In this paper, a method based on the indirect solution of optimal control problem is presented to specify the optimal trajectory of spatially suspended cable robot in Point to Point motion with considering the counterweights. In fact, an optimal trajectory planning problem is outlined in which states, controls and the values of counterweights must be calculated simultaneously in order to minimize the given performance index. The value of the pulley torques is considered forthe performance index (objective function).Using the fundamental theorem of a calculus of variations, the necessary conditions for optimality of cable robotare achieved. For the three-cable spatial robot, a two-Point boundary value problem is achieved which can be solved with bvp4c command in MATLAB. The obtained results show that optimal Balancing in comparison with the unBalancing method can reduce the performance index significantly.

The present work studies a model predictive controlled two-and three-level active front-end rectifier system for supplying LORAN transmitter system. Up to now, the LORAN transmitters have been supplied by only diode rectifiers, which inject sever harmonics into the AC network and induce a very low input power factor when supplying pulsed loads. Therefore, an MPC-controlled active rectifier system with three level Neutral Point clamped topology is proposed to attenuate the input current harmonics and improve the input power factor. Compared with the conventional methods (e. g. voltage oriented control (VOC), direct power control (DPC)), the proposed control method provides such advantages as improved power quality indices, reduced switching frequency, and simplicity for controlling different indices just by changing the weighting factors of the relevant cost function. The results of comparing these thee methods demonstrate that the MPC method could not only give a power factor close to unity and negligible harmonic distortion, but also very lower switching frequency, as compared to the two other methods. Using the MPC, VOC, and DPC control methods, the switching frequencies for a typical load were found to be 11. 3, 74. 5, and 60 kHz, respectively. Moreover, the intuitive logic and easy implementation of the MPC method, compared to the two other ones, besides achieving an improved operating Point with a lower cost, represent the other important advantages of the MPC method.

Grid-tied Neutral-Point-Clamped (NPC) inverters have been widely used in various applications recently. A superior control method is required to achieve the desired performance of a grid-connected NPC inverter. Accordingly, a second-order sliding mode control (SOSMC) method, which is designed in the stationary frame, is utilized for achieving this aim in this paper. The super-twisting second-order sliding mode control is used for solving the chattering problem of conventional first-order sliding mode control (FOSMC). In comparison to control methods which are applied in rotation frame, this method is not required transformation from rotating frame to a-b-c frame and vice versa and decoupling of d and q components. The Lyapunov stability analysis is used for designing of this controller. The performance of proposed method is evaluated by simulation results implemented in MATLAB/Simulink software. The performance of the SOSMC is also compared with FOSMC. The results show that the incorporation of SOSMC can improve current reference tracking of the NPC inverter in different scenarios.

This paper presents a finite control set model predictive control for a four-level nested Neutral Point clamped converter (4L-NNPC) in electric drive application. Controlling the voltage of the flying capacitors (FCs) in this converter, especially at low output frequency, is challenging due to the lack of complete switching states to control the FCs voltages. In the proposed method, the main control objectives of the electrical motor and converter, i.e., the control of the torque, flux, and voltage of the FCs, have been formulated. A modified weighting factor for FC voltage objective in the cost function is introduced, which provides the full possibility of controlling voltage fluctuations of FCs, especially in low-frequency operation. The proposed control method, in addition to controlling the electric motor's required objectives, can control the voltage of the FCs of the converter in the entire operating frequency range. The performance of the proposed method has been simulated and verified on a 4L-NNPC converter using a 1500 HP, 4160 V electric drive in the MATLAB/Simulink software environment.

This article presents the open switch fault detection and diagnosis of Neutral Point clamped inverters using neural networks. The Neutral Point clamped inverter consist of four power semiconductor switches with two clamp diodes in each phase. As the number of power semiconductor switches in the inverter increases, the probability of fault occurrence significantly increases. Therefore, for ensuring uninterrupted operation and preventing additional damage during faults, rapid fault diagnosis is essential for the fault tolerant systems. In this study, a neural network based system is developed for the detection and diagnosis of open switch faults in one or two power semiconductor switches in Neutral Point clamped inverter. The proposed method relies on measuring the inverter output currents and calculating their average values, which are then used for training the neural network. The proposed system covers open switch fault diagnosis for one or two switches. The mentioned system was simulated in the MATLAB/SIMULINK environment, and the result demonstrate accuracy and rapid fault diagnosis for semiconductor power switches within a fundamental cycle.

In this paper a new topology of three-level inverters with ten-switch is proposed to control low voltage three phase induction motor. Ten-switch inverter is a reduced-switch-count three level inverter which compared to conventional topologies such as NPC, CHB and flying capacitor has lower count of semiconductor switches. Thus, it enjoys from lower cost, lower volume and lower weight. In this paper, a direct torque control (DTC) scheme based on switching table is developed to control a ten switch inverter. Simulation results of controlling induction motor fed by a conventional two-level inverter, NPC and proposed 10 switch inverter are presented and they are compared together in different aspects. Results confirm the effectiveness of the proposed topology and its control method.

Background and Objectives: Due to the high torque ripple and stator current harmonics in direct torque control using a two-level inverter, the use of multi-level inverters has become common to reduce these two factors. Among the multilevel inverters, the Neutral-Point-Clamped Inverter has been given more attention in the industry due to its advantages. This inverter has 27 voltage vectors by which torque and flux are controlled. In order to reduce torque ripple and current harmonic as much as possible, methods such as space vector modulation methods or the use of multi-level inverters with higher levels have been considered. But the main drawback of these methods is the increase of complexity and cost.Methods: In this article, virtual voltage vectors are used to increase the number of hysteresis controller levels. These vectors are obtained from the sum of two voltage vectors. In this way, we will have 12 voltage vectors in addition to the diode clamped inverter’s voltage vectors. Therefore, we can increase the number of torque hysteresis levels from 7 levels to 11 levels.Results: Considering that the proposed method uses virtual vectors and voltage vectors, it does not increase the cost and computational complexity. Also, one of the requirements of using this method is the use of fixed switching frequency, which solves the variable switching frequency problem of conventional methods. Therefore, the proposed control reaches an overall optimization.Conclusion: To verify the feasibility of the proposed method and compare it with the conventional method, both of these methods are simulated in the MATLAB /Simulink environment and the simulation results represent the efficiency of the proposed control method. This method achieves less torque ripple and harmonic current without increasing the cost and computational complexity.

Assembly Line production is one of the widely used basic principles in production system. The problem of Assembly Line Balancing deals with the distribution of activities among the workstations so that there will be maximum utilization of human resources and facilities without disturbing the work sequence. Research works reported in the literature mainly deals with minimization of idle time i.e. Balancing, subject to precedence constraints. Lack of uniqueness in their optimum solutions has led to the present work where minimization of both Balancing loss and system loss has been envisaged under the usual precedence constraints. The researchers suggest a generic approach for designing of an assembly line where, with a given number of workstations, one can efficiently arrive at the desired solution under different methods of search like simulation, heuristic etc. Thus, the main aim of this paper is to redefine the objective of the Assembly Line Balancing Problem and sequentially handle Balancing Loss and System Loss. A numerical example has been added to demonstrate the generic nature of the researcher's approach and improvement in the solution set when compared with different standard line Balancing methods available so far in the literature.