# Steering Assist Control for Bicycles with Variable Trail Effect
## 4 Conclusions  
In this study, a steering assist control has been proposed and realized to recover from the deterioration of maneuverability, which is caused by the increase in the moment of inertia around the bicycle handlebar axis and the shift in the center of gravity when luggage is placed in the front basket of the bicycle handle or when a child is seated in the child seat. These previous studies only focused on the steering assist by applying some torque to the bicycle handlebar axis. However, when actually riding a bicycle, the bicycle is steered not only by the handlebar but also by a mechanism called the \"trail effect\" in which the handlebar is automatically steered when the bicycle is inclined in the roll angle direction. Therefore, we considered it is necessary to design and realize an assist control system that also takes the trail effect into account in order to recover and improve bicycle maneuverability. An experimental bicycle equipped with a power steering mechanism was developed with the two following types of control method: the control method to apply an assist torque proportional to the steering torque generated by the user to the handlebars, and the control method to realize a variable trail effect in which the front wheel is steered in conjunction with the roll angle of the bicycle. The investigation of changes in bicycle behavior depend on the load, and it has been found that the overshoot of the steering angle increased as the load increased, although there were individual differences. The effectiveness of the proportional assist control and the variable trail control in assisting bicyclists with a load has been verified through experiments using the developed bicycle. The results show that the variable trail control reduced the overshoot of the steering angle when the bicycle turns compared to that of the proportional control. The frequency analysis of the steering angle also confirms that the variable trail control attenuates the vibration caused by the swing of the handlebars when the bicycle turns. From them, it has been concluded that variable trail control, which also takes trail effects into account, is more effective in restoring the maneuverability of bicycles. As a future work, model-based assist  
Figure 17: **(a)** Frequency component without loading (rider 3). **(b)** Frequency components during variable trail control (rider 3). **(c)** Frequency components when loaded (rider 3). **(d)** Frequency components during proportional assist control (rider 3).  
control will be investigated to improve the steering assist by incorporating not only the trail effect but also the dynamics of bicycles, such as the gyroscopic effect.  
Resources, Y.S. and K.K.; Writing--original draft, T.K.; Writing--review & editing, M.I. All authors have read and agreed to the published version of the manuscript.  
This study was partially supported by JSPS KAKENHI Grant Number 24K01008.  
Not applicable.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.