Spacecraft robust attitude tracking design: PID control approach

A nonlinear robust controller design method is proposed for the lateral control of heavy vehicles for automated highway systems. In the controller design, the actuator dynamics is explicitly taken into account. A first order pre-filter is introduced to reduce chattering which is inherent in the nonlinear robust controller and to prevent the saturation in the front wheel steering angle and steering system slew rate. A constructive backstepping design technique is utilized in the design of a robust controller for the augmented system. Simulation results are shown.

While linear robust control theory is relatively well understood with many standard techniques for control system analysis and controller design, methods for designing robust nonlinear controllers are relatively undeveloped. This constitutes a significant gap between control theory and practice, as most real processes have significant nonlinearities associated with their startup and shutdown, and often during normal operations. Hence, the development of robust nonlinear controller design methods is widely recognized as one of the most important and challenging open fundamental problems in process control theory. Here, a rigorous approach is developed for designing robust nonlinear controllers using a combination of dynamic nonlinearity inversion and bilinear matrix inequalities.

Performance-guaranteed Robust PID Controller Design for Systems with Unstable Zero

We propose a robust control system which has robustness for disturbance and can deal with a nonlinear system with partially unknown structure by fusing reinforcement learning and robust control theory. First, we solved an optimal control problem without using unknown part of functions of the system, using neural network and the repetition learning of reinforcement learning algorithm. Second, we built the robust reinforcement learning control system which permits uncertainty and has robustness for disturbance by fusing the idea of H infinity control theory with above system.

A new robust linear controller design method is considered. The robust controller consists of two parts: 1) a conventional model matching feedback and 2) a new linear "modeling error compensator" which exploits a modeling error signal (based on the plant input and output signals) to enhance both the stability and performance robustness. For linear SISO systems of known order without right half plane zeros and arbitrary variation of transfer function coefficients within a given bounded set, a modeling error compensator can be designed which guarantees robust stability and an arbitrary small H/sub /spl infin//-norm of the tracking error transfer function over a given frequency band. Examples show that modeling error compensation can also be used to improve the robustness for systems with right half plane zeros, and that the transient response using model error compensation is better than that using model reference adaptive control.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Robust STATCOM voltage controller design using loop-shaping technique

Hybrid Passive/Active Control Performance in Buildings Using Robust Control Design Approaches

Robust Anticipative Controller Design with Application to A High Dynamic Engine Testbed

This paper presents a robust tracking controller design method for the track-following system of an optical recording device. A tracking loop gain adjustment algorithm is introduced to accurately estimate the tracking vibration quantity in spite of the uncertainties of the tracking actuator. A minimum tracking open-loop gain is calculated by the estimated tracking vibration quantity and a tolerable limit of tracking error. A robust tracking controller is designed by considering a robust <TEX>$H_\infty$</TEX> control problem with the weighting function of a slightly larger gain than the minimum tracking open-loop gain. The proposed controller design method is applied to the track-following system of an optical recording device and is evaluated through the experimental result.

Robust Multivariable Control of Nuclear Power Plant

We discuss the fragility of controllers against small inaccuracies of controller parameters. A useful way to gain insight into controller fragility is to consider the fragility of poles and zeros. Certain controller design methods and controller parametrizations are especially vulnerable to fragility problems. It is hoped that the controversy and debate around the claimed fragility of designs obtained by modern robust and optimal control theories calls attention to the relevance of the work on fixed wordlength effects in controller implementation. A case study on a paper machine headbox control problem is included to illustrate that if a good robust control design method is used, together with a reasonable controller realization (parametrization), it should be possible to combat controller fragility in a fairly satisfactory, although indirect, manner. However, it would certainly be interesting to study whether controller fragility could be directly addressed within some generalized robust control design theory.

Robust velocity and height control problem is dealt with for hypersonic vehicles subject to highly nonlinearity and uncertainties. The linear robust controller design for nonlinear systems suffers from the conservation problem, because the nonlinear dynamics are considered as uncertainties. In this paper, a feedback linearization controller is firstly applied to achieve the dynamic decoupling of the velocity and height channels. Then, robust controllers are designed for each channel to restrain the effects of the parametric uncertainties, external disturbances, and nonlinear dynamics, which cannot be counteracted accurately by the feedback linearization technique. This method can guarantee the robust stability and robust tracking properties of the closed-loop control system, while the conservation of the robust controller design can be reduced because the nonlinear information of dynamic system is used. Simulation comparisons are given to show the advantages of the proposed robust nonlinear control method.

A robust adaptive backstepping controller design method is proposed for a nonlinear system with uncertainty and unknown parameters based on the CMAC neural network. The CMAC neural network was used not only to approach the arbitrary model uncertainties but also to eliminate the bad effects of the uncertainties with robust terms in the controller and virtual controllers. Novel update and control laws are proposed to guarantee that all the signals in the closed-loop control system are uniformly ultimately bounded in a Lyapunov sense. Simulation experimental showed the tracking control of the nonlinear system is achieved and this method is effectual.

The paper derives a robust networked controller design method for systems with saturation where the delay is large and uncertain, as in one‐directional data flow‐control. A classical linearH∞criterion is first formulated in terms of the sensitivity and complementary sensitivity functions. A new asymptotic constraint is then derived, which specifies the minimum amount of low frequency gain that is needed in the sensitivity function to conclude on non‐linear closed loop‐stability using the Popov criterion. This result guides the selection of the design criterion, thereby adjusting the linear controller design for better handling of delay and saturation. The controller design method then uses gridding to pre‐compute a subset of thestability region. Based on the pre‐computed region, a robust‐stable controller can be selected. Alternatively, an adaptive controller could recompute‐stable controllers on‐line using the pre‐computed region. Simulations show that the controller meets the specified stability and performance requirements.

A new tuning method for proportional-integral-derivative (PID) controller design is proposed for a class of unknown, stable, and minimum phase plants. We are able to design a PID controller to ensure that the phase Bode plot is flat, i.e., the phase derivative w.r.t. the frequency is zero, at a given frequency called the "tangent frequency" so that the closed-loop system is robust to gain variations and the step responses exhibit an iso-damping property. At the "tangent frequency," the Nyquist curve tangentially touches the sensitivity circle. Several relay feedback tests are used to identify the plant gain and phase at the tangent frequency in an iterative way. The identified plant gain and phase at the desired tangent frequency are used to estimate the derivatives of amplitude and phase of the plant with respect to frequency at the same frequency point by Bode's integral relationship. Then, these derivatives are used to design a PID controller for slope adjustment of the Nyquist plot to achieve the robustness of the system to gain variations. No plant model is assumed during the PID controller design. Only several relay tests are needed. Simulation examples illustrate the effectiveness and the simplicity of the proposed method for robust PID controller design with an iso-damping property.