Active disturbance rejection based trajectory linearization control for hypersonic reentry vehicle with bounded uncertainties

This paper investigates a novel compound control scheme combined with the advantages of trajectory linearization control (TLC) and alternative active disturbance rejection control (ADRC) for hypersonic reentry vehicle (HRV) attitude tracking system with bounded uncertainties. Firstly, in order to overcome actuator saturation problem, nonlinear tracking differentiator (TD) is applied in the attitude loop to achieve fewer control consumption. Then, linear extended state observers (LESO) are constructed to estimate the uncertainties acting on the LTV system in the attitude and angular rate loop. In addition, feedback linearization (FL) based controllers are designed using estimates of uncertainties generated by LESO in each loop, which enable the tracking error for closed-loop system in the presence of large uncertainties to converge to the residual set of the origin asymptotically. Finally, the compound controllers are derived by integrating with the nominal controller for open-loop nonlinear system and FL based controller. Also, comparisons and simulation results are presented to illustrate the effectiveness of the control strategy.     

Robust internal model control of servo motor based on sliding mode control approach

This paper proposes a robust internal model control (IMC) based on sliding mode control (SMC) approach for high-performance motion control of a servo motor subject to uncertainties and/or disturbances. The proposed control strategy considers not only the simplicity and intuition of the IMC-based controller for a prescribed tracking performance but also the effectiveness of the SMC scheme to guarantee the robustness of the servo system. Since the performance of the IMC-based controller can be analyzed via a SMC structure, a robust control law based on the SMC technique is introduced into the IMC scheme to decrease the sensitivity to uncertainties and enhance the resistance to disturbances. Moreover, the 2-degree-of-freedom IMC integrating the robust SMC scheme is developed to further improve the control performance. The stability is analyzed based on Lyapunov theory, and the theoretical results show that a prescribed transient tracking performance and a final tracking accuracy of the servo system can be guaranteed. Comparative simulations and experiments are investigated to verify the high performance nature of the proposed control strategy.     

Adaptive super-twisting fractional-order nonsingular terminal sliding mode control of cable-driven manipulators

This paper proposes a novel adaptive super-twisting fractional-order nonsingular terminal sliding mode (AST–FONTSM) control scheme using time delay estimation (TDE) for the cable-driven manipulators. The designed control scheme utilizes TDE to obtain the estimation of system dynamics, and therefore no system dynamic model information will be required. Afterwards, AST and FONTSM schemes are applied to ensure good control performance in both reaching and sliding mode phases. Due to the adoption of AST scheme, good robustness and high control precision are obtained in the reaching phase, while the boundary information of the lumped uncertainties will be no longer required. Thanks to the utilization of FONTSM error dynamics, fast convergence and accurate tracking and strong robustness can be simultaneously ensured in the sliding mode phase. Corresponding comparative simulation and experimental results demonstrate the effectiveness and superiorities of our proposed method over the existing control methods.     

Sliding mode control with third-order contour error estimation for free-form contour following

To reduce the contour error in contour-following tasks, the most common method is to design a contour controller based on the contour error model. Therefore, how to estimate the contour error in real-time and with high accuracy plays an important role in contour-following control. It is difficult to guarantee real-time performance, high estimation accuracy and strong robustness against arbitrary trajectories at the same time. In this paper, a contour error estimation method based on the third-order osculating helix is proposed. The osculating helix can fully consider the geometric characteristics of the interpolation trajectory and is closer to the desired interpolation trajectory. On this basis, PD-type tracking error sliding mode surface and PD-type contour error sliding mode surface are redesigned to fully take into account the regulating effect of the velocity tracking error and velocity contour error. Experimental results demonstrate the effectiveness of the proposed contour control approach.     

Adaptive compensation control for attitude adjustment of quad-rotor unmanned aerial vehicle

A compensation control strategy based on adaptive back-stepping technique is presented to address the problem of attitude adjustment for a quad-rotor unmanned aerial vehicle (QR- UAV) with inertia parameter uncertainties, the limited airflow disturbance and the partial loss of rotation speed effectiveness. In the design process of control system, adaptive estimation technique is introduced into the closed loop system in order to compensate the lumped disturbance term. More specifically, the designed controller utilizes “prescribed performance bounds” method, and therefore guarantees the transient performance of tracking errors, even in the presence of the lumped disturbance. Adaptive compensation algorithms under the proposed closed loop system structure are derived in the sense of Lyapunov stability analysis such that the attitude tracking error converge to a small neighborhood of equilibrium point. Finally, the simulation results demonstrate the effectiveness of the proposed controller.     

