조인트간 가상의 토션스프링을 이용한 힘 반향 master-slave 시스템

Abstract

햅틱 기술은 입력장치에서 말단부에 전해지는 힘과 운동 등을 느끼게 하는 기술을 말한다. 대표적인 햅틱의 적용 분야는 복강경 수술로봇인 Intuitive Surgical 사의 DaVinci가 있으며, 접근이 어렵거나 인간에게 유해한 환경인 핵 시설 내부, 우주, 해저, 지하 등에서 기계를 조작하기 위해 Master-Slave 형태의 구조를 가지고 사용되며, 컴퓨터, 비디오 게임의 가상 공간에서 게이머에게 촉감을 구현하는데에도 응용되고 있다. 원격조작은 1954년 Argonne National Laboratory에서 기구적 링크로만 연결하여 근거리에서 시도되었으나 시각만을 이용한 현실감에 한계를 느껴 햅틱의 필요성이 생겨났다. 햅틱을 구현하기 위해서는 슬레이브쪽의 end-effecter에 고가의 FT센서 또는 토크센서를 부착하여 외력을 측정한 후 이를 마스터로 피드백하여 사용자에게 외력을 전달하는 방식이 사용되는데, 시각에 촉각정보를 추가로 제공하여 사용자에게 더 현실감있는 원격정보를 제공할 수 있게 된 반면, 이로 인해 시스템의 가격이 크게 상승하는 요인이 되었다. 본 연구에서는 가상스프링 알고리즘을 이용하여 이러한 고가의 센서를 사용하지 않고 사용자에게 외력정보를 제공할 수 있는 시스템을 제안한다. 마스터와 슬레이브의 위치정보가 상이할 경우 그 중간지점으로 당겨지는 힘을 전류제어를 통해 각각 가하여 마스터를 조작하여 슬레이브를 제어할 수 있음과 동시에 슬레이브쪽에 이 동작을 방해하는 요소 또는 외력이 가해질 경우 마스터에 그 정보가 전달 될 수 있는 알고리즘을 고안하고 실험을 통해 효과를 측정하였다. 또한 정지마찰력 문제, 그리고 슬레이브가 강체와 접촉하였을 경우의 대응을 위해 비선형제어구문을 추가하여 현실감을 줄 수 있도록 한 후 실험을 실시하였다. 실험결과 알고리즘이 적용된 시스템이 외란의 경향을 사용자가 구분할 수 있을 정도의 정보를 전달하는 것이 가능하다는 것이 확인되었으며, 이후 빠른 제어주기를 제공할 수 있는 우수한 하드웨어와 보완된 비선형제어를 통해 성능이 개선된다면 가격으로 인해 시장진입에 어려움을 겪고 있는 로봇 분야의 시장개척에 기여할 것으로 예상한다.|Haptics is a technic what makes to feel force or movement to endeffector from input device. Representative applications of haptics are laparoscopic surgery robot 'DaVinci' of Intuitive Surgical, using master-slave system on place where hard to approach or nuclear facility where has hazardous environment to human or space or abyss or underground, and also being applied to body out tactile to gamer on PC and video game. Remote controll was tried with only mechanical linkage in short range by Argonne National Laboratory in 1954, but there was limit on reality with vision information only and that's why to develop haptics. In order to body out haptics, it is necessary to attach expensive FT sensor or torque sensor on endeffector which is on to slave part, to know disturbance and feedback to the master part to make user know it. Though it is possible to provide not only vision information but also tactile information, it occurs high price of whole system. In this paper, we propose a system with novel algorithm which can provide disturbance to user without those expensive sensors, with applying of virtual spring damper hypothysis. When position of master between slave is different, it is able to contol slave with operating master, by giving torque to each device to the mid-point with current control. And at the same time, when disturbance or something which bothers this motion comes. We had have experiment and measured effect of the algorithm. Also in order to deal with traction problem and case of contacting with rigid stuff, we added nonlinear control syntax. Experimental result shows that it is possible to convey enough informations to user to distinguish tendency of disturbance. If we improve performance through excellent hardware which can provide more frequent control cycle and improved nonlinear control syntax, we expect that this can contribute market development of robotics that is going through struggles to market.; Haptics is a technic what makes to feel force or movement to endeffector from input device. Representative applications of haptics are laparoscopic surgery robot 'DaVinci' of Intuitive Surgical, using master-slave system on place where hard to approach or nuclear facility where has hazardous environment to human or space or abyss or underground, and also being applied to body out tactile to gamer on PC and video game. Remote controll was tried with only mechanical linkage in short range by Argonne National Laboratory in 1954, but there was limit on reality with vision information only and that's why to develop haptics. In order to body out haptics, it is necessary to attach expensive FT sensor or torque sensor on endeffector which is on to slave part, to know disturbance and feedback to the master part to make user know it. Though it is possible to provide not only vision information but also tactile information, it occurs high price of whole system. In this paper, we propose a system with novel algorithm which can provide disturbance to user without those expensive sensors, with applying of virtual spring damper hypothysis. When position of master between slave is different, it is able to contol slave with operating master, by giving torque to each device to the mid-point with current control. And at the same time, when disturbance or something which bothers this motion comes. We had have experiment and measured effect of the algorithm. Also in order to deal with traction problem and case of contacting with rigid stuff, we added nonlinear control syntax. Experimental result shows that it is possible to convey enough informations to user to distinguish tendency of disturbance. If we improve performance through excellent hardware which can provide more frequent control cycle and improved nonlinear control syntax, we expect that this can contribute market development of robotics that is going through struggles to market.