# A Review of Coordinated Control Technology for Chassis of Distributed Drive Electric Vehicles
## 3 Two-Dimensional Coordinated Control Strategies for DDEV Chassis
### Longitudinal and Vertical Coordinated Control Strategies  
Under the DDEV chassis architecture, significant coupling effects exist between the vehicle's longitudinal and vertical dynamic behaviors [109; 110]. Specifically, the longitudinal motion (such as acceleration and braking) and vertical motion (such as suspension's compression and rebound, vehicle body pitch) during vehicles' operation constitute a dynamic interactive system. This coupling relationship exhibits a clear bidirectional nature: longitudinal control actions (such as driving or braking) directly cause a shift in the vehicle's center of gravity, thereby inducing vertical dynamic responses (like vehicle pitch and changes in suspension travel). Conversely, vertical disturbances (such as road unevenness or impacts) affect longitudinal traction/braking performance by altering tires' normal loads and may even lead to traction force fluctuations or sudden changes in adhesion conditions. Simultaneously, this coupling relationship also has a dual nature: On the one hand, it poses a challenge to traditional decoupled control strategies, as control input in a single direction inevitably causes responses in other degrees of freedom, increasing the system design complexity. On the other hand, this characteristic also provides new opportunities for the development of integrated control strategies. Thanks to the independent controllability of each wheel drive unit in DDEV chassis and the introduction of vertical executive units like active suspension, cross-dimensional information fusion and control coordination can be achieved at the control system level. For example, by precisely adjusting the longitudinal driving/braking torque of each wheel, the vehicle pitch attitude can be actively regulated to enhance vertical ride comfort and driving stability. Meanwhile, active suspension systems can improve the efficiency of vehicles' longitudinal acceleration response and traction/braking limits by optimizing wheels' normal load distribution. As shown in Figure 8, a typical hierarchical coordinated control framework features a middle-layer coordination controller. This controller decomposes control tasks for various actuators (such as drive motors, active suspension, and braking systems) based on upper-layer commands, control objectives, and boundary conditions. Within this framework, the design of the coordinated control strategy is of crucial importance. At the current stage, longitudinal and vertical coordinated control strategies can be broadly categorized in three ways based on their primary objectives. The first category centers on enhancing ride comfort and vehicle body attitude control. The second focuses \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Coordinated Subsystem** & **Applied Control Algorithm** & **Achieved Control Effect** & **Refs** \\ \hline SAS, differential braking & \begin{tabular}{c} Hierarchical control architecture, \\ SMC used for upper-level \\ controller’s desired yaw and roll \\ moment calculation \\ \end{tabular} & Enhances the vehicle’s lateral stability while maintaining a good roll performance & [43] \\ \hline AFS, ASS, DYC & MPC, tire force allocation algorithm & Significantly improves the vehicle’s path tracking performance and driving stability under different road adhesion coefficients & [107] \\ \hline Multi-axle steering & \begin{tabular}{c} Dual linear quadratic \\ regulator (DLQR) \\ \end{tabular} & Improves the handling stability and ride comfort of the vehicle & [104] \\ \hline AFS, hydro-pneumatic & \begin{tabular}{c} GRNN, PID control \\ \end{tabular} & \
\begin{tabular}{c} Accurately tracks the desired yaw \\ rate and roll angle, improves \\ vehicle handling stability \\ \end{tabular} & [108] \\ \hline AFS, ASS & MAS, MDMPC &
\begin{tabular}{c} Significantly improves the vehicle’s \\ lateral stability, ride comfort, and roll safety during path tracking \\ \end{tabular} & [86] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Lateral and vertical cooperative control strategies.