Nowadays, a highly integrated valve?controlled cylinder(HIVC) is applied to drive the joints of legged robots. Although the adoption of HIVC has resulted in high?performance robot control, the hydraulic force system s...Nowadays, a highly integrated valve?controlled cylinder(HIVC) is applied to drive the joints of legged robots. Although the adoption of HIVC has resulted in high?performance robot control, the hydraulic force system still has problems, such as strong nonlinearity, and time?varying parameters. This makes HIVC force control very diffcult and complex. How to improve the control performance of the HIVC force control system and find the influence rule of the system parameters on the control performance is very significant. Firstly, the mathematical model of HIVC force control system is established. Then the mathematical expression for parameter sensitivity matrix is obtained by applying matrix sensitivity analysis(PSM). Then, aimed at the sinusoidal response under(three factors and three levels) working conditions, the simulation and the experiment are conducted. While the error between the simulation and experiment can't be avoided. Therefore, combined with the range analysis, the error in the two performance indexes of sinusoidal response under the whole working condition is analyzed. Besides, the sensitivity variation pattern for each system parameter under the whole working condition is figured out. Then the two sensitivity indexes for the three system parameters, which are supply pressure, proportional gain and initial displacement of piston, are proved experimentally. The proposed method significantly reveals the sensitivity characteristics of HIVC force control system, which can make the contribution to improve the control performance.展开更多
Rectangular cross-section specimens with different section thicknesses were prepared to study the infl uences of pouring temperature, mould temperature and squeeze velocity on the fl uidity of squeeze cast AZ91D magne...Rectangular cross-section specimens with different section thicknesses were prepared to study the infl uences of pouring temperature, mould temperature and squeeze velocity on the fl uidity of squeeze cast AZ91D magnesium alloy by means of orthogonal test design method. The results show that pouring temperature, mould temperature and squeeze velocity can significantly affect the fluidity of magnesium alloy specimens with wall thickness no more than 4 mm, and the pouring temperature is the most infl uential factor on the fl uidity of specimens with wall thickness of 1, 2 and 3 mm, while mould temperature is the one for specimens with wall thickness of 4 mm. Increasing pouring temperature between 700 °C and 750 °C is benefi cial to the fl uidity of AZ91D magnesium alloy, and increasing mould temperature signifi cantly enhances the fi lling ability of thick(3 and 4 mm) section castings. The fl uidity of squeeze cast magnesium alloy increases with the increase of wall thickness. It is not recommended to produce magnesium alloy casting with wall thickness of smaller than 3 mm by squeeze cast process due to the poor fl uidity. The software DPS was used to generate the regression model, and linear regression equations of the fl uidity of squeeze cast AZ91D with different wall thicknesses are obtained using the test results.展开更多
Chinese herbal flavonoids play a role in improving the health of aquatic animals and optimizing the quality of aquatic products.The efficient extraction of flavonoids is beneficial to deepening the application of flav...Chinese herbal flavonoids play a role in improving the health of aquatic animals and optimizing the quality of aquatic products.The efficient extraction of flavonoids is beneficial to deepening the application of flavonoids in aquatic products.To explore the optimal way of flavonoid extraction has become a hot research topic.In this study,based on temperature,ultrasonic power and extraction time,the best ways to extract flavonoids from four Chinese herbal medicines,purslane,Verbena,Fructus Amomi and Alpinia oxyphylla,were explored.Through single-factor and multi-factor optimization extraction,the most appropriate conditions for flavonoid extraction were obtained.The results showed that the best way of ultrasonic assisted extraction of flavonoids was purslane at 40℃,300 W(400 W),Verbena at 70℃,400W,Fructus Amomi at 50℃,200 W,and A.oxyphylla at 40℃,400W,and 40 min.The results of orthogonal design showed that purslane could get 13.20 mg/g at 40℃,400 W and 50 min,Verbena could get 10.23 mg/g at 60℃,300 W and 30 min,Fructus Amomi could get 8.18 mg/g at 50℃,300 W and 60 min,and A.oxyphylla could get 7.31 mg/g at 30℃,300 W and 50 min.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51605417)Key Project of Hebei Provincial Natural Science Foundation,China(Grant No.E2016203264)State Key Laboratory of Fluid Power and Mechatronic Systems(Zhejiang University)Open Fund Project(Grant No.GZKF-201502)
