# A Review of Coordinated Control Technology for Chassis of Distributed Drive Electric Vehicles
## 3 Two-Dimensional Coordinated Control Strategies for DDEV Chassis
### Lateral and Longitudinal Coordinated Control Strategies  
DDEV chassis possess independent driving and braking torque control capabilities at each wheel, offering unprecedented opportunities to enhance vehicles' lateral handling stability, path tracking accuracy, and overall safety [49; 50]. However, an inherent and complex nonlinear coupling relationship exists between the vehicle's longitudinal and lateral motions. This coupling effect is particularly pronounced in extreme driving conditions such as high-speed cornering and emergency obstacle avoidance, or on slippery, uneven, and varying road conditions. For example, longitudinal acceleration or deceleration behavior directly alters the vertical load distribution on the tires, thereby affecting their cornering stiffness and the maximum lateral adhesion force they can generate [51]. Conversely, lateral steering maneuvers can also introduce disturbances to the vehicle's maintenance of longitudinal speed and driving stability [52]. Therefore, by implementing effective longitudinal-lateral dynamics coordinated control, it is possible to further expand the vehicle's handling stability boundaries and overall dynamic performance limits, while avoiding redundancy in distributed-drive control functions and potential dynamic conflicts [21; 53]. Currently, control strategies based on coordination among various subsystems have become a widely adopted technical path in this field. In the lateral and longitudinal stability control of chassis, common subsystems include AFS [54], Active Rear Steering (ARS) [55], Four-Wheel Steering (4 WS) [12], Direct Yaw moment Control (DYC) [56], the Anti-lock Braking System (ABS) [57], Traction Control System (TCS) [58], differential braking systems [59], and differential steering systems [60]. Existing research primarily \begin{table}
\begin{tabular}{c c c c} \hline
**Architecture** & **Decentralized** & **Centralized** & **Hierarchical** \\ \hline Disadvantages [39; 45] & Difficult to achieve true coordination, prone to conflicts & High computational load, complex development, high risk of single-point failure & Relatively complex design, inter-layer coordination is key \\ \hline Coordinated control capability [46; 47] & Weak, difficult to leverage DDEV advantages & Strong, theoretically capable of achieving optimal coordination & Strong, achieved through mid-level coordination and control distribution \\ \hline Fault tolerance capability [48] & Relies on the fault tolerance of individual subsystems & Controller failure has a significant impact & Fault tolerance strategies can be designed at different levels, good redundancy \\ \hline Development complexity [39] & Low & High & Medium to high \\ \hline DDEV applicability [48] & Limited, difficult to fully utilize over- actuation characteristics & Theoretically suitable, but practical implementation is challenging & Very suitable \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._focuses on the integration and optimization of advanced steering systems (particularly represented by AFS) and DYC. Therefore, coordinated control between these two has naturally become a research focus for many scholars. Figure 4 shows a typical hierarchical coordinated control framework for the longitudinal and lateral dynamics of a distributed-drive chassis. In this framework, the upper-layer controller receives and processes steering and pedal operation commands from the driver and fuses environmental perception information. Based on the vehicle dynamics model, this layer is responsible for determining the desired vehicle motion state, for example, calculating the desired additional yaw moment required to maintain vehicle yaw stability. The core task of the middle-layer coordination controller is to rationally and optimally distribute the generalized control commands (such as the desired total longitudinal force and additional yaw moment) generated by the upper-layer controller to the individual independent actuators. Finally, the bottom-layer controller is responsible for execution.