检索结果-内蒙古大学图书馆

On the use of positive feedback for improved torque control

Control Theory and Technology 2015年第3期13卷 266-285页

作者： Houman DALLALI Gustavo A.MEDRANO-CERDA Michele FOCCHI Thiago BOAVENTURA Marco FRIGERIO Claudio SEMINI Jonas BUCHLI Darwin G.CALDWELL Department of Advanced Robotics Istituto Italiano di Tecnologia(IIT) Agile and Dexterous Robotics Lab Institute of Robotics and Intelligent SystemsETH

This paper considers the torque control problem for robots with flexible joints driven by electrical actuators. It is shown that the achievable closed-loop tracking bandwidth using PI torque controllers may be limited due to transmission zeros introduced by the load dynamics. This limitation is overcome by using positive feedback from the load motion in unison with PI torque controllers. The positive feedback is given in terms of load velocity, acceleration and jerk. Stability conditions for designing decentralized PI torque controllers are derived in terms of Routh-Hurwitz criteria. Disturbance rejection properties of the closed system are characterized and an analysis is carried out investigating the use of approximate positive feedback by omitting acceleration and/or jerk signals. The results of this paper are illustrated for a two DoF （degrees of freedom） system. Experimental results for a one DoF system are also included.

关键词： Force-torque control load motion compensation decentralized control

来源：评论

学校读者我要写书评

暂无评论

Online walking motion and foothold optimization for quadruped locomotion

Online walking motion and foothold optimization for quadrupe...

引用

2017 IEEE International Conference on robotics and Automation, ICRA 2017

作者： Winkler, Alexander W. Farshidian, Farbod Neunert, Michael Pardo, Diego Buchli, Jonas Agile and Dexterous Robotics Lab Institute of Robotics and Intelligent Systems ETHZ Zurich Switzerland

ISBN: (纸本)9781509046331

We present an algorithm that generates walking motions for quadruped robots without the use of an explicit footstep planner by simultaneously optimizing over both the Center of Mass (CoM) trajectory and the footholds. Feasibility is achieved by imposing stability constraints on the CoM related to the Zero Moment Point and explicitly enforcing kinematic constraints between the footholds and the CoM position. Given a desired goal state, the problem is solved online by a Nonlinear Programming solver to generate the walking motion. Experimental trials show that the algorithm is able to generate walking gaits for multiple steps in milliseconds that can be executed on a real quadruped robot. © 2017 IEEE.

关键词： Nonlinear programming

来源：评论

学校读者我要写书评

暂无评论

Efficient kinematic planning for mobile manipulators with non-holonomic constraints using optimal control

Efficient kinematic planning for mobile manipulators with no...

引用

2017 IEEE International Conference on robotics and Automation, ICRA 2017

作者： Giftthaler, Markus Farshidian, Farbod Sandy, Timothy Stadelmann, Lukas Buchli, Jonas Agile and Dexterous Robotics Lab Institute of Robotics and Intelligent Systems ETH Zürich Switzerland

ISBN: (纸本)9781509046331

This work addresses the problem of kinematic trajectory planning for mobile manipulators with non-holonomic constraints, and holonomic operational-space tracking constraints. We obtain whole-body trajectories and time-varying kinematic feedback controllers by solving a Constrained Sequential Linear Quadratic Optimal Control problem. The employed algorithm features high efficiency through a continuous-time formulation that benefits from adaptive step-size integrators and through linear complexity in the number of integration steps. In a first application example, we solve kinematic trajectory planning problems for a 26 DoF wheeled robot. In a second example, we apply Constrained SLQ to a real-world mobile manipulator in a receding-horizon optimal control fashion, where we obtain optimal controllers and plans at rates up to 100 Hz. © 2017 IEEE.

关键词： Kinematics

来源：评论

学校读者我要写书评

暂无评论

Design, development and experimental assessment of a robotic end-effector for non-standard concrete applications

Design, development and experimental assessment of a robotic...