文摘Nowadays, a highly integrated valve?controlled cylinder(HIVC) is applied to drive the joints of legged robots. Although the adoption of HIVC has resulted in high?performance robot control, the hydraulic force system still has problems, such as strong nonlinearity, and time?varying parameters. This makes HIVC force control very diffcult and complex. How to improve the control performance of the HIVC force control system and find the influence rule of the system parameters on the control performance is very significant. Firstly, the mathematical model of HIVC force control system is established. Then the mathematical expression for parameter sensitivity matrix is obtained by applying matrix sensitivity analysis(PSM). Then, aimed at the sinusoidal response under(three factors and three levels) working conditions, the simulation and the experiment are conducted. While the error between the simulation and experiment can't be avoided. Therefore, combined with the range analysis, the error in the two performance indexes of sinusoidal response under the whole working condition is analyzed. Besides, the sensitivity variation pattern for each system parameter under the whole working condition is figured out. Then the two sensitivity indexes for the three system parameters, which are supply pressure, proportional gain and initial displacement of piston, are proved experimentally. The proposed method significantly reveals the sensitivity characteristics of HIVC force control system, which can make the contribution to improve the control performance.
基金the open program of State Key Laboratory of Materials Processing and Die&Mould Technology(No.08-04),Huazhong University of Science and Technology,China
文摘Rectangular cross-section specimens with different section thicknesses were prepared to study the infl uences of pouring temperature, mould temperature and squeeze velocity on the fl uidity of squeeze cast AZ91D magnesium alloy by means of orthogonal test design method. The results show that pouring temperature, mould temperature and squeeze velocity can significantly affect the fluidity of magnesium alloy specimens with wall thickness no more than 4 mm, and the pouring temperature is the most infl uential factor on the fl uidity of specimens with wall thickness of 1, 2 and 3 mm, while mould temperature is the one for specimens with wall thickness of 4 mm. Increasing pouring temperature between 700 °C and 750 °C is benefi cial to the fl uidity of AZ91D magnesium alloy, and increasing mould temperature signifi cantly enhances the fi lling ability of thick(3 and 4 mm) section castings. The fl uidity of squeeze cast magnesium alloy increases with the increase of wall thickness. It is not recommended to produce magnesium alloy casting with wall thickness of smaller than 3 mm by squeeze cast process due to the poor fl uidity. The software DPS was used to generate the regression model, and linear regression equations of the fl uidity of squeeze cast AZ91D with different wall thicknesses are obtained using the test results.
基金Supported by High-level Talents Project of Hainan Province(No.2019RC246)the Natural Science Foundation of Hainan Province(No.20163074,No.20163071)"Ichthyology"First-Class Undergraduate Course Construction Project of Hainan Province.
文摘Chinese herbal flavonoids play a role in improving the health of aquatic animals and optimizing the quality of aquatic products.The efficient extraction of flavonoids is beneficial to deepening the application of flavonoids in aquatic products.To explore the optimal way of flavonoid extraction has become a hot research topic.In this study,based on temperature,ultrasonic power and extraction time,the best ways to extract flavonoids from four Chinese herbal medicines,purslane,Verbena,Fructus Amomi and Alpinia oxyphylla,were explored.Through single-factor and multi-factor optimization extraction,the most appropriate conditions for flavonoid extraction were obtained.The results showed that the best way of ultrasonic assisted extraction of flavonoids was purslane at 40℃,300 W(400 W),Verbena at 70℃,400W,Fructus Amomi at 50℃,200 W,and A.oxyphylla at 40℃,400W,and 40 min.The results of orthogonal design showed that purslane could get 13.20 mg/g at 40℃,400 W and 50 min,Verbena could get 10.23 mg/g at 60℃,300 W and 30 min,Fructus Amomi could get 8.18 mg/g at 50℃,300 W and 60 min,and A.oxyphylla could get 7.31 mg/g at 30℃,300 W and 50 min.
