Journal of Control
Year:2015 | Volume:9 | Issue:1|Papers Count:7

Advanced traffic control strategies are designed to improve the safety issue, as well as these strategies consider the dynamic of vehicles in traffic system. One important issue in the field of automatic traffic control in platoons is the string stability. In this paper, a robust centralized traffic control system, for a platoon of the same vehicles based on the linear matrix inequalities (LMIs), is designed. This control system satisfies the robust stability and robust string stability conditions. Simulation results are presented to show the effectiveness of the control design methodology.

This paper presents a new approach for fault tolerant control system (FTCs) design based on robust nonlinear model predictive control (NMPC) for multivariable affine systems. The proposed FTCs uses an estimation scheme that is based on adaptive extended kalman filter (AEKF) for the state estimation of plant and loss of effectiveness factors of actuators. A supervisor module also uses the fault modeling and correction of plant model per sampling time to accommodate bias and loss of effectiveness of actuators. In addition by feedback compensation in NMPC, the proposed controller is robust through plant uncertainties. The most important advantage of the proposed approach is its ability to deal with the constraints and simultaneous fault in actuators and it is practical. Simulation results of the proposed method on automotive engine show the effectiveness of the proposed method.

In this paper, we investigate the design method for interval type-2 (IT2) fuzzy controller for nonlinear systems along with uncertainty parameters. In order to analyze the stability and synthesis the control methods conveniently, an IT2 T-S fuzzy model is applied through representing the dynamic of nonlinear systems. Uncertainty parameters are captured by IT2 membership function characterized by the lower and upper membership functions. In this paper, for IT2 fuzzy controller, the membership functions and number of rules can be freely chosen different from the IT2 T-S fuzzy model. This method is known Non- Parallel Distributed Compensation. To reduce the conservativeness of stability analysis, a fuzzy Lyapunov function candidate is applied. The stability conditions in term of linear matrix inequalities (LMI) are obtained.

In this article, a nonlinear controller is designed for a pumped storage hydropower (PSH) based on doubly fed induction machine (DFIM) in the motor mode. The main controller of a variable speed PSH consists of three separate parts: motor side converter, grid side converter and pump-turbine guide vanes which are designed via stator voltage oriented vector control. Using the power electronics in DFIM-based application can be made the fault ride through issues. In industrial applications, the variable speed PSH uses a hardware protection, i.e. crowbar or dc link brake chopper, in order to maintain the connectivity to the grid during a fault. In this article, however, the motor side controller is modified by an effective input signal to be added to decoupled d-axis inner loop. It is shown that the proposed controller not only eliminates the need of conventional protection, but also improves the transient responses. Furthermore, it is demonstrated using realtime simulation in Matlab/Simulink that the credibility of the proposed controller.

The most important property of sliding mode control (SMC) is invariant against matched uncertainties, which is due to the using of Sign function and this Sign function produces chattering. Moreover, SMC is not invariant with respect to the mismatched uncertainties, which is its other problem. In this paper to solve these two problems, using of multiple surface dynamic sliding mode control (DSMC) is proposed. In DSMC the chattering is removed due to the integrator where is placed before the input control signal of the plant. However, in DSMC the augmented system (the system plus the integrator) is one dimension bigger than the actual system and then, the plant model should be completely known. To solve this problem, an observer is proposed called integral-chain observer or ICO. To counteract with mismatched uncertainty, any system dynamics are considered as a distinct nonlinear system and multiple sliding surfaces is defined. One of the advantages of the proposed approach is the upper bound of the uncertainty not used in DSMC and ICO, which is important in practical implementation. Then, a design procedure is described and simulation result is presented to demonstrate the approach.

In this paper we investigate generating an optimal running gait for the planar model of ATRIAS bipedal robot. ATRIAS is a robotic prototype implemented in Oregon State University with the aim of high speed running. Gait generation for ATRIAS has been done based on SLIP model. Although this passive model is a good base for gait generation, it does not necessarily yield to the best energy efficient solution. So, in this paper via the gradient based method starting from an initial point given by SLIP based control, we search for an optimal pattern for the running gait that minimizes cost of transport (COT) during one complete step. Equations of motion for each continuous time phases, called stance and flight, and models for take-off and touch-down events are derived. Then by parameterization of motors torque profiles using polynomials and solving the direct dynamic model, optimization problem is solved to minimize COT. The optimization is repeated three times by performing the parameterization in terms of polynomials of degrees 3, 4, and 5, to obtain the most efficient torque profiles. The results indicate that for all three shapes of polynomials COT is reduced compared with SLIP based running gait. Moreover, the minimal COT is achieved by torque profiles of degree 4.