Smc3 safety filter ?

My son was racing a F1 car a few days ago and he managed to crash and go into a barrel roll

It was pretty scary and shook him up

He was twisting so fast he was not able to hit the safety shutdown button

Can anyone think of a simple way to filter out sudden changes or excessive motion.

I was thinking of fitting an accelerometer in the seat but there must be a simple way to do it in the smc3 code

Any suggestions ? He is a bit scared to get back on the sim

i added an average value and a range

if the range exceeds the average value it just uses the average value instead

.......................................................................................................................


// MJG 18/8/2020 - code to remove a large jump or spike in data
// uses a moving average and a range value
// if the range is greater than the moving average it just uses the moving average instead


SampleLoop++ ;
if (SampleLoop > Sample) {SampleLoop = 0;}

AvgTarget1[SampleLoop] = Target1;
AvgTarget2[SampleLoop] = Target2;

TmpTarget1 = 0;
TmpTarget2 = 0;

for (int i = 0; i <= Sample; i++) {
TmpTarget1 = TmpTarget1 + AvgTarget1 ;
TmpTarget2 = TmpTarget1 + AvgTarget2 ;
}

TmpTarget1 = TmpTarget1 / Sample ;
TmpTarget2 = TmpTarget2 / Sample ;

if (Target1 > TmpTarget1 + Target1Range){
Target1 = TmpTarget1;
}

if (Target1 < TmpTarget1 - Target1Range){
Target1 = TmpTarget1;
}


if (Target2 > TmpTarget2 + Target2Range){
Target2 = TmpTarget2;
}

if (Target2 < TmpTarget2 - Target2Range){
Target2 = TmpTarget2;
}

The code above did not work that sucessfully, the dam thing moves too fast

I will try a different approach where the motor strength is reduced and then restored after a period of time

I was about to post limiting power would probably be an easy way but then you posted your code which I hoped would work out. But a simple way would be to set PWMmax1. 2 and 3 temporarily to a lower number then raise them back when the event is over. I use PWMmax to control the motors on the soft start routine I added.

Hi @BlazinH,

I coded the pwmmax to keep cutting in half till then after the event is over wait 5 secs and bring it back.

However, today I programmed a g sensor that outputs when a shock is detected, i can use that to s

I programmed it to keep halving the pwm max till the event is over, after 5 secs the full pwm is restored

However today i programmed a simple g sensor i can fit to the rig

Similar to this -- https://www.arduino.cc/en/Tutorial/ADXL3xx


Basically it outputs a digital pin that i can detect on the smc3 board and use that to reduce motion

I will fit it to the rig and see what sort of forces it records.

the codes uses a mma7361 Accelerometer and a Nano

it ouputs pin 13 high if it detects over 1g of force

after 5 seconds the pin is released

this pin can be used to trigger the SMC3 into a stall mode


/***********************************************************/
/****************** Accelerometer ****************ar******/
/***********************************************************/
int x, y, z; //raw analog values
float x_avg, y_avg, z_avg; //smoothed values
float rx, ry, rz; //smoothed value in number of gs (one g = 9.8 m/s^2)

float tiltAngle;

float vref;
float vzerog;
float sensitivity;

void initAcc()
{
vref = 5.0; //voltage reference
vzerog = 1.65; //voltage at zero g, as specified by accelerometer datasheet
sensitivity = 0.8; //output voltage produced by a certain force, as specified in datasheet
}

/***********************************************************/

void setup()
{
delay(1000);

initAcc();
Serial.begin(9600);

pinMode(12, INPUT_PULLUP);
}

void loop()
{
updateAcc();
delay(50);
}

void updateAcc()
{
//raw accelerometer values
x = analogRead(A0);
y = analogRead(A1);
z = analogRead(A2);

// Serial.print(x);
// Serial.print('\t');
// Serial.print(y);
// Serial.print('\t');
// Serial.print(z);
// Serial.print('\t');
// Serial.println();
//
// Serial.print(rx);
// Serial.print('\t');
// Serial.print(ry);
// Serial.print('\t');
// Serial.print(rz);
// Serial.print('\t');
// Serial.println();

//smoothed values
//x_avg = expMovingAvg(x, 0.1, x_avg);
//y_avg = expMovingAvg(y, 0.1, y_avg);
//z_avg = expMovingAvg(z, 0.1, z_avg);

//smoothed values in number of gs (one g = 9.8 m/s^2)
// rx = (x_avg*vref/1023-vzerog) / sensitivity;
// ry = (y_avg*vref/1023-vzerog) / sensitivity;
// rz = (z_avg*vref/1023-vzerog) / sensitivity;

rx = (x*vref/1023-vzerog) / sensitivity;
ry = (y*vref/1023-vzerog) / sensitivity;
rz = (z*vref/1023-vzerog) / sensitivity;


Serial.print(rx);
Serial.print('\t');
Serial.print(ry);
Serial.print('\t');
Serial.print(rz);
Serial.print('\t');
Serial.println();


if ((rx > 1) || (rx < -1)){

Serial.println("Excess X Force");

Serial.print(rx);
Serial.print('\t');
Serial.print(ry);
Serial.print('\t');
Serial.print(rz);
Serial.print('\t');
Serial.println();
digitalWrite(13, HIGH);
delay(5000);
digitalWrite(13, LOW);


}


if ((ry > 1) || (ry < -1)){

Serial.println("Excess Y Force");

Serial.print(rx);
Serial.print('\t');
Serial.print(ry);
Serial.print('\t');
Serial.print(rz);
Serial.print('\t');
Serial.println();
digitalWrite(13, HIGH);
delay(5000);
digitalWrite(13, LOW);

}


if ((rz > 1) || (rz < -1)){

Serial.println("Excess Z Force");

Serial.print(rx);
Serial.print('\t');
Serial.print(ry);
Serial.print('\t');
Serial.print(rz);
Serial.print('\t');
Serial.println();
digitalWrite(13, HIGH);
delay(5000);
digitalWrite(13, LOW);

}


//angle accelerometer is tilted from vertical, in radians (exact only if it is at rest)
//tiltAngle = acos( (rx*0 + ry*0 + rz*-1) / (sqrt(sq(rx) + sq(ry) + sq(rz)) * sqrt(sq(0) + sq(0) + sq(-1))) );

//Serial.print("tilt angle: ");
//Serial.println(tiltAngle);
}

//Exponential moving average, weight on new value
float expMovingAvg(float new_val, float weight_on_new, float avg)
{
return avg + weight_on_new*(new_val - avg);
}

What about adding a capacitive sensor on the seat? If the driver is ejected from his seat, it would slow down the motion...

@BlazinH

I looked at your softstart code and it looks like you have a park routine

i can use this with the accelerometer

does the park just drop power to the motors till the pin(8) is released ?

Sorry but my code is soft start only. It could be reversed however.
Needless to say I don't know where you got info regarding pin(8).

Using an accelerometer is a novel ideal but thats like putting the horse before the buggy I think. Yes normally thats correct but that method uses the result of power after being applied vs before; like after the horses pulling has affected the buggy. But with use of current and previous set point variables I think the horses affect on the buggy should be able to be calculated prior to actual movement resulting in more precise control with less latency.

Hi BlazinH

The park on pin 8 must have been my own work. I did look at it some time ago and forgot to rename the sketch.

Yes I know what you mean about trapping the event before the sim gets a hard kick.

I have used a moving average and a step amount. If the sim trys to move to fast it can drop the power off.

I will start again and code it based on your softstart sketch