Robust block second order sliding mode control for a quadrotor

This paper presents the design of a controller based on the block control technique combined with the super twisting control algorithm for trajectory tracking of a quadrotor helicopter. A first order exact differentiator is used in order to estimate the virtual control inputs, which simplifies the control law design. In addition, the wind parameter resulting from the aerodynamic forces is also estimated in order to ensure robustness against these unmatched perturbations. The stability and finite time convergence of the exact differentiator have been recently proved by means of Lyapunov functions, and therefore the stability analysis of the proposed controller has been carried out along the same lines. The performance and effectiveness of the proposed controller are tested in a simulation study taking into account external disturbances.     

Robust sliding mode guidance and control for soft landing on small bodies

The variable structure control (VSC) with sliding mode is presented to design a tracking control law to ensure the fast and accurate response and robustness of guidance law in this paper. First, the small body dynamic equation is deduced in the landing site coordinate system. Second, the desired trajectory is planned in the condition of safe soft landing constraints. Third, the guidance law based on VSC is designed to track the desired trajectory and succeed in landing on the surface of small body. Finally, the guidance and control algorithm is formed and the effectiveness of algorithm is verified by numerical Monte Carlo simulations.     

Fuzzy sliding mode control design based on stability margins

Fuzzy Sliding Mode Control (FSMC) algorithms have been widely studied and implemented to combine the robustness of the classical sliding mode control with lower chattering levels, but industrial implementation requires a robustness measurement such as the stability margins. Due to the significance of stability margins in control systems, the computation of the phase Margin (PM) and gain margin (GM) in FSMC has already been proposed with the self-sustained oscillations considered as an unstable behavior. However, a procedure to obtain the desired PM and GM from the FSMC design itself has not been developed yet. Hence, in this study, a method to design FSMC algorithms with desired PM and GM is presented. The describing function (DF) and harmonic balance (HB) techniques were used to identify the limit cycles; then, a step-by-step process to tune the FSMC parameters was provided. Examples and simulations are presented to validate the proposed method.     

Robust sliding mode control of a DC/DC Boost converter with switching frequency regulation

This paper presents the design of a hysteresis band controller to regulate the switching frequency in a sliding mode controlled nonlinear Boost power converter. The proposed architecture relies on a piecewise linear modeling of the switching function behavior within the hysteresis band, and consists of a continuous-time integral-type controller that modifies the amplitude of the hysteresis band of the comparator in accordance with the error between the desired and the actually measured switching period. The study provides the dynamical models of the converter operating in sliding mode and the switching frequency control loop. Moreover, the design of the parameters of both the sliding mode control and the switching frequency controller guarantee the fulfilment of the desired output voltage regulation of the Boost converter and the steady state setting of the switching frequency with a known, taylored dynamics. A Boost power converter prototype has been built to validate the proposal. Experimental results confirm the predicted good performance of the controllers, as well as the robustness with respect to changes in the switching frequency reference and the system parameters.     

基于随机微分博弈的协同创新知识共享策略

在考虑随机因素干扰的情形下,通过建立一个随机微分博弈模型研究了产学研协同创新主体间的知识共享问题。运用动态规划方法分别求得了Stackelberg主从博弈和协同合作博弈两种下均衡的知识共享策略和创新补贴比例,并对两种博弈模式下的均衡结果进行了比较。比较结果显示:(1)在Stackelberg主从博弈和协同合作博弈两种模式下,知识共享的成本及其创新能力、知识共享的边际收益及其折旧率对创新主体共享的知识量产生重要影响,当知识共享的成本及其折旧率提高时,共享的知识量将减少;当知识创新能力及其共享的边际收益提升时,共享的知识量将提高。(2)在协同合作博弈下,创新主体共享的知识量、知识创新系统的总收益、知识创新量的期望值和方差均高于Stackelberg主从博弈下的值。     

Event-triggered asynchronous sliding mode control of CSTR based on Markov model

In this paper, an asynchronous sliding mode control design method based on the event-triggered strategy is proposed for the continuous stirred tank reactor (CSTR) under external disturbance. Firstly, with the purpose of appropriately modeling the multi-mode switching phenomenon in the CSTR caused by the fluctuation of temperature and concentration, the Markov process is applied. Secondly, the asynchronous switching characteristics are introduced to describe mismatch between the controller and the system, which caused by some factors such as signal transmission delay and packet dropout. In order to effectively estimate the system states that cannot be measured in real time, an observer based on the event-triggered strategy is proposed, which also can reduce the computational cost. In addition, a sliding mode controller is designed to ensure the dynamic stability and the sliding dynamics is reachable in a finite time. Finally, the effectiveness of the proposed method is verified by simulation experiments.     

