Shengjun Wen

Operator-based robust nonlinear control and fault detection for a Peltier actuated thermal process

Abstract In this paper, operator-based robust nonlinear control design scheme and fault detection technique using robust right coprime factorization approach are considered for a Peltier actuated thermal process. The Peltier actuated thermal process is a typical nonlinear control affine system, where the process temperature depends not only on input current, but also on the square of the input current. In addition, the real system is likely to contain a fault signal owing to various factors. As a result, it is difficult to stabilize the control system and to achieve high accurate control performance, and to detect the fault signal to guarantee the engineering safety when a fault occurs. In this paper, for pursuing robust stability and tracking performance of the nonlinear closed-loop control system, a design scheme of operator-based robust tracking control system is proposed by using robust right coprime factorization approach. Then, for the tracking operator control system, a fault detection design technique based on robust right coprime factorization approach is also investigated. Finally, simulation and experimental results are given to confirm the effectiveness of the proposed method.

Operator-Based Robust Nonlinear Control for a Peltier Actuated Process:

Recently, Peltier device has attracted much attention in cooling process industry. Peltier device is a kind of device with thermoelectric effect which contains three effects such as Peltier effect, Seebeck effect and Thomson effect1, 2. It can be used to cool or heat by Peltier effect and generate electric power by Seebeck effect. Thomson effect relates the rate of generation of reversible heat inside a homogeneous conductor with a temperature gradient23. Due to the Peltier effect, one side of Peltier device is endothermic and another side is radiation when an electric current is applied to it, and the hot side and cold side reverse when opposite current is applied22, 23. Because heating can be achieved more easily and economically by many other methods, Peltier devices are mostly used for cooling. Peltier cooler uses the Peltier effect to create a temperature difference between the two sides of the device. So, it is an interesting consequence that the Peltier effect is used to make a cooler. Due to compact size, not generating vibration noises and freon gas, the Peltier devices are widely used in many applications3, 4, 23. For example in the past years refrigerators used fluorocarbon generally. However, such refrigerators are prohibited gradually because it leads the disruption of ozone layers and affects the climatic change. So the Peltier effect is considered to create the refrigerator. Peltier devices are also commonly used in camping and portable coolers and for cooling electronic components and small instruments22. Peltier coolers can be used to cool computer components to keep temperatures within design limits without the noise of a fan, or to maintain stable functioning when overclocking23. Moreover, there are still some application products including some small wine coolers, some icing devices for medical treatment and so on. In this paper, we focus on the control aspects of a Peltier-based aluminum plate thermal process. Linear PID controllers or switching PID controllers are commonly used in Peltier-based thermal process due to their simplicity in both design and implementation24, 25. However, Peltier cooling performance is a function of ambient temperature, hot and cold side heat exchanger (heat sink) performance, thermal load, Peltier module geometry and Peltier electrical parameters24. Therefore, in general, the Peltier actuated process is a nonlinear control affine system. The output temperature depends not only on the current, but also on square of the current. For the complex nonlinear, it is difficult to achieve high control accuracy (±0.2°C) by using the mentioned PID controller designs, which is required in some applications such as laser frequency elements. Conventional nonlinear controller design techniques cannot also be applied since the dynamics model does not belong to the typical nonlinear control affine form3, 25. To resolve this problem, a robust nonlinear control technology is presented for an aluminum plate thermal process with the Peltier device by using operator-based robust right coprime factorization approach in this paper. Operator theory is an advanced control theory based on an idea that a signal in the input space is mapped to the output space and some researches in regards to the theory have been conducted5, 6, 11, 12. The relationship between the robustness of the right coprime factorization and the robust stability of the perturbed nonlinear system is shown by Chen and Han7, 14. Based on the design scheme a robust tracking control system is proposed by Deng et al. 10, 13, 18 and the perturbed signal does not affect the system output. So, the operatorbased control method can be applied to a broader class of nonlinear systems with perturbations. Furthermore, a method to control unstable systems with input constraints is given in ref 15, 17, 19 where the controlled system with the input constraints satisfies robust right coprime factorization. The advantage of the operatorbased control is that the control design is relatively simple because bounded input and bounded output stability is guaranteed21, 26. Based on the operator theory, nonlinear controller for the aluminum plate thermal process with Peltier device is designed by using robust right coprime factorization concept. That is, to ensure the robust stability, robust controller is considered and operator-based tracking filter is also designed to obtain the desired output tracking performance. As a result the designed control system is to ensure the robust stability and pursue the perfect output tracking performance. The effectiveness of the designed system is shown by the simulation and experiment. The contents of this paper are written as follows. Firstly, system architecture and function for Peltier actuated process is given. Then modelling of the thermal process is shown. Next, an operator-based robust stabilization controller is designed by robust right coprime factorization method. Meanwhile an operator-based tracking control is considered to satisfy tracking performance. Further, simulation and experimental results are given to confirm the proposed method. Finally we draw the conclusion on our current and show future work.

Operator-based robust nonlinear control and its realization for a multi-tank process by using a distributed control system

In this paper, a robust nonlinear control design method using an operator-based robust right coprime factorization approach and its realization based on a distributed control system (DCS) device are considered for a multi-tank process. In detail, for the multi-tank process, consisting of a water-level process and a water-flow process, theoretical models are developed according to the Bernoulli theorem. Based on the obtained models, a robust nonlinear feedback control design is presented by using robust right coprime factorization for the multi-tank process. Further, from a large-scale industrial application viewpoint, the realization of the designed operator-based robust right coprime factorization controllers is considered by using a DCS device. Because there are some nonlinear functions in the designed controllers which cannot be realized straightforwardly in the DCS device such that the designed controllers need to be realized approximately. That is, there exist some parasitic terms for the approximated realization of the controllers in the real system. As a result, the parasitic terms and processes’ unknown uncertainties should be considered simultaneously. In this paper, a robust condition is derived to guarantee robust stability of the nonlinear feedback control system with the parasitic terms and the uncertainties. Moreover, tracking controller design problem for the multi-tank process is discussed. Finally, by using a DCS device (CENTUM CS3000), experimental results are given to confirm the effectiveness of the proposed design scheme.

