41 results about "Fractional-order control" patented technology

The invention relates to a fractional order PID (Proportion Integration Differentiation) control method and system based on an FPGA (Field Programmable Gate Array). The method comprises the following steps of: 1, setting fractional order PID related parameters according to the requirements of a controlled object; 2, calculating a fractional order calculus weight coefficient according to the fractional order PID related parameters, and storing the fractional order calculus weight coefficient in the FPGA; 3, collecting a state feedback signal of the controlled object, and calculating an integral term operator and a differential term operator; step 4, calculating control output and performing amplitude limiting processing, and updating the state of the controlled object by using the control output after the amplitude limiting processing; and 5, repeating the steps 1-4 to realize fractional order PID closed-loop control. By optimizing a discrete convolution algorithm, adopting a parallel pipeline architecture and configurable parameter design and combining fixed-point number operation and security boundary constraint, the numerical stability and hardware security of the system under high-speed operation are ensured, the calculation speed is remarkably increased while the operation precision is ensured, and the method is suitable for large-scale popularization and application. And the method is suitable for control occasions with extremely high real-time requirements.

The invention aims to provide a self-adaptive fault-tolerant control method under an open-circuit fault of a nine-phase permanent magnet synchronous motor. A system comprises a fractional order PID controller, a nine-phase modular multilevel converter, an SPWM modulator, an improved ADRC controller, an MMC energy controller, a nine-phase current sampling and coordinate transformation module and a nine-phase voltage control and coordinate transformation module. According to the system and the method, the problem that an existing control method is insufficient in control performance in a nine-phase permanent magnet synchronous motor control system can be solved, and the stability, the reliability and the overall performance of the system can be improved.

The present invention relates to the field of wind power generation technology, and more particularly to a method for PID parameter tuning for a wind power generation system. The method collects wind speed data from a random wind speed model and actual generator speed data, calculates the error between the optimal generator speed and the actual generator speed, uses the calculated error as the input signal for a fractional-order PID controller, and optimizes the parameters of the fractional-order PID controller using a differential evolution algorithm. The method utilizes a differential evolution algorithm, which has fast convergence speed and high search accuracy, improving parameter tuning speed and accuracy while offering greater robustness. Furthermore, the method has low reliance on motor parameters during the tuning process, is highly versatile, and can be widely used in engineering practice.

The invention provides a robust design method and system for a fractional order PI controller of an inertia and delay fractional order object. The method comprises the following steps: describing a controlled object by adopting an inertia and delay fractional order transfer function; the feedback controller adopts a fractional order PI controller; a crossing frequency and a phase margin are given, and a proportional gain, an integral gain and a controller order of the fractional order PI controller are solely solved based on three constraint equations of the given crossing frequency, the given phase margin and zero slope of an open-loop phase of a closed-loop system at the crossing frequency; if a null set is solved, the values of the crossing frequency and the phase margin need to be given again, and solving is carried out; and traversing the range of the traversing frequency and the phase margin to obtain a feasible region of the fractional order PI controller. According to the method, the parameters and the feasible region of the fractional order PI controller can be directly calculated, it is guaranteed that the fractional order PI controller has high robustness, and the method has practical application value.

The present invention relates to a chip temperature stability control method; the method comprises: obtaining the difference between the temperature of the chip and a preset operating temperature; constructing a fractional-order PID controller, and constructing a multi-objective constrained fitness function and a single-objective fitness function based on the control time and the driving power; optimizing the parameters of the fractional-order PID controller using a multi-objective adaptive Hippo algorithm based on the fitness function; the multi-objective adaptive Hippo algorithm classifies populations and assigns corresponding fitness functions to different populations for position optimization, thereby achieving global optimization of the controller parameters; utilizing the fractional-order PID controller after parameter optimization, generating control parameters based on the difference between the temperature of the chip and the preset operating temperature; and heating the chip to the preset operating temperature based on the control parameters to complete chip temperature stability control. The present invention solves the problems of premature convergence and local optima in the optimization algorithms in the prior art, thereby improving the chip temperature stability control effect.

