A robust adaptive control approach is presented to improve the performance of the control scheme proposed in the authors＇ previous work, aiming at producing a low ripple hybrid stepping motor servo drive for precisio...A robust adaptive control approach is presented to improve the performance of the control scheme proposed in the authors＇ previous work, aiming at producing a low ripple hybrid stepping motor servo drive for precision profile tracking at a low speed. In order to construct a completely integrated control design philosophy to reduce torque ripple and at the same time to enhance tracking performance, the properties of nonlinear uncertainties in the system dynamics are uncovered, and then incorporated into the design of the controller. The system uncertainties concerned with ripple dynamics and other external disturbances are composed of two categories. The first category of uncertainties with linear parameterization arising from the detention effect is dealt with by the wellknown adaptive control method. A robust adaptive method is used to deal with the second category of uncertainties resulting from the non-sinusoidal flux distribution. The μ-modification scheme is used to cease parameter adaptation by the robust adaptive control law, thus ensuring that the trajectory tracking error asymptotically converges to a pre-specified boundary. Experiments are performed with a typical hybrid stepping motor to test its profile tracking accuracy. Results confirm the proposed control scheme.展开更多
Cardiomyopathies are diseases that primarily affect the myocardium, leading to serious cardiac dysfunction and heart failure. Out of the three major categories of cardiomyopathies （hypertrophic, dilated and restrict...Cardiomyopathies are diseases that primarily affect the myocardium, leading to serious cardiac dysfunction and heart failure. Out of the three major categories of cardiomyopathies （hypertrophic, dilated and restrictive）, restrictive cardiomyopathy （RCM） is less common and also the least studied. However, the prognosis for RCM is poor as some patients dying in their childhood. The molecular mechanisms behind the disease development and progression are not very clear and the treatment of RCM is very difficult and often ineffective. In this article, we reviewed the recent progress in RCM research from the clinical studies and the translational studies done on diseased transgenic animal models. This will help for a better understanding of the mechanisms underlying the etiology and development of RCM and for the design of better treatments for the disease.展开更多
This paper studies the problem of deriving an interface automata model from UML statechart, in which, interface automata is a formaliged model for describing component behavior in an open system, but there is no unive...This paper studies the problem of deriving an interface automata model from UML statechart, in which, interface automata is a formaliged model for describing component behavior in an open system, but there is no universal criterion for deriving behavior from component to construct the model. UML is a widely used modeling standard, yet it is very difficult to apply it to system verification and testing directly for its imprecise semantics. After analyzing the expression ability of the two models, several transforma- tion rules are defined and each step of transformation is described in detail, after that, the approach is illustrated with an example. The paper provides a method for acquiring interface automata and lays the foundation for related research.展开更多
A novel twin-rotor piston engine （TRPE） mechanism with high volumetric output and power density was introduced. This new engine comprises an energy conversion system and a differential velocity drive mechanism （DVD...A novel twin-rotor piston engine （TRPE） mechanism with high volumetric output and power density was introduced. This new engine comprises an energy conversion system and a differential velocity drive mechanism （DVDM）. Two special geared four-bar mechanisms, DVDM-1 and DVDM-2, were utilized and compared. Based on the closed loop vector method, a mathematical model for position, velocity, and acceleration of the two mechanisms was established. Numerical examples illustrate that the kinematic characteristics were presented. Expression of the displacement and compression ratio of the two engine mechanisms were derived and compared. It is concluded that both DVDM-1 and DVDM-2 adopted in the proposed TRPE with six vane pistons create thirty-six power strokes per revolution of the output shaft, and the summation of two angles covered by each rocker is always 2x/N as the output shaft rotates an angle of x/N. In DVDM-1, the span angle of a vane piston should be designed to be 10.2°, and the compression ratio should be equal to 10; in DVDM-2, the span angle of a vane piston should be designed to be 10.6°, and the compression ratio should be equal to 4.3.展开更多
