Quadrotor Control Via Robust Generalized Dynamic Inversion and Adaptive Non‐Singular Terminal Sliding Mode

A robust two‐loops structured control system design for quadrotor's position/attitude trajectory tracking is proposed. The aim of the outer loop is to provide the roll/pitch tilting commands to the inner loop, which in turns generates the tilting angles that control the quadrotor's center of gravity in the horizontal plane. The outer loop utilizes Robust Generalized Dynamic Inversion (RGDI) of a prescribed asymptotically stable differential equation in the deviation function of the horizontal position coordinates from their reference trajectories. The inner loop employs an Adaptive Non‐singular Terminal Sliding Mode (ANTSM) to control the tilting angles, in addition to controlling the yaw attitude angle and the vertical position coordinate. The proposed scheme solves the singularity avoidance problems of generalized inversion and terminal sliding mode control. The stability of outer and inner loop is ensured by utilizing positive definite Lyapunov energy function for stable tracking performance against parametric variations and bounded unknown external disturbances. Numerous simulations are conducted on a six Degrees of Freedom (DoF) quadrotor model in the presence of parametric variations, un modeled dynamics, and external disturbances.     

Unmanned bicycle balancing via Lyapunov rule-based fuzzy control

Guaranteed stability fuzzy controller for stabilization the motion of an unmanned bicycle is proposed. First, a fuzzy control system capable of automatically balancing an unmanned bicycle through tracking desired roll angle is developed. Fuzzy logic controller membership functions are defined utilizing scaling factors. To guarantee the stability of the closed loop system, similar to previous approaches reported in the literature, fuzzy If–Then rules are constructed based on Lyapunov stability criterion. It is indicated that the proposed fuzzy controller violates Lyapunov stability criterion. The reason of such a violation is argued in detail. To cope with this shortcoming, some modifications are made to the control strategy to assure stability. Through these modifications, the modified fuzzy controller is developed which simultaneously balances the bicycle and guarantees stability while minimizing roll angle tracking error and its derivative. It is indicated that the improved fuzzy controller can adapt to a variety of initial conditions. Moreover, robustness of the controller against parameter variation is verified through its implementation on different bicycle designs (different sets of bicycle parameters). Simulation results confirm the efficacy of the proposed fuzzy controller in terms of settling time and overshoot in comparison with previous studies. Sensitivity analysis of the controller efficiency with respect to system parameters is also assessed.     

基于准连续高阶滑模的可重复使用运载器再入姿态控制

针对可重复使用运载器再入段的姿态控制问题,提出一种基于准连续高阶滑模的控制方法。将姿态控制系统分为两个回路,分别为角度控制回路与角速度控制回路。角度回路作为外回路产生角速度指令,角速度回路作为内回路跟踪外回路产生的角速度控制指令。为了提高系统的鲁棒性,对两个回路分别设计滑模控制器。外回路中设计基于低通滤波的终端滑模控制方法,以获得平滑的控制量作为角速度指令。内回路设计增加系统相对阶的准连续高阶滑模方法,使控制律中不直接含有符号函数项,保证系统稳定的同时减弱控制器抖振。在具有外界干扰与参数不确定的情况下,使用本文提出的方法进行仿真试验,仿真结果证明了所提出方法的有效性。     

Fuzzy Control for Equilibrium and Roll-Angle Tracking of an Unmanned Bicycle

This study presents steady turning motion and roll-angle tracking controls for an unmanned bicycle. The equations of motion describing the dynamics of a bicycle are developed using Lagrange's equations for quasi-coordinates. Pure rolling without slipping constraints between the ground and two wheels are also considered in this model. These constraints introduce four holonomic and four non-holonomic constraint equations to the model. For the developed bicycle dynamics, one PID and one fuzzy controller that create steering torque are derived to recover the balance of the bicycle from a near-fall state. Furthermore, another fuzzy controller is added for controlling the bicycle to a desired roll angle which leads to its steady circular motion. The bicycle can track a given roll angle while maintaining its balance. The effectiveness of the control schemes is proved by simulation results.     

Nonlinear adaptive control using the Fourier integral and itsapplication to CSTR systems

This paper presents a new nonlinear adaptive tracking controller for a class of general time-variant nonlinear systems. The control system consists of an inner loop and an outer loop. The inner loop is a fuzzy sliding mode control that is used as the feedback controller to overcome random instant disturbances. The stability of the inner loop is designed by the sliding mode control method. The other loop is a Fourier integral-based control that is used as the feedforward controller to overcome the deterministic type of uncertain disturbance. The asymptotic convergence condition of the nonlinear adaptive control system is guaranteed by the Lyapunov direct method. The effectiveness of the proposed controller is illustrated by its application to composition control in a continuously stirred tank reactor system.     