The application relates to a complex terrain adaptive gait planning method for a biped robot and the biped robot, and belongs to the technical field of robots, and comprises the following steps: a fractional order PID controller is constructed, the fractional order PID controller comprises a multi-sensor network module, an adaptive module and a fractional order calculus control module; a reinforcement learning model for gait planning of the biped robot is constructed, a state, an action, a decision and a reinforcement learning reward function of the reinforcement learning are set, a policy gradient method is used to continuously iterate and optimally adjust the reinforcement learning model, policy parameters are updated, and control parameters of the biped robot are output; and the control parameters output by the fractional order PID controller and the reinforcement learning model are decisionally fused through a comprehensive loss function, so that globally optimal control parameters of the biped robot are obtained. The application can provide more accurate gait planning for the biped robot in complex terrain, and better walking flexibility and adaptability are achieved.

The application discloses a tension anti-interference control method based on an event triggering mechanism, which comprises the following steps: S1, a surface-mounted permanent magnet synchronous servo motor model is established, and a mathematical model is described to obtain state variables in a speed loop, a current loop, speed and position output of the motor; S2, the obtained data is analyzed to design a sliding mode controller and a fractional order PID controller; S3, a disturbance observer is designed to estimate and compensate the disturbance in the system through the state variables of the double loop, and the robustness of the system is improved; S4, an event triggering mechanism based on nonlinear sliding mode control is designed to reduce the calculation amount of the sliding mode control, reduce the operation demand of the overall system, and complete the control target. The application not only improves the accuracy and response speed of motor control, but also improves the energy efficiency ratio and application range of the system by reducing the calculation amount and optimizing the control algorithm; in the application occasion of high-precision tension control, the stability of the production process and the quality of the product can be remarkably improved.

The invention relates to the technical field of power grid control, in particular to a new energy converter voltage frequency supporting method and system based on fractional order matching control, and the method comprises the steps: configuring rated operation parameters of a converter; collecting operation data of the new energy converter, and calculating an instantaneous power difference of a DC bus; constructing a fractional order transfer function, calculating an additional frequency regulating variable according to the instantaneous power difference, generating an AC port output frequency reference value, and transmitting the AC port output frequency reference value to an outer loop controller to generate a PWM signal; calculating the current available reactive capacity of the converter according to the operation data in combination with the converter, and calculating a reactive voltage droop coefficient; a reactive current reference value is calculated through a second fractional order controller; and adjusting the active power output of the converter according to the PWM signal, and controlling the reactive power of the converter according to the reactive current reference value. According to the invention, by introducing the fractional order control and the adaptive strategy, the dynamic stability and the adaptive capability of the voltage frequency support of the converter are significantly improved.

The invention discloses sampling data self-adaptive backstepping control of an unsymmetrical air handling unit in a heating, ventilation and air conditioning system, which is used for an unsymmetrical fractional order air handling unit in a building heating, ventilation and air conditioning system so as to realize indoor temperature regulation. The method specifically comprises the following steps: constructing an unsymmetrical fractional order model for describing the dynamic behavior of the air handling unit system; designing a sampling data self-adaptive controller based on the constructed unsymmetrical fractional order model so as to realize self-adaptive fractional order control by adopting a sampling data backstepping technology; the invention aims to enhance indoor temperature control even in the presence of system uncertainty and external interference.

The application discloses a parallel circulating current suppression method and device of a fractional order inverter, electronic equipment and a storage medium, and comprises the following steps: establishing a mathematical model of a fractional order inverter comprising a fractional order inductor and a fractional order capacitor, constructing a voltage and current double control loop based on a fractional order controller based on the mathematical model, and tracking and controlling the output voltage and current of the parallel fractional order inverters, and suppressing the circulating current by power sharing of the parallel fractional order inverters through droop control and fractional order virtual impedance. On the one hand, the voltage and current double control loop based on the fractional order controller can track the output voltage of the inverter, improve the tracking effect of the output voltage, reduce the voltage difference between the inverters, and suppress the parallel circulating current. On the other hand, the droop control combined with the fractional order virtual impedance can improve the power distribution response speed of the fractional order inverter, improve the power distribution accuracy between the inverters, and improve the suppression effect of the parallel circulating current.