Operator-based robust non-linear control for gantry crane system with soft measurement of swing angle

In this paper, a robust non-linear control scheme is proposed for a gantry crane system with estimation of swing angle by using operator-based robust right coprime factorisation approach. By analysing properties of the crane system, it shows that displacement distance and swing angle are the two main goals. But, there exists only one input force. Also, in real gantry crane system, it is difficult to measure the swing angle. As a result, real-time estimation of the swing angle is presented by using data-based SVM model, where a generalised Gaussian function is adopted as the kernel function. The difference between the estimation and real value leads some uncertainties. Then, operator-based robust right coprime factorisation approach is presented for the non-linear system with uncertainties. Meanwhile, an optimal tracking controller is designed to ensure the tracking performance. Finally, experimental results are given to show the effectiveness of the proposed scheme.

Improved Artificial Bee Colony Algorithm and Its Application in LQR Controller Optimization

In order to get the optimal performance of controller and improve the design efficiency, artificial bee colony (ABC) algorithm as a metaheuristic approach which is inspired by the collective foraging behavior of honey bee swarms is considered for optimal linear quadratic regulator (LQR) design in this paper. Furthermore, for accelerating the convergence speed and enhancing the diversities of population of the traditional ABC algorithm, improved solution searching approach is proposed creatively. The proposed approach refers to the procedure of differential mutation in differential evolutionary (DE) algorithm and produces uniform distributed food sources in employed bee phase to avoid local optimal solution. Meanwhile, during the onlooker bees searching stage where the solution search area has been narrowed by employed bees, new solutions are generated around the solution with higher fitness value to keep the fitness values increasing monotonously. The improved ABC algorithm is applied to the optimization of LQR controller for the circular-rail double inverted pendulum system, and the simulation results show the effect on the proposed optimization problem.

Operator-based robust right coprime factorization design for planar gantry crane

In this paper, a nonlinear robust control scheme is considered for a planar gantry crane system. The influence of motion friction and viscous friction of the linear motor and viscous friction of the cable is investigated under different operating conditions. Then, the Lagrange motion equation of the planar gantry crane is setup, which can be described as a nonlinear dynamic model. For this system, there exist one input force and two outputs including the displacement distance of the linear motor and the swing angle of the cable, that is, it is a nonlinear underactuated system. In this paper, the swing angle is regarded as variable parameter, which is calculated approximately using the force and the displacement distance. As a result, it leads some uncertainties in the considered model, which is unknown but bounded. To avoid the influence of the unknown uncertainties, operator-based robust right coprime factorization approach is considered for the nonlinear system. The stability of the control system is guaranteed by robust right coprime factorization condition. The nonlinear robust controller makes the linear motor move to the desired position and the swing of the cable go to zero nonoscillatory. Numerical simulation is given to show the effectiveness of the proposed method.

Robust Control System Design of a Direct Current Governor System with Input Constraints

In dual closed loop direct current governor system, startup current is usually much larger than rated current so that current restricting problem must be considered during startup stage of direct current motor. In this paper, a dual closed loop robust control scheme is presented for a direct current governor system with input constraints by using robust right coprime factorization approach. PI regulator is designed for inner current loop and robust right coprime factorization with input constraints is employed for outer speed loop. Meanwhile, speed tracking control problem is also considered. Finally, simulation result is given to show the effectiveness of the proposed approach.

Operator-based actuator fault detection system design of a thermal process

In this paper, an operator-based fault detection method for actuator fault of an aluminium plate thermal process is proposed by using operator-based robust right coprime factorisation (RCF) approach. In details, operator-based output tracking and fault detection system design for single input single output (SISO) system is proposed, then the theoretical analysis is extended to multi input multi output (MIMO) system. Based on the proposed design schemes, the output tracking performance can be realised and the actuator fault can be detected. After developing a mathematical model of the three-input three-output aluminium plate thermal process, the proposed design schemes are applied and the effectiveness of that is confirmed by the simulation results.

Application of robust right coprime factorization approach to a distributed process control system

In this paper, nonlinear feedback control of a distributed process is considered by using robust right coprime factorization approach. The distributed process model is developed. The model includes a water level process model of single tank and a water flow process model for twin-tank. Then, robust right coprime factorization based nonlinear control is proposed for the distributed process consisting of the water level process and the water flow process. Furthermore, from the industrial application viewpoint, CENTUM CS3000 based implementation issues of robust right coprime factorization operators are investigated. Finally, the experimental results are given to show the effectiveness of the proposed approach.

Operator-based robust nonlinear control for SISO and MIMO nonlinear systems with PI hysteresis

In this paper, operator based robust nonlinear control for single-input single-output U+0028 SISO U+0029 and multi-input multi-output U+0028 MIMO U+0029 nonlinear uncertain systems preceded by generalized Prandtl-Ishlinskii U+0028 PI U+0029 hysteresis is considered respectively. In detail, by using operator based robust right coprime factorization approach, the control system design structures including feedforward and feedback controllers for both SISO and MIMO nonlinear uncertain systems are given, respectively. In which, the controller design includes the information of PI hysteresis and its inverse, and some sufficient conditions for the controllers in both SISO and MIMO systems should be satisfied are also derived respectively. Based on the proposed conditions, influence from hysteresis is rejected, the systems are robustly stable and output tracking performance can be realized. Finally, the effectiveness of the proposed method is confirmed by numerical simulations.