This paper presents a method to characterize asphalt pavement macrotexture using the gray-tone difference matrix （GTDM）and discusses the potentials of the GTDM indicators for skid resistance evaluation.There are 37 ...This paper presents a method to characterize asphalt pavement macrotexture using the gray-tone difference matrix （GTDM）and discusses the potentials of the GTDM indicators for skid resistance evaluation.There are 37 field sites included in the data collection,which cover 6 types of asphalt pavement surfaces. The mean profile depth derived from 3-D macrotexture measurements （MPD3 ） has a significant relationship with the mean texture depth （MTD ）,which can be described by a logarithm model with R2 of 0.962.There is no significant linear relationship between the friction coefficient at a speed of 60 km/h （DFT60 ）and macrotexture indicators.A nonlinear model with British pendulum number （BPN ） incorporated can relate DFT60 to MTD or indicator fcon .A comparison with MTD shows that GTDM-based fcon has a potential to be a macrotexture indicator for skid resistance evaluation,which describes the general height difference and the average local height difference of pavement macrotexture. A relatively high fcon is helpful for improving asphalt pavement skid resistance.展开更多
Unique correct correspondence cannot be obtained only by use of gray correlation technique, which describes gray similar degree of feature points between the left and right images too unilaterally. The gray correlatio...Unique correct correspondence cannot be obtained only by use of gray correlation technique, which describes gray similar degree of feature points between the left and right images too unilaterally. The gray correlation technique is adopted to extract gray correlation peaks as a coarse matching set called multi-peak set. The disparity gradient limited constraint is utilized to optimize the multi-peak set. Unique match will be obtained by calculating the correlation of hybrid matrices consisting of reference differences and disparities from the multi-peak set. Two of the known corresponding points in the left and right images, respectively, are set as a pair of reference points to determine search direction and search scope at first. After the unique correspondence is obtained by calculating the correlation of the hybrid matrices from the multi-peak set, the obtained match is regarded as a new reference point till all feature points in the left (or right) image have been processed. Experimental results proved that the proposed algorithm was feasible and accurate.展开更多
In order to improve the frequency response and anti-interference characteristics of the smart electromechanical actuator(EMA)system,and aiming at the force fighting problem when multiple actuators work synchronously,a...In order to improve the frequency response and anti-interference characteristics of the smart electromechanical actuator(EMA)system,and aiming at the force fighting problem when multiple actuators work synchronously,a multi input multi output(MIMO)position difference cross coupling control coordinated strategy based on double‑closed-loop load feedforward control is proposed and designed.In this strategy,the singular value method of return difference matrix is used to design the parameter range that meets the requirements of system stability margin,and the sensitivity function and the H_(∞)norm theory are used to design and determine the optimal solution in the obtained parameter stability region,so that the multi actuator system has excellent synchronization,stability and anti-interference.At the same time,the mathematical model of the integrated smart EMA system is established.According to the requirements of point-to-point control,the controller of double-loop control and load feedforward compensation is determined and designed to improve the frequency response and anti-interference ability of single actuator.Finally,the 270 V high-voltage smart EMA system experimental platform is built,and the frequency response,load feedforward compensation and coordinated control experiments are carried out to verify the correctness of the position difference cross coupling control strategy and the rationality of the parameter design,so that the system can reach the servo control indexes of bandwidth 6 Hz,the maximum output force 20000 N and the synchronization error≤0.1 mm,which effectively solves the problem of force fighting.展开更多
基金The National Natural Science Foundation of China(No.50908004,51178013)
文摘This paper presents a method to characterize asphalt pavement macrotexture using the gray-tone difference matrix （GTDM）and discusses the potentials of the GTDM indicators for skid resistance evaluation.There are 37 field sites included in the data collection,which cover 6 types of asphalt pavement surfaces. The mean profile depth derived from 3-D macrotexture measurements （MPD3 ） has a significant relationship with the mean texture depth （MTD ）,which can be described by a logarithm model with R2 of 0.962.There is no significant linear relationship between the friction coefficient at a speed of 60 km/h （DFT60 ）and macrotexture indicators.A nonlinear model with British pendulum number （BPN ） incorporated can relate DFT60 to MTD or indicator fcon .A comparison with MTD shows that GTDM-based fcon has a potential to be a macrotexture indicator for skid resistance evaluation,which describes the general height difference and the average local height difference of pavement macrotexture. A relatively high fcon is helpful for improving asphalt pavement skid resistance.
文摘Unique correct correspondence cannot be obtained only by use of gray correlation technique, which describes gray similar degree of feature points between the left and right images too unilaterally. The gray correlation technique is adopted to extract gray correlation peaks as a coarse matching set called multi-peak set. The disparity gradient limited constraint is utilized to optimize the multi-peak set. Unique match will be obtained by calculating the correlation of hybrid matrices consisting of reference differences and disparities from the multi-peak set. Two of the known corresponding points in the left and right images, respectively, are set as a pair of reference points to determine search direction and search scope at first. After the unique correspondence is obtained by calculating the correlation of the hybrid matrices from the multi-peak set, the obtained match is regarded as a new reference point till all feature points in the left (or right) image have been processed. Experimental results proved that the proposed algorithm was feasible and accurate.
基金supported by the National Natural Science Foundation of China(No.52077100)the Aviation Science Foundation(No.201958052001)
文摘In order to improve the frequency response and anti-interference characteristics of the smart electromechanical actuator(EMA)system,and aiming at the force fighting problem when multiple actuators work synchronously,a multi input multi output(MIMO)position difference cross coupling control coordinated strategy based on double‑closed-loop load feedforward control is proposed and designed.In this strategy,the singular value method of return difference matrix is used to design the parameter range that meets the requirements of system stability margin,and the sensitivity function and the H_(∞)norm theory are used to design and determine the optimal solution in the obtained parameter stability region,so that the multi actuator system has excellent synchronization,stability and anti-interference.At the same time,the mathematical model of the integrated smart EMA system is established.According to the requirements of point-to-point control,the controller of double-loop control and load feedforward compensation is determined and designed to improve the frequency response and anti-interference ability of single actuator.Finally,the 270 V high-voltage smart EMA system experimental platform is built,and the frequency response,load feedforward compensation and coordinated control experiments are carried out to verify the correctness of the position difference cross coupling control strategy and the rationality of the parameter design,so that the system can reach the servo control indexes of bandwidth 6 Hz,the maximum output force 20000 N and the synchronization error≤0.1 mm,which effectively solves the problem of force fighting.