非同轴两轮机器人自平衡与转向闭环控制

针对车速、车身侧倾角和前轮转角变化较大工况下的非同轴两轮机器人在基于前轮转角的自平衡控制中,因动力学模型准确性对自平衡控制带来的影响,设计了基于RBF神经网络模糊滑模控制的自平衡控制器,利用RBF神经网络的逼近特性,对动力学模型中非线性时变的不确定部分进行自适应逼近,从而提高动力学模型的准确性,并借助模糊规则削弱滑模控制中产生的系统抖振;以及因前轮转角用于自平衡控制中难以实现转向闭环控制,建立了基于纯跟踪法的轨迹跟踪控制器,并设计利用车身平衡时车身侧倾角与前轮转角的耦合关系,将转向闭环控制中的目标前轮转角替换为目标车身侧倾角,从而将自平衡控制器与轨迹跟踪控制器相结合,在保证车身平衡行驶的前提下,实现带有轨迹跟踪的转向闭环控制。实验结果表明,凭借动力学模型的较高准确性,RBF神经网络模糊滑模自平衡控制器具有鲁棒性好、超调量低和响应迅速的优点,并且利用车身平衡后车身侧倾角与前轮转角耦合关系,实现转向闭环控制是可行的,具有良好的轨迹跟踪效果。     

Nonlinear robust sliding mode control of a quadrotor unmanned aerial vehicle based on immersion and invariance method

We present an asymptotic tracking controller for an underactuated quadrotor unmanned aerial vehicle using the sliding mode control method and immersion and invariance based adaptive control strategy in this paper. The control system is divided into two loops: the inner‐loop for the attitude control and the outer‐loop for the position. The sliding mode control technology is applied in the inner‐loop to compensate the unmatched nonlinear disturbances, and the immersion and invariance approach is chosen for the outer‐loop to address the parametric uncertainties. The asymptotic tracking of the position and the yaw motion is proven with the Lyapunov based stability analysis and LaSalle's invariance theorem. Real‐time experiment results performed on a hardware‐in‐the‐loop‐simulation testbed are presented to validate the good control performance of the proposed scheme. Copyright © 2014 John Wiley & Sons, Ltd.     

Double Closed-loop Integral Terminal Sliding Mode for a Class of Underactuated Systems Based on Sliding Mode Observer

Aiming to solve the tracking control problem of a class of second-order underactuated mechanical systems with unknown model parts, external disturbances and noise disturbances, a double closed-loop layered integral terminal sliding mode control method based on sliding mode observer is proposed. At the outset, the Lagrange model of the system is transformed into an affine model, and a sliding mode observer is designed according to the system structure. Neatly, the outer loop controller is designed using the observer’s estimated state, and the output value of the outer loop controller is filtered with a low pass filter. Then the inner loop controller is designed by using hierarchical sliding mode control method. On a premise of ensuring tracking performance, the control method can maximally improve convergence speed and reduce chattering even if there are unknown model parts, external interference and noise interference phenomena in the system. This simulation results distinctly display the effectiveness of the control tactics.     

Predictive direct torque control with reduced ripples for induction motor drive based on T‐S fuzzy speed controller

Finite‐state model predictive control (FS‐MPC) has been widely used for controlling power converters and electric drives. Predictive torque control strategy (PTC) evaluates flux and torque in a cost function to generate an optimal inverter switching state in a sampling period. However, the existing PTC method relies on a traditional proportional‐integral (PI) controller in the external loop for speed regulation. Consequently, the torque reference may not be generated properly, especially when a sudden variation of load or inertia takes place. This paper proposes an enhanced predictive torque control scheme. A Takagi‐Sugeno fuzzy logic controller replaces PI in the external loop for speed regulation. Besides, the proposed controller generates a proper torque reference since it plays an important role in cost function design. This improvement ensures accurate tracking and robust control against different uncertainties. The effectiveness of the presented algorithms is investigated by simulation and experimental validation using MATLAB/Simulink with dSpace 1104 real‐time interface.     

