This paper presents a contribution related to the control of nonlinear variable-speed marine current turbine(MCT)without pitch operating below the rated marine current speed.Given that the operation of the MCT can be ...This paper presents a contribution related to the control of nonlinear variable-speed marine current turbine(MCT)without pitch operating below the rated marine current speed.Given that the operation of the MCT can be divided into several operating zones on the basis of the marine current speed,the system control objectives are different for each zone.To deal with this issue,we develop a new control approach based on a linear quadratic regulator with variable generator torque.Our proposed approach enables the optimization of the rotational speed of the turbine,which maximizes the power extracted by the MCT and minimizes the transient loads on the drivetrain.The novelty of our study is the use of a real profile of marine current speed from the northern coasts of Morocco.The simulation results obtained using MATLAB Simulink indicate the effectiveness and robustness of the proposed control approach on the electrical and mechanical parameters with the variations of marine current speed.展开更多
This paper describes an improvement of the existing nominal characteristic trajectory following (NCTF) as a practical control method for a two-mass rotary point-to-point (PTP) positioning systems. Generally, the NCTF ...This paper describes an improvement of the existing nominal characteristic trajectory following (NCTF) as a practical control method for a two-mass rotary point-to-point (PTP) positioning systems. Generally, the NCTF controller consists of a nominal characteristic trajectory (NCT) and a PI compensator. A notch filter is added as a part of the compensator to eliminate the vibration due to the mechanical resonance of the plant. The objective of the NCTF controller is to make the object motion follow the NCT and end at its origin. The NCTF controller is designed based on a simple open-loop experiment of the object. The parameters identification and an exact model of the plant are not necessary for controller design. The performance response of improved NCTF controller is evaluated and discussed based on results of simulation. The effect of the design parameters on the robustness of the NCTF controller to inertia and friction variations is evaluated and compared with conventional PID controller. The results show that the improved NCTF controller has a better positioning performance and is much more robust than the PID controller.展开更多
为了减少荔枝汁在加热后产生的“蒸煮”异味,筛选了邻苯三酚、没食子酸、迷迭香酸、儿茶素、抗坏血酸及葡萄糖氧化酶六种抑制剂,从色泽、pH、香气轮廓、电子鼻、挥发性成分、降硫率以及总酚、总黄酮、抗氧化特性等角度去评价六种抑制剂...为了减少荔枝汁在加热后产生的“蒸煮”异味,筛选了邻苯三酚、没食子酸、迷迭香酸、儿茶素、抗坏血酸及葡萄糖氧化酶六种抑制剂,从色泽、pH、香气轮廓、电子鼻、挥发性成分、降硫率以及总酚、总黄酮、抗氧化特性等角度去评价六种抑制剂对荔枝汁风味及营养品质的影响。结果显示抗坏血酸和没食子酸抑制剂处理的样品与新鲜汁相比的色差值最小;整体香气轮廓显示葡萄糖氧化酶抑制蒸煮异味效果最佳,其次为迷迭香酸;电子鼻结果显示葡萄糖氧化酶处理的荔枝汁与新鲜汁最为接近,其次是儿茶素和邻苯三酚。挥发性成分的主成分分析结果显示抗坏血酸抑制剂处理的样品与新鲜汁最接近,其次为没食子酸、儿茶素、迷迭香酸。降硫率结果显示葡萄糖氧化酶的降硫效果最为显著,对二甲基硫醚、二甲基三硫醚、甲硫基丙醛的抑制率均达到100%,对二甲基二硫醚的抑制率为61.11%。营养品质方面,多酚类抑制剂与抗坏血酸处理的总酚、总黄酮含量和抗氧化性较新鲜汁均显著上升(P<0.05),而葡萄糖氧化酶处理的总酚、总黄酮含量较新鲜汁上升但抗氧化活性与新鲜汁无显著差异。综合色泽、pH、香气轮廓、营养品质以及降硫效果等因素进行偏最小二乘判别分析(partial least squares discriminant analysis,PLS-DA),发现葡萄糖氧化酶对荔枝汁整体品质影响最好。本研究可为荔枝以及其他热敏性水果加工过程中品质提升提供参考依据。展开更多
文摘This paper presents a contribution related to the control of nonlinear variable-speed marine current turbine(MCT)without pitch operating below the rated marine current speed.Given that the operation of the MCT can be divided into several operating zones on the basis of the marine current speed,the system control objectives are different for each zone.To deal with this issue,we develop a new control approach based on a linear quadratic regulator with variable generator torque.Our proposed approach enables the optimization of the rotational speed of the turbine,which maximizes the power extracted by the MCT and minimizes the transient loads on the drivetrain.The novelty of our study is the use of a real profile of marine current speed from the northern coasts of Morocco.The simulation results obtained using MATLAB Simulink indicate the effectiveness and robustness of the proposed control approach on the electrical and mechanical parameters with the variations of marine current speed.
文摘This paper describes an improvement of the existing nominal characteristic trajectory following (NCTF) as a practical control method for a two-mass rotary point-to-point (PTP) positioning systems. Generally, the NCTF controller consists of a nominal characteristic trajectory (NCT) and a PI compensator. A notch filter is added as a part of the compensator to eliminate the vibration due to the mechanical resonance of the plant. The objective of the NCTF controller is to make the object motion follow the NCT and end at its origin. The NCTF controller is designed based on a simple open-loop experiment of the object. The parameters identification and an exact model of the plant are not necessary for controller design. The performance response of improved NCTF controller is evaluated and discussed based on results of simulation. The effect of the design parameters on the robustness of the NCTF controller to inertia and friction variations is evaluated and compared with conventional PID controller. The results show that the improved NCTF controller has a better positioning performance and is much more robust than the PID controller.
文摘为了减少荔枝汁在加热后产生的“蒸煮”异味,筛选了邻苯三酚、没食子酸、迷迭香酸、儿茶素、抗坏血酸及葡萄糖氧化酶六种抑制剂,从色泽、pH、香气轮廓、电子鼻、挥发性成分、降硫率以及总酚、总黄酮、抗氧化特性等角度去评价六种抑制剂对荔枝汁风味及营养品质的影响。结果显示抗坏血酸和没食子酸抑制剂处理的样品与新鲜汁相比的色差值最小;整体香气轮廓显示葡萄糖氧化酶抑制蒸煮异味效果最佳,其次为迷迭香酸;电子鼻结果显示葡萄糖氧化酶处理的荔枝汁与新鲜汁最为接近,其次是儿茶素和邻苯三酚。挥发性成分的主成分分析结果显示抗坏血酸抑制剂处理的样品与新鲜汁最接近,其次为没食子酸、儿茶素、迷迭香酸。降硫率结果显示葡萄糖氧化酶的降硫效果最为显著,对二甲基硫醚、二甲基三硫醚、甲硫基丙醛的抑制率均达到100%,对二甲基二硫醚的抑制率为61.11%。营养品质方面,多酚类抑制剂与抗坏血酸处理的总酚、总黄酮含量和抗氧化性较新鲜汁均显著上升(P<0.05),而葡萄糖氧化酶处理的总酚、总黄酮含量较新鲜汁上升但抗氧化活性与新鲜汁无显著差异。综合色泽、pH、香气轮廓、营养品质以及降硫效果等因素进行偏最小二乘判别分析(partial least squares discriminant analysis,PLS-DA),发现葡萄糖氧化酶对荔枝汁整体品质影响最好。本研究可为荔枝以及其他热敏性水果加工过程中品质提升提供参考依据。
