Winding system is a production system commonly used in industry. Its control goal is to achieve constant tension control of the system by controlling motor torque, and to cope with various external disturbances in industrial environment. The Fractional Order PID(FOPID) controller is well known for its simplicity with better tuning flexibility as well as robustness with respect to disturbances b1b2. Thus, this paper proposes a control strategy based on FOPID to achieve the control objectives. First, a linear approximation model is established for the constant tension control system. Then, a FOPID controller is designed based on the model. Four non-linear constraints and an objective function of the controller are proposed based on the frequency domain. Five tunable parameters of FOPID are determined by combining genetic algorithm(GA) with FMINCON non-linear optimization. Finally, through the simulation of MATLAB, the performance of the controller is compared with the classic integer order PID. The results show that the FOPID controller has better control characteristics and robustness.

The control aim of parabolic distributed solar collector (PDSC) is to make the heat generated follow the expected reference value when the solar radiation varies unevenly. This article proposes a control strategy based on fractional-order PID (FOPID) to achieve control objectives. Four non-linear constraints and an objective function of the controller are proposed based on the frequency domain. Most studies regard the constraint measuring stability as the objective function, while the real difficulty for the control system design should be how to obtain better robustness. Therefore, this article determines five parameters of FOPID by selecting the constraint measuring robustness as the objective function based on Particle swarm optimization (PSO). Besides, three non-parametric statistical tests, including Friedman ranks, Friedman Aligned ranks and Quade ranks, have been adopted to compare PSO with other evolutionary algorithms to demonstrate its advantage. Finally, the superiority of proposed strategy to previous design is demonstrated by the simulation studies on a PDSC in terms of the control performance of step response, static gain variation, time constant variation, high frequency noise and output interference.

The passivity-based control (PBC) is a new direction of nonlinear control, but the method is basically a qualitative method. A quantifiable design method in combination with PBC is provided in this paper. To solve the partial differential equation (PDE) for PBC, the nonlinear system must first be transformed into a Hamiltonian model. The PDE for the Hamiltonian system is then quantifiably solved with an electromagnetic levitation example. The resulting control law is presented and discussed. The proposed method provides a practical design tool for nonlinear control.

The coupling between variables in the multi-input multi-output (MIMO) systems brings difficulties to the design of the controller. Aiming at this problem, this paper combines the particle swarm optimization (PSO) with the coefficient diagram method (CDM) and proposes a robust controller design strategy for the MIMO systems. The decoupling problem is transformed into a compensator parameter optimization problem, and PSO optimizes the compensator parameters to reduce the coupling effect in the MIMO systems. For the MIMO system with measurement noise, the effectiveness of CDM in processing measurement noise is analyzed. This paper gives the control design steps of the MIMO systems. Finally, simulation experiments of four typical MIMO systems demonstrate the effectiveness of the proposed method.

This paper introduces a planar two-degree of freedom (2-DoF) compliant rotational hinge which can achieve rotation in-plane and out-of-plane to promote the flexibility of Lamina Emergent Mechanisms (LEMs). The theory models of rotational equivalent stiffness around y-axis and z-axis for the planar 2-DoF compliant rotational hinge were inferred respectively using appropriate spring models. Then a finite element analysis was used to prove the reliability of the theoretical models. Finally, an optimal model was built to improve the rotational performance of planar 2-DoF compliant rotational hinge, and all the structure dimensions were optimized by particle swarm optimization algorithm with penalty function. The optimization results show that the rotational performance was improved observably with the rotational stiffness around y-axis and z-axis were reduced by 80.5% and 89.4% separately, which also was in line with expectations.