The invention discloses a heat energy gradient utilization method integrating working condition estimation and fractional derivative, which comprises the following steps: firstly, establishing a waste heat estimation model for a dynamic heat source, and calculating expected heat energy data of a future time window; secondly, the expected data are input into a fractional order fuzzy control model, the model processes the time sequence characteristics of the data by applying fractional order derivatives, and an optimal regulation and control instruction is solved in combination with a fuzzy rule base generated offline; and finally, a flux control valve group is controlled through the instruction, heat source gas is sequentially distributed into the high-temperature reaction module, the medium-temperature reaction module and the low-temperature reaction module, and gradient recovery of heat energy is achieved. According to the method, passive response is replaced by active pre-judgment, the problem of control lag when the dynamic heat source working condition changes drastically is effectively solved by fusing the prediction model and fractional order control, and the heat recovery efficiency and the system robustness are remarkably improved.

The application provides a kind of intelligent vehicle steer-by-wire motor control method, and the steer-by-wire motor adopts double closed-loop control of rotation angle ring and current loop;The rotation angle ring is controlled by an improved nonlinear active-disturbance rejection controller, and the current loop is controlled by a fractional order PID controller;The improved nonlinear active-disturbance rejection controller includes an improved third-order nonlinear extended state observer and a nonlinear state error feedback control law, wherein the nonlinear state error feedback control law adopts a super-spiral second-order sliding mode control.The method enhances the anti-interference and robustness of the steer-by-wire motor system, improves the estimation accuracy of the observer, and improves the tracking performance of the steer-by-wire motor.

The application belongs to the technical field of mechanical arm control and grasping, and in particular to a mechanical arm grasping method based on FO-DDPG. The application introduces a fractional order control theory to select the motion of the mechanical arm, and introduces a fractional order discount factor to calculate a fractional order return, so as to better handle the decay of long-term rewards. The application can more accurately model and handle complex nonlinear, non-local and long-time dependent dynamic systems; improve the estimation accuracy of the value function to better guide the grasping decision of the mechanical arm; enhance the decision quality and robustness of the policy function by more accurately utilizing past experience; increase the performance and stability of the algorithm, improve the success rate and efficiency of the mechanical arm in the grasping task, and enable the mechanical arm to successfully perform grasping operations under different environmental and object characteristics.

This invention discloses a grid-connected frequency control method for a doubly-fed induction generator (DFIG) based on a fractional-order adaptive virtual synchronous generator (VSSG), belonging to the field of wind power grid-connected control technology. The method first establishes a mathematical model for DFIG grid connection and monitors grid frequency and active power in real time. Second, it constructs a grid-side VSG control model, analyzes the influence of rotational inertia J and damping coefficient D on the system's dynamic response, and designs adaptive VSG control. Based on this, fractional-order control theory is introduced, and a fractional-order VSG control module is designed. The system's frequency regulation performance is optimized using a non-integer-order differential operator. Finally, the controller parameters are optimized to achieve rapid dynamic response and frequency stability. By combining fractional-order control and adaptive VSG strategies, this invention effectively suppresses power oscillations and frequency overshoot during grid frequency fluctuations, improving the frequency support capability and transient stability of the DFIG grid-connected system. It is suitable for frequency control applications in power systems with a high proportion of renewable energy integration.

The invention discloses a parallel circulating current suppression method and device for a fractional-order inverter, electronic equipment and a storage medium, and the method comprises the steps: building a mathematical model of the fractional-order inverter which comprises a fractional-order inductor and a fractional-order capacitor, and building a voltage and current dual-control loop based on a fractional-order controller based on the mathematical model, according to the method, the fractional order inverters are connected in parallel, the output voltage and current of the fractional order inverters connected in parallel are tracked and controlled, and the power of the fractional order inverters connected in parallel are equally divided through droop control and fractional order virtual impedance so as to restrain circulating current, on one hand, the output voltage of the inverters is tracked based on a voltage and current dual-control loop of a fractional order controller, and on the other hand, the output voltage of the inverters is controlled; on the one hand, the tracking effect of the output voltage can be improved, the voltage difference between the inverters can be reduced to suppress the parallel circulating current, on the other hand, the fractional order virtual impedance is combined for droop control, the power distribution response speed of the fractional order inverters can be improved, the power distribution precision between the inverters can be improved, and the suppression effect of the parallel circulating current can be improved.

