Intelligent backstepping control for wheeled inverted pendulum

The adaptive output recurrent cerebellar model articulation control (AORCMAC) is an adaptive system with simple computation, good generalization capability and fast learning property. The proposed AORCMAC has superior capability to the conventional cerebellar model articulation controller (CMAC) in efficient learning mechanism and dynamic response. In this study, an intelligent backstepping tracking control system is proposed for wheeled inverted pendulums (WIPs) with unknown system dynamics and external disturbance. In this control system, an ABORCMAC is used to copy an ideal backstepping control (IBC), and a compensated controller is designed to compensate for difference between the IBC law and AORCMAC. Moreover, all adaptation laws of the proposed system are derived based on the Lyapunov stability analysis, the Taylor linearization technique, so that the stability of the closed-loop system can be guaranteed.     

Adaptive backstepping control of wheeled inverted pendulum with velocity estimator

In this paper, we introduce a backstepping control design of a wheeled inverted pendulum. Based on a second-order motion equation of the body angle, an adaptive integral backstepping controller is designed to stabilize the body angle. It is shown that the σ-modification rule in the adaptive update law guarantees the boundedness of the errors in estimating the time-varying signal that is an output of a linear system with every bounded input signal. Then, the stabilizing controller for the wheel angle is constructed by a PD-type positive feedback. The derived controller requires the full-state measurements. In the output feedback case, the K filter or the observer backstepping is needed. However, the structure of the controller becomes complicated. We propose a non-model-based differentiator based on the adaptive update law. Since the non-model-based differentiator does not require any knowledge of the dynamic structure of the signal, we can use it as a velocity estimator for unknown nonlinear systems. Therefore, we replaced the velocity measurement with the estimates by the non-model-based differentiator. Finally, simulation results for the proposed controller are presented.     

倒立摆的自适应积分反步控制策略

针对直线单级倒立摆在模型参数不确定和外部扰动情况下的稳定控制问题,提出一种自适应积分反步控制策略。采用拉格朗日方程建立倒立摆系统的运动学模型,为减少稳态误差,将误差积分项引入反步法,设计了倒立摆的控制器;对含有未知参数的系统非线性状态微分方程,设计适当的Lyapunov函数推导出系统未知参数的自适应更新律,削弱了参数不确定性的影响。将自适应积分反步控制与一般的反步法控制、模糊控制及神经网络控制的仿真结果进行了对比,并在LabVIEW开发环境下进行了实物实验。结果表明,自适应积分反步法可以较为迅速且精确地完成稳定控制,较好地克服系统参数不确定及外部扰动的影响,具有较强的鲁棒性。     

Following control approach based on model predictive control for wheeled inverted pendulum robot

Personal robots, which are seen as tools that will be needed to support our aging society, will be expected to support the comfortable lifestyles of healthy young people as well as the elderly. However, excessive and premature robot support may adversely impact the physical abilities of their human owner/operators. In this paper, the authors propose a personal robot equipped with wheeled inverted pendulum control that can carry baggage and follow the human being. Since such robots could remove the drudgery associated with carrying luggage, their use could also encourage people to go outside and walk briskly, which could contribute to improved health management. This paper proposes a novel control approach for a robot following the human being. The proposed approach employs a model predictive control that facilitates consideration of several types of upper and lower level constraints a personal robot would require. The effectiveness of our proposed approach was then verified in experiments using a prototype personal robot.     

基于反步法的移动机器人鲁棒跟踪控制

以四轮移动机器人为研究对象,建立了机器人完整的数学模型,包括运动学模型、动力学模型以及驱动电机模型。在机器人数学模型的基础上,采用反步法的思想设计具有全局收敛特性的鲁棒轨迹跟踪控制器,设计中考虑了驱动电机模型使控制器更符合实际控制要求,并将其分解为运动学控制器、动力学控制器以及电机控制器三部分,降低了控制器设计的难度。构造了系统的李雅普诺夫函数,证明了该类型移动机器人在所得控制器作用下,能实现对给定轨迹的全局渐近追踪。仿真实验结果表明基于反步法的控制器是有效的。     

Robust adaptive motion/force control for wheeled inverted pendulums

Previous works for wheeled inverted pendulums usually eliminate nonholonomic constraint force in order to make the control design easier, under the assumption that the friction force from the ground is as large as needed. Nevertheless, such an assumption is unfeasible in practical applications. In this paper, adaptive robust motion/force control for wheeled inverted pendulums is investigated with parametric and functional uncertainties. The proposed robust adaptive controls based on physical properties of wheeled inverted pendulums make use of online adaptation mechanism to cancel the unmodelled dynamics. Based on Lyapunov synthesis, the proposed controls ensure that the system outputs track the given bounded reference signals within a small neighborhood of zero, and guarantee the semi-global uniform boundedness of all closed loop signals. The effectiveness of the proposed controls is verified through extensive simulations.     