A quasi-optimal sliding mode control scheme based on control Lyapunov function

In this paper, the sliding mode control (SMC) method is integrated with a nonlinear suboptimal control method based on control Lyapunov function (CLF). According to the system nominal part, a CLF is first constructed in general to facilitate the nonlinear optimal system design and Sontag's formula is used in particular to generate a suboptimal controller. To take system uncertainties into account, the SMC mechanism is designed based on the CLF. By integration, the suboptimal control and SMC are made to function in a complementary manner. When the system state is far away from the equilibrium and the system nominal part is predominant, the nonlinear optimal control part will govern the system response as well as drive the system state approach the equilibrium in an optimal fashion. On the contrary, when approaching the equilibrium such that system perturbations become the main factor, the SMC will take over the control task to warrant the desired robustness property and achieve precise control.     

基于异质型寡头博弈模型的产出和初始排污权分配研究*

在产品生产市场和排污权交易市场相关联的环境下,基于一个一般性的异质型寡头博弈模型对厂商的均衡产出和初始排污权的分配问题进行了研究。通过对模型的求解,给出了厂商的均衡产出的解析表达式,分析了厂商的均衡产出随排污权交易市场价格(以下简称排污权价格)的变化规律。结果表明：厂商的均衡总产出与排污权价格呈反向变化关系;当所有厂商的致污率系数相等时,各厂商的均衡产出以相同的幅度与排污权价格呈反向变化关系;当所有厂商的致污率系数不完全相等时,排污权价格对不同类型的厂商的均衡产出具有不同的调节功能,清洁程度或污染度越高的厂商的均衡产出对排污权价格变动的敏感度也越高。进一步,在前述结果的基础上,获得了厂商的初始排污权表达式,并基于拍卖机制分析了初始排污权的分配过程。最后,通过算例验证了模型结果的正确性。     

Fractional-order sliding mode control for a bearingless induction motor based on improved load torque observer

In order to improve the anti-disturbance performance of a bearingless induction motor (BIM) control system, a fractional-order sliding mode control (FOSMC) strategy based on improved load torque observer is proposed on the basis of the sliding mode speed regulation system. Using the information memory and genetic characteristics of the fractional calculus operator, the fractional integral term of the speed error is introduced in the design of the traditional sliding surface, which reduces the influence of disturbance on the speed regulation system. The fractional-order sliding mode control law is derived based on the BIM mathematical model, and the stability of the control law is proved by Lyapunov theorem. An improved observer is constructed based on the BIM state equations, and the real-time observed load torque is introduced into the fractional-order sliding mode controller. To improve the observer's convergence speed, the proportional integral form is used to replace the integral form in the traditional reduced order load observer. And the state error feedback coefficients of the improved load observer are calculated. Both simulation and experimental results verified the effectiveness of the proposed control strategy.     

Path tracking of unmanned agricultural tractors based on a novel adaptive second-order sliding mode control

Unmanned tractors are widely adopted in agricultural operations as autonomous driving technology progresses. The current path tracking control methods are limited by the unstructured farmland, the accuracy and anti-interference ability needed to be improved. This paper presents a novel adaptive second-order sliding mode (ASOSM) control method to tackle the aforementioned problems in practical implementation. First, we introduce a preview lateral offset model based on the preview kinematic and tractor dynamic model, which helps solve the under-actuated problem in path tracking. Then, the ASOSM controller is designed using the revamped adding a power integrator (API) and adaptive mechanism, which ensures that the sliding variable is converged to zero within the finite time. Meanwhile, the chattering problem in traditional sliding mode control is relieved. Finally, a high-fidelity and full-car model is established under Simulink/Carsim environment, and comparative simulations conrm the superiority of the designed control method.     

Position stabilization of a Stewart platform: High-order sliding mode observers based approach

The problem of robust exact control for a Stewart platform with smooth bounded unknown inputs is considered. This platform has three degrees of freedom and it is used as a remote surveillance device. We consider high-order sliding mode observers to provide both theoretical exact observation and unknown input identification. In this paper, a methodology is proposed to select the most adequate control strategy for unknown external perturbation identification. The results obtained are illustrated by simulations.     

Second order sliding mode output feedback control with switching gains—Application to the control of a pneumatic actuator

This paper proposes a switching gains output feedback controller, which is a sample-based second order sliding mode one. First, constructive convergence conditions are established for the controller, in the unperturbed and perturbed cases. Then, a gain adjustment mechanism of the gain, based on the aforementioned convergence conditions, allows us to reduce gain magnitude, and then to reduce the chattering effect. This new algorithm is experimentally applied for the position control of an electropneumatic actuator.     

