The arm driven inverted pendulum system is a highly nonlinear model, muhivariable and absolutely unstable dynamic system so it is very difficult to obtain exact mathematical model and balance the inverted pendulum wit...The arm driven inverted pendulum system is a highly nonlinear model, muhivariable and absolutely unstable dynamic system so it is very difficult to obtain exact mathematical model and balance the inverted pendulum with variable position of the ann. To solve this problem, this paper presents a mathematical model for arm driven inverted pendulum in mid-position configuration and an adaptive gain scheduling linear quadratic regulator control method for the stabilizing the inverted pendulum. The proposed controllers for arm driven inverted pendulum are simulated using MATLAB-SIMULINK and implemented on an experiment system using PIC 18F4431 mieroeontroller. The result of experiment system shows the control performance to be very good in a wide range stabilization of the arm position.展开更多
In this study, in order to investigate the power consumption of feed drive system, mathematical models for the single-axis experimental apparatus are developed. This apparatus can be driven by either of ball screw or ...In this study, in order to investigate the power consumption of feed drive system, mathematical models for the single-axis experimental apparatus are developed. This apparatus can be driven by either of ball screw or linear motor and it is possible to change the mechanical properties of such as grease viscosity of the table. Then, the power consumption is simulated by proposed method based on the mathematical model of feed drive systems and the simulated results are compared with the measured results of the experimental apparatus to confirm the validity of the proposed method. In addition, it is clarified that the energy usages of the feed drive system. The energy losses of the feed drive system are divided into the loss of each part and these energy losses are calculated by the proposed method. Then, it is investigated that the influence of the velocity and friction to the energy consumption of feed drive system. As the results, it is confirmed that proposed method can accurately predict the power consumption of the ball-screw feed drive system. It is also clarified that the energy usage for both of ball-screw and linear motor drive systems.展开更多
In the stock pricing, liquidity risk has become one of the important factors that affect the stock realizable value. Systematic and unsystematic risk decided a stock＇s liquidity risk. The author uses the stock price ...In the stock pricing, liquidity risk has become one of the important factors that affect the stock realizable value. Systematic and unsystematic risk decided a stock＇s liquidity risk. The author uses the stock price index growth rate and net outer disk ratio to describe a systematic and unsystematic risk faced by investors. With the help of correlation and regression analysis in SPSS software, the paper tries to establish the systematic and unsystematic risk-driven stock liquidity risk pricing model. Empirical study shows that systematic and unsystematic risk has significant influence on stock liquidity risk. The bigger circulation stock, the greater the systemic risk influence; the less the circulation stock, the larger the non-system risk influence. Calendar factor on stock returns ratio has no significant effect. Trading volume on the stock returns ratio of small companies had no significant effect. The model has important reference value for the measure of stock liquidity risk value loss.展开更多
The control of nuclear fuel manipulator crane （MC） drive system is essential for its running and other systems are designed surrounding the drive system.This paper gives a brief introduction to the composition and f...The control of nuclear fuel manipulator crane （MC） drive system is essential for its running and other systems are designed surrounding the drive system.This paper gives a brief introduction to the composition and function of MC,analyses its drive mode and control method and applies PLC to control its frequency transducer directly to help the motor work more stable.Based on the control requirements of bridge,trolley,Hoist,the control system of bridge applies a drive mode with 2-drag2 drive model on both sides and a multi-control method to realize simultaneous runningof two sides,1-drag-1 model on through-going axes and closed loop control method finish the precise location of trolley,and the using of 1-drag-1 model drive mode and closed loop control method solves the protect control difficulty of hoist which stops/starts repeatedly and changes speed.展开更多
The paper presents physical and mathematical models of kinetic system, drive system （electric and combustion traction motors）, and also wheel and rails traction vehicle supply system （car, special vehicle, modern t...The paper presents physical and mathematical models of kinetic system, drive system （electric and combustion traction motors）, and also wheel and rails traction vehicle supply system （car, special vehicle, modern tram vehicle）. Selected predictive and quasi dynamic control system algorithms of traction vehicle are presented in the paper. For selected constructions of traction vehicle drive system are presented in simulation models and are results of calculations of different exploitations work state of wheel vehicle with hybrid drive system. Results of computer calculations are verified with laboratory measurement and suitable corrections coefficient to simulations models of vehicles is introduced.展开更多
