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Robotarakan Petya for ten bucks

Meet Petya, the six-legged three servos


I continue to publish articles from the Arduino Brain series. Petya is a very cheap (about ten bucks) hexapods. It can be a wonderful project for a rainy day off, which will entertain both adults and children. Since we're talking about entertainment, here's a video with Petya dancing to funk music:



Of course, I did not do any sound analysis, I simply programmed Petya to dance in a certain rhythm. Here is another video in which Petya shows his contempt for juggling balls:



In his current form, Petya can only walk, but at the same time he can see (measure the distance to) nearby obstacles. His brains, however, are productive enough to be able to digest data from many other sensors, send your suggestions!


How to clone Petya


Shopping list


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OCR1A = 1500;    // left servo
OCR1B = 1500;    // right servo
OCR2  = 1500/16; // center servo


-, :


const uint8_t  zero[3] = {45, 50, 40};     // zero position of the servo (degrees)
const uint8_t range[3] = {25, 25, 20};     // the servos are allowed to move in the zero[i] +- range[i] interval

zero[3] , (. ). , 45° ( ), 45° , . , range[3] . , i zero[i]-range[i] zero[i]+range[i].



( , 0°-90°) uint8_t pos[3]. update_servo_timers() - . pos[i]=zero[i]+range[i] i=0,1,2.


. pos_beg[3], pos_end[3], time_start[3] duration[3]. , . :


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movement_planner(), pos[] , update_servo_timers(), - pos[].



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  • 1: {zero[0]-range[0], zero[1]-range[1], zero[2]+range[2]}
  • 2: {zero[0]-range[0], zero[1]-range[1], zero[2]-range[2]}
  • 3: {zero[0]+range[0], zero[1]+range[1], zero[2]-range[2]}
  • 4: {zero[0]+range[0], zero[1]+range[1], zero[2]+range[2]}

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const int8_t advance_sequence[4][3] = {{-1, -1,  1}, {-1, -1, -1}, { 1,  1, -1}, { 1,  1,  1}};

, i step zero[i] + range[i]*advance_sequence[step][i].
:


    uint8_t step = steps_per_sequence-1; // at the initialization stage the (previous) movement is considered to be complete, thus the next movement will be planned starting from the step 0
    while (1) {
        if (is_movement_finished()) {
            step = (step + 1) % 4; // if previous movement is complete, then perform the next step; this variable loops as 0,1,2,3.
            plan_next_movement(step, advance_sequence); // execute next movement
        }
        movement_planner(); // update the servos position according to the planning
        _delay_ms(1);
    }


, , 4 5 . , ( , ), adc_left_eye adc_right_eye , :


        adc_left_eye  = adc_left_eye *.99 + adc_read(5)*.01; // low-pass filter on the ADC readings
        adc_right_eye = adc_right_eye*.99 + adc_read(4)*.01;

_delay_ms() , .99 1-.99 .


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        uint8_t lobst = adc_left_eye  < distance_threshold; // obstacle on the left?
        uint8_t robst = adc_right_eye < distance_threshold; // obstacle on the right?

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        if (is_movement_finished()) {
            if (!lobst && !robst) {
                sequence = advance_sequence; // no obstacles => go forward
            } else if (lobst && robst) {
                sequence = retreat_sequence; // obstacles left and right => go backwards
            } else if (lobst && !robst) {
                sequence = turn_right_sequence; // obstacle on the left => turn right
            } else if (!lobst && robst) {
                sequence = turn_left_sequence; // obstacle on the right => turn left
            }
            step = (step + 1) % steps_per_sequence; // if previous movement is complete, then perform the next step
            plan_next_movement(step, sequence); // execute next movement
        }

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  • Move the electrolyte slightly. I had to tilt it, because otherwise, the central left leg hurts him;
  • Add test sites with easy access to them with an oscilloscope;
  • Add a pair of debug LEDs for debugging without an oscilloscope;
  • Add soldering pads for all unused microprocessor legs for debugging and further expansion of the robot.

Conclusion


Petya is terrible fun!


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