This serial research has proposed the hybrid power system combined the wind power unit with the counter-rotating type pump-turbine unit, to provide the constant output for the grid system, even at the suddenly fluctua...This serial research has proposed the hybrid power system combined the wind power unit with the counter-rotating type pump-turbine unit, to provide the constant output for the grid system, even at the suddenly fluctuating/turbulent wind circumstance. In this paper, the tandem impellers prepared for the counter-rotating type pumping unit were operated at the turbine mode, and the performances and the flow conditions were investigated numerically with accompanying the experimental results. Even though providing the pumping unit for the turbine mode, the maximum hydraulic efficiency is close to one of the counter-rotating type hydroelectric unit designed exclusively for the turbine mode. Besides, the runners/impellers of the unit work evidently so as to coincide the angular momentum change through the front runners/impellers with that through the rear runners/impellers, namely to take the axial flow at not only the inlet but also the outlet, without the guide vanes. From these results, it can be concluded that this type unit is effective to work at not only the pumping but also the turbine modes.展开更多
Hardware neural networks controlled rotational actuators and application to an insect type micro robot are reported in this paper. Millimeter size rotational actuators are fabricated by combining MEMS （Micro Electro ...Hardware neural networks controlled rotational actuators and application to an insect type micro robot are reported in this paper. Millimeter size rotational actuators are fabricated by combining MEMS （Micro Electro Mechanical System） technology and shape memory alloy based artificial muscle wires. The actuator is composed of a pair of disk rotators and each rotor is suspended by four artificial muscle wires that are connected to the silicon frame. The rotational motion is generated by flowing the electrical current to each wire successively. Two actuators of different sizes are fabricated. The large actuator shows the displacement of 0.5 mm at the cycle time of 4 s. The small actuator shows 0.3 mm at 2 s. For controlling the actuator, the hardware neural networks are used. The hardware neural networks are composed of electrical circuits imitating cell bodies, excitatory synapses and inhibitory synapses. Four signal ports are extracted from four pairs of excitatory and inhibitory neurons and they are connected to the actuator. The small actuator is applied to the robot and built in the mid body of the robot. The shaft of the actuator is connected to the link mechanisms that transform the rotational motion to the locomotion. The appearance dimensions of the robot are 4.0, 2.7, 2.5 mm width, length and height. The robot performs forward and backward foot step like insects. The speed is 26.4 mm·min^-1 and the stepping width is 0.88 mm. Also, the robot changes the direction by external trigger pulses.展开更多
The widely used cascade speed and torque controllers have a limited control performance in most high power applications due to the low switching frequency of power electronic converters and the convenience to avoid sp...The widely used cascade speed and torque controllers have a limited control performance in most high power applications due to the low switching frequency of power electronic converters and the convenience to avoid speed overshoots and oscillations for lifetime considerations. Model Predictive Direct Current Control （MPDCC） leads to an increase of torque control performance taking into account the discrete nature of inverters but temporary offsets and poor responses to load torque variations are still issues in speed control. A load torque estimator is proposed in this paper in order to further improve dynamic behavior. It compensates the load torque influence on the speed control setting a feed forward torque reference value. The benefits are twice; the speed controller reaches the speed reference value without offsets which would need to be compensated by an integrator and a better response to load torque variations is obtained since they are detected and compensated leading to small speed variations. Moreover, the influence of pararneter errors and disturbances has been analyzed and limited so that they play a minor role in operation.展开更多
Farmers’livelihoods and their impacts on the ecosystem are important indicators of human-land relationships.Appropriate livelihood strategies for farmers can meet the needs of human well-being and promote the sustain...Farmers’livelihoods and their impacts on the ecosystem are important indicators of human-land relationships.Appropriate livelihood strategies for farmers can meet the needs of human well-being and promote the sustainable use of natural resources,thereby maintaining the health and stability of natural ecosystems.Scholars have carried out a great deal of research on the changes in farmers’livelihoods,as well as the driving mechanisms and ecological effects,but there are still many controversial issues about the ecological effects of farmers’livelihood transformation.On the basis of collecting and sorting out the relevant literature,this paper analyzes the previous