基于模糊控制的高超声速飞行器二阶滑模姿态控制

考虑高超声速飞行器飞行过程中气动参数变动导致的不确定,将模糊控制与二阶滑模控制相结合,形成自适应模糊二阶滑模控制器,用于控制高超声速飞行器姿态的飞行系统中.依据奇异摄动理论,设计快速和慢速双闭环系统控制角速率和姿态角.设计二阶滑模控制器用于有效地衰减抖振,同时对姿态角指令实现准确和快速跟踪.采用自适应模糊逻辑逼近高超声速飞行器动力学和运动学模型中的不确定部分,以对控制器进行有效补偿,基于Lyapunov稳定性理论,推导模糊规则参数的自适应律,确保整个闭环控制系统的稳定.仿真结果表明,所提出的高超声速飞行器的自适应模糊滑模控制系统能够有效抑制气动参数摄动的影响,对姿态角指令有较好的跟踪性能.     

交会对接模拟系统姿态位置耦合有限时间控制

针对航天器交会对接模拟系统的姿态同步和位置跟踪控制问题,在存在外界扰动和系统不确定性的情况下,基于改进的快速非奇异终端滑模面和改进的自适应律,采用双闭环控制结构分别设计内环和外环有限时间姿态位置耦合控制器.所提出的自适应律不仅能有效地抑制扰动和不确定性且能保证控制器是连续的.李雅普诺夫理论推导和仿真结果表明,所提出的控制方法能保证系统内环和外环跟踪误差的有限时间稳定性和准确收敛性.     

Nonlinear cascade control of an electro-hydraulic actuator with large payload variation

Electro-hydraulic actuators have been widely used in industrial production, but the unknown variable payload seriously affects its position control accuracy. Therefore, a radial basis function neural network disturbance observer is designed to estimate the lumped disturbance force through strong online learning ability in the absence of force sensor. Besides, a nonlinear cascade controller with double loop structure is proposed in this paper. A global fast terminal sliding mode control method is firstly applied in the outer loop position system, which can eliminate chattering and improve convergence speed comparing to traditional sliding mode control. The inner loop force system adopts a backstepping control method to calculate the actual input of the whole system. Theoretical analysis indicates that the proposed controller is stable even if existing time-variant disturbance. Moreover, three comparative controllers are designed and tested in both simulations and experiments. Comparative results show that the developed method has absolute average errors of 1.14 and 0.49 mm in different position tracking, which means more satisfactory tracking performance compared to the contrast controllers.     

前轮驱动自行车机器人定车运动的鲁棒控制实现

针对一种前轮驱动的自行车机器人,研究其在具有内部结构参数和外部环境不确定性因素下实现原地定车的控制方法;给出基于Lagrange方法的定车运动简化力学模型;提出以欠驱动的车架横滚角为输出,将有驱动的前轮转角作为系统内部动态考虑的鲁棒控制器;仿真结果表明,控制器可以实现快速稳定的定车,并且对系统50%的结构参数误差、幅值为1N.m正弦干扰力矩和幅值为10N.m的脉冲干扰力矩体现了较强的鲁棒性;物理样机实验进一步证明,控制器可以在凹凸不平的地面环境、传感器数据不精确及脉冲干扰力矩下实现±3°车架倾角范围的定车运动。     

考虑车轮纵向滑动的无人自行车平衡控制实现

针对无人自行车在出现车轮纵向滑动下的平衡控制问题,提出一种将自行车车轮纵向滑动引入控制器的方法来实现在一定程度车轮纵向滑动下的无人自行车平衡运动控制。首先引入一种自行车线性变参数(linear parameter-varying, LPV)动力学模型,其次将卡尔曼滤波算法估算的自行车质心线速度作为变参数带入LPV模型中,最后根据引入了车轮滑动因素的LPV模型设计降阶滑模控制器以消除车轮纵向滑动对无人自行车平衡运动的影响。仿真结果表明：当车轮发生小于70%的纵向滑动,降阶滑模控制器能够有效校正自行车的横滚角。样机实验结果进一步证明：降阶滑模控制器能够控制无人自行车分别在车轮纵向滑动较小的水泥地(约8%纵向滑动的)和滑动较大的湿滑草地上(约40%纵向滑动)进行平衡运动。     

ON STABILITY AND PERFORMANCE OF INDUCTION MOTOR SPEED DRIVES WITH SLIDING MODE CURRENT CONTROL

A novel inner loop sliding mode current control scheme for induction motor speed drives is proposed in this paper. The controller design is based on the nonlinear mathematical model of an induction motor in a coordinate system oriented along the rotor flux. The parameters of the PI speed controller are taken into consideration in the inner loop sliding mode current control. Rigorous stability verification for the overall system is provided in this paper. The chattering in sliding mode control is attenuated using the reaching law design method. The experimental results show that the proposed approach exhibits robust tracking performance in the presence of motor parameter variations and load disturbances.     

