As the foundation of intelligent systems, machine vision perceives the surrounding environment and provides a basis for decision-making. Object detection is the core task in machine vision. 3D object detection can provide object steric size and location information. Compared with the 2D object detection widely studied in image coordinates, it can provide more applications of detection systems. Accurate LiDAR data has a stronger spatial capture capability and is insensitive to natural light, which makes LiDAR a potential sensor for 3D detection. Recently, deep neural network has been developed to learn powerful object features from sensor data. However, the sparsity of LiDAR point cloud data poses challenges to the network processing. Plenty of emerged efforts have been made to address this difficulty, but a comprehensive review literature is still lacking. The purpose of this article is to review the challenges and methodologies of 3D object detection networks using LiDAR data. On this account, we first give an outline of 3D detection task and LiDAR sensing techniques. Then we unfold the review of deep 3D detection networks with three kinds of LiDAR point cloud representations and their challenges. We next summarize evaluation metrics and performance of algorithms on three authoritative 3D detection benchmarks. Finally, we provide valuable insights of challenges and open issues.

Decision-making is still a significant challenge to realize fully autonomous driving. Using deep reinforcement learning (DRL) to solve autonomous driving decision-making problems is a recent trend. A common method is to encode surrounding vehicles in a grid to describe the state space to help DRL network extract the scene features. However, in the process of human driving, surrounding vehicles at different positions have different contributions to decision-making. Meanwhile, the network is difficult to fully extract useful features in a sparse state, which can also lead to catastrophic actions. Therefore, this work proposes a spatial attention module to calculate different weights to represent different contributions to decision-making results. And a channel attention module is proposed to fully extract useful features in sparse state features. These two attention modules are integrated into dueling double deep Q network, named D3QN-DA, as a high-level decision-maker of a hierarchical hierarchical control structure based decision-making system. To improve agent performance, an emergency safe checker is introduced in this system. And the agent is trained and test with a designed reward function from safety and efficiency in simulation. The experimental results show that the proposed method increases the safety rate by 54%, and the average explore distance by 30%, which is safer and more intelligent for the decision-making process of automatic driving.

Feature Pyramid Network (FPN) builds a high-level semantic feature pyramid and detects objects of different scales in corresponding pyramid levels. Usually, features within the same pyramid levels have the same weight for subsequent object detection, which ignores the feature requirements of different scale objects. As we know, for most detection networks, it is hard to detect small objects and occluded objects because there is little information to exploit. To solve the above problems, we propose an Enhanced Feature Pyramid Object Detection Network (EFPN), which innovatively constructs an enhanced feature extraction subnet and adaptive parallel detection subnet. Enhanced feature extraction subnet introduces Feature Weight Module (FWM) to enhance pyramid features by weighting the fusion feature map. Adaptive parallel detection subnet introduces Adaptive Context Expansion (ACE) and Parallel Detection Branch (PDB). ACE aims to generate the features of adaptively enlarged object context region and original region. PDB predicts classification and regression results separately with the two features. Experiments showed that EFPN outperforms FPN in detection accuracy on Pascal VOC and KITTI datasets. Furthermore, the performance of EFPN meets the real-time requirements of autonomous driving systems.

Object detection plays an important role in autonomous driving systems. LiDAR is widely used in autonomous driving vehicles and robots as a sensor for environmental perception. Recently, the development of computational power and deep learning technology makes it possible to classify and locate objects from LiDAR point cloud in a single end-to-end learnable network. However, objects are sparsely distributed in large point cloud field, and are always been partly scanned by LiDAR, which pose a challenge for accurate and rapid object positioning and classification from the raw point cloud. In this paper, we introduce a new single-shot refinement neural network for fast and accurate 3D object detection from the raw LiDAR point cloud. Firstly, we exploit self-attention mechanism in main object detection branch to enhance object feature representation. Secondly, we apply deformable convolution for learning adaptive receptive fields to fully capture the features of rotating and partially visible objects. Thirdly, an object refinement branch is introduced to produce a finer regression of objects upon the primary estimation from the main detection branch. All proposed modules have been proven to effectively improve the accuracy of object detection. Our method is evaluated on KITTI 3D detection benchmark and achieves state-of-the-art results while maintains real-time efficiency. Furthermore, real-time test in autonomous driving vehicle demonstrates that our method is robust to 16 channels LiDAR and can meet the demands of accuracy, efficiency, and visibility of object detection in various urban scenarios.

With the improvement of human life quality, life expectancy generally increases. As a result, more and more elderly people living alone appear. Recently, the safety problems of the elderly living alone have attracted more and more attention from the public. Due to living alone, the elderly cannot be found at the first time when an accident occurs indoors or out, and the rescue time is delayed. This article proposes a way to use the speed up module to realize real-time face detection on the Raspberry Pi and optimize the processing of PIR sensor signals and write a logic system based on the camera and PIR signals to record and analyze the life of the elderly living alone and warning system to their family members.