research results on the transformation mechanism and ecological effects of farmers’livelihoods,and further explores the coupling relationship.Through the analysis and summary,we find that the choice of farmers’livelihoods is affected by natural factors,subjective willingness and social policies.The transformation of farmers’livelihood changes the ways of production,consumption and resource utilization,which in turn profoundly affects the evolutionary process of the natural ecosystems.This paper establishes a research framework for the livelihood transformation mechanism of farmers and its ecological effect,and finally summarizes two directions that need to be studied further in the future:(1)Exploring the interactions between the driving factors of farmers’livelihood transformation;and(2)Exploring a win-win sustainable mechanism for farmers’livelihood needs and natural resource utilization.展开更多
文摘A robust adaptive control approach is presented to improve the performance of the control scheme proposed in the authors＇ previous work, aiming at producing a low ripple hybrid stepping motor servo drive for precision profile tracking at a low speed. In order to construct a completely integrated control design philosophy to reduce torque ripple and at the same time to enhance tracking performance, the properties of nonlinear uncertainties in the system dynamics are uncovered, and then incorporated into the design of the controller. The system uncertainties concerned with ripple dynamics and other external disturbances are composed of two categories. The first category of uncertainties with linear parameterization arising from the detention effect is dealt with by the wellknown adaptive control method. A robust adaptive method is used to deal with the second category of uncertainties resulting from the non-sinusoidal flux distribution. The μ-modification scheme is used to cease parameter adaptation by the robust adaptive control law, thus ensuring that the trajectory tracking error asymptotically converges to a pre-specified boundary. Experiments are performed with a typical hybrid stepping motor to test its profile tracking accuracy. Results confirm the proposed control scheme.
文摘Cardiomyopathies are diseases that primarily affect the myocardium, leading to serious cardiac dysfunction and heart failure. Out of the three major categories of cardiomyopathies （hypertrophic, dilated and restrictive）, restrictive cardiomyopathy （RCM） is less common and also the least studied. However, the prognosis for RCM is poor as some patients dying in their childhood. The molecular mechanisms behind the disease development and progression are not very clear and the treatment of RCM is very difficult and often ineffective. In this article, we reviewed the recent progress in RCM research from the clinical studies and the translational studies done on diseased transgenic animal models. This will help for a better understanding of the mechanisms underlying the etiology and development of RCM and for the design of better treatments for the disease.
文摘This paper studies the problem of deriving an interface automata model from UML statechart, in which, interface automata is a formaliged model for describing component behavior in an open system, but there is no universal criterion for deriving behavior from component to construct the model. UML is a widely used modeling standard, yet it is very difficult to apply it to system verification and testing directly for its imprecise semantics. After analyzing the expression ability of the two models, several transforma- tion rules are defined and each step of transformation is described in detail, after that, the approach is illustrated with an example. The paper provides a method for acquiring interface automata and lays the foundation for related research.
基金Project(7131109) supported the by National Defense Pre-research Foundation of ChinaProject(50975278) supported by National the Natural Science Foundation of China
文摘A novel twin-rotor piston engine （TRPE） mechanism with high volumetric output and power density was introduced. This new engine comprises an energy conversion system and a differential velocity drive mechanism （DVDM）. Two special geared four-bar mechanisms, DVDM-1 and DVDM-2, were utilized and compared. Based on the closed loop vector method, a mathematical model for position, velocity, and acceleration of the two mechanisms was established. Numerical examples illustrate that the kinematic characteristics were presented. Expression of the displacement and compression ratio of the two engine mechanisms were derived and compared. It is concluded that both DVDM-1 and DVDM-2 adopted in the proposed TRPE with six vane pistons create thirty-six power strokes per revolution of the output shaft, and the summation of two angles covered by each rocker is always 2x/N as the output shaft rotates an angle of x/N. In DVDM-1, the span angle of a vane piston should be designed to be 10.2°, and the compression ratio should be equal to 10; in DVDM-2, the span angle of a vane piston should be designed to be 10.6°, and the compression ratio should be equal to 4.3.