Finite‐Time Sliding Mode Trajectory Tracking Control of Uncertain Mechanical Systems

The problem of finite‐time tracking control is studied for uncertain nonlinear mechanical systems. To achieve finite‐time convergence of tracking errors, a simple linear sliding surface based on polynomial reference trajectory is proposed to enable the trajectory tracking errors to converge to zero in a finite time, which is assigned arbitrarily in advance. The sliding mode control technique is employed in the development of the finite‐time controller to guarantee the excellent robustness of the closed‐loop system. The proposed sliding mode scheme eliminates the reaching phase problem, so that the closed‐loop system always holds the invariance property to parametric uncertainties and external disturbances. Lyapunov stability analysis is performed to show the global finite‐time convergence of the tracking errors. A numerical example of a rigid spacecraft attitude tracking problem demonstrates the effectiveness of the proposed controller.     

基于MPC的无传感器永磁同步电机NFTSMC仿真研究

为了提高注塑机中永磁同步电机控制系统的运行可靠性,优化永磁同步电机的调速系统动态性能,提出了一种基于模型预测电流控制的无速度传感器永磁同步电机非奇异快速终端滑模控制策略.以模型预测电流控制作为电流控制内环,取代传统的PI调节器,能够有效地抑制电流纹波,提高电流的动态跟踪性能.根据非奇异终端滑模的设计原理,构造外环速度控制器,从而生成期望的q轴电流,提高了系统的稳定性.设计无速度传感器对电机运行转速进行在线辨识,实现对转速和转子位置准确地估计.并与传统的PI调节器进行对比,仿真与实验结果表明该控制策略具有较高的可靠性和快速性.     

粘度测量直流电机调速系统自适应控制器的建模与仿真

基于旋转法的液体粘度测量需要不同等级稳定的电机旋转速度。采用电流转速双闭环来实现对直流电机调速系统的控制。电流内环使用PI控制,转速外环采用大增益比例控制结合PID控制,PID参数使用模糊逻辑进行自整定,这种控制方式可根据输入偏差大小选择不同控制策略实现转速的自适应快速调节与准确跟踪。在Matlab/Simulink平台上搭建基于这种控制器的仿真模型,对直流电机调速系统进行仿真。仿真结果表明这种系统具有良好的控制性能,这种自适应控制器具有良好的动态响应特性,可以消除稳态误差。     

作业型水下机器人姿态调节控制研究

为了解决在作业时水下机器人载体上的机械手伸展过程将会引起载体重心发生变化,导致水下机器人发生纵横倾运动,影响作业效率的问题,考虑到水下机器人控制系统较为复杂,因此引入模糊滑模控制,根据要求设计出一款模糊滑模控制器。利用计算机和MATLAB技术,将水下机器人姿态运动方程与常规PID控制和模糊滑模控制分别结合起来进行仿真分析。仿真结果表明,模糊滑模控制相比于常规PID控制,在机械手关节正弦运动过程中,姿态角下降了20%以上,横倾姿态角度误差减小了30%以上,纵倾姿态角误差也超过了8%以上。在悬停作业过程中,纵横倾姿态角度都下降了30%以上。通过两种不同控制方式的仿真,验证了模糊滑模控制的控制效果要优于常规PID控制,能够取得更好的控制效果,同时利用计算机技术缩短了研究时间、提高了研究效率。     

A multivariable control scheme for robot manipulators

The article puts forward a simple scheme for multivariable control of robot manipulators to achieve trajectory tracking. The scheme is composed of an inner loop stabilizing controller and an outer loop tracking controller. The inner loop utilizes a multivariable PD controller to stabilize the robot by placing the poles of the linearized robot model at some desired locations. The outer loop employs a multivariable PID controller to achieve input-output decoupling and trajectory tracking. The gains of the PD and PID controllers are related directly to the linearized robot model by simple closed-form expressions. The controller gains are updated on-line to cope with variations in the robot model during gross motion and for payload change. Alternatively, the use of high gain controllers for gross motion and payload change is discussed. Computer simulation results are given for illustration.