Self-tuning output recurrent cerebellar model articulation controller for a wheeled inverted pendulum control

In this study, a model-free self-tuning output recurrent cerebellar model articulation controller (SORCMAC) is investigated to control a wheeled inverted pendulum (WIP). Since the proposed SORCMAC captures the system dynamics, it has superior capability compared to the conventional cerebellar model articulation controller in terms of an efficient learning mechanism and dynamic response. The dynamic gradient descent method is also adopted to adjust the SORCMAC parameters online. Moreover, an analytical method based on a Lyapunov function is proposed to determine the learning rates of the SORCMAC so that the convergence of the system can be guaranteed. Finally, the effectiveness of the proposed control system is verified by simulations of the WIP control. Simulation results show that the WIP can move forward and backward stably with uncertainty disturbance by using the proposed SORCMAC.     

一种轮式倒立摆机器人设计

倒立摆是检验各种控制理论的理想模型,通过它可以判断各类控制算法的有效性和控制性能.为此,结合K60微控制器强大的运算能力和丰富的接口功能,设计了该轮式倒立摆机器人,可以通过它验证各种新型控制算法.硬件上介绍了与姿态控制相关的姿态检测系统和电机驱动单元.软件上介绍了根据系统数学模型设计的互补滤波器、姿态控制器、方向控制器和速度控制器.实验结果表明:该系统具有良好的鲁棒性和稳定性,可以准确地对控制算法的有效性和控制性能进行判断.     

Non-linear stable inversion-based output tracking control for a spherical inverted pendulum

We design an exact output tracking control law for a four degree of freedom spherical inverted pendulum based on the non-linear stable inversion tool proposed by Devasia et al. (1989). The pendulum is a slim cylindrical beam attached to a horizontal plane via a universal joint; the joint is free to move in the plane under the influence of a planar force. The upright position is an unstable equilibrium of the uncontrolled system because of gravity. The objective is to design a controller so that the pendulum can be steered to track some smooth desired translational trajectories while keeping the pendulum tightly around the upright position. The design proceeds in three steps: 1. identification of the internal dynamics; 2. feedforward control design for achievable trajectories; 3. feedback design to stabilize the achievable trajectories. The computer simulations show that the proposed controller can deliver excellent tracking performance.     

Velocity and position control of a wheeled inverted pendulum by partial feedback linearization

In this paper, the dynamic model of a wheeled inverted pendulum (e.g., Segway, Quasimoro, and Joe) is analyzed from a controllability and feedback linearizability point of view. First, a dynamic model of this underactuated system is derived with respect to the wheel motor torques as inputs while taking the nonholonomic no-slip constraints into considerations. This model is compared with the previous models derived for similar systems. The strong accessibility condition is checked and the maximum relative degree of the system is found. Based on this result, a partial feedback linearization of the system is obtained and the internal dynamics equations are isolated. The resulting equations are then used to design two novel controllers. The first one is a two-level velocity controller for tracking vehicle orientation and heading speed set-points, while controlling the vehicle pitch (pendulum angle from the vertical) within a specified range. The second controller is also a two-level controller which stabilizes the vehicle's position to the desired point, while again keeping the pitch bounded between specified limits. Simulation results are provided to show the efficacy of the controllers using realistic data.     

不确定平面二级倒立摆的鲁棒自适应控制

为提高倒立摆控制系统的抗扰动能力,降低其对未建模动态等的敏感度,研究了不确定平面二级倒立摆的鲁棒自适应控制器的设计方法。把倒立摆动力学模型分解为确定和不确定两部分,用一个非线性参数化模糊逻辑系统逼近平面二级倒立摆的不确定动态,采用李雅普诺夫稳定性理论推导出使平面二级倒立摆的状态误差渐近收敛的鲁棒控制器及自适应律。理论分析和仿真结果表明所提出的控制算法是有效的。     

Robust tracking control for wheeled mobile robot based on extended state observer

This paper presents a new control scheme on trajectory tracking of wheeled mobile robot with nonholonomic constraints. Extended state observer is introduced to estimate unknown disturbances and velocity information. A robust tracking controller is designed to implement the accurate trajectory tracking and disturbance compensation. By theoretical, position and velocity tracking errors of wheeled mobile robot are proven uniformly ultimately asymptotically stable. Simulation results are given to illustrate the effectiveness of the developed technique.     

双轮共轴移动式倒立摆动力学建模与状态反馈控制

应用第一类拉格朗日方法对系统进行力学分析,建立了以电机转矩为输入且轮在轴向无滑移的非完整约束下系统的数学模型.双轮共轴移动式倒立摆的运动控制目标是移动式倒立摆在二维平面内按指定的方向和速度运动,同时保持摆杆平衡.利用状态反馈,构造闭环系统的状态方程,通过极点配置求得控制量.仿真结果验证了系统状态方程的正确性和控制方法的合理性.     

