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10. Adjust Posture

In this example, we use the keyboard to control the PiCrawler foot by foot and assume the desired posture.

You can press the space bar to print out the current coordinate values. These coordinate values come in handy when you create unique actions for PiCrawler.

Run the Code

cd ~/picrawler/examples
sudo python3 10_do_single_leg.py

After the code runs, please operate according to the prompt that pops up in the terminal.

• Press 1234 to select the feet separately, 1: right front foot, 2: left front foot, 3: left rear foot, 4: right rear foot

• Press w, a, s, d, r, and f to slowly control the PiCrawler’s coordinate values.

• Press Ctrl+C to exit.

Code

#!/usr/bin/env python3
from picrawler import Picrawler
from time import sleep
import readchar

crawler = Picrawler()

SPEED = 80
STEP_SIZE = 2

manual = '''
-------- PiCrawler Controller ---------
    .......          .......
    <=|   2   |┌-┌┐┌┐-┐|   1   |=>
    ``````` ├      ┤ ```````
    ....... ├      ┤ .......
    <=|   3   |└------┘|   4   |=>
    ```````          ```````
    1: Select right front leg
    2: Select left front leg
    3: Select left rear leg
    4: Select right rear leg

    W: Y++          R: Z++
    A: X--          F: Z--
    S: Y--
    D: X++          Ctrl+C: Quit
'''

legs_list = ['right front', 'left front', 'left rear', 'right rear']

# Axis mapping for cleaner logic
move_map = {
    'w': (1, +STEP_SIZE),  # Y++
    's': (1, -STEP_SIZE),  # Y--
    'a': (0, -STEP_SIZE),  # X--
    'd': (0, +STEP_SIZE),  # X++
    'r': (2, +STEP_SIZE),  # Z++
    'f': (2, -STEP_SIZE),  # Z--
}


def clear_screen():
    print("\033[H\033[J", end='')


def show_info(selected_leg, coordinate):
    clear_screen()
    print(manual)
    print(f"Selected leg: {selected_leg + 1} - {legs_list[selected_leg]}")
    print(f"Coordinate: {coordinate}")


def main():
    selected_leg = 0

    try:
        print(manual)

        # Stand up first
        crawler.do_step('stand', 40)
        sleep(0.5)

        # Get current coordinates
        coordinate = crawler.current_step_all_leg_value()
        show_info(selected_leg, coordinate)

        while True:
            key = readchar.readkey().lower()

            # Select leg
            if key in ('1', '2', '3', '4'):
                selected_leg = int(key) - 1
                show_info(selected_leg, coordinate)

            # Move selected leg
            elif key in move_map:
                axis, delta = move_map[key]

                # Update coordinate
                coordinate[selected_leg][axis] += delta

                # Send updated position
                crawler.do_single_leg(selected_leg, coordinate[selected_leg], SPEED)
                sleep(0.1)

                show_info(selected_leg, coordinate)

            sleep(0.05)

    except KeyboardInterrupt:
        print("\nExiting safely...")

    finally:
        # Return to sitting position on exit
        try:
            crawler.do_step('sit', 40)
            sleep(1)
        except Exception:
            pass

        print("Robot is now sitting. Program ended.")


if __name__ == "__main__":
    main()

• current_step_all_leg_value(): Returns the coordinate values of all legs.

• do_single_leg(leg,coordinate[leg],speed): Modify the coordinate value of a certain leg individually.