A Control Scheme for Physical Human-Robot Interaction Coupled with an Environment of Unknown Stiffness
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A Control Scheme for Physical Human-Robot Interaction Coupled with an Environment of Unknown Stiffness Hsieh-Yu Li1
· Audelia G. Dharmawan1 · Ishara Paranawithana1 · Liangjing Yang2 · U-Xuan Tan1
Received: 7 October 2019 / Accepted: 12 February 2020 © Springer Nature B.V. 2020
Abstract Variable admittance control is commonly used for a collaborative robot to achieve the compliant or accurate cooperation according to human’s intention. However, existing research seldom investigates such a human-robot collaboration coupled with an extra environment with unknown stiffness. If the end-effector that is guided by a human with various intended motion contacts the unknown environment, the interaction might become unstable. Additionally, current research for this physical human-robot-environment interaction use two force sensors to address the issue, and hence the cost of the robot is likely to increase and it reduces the flexibility to many applications. Therefore, in this paper, we address the issue of physical humanrobot interaction coupled with an extra environment whose stiffness is unknown. To achieve this, the condition of robot admittance is rigorously proved in accordance with different human intended motion and environmental stiffness. Moreover, a variable admittance control scheme is proposed based on human intention, environmental force and environment stiffness using the combination of a force sensor and a force observer. Simulation and experiments are conducted to demonstrate the effectiveness of the proposed control scheme. Keywords Physical human-robot interaction (pHRI) · Variable admittance control · Collaborative manipulator
1 Introduction Collaborative Robot, or cobot, has been gaining importance [1–4]. In the context of physical human-robot interaction (pHRI), a cobot whose end-effector is in response to human operator’s intended forces has the advantage of dexterity of human motion and accuracy/high payload capability of the robot [5, 6]. A force/torque (F/T) sensor is normally appended at end-effector of the robot to measure the human force and a controller takes this human force as the input command and engenders motion of the robot [5, 7]. In this paper, we focus on this type of pHRI in which a human and a robot in contact and intentionally exchanging forces to accomplish collaborative tasks. Such a cobot allows the
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10846-020-01176-2) contains supplementary material, which is available to authorized users. Hsieh-Yu Li
hsiehyu [email protected]
Extended author information available on the last page of the article.
human to direct the motion of the robot in their intended direction and hence, the human operator can execute the tasks based on their judgement [5, 8]. The applications utilizing this cobot include the medical robots [8, 11, 12], safe collaboration [9, 10] and human augmentation [5, 13, 14]. Although this pHRI provides a direct cooperation for human to guide the motion of the robot, it is c
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