News Details

Introduction

The performance of an AGV or AMR system depends heavily on its drive system. Acceleration capability, turning performance, load capacity, and long term stability are all directly influenced by the selection of the drive wheel and motor.

In engineering practice many AGV projects select motors based only on total vehicle weight or previous experience. This approach often leads to insufficient torque during turning or acceleration because a differential drive AGV operates under multiple motion conditions.

A proper design must consider all working conditions including straight motion, curved motion, and in place rotation. Among these conditions in place rotation usually requires the highest torque and becomes the key factor in motor selection.

This document explains the basic engineering method for calculating torque and inertia for differential drive wheel AGVs.

Differential Drive Wheel System Overview

A differential drive AGV typically uses two powered drive wheels and multiple caster wheels for support.

The motion is controlled by changing the speed difference between the left and right drive wheels.

Equal speed results in straight motion.

Different speeds result in turning motion.

Opposite directions result in in place rotation.

This system is widely used in warehouse AGVs AMRs tugger vehicles and industrial mobile robots.

Motion Resistance Components

The total resistance acting on the AGV consists of three main parts.

Rolling resistance

F_roll = (m - m_drive) * g * mu

m is total vehicle mass

m_drive is load supported by drive wheels

mu is rolling resistance coefficient

Acceleration force

F_acc = m * a

a is acceleration of the vehicle

Grade resistance

F_grade = m * g * sin(theta)

theta is slope angle

For flat ground this value is zero

Total driving force

F_total = F_roll + F_acc + F_grade

This force is used as the basis for torque calculation

Straight line operation torque

In straight motion both drive wheels share the load equally

Force per wheel

F_straight = F_total / 2

Torque per wheel

T_straight = F_straight * (D / 2)

D is drive wheel diameter

This condition is used for continuous operation verification

In place rotation critical condition

In place rotation is the most demanding condition for a differential drive AGV

During rotation one wheel rotates forward and the other rotates backward

Caster wheels generate high resistance due to steering angles

An engineering approximation of resistance is

F_spin = (2 * F_roll * sqrt(W^2 + L^2)) / W

W is wheel spacing

L is vehicle length

Torque requirement

T_spin = F_spin * (D / 2)

In most real applications rotation torque is two to five times higher than straight line torque

This condition usually determines motor selection

Curved motion condition

Most AGVs operate under curved motion during normal operation

In this case wheel speeds are different and caster wheels generate steering resistance

In general

T_straight < T_curve < T_spin

Curved motion is used for validation of system stability

Load inertia and gear ratio matching

Inertia is an important factor for motion control performance

Equivalent load inertia

J_load = (m / 2) * (D / 2) * (D / 2)

If a gearbox is used the inertia reflected to motor side is

J_motor = J_load / (i * i)

i is gear ratio

Recommended inertia ratio

Servo system below 5 to 1

Stepper system below 10 to 1

Proper inertia matching improves acceleration response stability and control accuracy

Engineering considerations for drive wheel selection

In real applications torque calculation alone is not enough

The following factors must also be considered

wheel traction

gearbox durability

thermal performance

continuous operation time

floor conditions

load distribution

Ignoring these factors may cause wheel slip overheating or unstable motion control

TEC series differential drive wheels

In practical AGV development integrated drive wheel systems are widely used to simplify design and improve reliability

The TEC series differential drive wheels developed by Yikong Intelligent Equipment integrate low voltage servo motors gearboxes and wheel assemblies into a compact unit

TEC85， TEC240 and TEC550 models are used in

AGVs

AMRs

tugger systems

industrial mobile robots

heavy duty transport platforms

These products help reduce development complexity and improve system consistency

Conclusion

Differential drive AGV motor sizing must be based on multi condition analysis rather than simple weight estimation

Straight motion defines continuous torque requirement

Curved motion validates stability

In place rotation defines maximum torque requirement

Proper torque calculation combined with inertia matching ensures stable and reliable AGV performance in industrial environments