The invention discloses a monitoring internet-of-things control platform based on a chemical production system. A distributed sensor array is used for collecting the temperature T (t), the pressure P (t) and the substance concentration Ci (t) in a chemical reaction kettle in real time; the edge computing node is used for realizing parameter dynamic compensation through a fractional order PID (Proportion Integration Differentiation) controller; and the cloud platform optimization module adopts an improved NSGA-II algorithm to solve a multi-objective optimization problem: high-precision dynamic control: through a fractional order PID controller and a Lyapunov stability design, the oscillation problem of traditional integer order PID in a nonlinear chemical process is solved. The actual measurement control precision is improved by 52%, the temperature fluctuation range is reduced from + / -5 DEG C to + / -2.1 DEG C, and the reaction efficiency is remarkably improved.

The invention discloses a fractional order PI controller parameter setting method and device, a storage medium and a terminal, and the method comprises the steps: obtaining a plurality of groups of initial parameters used for controlling a PWM rectifier in a PI controller, the initial parameters comprising an integral order, a proportionality coefficient and an integral coefficient; setting the initial parameters by utilizing a water circulation algorithm, taking a plurality of groups of initial parameters as initial raindrops of the water circulation algorithm, and classifying the initial raindrops to obtain a stream population, a river population and a sea population; iteration is at least carried out on the initial raindrops, iteration is stopped until the preset number of iterations is reached, and a sea population is output; through multiple rounds of iteration, raindrops flow among the populations, new raindrops are generated for the populations meeting the evaporation conditions, the positions of the new raindrops are updated through rainfall, and finally the sea populations are output; and controlling the PWM rectifier through a fractional order PI controller based on the parameters corresponding to the sea population obtained by the last iteration. According to the invention, the control precision and the dynamic performance of the PWM rectifier are obviously improved.

The invention discloses a wireless communication power control method based on a fractional calculus theory, which comprises the following steps of: firstly, constructing a continuous time stochastic differential equation channel model driven by a symmetric-stable Levy process, and respectively depicting heavy tail jump behaviors in long-term path loss and short-term multipath fading; then, on the basis of the channel model, a generalized Riesz fractional order derivative operator is introduced, a class of fractional order HJB (FHJB) control equations with non-local operators are deduced under the dynamic programming principle, and the fractional order HJB (FHJB) control equations are used for describing an optimal power control strategy under the infinite variance interference condition; and finally, in a multi-base-station multi-user same-frequency interference scene, constructing a fractional order FHJB power control solution framework, obtaining an optimal transmitting power distribution strategy by using a value function iteration method, and verifying the robustness and communication quality assurance capability of the optimal transmitting power distribution strategy under a jump fading channel through numerical simulation. According to the invention, adaptive control of the transmitting power in a non-stationary and heavy-tailed fading environment can be realized.

The invention relates to the technical field of flywheel energy storage control, in particular to a particle swarm fractional order power control method and system for a flywheel energy storage system, and the method comprises the steps: collecting system operation data in real time, processing a power tracking error through a fractional order PI lambda controller, and carrying out the continuous iteration optimization of the core parameters of the controller through a particle swarm algorithm; more accurate power tracking can be achieved, meanwhile, coupling interference of d-axis current and q-axis current can be eliminated through feedforward decoupling control of the machine-side converter, stable direct-current bus voltage is maintained through cooperation with voltage-current double-closed-loop control of the grid-side converter, the running state adjusting smoothness of the flywheel motor and the grid-connected running stability of the system can be improved, and the system stability is improved. The impact of the grid-connected process on the power grid is reduced, and the loop iteration control flow can enable the system to adaptively adjust the control strategy, always maintain the optimal operation state, reduce the electric energy loss, improve the overall operation efficiency of the system, and ensure that the flywheel energy storage system stably and efficiently completes power scheduling and grid-connected operation.

The invention relates to the technical field of unmanned aerial vehicles, and particularly provides a four-rotor unmanned aerial vehicle cascade control method. The method comprises the following steps: acquiring a mathematical model of the quad-rotor unmanned aerial vehicle; designing a cascade control framework of position incremental model predictive control-attitude fractional order PID (Proportion Integration Differentiation) control; according to the method, a non-linear cross iteration strategy is designed, controller parameters in a cascade control framework are optimized by taking the minimum tracking error square as a target, the optimal parameters can be quickly and accurately searched, and the external disturbance resistance is improved while the tracking performance is ensured.

