How to select a robot chassis structure?

With the gradual advancement of intelligent technology, robotic chassis have evolved from simple mobile carriers into critical structural components that determine overall machine performance. Their structural design directly dictates whether a robot can climb steep, slippery slopes at 30-degree inclines with stability, operate continuously in pesticide-filled vegetable greenhouses, or execute 360-degree turns on the spot within narrow utility tunnels.

The robot chassis structure serves as the fundamental platform for robotic motion, with its core functions being the provision of mobility and execution capabilities. The chassis structure primarily consists of two major components: the mechanical structure and the control system.

The mechanical structure serves as the physical carrier of the chassis, determining the robot's movement capabilities and load-bearing capacity. Common types of mechanical structures include:

Wheeled chassis represent the most common and mature mobility mechanism in mobile robots. They offer advantages such as simple structure, low manufacturing costs, high motion efficiency, and mature control algorithms. They are particularly well-suited for flat or slightly undulating indoor/outdoor surfaces (e.g., warehouses, offices, shopping malls, factories).

Based on drive configuration, systems can be categorized into two-wheel differential drive (where independent speed control of left and right wheels enables steering, suitable for robotic vacuum cleaners, material handling robots, and automated guided vehicles (AGVs), etc.) and four-wheel drive (such as logistics robots, agricultural robots, and inspection robots, etc.).

4D 4S Robot Chassis(Steering wheel drive motor as a driving method): Achieves highly agile motion control by independently controlling each wheel's steering angle and drive speed. This configuration enables multi-degree-of-freedom movement, including 360° on-the-spot rotation, omni-directional translation, diagonal movement, and curved path tracking without relying on traditional differential steering mechanisms. Common configurations include:

Single-Steering wheel drive motor Configuration: Features a single steerable drive wheel, typically paired with fixed or passive wheels.

Dual Steering wheel drive motor Configuration: Two independent steering wheels, typically arranged front-to-back or diagonally, enable precise steering and lateral movement. Ideal for compact AGVs or service robots operating in confined spaces.

Quad-Steering wheel drive motor configuration: Four fully independent steering wheels (each capable of 360° rotation and independent drive) represent the highest mobility configuration, enabling true omnidirectional movement. Commonly used in industrial-grade AGVs (Automated Guided Vehicles), warehouse robots, or logistics robots.

Differential Chassis: Achieves steering and forward/reverse motion by controlling the speed difference between the left and right wheel sets. When wheel speeds are equal, the vehicle travels straight; when one side spins faster, it turns toward the opposite direction. Each wheel is typically driven by an independent motor (such as a DC motor or brushless motor) and equipped with an encoder for speed feedback. Common configurations include:

Two-wheel differential robot chassis: Drives only two wheels (typically rear or center wheels), with the remaining wheels functioning as passive caster wheels to provide basic maneuverability. Examples include warehouse goods-handling robots capable of agile turning in narrow aisles.

Four-wheel differential robot chassis: All four wheels are drivable, typically employing two sets of differentials (one per axle) or fully independent all-wheel drive for enhanced traction. It offers superior stability and load capacity, suitable for rugged terrain or heavy-duty applications. Examples include agricultural robots or outdoor inspection equipment that handle slopes and uneven surfaces. However, it has a larger turning radius and cannot perform pure sideways movement.

Specialized Chassis: Refers to non-generic wheeled or non-wheeled mobile platforms designed for specific environments or tasks. Common types include Ackermann steering chassis and tracked chassis, which are often employed to navigate complex terrain or meet precise steering requirements.

The control system serves as the “brain” of the chassis, responsible for sensing the environment, processing information, and issuing motion commands. Its core components include:

Sensors: Used to acquire environmental information and self-status, such as distance sensors (radar, ultrasonic), wheel speed sensors (encoders), inertial measurement units (IMUs), and image sensors (cameras).

‌Controller: Typically based on a microprocessor (e.g., STM32 chip) or embedded system, it parses commands, computes control algorithms (e.g., PID control), and sends instructions to the driver.‌

‌Drive System: Comprising motors (e.g., DC motors, permanent magnet synchronous motors) and drivers, it receives commands from the controller and drives the wheels.‌

‌Power System: Supplies energy to the entire chassis, usually via a rechargeable battery pack.

The robot chassis, as the core foundation for motion and execution, directly determines whether it can traverse muddy slopes, spray pesticides in farm fields, or turn around in narrow passages.