考虑摆动腿动态的变长度柔性双足机器人步态切换控制研究

弹簧负载倒立摆模型是一种典型的双足行走模型,已经成为研究机器人类人行走的基础。本文在此模型的基础上进行了扩展,通过添加刚性躯干、脚质量及采用变长度伸缩腿,充分考虑了躯干及摆动腿动力学对机器人行走步态的影响。首先,利用欧拉–拉格朗日法推导了动力学方程。其次,设计了反馈线性化控制器来跟踪目标轨迹,以及调节摆动腿和躯干的姿态。第三,提出了步态切换策略,通过控制腿部长度和髋关节力矩来实现步态切换,从而改变平均行走速度。最后,通过计算机仿真验证了该方法的有效性。仿真结果表明：该控制策略能够有效地跟踪系统的期望轨迹及实现两种自然步态之间的切换,并形成稳定的极限环,实现机器人的稳定行走。

     

机器人关节非线性摩擦模型关键参数反求

机器人关节非线性摩擦的准确描述对提高机器人轨迹精度、定位精度及其可靠性等具有重要理论意义和科学价值. 然而, 机器人关节通常包含电机、减速器、驱动器和传感器, 是一个复杂的机电耦合系统, 随服役时间及工况的变化, 机器人关节的摩擦参数也存在显著时变效应, 难以准确描述, 造成轨迹精度下降, 为机器人后期精度维护造成巨大困难. 因此, 本文定量评价了摩擦参数对机器人输出力矩的影响, 提出考虑时变效应的机器人关节非线性摩擦参数反求方法. 首先, 建立机器人关节一般非线性摩擦模型. 设计机器人关节恒速跟踪实验, 通过卡尔曼滤波对实验采集的数据进行处理, 进而建立关节速度和驱动电机电流之间的关系, 完成关节一般非线性摩擦模型建立. 其次, 择取非线性摩擦模型关键参数. 建立包含非线性摩擦的机器人动力学模型, 基于激励轨迹计算各关节力矩, 并对其开展灵敏度分析, 择取对关节力矩灵敏性较高的摩擦参数. 再次, 建立关节输出力矩和摩擦参数一一对应的数据集. 基于实际工况构建摩擦参数取值空间, 采用最优拉丁超立方法对摩擦参数采样, 并将其代入机器人动力学模型计算出相应的力矩, 从而求得关节输出力矩和摩擦参数一一对应的数据集. 最后, 建立反问题神经网络并对其进行训练, 实现非线性摩擦模型关键参数反求, 并进行验证. 研究结果表明关节非线性摩擦的准确描述减小了机器人低速运动换向时摩擦力矩突变对机器人轨迹的影响, 显著提升了机器人轨迹精度.      

考虑摩擦特性的柔性关节空间机器人自适应CMAC神经网络鲁棒控制

讨论了关节摩擦力矩影响下,具有柔性铰关节的漂浮基空间机器人系统的动力学控制问题.设计了基于高斯基函数的小脑神经网络(CMAC)鲁棒控制器和摩擦力矩补偿器.用奇异摄动理论对系统的动力学模型进行快慢变子系统分解,针对快变子系统,设计力矩微分反馈控制器来抑制机械臂关节柔性引起的振动;对于慢变子系统,设计了基于自适应CMAC神...     

变长度弹性伸缩腿双足机器人动力学与控制

研究了半被动双足机器人的平面稳定行走的控制问题．基于弹簧质点模型，采用拉格朗日方法分别得到双足机器人单支撑阶段与双支撑阶段的动力学方程，对机器人系统的动力学方程求得周期解．应用非线性系统状态反馈线性化理论，在双足机器人的单支撑阶段和双支撑阶段中，通过控制双足机器人的腿长度，实现稳定的周期行走．在理论分析的基础上，对控制算法进行了仿真与研究．结果表明：在周期行走过程中，文中采用的变长度控制算法可以使双足机器人克服外界的干扰，并具有较强的抗干扰性．     

The experimental study on the contact process of passive walking

The passive dynamic walking is a new concept of biped walking. Researchers have been working on this area with both theoretical analysis and experimental analysis ever since McGeer. This paper presents our compass-like passive walking model with a new set of testing system. Two gyroscopes are used for measuring the angles of two legs, and ten FlexiForce sensors are used for measuring the contact forces on the feet. We got the experimental data on the passive walking process with the validated testing system. A great emphasis was put on the contact process between the feet and the slope. The contact process of the stance leg was divided into four sections, and differences between the real testing contact process and the classic analytical contact process with no bouncing and slipping were summarized.     

