MAVRIC

Wander Circuit

Figure 1. The wander circuit is composed of four neurons. RO = rightOscillator, LO = leftOscillator, RT = rightTrigger, LT = leftTrigger. Constants are shown in rectangles. Not all constants are shown. The RO and LO cells are tonic with randomized inputs. The RT and LT cells are threshold-burst devices. Once the threshold has been exceeded the neuron outputs for some time afterward with a decay. The thresholding acts as a time delay before onset of the output. The outputs of the trigger cells inhibit their respective oscillator cells and excite the colateral oscillator.

The wander circuit is implemented below in pseudocode.

All variables/constants doubles unless otherwise specified

Constants:
gain = 0.25
decay = 0.1
threshold = 0.5;

External variables:
baseSpeed
goRight
goLeft
goStraight
rightMotor
leftMotor

Internal variables:
rightOscillator
rightTrigger {
   input
   output
}
leftOscillator
leftTrigger {
   input
   output
}

Initialize:
rightTrigger.input = 0;
rightTrigger.output = 0;
leftTrigger.input = 0;
leftTrigger.output = 0;

Utilities:

double bound(double v)
{
double ret = 0.0;
if (v > 0.99) ret = 0.99;
else if (v < 0.0) ret = 0.01;
return ret;
}

double random(double max)
{
generate a random double in the range 0.0 .. max
}

Execute every 1/10 second:
rightOscillator = bound(0.5 + random(0.1) + leftTrigger.output -
                   rightTrigger.output - goRight - goStraight);
leftOscillator = bound(0.5 + random(0.1) + rightTrigger.output -
                   leftTrigger.output - goLeft - goStraight);
rightTrigger.input = bound(rightTrigger.input +
                           rightOscillator * gain -
                           rightTrigger.input * decay);
if (rightTrigger.input > threshold) {
   rightTrigger.output = bound(rightTrigger.input + random(0.1));
   rightTrigger.input = random(0.1);
}
leftTrigger.input = bound(leftTrigger.input +
                           leftOscillator * gain -
                           leftTrigger.input * decay);
if (leftTrigger.input > threshold) {
   leftTrigger.output = bound(leftTrigger.input + random(0.1));
   leftTrigger.input = random(0.1);
}

End Execute

Execute every 1/10 second:

rightMotor = bound(baseSpeed + rightOscillator);
leftMotor = bound(baseSpeed + leftOscillatory);

End Execute