Deforestation is a major environmental challenge in the mountain areas of Pakistan. The study assessed trends in the forest cover in Chitral tehsil over the last two decades using supervised land cover classification ...Deforestation is a major environmental challenge in the mountain areas of Pakistan. The study assessed trends in the forest cover in Chitral tehsil over the last two decades using supervised land cover classification of Landsat TM satellite images from 1992, 2000, and 2009, with a maximum likelihood algorithm. In 2009, the forest cover was 10.3% of the land area of Chitral(60,000 ha). The deforestation rate increased from 0.14% per annum in 1992–2000 to 0.54% per annum in 2000–2009, with 3,759 ha forest lost over the 17 years. The spatial drivers of deforestation were investigated using a cellular automaton modelling technique to project future forest conditions. Accessibility(elevation, slope), population density, distance to settlements, and distance to administrative boundary were strongly associated with neighbourhood deforestation. A model projection showed a further loss of 23% of existing forest in Chitral tehsil by 2030, and degradation of 8%, if deforestation continues at the present rate. Arandu Union Council, with 2212 households, will lose 85% of its forest. Local communities have limited income resources and high poverty and are heavily dependent on non-timber forest products for their livelihoods. Continued deforestation will further worsen their livelihood conditions, thus improved conservation efforts are essential.展开更多
Gear drives are one of the most common parts in many rotating machinery. If the gear drive runs under lower torque load, nonlinear effects like gear mesh interruption can occur and vibration is accompanied by impact m...Gear drives are one of the most common parts in many rotating machinery. If the gear drive runs under lower torque load, nonlinear effects like gear mesh interruption can occur and vibration is accompanied by impact motions of the gears, This paper presents an original method of the mathematical modelling of gear drive nonlinear vibrations by using the modal synthesis method with degrees of freedom number reduction. The model respects nonlinearities caused by gear mesh interruption, parametric gearing excitation caused by time-varying meshing stiffness and nonlinear contact forces acting between journals of the rolling-element bearings and the outer housing. The nonlinear model is then used for investigation of gear drive vibration, especially for constant gear mesh determination. The theoretical method is applied for investigating of test gear drive nonlinear vibration.展开更多
Step motors, compared to other drive systems, are low-cost and easy to use devices. However, despite these undeniable advantages, they are characterized by some critical running conditions, due to the loss of synchron...Step motors, compared to other drive systems, are low-cost and easy to use devices. However, despite these undeniable advantages, they are characterized by some critical running conditions, due to the loss of synchronization between the stator＇s magnetic field and the rotor. In order to theoretically investigate such a behavior, several complex mathematical models have been developed, which require several parameters to be defined. For most step motors, such parameters cannot be easily drawn from their data-sheets; on the contrary, in this paper the authors refer to a simplified electro-mechanical model where the most of the parameters are known from data-sheets. The dependence between electrical and mechanical quantities can be investigated by an experimental point of view. At this aim, a specific novel test rig has been designed and developed for either static or dynamic characteristics measurement of small size step motors. In particular, the test rig allow to measure rotor＇s angular position, motor＇s torque, currents flowing in the motor＇s phases. The paper ends with the report of the results of several experimental tests, carried-out on a small-size motor in different running conditions, and with some preliminary remarks on the basis of the measures analysis.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
The Tibetan Plateau(TP)and Arctic permafrost constitute two large reservoirs of organic carbon,but processes which control carbon accumulation within the surface soil layer of these areas would differ due to the inter...The Tibetan Plateau(TP)and Arctic permafrost constitute two large reservoirs of organic carbon,but processes which control carbon accumulation within the surface soil layer of these areas would differ due to the interplay of climate,soil and vegetation type.Here,we synthesized currently available soil carbon data to show that mean organic carbon density in the topsoil(0-10 cm)in TP grassland(3.12±0.52 kg C m^(-2))is less than half of that in Arctic tundra(6.70±1.94 kg C m^(-2)).Such difference is primarily attributed to their difference in radiocarbon-inferred soil carbon turnover times(547 years for TP grassland versus 1609 years for Arctic tundra)rather than to their marginal difference in topsoil carbon inputs.Our findings highlight the importance of improving regional-specific soil carbon turnover and its controlling mechanisms across permafrost affected zones in ecosystem models to fully represent carbon-climate feedback.展开更多
文摘The arm driven inverted pendulum system is a highly nonlinear model, muhivariable and absolutely unstable dynamic system so it is very difficult to obtain exact mathematical model and balance the inverted pendulum with variable position of the ann. To solve this problem, this paper presents a mathematical model for arm driven inverted pendulum in mid-position configuration and an adaptive gain scheduling linear quadratic regulator control method for the stabilizing the inverted pendulum. The proposed controllers for arm driven inverted pendulum are simulated using MATLAB-SIMULINK and implemented on an experiment system using PIC 18F4431 mieroeontroller. The result of experiment system shows the control performance to be very good in a wide range stabilization of the arm position.
