Mobile robot and method for controlling mobile robot

{
  "publication_number": "US8634955B2",
  "country": "US",
  "kind": "B2",
  "title": "Mobile robot and method for controlling mobile robot",
  "abstract": "A mobile robot includes: a main body; a drive unit that moves the main body; a contact force detecting unit that detects a contact force acting against an obstacle; and a controller that controls the drive unit to move the main body toward a target object under a condition that the contact force detected by the contact force detecting unit is in a predetermined range.",
  "claims": [
    "1. A mobile robot comprising: a main body; a drive unit that moves the main body; a contact force detecting unit that measures a contact force between the mobile robot and an obstacle; an input unit that inputs information indicating characteristics of the obstacle to the controller, the characteristics including a weight of a person or a hardness of a body surface of the person in a case in which the obstacle is the person; a target position detecting unit that detects a target position that indicates a relative position of a target object from the main body; a controller that controls the drive unit to move the main body toward the target position under a condition that the contact force measured by the contact force detecting unit is in a predetermined contact force range so as to keep the contact force, the controller changing the predetermined contact force range in accordance with the information input by the input unit, wherein the controller includes: a velocity control unit that controls a velocity of movement of the main body to control a distance between the target position and a position of the main body to be in a predetermined distance range; a velocity vector generating unit that generates a velocity vector based on an impedance model using the contact force as an input; a moving velocity composing unit that composes an output of the velocity control unit for keeping the constant distance and the velocity vector generated by the velocity vector generating unit; and a contact force attenuating unit that changes a spring constant of the impedance model to a value smaller than a current spring constant when the contact force measured by the contact force detecting unit exceeds a predetermined value, wherein the controller changes the predetermined contact force range in accordance with the information input by the input unit.",
    "2. The mobile robot according to claim 1, wherein the controller further includes: a stopping unit that stops movement of the main body when the contact force is larger than a first predetermined value; and an avoiding unit that avoids movement of the main body in a direction toward an external force that applies the contact force to the main body when the contact force is larger than a second predetermined value that is larger than the first predetermined value.",
    "3. The mobile robot according to claim 1, wherein the velocity vector generating unit generates the velocity vector based on an impedance model G(s) defined by the following equation (1), wherein M is a mass, D is a damper, and K is a spring constant G (s)=1/(Ms 2 +Ds+K) (1).",
    "4. The mobile robot according to claim 1, wherein the contact force detecting unit comprises a touch force sensor mounted on a ring member protruding from an outer periphery of the main body.",
    "5. The mobile robot according to claim 1, wherein when the mobile robot is in a crowd and the velocity control unit determines that the distance is above the predetermined distance range, the contact force detecting unit measures the contact force between the mobile robot and a person in the crowd, and the controller controls the main body to move around the person in the crowd under the condition that the contact force is in the predetermined contact force range and to move toward the target position.",
    "6. A method for controlling a mobile robot, wherein the mobile robot includes: a main body; a drive unit that moves the main body; and a contact force detecting unit that measures a contact force between the mobile robot and an obstacle; an input unit that inputs information indicating characteristics of the obstacle to the controller, the characteristics including a weight of a person or a hardness of a body surface of the person in a case in which the obstacle is the person; and a target position detecting unit that detects a target position that indicates a relative position of a target object from the main body, wherein the method comprises: receiving the measured contact force from the contact force detecting unit; controlling the drive unit to move the main body toward the target position under a condition that the measured contact force is in a predetermined range so as to keep the contact force; controlling a velocity of movement of the main body to control a distance between the target position and a position of the main body to be in a predetermined distance range; generating a velocity vector based on an impedance model using the contact force as an input; composing an output of the velocity control unit for keeping the constant distance and the velocity vector generated by the velocity vector generating unit; changing a spring constant of the impedance model to a value smaller than a current spring constant when the contact force measured by the contact force detecting unit exceeds a predetermined value; and changing the predetermined contact force range in accordance with the information input by the input unit.",
    "7. The mobile robot according to claim 4, wherein the touch force sensor detects which portion of the mobile robot is contacting with the obstacle with how much force."
  ],
  "description_excerpt": "The present invention relates to a mobile robot and a method for controlling the mobile robot, for safely moving toward a target in a situation, such as in a crowd of people, where being bumped with surrounding people and obstacles.\n\nIn a conventional mobile robot, there is used a control method to basically stop moving or to largely avoid a course of movement when people are around the robot while the robot is attempting to follow a target object, thereby securing a safety of the people. An example of such technique is disclosed in JP-A-2006-146491. However, conventional control method is nearly store, which follows a person through a crowd of people.\n\nOne of objects of the present invention is to provide a mobile robot and a controller for the mobile robot, for safely moving toward a target in a situation where being bumped with surrounding obstacles including people, by controlling contact force between the mobile robot and the obstacles. According to an aspect of the invention, there is provided a mobile robot including: a main body; a drive unit that moves the main body; a contact force detecting unit that detects a contact force acting against an obstacle; and a controller that controls the drive unit to move the main body toward a target object under a condition that the contact force detected by the contact force detecting unit is in a predetermined range.",
  "cpc": [
    "G05D 1/0227",
    "B25J 13/08",
    "B25J 5/00",
    "G05D 1/241"
  ],
  "ipc": [
    "G05D 1/02",
    "G06F 19/00"
  ],
  "assignees": [
    "OAKI JUNJI",
    "OZAKI FUMIO",
    "MATSUHIRA NOBUTO",
    "TOSHIBA KK"
  ],
  "inventors": [
    "OAKI JUNJI",
    "OZAKI FUMIO",
    "MATSUHIRA NOBUTO"
  ],
  "filing_date": "2008-07-18",
  "publication_date": "2014-01-21",
  "grant_date": "2014-01-21",
  "priority_date": "2007-07-18",
  "application_number": "US-21931908-A",
  "family_id": "40265488",
  "citations": [
    "JP2006146491A",
    "JPH07257299A",
    "JPH10329071A",
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    "US2005000543A1",
    "US2006106496A1",
    "US2008134458A1",
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    "US2008231221A1",
    "US2009024250A1",
    "US4958068A",
    "US6394203B1",
    "US6481515B1",
    "US6580246B2",
    "US6705332B2",
    "US6810305B2",
    "US7061200B2",
    "US7761954B2",
    "US7818090B2"
  ]
}