The invention discloses a fusion image perception and variable-order fractional order motion control method, and belongs to the technical field of automatic control. The method comprises the following steps: establishing a sliding platform coordinate system; a target image is collected through binocular vision, and three-dimensional coordinates of a target object are extracted through median filtering, weighted equalization, edge masking and binarization processing; constructing an error function according to the target three-dimensional coordinates and the current position of the motor, and constructing a nonlinear order function in combination with target speed derivative information; the function is substituted into a speed ring of a three-ring control structure, a variable-order fractional order controller is adopted, a fractional order operator is quickly approached through improved polynomial fitting and dichotomy, an optimal control quantity is generated in real time to drive a three-axis motor, and high-precision tracking control over a target object is achieved. According to the method, image perception and variable-order control are deeply fused, and the tracking precision, the response speed and the adaptive capacity of the system in a complex dynamic scene are effectively improved.

The application discloses a kind of based on fractional order PID and fractional order terminal sliding mode quadrotor unmanned aerial vehicle control method, comprising (1) the dynamics model of quadrotor unmanned aerial vehicle is established;(2) construct fractional order PID controller, the desired position of unmanned aerial vehicle and actual position input fractional order PID controller, obtain the control output of unmanned aerial vehicle in X, Y, Z axis direction;(3) according to step (2) control output and current attitude angle are calculated out the desired attitude angle of unmanned aerial vehicle;(4) determine attitude error;(5) construct fractional order terminal sliding surface and obtain the equivalent control law of this fractional order terminal sliding;(6) design fractional order terminal sliding switch control law, combine switch control law and equivalent control law obtain fractional order terminal sliding attitude controller;(7) design Lyapunov function and prove the stability of fractional order terminal sliding attitude controller by Lyapunov theorem.The application guarantees that unmanned aerial vehicle keeps attitude stable when being disturbed by air flow factor.

The invention discloses a control method and device for reducing the influence of high-temperature bar feeding on a main shaft / main beam, and belongs to the technical field of bar rolling equipment. According to the method, independent cooling channels are arranged in a hollow main shaft and a main beam, a non-integer order thermodynamic model is established, an improved self-adaptive filtering fractional order PID controller containing a thermal state weighting function and an error weighting function is constructed, and accurate suppression of temperature rise of the main shaft and the main beam is achieved. The device comprises a double-channel C-shaped groove, a hollow main shaft, a hollow main beam, a circulating cooling system, a temperature detection unit and a control unit. The problems of thermal deformation and jamming caused by high-temperature bar feeding are effectively solved, and the equipment stability and the production efficiency are improved.

The application provides a micro-grid hierarchical fractional order robust control method based on neural network order estimation, and belongs to the technical field of micro-grid control. The application establishes the mapping relationship between the micro-grid operation state parameters and the fractional order PID controller order parameters by constructing a neural network order estimator, adopts the fractional order PID controller which has better dynamic performance than the integer order PID, increases the adjustable integral order and differential order, and combines the self-optimization ability of the LSTM neural network, so that the fractional order PID controller can obtain more suitable parameter configuration under different working conditions. Meanwhile, the application establishes a small signal model of the micro-grid closed-loop system, constructs the stability criterion and the stability domain boundary based on the frequency domain analysis method, and checks and corrects the order parameters. The application significantly improves the adaptability of the system to complex working condition changes, improves the transient control performance of the micro-grid, reduces the overshoot and shortens the regulation time.

The invention discloses a fractional-order modeling method for a single-phase power spring, belonging to the technical field of power electronic system modeling. The modeling method includes establishing fractional-order mathematical models of a fractional-order filter inductor and a fractional-order filter capacitor, a fractional-order mathematical model of the single-phase power spring, and a fractional-order small-signal model of the single-phase power spring. Aiming at the problem that the current models of single-phase power springs are usually integer-order models established by using integer-order inductors and capacitors, and there are large deviations between the modeling and analysis results and the actual system, considering the fractional-order characteristics of actual inductors and capacitors, the above models are established, which can be conveniently used for the analysis of the operating characteristics of single-phase power springs and the design of their fractional-order controllers, improving the operating performance and control effect. Compared with the integer-order model, the fractional-order model can achieve high-precision simulation of the output waveform, with a smaller difference from the actual system, and can better reflect the essence of the actual system.