Adaptive sliding mode disturbance rejection control with prescribed performance for robotic manipulators

This study proposes an adaptive sliding mode disturbance rejection control with prescribed performance for robotic manipulators. A transformation with respect to tracking error using certain performance functions is used to ensure the transient and steady-state performances of the trajectory tracking control for robotic manipulators. Using the transformed error, a nonsingular terminal sliding mode surface is proposed. A continuous terminal sliding mode control (SMC) is presented to stabilize the system. To compensate for the uncertainty and external disturbance, a novel sliding mode disturbance observer is proposed. Considering the unknown boundary of the derivative of a lumped disturbance, an adaptive law based on the idea of equivalent control is designed. Combining the adaptive law, continuous nonsingular terminal SMC, and sliding mode disturbance observer, the adaptive sliding mode disturbance rejection control with prescribed performance is developed. Simulations are carried out to demonstrate the effectiveness of the proposed approach.     

Regulated model-based and non-model-based sliding mode control of a MEMS vibratory gyroscope

Control of MEMS vibratory gyros and angular rate estimation form the challenging problem which is the focus of this paper. To this end, the model-based and non-model-based sliding model control (SMC) approaches are presented, and a chattering elimination method called regulated SMC (RSMC) is invoked to improve tracking control of the drive and sense modes of the uncertain vibratory gyroscope. The force-balancing method is employed to estimate the unknown rotation rate and quadrature error term using two desired trajectories for conventional mode with the same amplitude and different frequencies. Finally, effectiveness of the regulated model-based and non-model-based SMC scheme even in the presence of significant uncertainties is demonstrated through simulations.     

On decentralized adaptive full-order sliding mode control of multiple UAVs

In this study, a novel decentralized adaptive full-order sliding mode control framework is proposed for the robust synchronized formation motion of multiple unmanned aerial vehicles (UAVs) subject to system uncertainty. First, a full-order sliding mode surface in a decentralized manner is designed to incorporate both the individual position tracking error and the synchronized formation error while the UAV group is engaged in building a certain desired geometric pattern in three dimensional space. Second, a decentralized virtual plant controller is constructed which allows the embedded low-pass filter to attain the chattering free property of the sliding mode controller. In addition, robust adaptive technique is integrated in the decentralized chattering free sliding control design in order to handle unknown bounded uncertainties, without requirements for assuming a priori knowledge of bounds on the system uncertainties as stated in conventional chattering free control methods. Subsequently, system robustness as well as stability of the decentralized full-order sliding mode control of multiple UAVs is synthesized. Numerical simulation results illustrate the effectiveness of the proposed control framework to achieve robust 3D formation flight of the multi-UAV system.     

Adaptive robust motion trajectory tracking control of pneumatic cylinders with LuGre model-based friction compensation

Friction compensation is particularly important for motion trajectory tracking control of pneumatic cylinders at low speed movement. However, most of the existing model-based friction compensation schemes use simple classical models, which are not enough to address applications with high-accuracy position requirements. Furthermore, the friction force in the cylinder is time-varying, and there exist rather severe unmodelled dynamics and unknown disturbances in the pneumatic system. To deal with these problems effectively, an adaptive robust controller with LuGre model-based dynamic friction compensation is constructed. The proposed controller employs on-line recursive least squares estimation（RLSE） to reduce the extent of parametric uncertainties, and utilizes the sliding mode control method to attenuate the effects of parameter estimation errors, unmodelled dynamics and disturbances. In addition, in order to realize LuGre model-based friction compensation, the modified dual-observer structure for estimating immeasurable friction internal state is developed. Therefore, a prescribed motion tracking transient performance and final tracking accuracy can be guaranteed. Since the system model uncertainties are unmatched, the recursive backstepping design technology is applied. In order to solve the conflicts between the sliding mode control design and the adaptive control design, the projection mapping is used to condition the RLSE algorithm so that the parameter estimates are kept within a known bounded convex set. Finally, the proposed controller is tested for tracking sinusoidal trajectories and smooth square trajectory under different loads and sudden disturbance. The testing results demonstrate that the achievable performance of the proposed controller is excellent and is much better than most other studies in literature. Especially when a 0.5 Hz sinusoidal trajectory is tracked, the maximum tracking error is 0.96 mm and the average tracking error is 0.45 mm. This paper constructs an adaptive robust controller     

Finite-time control for nonlinear spacecraft attitude based on terminal sliding mode technique

In this paper, a fast terminal sliding mode control (FTSMC) scheme with double closed loops is proposed for the spacecraft attitude control. The FTSMC laws are included both in an inner control loop and an outer control loop. Firstly, a fast terminal sliding surface (FTSS) is constructed, which can drive the inner loop tracking-error and the outer loop tracking-error on the FTSS to converge to zero in finite time. Secondly, FTSMC strategy is designed by using Lyaponov's method for ensuring the occurrence of the sliding motion in finite time, which can hold the character of fast transient response and improve the tracking accuracy. It is proved that FTSMC can guarantee the convergence of tracking-error in both approaching and sliding mode surface. Finally, simulation results demonstrate the effectiveness of the proposed control scheme.     

