Fast tool servos (FTS) for single point diamond turning are widely employed for machine optical free-form surfaces. A FTS with a large stroke and a high bandwidth can increase the efficiency of a machine and complexity of a work-piece. In this paper, a FTS driven by a Maxwell electromagnetic actuator is developed to obtain a relatively large stroke and high bandwidth. In this study, a multi-objective optimization model is proposed based on the whole system by considering electromagnetic driving principles, kinematic model, and mechanical model. The proposed optimization model can be applied to solve the parameters of electromagnetic actuators with diverse application requirements. A sequential quadratic programming (SQP) algorithm is implemented to solve the problem. The optimization results are verified through both finite element analysis and experiments. The optimized FTS can produce 49.55 µm of full stroke with a frequency response of 3.2 kHz.
In this paper, an analysis of a hybrid two-population genetic algorithm (H2PGA) for the job shop scheduling problem is presented. H2PGA is composed of two populations that constitute of similar fit chromosomes. These two branches implement genetic operation separately using different evolutionary strategy and exchange excellent chromosomes using migration strategy which is acquired by experiments. Improved adaptive genetic algorithm (IAGA) and simulated annealing genetic algorithm (SAGA) are applied in two branches respectively. By integrating the advantages of two techniques, this algorithm has comparatively solved the two major problems with genetic algorithm which are low convergence velocity and potentially to be plunged into local optimum. Experimental results show that the H2PGA outperforms the other three methods for it has higher convergence velocity and higher efficiency.
In combustion of a circulating fluidized bed, primary air plays a key role in keeping materials fluidized and regulating bed temperature. This report provides a design of reference governor for primary air fans to amend their control commands. That will improve the combustion efficiency via regulating primary air flow rate timely according to the changes of coal feed flow rate and bed temperature. To deal with the large inertia and slow response feature of primary air fans, a rule-based control method was used to design the reference governor. Based on the experiences of technical experts and operation data analysis, an expert rules system with wide coverage range was developed, which composed of the logical relationships between the coal feed flow rate, bed temperature and the primary air flow rate in various operation conditions. Test results show that designed reference governor can improve the control performance of primary air flow rate obviously.
This study investigated a mathematical model which was built for a simulation loading system based on secondary regulation. Because the loading system was complicated in structure and some other factors, the control performance was not ideal. Therefore, a dynamic robust compensating controller was designed for the system. The robust compensator could improve the control system by adding the return-to-zero factor and low pass filter on the basis of PID control. This study used MATLAB to simulate the general PID control and the robust compensation control. The results of simulation showed that when the equivalent rotary inertia and damping coefficient changed, the control performance decreased. When using the dynamic robust compensation control, the influences caused by parameter variations were reduced greatly, the system robustness and control accuracy are improved.
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