The task of lateral control is to adjust the direction of the vehicle so that it can travel along the planned path. The difficulty in this process lies in the diversity of road conditions, such as changes in curve curvature, differences in road friction, etc., which will increase the difficulty of lateral control. The input usually includes the vehicle's own status data and the trajectory information output by the path planning module. The output is the steering angle command of the vehicle, which is used to adjust the angle of the steering wheel to make the vehicle drive along the predetermined path. For example, when it detects that the vehicle has deviated from the path, the lateral control system will issue instructions to adjust the steering angle to correct the direction of the vehicle.

Longitudinal control is concerned with speed regulation of the vehicle, aiming to maintain a safe distance and achieve the desired speed. Frequent acceleration and deceleration in urban traffic and requirements for stability on highways test the robustness and adaptability of the longitudinal control algorithm. In addition, in different driving modes (such as economy mode, sports mode), longitudinal control also needs to meet different priority needs, such as energy saving or quick response. Inputs typically include current vehicle speed information and a target speed provided by the planning module. The output is the vehicle's acceleration or throttle/braking commands, which are used to adjust the vehicle's speed. For example, when it detects that the vehicle ahead is slowing down, the longitudinal control system will issue a deceleration command to maintain a safe distance.

Coupled control (or combined control) refers to the comprehensive application of lateral control and longitudinal control to achieve higher-level autonomous driving functions. The difficulty of this task lies in how to smoothly coordinate control instructions in two directions under different scenarios, especially in the case of multi-objective optimization, such as high-speed steering and other operations. In addition, when faced with emergencies, how to respond in a short time is also a major challenge faced by coupled control. Inputs typically include a combination of all sensor data required for lateral and longitudinal control as well as information output from the trajectory planning module. The output is the integrated control instructions, including steering angle and torque instructions, which are used to adjust the direction and speed of the vehicle at the same time.