基于模糊滑模控制和两级滤波滑模观测器的PMSM改进控制策略

针对传统带有滑模观测器的永磁同步电机控制系统中转矩脉动大、抖振明显、反电动势估计精度差等问题,提出基于模糊滑模控制和两级滤波滑模观测器的PMSM改进控制策略.首先,在速度环提出基于双曲正弦函数的新型趋近率,结合模糊控制思想对趋近率参数实现自整定,设计了一种基于新型趋近率的模糊积分滑模速度环控制器,并且对新型趋近率的抖振抑制效果给出严格分析.其次,提出基于变截止频率低通滤波器和修正反电动势观测器的两级滤波结构,抑制反电动势中的高频分量和测量噪声,并对转子位置进行合理补偿,继而设计了两级滤波滑模观测器;通过Lyapunov判据对本文提出控制策略的稳定性进行了推导证明.仿真和实验结果表明,与传统滑模观测器相比,改进的控制器使电机在启动和受到外部扰动时系统响应良好,有效改善了转矩脉动、抖振、反电动势的估计精度等问题.     

Adaptive sliding mode current control with sliding mode disturbance observer for PMSM drives

This paper focuses on the current control of a permanent magnet synchronous motor (PMSM) for electric drives with model uncertainties and external disturbances. To improve the performance of the PMSM current loop in terms of the speed of response, tracking accuracy, and robustness, a hybrid control strategy is proposed by combining the adaptive sliding mode control and sliding mode disturbance observer (SMDO). An adaptive law is introduced in the sliding mode current controller to improve the dynamic response speed of the current loop and robustness of the PMSM drive system to the existing parameter variations. The SMDO is used as a compensator to restrain the external disturbances and reduce the sliding mode control gains. Experiments results demonstrate that the proposed control strategy can guarantee strong anti-disturbance capability of the PMSM drive system with improved current and speed-tracking performance.     

Sliding mode output feedback control based on tracking error observer with disturbance estimator

For a class of systems who suffers from disturbances, an original output feedback sliding mode control method is presented based on a novel tracking error observer with disturbance estimator. The mathematical models of the systems are not required to be with high accuracy, and the disturbances can be vanishing or nonvanishing, while the bounds of disturbances are unknown. By constructing a differential sliding surface and employing reaching law approach, a sliding mode controller is obtained. On the basis of an extended disturbance estimator, a creative tracking error observer is produced. By using the observation of tracking error and the estimation of disturbance, the sliding mode controller is implementable. It is proved that the disturbance estimation error and tracking observation error are bounded, the sliding surface is reachable and the closed-loop system is robustly stable. The simulations on a servomotor positioning system and a five-degree-of-freedom active magnetic bearings system verify the effect of the proposed method.     

基于改进扩展状态观测器的四旋翼无人机轨迹鲁棒跟踪控制

针对四旋翼无人机在轨迹跟踪过程中会受到内外部扰动、模型误差等不确定性因素的影响,本文提出了一种基于改进型扩展状态观测器的积分滑模控制方案。具体来讲,首先,将四旋翼无人机系统存在的模型误差以及内外部扰动等不确定性因素视作集总干扰,通过借鉴的改进扩展状态观测器对其进行观测;进而,在此基础上,进一步考虑四旋翼无人机系统控制的连续性,基于四旋翼无人机轨迹误差、速度误差、姿态角误差和姿态角速度误差设计积分滑模控制器,分析了系统的稳定性并分别进行了数值仿真和实机实验。结果表明,采用本文算法时,在数值仿真中,各状态跟踪误差不超过1%,跟踪精度最高;在实机实验中,位置跟踪误差总体上能控制在20%以下。因此,本文方法具备有效性和可行性。     

时变边界层滑模控制在多连杆机械手的应用

针对多连杆机械手的跟踪控制问题,提出了具有时变边界层的滑模变结构控制设计,同固定宽度边界层滑模控制相比,在削弱滑模控制中抖振现象和对参数不确定性的鲁棒性的同时,进一步提高了控制精度.     