踝关节外骨骼人机耦合动力学与助力性能分析

踝关节在人体下肢运动过程中提供了最大的关节力矩, 因此在下肢增强型外骨骼的研究中, 踝关节外骨骼受到了重点关注. 穿戴外骨骼的人体的行走是典型的动力学问题, 但目前人机耦合动力学的相关研究还处于早期阶段. 本文以绳驱踝关节外骨骼为研究对象, 融合机器人正运动学方法和拉格朗日方程建立了考虑足?地交互力、人体关节力矩和外骨骼力矩的人?机耦合动力学模型. 模型中, 足?地交互力由Kelvin-Voigt模型结合库伦摩擦模型描述, 人体关节力矩由基于粒子群优化的PD控制生成, 外骨骼期望力矩由上层控制器依据人体步态周期确定. 通过基于模型的动力学仿真, 本文从人体踝关节角度、踝关节力矩、踝关节功率和踝关节做功多个角度系统分析了踝关节外骨骼对人体行走的助力效果. 研究表明, 在2.0 km/h到6.5 km/h的人体步行速度下, 穿戴外骨骼可以实现至少24.84%的人体踝关节平均力矩下降和至少24.69%的踝关节做功下降. 本文也开展了基于SCONE平台的肌肉骨骼建模和预测仿真. 仿真结果表明, 在3.6 km/h的步行速度下, 穿戴外骨骼可以有效降低比目鱼肌的激活度峰值, 并使肌电信号的RMS值下降了6.21%, 从而从生理学的角度证实了踝关节外骨骼的助力效果. 本文的结果进一步完善了人体下肢?外骨骼耦合系统的动力学建模和分析方法, 从动力学和生理学角度证实和解释了踝关节外骨骼对行走的助力机制, 也为今后下肢外骨骼的实验研究提供了理论支撑.      

Efficient parametric excitation walking with delayed feedback control

In passive dynamic walking proposed by McGeer, mechanical energy lost by heel strike is restored by transporting potential energy to kinetic energy as walking down a slope. When energy input is larger as a slope is steeper, the bifurcation of a walking cycle occurs. In the parametric excitation walking, which is to realize passive dynamic-like walking on the level ground, the bifurcation of a walking cycle has also been observed when walking speed is fast. Recently, Asano et al. have shown that bifurcation exerts an adverse influence upon walking performance by using a rimless wheel model. In this paper, we apply the delayed feedback control (DFC), originally used in chaos control, to parametric excitation walking to suppress bifurcation. We show in numerical simulation that the proposed method makes period-two walking to period-one walking, and improves energy efficiency. In addition, the proposed method can generate a sustainable gait in the region where a biped robot cannot walk without DFC. The analyses using a Poincaré map reveal that period-one walking with DFC corresponds to an unstable periodic orbit and reveal that a robot model in this paper satisfies the sufficient condition of applicability of DFC.     

变刚度半被动双足机器人行走的仿人控制1)

研究了变刚度半被动双足机器人行走控制问题。采用仿人的行走控制策略,使用变刚度双足弹簧负载倒立摆模型,利用模型自稳定性,在双支撑阶段调整后腿刚度使机器人的能量保持在期望能量附近,在单支撑阶段调整摆动腿落地位置控制质点的高度和前向速度。仿真结果表明：本文采用的控制策略可以实现双足机器人在水平面上的稳定行走,无扰动时可以使机器人实现零输入的被动周期行走,有外部扰动时腿部变刚度控制可使机器人总能量恢复平衡并重新进入稳态行走,控制系统具有鲁棒性。     

HUMAN-LIKE CONTROL FOR SEMI-PASSIVE BIPEDAL ROBOT WALKING WITH VARIABLE LEG STIFFNESS1)