引用

2017 IEEE International Conference on robotics and Automation, ICRA 2017

作者： Kumar, Nitish Hack, Norman Doerfler, Kathrin Walzer, Alexander Nikolas Rey, Gonzalo Javier Gramazio, Fabio Kohler, Matthias Daniel Buchli, Jonas The Agile & Dexterous Robotics Lab. The Institute of Robotics and Intelligent Systems ETH Zurich Switzerland The Institute of Technology in Architecture ETH Zurich Switzerland Moog Inc. United States

Despite the recent advances in, and the adoption of robotic technologies in the construction industry, the architectural processes which demand a high degree of geometric freedom still remain largely labour intensive and manual. This is due to the inherent difficulties in robotizing the current implementation of such processes coupled with the lack of alternate robotic technologies. A specific example, which is also the focus of this paper, is that of building a steel reinforced concrete structure, with varying curvature or cross-section. This process still remains rather manual and requires extensive support of customized form-work. In this paper, first we describe an alternate novel robotic fabrication process for building steel wire meshes which act as both reinforcement and formwork. The robotization of such a process is discussed with the use of a previously developed mobile robotic system. Based on the specifications derived from the process, design of a novel custom designed robotic end-effector, enabling this process, is detailed. Automation of the full robotic system comprising the mobile robotic system and the robotic end-effector is discussed from simulation to control. Through experimental evaluation of the robotic system, we demonstrate the ability to fully automate the construction of non-standard steel reinforced steel meshes of varying curvature and cell sizes. © 2017 IEEE.

关键词： Construction industry

来源：评论

学校读者我要写书评

暂无评论

Learning of Closed-Loop Motion Control

Learning of Closed-Loop Motion Control

引用

IEEE/RSJ International Conference on intelligent Robots and systems

作者： Farbod Farshidian Michael Neunert Jonas Buchli Agile & Dexterous Robotics Lab at the Institute of Robotics and Intelligent Systems ETH Zurich Switzerland

ISBN: (纸本)9781479969357

Learning motion control as a unified process of designing the reference trajectory and the controller is one of the most challenging problems in robotics. The complexity of the problem prevents most of the existing optimization algorithms from giving satisfactory results. While model-based algorithms like iterative linear-quadratic-Gaussian (iLQG) can be used to design a suitable controller for the motion control, their performance is strongly limited by the model accuracy. An inaccurate model may lead to degraded performance of the controller on the physical system. Although using machine learning approaches to learn the motion control on real systems have been proven to be effective, their performance depends on good initialization. To address these issues, this paper introduces a two-step algorithm which combines the proven performance of a model-based controller with a model-free method for compensating for model inaccuracy. The first step optimizes the problem using iLQG. Then, in the second step this controller is used to initialize the policy for our PI~2-01 reinforcement learning algorithm. This algorithm is a derivation of the PI~2 algorithm enabling more stable and faster convergence. The performance of this method is demonstrated both in simulation and experimental results.

关键词： Motor Control Controllers Optimization algorithms degraded performance Learning initialization

来源：评论

学校读者我要写书评

暂无评论

Fast trajectory optimization for legged robots using vertex-based ZMP constraints

arXiv

引用

arXiv 2017年

作者： Winkler, Alexander W. Farshidian, Farbod Pardo, Diego Neunert, Michael Buchli, Jonas Agile & Dexterous Robotics Lab Institute of Robotics and Intelligent Systems ETHZ Zurich Switzerland

This paper combines the fast Zero-Moment-Point (ZMP) approaches that work well in practice with the broader range of capabilities of a Trajectory Optimization formulation, by optimizing over body motion, footholds and Center of Pressure simultaneously. We introduce a vertex-based representation of the support-area constraint, which can treat arbitrarily oriented point-, line-, and area-contacts uniformly. This generalization allows us to create motions such quadrupedal walking, trotting, bounding, pacing, combinations and transitions between these, limping, bipedal walking and push-recovery all with the same approach. This formulation constitutes a minimal representation of the physical laws (unilateral contact forces) and kinematic restrictions (range of motion) in legged locomotion, which allows us to generate various motion in less than a second. We demonstrate the feasibility of the generated motions on a real quadruped robot. Copyright © 2017, The Authors. All rights reserved.