倒立摆系统的一种H∞优化控制

在运用H_∞环路成形设计方法时权函数的选择一般是凭经验试凑,不能保证所得控制器综合指标最优;且控制器阶次较高,不便于工程实现和参数调整.鉴于以上问题,提出了基于遗传算法的权函数选取方法,在遗传算法的目标函数里加入对鲁棒性能和时域性能指标的约束,从而得到使控制器综合性能指标最优的权函数,避免了凭经验试凑权函数的盲目性;然后,给出一种用多变量PID控制器逼近此控制器的方法,使所得控制器便于实际运用.最后用此方法对小车倒立摆系统进行仿真,结果表明了该方法的有效性.     

基于非线性干扰观测器的翼伞鲁棒反步跟踪控制

针对干扰条件下的无人翼伞飞行器路径跟踪控制问题,提出一种基于非线性干扰观测器的反馈增益鲁棒反步控制方法.采用二阶跟踪-微分器设计干扰观测器对系统复合干扰进行估计和补偿,设计了反馈增益反步跟踪控制律,通过合理设计增益参数,消除了部分复杂非线性项,避免了虚拟量高阶导数问题,简化了控制器形式.根据Lyapunov理论设计鲁棒反馈补偿项,在保证稳定性的同时提高了系统的鲁棒性.仿真实验结果验证了所提出方法的有效性.     

具有非线性不确定性的高超声速飞行器的 分布式鲁棒反步跟踪控制

本文针对具有外部干扰,参数摄动和非连续未知非线性气动影响的一般高超声速飞行器纵向动力学问题,设计了分布式鲁棒反步跟踪控制器.为了处理复杂的系统,将标准反步控制和信号补偿方法结合起来构成一个"简单"的鲁棒控制器.该方法不仅可以保证闭环系统半全局鲁棒跟踪性能,也可保证系统跟踪误差以期望的收敛速度收敛到期望的误差范围内.最后,带有非线性不确定性,外部干扰和参数扰动的仿真系统说明了该方法的有效性.     

Robust backstepping output tracking control for SISO uncertain nonlinear systems with unknown virtual control coefficients

The output tracking controller design problem is dealt with for a class of nonlinear strict-feedback form systems in the presence of nonlinear uncertainties, external disturbance, unmodelled dynamics and unknown time-varying virtual control coefficients. A new method based on signal compensation is proposed to design a linear time-invariant robust controller, which consists of a nominal controller and a robust compensator. It is shown that the closed-loop control system with a controller designed by the proposed method has robust asymptotical practical tracking property for any bounded initial conditions and robust tracking transient property if all initial states are zero.     

Design and implementation of a block‐backstepping based tracking control for nonholonomic wheeled mobile robot

This paper presents formulation of a novel block‐backstepping based control algorithm to overcome the challenges posed by the tracking and the stabilization problem for a differential drive wheeled mobile robot (WMR). At first, a two‐dimensional output vector for the WMR has been defined in such a manner that it would decouple the two control inputs and, thereby, allow the designer to formulate the control laws for the two inputs one at a time. Actually, the decoupling has been carried out in a way to convert the system into block‐strict feedback form. Thereafter, block‐backstepping control algorithm has been utilized to derive the expressions of the control inputs for the WMR system. The proposed block‐backstepping technique has further been enriched by incorporating an integral action for enhancing the steady state performance of the overall system. Global asymptotic stability of the overall system has been analyzed using Lyapunov stability criteria. Finally, the proposed control algorithm has been implemented on a laboratory scale differential drive WMR to verify the effectiveness of the proposed control law in real‐time environment. Indeed, the proposed design approach is novel in the sense that it has judiciously exploited the nonholonomic constraint of the WMR to result in a reduced order block‐backstepping controller for the WMR, and thereby, it has eventually yielded a compact expression of the control law that is amenable to real‐time implementation. Copyright © 2015 John Wiley & Sons, Ltd.     

拟人控制二维单倒立摆

以二维单极倒立摆为被控对象，利用拟人控制的思想形成非线性控制律，并确定出反馈系数间的相对关系。通过在线调试实现定性控制律的量化，从而成功地控制了二维单级倒立摆的稳定。与传统的控制系统设计相比，不依赖于数学模型，不受线性约束；与模糊控制相比，不需要人类直接被控对象的经验。拟人控制方法设计简单易行，且得到的控制系统具有较强的鲁棒性。     

基于模糊加权的倒立摆混合控制

针对小车倒立摆系统,提出了一种线性状态反馈控制和滑模控制模糊加权的控制方法.滑模控制器的作用是将摆角控制在零的一个邻域内,在此邻域内首先采用近似的线性化模型来描述倒立摆系统,然后采用基于极点配置的方法设计系统的线性状态反馈控制器以使系统的状态稳定在给定值,两个控制器的输出通过加权求和作为倒立摆的控制作用.仿真结果证实了该方法的有效性.