研究了变刚度半被动双足机器人行走控制问题。采用仿人的行走控制策略,使用变刚度双足弹簧负载倒立摆模型,利用模型自稳定性,在双支撑阶段调整后腿刚度使机器人的能量保持在期望能量附近,在单支撑阶段调整摆动腿落地位置控制质点的高度和前向速度。仿真结果表明：本文采用的控制策略可以实现双足机器人在水平面上的稳定行走,无扰动时可以使机器人实现零输入的被动周期行走,有外部扰动时腿部变刚度控制可使机器人总能量恢复平衡并重新进入稳态行走,控制系统具有鲁棒性。     

基于步态切换的欠驱动双足机器人控制方法

由于高维、非线性、欠驱动等特点, 3-D双足机器人的稳定性控制依然是一个研究难点. 一些传统的控制方法, 如基于事件的反馈控制方法和PD控制方法, 抗扰动能力较弱, 鲁棒性较差. 通过观察, 人类受到外部扰动影响时, 会通过调整步态重新获得稳定性,相较之下仅依靠一个步态获得的稳定性是有限的. 受此启发, 本文针对上述问题提出一种基于步态切换的欠驱动3-D双足机器人控制方法. 首先, 以能耗最少为优化目标, 通过非线性优化方法预先设计多组不同步长、步速的步态作为参考步态, 以构建一个步态库; 然后, 通过综合考虑步态切换过程中的稳定性与能效, 建立了多目标步态切换函数; 最后, 将该步态切换函数作为优化目标, 并求解该最小化问题获得下一步的参考步态, 从而实现步态切换, 达到使用步态库?多轨迹方法来提高鲁棒性的目的. 在仿真实验中运用该步态切换控制方法, 欠驱动3-D双足机器人可实现相对高度在[-20, 20] mm内随机变化的不平整地面上行走, 而仅采用单步态控制策略则无法克服这样的外部扰动, 从而说明了基于步态切换的欠驱动双足机器人控制方法的有效性.      

基于干扰观测器的柔性关节空间机器人退步自适应控制

研究了载体位置、姿态均不受控的情况下,系统参数不确定的柔性关节空间机器人轨迹跟踪的控制问题.结合系统动量、动量矩守恒关系,利用拉格朗日法推导出系统的动力学模型.为减小系统柔性关节对系统控制精度的影响,采用关节柔性补偿器来等效降低系统关节的柔性.再借助奇异摄动法,针对系统参数不确定的情况,设计了柔性关节空间机器人基于干扰观测器的退步自适应滑模控制方案.该方案不需要对系统惯性参数进行线性化处理,控制器结构简单,且实现了空间机器人期望轨迹的精确跟踪控制.通过平面两杆空间机器人的数值仿真证明了该方法的有效性.     

Self-stability of a simple walking model driven by a rhythmic signal

In this paper, we analyzed the dynamic properties of a simple walking model of a biped robot driven by a rhythmic signal from an oscillator. The oscillator receives no sensory feedback and the rhythmic signal is an open loop. The simple model consists of a hip and two legs that are connected at the hip. The leg motion is generated by a rhythmic signal. In particular, we analytically examined the stability of a periodic walking motion. We obtained approximate periodic solutions and the Jacobian matrix of a Poincaré map by the power-series expansion using a small parameter. Although the analysis was inconclusive when we used only the first order expansion, by employing the second order expansion it clarified the stability, revealing that the periodic walking motion is asymptotically stable and the simple model possesses self-stability as an inherent dynamic characteristic in walking. We also clarified the stability region with respect to model parameters such as mass ratio and walking speed.     

高自由度双足机器人数学模型及步行控制研究

基于ZMP理论及位姿矩阵,采用了相对重心以及相对坐标系的数学描述方法,对17自由度双足机器人步行稳定性控制进行数学建模研究．所建立的数学模型能够描述机器人稳定性控制．并经过Matlab数学计算和仿真研究,验证了所建立的模型可以描述双足机器人的步行规律,在理论上达到了双足机器人步行稳定性的控制目的．最后通过VC 把整个模型封装成一个可视化系统,便于将所研究的模型应用到实际的控制中,为未来机器人的实时控制的研究提供了技术支持．     

Treadmill walking of the pneumatic biped Lucy: Walking at different speeds and step-lengths

