Swing-up control strategies for a reaction wheel pendulum

Control of a reaction wheel pendulum, a prototype of an under-actuated system, is easily done using switching control strategies, which combines swing-up control and balancing control schemes. In this article, two novel swing-up control strategies for a reaction wheel pendulum have been proposed. The first swing-up control strategy treats the oscillations of the pendulum as perturbations from the bottom equilibrium point. The second swing-up control is based on interconnection and damping assignment-passivity based control (IDA-PBC). IDA-PBC preserves Euler Lagrangian structure of the system and gives more physical insight about any mechanical system. Any balancing controller can be coupled with the proposed swing-up control strategies to stabilise the pendulum at the top unstable equilibrium position. The control task of balancing the pendulum in top upright position is completed by switching from swing-up scheme to the balancing scheme at the point where the pendulum is very near to the top equilibrium point. Proposed swing-up control strategies have been implemented in real time in switching mode. The two proposed swing-up control schemes provide fast responses as compared to existing energy based schemes.     

An experiment with swinging up a double pendulum using feedback control

Experimental results with swinging up a double pendulum using a bang-bang control torque exerted about the suspension point are presented. In the course of the experiment, the feedback control brings the double pendulum into the vicinity of the upper equilibrium state. The algorithm is based on the decomposition method, and it is fairly simple.     

基于能量反馈的圆轨倒立摆摆起控制

基于拉格朗日方程建立圆轨倒立摆单摆模型,根据能量反馈控制理论,设计圆轨倒立摆摆起控制器,从而使摆杆从稳定平衡点摆起到不稳定平衡点并稳定不倒。采用具有流水线指令结构CIP-51控制器内核的C8051单片机实现控制算法。实验结果表明,采用能量反馈控制器可以对具有复杂非线性、强耦合、自然不稳定特性的倒立摆系统实现摆起控制,摆起效果良好。同时也为其他非线性多变量系统的控制提供了有效方法。     

基于快速起摆的Furuta摆切换控制系统

针对由一个驱动臂和一个未驱动摆杆组成的欠驱动Furuta摆系统,设计了实现其稳定的切换控制系统.控制任务是将未驱动摆杆稳定在上方不稳定平衡点的同时,将驱动臂控制到零点,分为两部分:首先基于部分反馈线性化技术设计一个饱和的状态反馈控制器,将摆杆快速控制到上方不稳定平衡点附近;然后切换到一个线性的全状态反馈控制器,实现系统的稳定控制.仿真实验验证了控制器的有效性.     

Stabilization of the inverted spherical pendulum via Lyapunov approach

In this paper a nonlinear controller is presented for the stabilization of the spherical inverted pendulum system. The control strategy is based on the Lyapunov approach in conjunction with LaSalle's invariance principle. The proposed controller is able to bring the pendulum to the unstable upright equilibrium point with the position of the movable base at the origin. The obtained closed‐loop system has a very large domain of attraction, that can be as large as desired, for any initial position of the pendulum which lies above the horizontal plane. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Pendubot: combining of energy and intuitive approaches to swing up,stabilization in erected pose

The objective of this paper is to define a strategy for the swing up of a double-link pendulum and its stabilization in the unstable equilibrium state with both erected links. The first joint of this double-link pendulum, which is the suspension joint, is actuated and the second joint is passive. This double-link pendulum, usually called pendubot, is an underactuated system. The double-link pendulum is straightened during the energy boosting process. The swing up control switches to the balancing mode at the instant when the system comes to the basin of attraction. The limits on the torque amplitude are taken into account. The gains of the saturated balancing control are chosen to ensure the basin of attraction as large as possible. Simulation results demonstrate that our strategy is efficient.     