文摘In this study, in order to investigate the power consumption of feed drive system, mathematical models for the single-axis experimental apparatus are developed. This apparatus can be driven by either of ball screw or linear motor and it is possible to change the mechanical properties of such as grease viscosity of the table. Then, the power consumption is simulated by proposed method based on the mathematical model of feed drive systems and the simulated results are compared with the measured results of the experimental apparatus to confirm the validity of the proposed method. In addition, it is clarified that the energy usages of the feed drive system. The energy losses of the feed drive system are divided into the loss of each part and these energy losses are calculated by the proposed method. Then, it is investigated that the influence of the velocity and friction to the energy consumption of feed drive system. As the results, it is confirmed that proposed method can accurately predict the power consumption of the ball-screw feed drive system. It is also clarified that the energy usage for both of ball-screw and linear motor drive systems.
文摘In the stock pricing, liquidity risk has become one of the important factors that affect the stock realizable value. Systematic and unsystematic risk decided a stock＇s liquidity risk. The author uses the stock price index growth rate and net outer disk ratio to describe a systematic and unsystematic risk faced by investors. With the help of correlation and regression analysis in SPSS software, the paper tries to establish the systematic and unsystematic risk-driven stock liquidity risk pricing model. Empirical study shows that systematic and unsystematic risk has significant influence on stock liquidity risk. The bigger circulation stock, the greater the systemic risk influence; the less the circulation stock, the larger the non-system risk influence. Calendar factor on stock returns ratio has no significant effect. Trading volume on the stock returns ratio of small companies had no significant effect. The model has important reference value for the measure of stock liquidity risk value loss.
基金Supported by the National High Technology Research and Development Program of China(No.SQ2010AA0401265006)
文摘The control of nuclear fuel manipulator crane （MC） drive system is essential for its running and other systems are designed surrounding the drive system.This paper gives a brief introduction to the composition and function of MC,analyses its drive mode and control method and applies PLC to control its frequency transducer directly to help the motor work more stable.Based on the control requirements of bridge,trolley,Hoist,the control system of bridge applies a drive mode with 2-drag2 drive model on both sides and a multi-control method to realize simultaneous runningof two sides,1-drag-1 model on through-going axes and closed loop control method finish the precise location of trolley,and the using of 1-drag-1 model drive mode and closed loop control method solves the protect control difficulty of hoist which stops/starts repeatedly and changes speed.
文摘The paper presents physical and mathematical models of kinetic system, drive system （electric and combustion traction motors）, and also wheel and rails traction vehicle supply system （car, special vehicle, modern tram vehicle）. Selected predictive and quasi dynamic control system algorithms of traction vehicle are presented in the paper. For selected constructions of traction vehicle drive system are presented in simulation models and are results of calculations of different exploitations work state of wheel vehicle with hybrid drive system. Results of computer calculations are verified with laboratory measurement and suitable corrections coefficient to simulations models of vehicles is introduced.
