1. Motivation: Lane detection is a critical component of autonomous vehicles, and essential for ensuring their safe and efficient navigation. Effective navigation solutions for affordable devices could contribute to the increasing use of robots and autonomous vehicles in a wide range of applications.
2. Problem statement: In recent years, several models have been proposed to improve the accuracy and performance of this activity, however, little is known about practical real-time implementations of these models in small-scale vehicles and low-cost devices, with limited computing and memory resources. Additionally, the suitability of deep learning models (DL) for this type of device remains unclear.
3. Approach: This report presents the results of a systematic mapping study aimed at gaining a deeper understanding of the models, techniques, hardware, and systems that have been employed for lane recognition on these devices. Additionally, an experimental evaluation was conducted for testing different models for lane detection in real-time on miniature cars, identifying the best-performing models. Three methods were analysed: (1) a model using traditional image processing techniques, (2) an end-to-end DL model proposed by Nvidia, which directly predicts angles, and (3) an ultrafast lane detection DL model, which predicts lane boundaries. Our hypothesis is that (3) is the best-performing model due to its loss calculation formula, which is based on local and global features and could detect lanes better.
To train the DL models, labelled data is required. In this study, an automated approach was employed for estimating the labels, which represent the steering angles or define the road markings used in the recognition process.
4. Results: The mapping study shows that a few models have been implemented in real-time applications for this kind of device. Among the most criticized aspects of them is the high processing and decision-making times. Another relevant point is that, although the publications provide insights into their approaches consisting of software-hardware systems, they do not allow a comparative evaluation among the models. The experiments conducted in this study enabled a robust and impartial comparative analysis among the methods. The results indicate that Model 1, which utilizes traditional image processing techniques, achieved a frame rate of 758 frames per second (FPS) without using any GPU, and with a memory usage of only 0.22 GB. However, it also demonstrated some scalability issues and lower accuracy compared to the other models, with a correct angle prediction rate of 86%. Among the DL methods, the ultra-fast model (3), which predicts lane boundaries, outperformed the end-to-end Nvidia model (2), which directly predicts steering angles. The former achieved a higher level of performance compared to the latter, with an accuracy of 95% compared to 92%. Despite its superior performance, the ultra-fast model has the disadvantage of requiring a longer processing time when run without a GPU, resulting in a lower frame rate of only 0.18 FPS. However, some adjustments were made to this model, resulting in an increase in its frame rate to 13 FPS while maintaining the same level of accuracy. On the other hand, the end-to-end model maybe simpler to implement and faster but is more prone to producing unreliable results when faced with unbalanced data.
5. Conclusions: In summary, the results of this study demonstrate the adequacy of DL models for addressing the lane detection recognition, even on low-cost devices, as long as minimum capacity and memory requirements are met. These models yield significantly more robust results and offer superior performance in handling variations in geometry and luminosity. A comparative analysis based on accuracy, memory consumption, and processing time is provided and serves as a useful guide for selecting the most appropriate model. It is essential to evaluate other traditional techniques and deep learning models. Finally, further research is needed to improve solutions, such as lighter backbones, libraries and tools, specifically tailored for mobile, embedded, and edge devices.