Lesson 24 - Arm, Gripper & Neck Servos

Learning Objective

• Command articulated left and right arm joint angles using move_left_arm() and move_right_arm().
• Control end-effector grippers using open_grippers(), close_grippers(), and set_grippers().
• Control head pan/tilt orientation using set_neck(), look_left(), look_right(), and look_center().

Introduction

Articulated robots use servos to move limbs, actuate grippers, and point sensors. The bonicbot_bridge SDK provides high-level shortcuts for commanding left/right arms, grippers, and neck joint positions.

This lesson covers joint positioning methods for arms, end-effectors, and neck servos.

Code

import time
from bonicbot_bridge import BonicBot
 
with BonicBot(host="192.168.29.52") as bot:
    print("1. Centering neck and opening grippers...")
    bot.look_center()
    time.sleep(2.0)
 
    print("2. Panning neck left and right...")
    bot.look_left()
    time.sleep(2.0)
    bot.look_center()
    time.sleep(2)
    bot.look_right()
    time.sleep(2.0)
    bot.look_center()
    time.sleep(2)
 
    print("3. Moving left and right arms to 45° shoulder / 30° elbow pose...")
    bot.move_left_arm(shoulder=65.0, elbow=40.0, wait=True)
    time.sleep(2)
    bot.move_right_arm(shoulder=65.0, elbow=40.0, wait=True)
    time.sleep(2)
    bot.open_grippers()
    time.sleep(2)
    print("4. Closing grippers...")
    bot.close_grippers()
    time.sleep(1.0)
 
    print("5. Resetting all servos to neutral 0° positions...")
    bot.reset_servos()

Expected Output

🤖 Connected to BonicBot at 192.168.29.52:9090
1. Centering neck and opening grippers...
2. Panning neck left and right...
3. Moving left and right arms to 45° shoulder / 30° elbow pose...
4. Closing grippers...
5. Resetting all servos to neutral 0° positions...
🔌 Disconnected from BonicBot

🔧 Under the Hood

Student Challenge

Challenge 1 — Python Only

Write a helper function deg_to_rad_dict(degrees_dict) that takes a dictionary of joint angles in degrees and returns a new dictionary with angles converted to radians.

import math
 
def deg_to_rad_dict(degrees_dict):
    return {joint: math.radians(deg) for joint, deg in degrees_dict.items()}
 
input_deg = {"neck_yaw": 45.0, "left_elbow": 30.0}
print("Converted radians:", deg_to_rad_dict(input_deg))

Challenge 2 — Robot

Program a “wave” routine: raise right shoulder to 90°, move elbow between 20° and 50° twice, then call bot.reset_servos().

import time
from bonicbot_bridge import BonicBot
 
with BonicBot(host="192.168.0.188") as bot:
    print("Raising right arm...")
    bot.move_right_arm(shoulder=90.0, elbow=20.0, wait=True)
 
    for _ in range(2):
        bot.move_right_arm(shoulder=90.0, elbow=50.0, wait=True)
        time.sleep(0.3)
        bot.move_right_arm(shoulder=90.0, elbow=20.0, wait=True)
        time.sleep(0.3)
 
    bot.reset_servos()

Quick Reference

Reflection Questions