The 4x4 robot chassis is a high mobility mobile platform with four independent steering wheels and four independent drive wheels, each wheel can be accurately controlled by servo or stepper motors to control the steering angle and drive power, to realize omni-directional freedom of movement, such as lateral movement, in-situ rotation, especially for complex terrain (independent drive to enhance the stability of the obstacle).

The chassis is widely used in industrial automation (AGV logistics, equipment inspection), special fields (explosive rescue, military reconnaissance), scientific research and education (motion control research, competition robots) and service robots (commercial cleaning, agricultural work) and other scenarios, especially suitable for narrow spaces, dynamic environments or high-precision operational needs.

The four-turn, four-wheel-drive robot chassis realizes complex motion control through modular design, and its core components can be disassembled into the following eight modules, with each part working in tandem to achieve omnidirectional movement and terrain adaptability:

1. Drive unit (4 groups)

Drive motors: brushless DC motors (BLDC) or servo motors to provide power output (power range customized according to load requirements).

Reducer: Planetary reducer or harmonic reducer to reduce the speed and increase the torque (reduction ratio is usually 5:1~20:1).

Encoder: magnetic encoder or photoelectric encoder, real-time feedback of wheel speed and position.

Function: Independently control the speed and torque of each wheel, support distributed power distribution (e.g. differential steering, single-wheel obstacle crossing).

2. Steering unit (4 groups)

Steering motor/servo: high-precision servo motor or digital servo (such as RS485 bus servo), to control the steering angle (range 0°~180°, accuracy ±0.1°).

Mechanical transmission mechanism: worm gear or gear set, converting motor rotation into wheel steering angle (anti-backlash design is required).

Limit Sensor: Hall sensor or mechanical limit switch to prevent damage to the structure by steering over-travel.

Function: Realize four-wheel synchronous/asynchronous steering, support in-situ rotation, lateral movement and other omnidirectional motion modes.

3. Wheels and Tires

Type selection:

Standard wheel: made of rubber or polyurethane, suitable for flat ground (e.g. factory AGV).

Off-road wheels: non-slip tires with toothed tread for enhanced grip on soft terrain such as sand and snow.

McNamee wheels: special oblique ball design to simplify omnidirectional movement control (higher cost).

4. Suspension system (optional)

Elastic elements: coil springs, air springs or rubber shock absorbing blocks to cushion the impact of bumpy road surfaces.

Guiding mechanism: double wishbone or multi-link structure to keep the wheels vertically attached to the ground (e.g. mountain robot chassis).

Damping: Hydraulic or magnetorheological shock absorbers dynamically adjust the stiffness to adapt to different terrains.

Function: Improve stability and obstacle-crossing ability (e.g., crossing 20cm steps or gravel roads).

5. Central Controller

Main control chip: ARM Cortex-M7, FPGA or embedded computer.

Motion control algorithm: Integrated inverse kinematics model (e.g. mapping based on Jacobi matrix) to decompose the target speed into commands for each wheel.

Communication interface: CAN bus, RS485, or EtherCAT for high-speed multi-axis synchronized control.

Function: Coordinate 12 degrees of freedom (4 wheels steering + 4 wheels driving), process sensor data, and perform tasks such as obstacle avoidance and path planning.

6. Sensor system

Inertial Measurement Unit (IMU): detects attitude angle, acceleration, and angular velocity.

Odometer/Encoder: records wheel speed and displacement (incremental or absolute encoder).

LiDAR (Laser Radar): builds maps and avoids obstacles.

Depth camera: RGB-D data to aid navigation.

Ultrasonic/IR sensors: proximity obstacle detection.

Function: provide real-time data input for SLAM navigation, dynamic path planning.

7. Power management module

Battery pack: High energy density lithium battery.

BMS (Battery Management System): Monitor voltage, current and temperature to prevent over-discharge/over-charge.

Power Distribution Board: Multiple DC-DC converters to power motors, controllers, and sensors.

Function: Balance range and weight (industrial grade chassis can last up to 4~8 hours).

Four-wheel-drive four-turn chassis With its omnidirectional mobility, adaptability to complex terrain and high degree of freedom control, it can seamlessly adapt to diversified scenarios and become the core mobile platform for industrial, specialty and outdoor operations.