tells us the Actuator
// psReadValue = next 3 characters from serial port tells us the value
enum TPortState { psReadActuator, psReadValue };
TPortState currentState = psReadActuator;

void setup()
{
// attach the Actuators to the pins
for (int i = 0; i < kActuatorCount; i++)
actuatorSet.attach(kPins);

// initialise actuator position
for (int i = 0; i < kActuatorCount; i++)
updateActuator(i);

Serial.begin(9600); // opens serial port at a baud rate of 9600
}
void loop()
{

}

// this code only runs when we have serial data available. ie (Serial.available() > 0).
void serialEvent() {
char tmpChar;
int tmpValue;

while (Serial.available()) {
// if we're waiting for a Actuator name, grab it here
if (currentState == psReadActuator) {
tmpChar = Serial.read();
// look for our actuator in the array of actuator names we set up
#ifdef DEBUG
Serial.print("read in ");
Serial.println(tmpChar);
#endif
for (int i = 0; i < kActuatorCount; i++) {
if (tmpChar == kActuatorName) {
#ifdef DEBUG
Serial.print("which is actuator ");
Serial.println(i);
#endif
currentActuator = i; // remember which actuator we found
currentState = psReadValue; // start looking for the Actuator position
actuatorPosition[currentActuator] = 0; // initialise the new position
valueCharCount = 0; // initialise number of value chars read in
break;
}
}
}

// if we're ready to read in the current Actuator's position data
if (currentState == psReadValue) {
while ((valueCharCount < kMaxCharCount) && Serial.available()) {
tmpValue = Serial.read();
if (tmpValue != kEOL) {
tmpValue = tmpValue - 48;
if ((tmpValue < 0) || (tmpValue > 9)) tmpValue = 0;
actuatorPosition[currentActuator] = actuatorPosition[currentActuator] * 10 + tmpValue;
valueCharCount++;
}
else break;
}

// if we've read the value delimiter, update the Actuator and start looking for the next Actuator name
if (tmpValue == kEOL || valueCharCount == kMaxCharCount) {
#ifdef DEBUG
Serial.print("read in ");
Serial.println(actuatorPosition[currentActuator]);
#endif
// scale the new position so the value is between 0 and 179
actuatorPosition[currentActuator] = map(actuatorPosition[currentActuator], 0, 255, kActuatorScale[currentActuator][0], kActuatorScale[currentActuator][1]);
#ifdef DEBUG
Serial.print("scaled to ");
Serial.println(actuatorPosition[currentActuator]);
#endif
updateActuator(currentActuator);
currentState = psReadActuator;
}
}
}
}


// write the current Actuator position to the passed in Actuator
void updateActuator(int thisActuator) {
actuatorSet[thisActuator].write(actuatorPosition[thisActuator]);
}

Thank's for the reply.

I have read the manual v. 2.5 from top to bottom, over and over again, and tried most things but still can not understand my problem. That's why I'm asking for help here.

If this is the case that the servos are downward in each DOF and not horizontal as I thought then how come the following?


This setting of forces only gives movement on servo one when I move the sliders for Roll, Pitch and Yaw:




This setting of forces instead gives movement on servos one, two and three when I move the sliders for related force Roll, Pitch and Yaw:



I thought that Axis1a corresponds to servo one, Axis2a corresponds to servo two and so on. Is that completely wrong?

My problem with twitches and incorrect neutral position as I described it in the beginning unfortunately remains ...

dof1 pitch ,pitch ... one dir the sign will light up in orange
dof 2 roll ,roll.....THE SAME

Ok, got it! It's completed now.
But jerks, the wrong neutral position and less than 20% value remains. What to do about that?

Axis Assignments:
Axis1a: Roll +10 / Pitch +15 / Heave -15 / Yaw -15 / Sway -15 / Surge +15
Axis2a: Roll -15 / Pitch 0 / Heave +15 / Yaw -15 / Sway 0 / Surge +15
Axis3a: Roll +10 / Pitch -15 / Heave -15 / Yaw -15 / Sway -15 / Surge +15
Axis4a: Roll +10 / Pitch +15 / Heave +15 / Yaw -15 / Sway -15 / Surge -15
Axis5a: Roll -15 / Pitch 0 / Heave -15 / Yaw -15 / Sway 0 / Surge -15
Axis6a: Roll +10 / Pitch +15 / Heave +15 / Yaw -15 / Sway -15 / Surge -15

Interface Settings:
Serial / COM20 / 9600 BPS / 8 DB / None P / 1 SB / 10 O-BR / Decimal O-Type

Startup - Output: [A<128>][B<128>][C<128>][D<128>][E<128>][F<128>] 10ms
Interface - Output: [A<Axis1a>][B<Axis2a>][C<Axis3a>][D<Axis4a>][E<Axis5a>][F<Axis6a>] 10ms
Shutdown - Output: [A<128>][B<128>][C<128>][D<128>][E<128>][F<128>] 10ms

Axis Limiting:
100% for all axis

Thank's noorbeast for your efforts to help!

If I change the Bit Range to 8, absolutely nothing happens when I test if it works in the Output Testing window.

It also does not matter if I write,
[A <Axis1a>] [B <Axis2a>]. . .
or
A <Axis1a> ~ B <Axis2a> ~. . .

But by changing Startup - Output to:
A<128>~B<128>~C<128>~D<128>~E<128>~F<128>~
The wrong neutral position is gone. But unfortunately the jerks at high or low % amount still remains when output testing.

I have no extra spaces, must have happened when I copied and pasted the text from simtool to here.
Sorry for that.