http://bjlgdxxbywb.xml-journal.net/ JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY blgywb@bit.edu.cn blgywb@bit.edu.cn en blgywb@bit.edu.cn 1004-057CN9 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20019?pageType=en Wang Jun, Liu Yanbin, Jin Yi, Zhang Youtong To speedily regulate and precisely control a hydraulic power system in a unmanned walking platform (UWP), based on the brief analysis of digital PID and its shortcomings, dual control parameters in a hydraulic power system are given for the precision requirement, and a control strategy for dual relative control parameters in the dual loop PID is put forward, a load and throttle rotation-speed response model for variable pump and gasoline engine is provided according to a physical process, a simplified neural network structure PID is introduced, and formed mixed neural network PID(MNN PID)to control rotation speed of engine and pressure of variable pump, calculation using the back propagation(BP) algorithm and a self-adapted learning step is made, including a mathematic principle and a calculation flow scheme, the BP algorithm of neural network PID is trained and the control effect of system is simulated in Matlab environment, real control effects of engine rotation speed and variable pump pressure are verified in the experimental bench. Results show that algorithm effect of MNN PID is stable and MNN PID can meet the adjusting requirement of control parameters. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 273-282. Wang Jun, Liu Yanbin, Jin Yi, Zhang Youtong To speedily regulate and precisely control a hydraulic power system in a unmanned walking platform (UWP), based on the brief analysis of digital PID and its shortcomings, dual control parameters in a hydraulic power system are given for the precision requirement, and a control strategy for dual relative control parameters in the dual loop PID is put forward, a load and throttle rotation-speed response model for variable pump and gasoline engine is provided according to a physical process, a simplified neural network structure PID is introduced, and formed mixed neural network PID(MNN PID)to control rotation speed of engine and pressure of variable pump, calculation using the back propagation(BP) algorithm and a self-adapted learning step is made, including a mathematic principle and a calculation flow scheme, the BP algorithm of neural network PID is trained and the control effect of system is simulated in Matlab environment, real control effects of engine rotation speed and variable pump pressure are verified in the experimental bench. Results show that algorithm effect of MNN PID is stable and MNN PID can meet the adjusting requirement of control parameters. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 273-282. Control of Hydraulic Power System by Mixed Neural Network PID in Unmanned Walking Platform Wang Jun, Liu Yanbin, Jin Yi, Zhang Youtong 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 273-282. article doi:10.15918/j.jbit1004-0579.20019 10.15918/j.jbit1004-0579.20019 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20019?pageType=en 273 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.19105?pageType=en Zheng Changsong, Chen Yichun, Jia Ran In the steering process of tracked vehicle with hydrostatic drive, the motion and resistance states of the vehicle are always of uncertain and nonlinear characteristics, and these states may undergoe large-scale changes. Therefore, it is significant to enhance the steering stability of tracked vehicle with hydrostatic drive to meet the need of future battlefield. In this paper, a sliding mode control algorithm is proposed and applied to achieve desired yaw rates. The speed controller and the yaw rate controller are designed through the kinematics and dynamics analysis. In addition, the nonlinear derivative and integral sliding mode control algorithm is designed, which is supposed to efficiently reduce the integration saturation and the disturbances from the unsmooth road surfaces through a conditional integrator approach. Moreover, it improves the response speed of the system and reduces the chattering by the derivative controller. The hydrostatic tracked vehicle module is modeled with a multi-body dynamic software RecurDyn and the steering control strategy module is modeled by MATLAB/Simulink. The co-simulation results of the whole model show that the control strategy can improve the vehicle steering response speed and also ensure a smooth control output with small chattering and strong robustness. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 283-293. Zheng Changsong, Chen Yichun, Jia Ran In the steering process of tracked vehicle with hydrostatic drive, the motion and resistance states of the vehicle are always of uncertain and nonlinear characteristics, and these states may undergoe large-scale changes. Therefore, it is significant to enhance the steering stability of tracked vehicle with hydrostatic drive to meet the need of future battlefield. In this paper, a sliding mode control algorithm is proposed and applied to achieve desired yaw rates. The speed controller and the yaw rate controller are designed through the kinematics and dynamics analysis. In addition, the nonlinear derivative and integral sliding mode control algorithm is designed, which is supposed to efficiently reduce the integration saturation and the disturbances from the unsmooth road surfaces through a conditional integrator approach. Moreover, it improves the response speed of the system and reduces the chattering by the derivative controller. The hydrostatic tracked vehicle module is modeled with a multi-body dynamic software RecurDyn and the steering control strategy module is modeled by MATLAB/Simulink. The co-simulation results of the whole model show that the control strategy can improve the vehicle steering response speed and also ensure a smooth control output with small chattering and strong robustness. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 283-293. Nonlinear Derivative and Integral Sliding Control for Tracked Vehicle Steering with Hydrostatic Drive Zheng Changsong, Chen Yichun, Jia Ran 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 283-293. article doi:10.15918/j.jbit1004-0579.19105 10.15918/j.jbit1004-0579.19105 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.19105?pageType=en 283 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.19121?pageType=en Wang Wei, Song Qiang, Li Yiting, Ahmad Mukhtiar The traditional measurement method was inaccurate to evaluate the motor controller efficiency, which the measurement efficiency value could be more than 100% in practical testing experiments. To deal with this issue, an improved electrical measurement method for the motor controller efficiency is proposed in this paper, which is established by analyzing the power loss distribution and phase currents of the motor controller. It is demonstrated that the SiC MOSFET chips are the main power loss devices in the motor controller, accounting for more than 93.1% of the total power loss. The accuracy of the proposed method is compared with the traditional method in simulation. It shows that the test error of the efficiency obtained by the traditional method fluctuates on a large scale, which varied from 0.094% to 1.911%. Compared with the traditional method, the test error of the proposed method appears to be less than 0.083%, which provides significant guidance for the motor controller efficiency test and design. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 294-302. Wang Wei, Song Qiang, Li Yiting, Ahmad Mukhtiar The traditional measurement method was inaccurate to evaluate the motor controller efficiency, which the measurement efficiency value could be more than 100% in practical testing experiments. To deal with this issue, an improved electrical measurement method for the motor controller efficiency is proposed in this paper, which is established by analyzing the power loss distribution and phase currents of the motor controller. It is demonstrated that the SiC MOSFET chips are the main power loss devices in the motor controller, accounting for more than 93.1% of the total power loss. The accuracy of the proposed method is compared with the traditional method in simulation. It shows that the test error of the efficiency obtained by the traditional method fluctuates on a large scale, which varied from 0.094% to 1.911%. Compared with the traditional method, the test error of the proposed method appears to be less than 0.083%, which provides significant guidance for the motor controller efficiency test and design. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 294-302. Improved Efficiency Test Method for the Motor Controller with SiC MOSFETs Wang Wei, Song Qiang, Li Yiting, Ahmad Mukhtiar 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 294-302. article doi:10.15918/j.jbit1004-0579.19121 10.15918/j.jbit1004-0579.19121 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.19121?pageType=en 294 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.19101?pageType=en Chen Shuping, Chen Huiyan, Negrut Dan In order to investigate how model fidelity in the formulation of model predictive control(MPC) algorithm affects the path tracking performance, a bicycle model and an 8 degrees of freedom(DOF) vehicle model, as well as a 14-DOF vehicle model were employed to implement the MPC-based path tracking controller considering the constraints of input limit and output admissibility by using a lower fidelity vehicle model to control a higher fidelity vehicle model. In the MPC controller, the nonlinear vehicle model was linearized and discretized for state prediction and vehicle heading angle, lateral position and longitudinal position were chosen as objectives in the cost function. The wheel step steering and sine wave steering responses between the developed vehicle models and the Carsim model were compared for validation before implementing the model predictive path tracking control. The simulation results of trajectory tracking considering an 8-shaped curved reference path were presented and compared when the prediction model and the plant were changed. The results show that the trajectory tracking errors are small and the tracking performances of the proposed controller considering different complexity vehicle models are good in the curved road environment. Additionally, the MPC-based controller formulated with a high-fidelity model performs better than that with a low-fidelity model in the trajectory tracking. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 303-316. Chen Shuping, Chen Huiyan, Negrut Dan In order to investigate how model fidelity in the formulation of model predictive control(MPC) algorithm affects the path tracking performance, a bicycle model and an 8 degrees of freedom(DOF) vehicle model, as well as a 14-DOF vehicle model were employed to implement the MPC-based path tracking controller considering the constraints of input limit and output admissibility by using a lower fidelity vehicle model to control a higher fidelity vehicle model. In the MPC controller, the nonlinear vehicle model was linearized and discretized for state prediction and vehicle heading angle, lateral position and longitudinal position were chosen as objectives in the cost function. The wheel step steering and sine wave steering responses between the developed vehicle models and the Carsim model were compared for validation before implementing the model predictive path tracking control. The simulation results of trajectory tracking considering an 8-shaped curved reference path were presented and compared when the prediction model and the plant were changed. The results show that the trajectory tracking errors are small and the tracking performances of the proposed controller considering different complexity vehicle models are good in the curved road environment. Additionally, the MPC-based controller formulated with a high-fidelity model performs better than that with a low-fidelity model in the trajectory tracking. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 303-316. Implementation of MPC-Based Trajectory Tracking Considering Different Fidelity Vehicle Models Chen Shuping, Chen Huiyan, Negrut Dan 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 303-316. article doi:10.15918/j.jbit1004-0579.19101 10.15918/j.jbit1004-0579.19101 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.19101?pageType=en 303 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20036?pageType=en Wu Hao, Zhang Fujun, Zhang Zhenyu Spray atomization of liquid fuel plays an important role in droplet evaporation, combustible mixture formation and subsequent combustion process. Well-atomized liquid spray contributes to high fuel efficiency and low pollutant emissions. Gasoline direct injection(GDI) has been recognized as one of the most effective ways to improve fuel atomization. As a special direct injection method, the air-assisted direct injection utilizes high-speed flow of high-pressure air at the injector exit to assist liquid fuel injection and promote spray atomization at a low injection pressure. This injection method has excellent application potential and advantages for high performance and lightweight engines. In this study, the hollow cone spray emerging from an air-assisted injector was studied in a constant volume chamber with the ambient pressures ranging from 5 kPa to 300 kPa. External macro characteristics of spray were obtained using high speed backlit imaging. Phase Doppler particle analyzer(PDPA) was utilized to study the microcosmic spray characteristics. The results show that under the flash boiling condition, the spray will generate a strong flash boiling point which causes the cone shape spray to expand both inwards and outwards. The axisymmetric inward expansion would converge together and form a lathy aggregation area below the nozzle and the axisymmetric outward expansion greatly increases the spray width. The sauter mean diameter (SMD) of flash boiling condition can be reduced to 5 μm compared to the level close to 10 μm in the non-flash boiling condition. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 317-325. Wu Hao, Zhang Fujun, Zhang Zhenyu Spray atomization of liquid fuel plays an important role in droplet evaporation, combustible mixture formation and subsequent combustion process. Well-atomized liquid spray contributes to high fuel efficiency and low pollutant emissions. Gasoline direct injection(GDI) has been recognized as one of the most effective ways to improve fuel atomization. As a special direct injection method, the air-assisted direct injection utilizes high-speed flow of high-pressure air at the injector exit to assist liquid fuel injection and promote spray atomization at a low injection pressure. This injection method has excellent application potential and advantages for high performance and lightweight engines. In this study, the hollow cone spray emerging from an air-assisted injector was studied in a constant volume chamber with the ambient pressures ranging from 5 kPa to 300 kPa. External macro characteristics of spray were obtained using high speed backlit imaging. Phase Doppler particle analyzer(PDPA) was utilized to study the microcosmic spray characteristics. The results show that under the flash boiling condition, the spray will generate a strong flash boiling point which causes the cone shape spray to expand both inwards and outwards. The axisymmetric inward expansion would converge together and form a lathy aggregation area below the nozzle and the axisymmetric outward expansion greatly increases the spray width. The sauter mean diameter (SMD) of flash boiling condition can be reduced to 5 μm compared to the level close to 10 μm in the non-flash boiling condition. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 317-325. Spray Characteristics of Air-Assisted Injector Under Different Ambient Pressures Wu Hao, Zhang Fujun, Zhang Zhenyu 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 317-325. article doi:10.15918/j.jbit1004-0579.20036 10.15918/j.jbit1004-0579.20036 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20036?pageType=en 317 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20029?pageType=en Zhu Ye, Wang Xulong, Chen Xiangyu A comprehensive performance evaluation method for the tunnel boring machine(TBM) cutterhead is proposed in this paper. The evaluation system is established on strength and vibration. Based on fracture mechanics theory, fatigue strength evaluation indices are determined under critical crack length. The concept of crack regions division is proposed to evaluate fatigue strength more accurately and specifically. In addition, the velocities in three directions of critical locations are obtained with dynamics equations. Then, the root-mean-square values of velocities are taken as the vibration severity indices. Taking the cutterhead of Jilin diversion engineering as an example, the evaluations of each index are completed; then, the vibration of the TBM cutterhead is measured and compared with the theoretical calculation results. There are similar change laws between the theoretical calculation results and the testing results of the cutterhead acceleration, which proves that the method of calculation of the vibration index is effective, the reliability of the cutter saddle welding should be paid attention to when the TBM is working, and the condition of vibration severity of the TBM cutterhead meets the requirements but needs to be improved. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 326-338. Zhu Ye, Wang Xulong, Chen Xiangyu A comprehensive performance evaluation method for the tunnel boring machine(TBM) cutterhead is proposed in this paper. The evaluation system is established on strength and vibration. Based on fracture mechanics theory, fatigue strength evaluation indices are determined under critical crack length. The concept of crack regions division is proposed to evaluate fatigue strength more accurately and specifically. In addition, the velocities in three directions of critical locations are obtained with dynamics equations. Then, the root-mean-square values of velocities are taken as the vibration severity indices. Taking the cutterhead of Jilin diversion engineering as an example, the evaluations of each index are completed; then, the vibration of the TBM cutterhead is measured and compared with the theoretical calculation results. There are similar change laws between the theoretical calculation results and the testing results of the cutterhead acceleration, which proves that the method of calculation of the vibration index is effective, the reliability of the cutter saddle welding should be paid attention to when the TBM is working, and the condition of vibration severity of the TBM cutterhead meets the requirements but needs to be improved. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 326-338. Evaluation of TBM Cutterhead’s Comprehensive Performance Under Complicated Conditions Zhu Ye, Wang Xulong, Chen Xiangyu 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 326-338. article doi:10.15918/j.jbit1004-0579.20029 10.15918/j.jbit1004-0579.20029 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20029?pageType=en 326 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20024?pageType=en Sun Xin, Yang Yuan, Song Zhengyu An improved delay priority resource scheduling algorithm with low packet loss rate for multimedia broadcast multicast service (MBMS) in long term evolution (LTE) systems is proposed in this paper. Real-time services in LTE systems require lower delay and packet loss rate. However, it is difficult to meet the QoS requirements of real-time services using the current MBMS resource scheduling algorithm. The proposed algorithm in this paper jointly considers user delay information and real-time channel conditions. By introducing the user delay information, the lower delay and fairness of users are guaranteed. Meanwhile, by considering the channel conditions of users, the packet loss rate can be effectively reduced, improving the system throughput. Simulation results show that under the premise of ensuring the delay requirements of real-time services, the proposed algorithm achieves a lower packet loss rate compared to other existing algorithms. Furthermore, it can achieve a good balance between system throughput and user fairness. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 339-344. Sun Xin, Yang Yuan, Song Zhengyu An improved delay priority resource scheduling algorithm with low packet loss rate for multimedia broadcast multicast service (MBMS) in long term evolution (LTE) systems is proposed in this paper. Real-time services in LTE systems require lower delay and packet loss rate. However, it is difficult to meet the QoS requirements of real-time services using the current MBMS resource scheduling algorithm. The proposed algorithm in this paper jointly considers user delay information and real-time channel conditions. By introducing the user delay information, the lower delay and fairness of users are guaranteed. Meanwhile, by considering the channel conditions of users, the packet loss rate can be effectively reduced, improving the system throughput. Simulation results show that under the premise of ensuring the delay requirements of real-time services, the proposed algorithm achieves a lower packet loss rate compared to other existing algorithms. Furthermore, it can achieve a good balance between system throughput and user fairness. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 339-344. Improved Delay Priority Resource Scheduling with Low Packet Loss Rate for MBMS in LTE Systems Sun Xin, Yang Yuan, Song Zhengyu 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 339-344. article doi:10.15918/j.jbit1004-0579.20024 10.15918/j.jbit1004-0579.20024 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20024?pageType=en 339 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20022?pageType=en Shi Wenling, Du Huiqian, Mei Wenbo A novel channel attention residual network (CAN) for SISR has been proposed to rescale pixel-wise features by explicitly modeling interdependencies between channels and encoding where the visual attention is located. The backbone of CAN is channel attention block (CAB). The proposed CAB combines cosine similarity block (CSB) and back-projection gating block (BG). CSB fully considers global spatial information of each channel and computes the cosine similarity between each channel to obtain finer channel statistics than the first-order statistics. For further exploration of channel attention, we introduce effective back-projection to the gating mechanism and propose BG. Meanwhile, we adopt local and global residual connections in SISR which directly convey most low-frequency information to the final SR outputs and valuable high-frequency components are allocated more computational resources through channel attention mechanism. Extensive experiments show the superiority of the proposed CAN over the state-of-the-art methods on benchmark datasets in both accuracy and visual quality. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 345-353. Shi Wenling, Du Huiqian, Mei Wenbo A novel channel attention residual network (CAN) for SISR has been proposed to rescale pixel-wise features by explicitly modeling interdependencies between channels and encoding where the visual attention is located. The backbone of CAN is channel attention block (CAB). The proposed CAB combines cosine similarity block (CSB) and back-projection gating block (BG). CSB fully considers global spatial information of each channel and computes the cosine similarity between each channel to obtain finer channel statistics than the first-order statistics. For further exploration of channel attention, we introduce effective back-projection to the gating mechanism and propose BG. Meanwhile, we adopt local and global residual connections in SISR which directly convey most low-frequency information to the final SR outputs and valuable high-frequency components are allocated more computational resources through channel attention mechanism. Extensive experiments show the superiority of the proposed CAN over the state-of-the-art methods on benchmark datasets in both accuracy and visual quality. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 345-353. Novel Channel Attention Residual Network for Single Image Super-Resolution Shi Wenling, Du Huiqian, Mei Wenbo 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 345-353. article doi:10.15918/j.jbit1004-0579.20022 10.15918/j.jbit1004-0579.20022 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20022?pageType=en 345 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20035?pageType=en Zheng Yuqiao, Jin Honghong, Zhang Chengcheng A method for hub assembly sequence planning oriented to the fixed position layout is proposed. An assembly relationship model was constructed to describe the relationship between hub assembly components and workstations, considering the layout of the hub assembly line and process constraints, including the assembly precedence matrix, workstation assembly capability table and criticality table of components. The evaluation mechanism for the assembly sequence was established. Values from the evaluation functions with engineering significance were used to select the optimal assembly sequence from the perspective of assembly time, assembly index and assembly path distance. In function, the criticality of components was introduced into the traditional assemblability index, comparing the multi-objective dragonfly algorithm (MODA) with non-dominated sorting genetic algorithm-Ⅱ (NSGA-Ⅱ) to complete the assembly sequence planning and assignment for workstations. The optimized results show that the presented method is feasible and efficient for solving the hub assembly sequence planning problem. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 354-365. Zheng Yuqiao, Jin Honghong, Zhang Chengcheng A method for hub assembly sequence planning oriented to the fixed position layout is proposed. An assembly relationship model was constructed to describe the relationship between hub assembly components and workstations, considering the layout of the hub assembly line and process constraints, including the assembly precedence matrix, workstation assembly capability table and criticality table of components. The evaluation mechanism for the assembly sequence was established. Values from the evaluation functions with engineering significance were used to select the optimal assembly sequence from the perspective of assembly time, assembly index and assembly path distance. In function, the criticality of components was introduced into the traditional assemblability index, comparing the multi-objective dragonfly algorithm (MODA) with non-dominated sorting genetic algorithm-Ⅱ (NSGA-Ⅱ) to complete the assembly sequence planning and assignment for workstations. The optimized results show that the presented method is feasible and efficient for solving the hub assembly sequence planning problem. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 354-365. Optimization of Wind Turbine Hub Assembly Sequence Based on Intelligent Algorithm Zheng Yuqiao, Jin Honghong, Zhang Chengcheng 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 354-365. article doi:10.15918/j.jbit1004-0579.20035 10.15918/j.jbit1004-0579.20035 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20035?pageType=en 354 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20042?pageType=en Ni Xiangdong, Bao Mingxi With a transmission system suitable for a medium or large self-propelled cotton picker as the object of the study, the following work focuses on the influence law of an independently designed hydro-mechanical continuously variable transmission(HMCVT) in the process of changing sections. An HMCVT simulation model was established using the multibody dynamics Simulation X software. The accuracy of the simulation model was verified by comparing the numerical values of the output speed of the HMCVT with model predictions. The HMCVT test bench was built independently using a John Deere 4045HYC11 diesel engine as power input. The engine speed, load torque, oil pressure, and flow of speed regulating valve were considered the influencing factors. The sliding friction power was the response index for the segment change process test. We analysed the reasons for the decrease in output speed during the shifting process, and proposed to effectively reduce the stable speed difference before and after the output shaft shifting by shifting the stage ahead (with displacement ratio of –0.96). This study provides a reference value for the smoothness of the HMCVT of the self-propelled cotton picker, and is relevant in promoting the use of the cotton picker. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 366-378. Ni Xiangdong, Bao Mingxi With a transmission system suitable for a medium or large self-propelled cotton picker as the object of the study, the following work focuses on the influence law of an independently designed hydro-mechanical continuously variable transmission(HMCVT) in the process of changing sections. An HMCVT simulation model was established using the multibody dynamics Simulation X software. The accuracy of the simulation model was verified by comparing the numerical values of the output speed of the HMCVT with model predictions. The HMCVT test bench was built independently using a John Deere 4045HYC11 diesel engine as power input. The engine speed, load torque, oil pressure, and flow of speed regulating valve were considered the influencing factors. The sliding friction power was the response index for the segment change process test. We analysed the reasons for the decrease in output speed during the shifting process, and proposed to effectively reduce the stable speed difference before and after the output shaft shifting by shifting the stage ahead (with displacement ratio of –0.96). This study provides a reference value for the smoothness of the HMCVT of the self-propelled cotton picker, and is relevant in promoting the use of the cotton picker. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 366-378. Dynamic Test of Hydro Mechanical Composite Transmission for Cotton Picker Ni Xiangdong, Bao Mingxi 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 366-378. article doi:10.15918/j.jbit1004-0579.20042 10.15918/j.jbit1004-0579.20042 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20042?pageType=en 366 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20049?pageType=en Fang Rui, Li Xiangnan, Wu Haixia, Gao Wei, Ren Shiwei The concept of difference and sum co-array(DSCA) has become a new design idea for planar sparse arrays. Inspired by the shifting invariance property of DSCA, a specific configuration named here as the improved L-shaped array is proposed. Compared to other traditional 2D sparse array configurations such as 2D nested arrays and hourglass arrays, the proposed configuration has larger central consecutive ranges in its DSCA, thus increasing the DOF. At the same time, the mutual coupling effect is also reduced due to the enlarged spacing between the adjacent sensors. Simulations further demonstrate the superiority of the proposed arrays in terms of detection performance and estimation accuracy. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 379-385. Fang Rui, Li Xiangnan, Wu Haixia, Gao Wei, Ren Shiwei The concept of difference and sum co-array(DSCA) has become a new design idea for planar sparse arrays. Inspired by the shifting invariance property of DSCA, a specific configuration named here as the improved L-shaped array is proposed. Compared to other traditional 2D sparse array configurations such as 2D nested arrays and hourglass arrays, the proposed configuration has larger central consecutive ranges in its DSCA, thus increasing the DOF. At the same time, the mutual coupling effect is also reduced due to the enlarged spacing between the adjacent sensors. Simulations further demonstrate the superiority of the proposed arrays in terms of detection performance and estimation accuracy. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 379-385. Optimal Design of Improved L-shaped Coprime Array Based on Difference and Sum Co-array Fang Rui, Li Xiangnan, Wu Haixia, Gao Wei, Ren Shiwei 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 379-385. article doi:10.15918/j.jbit1004-0579.20049 10.15918/j.jbit1004-0579.20049 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20049?pageType=en 379 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20008?pageType=en You Mingyue, Ma Zhifeng The soft cancellation decoding of polar codes achieves a better performance than the belief propagation decoding with lower computational time and space complexities. However, because the soft cancellation decoding is based on the successive cancellation decoding, the decoding efficiency and performance with finite-length blocks can be further improved. Exploiting the idea of the successive cancellation list decoding, the soft cancellation decoding can be improved in two aspects: one is by adding branch decoding to the error-prone information bits to increase the accuracy of the soft information, and the other is through using partial iterative decoding to reduce the time and computational complexities. Compared with the original method, the improved soft cancellation decoding makes progress in the error correction performance, increasing the decoding efficiency and reducing the computational complexity, at the cost of a small increase of space complexity. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 386-392. You Mingyue, Ma Zhifeng The soft cancellation decoding of polar codes achieves a better performance than the belief propagation decoding with lower computational time and space complexities. However, because the soft cancellation decoding is based on the successive cancellation decoding, the decoding efficiency and performance with finite-length blocks can be further improved. Exploiting the idea of the successive cancellation list decoding, the soft cancellation decoding can be improved in two aspects: one is by adding branch decoding to the error-prone information bits to increase the accuracy of the soft information, and the other is through using partial iterative decoding to reduce the time and computational complexities. Compared with the original method, the improved soft cancellation decoding makes progress in the error correction performance, increasing the decoding efficiency and reducing the computational complexity, at the cost of a small increase of space complexity. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 386-392. Improved Soft Cancellation Decoding of Polar Codes You Mingyue, Ma Zhifeng 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 386-392. article doi:10.15918/j.jbit1004-0579.20008 10.15918/j.jbit1004-0579.20008 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20008?pageType=en 386 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.19125?pageType=en Huang Guiping, Zhu Wenfang, Wang Weifeng, Xie Xiaoliang, Wang Hewei According to the operational conditions of an aviation module reticule, a measurement mode is proposed, which is based on an industrial photogrammetry system, with matching by a measuring pen. Meanwhile, the factors affecting the accuracy of the measurement have been analyzed and verified by examples. The analysis is described as follows: ① Along the optical axis of the camera, the error is larger than the ones in other directions using the “single camera + measuring pen” mode; ② By avoiding the error along the optical axis of the camera, the accuracy of the “single camera + measuring pen” mode is better than 0.1 mm when the measuring pen is moving parallel to the optical axis. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 393-398. Huang Guiping, Zhu Wenfang, Wang Weifeng, Xie Xiaoliang, Wang Hewei According to the operational conditions of an aviation module reticule, a measurement mode is proposed, which is based on an industrial photogrammetry system, with matching by a measuring pen. Meanwhile, the factors affecting the accuracy of the measurement have been analyzed and verified by examples. The analysis is described as follows: ① Along the optical axis of the camera, the error is larger than the ones in other directions using the “single camera + measuring pen” mode; ② By avoiding the error along the optical axis of the camera, the accuracy of the “single camera + measuring pen” mode is better than 0.1 mm when the measuring pen is moving parallel to the optical axis. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 393-398. Test and Evaluation of Aviation Die Tyre Accuracy Based on Industrial Photogrammetry Huang Guiping, Zhu Wenfang, Wang Weifeng, Xie Xiaoliang, Wang Hewei 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 393-398. article doi:10.15918/j.jbit1004-0579.19125 10.15918/j.jbit1004-0579.19125 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.19125?pageType=en 393 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20031?pageType=en Zhuang Weimin, Wang Pengyue, Liu Yang, Xie Dongxuan, Shi Hongda The effects of forming damage are analyzed, which occur during hot stamping process, on the load-carrying capacity and failure mode of hot stamped beams. A damage-coupled pre-forming constitutive model was proposed, in which the damage during hot stamping process was introduced into the service response. The constitutive model was applied into the three-point bending simulation of a hot stamped beam, and then the influences of forming damage on the load-carrying capacity and cracks propagation were investigated. The results show that the forming damage reduces the maximum load capacity of the hot stamped beam by 7.5%. It also causes the crack to occur earlier and promotes crack to propagate along the radial direction of the punch. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 399-409. Zhuang Weimin, Wang Pengyue, Liu Yang, Xie Dongxuan, Shi Hongda The effects of forming damage are analyzed, which occur during hot stamping process, on the load-carrying capacity and failure mode of hot stamped beams. A damage-coupled pre-forming constitutive model was proposed, in which the damage during hot stamping process was introduced into the service response. The constitutive model was applied into the three-point bending simulation of a hot stamped beam, and then the influences of forming damage on the load-carrying capacity and cracks propagation were investigated. The results show that the forming damage reduces the maximum load capacity of the hot stamped beam by 7.5%. It also causes the crack to occur earlier and promotes crack to propagate along the radial direction of the punch. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 399-409. Modelling and Simulation on the Effect of Hot Forming Damage on Three-Point Bending Performance of Beam Components Zhuang Weimin, Wang Pengyue, Liu Yang, Xie Dongxuan, Shi Hongda 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 399-409. article doi:10.15918/j.jbit1004-0579.20031 10.15918/j.jbit1004-0579.20031 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20031?pageType=en 399 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.19108?pageType=en Wang Sufei, Zhang Fujun Exhaust resonance effect on the 2-stroke engine aspiration is investigated via one-dimensional simulation on GT-Power. Result shows that exhaust resonance is established when the number of oscillation periods per engine cycle derived from the engine speed and exhaust length is an integer. Exhaust resonance may raise or lower the trapping ratio, and the specific effect depends on the value of the number of oscillation periods per engine cycle. There is a liner regression relationship between the trapping ratio and average after back pressure. The primary way to improve the trapping ratio with the exhaust resonance is to increase the average after back pressure. The optimum exhaust resonance state is the one that suits the port timings so that the peak of exhaust pressure lies within the after charging period, raising the average after back pressure. For the case where the exhaust duration is 184°CA and the scavenge duration is 111°CA, the optimum number of oscillation periods per engine cycle is 3. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 410-416. Wang Sufei, Zhang Fujun Exhaust resonance effect on the 2-stroke engine aspiration is investigated via one-dimensional simulation on GT-Power. Result shows that exhaust resonance is established when the number of oscillation periods per engine cycle derived from the engine speed and exhaust length is an integer. Exhaust resonance may raise or lower the trapping ratio, and the specific effect depends on the value of the number of oscillation periods per engine cycle. There is a liner regression relationship between the trapping ratio and average after back pressure. The primary way to improve the trapping ratio with the exhaust resonance is to increase the average after back pressure. The optimum exhaust resonance state is the one that suits the port timings so that the peak of exhaust pressure lies within the after charging period, raising the average after back pressure. For the case where the exhaust duration is 184°CA and the scavenge duration is 111°CA, the optimum number of oscillation periods per engine cycle is 3. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 410-416. Simulation Research on the Effect of 2-Stroke Engine Exhaust Resonance on Aspiration Wang Sufei, Zhang Fujun 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 410-416. article doi:10.15918/j.jbit1004-0579.19108 10.15918/j.jbit1004-0579.19108 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.19108?pageType=en 410 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20050?pageType=en Zheng Yuqiao, Zhang Lu, Dong Fugang, Dong Bo A multi-objective optimization process for wind turbine steel towers is described in present work. The objective functions are tower top deformation and mass. The tower's height, radius and thickness are considered as design variables. The mathematical relationships between objective functions and variables were predicted by adopting a response surface methodology (RSM). Furthermore, the multi-objective non-dominated sorting genetic algorithm-II (NSGA-II) is adopted to optimize the tower structure to achieve accurate results with the minimum top deformation and total mass. A case study on a 2MW wind turbine tower optimization is given, which computes the desired tower structure parameters. The results are compared with the original tower: a reduction of tower top deformation reduction by about 16.5% and a reduction of a mass by about 1.5% could be achieved for such an optimization process. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 417-424. Zheng Yuqiao, Zhang Lu, Dong Fugang, Dong Bo A multi-objective optimization process for wind turbine steel towers is described in present work. The objective functions are tower top deformation and mass. The tower's height, radius and thickness are considered as design variables. The mathematical relationships between objective functions and variables were predicted by adopting a response surface methodology (RSM). Furthermore, the multi-objective non-dominated sorting genetic algorithm-II (NSGA-II) is adopted to optimize the tower structure to achieve accurate results with the minimum top deformation and total mass. A case study on a 2MW wind turbine tower optimization is given, which computes the desired tower structure parameters. The results are compared with the original tower: a reduction of tower top deformation reduction by about 16.5% and a reduction of a mass by about 1.5% could be achieved for such an optimization process. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 417-424. Multi-Objective Structural Optimization of Wind Turbine Tower Using Nondominated Sorting Genetic Algorithm Zheng Yuqiao, Zhang Lu, Dong Fugang, Dong Bo 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 417-424. article doi:10.15918/j.jbit1004-0579.20050 10.15918/j.jbit1004-0579.20050 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20050?pageType=en 417 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20053?pageType=en Wu Jun, Xu Haitao, Song Fengcheng, Xu Jun, Li Yanling, Wang Tao A 3D temperature field reconstruction method using the colored background oriented schlieren (CBOS) method is proposed to address image blurring due to the different refractive index of the multi-wavelength light and significant errors produced when the traditional background oriented schlieren (BOS) method is applied to high-temperature gas. First, the traditional method is employed to reconstruct the non-uniform 3D temperature field. Second, the CBOS method is applied to correct the distortion. Then, by analyzing the correlation coefficient among different color points of the colored background pattern, the non-uniform temperature field is reconstructed much more accurately. Finally, the experimental results are verified by applying the Runge-Kutta ray-tracing method and the thermocouple contact measurement method. The maximum average temperature error of the CBOS-reconstructed temperature field is 12.92°C, compared with the thermocouples. Therefore, an accurate three-dimensional reconstruction of the temperature field can be achieved by the proposed method effectively. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 425-434. Wu Jun, Xu Haitao, Song Fengcheng, Xu Jun, Li Yanling, Wang Tao A 3D temperature field reconstruction method using the colored background oriented schlieren (CBOS) method is proposed to address image blurring due to the different refractive index of the multi-wavelength light and significant errors produced when the traditional background oriented schlieren (BOS) method is applied to high-temperature gas. First, the traditional method is employed to reconstruct the non-uniform 3D temperature field. Second, the CBOS method is applied to correct the distortion. Then, by analyzing the correlation coefficient among different color points of the colored background pattern, the non-uniform temperature field is reconstructed much more accurately. Finally, the experimental results are verified by applying the Runge-Kutta ray-tracing method and the thermocouple contact measurement method. The maximum average temperature error of the CBOS-reconstructed temperature field is 12.92°C, compared with the thermocouples. Therefore, an accurate three-dimensional reconstruction of the temperature field can be achieved by the proposed method effectively. JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 425-434. Temperature Field Reconstruction in High-Temperature Gas by Using the Colored Background Oriented Schlieren Method Wu Jun, Xu Haitao, Song Fengcheng, Xu Jun, Li Yanling, Wang Tao 2020-12-29 Personal use only, all commercial or other reuse prohibited JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY. 2020 29(3): 425-434. article doi:10.15918/j.jbit1004-0579.20053 10.15918/j.jbit1004-0579.20053 JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY 29 3 2020-12-29 http://bjlgdxxbywb.xml-journal.net/article/doi/10.15918/j.jbit1004-0579.20053?pageType=en 425

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