Qinglin Sun

Pressure Regulation for Oxygen Mask Based on Active Disturbance Rejection Control

Safe and reliable automatic pressure regulation for the oxygen mask is a primary consideration in an oxygen supply system (OSS). In order to enhance comfort of users, it is of significance to improve performance of the oxygen regulator. Based on analyses of the operation principle of electronic oxygen regulator (EOR), a new EOR is designed, where a proportional flow valve is adopted as the throttle valve, and an active disturbance rejection control (ADRC) strategy is applied to control the throttle valve. The external disturbances and the internal dynamics are estimated using an extended state observer. The dynamic compensation using a state error feedback in each sampling period reduces the plant approximately to an integrator tandem structure. Mathematical simulations are performed for the OSS to evaluate the control method compared with the proportional integral derivative (PID) control approach. The simulation and experimental results demonstrate that the ADRC can achieve precise pressure regulation with superior lower inspiratory resistance than the PID method, considering some environmental disturbances including the users changing pulmonary ventilation. The work in this paper may be a reference for the EOR design.

Autonomous homing control of a powered parafoil with insufficient altitude

In order to realize safe and accurate homing of a powered parafoil under the condition of insufficient initial altitude, a multiphase homing path is designed according to the flight characteristics of the vehicle. With consideration that the traditional control methods cannot ensure the quality of path following because of the nonlinear, large inertial and longtime delay existed in the system and strong disturbances in a complex environment, a homing controller, composed of the vertical and horizontal trajectory tracking controllers, is designed based on active disturbance rejection control (ADRC). Then autonomous homing simulation experiment of the powered parafoil with insufficient altitude is carried on in a windy environment. The simulation results show that the planned multiphase homing trajectory can fulfill the requirements of fixed-point homing and flare landing; the designed homing controller can overcome the influences of uncertain items of the internal and external disturbances, track the desired homing path more rapidly and steadily, and possesses better control performances than traditional PID controllers.

Dynamic Modeling and Trajectory Tracking Control of Parafoil System in Wind Environments

In this paper, we explore a novel modeling technique to investigate a parafoil flying in wind environments by using computational fluid dynamics. Further, we apply an eight-degree-of-freedom dynamic model of the parafoil in wind environment based on utilizing revised aerodynamic equations. Given that the traditional control methods cannot always tackle trajectory tracking effects properly, we propose an accurate trajectory tracking control method based on active disturbance rejection controller. Semiphysical simulation and airdrop experiments are conducted to evaluate the model as well as the control method. Results demonstrate that the proposed model is effective. Also, active disturbance rejection control outperforms the proportional-integral-derivative (PID) controller regarding the antidisturbance ability and control accuracy.

Modeling and Control of a Powered Parafoil in Wind and Rain Environments

A novel modeling method, based on computational fluid dynamics (CFD) to simulate a parafoil flying in rain and wind environments, is proposed. Then, the dynamic model of the powered parafoil in the complex environment is established on the basis of revised aerodynamic equations. By introducing path-following controllers based on active disturbance rejection control (ADRC), horizontal and longitude trajectory tracking of the powered parafoil in realistic environments are simulated. Results verify the effectiveness of the model and control methods.

Performance Analysis of Flux-Switching Stator Permanent Magnet Motor Based on Linear Active Disturbance Rejection Control

Flux-switching permanent magnet motor (FSPMM) is a new stator permanent magnet brushless motor. It overcomes many shortcomings of the conventional permanent magnet motor having magnets in the rotor and has a well application prospect. The three-phase 12-slots/10-poles FSPMM is used as the control object. On the basis of the working principles, the mathematical models have deduced and the mechanical properties are calculated. The characteristics of the electromagnetic are analysed by setting up the steady and dynamic-state models of the FSPMM. Linear Active Disturbance Rejection Control (LADRC) is designed in the speed loop of the FSPMM to realize the linear control of the nonlinear system. By using the Linear Extended State Observer (LESO), the total disturbances can be estimated and compensated in real time. The performance robustness is verified by the Monte Carlo experiments of the two control strategies, including the LADRC algorithm, and the traditional PI control strategy. The results show that LADRC strategy has a greater capability of disturbance rejecting and stronger performance robustness.