Analysis of the energy‐based swing‐up control for the double pendulum on a cart

Designing and analyzing controllers for mechanical systems with underactuation degree (difference between the number of degrees of freedom and that of inputs) greater than one is a challenging problem. In this paper, for the double pendulum on a cart, which has three degrees of freedom and only one control input, we study an unsolved problem of analyzing the energy‐based swing‐up control which aims at controlling the total mechanical energy of the cart‐double‐pendulum system, the velocity and displacement of the cart. Under the energy‐based controller, we show that for all initial states of the cart‐double‐pendulum system, the velocity and displacement of the cart converge to their desired values. Then, by using a property of the mechanical parameters of the double pendulum, we show that if the convergent value of the total mechanical energy is not equal to the potential energy at the up–up equilibrium point, where two links are in the upright position, then the system remains at the up–down, down–up, and down–down equilibrium points, where two links are in the upright–down, down–upright, and down–down positions, respectively. Moreover, we show that each of these three equilibrium points is strictly unstable in the closed‐loop system by showing that the Jacobian matrix valued at each equilibrium point has at least one eigenvalue in the open right half plane. This shows that for all initial states with the exception of a set of Lebesgue measure zero, the total mechanical energy converges to the potential energy at the up–up equilibrium point. This paper provides insight into the energy‐based control approach to mechanical systems with underactuation degree greater than one. Copyright © 2010 John Wiley & Sons, Ltd.     

On some time-optimal problems for pendulum systems

The problem of time-optimal swinging of a double pendulum with the upper suspension point (and some other pendulum-type mechanical systems) from the stable lower position into the unstable upper position is solved. The angle between the links or, more precisely, the angular velocity of this angle is controlled. This angular velocity and the angle itself can vary within bounded intervals.     

Design of optimized fuzzy cascade controllers by means of Hierarchical Fair Competition-based Genetic Algorithms

In this study, we present a design of an optimized fuzzy cascade controller based on Hierarchical Fair Competition-based Genetic Algorithms (HFCGA) for a rotary inverted pendulum system. In this system, one controls the movement of a pendulum through the adjustment of a rotating arm. The objective is to control the position of the rotating arm and to make the pendulum maintain the unstable equilibrium point at vertical position. To control the system, we design a fuzzy cascade controller scheme which consists of two fuzzy controllers arrange in a cascaded topology. The parameters of the controller are optimized by means of the HFCGA algorithm. The fuzzy cascade scheme comprises two controllers located in two loops. An inner loop controller governs the position of the rotating arm while an outer controller modifies a set point of the inner controller implied by the changes of the angle of pendulum. The HFCGA being a computationally effective scheme of the Parallel Genetic Algorithm (PGA) has been developed to eliminate an effect of premature convergence encountered in Serial Genetic Algorithms (SGA). It has emerged as an effective optimization vehicle to deal with very large search spaces. A comparative analysis involving computing simulations and practical experiment demonstrates that the proposed HFCGA based fuzzy cascade controller comes with superb performance in comparison with the conventional Linear Quadratic Regulator (LQR) controller as well as HFCGA-based PD cascade controller.     

Dynamics and stabilization of a spherical inverted pendulum on a wheeled cart

This paper studies a stabilization problem of an inverted spherical pendulum on a wheeled cart assuming that pure rotation of cart cannot move support of pendulum. It is shown that in spite of nonholonomic constraints of wheels and the above geometric condition on pendulum support the pendulum can be locally stabilizable at a certain non-static equilibrium point by applying a standard linearization approach. Furthermore it is shown that equilibrium points can be chosen to make cart move to a given location. Numerical simulations are performed to confirm theoretical findings and illustrate interesting dynamics of closed loop pendulum system.     

Bringing a multilink pendulum to the equilibrium position using a single control torque

The problem of controlling the multilink pendulum in the neighborhood of a given equilibrium position is considered. A feedback control bringing the pendulum to the equilibrium position in a finite time using a bounded torque applied to the first link is constructed. The proposed approach is based on stability theory of motion and uses the concept of the Lyapunov function that is common for two different stable systems of differential equations. The efficiency of the control is demonstrated by a computer simulation of the three-link pendulum dynamics.     

van der Pol型自激单摆的张弛振荡特性

含van der Pol型自激项的单摆系统是典型的自激机械系统,本文研究了该系统的张弛振荡特性.首先通过引入新的时间尺度和变量,把原系统表示成标准的快慢系统.然后基于几何奇异摄动理论,求得系统的慢变流形及其结构,从而证明了张弛振荡解的存在性,并进一步求得了张弛振荡解及其周期的近似表达式.理论结果表明,发生张弛振荡时,单摆快速通过其平衡位置,而在远离平衡位置的一段区域上停留较长时间,且存在两个分界点把快速运动和慢速运动分隔开.数值算例证明了理论分析的正确性.     

