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In various AGV solutions used for intralogistics, the chassis mobility system is often one of the first considerations in design, yet one of the last components to be fully optimized. Unlike navigation algorithms, which are highly visible, or dispatching systems, which are dynamically managed, the mobility system fundamentally determines how stable, agile, and precise an AGV can be.

Differential drive wheels, steering drive wheels, and casters form an engineering "triangle" of trade-offs among cost, precision, and flexibility. Different combinations and compromises ultimately define the mobility characteristics of an AGV.

1. Differential Drive Wheels: Technical Characteristics and Application Boundaries

Differential drive wheels are the core power-output components of an AGV. Differential drive is the most widely adopted propulsion solution for light- and medium-duty AGVs, achieving steering and movement through speed differences between the left and right drive wheels.

1.1 Understanding Differential Motion

The principle of differential steering is intuitive. When the left wheel rotates faster than the right wheel, the vehicle naturally turns right. If both wheels rotate in opposite directions at the same speed, the AGV can rotate around its own center point.

This steering method relies entirely on wheel speed differences, making differential drive particularly suitable for applications where basic turning capability is sufficient. Examples include transporting racks or materials between fixed points where lateral movement and millimeter-level positioning accuracy are not required.

1.2 Advantages and Limitations

The advantages of differential drive wheels are straightforward:

• Low cost

• Robust and durable structure

• Easy maintenance

• Mature ecosystem of motors and controllers

• Simple control algorithms

However, differential drive systems also have clear limitations.

Since the two wheels operate independently, uneven tire wear and minor floor irregularities can gradually cause the AGV to deviate from its intended path during long-distance travel. While this may not be problematic in open spaces, it can significantly impact automatic docking with production equipment and workstations.

Additionally, differential-drive AGVs tend to experience rear-end swing caused by inertia when cornering at higher speeds. This effect becomes more noticeable in heavy-load applications or on slippery floors.

2. Steering Drive Wheels: The Integrated Solution for High-End AGV Mobility

AGV steering drive wheels integrate propulsion, steering, and load-bearing functions into a single module. They are the key enabling technology for omnidirectional AGV movement and are widely regarded as a hallmark of high-end AGV platforms.

2.1 Why Early Steering Drive Wheels Had Limited Adoption

Size and Height Constraints

Early imported steering drive wheel systems typically featured relatively large installation heights. Since under-riding AGVs have strict height limitations and often carry medium or light loads, these steering modules were difficult to integrate into compact chassis designs.

Limited Functional Demand

In early industrial applications such as automotive manufacturing, AGVs primarily followed fixed routes. Differential drive systems were sufficient for these tasks. Although bidirectional movement required dual differential-drive assemblies, the advantages of omnidirectional steering were not yet fully recognized.

Localization and Cost Barriers

Core steering wheel technologies were largely dependent on imports, while domestic development remained at an early stage. The resulting high costs limited adoption among small and medium-sized system integrators.

2.2 Key Advantages of Steering Drive Wheels

Omnidirectional Mobility

By integrating independent steering and drive functions, steering drive wheels support continuous 360° rotation, enabling:

• Lateral movement

• Diagonal movement

• In-place rotation

This allows AGVs to operate efficiently in highly constrained environments.

High Positioning Accuracy

Integrated servo steering systems provide excellent motion control, enabling repeatable positioning accuracy within ±5 mm, making them ideal for precision docking applications.

High Integration Level

A single steering drive wheel module can replace multiple differential drive assemblies, simplifying chassis architecture and maximizing internal space utilization.

Strong Load Adaptability

Modular steering drive wheel designs are available for applications ranging from light-duty AGVs to multi-ton heavy-load vehicles, delivering industrial-grade reliability across various scenarios.

2.3 Industry Trends and Domestic Innovation

Leading Chinese manufacturers such as Yikong Intelligent have made significant breakthroughs in steering drive wheel technology, overcoming historical limitations associated with imported products.

Ultra-low-profile steering drive wheel solutions have substantially reduced installation height, making them highly compatible with modern under-riding AGVs. Integrated designs now combine:

• Drive motor

• Steering motor

• Brake system

• Absolute encoder

within a single compact module.

Steering repeatability can be maintained within ±0.5°, significantly reducing integration and commissioning complexity for AGV manufacturers.

Today, the primary development trends for steering drive wheel technology include:

• Miniaturization

• Modularization

• Higher precision

• Greater integration

2.4 Typical Applications

• Omnidirectional under-riding AGVs

• Lift-top AGVs

• Automotive manufacturing

• 3C electronics production

• New energy battery manufacturing

• Heavy-duty AGVs with payloads exceeding 1,000 kg