Actuators with adaptable compliance are gaining interest in the field of legged robotics due to their capability to store motion energy and to exploit the natural dynamics of the system to reduce energy consumption while walking and running. To perform research on compliant actuators we have built the planar biped Lucy. The robot has six actuated joints, the ankle, knee and hip of both legs with each joint powered by two pleated pneumatic artificial muscles in an antagonistic setup. This makes it possible to control both the torque and the stiffness of the joint. Such compliant actuators are used in passive walkers to overcome friction when walking over level ground and to improve stability. Typically, this kind of robots is only designed to walk with a constant walking speed and step-length, determined by the mechanical design of the mechanism and the properties of the ground. In this paper, we show that by an appropriate control, the robot Lucy is able to walk at different speeds and step-lengths and that adding and releasing weights does not affect the stability of the robot. To perform these experiments, an automated treadmill was built Published in Prikladnaya Mekhanika, Vol. 44, No. 7, pp. 134–142, July 2008.     

TRAJECTORY TRACKING CONTROL FOR DUAL-ARM SPACE ROBOT WITH BOUNDED INPUT TORQUES

讨论基座姿态、位置均不控的自由漂浮双臂空间机器人在关节驱动力矩受限下其关节协调运动的控制问题. 运用拉格朗日第二类方程并耦合动量守恒关系建立动力学方程. 尔后,设计了基于饱和函数的控制方案,该方案引入具有饱和特性的双曲正切函数来控制关节力矩幅值. 最后,根据奇异扰动系统稳定性理论将系统分为降阶系统和边界层系统,分别利用李雅普诺夫函数证明其在原点呈指数稳定. 数值仿真进一步表明该方案的有效性和优越性.     

驱动力矩受限下双臂空间机器人轨迹跟踪控制

讨论基座姿态、位置均不控的自由漂浮双臂空间机器人在关节驱动力矩受限下其关节协调运动的控制问题. 运用拉格朗日第二类方程并耦合动量守恒关系建立动力学方程. 尔后,设计了基于饱和函数的控制方案,该方案引入具有饱和特性的双曲正切函数来控制关节力矩幅值. 最后,根据奇异扰动系统稳定性理论将系统分为降阶系统和边界层系统,分别利用李雅普诺夫函数证明其在原点呈指数稳定. 数值仿真进一步表明该方案的有效性和优越性.     

Trajectory planning and tracking control for autonomous bicycle robot

Control of the autonomous bicycle robot offers considerable challenges to the field of robotics due to its nonholonomic, underactuated, and nonminimum-phase properties. Furthermore, instability and complex dynamic coupling make the trajectory planning of the bicycle robot even more challenging. In this paper, we consider both trajectory planning and tracking control of the autonomous bicycle robot. The desired motion trajectory of the contact point of the bicycle’s rear wheel is constructed using the parameterized polynomial curve that can connect two given endpoints with associated tangent angles. The parameters of the polynomial curve are determined by minimizing the maximum of the desired roll angle’s equilibrium of the bicycle, and this optimization problem is solved by the particle swarm optimization algorithm. Then, a control scheme that can achieve full-state trajectory tracking while maintaining the bicycle’s balance is proposed by combining a planar trajectory tracking controller with a roll angle balance controller. Simulation results are presented to demonstrate the effectiveness of the proposed method.     

LIE SYMMETRIES AND CONSERVED QUANTITY OF A BIPED ROBOT

I. INTRODUCTION It is well known there are close relationships between the symmetries and conservation laws inmechanical systems. The symmetric principles are among the key issues in mechanics. Two e?ectivemethods of studying the symmetries and conservation laws of mechanical are Noether’s method[1] andLie’s method. The approach to Lie symmetries was reported in the 19th century, but no applicationin mechanics appeared until 1979[2]. In recent years, studies of Lie’s method have be…     

Discriminating on dynamical stability of biped walking

In paper, a biped with 7 rigids and 12 degrees of freedom is taken as a research mould. The discriminating conditions on dynamical walking stability are derived and discussed in detail. The discriminating condition could be used to check biped motive planning and to modify it.     

A passive-biped model with multiple routes to chaos

This paper presents a new passive-biped model consisting of a simplest walking model beneath an upper body, with no kinematic constraint. The upper body is attached to the legs with a linear torsional spring. The model is a passive dynamic walker, so it walks down a slope without energy input. The governing equations of motion are derived and simulated for the parameter analysis purposes. Simulation results reveal some different routes to chaos that have not been observed in previous models.