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Smc3 safety filter ?

Discussion in 'DIY Motion Simulator Projects' started by Gadget999, Aug 17, 2020.

  1. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
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    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
    Last edited: Aug 18, 2020
  2. Ads Master

    Ads Master

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  3. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
    2DOF, DC motor, Arduino, 6DOF
    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;
    }
  4. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
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    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
  5. BlazinH

    BlazinH Well-Known Member

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    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.
  6. Gadget999

    Gadget999 Well-Known Member

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    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.
    • Creative Creative x 1
  7. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
    2DOF, DC motor, Arduino, 6DOF
    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);
    }
  8. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    My Motion Simulator:
    AC motor, Motion platform, 4DOF, 6DOF
    What about adding a capacitive sensor on the seat? If the driver is ejected from his seat, it would slow down the motion... :p
    • Funny Funny x 2
  9. Gadget999

    Gadget999 Well-Known Member

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    @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 ?
  10. BlazinH

    BlazinH Well-Known Member

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    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.
  11. Gadget999

    Gadget999 Well-Known Member

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    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 :)