• lidar-optimization

    Improving Perception via Sensor Placement: Designing Multi-LiDAR Systems for Autonomous Vehicles

    Sharad Chitlangia, Akhil Agnihotri, Zuxin Liu, Ding Zhao.

    CVPR 2021, Autonomous Driving: Perception, Prediction and Planning Workshop.   [arxiv] [talk] [code]

    Abstract: Recent years have witnessed an increasing interest in improving the perception performance of LiDARs on autonomous vehicles. While most of the existing works focus on developing novel model architectures to process point cloud data, we study the problem from an optimal sensing perspective. To this end, together with a fast evaluation function based on ray tracing within the perception region of a LiDAR configuration, we propose an easy-to-compute information-theoretic surrogate cost metric based on Probabilistic Occupancy Grids (POG) to optimize LiDAR placement for maximal sensing. We show a correlation between our surrogate function and common object detection performance metrics. We demonstrate the efficacy of our approach by verifying our results in a robust and reproducible data collection and extraction framework based on the CARLA simulator. Our results confirm that sensor placement is an important factor in 3D point cloud-based object detection and could lead to a variation of performance by 10% ~ 20% on the state-of-the-art perception algorithms. We believe that this is one of the first studies to use LiDAR placement to improve the performance of perception.

  • scenario-generation

    Multi-Vehicle Interaction Scenarios Generation & Interpretable Traffic Primitives and Gaussian Process Regression

    Wenshuo Wang, Weiyang Zhang, Jiacheng Zhu, Akhil Agnihotri, Ding Zhao.

    IEEE Intelligent Vehicles Symposium 2020.   [arxiv] [code]

    Abstract: Generating multi-vehicle interaction scenarios can benefit motion planning and decision making of autonomous vehicles when on-road data is insufficient. This paper presents an efficient approach to generate varied multi-vehicle interaction scenarios that can both adapt to different road geometries and inherit the key interaction patterns in real-world driving. Towards this end, the available multi-vehicle interaction scenarios are temporally segmented into several interpretable fundamental building blocks, called traffic primitives, via the Bayesian nonparametric learning. Then, the changepoints of traffic primitives are transformed into the desired road to generate collision-free interaction trajectories through a sampling-based path planning algorithm. The Gaussian process regression is finally introduced to control the variance and smoothness of the generated multi-vehicle interaction trajectories. Experiments with simulation results of three typical multi-vehicle trajectories at different road conditions are carried out. The experimental results demonstrate that our proposed method can generate a bunch of human-like multi-vehicle interaction trajectories that can fit different road conditions remaining the key interaction patterns of agents in the provided scenarios, which is import to the development of autonomous vehicles.

  • image

    A Convolutional Neural Network Approach Towards Self-Driving Cars

    Akhil Agnihotri, Prathamesh Saraf, Kriti Bapnad.

    IEEE India Conference 2019.   [arxiv] [code]

    Abstract: A convolutional neural network (CNN) approach is used to implement a level 2 autonomous vehicle by mapping pixels from the camera input to the steering commands. The network automatically learns the maximum variable features from the camera input, hence requires minimal human intervention. Given realistic frames as input, the driving policy trained on the dataset by NVIDIA and Udacity can adapt to real-world driving in a controlled environment. The CNN is tested on the CARLA open-source driving simulator. Details of a beta-testing platform are also presented, which consists of an ultrasonic sensor for obstacle detection and an RGBD camera for real-time position monitoring at 10Hz. Arduino Mega and Raspberry Pi are used for motor control and processing respectively to output the steering angle, which is converted to angular velocity for steering.

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    A Review on Superplastic Forming of Ti-6Al-4V Alloy

    Akhil Agnihotri, Akula Pratyush, Amit Kumar Gupta.

    Journal of Alloys and Compounds.   [arxiv]

    Abstract: This paper presents a review on the superplastic forming of Ti-6Al-4V alloy, which has been used to manufacture parts of complex shapes and geometries. This paper outlines the major work carried out on this front in the past three decades. It covers various aspects related to experimental setups, including the manufacture of dies and their modifications to maintain alloy thickness uniformity after forming. A detailed study of the process parameters has also been done to note the most important physical conditions required for successful forming. This is followed by the influence of microstructure, modern applications of superplastic forming of different titanium alloys and is concluded with an insight into the future work and progress in this field.


  • scenario-generation

    Min-max Optimization of a LiDAR Sensor

    CARLA simulator, Weighted convex optimization, Object detection.

    Abstract: A LiDAR provides accurate 3D views and precise distance measurements under uncertain driving conditions. However, its implementation remains costly. To tackle this issue an effort to maximize the utility of the LiDAR is made. Since, at a high-level, the task of a LiDAR is to detect objects, an easy-to-evaluate cost function which minimizes the maximally undetected subspace is used. Different LiDAR configurations in the CARLA simulator are used and for each, depth camera images are converted to LiDAR point clouds since CARLA’s LiDARs are not accurate. The perception area is used to construct a design procedure to solve the optimization problem described above based on weighted region of interests around the vehicle. The weighted regions are obtained when a subspace cuts a cube and the cube’s weight is incremented by 1. Now, the task becomes to maximize for all LiDAR configurations and find the optimum for a particular number of LiDARs.


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    Inverse Kinematic Algorithms for Spatially Hyper Redundant Bodies

    Metaheuristic optimization, inverse kinematics, Closed-loop control algorithm design.

    Abstract: Spatially hyper redundant systems have more number of controllable Degrees of Freedom (DOF) as compared to their actual DOF. These systems have infinite number of solutions for a given state space reach making it complex to develop proper inverse kinematic solution. Adapting the optimization methods only help to arrive at the promising Inverse Kinematic (IK) solution. The second part of the project involves implementation and simulation of computed torque control method for a 2-DOF manipulator sing MATLAB/Simulink. Computed Torque Control is a powerful non-linear controller which uses feedback linearisation to compute the required arm torques required for movement. The robot model is designed using the SimMechanics library of Simulink.


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    Galerkin Finite Element Analysis of Below-knee Prosthesis

    Crank-Nicolson scheme, weak Galerkin, Stress analysis.

    Abstract: This study aims to identify the best possible material for production of liners for prosthetic limbs. Based on the standard Galerkin finite element method in space and Crank-Nicolson difference method in time, the semi-discrete and fully discrete systems are constructed. The code is written in C++ and MATLAB, and deformation plots of different loading conditions for different materials are analyzed. The code is a general approach written for a (n x m) meshing domain and can be refined as per the user preference based on the desired accuracy. The code was validated with simulations on ANSYS Static Structural providing a green signal for further research. Further work to incorporate the nonlinear constitutive behavior of silicone will be done to test whether silicone is really the best economic material in the market available.