A stable transition controller for constrained robots

Abstract-The problem of prescribing, reducing, or controlling the interaction forces between a robot and the environment during a noncontact-to-contact transition is intriguing because large interaction forces can damage both the robot and/or the environment or lead to degraded performance or instabilities. In this paper, we consider a two-link planar robotic arm that transitions from free motion to contact with an unactuated mass-spring system. The objective is to control a robot from a noncontact initial condition to a desired (in-contact) position so that the mass-spring system is regulated to a desired compressed state. The feedback elements for the controller in this paper are contained inside hyperbolic tangent functions as a means to limit the impact forces resulting from large initial conditions as the robot transitions from a noncontact to contact state. The main challenge of this work is that the use of saturated feedback does not allow some coupling terms to be canceled in the stability analysis, resulting in the need to develop state-dependent upper bounds that reduce the stability to a semiglobal result. New control development, closed-loop error systems, and Lyapunov-based stability analysis arguments are used to conclude the result. It is interesting to note that only the position and velocity terms are required for the proposed controller (i.e., the controller does not depend on measuring the impact force and the acceleration terms). Experimental results that successfully demonstrate the control objective are provided.

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“…The inertia matrix is symmetric, positive definite, and can be lower and upper bounded as (9) where and are positive constants.…”

Section: ) Propertymentioning

confidence: 99%

A force limiting adaptive controller for a robotic system undergoing a non-contact to contact transition

Liang

Bhasin

Dupree

et al. 2007

2007 46th IEEE Conference on Decision and Control

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“…A two degree-of-freedom (DOF) planar manipulator was globally asymptotically regulated to contact an infinitely rigid and massive surface by Tornambe [23] where the impact force was estimated using a reducedorder observer. Pagilla and Yu [24] proposed a stable transition controller to deal with the transition from a non-contact to a contact state which can improve transition performance and force regulation. Hyde and Cutkosky [25] proposed an approach, based on input command shaping, to suppress vibration during the contact transition of switching controllers by modifying feedforward information.…”

Section: Introductionmentioning

confidence: 99%

Lyapunov-based control of a robot and mass-spring system undergoing an impact collision

Dupree

Dixon

et al. 2006

2006 American Control Conference

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To my wife Yen-Chen and son Hsu-Chen who constantly filled me with love and joy. ACKNOWLEDGMENTSI would like to express my gratitude to my advisor, mentor, and friend, Dr.Warren E. Dixon for introducing me with the interesting field of Lyapunov-based control. As an advisor, he provided the necessary guidance and allowed me to try some stupid ideas during my research. As a mentor, he helped me understand the high pressure of working in a professional environment and was willing to give me time to learn and adjust. I feel fortunate in getting the opportunity to work with him.

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“…Since the mass is to be controlled in the direction normal to the tissue surface, it is only required that be chosen such that the robot impacts the tissue surface. The closed-loop error system for the mass can be developed by substituting (17) into (16) as (19) Adding and subtracting to (19), and then using the Taylor series approximation in (12), the following expression for the closed-loop mass error system can be obtained (20) where the notation and is introduced in (12), and is defined as 1 The initial weights are selected in some compact set, then new estimates are generated based on the weight update laws in (18). If the weights on the boundary of the set are found to be directed outside the compact set, they are projected back into the set using a smooth projection algorithm (see [27], [28] for details).…”

Section: Closed-loop Error Systemmentioning

confidence: 99%

“…Tarn et al [11] used positive acceleration feedback together with a switching control strategy for force regulation and contact transition control. Discontinuous control approaches are also proposed in [12], [13]. Stability of a system undergoing contact transition is investigated using hybrid systems theory in [19] and [20].…”

mentioning

confidence: 99%

Neural Network Control of a Robot Interacting With an Uncertain Hunt-Crossley Viscoelastic Environment

Bhasin

Dupree

Patre

et al. 2008

ASME 2008 Dynamic Systems and Control Conference, Parts a and B

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Abstract-A continuous controller is developed for a robot that moves in free space, undergoes a collision with a viscoelastic environment, and then regulates the new coupled dynamic system to a desired setpoint. Since the model for the viscoelastic surface contains uncertainties that do not satisfy the linear-in-the-parameters assumption, the model is approximated by a neural network feedforward term, which is combined with a continuous feedback term to guarantee uniformly ultimately bounded regulation of the system despite parametric uncertainties in the robot and the viscoelastic environment. Experimental results of a two-link robot interacting with a human tissue phantom demonstrate the performance of the proposed controller.

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A stable transition controller for constrained robots

Cited by 60 publications

References 23 publications

A force limiting adaptive controller for a robotic system undergoing a non-contact to contact transition

A force limiting adaptive controller for a robotic system undergoing a non-contact to contact transition

Lyapunov-based control of a robot and mass-spring system undergoing an impact collision

Neural Network Control of a Robot Interacting With an Uncertain Hunt-Crossley Viscoelastic Environment

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