内共振关系对弹簧摆动力学行为的影响

基于数值方法,以弹簧摆为对象,讨论了不同的内共振关系对一类平方、立方非线性系统动力学行为的影响.结果表明,对1∶1内共振的情况,两个模态的振动均可能发生在偏离原来平衡位置的新的平衡位置附近,即出现平衡位置飘移的现象.能量可以从低阶(摆动)模态传递到高阶(呼吸)模态,但不能从高阶(呼吸)模态传递到低阶(摆动)模态.然而对...     

非线性倒立摆系统平衡点反馈控制参数的优化计算

本文基于圆轨倒立摆非线性系统模型,建立了平衡点状态反馈控制参数的高精度优化算法,编制计算程序确定出反馈控制参数,并对圆轨倒立摆平衡点的实例控制.与将系统线性化后的反馈参数的计算分析相比,本文研究方法具有较大平衡范围.仿真与实例平衡控制都表明了本文研究方法的可行性.     

Stabilization of the Furuta pendulum around its homoclinic orbit

We present an energy based control approach to control the Furuta pendulum. A controller is proposed for swinging the pendulum and raise it to its uppermost unstable equilibrium position. The passivity properties of the system are used as a guideline in the control strategy. The stability analysis is carried out by using a Lyapunov technique.     

A machine-vision system to measure the parameters describing the performance of a Foucault pendulum

We describe a machine-vision system that makes real-time measurements of the kinematics of a Foucault pendulum. Images are taken from a downward-facing camera placed close to the pendulum suspension point. The bob is detected via background subtraction and located by fitting circles to the resulting contour segments. The bob trajectory is then modelled by fitting ellipses to recent positions. Parameters are improved through Kalman filtering. Experimental results are shown. Our implementation is a robust and accurate tool for visualization of the pendulum kinematics as well as troubleshooting and maintenance of the mechanical elements.     

环型二级倒立摆的控制研究与实现

通过分析环型二级倒立摆系统的动力学特性,将系统的状态空间方程在“倒立”的 平衡点附近进行线性化处理,应用线性二次型最优控制策略,对环型二级倒立摆进行控制器 的设计与仿真实验,并成功地将所设计的控制器应用到实际的环型二级倒立摆系统上,使其 稳定地平衡在“倒立”状态．所做应用与实际实验在国内尚未见到报道．     

A nonlinear hybrid controller for swinging-up and stabilizing the Furuta pendulum

The conventional switching strategy for solving the inverted pendulum control problem is based on two steps: swinging-up and stabilization. In this note, first, a new strategy for swinging the Furuta pendulum up towards the desired upright position is designed using the Speed-Gradient method, which uses only directly measured coordinates. Then, a nonlinear controller, based on the Forwarding approach, stabilizes the upright position. As a new contribution the latter leads to a nonlinear stabilizer around the upright position, whose Lyapunov function yields a larger size estimation of the domain of attraction than the one obtained with the traditional linear approach. This estimation allows us to use it in a global switching strategy in the practical implementation and guarantees almost-global asymptotic stability of the equilibrium. Successful experimental results are reported with the available laboratory Furuta pendulum.     

Stabilization of the inverted pendulum around its homoclinic orbit

The inverted pendulum has been used as a benchmark for motivating the study of nonlinear control techniques. We propose a simple controller for balancing the inverted pendulum and raise it to its upper equilibrium position while the cart displacement is brought to zero. The control strategy is based on an energy approach of the cart and pendulum system.     

Asymptotic Smooth Stabilization of the Inverted 3-D Pendulum

The 3-D pendulum consists of a rigid body, supported at a fixed pivot, with three rotational degrees of freedom; it is acted on by gravity and it is fully actuated by control forces. The 3-D pendulum has two disjoint equilibrium manifolds, namely a hanging equilibrium manifold and an inverted equilibrium manifold. The contribution of this paper is that two fundamental stabilization problems for the inverted 3-D pendulum are posed and solved. The first problem, asymptotic stabilization of a specified equilibrium in the inverted equilibrium manifold, is solved using smooth and globally defined feedback of angular velocity and attitude of the 3-D pendulum. The second problem, asymptotic stabilization of the inverted equilibrium manifold, is solved using smooth and globally defined feedback of angular velocity and a reduced attitude vector of the 3-D pendulum. These control problems for the 3-D pendulum exemplify attitude stabilization problems on the configuration manifold SO(3) in the presence of potential forces. Lyapunov analysis and nonlinear geometric methods are used to assess global closed-loop properties, yielding a characterization of the almost global domain of attraction for each case.