Convergence and stability analysis of active disturbance rejection control for first-order nonlinear dynamic systems

To quantitatively investigate the correlation between parameters, disturbance and stability of the linear active disturbance rejection control (LADRC) technique, this paper provides a perspective of first-order nonlinear dynamic systems, and obtains the stable region of LADRC and reduced-order LADRC according to the Lyapunov function and the Markus–Yamabe theorem, along with mathematical proofs for global stability and asymptotic regulation. To be specific, regardless of whether plant dynamics are exactly known or unknown, the control bandwidth can be chosen arbitrarily from the obtained feasible region as long as the derivative of the disturbance satisfies a Lipschitz condition, or some knowledge of the boundary is available. Moreover, simulations are presented to testify the reliability of the results for different disturbances that are probably known or unknown when designing the extended state observer. The results show the validity and feasibility of this analysis.

A hybrid control approach for powered parafoil combining active disturbance rejection control and unbalanced load compensation

Powered parafoil is a kind of low-speed unmanned air vehicle and is widely used in aerospace applications. However, the wind interference and the unbalanced load on the actuators of its horizontal controller extremely reduce the control effect and the disturbance rejection ability of the trajectory tracking. In order to solve these problems, a hybrid control approach for powered parafoil based on active disturbance rejection control is proposed. In this control approach, distinguished from other existing ones, the horizontal controller consists of the inner and outer loops. The outer loop is applied to accurately control the flight direction and offset the wind disturbance of the whole system. Meanwhile, the inner loop is designed to offer higher control precision and dynamically compensate the unbalanced load on the actuators of the horizontal controller. In order to verify the control approach, the model of the powered parafoil is improved by the model of rudders and flap deflection. Then, the effectiveness of the proposed control method is illustrated by the experiment. The results show that compared with the proportional–integral–derivative controller, the control effect and the anti-disturbance ability are all substantially improved.

Soft landing control of unmanned powered parafoils in unknown wind environments

For autonomous landing powered parafoils, the ability to perform a final flare maneuver against the wind direction can generate a considerable reduction of lateral and longitudinal velocities at impact, enabling a soft landing for a safe delivery of sensible loads. To realize accurate, soft landing in the unknown wind environment, an in-flight wind identification algorithm is first proposed. The wind direction and speed can be obtained online by only using the GPS sampling data based on the recursive least square method. Moreover, the 3D trajectory tracking strategy for the powered parafoil is also established, which is globally asymptotically stable. Furthermore, the lateral trajectory tracking controller and longitudinal altitude controller based on active disturbance rejection control are presented, respectively. Eventually, results from simulations demonstrate that the proposed landing control method can effectively realize accurate soft landing in unknown wind environments with the in-flight wind identification algorithm applied in the trajectory tracking process.

In-flight wind identification and soft landing control for autonomous unmanned powered parafoils

ABSTRACT For autonomous unmanned powered parafoil, the ability to perform a final flare manoeuvre against the wind direction can allow a considerable reduction of horizontal and vertical velocities at impact, enabling a soft landing for a safe delivery of sensible loads; the lack of knowledge about the surface-layer winds will result in messing up terminal flare manoeuvre. Moreover, unknown or erroneous winds can also prevent the parafoil system from reaching the target area. To realize accurate trajectory tracking and terminal soft landing in the unknown wind environment, an efficient in-flight wind identification method merely using Global Positioning System (GPS) data and recursive least square method is proposed to online identify the variable wind information. Furthermore, a novel linear extended state observation filter is proposed to filter the groundspeed of the powered parafoil system calculated by the GPS information to provide a best estimation of the present wind during flight. Simulation experiments and real airdrop tests demonstrate the great ability of this method to in-flight identify the variable wind field, and it can benefit the powered parafoil system to fulfil accurate tracking control and a soft landing in the unknown wind field with high landing accuracy and strong wind-resistance ability.

Accurate calculation of aerodynamic coefficients of parafoil airdrop system based on computational fluid dynamic

Accurate calculation of canopy aerodynamic parameters is a prerequisite for precise modeling of a parafoil airdrop system. This investigation analyses the aerodynamic performance of the canopy in airdrop testing combining the leading-edge incision and the trailing-edge deflection. Aerodynamic parameters of the canopy are obtained using the computational fluid dynamic simulations, and then, the output data are used to estimate the deflection and incision factors. The estimated lift and drag coefficients instead of the traditional parameters based on lifting-line theory are incorporated into the eight degrees of freedom dynamic model of an airdrop system and make some simulations. The effectiveness of the proposed method for calculating aerodynamic coefficients is verified by actual airdrop testing.