transporting an object by a passive mobile robot with servo brakes in cooperation with a human

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  • This article was downloaded by: [Temple University Libraries]On: 08 December 2014, At: 05:33Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

    Advanced RoboticsPublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/tadr20

    Transporting an Object by aPassive Mobile Robot with ServoBrakes in Cooperation with aHumanYasuhisa Hirata a , Zhidong Wang b , Kenta Fukaya c &Kazuhiro Kosuge da Department of Bioengineering and Robotics, TohokuUniversity, 6-6-01, Aoba, Aramaki, Aoba-ku, Sendai980-8579, Japan;, Email: hirata@irs.mech.tohoku.ac.jpb Department of Advanced Robotics, Chiba Institute ofTechnology, Narashino, Chiba 275-0016, Japanc Department of Bioengineering and Robotics, TohokuUniversity, 6-6-01, Aoba, Aramaki, Aoba-ku, Sendai980-8579, Japand Department of Bioengineering and Robotics, TohokuUniversity, 6-6-01, Aoba, Aramaki, Aoba-ku, Sendai980-8579, JapanPublished online: 02 Apr 2012.

    To cite this article: Yasuhisa Hirata , Zhidong Wang , Kenta Fukaya & Kazuhiro Kosuge(2009) Transporting an Object by a Passive Mobile Robot with Servo Brakes in Cooperationwith a Human, Advanced Robotics, 23:4, 387-404, DOI: 10.1163/156855309X408745

    To link to this article: http://dx.doi.org/10.1163/156855309X408745

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    http://www.tandfonline.com/page/terms-and-conditionshttp://www.tandfonline.com/page/terms-and-conditions

  • Advanced Robotics 23 (2009) 387404www.brill.nl/ar

    Full paper

    Transporting an Object by a Passive Mobile Robot withServo Brakes in Cooperation with a Human

    Yasuhisa Hirata a,, Zhidong Wang b, Kenta Fukaya a and Kazuhiro Kosuge a

    a Department of Bioengineering and Robotics, Tohoku University, 6-6-01, Aoba, Aramaki,Aoba-ku, Sendai 980-8579, Japan

    b Department of Advanced Robotics, Chiba Institute of Technology, Narashino,Chiba 275-0016, Japan

    Received 2 May 2008; accepted 7 August 2008

    AbstractIn this paper, we introduce a passive mobile robot called PRP (Passive Robot Porter) to realize transportationof an object in cooperation with human, which is developed based on a concept of passive robotics. PRPconsists of three omni-directional wheels with servo brakes and a controller. It can manipulate an objectby controlling an external force/moment applied by a human based on the control of the servo brakes. Weconsider the characteristics of the servo brakes and control the brake torque of each wheel based on thebrake force/moment constraint so that several motion functions of PRP are realized based on the appliedforce. This allows PRP to track a path which includes motion perpendicular to the pushing direction of thehuman without using servo motors. The impedance-based motion control is also realized with respect to theperpendicular to the pushing direction. These functions are implemented on PRP experimentally, and theexperimental results illustrate the validity of PRP and its control method. Koninklijke Brill NV, Leiden and The Robotics Society of Japan, 2009

    KeywordsPassive mobile robot, passive robotics, object handling, humanrobot interaction, brake control

    1. Introduction

    Most robots have been used as industrial robots in factories to replace humans do-ing tasks that humans do not want to do or could not do, and have been isolatedfrom humans. Recently, however, we expect to utilize robot systems not only in theindustrial fields, but also fields such as the home, office and hospital in cooperationwith humans. For realizing physical support for a human being using robot systems,we have to consider two main points: achieving high performance and user safety.

    * To whom correspondence should be addressed. E-mail: hirata@irs.mech.tohoku.ac.jp

    Koninklijke Brill NV, Leiden and The Robotics Society of Japan, 2009 DOI:10.1163/156855309X408745

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  • 388 Y. Hirata et al. / Advanced Robotics 23 (2009) 387404

    To achieve high performance, humanrobot cooperation issues have been stud-ied by many researchers [15] for augmenting human performance. Most of theseconventional intelligent robot systems have servo motors that are controlled basedon the sensory information from sensors such as force/torque sensors, ultrasonicsensors and laser range finders. The high performance for intelligent systems is re-alized in the form of functions such as power assist, collision avoidance, navigation,variable motion characteristics, etc.

    However, if we cannot appropriately control the servo motors of the intelligentsystems, they can move unintentionally and might be dangerous for human beings.In particular, in Japan, the legislation has to be formulated for using them in a liv-ing environment practically. In addition, these systems with servo motors tend tobe heavy and complex, because of the servo motors, reduction gears, sensors, con-troller, batteries, etc. The battery problem is also very severe for long time working,as the servo motors need much electricity to work.

    On the other hand, Goswami et al. have proposed concept of passive robotics [6],in which the system moves passively based on the external force/moment withoutusing the actuators, and have dealt with the passive wrist, whose components aresprings, hydraulic cylinders, dampers, etc. The passive wrist responds to an appliedforce by computing a particular motion and changing the physical parameters ofthe components to realize the desired motion. Peshkin et al. have also developeda handling system of an object called Cobot [7] based on passive robotics, whichconsists of the caster and the servo motor for steering its caster.

    The concept of the passive robot has been extended to many fields. Wasson etal. [8] and Rentschler et al. [9] proposed a passive intelligent walkers. In most ofthese walkers, a servo motor is attached to the steering wheel, similar to the Cobotsystem [7], and the steering angle is controlled based on environmental informationfor navigating the user. We have also proposed a passive intelligent walker calledRT Walker (Robot Technology Walker) [10]. It differs from other passive intelligentwalkers in that it controls servo brakes appropriately to realize several functionswithout using any servo motors.

    In addition, PADyC (Passive Arm with Dynamic Constraints) has been proposedas an assistant tool for surgeons [11]. Other applications for surgical robots are seenin Ref. [12]. Applications to rehabilitation have also been considered by many re-searchers. One example is shown in Ref. [13]. Applications of the concept to hapticdisplays have been proposed in Refs [14, 15]. These passive systems are intrinsi-cally safe because they cannot move unintentionally with a driving force. Thus,passive robotics will prove useful in many types of intelligent systems throughphysical interaction between the systems and humans.

    In this research, we develop a new passive-type mobile robot system for han-dling a single object in cooperation with a human. The passive object handlingrobot called PRP (Passive Robot Porter) consists of three omni-directional wheelswith servo brakes, which can realize omni-directional motion, and its motion iscontrolled based on the servo brakes similar to RT Walker proposed by us [10].

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  • Y. Hirata et al. / Advanced Robotics 23 (2009) 387404 389

    Different from the object handling robot called Cobot [7], PRP does not utilize anyservo motors for realizing the passive robotics concept; it utilizes the servo brakes,which have some unique characteristics. The constraints based on the characteris-tics of the servo brake make the control of a passive robot difficult compared torobot with servo motors. In this paper, we especially address the characteristicsof t

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