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Recent advances in monocular 3D detection leverage a depth estimation network explicitly as an intermediate stage of the 3D detection network. Depth map approaches yield more accurate depth to objects than other methods thanks to the depth estimation network trained on a large-scale dataset. However, depth map approaches can be limited by the accuracy of the depth map, and sequentially using two separated networks for depth estimation and 3D detection significantly increases computation cost and inference time. In this work, we propose a method to boost the RGB image-based 3D detector by jointly training the detection network with a depth prediction loss analogous to the depth estimation task. In this way, our 3D detection network can be supervised by more depth supervision from raw LiDAR points, which does not require any human annotation cost, to estimate accurate depth without explicitly predicting the depth map. Our novel object-centric depth prediction loss focuses on depth around foreground objects, which is important for 3D object detection, to leverage pixel-wise depth supervision in an object-centric manner. Our depth regression model is further trained to predict the uncertainty of depth to represent the 3D confidence of objects. To effectively train the 3D detector with raw LiDAR points and to enable end-to-end training, we revisit the regression target of 3D objects and design a network architecture. Extensive experiments on KITTI and nuScenes benchmarks show that our method can significantly boost the monocular image-based 3D detector to outperform depth map approaches while maintaining the real-time inference speed., Comment: Accepted by IEEE Transaction on Intelligent Transportation System (T-ITS)

Power-split hybrid electric vehicles (HEV) employ a speed reduction gear (SRG) mainly to enhance acceleration performance. However, the full potentials of an additional gear on fuel economy and acceleration performance have not yet been thoroughly investigated due to a vast design space: 432 configurations with three design variables (i.e. two planetary gear ratios and a final drive gear ratio). In this paper, a systematic speed reduction gear design methodology is proposed to analyze the impact of a speed reduction (multiplication) gear on the performance of input- and output-split HEVs and select an optimal configuration. First, the physical and virtual design spaces of SRG (SMG) are defined and the relationship between two design spaces are identified. Second, performance metrics are evaluated within the virtual design space using the proposed simplified lever. The proposed approach completely eliminates the redundancy present in the physical design spaces, and thus, the impact of SRG (SMG) on the performance of input- and output-split configurations can be analyzed with the minimum computational burden. Lastly, the selected gear ratio is converted back to the physical planetary gear connections. The results confirm that SRG (SMG) can potentially either improve or deteriorate the acceleration performance and the fuel economy of split HEVs. Therefore, the full potential of speed reduction or multiplication gear should be thoroughly analyzed when designing split hybrid electric vehicles.

Predicting future motions of surrounding vehicles and driver’s intentions are essential to avoid future potential risks. The predicting future motions, however, is very challenging because the future cannot be deterministically known a priori and there are infinitely many possible future trajectories. Prediction becomes far more challenging when trying to foresee distant future. This paper proposes a probabilistic motion prediction algorithm that can accurately compute the likelihood of multiple target lanes and trajectories of surrounding vehicles by using the artificial neural network; more specifically radial base function network (RBFN). The RBFN prediction algorithm estimates the likelihood of each lane being the driver’s target lane in categorical distributions and the corresponding future trajectories in parallel. In order to demonstrate the effectiveness of the proposed prediction algorithm, it is applied for the predictive cruise control problem. Chance-constrained model predictive control (CCMPC) is utilized because the chance constraints in CCMPC can handle collision uncertainties associated with future uncertainties from the proposed prediction algorithm. The RBFN-based CCMPC simulation is conducted for several risky cut-in scenarios and compared with the state-of-the-art Interactive Multiple Model (IMM)-based prediction algorithm. The simulation results show that the RBFN-based CCMPC achieves higher collision avoidance success rate than that of the IMM-based CCMPC while using smaller actuator inputs and providing higher passenger comforts. Furthermore, the RBFN-based CCMPC showed high robustness to false braking during near lane-change (lane-keeping) scenarios.

There has been an increasing level of demand for faster, safer and greener transportation systems with higher levels of capacity and convenience, though the implementation of transportation systems overall is often restricted by geographical limitations, presenting a challenge to scientists and engineers in the field. However, we have been witnessing the evolution of the transportation systems over the last few decades, and at present we are facing a new era of intelligent transportation systems (ITS) empowered by artificial intelligence (AI) technologies. There have been classification, deep learning, and reinforcement learning techniques, to name a few, which collectively have enabled almost all technical elements of the ITS. For example, autonomous vehicle technologies are now mature enough to introduce self-driving cars, taxis, buses, and trucks on the roads and streets; traffic signals are controlled by AI-based systems for far more enhanced traffic efficiency; and machine learning based on big data is improving the operational performance of transportation systems to the next level of safety, efficiency, and sustainability.

The lane keeping system (LKS), a promising driver assistance system, is essential for autonomous vehicles. In real-world road conditions, it can be quite challenging because LKS must stay within the lane without causing passenger discomfort while both disturbances (e.g., road curvature, wind gusts, and hydroplaning) and model uncertainties in parameters [e.g., vehicle mass, center of gravity (CG), and tire cornering stiffness] are present. In this paper, the performance limits and tradeoffs between three performance criteria (lane tracking, stability robustness, and passenger comfort) are first investigated by exploring the entire design space of three prominent controllers, i.e., proportional–integral–derivative, linear–quadratic–Gaussian, and H-infinity ( $\text{H}_{\infty }$ ). Then, a sensitivity study on the vehicle parameters is conducted in order to investigate the impact of the parameters on the three performance metrics. Based on the aforementioned studies, this paper concludes that a robust controller can provide the maximum performance limit with respect to the lane tracking and stability robustness, when properly designed. However, it is observed that the robust controller is still sensitive to a few design and model parameters, such as look-ahead distance and CG. Therefore, the sensitivity study suggests that for vehicles with excessive mass and CG changes, such as SUVs and trucks, the adaptation of controller and look-ahead distance may be necessary to maximize both tracking performance and passenger comfort over a wide range of vehicle speeds.

In order to ensure reliable autonomous driving, the system must be able to detect future dangers in sufficient time to avoid or mitigate collisions. In this paper, we propose a collision risk assessment algorithm that can quantitatively assess collision risks for a set of local path candidates via the lane-based probabilistic motion prediction of surrounding vehicles. First, we compute target lane probabilities, which represent how likely a driver is to drive or move toward each lane, based on lateral position and lateral velocity in curvilinear coordinates. And then, collision risks are computed by incorporating both model probability distribution of lanes and a time-to-collision between a pair of predicted trajectories. Finally, collision risks are plotted on a trajectory plane that represents each set of the tangential acceleration and the final lateral offset of local path candidates. This collision risk map provides intuitive risk measures, and can also be utilized to determine a control strategy for a collision avoidance maneuver. Validation of the model is conducted by comparing the model probabilities with the maneuver probabilities derived from the next generation simulation database. Furthermore, the effectiveness of the proposed algorithm is verified in two driving scenarios, preceding vehicle braking and cut-in, on a curved highway with multiple vehicles.