关键词： Aerodynamics

来源：评论

学校读者我要写书评

暂无评论

Numerical search for local (partial) differential flatness

Numerical search for local (partial) differential flatness

引用

IEEE/RSJ International Conference on intelligent Robots and systems

作者： Carmelo Sferrazza Diego Pardo Jonas Buchli Agile Dexterous Robotics Lab at the Institute of Robotics and Intelligent Systems ETH Zurich Switzerland

ISBN: (纸本)9781509037636

Differential flatness is a property of certain systems that greatly simplifies the generation of optimal and dynamically feasible trajectories. Using a differentially flat model, there is no need to integrate the system dynamics to retrieve the states and the constraints of the optimization problem are simpler. Recently, the concept of partial differential flatness has been introduced covering a broader class of systems. In particular, it allows to reduce the need for integration by limiting it to a subset of the states. However, finding an analytical expression for the (partial) differential flatness requires the manipulation of the equations of motion in a very specific manner such that a series of properties are fulfilled. In general, finding such analytical model is not straightforward nor compatible with algorithmic models. In order to tackle this problem, in this paper we present a numerical method to find a (partially) differentially flat model of a system around a collection of states and inputs trajectories. We present results on three underactuated nonlinear systems (cart-pole, planar ballbot and a 3D quadrotor). As use case examples, we show online trajectory re-planning tasks. The validity of the trajectories obtained with the locally flat models is verified by forward integrating the original equations of motion together with an optimal stabilizer.

关键词： Trajectory Mathematical model Numerical models Robots Optimization Analytical models System dynamics

来源：评论

学校读者我要写书评

暂无评论

Nonlinear disturbance attenuation control of hydraulic robotics

Nonlinear disturbance attenuation control of hydraulic robot...

引用

IEEE International Conference on robotics and Biomimetics

作者： Peng Lu Timothy Sandy Jonas Buchli Agile & Dexterous Robotics Lab at the Institute of Robotics and Intelligent Systems ETH Zürich Switzerland

ISBN: (纸本)9781728103785;9781728103778

This paper presents a novel nonlinear disturbance rejection control for hydraulic robots. This method requires two third-order filters as well as inverse dynamics in order to estimate the disturbances. All the parameters for the third-order filters are pre-defined. The proposed method is nonlinear, which does not require the linearization of the rigid body dynamics. The estimated disturbances are used by the nonlinear controller in order to achieve disturbance attenuation. The performance of the proposed approach is compared with existing approaches. Finally, the tracking performance and robustness of the proposed approach is validated extensively on real hardware by performing different tasks under either internal or both internal and external disturbances. The experimental results demonstrate the robustness and superior tracking performance of the proposed approach.

关键词： Actuators Adaptation models Attenuation Robustness Friction Robot sensing systems

来源：评论

学校读者我要写书评

暂无评论

Efficient kinematic planning for mobile manipulators with non-holonomic constraints using optimal control

arXiv

引用

arXiv 2017年

作者： Giftthaler, Markus Farshidian, Farbod Sandy, Timothy Stadelmann, Lukas Buchli, Jonas Agile & Dexterous Robotics Lab Institute of Robotics and Intelligent Systems ETH Zürich Switzerland

关键词： Manipulators

来源：评论

学校读者我要写书评

暂无评论

A projection approach to equality constrained iterative linear quadratic optimal control

A projection approach to equality constrained iterative line...

引用

IEEE-RAS International Conference on Humanoid Robots

作者： Markus Giftthaler Jonas Buchli Agile & Dexterous Robotics Lab Institute of Robotics and Intelligent Systems ETH Zürich Switzerland

ISBN: (纸本)9781538646793

This paper presents a state and state-input constrained variant of the discrete-time iterative Linear Quadratic Regulator (iLQR) algorithm, with linear time-complexity in the number of time steps. The approach is based on a projection of the control input onto the nullspace of the linearized constraints. We derive a fully constraint-compliant feedforward-feedback control update rule, for which we can solve efficiently with Riccati-style difference equations. We assume that the relative degree of all constraints in the discrete-time system model is equal to one, which often holds for robotics problems employing rigid-body dynamic models. Simulation examples, including a 6 DoF robotic arm, are given to validate and illustrate the performance of the method.

关键词： Optimal control Manganese Robots System dynamics Mathematical model Heuristic algorithms Trajectory

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：