A real-time estimation and control scheme for induction motors based on sliding mode theory

In this paper a sliding mode position control for high-performance real-time applications of induction motors is developed. The design also incorporates a sliding mode rotor flux estimator in order to avoid the flux sensors. The proposed control scheme presents a low computational cost and therefore can be implemented easily in a real-time applications using a low cost Digital Signal Processor (DSP). The stability analysis of the observer and the controller, under parameter uncertainties and load torque disturbances, is provided using the Lyapunov stability theory. Finally simulated and experimental results show that the proposed controller with the proposed observer provides a good trajectory tracking and that this scheme is robust with respect to plant parameter variations and external load disturbances.     

Trajectory tracking of a quadrotor using extend state observer based U-model enhanced double sliding mode control

This paper develops a novel U-model enhanced double sliding mode controller (UDSMC) for a quadrotor based on multiple-input and multiple-output extended-state-observer (MIMO-ESO). UDSMC is designed using Lyapunov synthesis and Hurwitz stability to not only cancel the complex dynamics and nonlinearity, but also stabilize the uncertainty and external disturbance of the underlying quadrotors. MIMO-ESO is designed to estimate the unmeasurable velocities which can reduce the impact of sensor measurement errors in practice. The difficulties associated with quadrotor velocity's measurement disturbances and uncertain aerodynamics are successfully addressed in this control design. Rigorous theoretical analysis has been carried out to determine whether the proposed control system can achieve stable trajectory tracking performance, and a comparative real-time experimental study has also been carried out to verify the better effectiveness of the proposed control system than the built-in PID control system.     

我国高新技术企业技术创新模式选择研究—基于演化博弈的视角

为研究高新技术企业的技术创新模式选择行为的内在决策机理,借助演化经济学研究工具,构建了高新技术企业技术创新模式选择的博弈模型,并对策略选择进行了演化动态稳定性分析,用数值仿真演示了决策参数的不同取值和初始条件的改变对演化结果的影响。结果表明:高新技术企业技术创新模式选择演化系统收敛于两种模式,一种为理想状态,一种为不良"锁定"状态;通过调节参数可以跳出不良"锁定"状态,诱导企业朝着期望的方向演化。     

基于前景理论的政企低碳策略演化博弈分析

从前景理论视角分析地方政府监督下的企业低碳生产策略,建立企业和地方政府的收益感知矩阵,运用复制动态方程分析企业和地方政府的低碳策略演化博弈过程,模拟分析环境恶化风险成本、惩罚成本、低碳补贴及地方政府收益变化对演化结果的影响。研究结果表明:企业和地方政府的低碳策略取决于对方低碳策略的选择和参数感知价值,参数感知价值围绕临界值上下波动时,低碳策略随之变化;在一定条件下,企业和地方政府的低碳策略演化为环境效益最大化的企业低碳生产、地方政府监督策略集合;企业和地方政府对损益价值的感知大小影响环境效益最大化的实现;企业选择低碳生产及地方政府选择监督的概率影响策略收敛的速度。     

基于演化博弈的上下游企业产业共生形成模式选择

针对产业共生形成模式的选择问题,以演化博弈为主要方法构建产业共生演化博弈模型,以实现社会总经济效益最大化为目标,从治理主体和驱动模式两个角度出发提出产业共生形成的4种情景模式;在此基础上,通过计算得出可以实现产业共生的9个参数情形及其对应的产业共生实现概率。研究表明:第一,在给定参数的情形下,可以根据该模型进行上下游企业工业废弃物治理的形成模式选择;第二,无论治理主体是上游企业还是下游企业,政府与市场在机制选择中的替换作用并没有明确的边界;第三,当治理主体为下游企业时,仅靠市场作用很难实现上下游企业的合作。最后基于研究结果提出相关政策建议,以期为政府和企业决策提供理论支持。     

Fault-tolerant adaptive control for uncertain switched systems with time-varying delay and actuator faults based on sliding mode technique

This paper utilizes the sliding mode approach to tackle the issue of adaptive control for uncertain switched systems with time-varying delay and actuator faults. Firstly, a kind of mathematical model of switched time-varying delay systems under sudden actuator faults is defined. Then, a linear sliding manifold is constructed, followed by some adequate conditions for exponential stability of the switched systems running on the sliding phase. Furthermore, an adaptive fault-tolerant controller for handling the actuator degradation is designed and the reachability of the established sliding manifold is proved. At last, a series of simulation examples are provided to demonstrate the efficiency of the proposed solution.