# A Review of Recent Advances in Roll Stability Control in On-Road and Off-Road Vehicles
## 5 Roll Stability Control in Off-Road Vehicles
### Active Roll Stability Control Methods
#### 5.3.3 Active Steering  
Similarly to the active steering control principles used in road vehicles, some agricultural machinery reduces the rollover moment and prevents tipping by generating lateral forces through tire steering. As shown in Figure 8b, [PERSON] et al. [121] addressed the rollover issue in agricultural tractors by establishing a nonlinear time-varying attitude dynamic model using the Lagrangian method. They proposed a rollover prevention control strategy combining SMC and active steering. By designing the SMC algorithm based on dynamic attitude stability indicators and variable structure theory, they successfully transformed the tractor roll and pitch motions into attitude recovery control. Simulation and scale model test results demonstrated that the SMC-AS strategy effectively reduced the tractor's rollover stabilization time by 46.07%, showing excellent robustness and control performance under various operating conditions. This provides an effective technical solution for preventing tractor rollover accidents. Meanwhile, [PERSON] et al. [122] addressed the issue of fatal rollover accidents in agricultural tractors by developing a low-cost rollover prevention control system based on active steering technology. They established a three-degree-of-freedom rollover dynamic model that incorporates an automatic steering system and proposed a  
Figure 8: Representative direct torque control and active steering in agricultural machinery: (**a**) active anti-rollover system based on control moment gyroscope [132]; (**b**) active anti-rollover control for tractor, integrating sliding mode control and active steering [121].  
tilt angle adjustment scheme based on adaptive sliding mode control. The system also designed a front-wheel angle tracking controller using internal model control (IMC) theory. Simulation results showed that the system can compute stability indicators in real time and maintain them within a safe range by adjusting the front-wheel angle (with a stability indicator error of <5%), providing a practical solution to reduce tractor rollover accidents.  
In addition to tractors, active steering technology for other agricultural machinery has also received widespread attention. [PERSON] et al. [38] addressed the issue of the complex installation and vulnerability of traditional steering angle measurement methods in agricultural environments. They proposed a novel dynamic measurement method based on vehicle attitude information and non-contact attitude sensors. Experimental results showed that the proposed method significantly improved measurement reliability without relying on vehicle kinematic models or repeated calibration, effectively avoiding issues such as mud blockage and cable damage. Furthermore, [PERSON] et al. [138] proposed an active steering system for a new four-wheel independently driven agricultural electric vehicle, based on MPC and direct yaw moment control (DYC). Simulation and experimental results demonstrated that when the steering angle was set to 5\({}^{\circ}\), the steering error was below 0.22%, and the yaw moment error was less than 0.17%, verifying that the system could achieve precise autonomous steering and effectively reduce crop crushing in the field.