Control of a dual stage magnetostrictive actuator and linear motor feed drive system

A dual stage feed drive system is well suited to satisfying current demands of high performance machining with tight position control under high feed rates in the presence of disturbances. It does this by integrating an actuator with high position resolution and fast response together with a conventional linear drive. A magnetostrictive actuator (MA) with a bandwidth in the kHz range capable of several kN of force output is an ideal candidate for use as the fine positioning element in such a dual stage system. However, MAs display significant hysteresis in their performance. This makes the effective implementation of real-time fast servo control challenging. In this paper, a dynamic Preisach model is utilized to reduce the undesired nonlinearity. A sliding mode controller (SMC) is designed to deal with uncertainties such as the Preisach modeling error as well as external disturbances so as to ensure a robust stable system. Experimental results show the servo performance improvement during a feed step test for single axis control and a single axis component of a sharp path interpolation test.     

自主飞艇侧滑角姿态建模及控制

针对特定结构的平流层信息平台——自主飞艇,建立侧滑角姿态动力学方程,并将这一分段函数表述为混杂逻辑方程。根据飞艇侧滑角姿态跟踪误差值的大小,判断其侧滑角姿态调整范围。当飞艇需要进行较大侧滑角姿态调整时,辅助推进系统产生附加力矩,采用基于极点配置的PID控制器,使得系统具有需要的动态特性和很好的可靠性能,对于较小的侧滑角姿态调整,改变方向舵操纵角,采用基于等效策略的滑模变结构控制器,保证系统具有很好的抗干扰性能及良好的跟踪精度。通过合理配置极点的位置,确定滑模面参数,设计出的0?-1逻辑触发器成功整合了这两种控制器在不同工况下的应用,避免了控制模式切换过程中常见的振动以致于系统失稳现象。数字仿真结果表明,采用的控制手段及整合方式是合理的。     

Robust partial integrated guidance and control for missiles via extended state observer

A novel extended state observer (ESO) based control is proposed for a class of nonlinear systems subject to multiple uncertainties, and then applied to partial integrated guidance and control (PIGC) design for a missile. The proposed control strategy incorporates both an ESO and an adaptive sliding mode control law. The multiple uncertainties are treated as an extended state of the plant, and then estimate them using the ESO and compensate for them in the control action, in real time. Based on the output of the ESO, the resulting adaptive sliding mode control law is inherently continuous and differentiable. Strict proof is given to show that the estimation error of the ESO can be arbitrarily small in a finite time. In addition, the adaptive sliding mode control law can achieve finite time convergence to a neighborhood of the origin, and the accurate expression of the convergent region is given. Finally, simulations are conducted on the planar missile–target engagement geometry. The effectiveness of the proposed control strategy in enhanced interception performance and improved robustness against multiple uncertainties are demonstrated.     

基于terminal滑模控制的小卫星机动方法

采用terminal滑模控制方法研究了以单框架控制力矩陀螺(SGCMG)为执行机构的小卫星的姿态机动控制。首先,基于修正罗德里格斯(MRP)参数建立了小卫星数学模型,以terminal滑模控制方法进行控制力矩规划。然后,采用SGCMGs作为小卫星执行机构,以非对角奇异鲁棒操纵律跟踪terminal滑模控制产生的期望力矩;通过仿真分析归纳出terminal滑模控制设计参数的变化规律和选取原则。最后,利用小卫星三轴气浮转台实验验证termianl滑模控制方法的实用性。实验显示:根据参数选取原则设定的参数进行小卫星机动稳定实验得到的姿态角和姿态角速度控制精度和稳态误差分别小于0.1°和0.01(°)/s,满足三轴气浮转台最佳控制精度。结果表明terminal滑模控制方法在小卫星机动稳定任务中具有很高的控制精度和稳定度,能够为小卫星成像任务稳定执行提供良好的基础。     

Neural network adaptive sliding mode control for omnidirectional vehicle with uncertainties

This paper presents a novel neural network adaptive sliding mode control (NNASMC) method to design the dynamic control system for an omnidirectional vehicle. The omnidirectional vehicle is equipped with four Mecanum wheels that are actuated by separate motors, and thus has the omnidirectional mobility and excellent athletic ability in a narrow space. Considering various uncertainties and unknown external disturbances, kinematic and dynamic models of the omnidirectional vehicle are established. The inner-loop controller is designed based the sliding mode control (SMC) method, while the out-loop controller uses the proportion integral derivative (PID) method. In order to achieve the stable and robust performance, the artificial neural network (ANN) based adaptive law is introduced to model and estimated the various uncertainties disturbances. Stability and robustness of the proposed control method are analyzed using the Lyapunov theory. The performance of the proposed NNASMC method is verified and compared with the classical PID controller and SMC controller through both the computer simulation and the platform experiment. Results validate the effectiveness and robustness of the NNASMC method in presence of uncertainties and unknown external disturbances.