文摘This serial research has proposed the hybrid power system combined the wind power unit with the counter-rotating type pump-turbine unit, to provide the constant output for the grid system, even at the suddenly fluctuating/turbulent wind circumstance. In this paper, the tandem impellers prepared for the counter-rotating type pumping unit were operated at the turbine mode, and the performances and the flow conditions were investigated numerically with accompanying the experimental results. Even though providing the pumping unit for the turbine mode, the maximum hydraulic efficiency is close to one of the counter-rotating type hydroelectric unit designed exclusively for the turbine mode. Besides, the runners/impellers of the unit work evidently so as to coincide the angular momentum change through the front runners/impellers with that through the rear runners/impellers, namely to take the axial flow at not only the inlet but also the outlet, without the guide vanes. From these results, it can be concluded that this type unit is effective to work at not only the pumping but also the turbine modes.
文摘Hardware neural networks controlled rotational actuators and application to an insect type micro robot are reported in this paper. Millimeter size rotational actuators are fabricated by combining MEMS （Micro Electro Mechanical System） technology and shape memory alloy based artificial muscle wires. The actuator is composed of a pair of disk rotators and each rotor is suspended by four artificial muscle wires that are connected to the silicon frame. The rotational motion is generated by flowing the electrical current to each wire successively. Two actuators of different sizes are fabricated. The large actuator shows the displacement of 0.5 mm at the cycle time of 4 s. The small actuator shows 0.3 mm at 2 s. For controlling the actuator, the hardware neural networks are used. The hardware neural networks are composed of electrical circuits imitating cell bodies, excitatory synapses and inhibitory synapses. Four signal ports are extracted from four pairs of excitatory and inhibitory neurons and they are connected to the actuator. The small actuator is applied to the robot and built in the mid body of the robot. The shaft of the actuator is connected to the link mechanisms that transform the rotational motion to the locomotion. The appearance dimensions of the robot are 4.0, 2.7, 2.5 mm width, length and height. The robot performs forward and backward foot step like insects. The speed is 26.4 mm·min^-1 and the stepping width is 0.88 mm. Also, the robot changes the direction by external trigger pulses.
文摘The widely used cascade speed and torque controllers have a limited control performance in most high power applications due to the low switching frequency of power electronic converters and the convenience to avoid speed overshoots and oscillations for lifetime considerations. Model Predictive Direct Current Control （MPDCC） leads to an increase of torque control performance taking into account the discrete nature of inverters but temporary offsets and poor responses to load torque variations are still issues in speed control. A load torque estimator is proposed in this paper in order to further improve dynamic behavior. It compensates the load torque influence on the speed control setting a feed forward torque reference value. The benefits are twice; the speed controller reaches the speed reference value without offsets which would need to be compensated by an integrator and a better response to load torque variations is obtained since they are detected and compensated leading to small speed variations. Moreover, the influence of pararneter errors and disturbances has been analyzed and limited so that they play a minor role in operation.
基金The National Natural Science Foundation of China(41871196)。
文摘Farmers’livelihoods and their impacts on the ecosystem are important indicators of human-land relationships.Appropriate livelihood strategies for farmers can meet the needs of human well-being and promote the sustainable use of natural resources,thereby maintaining the health and stability of natural ecosystems.Scholars have carried out a great deal of research on the changes in farmers’livelihoods,as well as the driving mechanisms and ecological effects,but there are still many controversial issues about the ecological effects of farmers’livelihood transformation.On the basis of collecting and sorting out the relevant literature,this paper analyzes the previous research results on the transformation mechanism and ecological effects of farmers’livelihoods,and further explores the coupling relationship.Through the analysis and summary,we find that the choice of farmers’livelihoods is affected by natural factors,subjective willingness and social policies.The transformation of farmers’livelihood changes the ways of production,consumption and resource utilization,which in turn profoundly affects the evolutionary process of the natural ecosystems.This paper establishes a research framework for the livelihood transformation mechanism of farmers and its ecological effect,and finally summarizes two directions that need to be studied further in the future:(1)Exploring the interactions between the driving factors of farmers’livelihood transformation;and(2)Exploring a win-win sustainable mechanism for farmers’livelihood needs and natural resource utilization.
