Research Projects

On-going project: Autonomous Wind Turbine Blade Crack Inspection Using a Speed-Regulated Robot

Summary

This paper presents the design of an autonomous wind turbine blade (WTB) crack inspection system, which consists of a crack detection subsystem and a quadrotor flight control subsystem. In practice, the high speed of the quadrotor always causes image blurry, which will lead to a crack detection failure. The novelty of this paper is that the proposed quadrotor flight control subsystem can avoid this problem. First, the appropriate speed range that can avoid image blurry is obtained; then, a speed regulation controller is developed to regulate the flying speed of the quadrotor within the desired range. Experimental studies with a real WTB are carried out, compared to the widely used proportional integral derivative (PID)-based control system for autonomous WTB inspection, the detection success rate is improved significantly.

Proposed System

Experimental Results

Project #1: Energy Saving Robot Control for Field Inspections

Summary

This paper presents a control strategy to improve the energy efficiency of a quadrotor for field inspections. A power consumption analytical model for a quadrotor is constructed, which indicates that the power consumption of a quadrotor is correlated with the roll and pitch angles. Based on that, a cascaded bounded control framework is developed to regulate the roll and pitch angles within the predefined energy efficient ranges, while a successful inspection trajectory tracking can be achieved simultaneously. Experimental studies are carried out to prove the effectiveness of the proposed method through a mock-up scenario of wind farm inspection. Compared to the conventional cascaded control framework, the proposed energy saving control strategy is capable of saving 5% energy for the same inspection assignment under wind disturbance.

Publication

Yafeng Wang, Yeqin Wang, Beibei Ren. Energy Saving Quadrotor Control for Field Inspections. IEEE Transactions on Systems, Man, and Cybernetics: Systems, 2021. DOI: 10.1109/TSMC.2020.3037071

Proposed Power Consumption Model

Experimental Results

Project #2: A Drive-through Recharging Strategy for a Flying Robot

Summary

This paper proposes a drive-through recharging strategy for a quadrotor. First, a ground charging station is constructed with a portable charging wire, then with two conductive hooks connected to the battery, the quadrotor is flying through the station. Finally, after connecting the hooks to the charging wire, the quadrotor can be recharged without landing or stopping, similar to a drive-through. During the charging, the quadrotor is still able to accomplish local monitoring assignments. The main challenge of this work is to ensure that the hooks successfully connect to the charging wire. Though visual-based techniques appear promising to handle this problem, the detection of a thin charging wire is challenging especially during the flight. Besides, the conductive hooks underneath the quadrotor are out of the camera view, which brings more challenges to the problem. Therefore, in this paper, the aiming problem is directed into the position constraint control problem of the quadrotor. Specifically, a virtual aiming box is considered near the charging wire center, then a control design is proposed to constrain the position of the quadrotor to ensure the hooks position always within the virtual aiming box. Moreover, to enhance the system's robustness against the outdoor environment, a wind disturbance estimator is proposed in the control design. Both theoretical analysis and experimental validation are carried out to demonstrate the effectiveness of the proposed strategy.

Publication

Wang, Yafeng, Qinbo Sun, Tristan Berger, and Weimin Qi. "A drive-through recharging strategy for a quadrotor." In 2021 IEEE International Conference on Robotics and Automation (ICRA)

Proposed System

Experimental Results

Project #3: Quadrotor-Enabled Autonomous Parking Occupancy Detection

Summary

Large special-events parking involves various parking scenarios, e.g., temporary parking and on-street parking. Their occupancy detection is challenging as it is unrealistic to construct gates/stations for temporary parking areas or build a sensor-based detection system to cover every single street. To address this issue, this study develops a quadrotor-enabled autonomous parking occupancy detection system. A camera-equipped quadrotor is flying over the parking lot first; then the images are captured by the on-board camera of the quadrotor and transferred to the ground station; finally, the ground station will process and release the occupancy information to the driver's mobile devices. The decision tree learning algorithm is adopted to determine the optimal flying speed for the quadrotor to balance the trade-off between the detection efficiency and accuracy. In order to tackle the complex environment in real-life parking, a convolutional neural network (CNN)-based vehicle detection model has been trained and implemented, where the realistic factors, e.g., passing pedestrians and tree blocking, are considered. Experiments are conducted to illustrate the effectiveness of the proposed system.

Publication

Yafeng Wang, Beibei Ren. Quadrotor-Enabled Autonomous Parking Occupancy Detection. In 2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), pp. 8287-8292.

Proposed System

Experimental Results

Project #4: Bounded UDE-Based Control for a SLAM Equipped Quadrotor with Input Constraints

Summary

Though the widely adopted re-localization technique can handle the pose lost problem of a ground robot or a vehicle carried simultaneous localization and mapping (SLAM) system, the high maneuverability of a quadrotor can still lead to the failure of the re-localization procedure. Therefore, this paper presents a bounded velocity control strategy, which can guarantee the velocities of a quadrotor within an appropriate range while tracking the desired trajectory. Particularly, a boundedness design is introduced into the barrier Lyapunov function (BLF)- based control framework to construct the bounded velocity controller. The effectiveness of the proposed control strategy is demonstrated through a quadrotor carried SLAM system. The proposed approach ensures the smooth and successful SLAM map building during the whole flight process while eliminating the need of the re-localization procedure. Furthermore, comparative experimental cases are investigated to demonstrate the advantages of the proposed approach over the commonly used control methods in terms of the SLAM system robustness.

Publication

Yafeng Wang, Beibei Ren. Bounded UDE-Based Control for a SLAM Equipped Quadrotor with Input Constraints. American Control Conference (ACC).

System structure

Experimental Results (comparison with traditional controllers)

Project #5 Design of Dual-spring Shock Absorption System for Outdoor AGV

Summary

Currently, the shock absorption system for outdoor AGV is mainly built with an identical-spring solution, in which all the damping springs have identical elastic coefficient. In this paper, we introduce a method to design the shock absorption system of the AGV using the dual-spring solution. Springs of two different elastic coefficients are used, and enhanced performance in obstacle-crossing capability can be achieved. The proposed dual-spring solution design method takes several critical outdoor working requirements as to design constraints and integrates damping system analysis to determine the optimal coefficients for the dual-spring system. To validate the effectiveness of this dual-spring design method, theoretical analysis is fully derived and an AGV chassis is physically built using a dual-spring solution and is subjected to a series of validation tests.

Publication

Yafeng Wang, Xiangyu Lei, Guilin Zhang, Shuaijun Li, Huihuan Qian, and Yangsheng Xu. "Design of dual-spring shock absorption system for outdoor agv." 2017 IEEE International Conference on Information and Automation (ICIA). IEEE, 2017.

Results