Papers by Keyword: Disturbance Rejection

Abstract: This paper describes a comparative performance analysis of sliding mode and fuzzy sliding mode controllers for climate control application of a greenhouse flower garden. Various internal and external climate related factors affect the overall growth and health of flowers that needs robust controllers to control the humidity and temperature of the greenhouse flower garden. Review of related works show that for non-linear systems, sliding mode controllers can provide robust performance even though chattering is a major drawback of the controller. A number of approaches are used to solve the chattering problem of sliding mode controllers such as hybrid uses of other controllers along with sliding mode controller. In this paper, sliding mode controller and fuzzy sliding mode controllers are designed and implemented for the specified control application based on the linearized and decoupled model of the system. The performance evaluation has been done for the control problems of reference tracking and disturbance rejection with time domain performance measures of percentage overshoot, settling time and rise time. Accordingly, the overall system has been implemented in MATLAB/Simulink and the simulations for the control problems have been done. Thus, FSMC has got rise time of 5.89min, 10.59min settling time and almost negligible percentage overshoot for indoor temperature at 27°C and humidity at 22g/m³. And for humidity control, the FSMC has got 5.44min settling time and nearly zero percentage overshoot for set point tracking problem. For the disturbance of solar radiation, decrease in outside temperature and fixed set point of 27°C and humidity of 22g/m³, FSMC outperforms SMC. In summary, both quantitative and qualitative results analysis results reveal that fuzzy sliding mode controller (FSMC) outperforms sliding mode controller (SMC) for the indoor temperature and humidity control tasks of both set point tracking and disturbance rejection problems.

Abstract: This paper presents a method for the active noise and vibration control (ANC/AVC) of harmonically related nonstationary disturbances using varying-sampling-time linear parameter-varying (LPV) controller. The frequencies are assumed to be known and varying within given ranges and they are multiples of one fundamental frequency.

Abstract: In this paper, a combing method based on the linear extended state observer (LESO) and the LQR controller is presented. The LESO is applied to estimate the total disturbance of the space station, and an effective disturbance compensation strategy is proposed for the attitude control and moment management. The simulation results illustrate this method is effective

Abstract: The disturbance rejection problem for discrete-time linear systems with both state delay and control delay is considered. Using a model transformation, the time-delay system is transformed into a nondelayed system. The disturbance rejection control law is obtained by solving its optimal regulation problem.

Abstract: This paper proposes a novel fuel cell system design by integrating both methods of Ziegler-Nichols-based PID control and the intelligent fuzzy control, thus the relative stability and disturbance rejection properties can be reserved. This new method is not proposed before for fuel cell control system design. By using PID method for the normal case of fuel cell current requirement, the overshoot of the temperature is 45%, the temperature rise and the settling times are 0.65 sec and 2 sec, respectively. However, by using intelligent fuzzy Ziegler-Nichols-based PID controller design, the overshoot of the temperature is 12%, the temperature rise and the settling times are 0.7 sec and 1 sec, respectively. Thus the proposed method is better. Moreover, this paper also takes the system disturbance variation effect into consideration, e.g. the current requirement is increased by 100% for climbing a slope or speed-up conditions; note a large 60% temperature overshoot is produced by using Ziegler-Nichols based PID controller. But the overshoot is only 20% by using the intelligent fuzzy Ziegler-Nichols-based PID controller. Thus the proposed system is more robust.

Abstract: In order to suppress the impact of the friction torque and the magnetic levitation high-speed rotor system on the stability of gimbal servo system output angular rate, a self-adaption compensation method with no modeling for disturbance torque is presented. The interference suppressor calculates the disturbance compensation based on the torque motor current and the angular rate measured real-time by the current detection circuit and the frame angular detection circuit in the gimbal servo system, then feedbacks to the frame servo system controller to regulating the torque motor output current. 500Hz and 50Hz sinusoidal disturbance torque are introduced into the system to test the role of the interference suppressor. The result proves the interference suppressor has the same significant inhibition of effect for disturbance torque of different frequencies by MATLAB simulating framework output angular rate waveform.

Abstract: A new soft-braking strategy for modern Wind Turbines (WTs) is proposed. The braking torque is directly controlled by regulating the caliper’s hydraulic pressure via a controllable pressure valve, subject to some thermal constraints about mechanic braking units. The proposed control strategy consists of a pressure controller, a braking controller and an optimization algorithm for generating a braking torque reference. The modeling issues and some of these design/developments based on a lab-sized setup are discussed. Comparing with the existing WT braking solutions, either through an on/off control, or through some soft-braking mechanism which mainly employs a kind of generator-shaft speed control, the proposed approach can control the brake-induced mechanic stress to the transmission system in a more effective manner, and meanwhile, the thermal stress to the braking units is also explicitly cooperated into this design.

Abstract: A high reliability of Traffic Memory(TM) working condition is of vital importance to information transfer in MVB. In order to avoid bus traffic overflows, the minimum possible time intervals or loading ratios of TM for a given number of ports were calculated. The longer supervision period it had, the more number of docks could be supervised. The number of docks supervised, during supervision intervals, was submitted to Normal distribution ( Ν(μ,σ²)). From the possibility distribution function it could σfind maximum possibility of the number of docks in working. From the disturbance rejection test of the fixed factor σ , a reasonable setting of sink-time supervision interval could be made to guarantee a high reliability for TM working condition.

Abstract: A class of multi-variable decoupling control algorithm for aero-engines is mainly studied In this paper. Firstly, the mechanism of ADRC decoupling control algorithm is elaborated and discussed in detail. Secondly, an ADRC controller for some turbofan engine's nonlinear component-level model is designed to solve two-loop control problem according to the basic principle of ADRC. Compared with ALQR (Augmented Linear Quadratic Regulator) controller in full flight envelope, enough numerical verification tests about ADRC controller have carried out. Finally, simulation results show that the closed-loop system based on the ADRC decoupling controller has better disturbance rejection capability than the ones based on ALQR controller.

Abstract: An asymmetric PI (aPI) controller based on a control algorithm, which is the modification of the PI control method, has been suggested. The principal characteristic feature of the aPI controller is that different values of proportional and integral constants are used at positive and at negative errors. Contrary to the classical PI controller, the proposed controller allows us to improve the positive disturbance rejection of control systems without sacrificing the unit step response dynamics. Results of the investigation of the concrete control systems based on the aPI controller are also presented. Using the dynamic system simulation program Simulink performed the investigation.