基金funded by the Ministry of Foreign Affairs,Norway and Swedish International Development Agency(Sida)supported by the United States Agency for International Development(USAID)National Aeronautics and Space Administration(NASA)
文摘Deforestation is a major environmental challenge in the mountain areas of Pakistan. The study assessed trends in the forest cover in Chitral tehsil over the last two decades using supervised land cover classification of Landsat TM satellite images from 1992, 2000, and 2009, with a maximum likelihood algorithm. In 2009, the forest cover was 10.3% of the land area of Chitral(60,000 ha). The deforestation rate increased from 0.14% per annum in 1992–2000 to 0.54% per annum in 2000–2009, with 3,759 ha forest lost over the 17 years. The spatial drivers of deforestation were investigated using a cellular automaton modelling technique to project future forest conditions. Accessibility(elevation, slope), population density, distance to settlements, and distance to administrative boundary were strongly associated with neighbourhood deforestation. A model projection showed a further loss of 23% of existing forest in Chitral tehsil by 2030, and degradation of 8%, if deforestation continues at the present rate. Arandu Union Council, with 2212 households, will lose 85% of its forest. Local communities have limited income resources and high poverty and are heavily dependent on non-timber forest products for their livelihoods. Continued deforestation will further worsen their livelihood conditions, thus improved conservation efforts are essential.
文摘Gear drives are one of the most common parts in many rotating machinery. If the gear drive runs under lower torque load, nonlinear effects like gear mesh interruption can occur and vibration is accompanied by impact motions of the gears, This paper presents an original method of the mathematical modelling of gear drive nonlinear vibrations by using the modal synthesis method with degrees of freedom number reduction. The model respects nonlinearities caused by gear mesh interruption, parametric gearing excitation caused by time-varying meshing stiffness and nonlinear contact forces acting between journals of the rolling-element bearings and the outer housing. The nonlinear model is then used for investigation of gear drive vibration, especially for constant gear mesh determination. The theoretical method is applied for investigating of test gear drive nonlinear vibration.
文摘Step motors, compared to other drive systems, are low-cost and easy to use devices. However, despite these undeniable advantages, they are characterized by some critical running conditions, due to the loss of synchronization between the stator＇s magnetic field and the rotor. In order to theoretically investigate such a behavior, several complex mathematical models have been developed, which require several parameters to be defined. For most step motors, such parameters cannot be easily drawn from their data-sheets; on the contrary, in this paper the authors refer to a simplified electro-mechanical model where the most of the parameters are known from data-sheets. The dependence between electrical and mechanical quantities can be investigated by an experimental point of view. At this aim, a specific novel test rig has been designed and developed for either static or dynamic characteristics measurement of small size step motors. In particular, the test rig allow to measure rotor＇s angular position, motor＇s torque, currents flowing in the motor＇s phases. The paper ends with the report of the results of several experimental tests, carried-out on a small-size motor in different running conditions, and with some preliminary remarks on the basis of the measures analysis.
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This work was supported by Preliminary Research on Three Poles Environment and Climate Change(2019YFC1509103)the National Natural Science Foundation of China(41861134036 and 41922004)+1 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0606)the Strategic Priority Research Program(A)of the Chinese Academy of Sciences(XDA19070303 and XDA20050101).
文摘The Tibetan Plateau(TP)and Arctic permafrost constitute two large reservoirs of organic carbon,but processes which control carbon accumulation within the surface soil layer of these areas would differ due to the interplay of climate,soil and vegetation type.Here,we synthesized currently available soil carbon data to show that mean organic carbon density in the topsoil(0-10 cm)in TP grassland(3.12±0.52 kg C m^(-2))is less than half of that in Arctic tundra(6.70±1.94 kg C m^(-2)).Such difference is primarily attributed to their difference in radiocarbon-inferred soil carbon turnover times(547 years for TP grassland versus 1609 years for Arctic tundra)rather than to their marginal difference in topsoil carbon inputs.Our findings highlight the importance of improving regional-specific soil carbon turnover and its controlling mechanisms across permafrost affected zones in ecosystem models to fully represent carbon-climate feedback.