The invention belongs to the technical field of power system frequency control, provides a power system frequency control method based on fractional order and electric vehicle energy storage cooperation, and realizes coordinated adjustment of frequency deviation, tie line power fluctuation and rotating speed change by establishing a wind energy conversion model, a PEV frequency response model and a fractional order PID controller. According to the system, a Rao algorithm is adopted to optimize fractional order PID control parameters, the minimum frequency deviation square integral serves as a target function, and frequency stabilization is achieved under load disturbance. The fractional order PID control law is composed of a proportion link, a fractional order integral link and a fractional order differential link, and virtual inertia support is achieved through an inertia simulation link. The PEV automatically adjusts the charging and discharging power according to the frequency deviation, and participates in primary and secondary frequency response. According to the method, the frequency stability of the low-inertia system can be effectively improved, the stabilization time is shortened, the lowest point of the frequency is reduced, the robustness and immunity of the system are improved, and the method has good engineering feasibility.

The invention discloses a control method and device of a photovoltaic tracking motor, electronic equipment and a storage medium, and relates to the technical field of new energy power generation. The method comprises the following steps: acquiring ideal input and actual output signals of a photovoltaic support, and constructing a speed-current double closed-loop control system; wherein the speed loop adopts an improved fractional order active disturbance rejection control algorithm, and the algorithm is executed by a controller comprising a fractional order nonlinear differentiator, a fractional order PID controller and a fractional order expansion state observer. The fractional order nonlinear differentiator is configured with an improved steepest tracking function constructed based on a hyperbolic tangent function, and a smoothing factor is used for carrying out continuous processing on a control quantity so as to replace step mutation of a sign function at a zero point. According to the invention, by optimizing the control algorithm structure, the non-continuous sudden change of the control signal is eliminated, the high-frequency oscillation is effectively suppressed, and the stability and response speed of the photovoltaic tracking system in a complex environment are improved.

The invention discloses a motor control method and system based on a fractional order disturbance observer and a fractional order auxiliary system, and the method comprises the steps: constructing a permanent magnet synchronous motor nonlinear system comprising time-varying disturbance and input saturation according to the physical characteristics of a permanent magnet synchronous motor; designing a fractional order interference observer to estimate time-varying interference; constructing a fractional order auxiliary system to process an input saturation problem in a permanent magnet synchronous motor nonlinear system; integrating the fractional order disturbance observer and the fractional order auxiliary system to obtain an actual fractional order controller; and controlling the permanent magnet synchronous motor through the obtained fractional order controller. A fractional order interference observer is synthesized to estimate time-varying interference, and a fractional order auxiliary system is used to process the input saturation problem in a permanent magnet synchronous motor nonlinear system, so that the estimation capability of the time-varying interference is enhanced, and the adverse effect of the input saturation on the system is effectively processed; and the closed-loop system stability and robustness of the permanent magnet synchronous motor nonlinear system are improved.

The invention discloses a fractional order active disturbance rejection control method for a fractional order chaotic system, and the method comprises the following steps: constructing a mathematical model of a fractional order Lorenz chaotic system according to a fractional order calculus theory; designing a fractional order tracking differentiator in order to accurately extract fractional order differential information of a system state variable; designing a fractional order expansion state observer for observing the total disturbance of the fractional order chaotic system; comparing the output of the fractional order expansion state observer with the output of the fractional order tracking differentiator to obtain an error signal, and designing a fractional order PID controller; and designing a fractional order active disturbance rejection controller to realize stable control of the fractional order Lorenz system. The fractional order active-disturbance-rejection control method for the fractional order chaotic system effectively makes up for the defects of the existing control technology, and remarkably improves the control precision, the anti-interference capability and the chaos phenomenon suppression capability of the fractional order chaotic system.

The application relates to a control system and an optimization control method based on a composite controller and relates to the field of advanced control technology. The existing nonlinear time-delay system is generally present in complex industrial control and automation systems, and traditional control strategies are difficult to effectively cope with the problems caused by time delay and nonlinearity. The application eliminates the influence of time delay in the system by designing a Smith predictor, and introduces a fractional order controller to enhance the adaptability of the system to nonlinear behavior. The composite controller formed by combining the Smith predictor and the fractional order controller can significantly improve the dynamic response performance and control accuracy of the system. In order to further optimize the controller parameters, an improved artificial rabbit optimization algorithm is adopted. The algorithm improves the global search ability and convergence speed by introducing a dynamic adjustment factor, a Levy flight strategy and a boundary control strategy.