Evaluation and optimization of a hybrid wave energy converter using excited motion response in two degrees of freedom

As waves in China seas are not high,a wave energy converter consisting of a coaxial annular buoy and a cylindrical buoy that extracts wave energy using two generators through the relative heave motion between the buoys and the pitch motion of the cylinder could be a more efficient choice.A dynamic model considering constraints and assuming linear power take-off is established to evaluate the power performance of the device.The influences of two key factors,the diameter of the annular buoy and the power take-off stiffness of the pitching generator,and their couplings on the power performance are analyzed.The power of the pitching generator accounts for a major proportion of the total power.An increase in the annular buoy diameter increases the power of the heaving generator while greatly decreases the power of the pitching generator.An increase in the power take-off stiffness of the pitching generator greatly decreases its power while has little influence on the power of the heaving generator.These two factors also influence the peak period of the total power.Based on the findings and practical limitations,an optimization strategy is proposed.Further,the device is optimized based on a real wave environment in Shandong Province,China.

Modified Two-Degrees-of-Freedom Internal Model Control for Non-Square Systems with Multiple Time Delays

A modified two-degrees-of-freedom( M-TDOF) internal model control( IMC) method is proposed for non-square systems with multiple time delays and right-half-plane( RHP) zeros. In this method,pseudo-inverse is introduced to design the internal model controller,and a desired closed-loop transfer function is designed to eliminate the unrealizable factors of the derived controller. In addition,set-point tracking and load-disturbance rejection of each process are separately controlled by two controllers. The simulation results show that in addition to high decoupling performance and robustness,the proposed control method also effectively improves loaddisturbance rejection and simultaneously optimizes the input tracking performance and disturbance rejection performance by selecting the parameters of controllers. Furthermore,the higher tolerance of model mismatch is achieved in this paper.

Temperature Control Based on Fuzzy Logic Two-degree-of-freedom Smith Internal Model

According to the characteristics of the large time delay,nonlinearity and the great inertia of temperature control system in biomass pyrolysis reactor,a two-degree-of-freedom Smith internal model controller based on fuzzy control is proposed.Firstly,the mathematical model of the temperature control system is established by using the step response method,and then the two-degree-of-freedom Smith internal model controller is designed,and the good tracking performance and disturbance suppression performance can be obtained by designing the set value tracking controller and interference rejection capability.Secondly,the fuzzy control algorithm is used to realize the on-line tuning of the control parameters of the two-degree-of-freedom Smith internal model algorithm.The simulation results show that,compared with the traditional internal model control,fuzzy internal model PID control and two-degree-of-freedom Smith internal model control,the algorithm proposed in this paper improves the influence of lag time on the control system,realizes the separation control of set point tracking and anti-jamming performance and the self-tuning of control parameters,and improves the control performance of the system.