7.Motor Sizing And Battery Sizing - L-division-2021-2022-Even/Repo-06 GitHub Wiki

1.Motor Sizing

We will be using totally 18 Servos for 6 legs, each having 3 Servos.

where;

T= Torque

M= Mass

A= Acceleration

D= Diameter

Servo motors 18 x 9g = 162g
Dimensions of single leg part= 5 x 0.7 x 2 = 8.68 mm^3
Therefore volume of one leg = 8.68 * 3 = 26.04 mm^3
mass of each leg = density x volume
= 1.24 * 26.04 = 32.28 g
Total weight of all legs = 6 * 32.28 = 193.68 g
weight of Arduino mega 2560 = 36 g
volume of casing = 15 x 5 x 6 = 450 mm^3
The thickness of all sides of casing is 3 mm, so calculating volume 14.7 x 4.7 x 5.7 = 393.813 mm^3
Total volume of casing = 450 - 393.813 = 56.187
Mass of casing = 56.187 * 1.24 = 69.67 g
weight of Ultrasonic sensor and LDR sensor = 10 + 15 = 25g
Weight of wires = 5 g
Total mass = 491.35 g
F = m*g = 491.35 * 9.8
= 0.4815
Torque = F * r
= 0.4815 * 1.2
= 0.5778 Ncm
= 0.5778 * FOS
= 0.5778 * 1.5
= 0.8667 kg-cm
Hence We have selected servo SG90 as it has max torque between 1.2-1.6 kg-cm, which is servo motor with minimum specification available in servo motors.

As we are using 18 servo motors, each servo has a stall current rating of 650mA.