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Journal of Mechanical Science and Technology 25 (8) (2011) 2051~2059
www.springerlink.com/content/1738-494x
DOI 10.1007/s12206-011-0624-4
Sensorless and modeless estimation of external force using time delay estimation: application to impedance control
Jae Won Jeong1,*, Pyung Hun Chang2 and Kyung Bin Park1
1Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong, Yuseong-gu, Daejeon, Korea
2Department of Robotics Engineering, Daegu Gyeongbuk Institute of Science and Technology, 50-1, Sang-ri, Hyeonpung-myeon, Dalseong-gun, Daegu, Korea
(Manuscript Received July 19, 2010; Revised April 22, 2011; Accepted May 18, 2011)
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Abstract
This paper proposes an external force estimation algorithm that requires neither dynamical models nor force-torque (F/T) sensors. Considering cost reduction, indirect estimation of external force can be preferable to direct sensing of the force. However, the explicit use of robot dynamical models, required by most previous studies on indirect estimation of external force, can be practically unfavorable due to inevitable modeling errors as well as arduous identification of system parameters. As a remedy for this problem, the Time-Delay Estimation (TDE) scheme has been incorporated in this research. TDE efficiently provides an accurate estimate of nonlinear robot dynamics including external force. Using TDE, the external force has been effectively and efficiently estimated without F/T sensors or robot dynamical models. Through application to impedance control of a robot, the practical advantages of the proposed estimation algorithm are demonstrated.
Keywords: Dynamical decoupling; External force estimation; Impedance control; Time-delay estimation
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1. Introduction
In recently introduced complex robotic systems, such as humanoids, accurate information on external force has become essential as the needs for interaction with the environment (including humans) have gradually increased [1]. A typical approach to obtain the external force is to directly sense it with precision force-torque (F/T) sensors. Although direct sensing provides a highly accurate value of the external force, indirect estimating is often desirable because 1) the expenditure on the highly expensive F/T sensors can be avoided; and 2) the external force exerted not only on the sensor-side but also on the whole robot-body can be estimated.
Most previous studies to estimate the external force (or torque) require accurate dynamical models, which establish the equations of robot motion [2-4]. In practical terms, however, the needs for robot dynamical models accompany several disadvantages: modeling error is inevitable; identification of...