The styrene-butadiene-styrene（SBS） modified bitumens with different contents of SBS modifiers are stored in different conditions to study the storage stability of SBS modified bitumen.Mixed-level orthogonal array de...The styrene-butadiene-styrene（SBS） modified bitumens with different contents of SBS modifiers are stored in different conditions to study the storage stability of SBS modified bitumen.Mixed-level orthogonal array design（OAD） is used and factors such as SBS modifier content,storage time,storage temperature and container size are chosen in a mixed-level OAD with an OA16（31×44） matrix.Parameters like the separation softening point difference（the separation difference of the ring and ball softening point of the top and bottom samples） and the average softening point（the arithmetic mean of the softening points of the top and bottom samples） are proposed to evaluate the separation and the ageing of modified bitumen during storage in this experiment,respectively.The results reveal that the separation and the ageing during storage exhibit a complicated variation for storage temperature and time.The separation softening point difference decreases with the storage temperature rising from 20 to 120 ℃ and increases with the temperature exceeding 120 ℃,and the average softening point drops with the storage time being prolonged.Different storage conditions have various effects on the storage stability of SBS modified bitumen.展开更多
Accurate parameter identification is essential when designing controllers for inertially stabilized platforms （lSPs）. But traditional identification methods suffer from observation measurement noise and operating re...Accurate parameter identification is essential when designing controllers for inertially stabilized platforms （lSPs）. But traditional identification methods suffer from observation measurement noise and operating restrictions of ISPs. To address this issue, a novel identification method based on current command design and multilevel coordinate search （MCS） algorithm without any higher order measurement differentiations was proposed. The designed current commands were adopted to obtain parameter decoupled models with the platform operating under allowable conditions. MCS algorithm was employed to estimate the parameters based on parameter decoupled models. A comparison experiment between the proposed method and non-linear least square method was carried out and most of the relative errors of identified parameters obtained by the proposed method were below 10%. Simulation and experiment based on identified parameters were conducted. A velocity control structure was also developed with disturbance observer （DOB） for application in disturbance compensation control system of an ISR Experimental results show that the control scheme based on the identified parameters with DOB has the best disturbance rejection performance. It reduces the peak to peak value （PPV） of velocity error integral to 0.8 mrad which is much smaller than the value （10 mrad） obtained by the single velocity controller without DOB. Compared with the control scheme based on sweep model with DOB compensation, the proposed control scheme improves the PPV of velocity error integral by 1.625 times.展开更多
基金The National Natural Science Foundation of China (No.51178348)
文摘The styrene-butadiene-styrene（SBS） modified bitumens with different contents of SBS modifiers are stored in different conditions to study the storage stability of SBS modified bitumen.Mixed-level orthogonal array design（OAD） is used and factors such as SBS modifier content,storage time,storage temperature and container size are chosen in a mixed-level OAD with an OA16（31×44） matrix.Parameters like the separation softening point difference（the separation difference of the ring and ball softening point of the top and bottom samples） and the average softening point（the arithmetic mean of the softening points of the top and bottom samples） are proposed to evaluate the separation and the ageing of modified bitumen during storage in this experiment,respectively.The results reveal that the separation and the ageing during storage exhibit a complicated variation for storage temperature and time.The separation softening point difference decreases with the storage temperature rising from 20 to 120 ℃ and increases with the temperature exceeding 120 ℃,and the average softening point drops with the storage time being prolonged.Different storage conditions have various effects on the storage stability of SBS modified bitumen.
基金Project(50805144) supported by the National Natural Science Foundation of China
文摘Accurate parameter identification is essential when designing controllers for inertially stabilized platforms （lSPs）. But traditional identification methods suffer from observation measurement noise and operating restrictions of ISPs. To address this issue, a novel identification method based on current command design and multilevel coordinate search （MCS） algorithm without any higher order measurement differentiations was proposed. The designed current commands were adopted to obtain parameter decoupled models with the platform operating under allowable conditions. MCS algorithm was employed to estimate the parameters based on parameter decoupled models. A comparison experiment between the proposed method and non-linear least square method was carried out and most of the relative errors of identified parameters obtained by the proposed method were below 10%. Simulation and experiment based on identified parameters were conducted. A velocity control structure was also developed with disturbance observer （DOB） for application in disturbance compensation control system of an ISR Experimental results show that the control scheme based on the identified parameters with DOB has the best disturbance rejection performance. It reduces the peak to peak value （PPV） of velocity error integral to 0.8 mrad which is much smaller than the value （10 mrad） obtained by the single velocity controller without DOB. Compared with the control scheme based on sweep model with DOB compensation, the proposed control scheme improves the PPV of velocity error integral by 1.625 times.
