# Research on Obstacle Avoidance Replanning and Trajectory Tracking Control Driverless Ferry Vehicles
## 6 Conclusions  
The driverless ferry vehicle is the topic of this research. We studied how the too frequent acceleration- and braking-mode switching affects the comfort and stability of speed control for the ferry and designed the acceleration/braking switching module with an acceleration-tolerance interval. To study the problem of obstacle avoidance replanning and trajectory tracking control, a lateral motion controller with the function of obstacle avoidance replanning and the coordinated control of lateral motion and longitudinal motion were designed.  
(1) Facing the problem of frequent switching between acceleration and braking modes of driverless ferry vehicles, a problem which affects the comfort and stability of speed control, according to the fuzzy control theory and PID control algorithm, the fuzzy PID longitudinal motion controller was designed, the braking control model was built, and the acceleration tolerance range of acceleration and braking was designed. It ensures the longitudinal speed tracking accuracy of the driverless ferry vehicle and the stability of  
Figure 25: Comparison of simulation results of control algorithms when the obstacle is behind. (**a**) Comparison between obstacle avoidance replanning and trajectory tracking. (**b**) Comparison of front wheel angle. (**c**) Comparison of yaw angle tracking effect. (**d**) Comparison of lateral position error.  
the switching between acceleration and braking. (2) We were faced with the problem that the driverless ferry vehicle encounters unknown obstacles on the road, which affects the normal planning and tracking control of the vehicle, and ultimately causes the driverless ferry vehicle to be unable to drive normally. We performed a tire lateral deflection stiffness estimation using the vehicle dynamics model as a predictive model, based on which the lateral motion controller for the obstacle avoidance replanning function was designed. Transforming trajectory tracking becomes a secondary planning problem with constraints, and the obstacle avoidance function is designed by a point mass model and obstacle avoidance function. (3) For better tracking control, the speed-planning module predictive time-domain two-dimensional look-up table module was designed to coordinate the horizontal and longitudinal motion of the driverless ferry vehicle. The coordinated control offered by this method is shown in the simulation results; the planning and tracking effects of the driverless ferry vehicle were significantly improved, which validates the validity of the methodology devised in the paper.  
To date, this work still has limitations. The coordinated control algorithm in this paper only carries out simulation experiments to verify its effectiveness, but it still needs to be verified in the real vehicle. Therefore, in the future research work, we can further confirm the effectiveness of the coordinated control algorithm in the real vehicle and analyze its control effect. And the potential practical impact of the scheme proposed in this paper is discussed. A further exploration of how these improvements mentioned in the scheme affect the overall ferry operation efficiency, passenger safety, and system reliability is needed.  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
The authors declare no conflicts of interest.