Mobile robot

• US 20060097683A1
• Filed: 11/10/2005
• Published: 05/11/2006
• Est. Priority Date: 11/11/2004
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Egawa, Saku, Nakamura, Ryosuke, Tamamoto, Junichi, Hosoda, Yuji, Horiuchi, Toshihiko
• Granted Patent: US 7,649,331 B2
• Time in Patent Office: Days
• US Class Current: 318/568.12
• CPC Class Codes: B25J 5/007 mounted on wheels
• CPC Class Codes: B62D 57/024 specially adapted for moving on inclined or vertical surfaces endless-track vehicles for ascending or descending stairs B62D55/075; hand-carts with provision for travelling up or down stairs B62B5/02
• CPC Class Codes: B62K 11/007 Automatic balancing machines with single main ground engaging wheel or coaxial wheels supporting a rider

Abstract

A mobile robot has a mobile mechanism, a swing mechanism and a control unit. The mobile mechanism is of a coaxial two-wheeled type and controls a forward thrust using inverted pendulum control. The swing mechanism actively swings an upper body laterally with respect to the mobile mechanism. A centrifugal force and a gravitational force act on a center of gravity of the mobile robot. A swing attitude is controlled such that a location of intersection of an extension of a composite vector of the forces acting on the center of gravity of the mobile robot and a ground plane of wheels is kept between left and right wheels.

Claims

1. A mobile robot comprising a coaxial two-wheeled mobile mechanism having left and right wheels and an upper body connected to an upper portion of the mobile mechanism, wherein:

the mobile robot is further provided with a swing mechanism which swings the upper body laterally with respect to the mobile mechanism and a control unit which controls the swing mechanism;

a forward thrust of the mobile mechanism is controlled using inverted pendulum control; and

the control unit controls the swing mechanism such that, when the upper body is inclined beyond a prescribed value while the mobile robot is traveling forward, the upper body restores a previous position.

2. The mobile robot according to claim 1, wherein the control unit controls the swing mechanism such that, when the mobile robot makes a turn, a force acting on a center of gravity of the mobile robot is directed between the two wheels.

3. A mobile robot comprising a coaxial two-wheeled mobile mechanism which controls a forward thrust using inverted pendulum control, wherein:

the mobile robot is further provided with a swing mechanism which actively swings an upper body laterally with respect to the mobile mechanism and a control unit which controls the swing mechanism; and

the control unit includes a sensing means for estimating a location of intersection of an extension of a composite vector of a centrifugal force and a gravitational force acting on a center of gravity of the mobile robot and a ground plane of wheels and controls a swing attitude so as to keep, based on an estimate made by the sensing means, the location of intersection in a prescribed area between left and right wheels.

4. The mobile robot according to claim 3, wherein the control unit sets the prescribed area for the location of intersection approximately at a center between the left and right wheels and controls the swing attitude so as to keep the location of intersection in the prescribed area thus set.

5. The mobile robot according to claim 3, wherein:

the sensing means includes an acceleration sensor which measures accelerations in three directions, i.e., front-back direction, left-right direction and top-down direction and an inclination sensor which measures an attitude of the mobile mechanism with respect to a vertical direction; and

the control unit estimates, based on data measured by the acceleration sensor and the inclination sensor, a resultant acceleration vector of a gravitational acceleration acting on the center of gravity of the mobile robot and a centrifugal acceleration generated when the mobile robot makes a turn, and determines, based on the estimate thus made, a swing attitude angle.

6. The mobile robot according to claim 4, wherein:

the sensing means includes an acceleration sensor which measures accelerations in three directions, i.e., front-back direction, left-right direction and top-down direction and an inclination sensor which measures an attitude of the mobile mechanism with respect to a vertical direction; and

the control unit estimates, based on data measured by the acceleration sensor and the inclination sensor, a resultant acceleration vector of a gravitational acceleration acting on the center of gravity of the mobile robot and a centrifugal acceleration generated when the mobile robot makes a turn, and determines, based on the estimate thus made, a swing attitude angle.

7. The mobile robot according to claim 3, wherein the control unit:

estimates, based on pre-generated time-series data on travel locus curvature and travel speed, time-series data on a centrifugal acceleration acting on the center of gravity of the mobile robot;

generates, based on the estimate thus made, time-series data on a swing attitude angle; and

controls the swing attitude by following the time-series data on the swing attitude angle thus generated in synchronization with travel control performed based on the time-series data on the travel locus curvature and the travel speed.

8. The mobile robot according to claim 4, wherein the control unit:

estimates, based on pre-generated time-series data on travel locus curvature and travel speed, time-series data on a centrifugal acceleration acting on the center of gravity of the mobile robot;

generates, based on the estimate thus made, time-series data on swing attitude angle; and

controls the swing attitude by following the time-series data on the swing attitude angle thus generated in synchronization with travel control performed based on the time-series data on the travel locus curvature and the travel speed.

9. The mobile robot according to claim 7:

wherein the sensing means includes an inclination sensor which is provided for the mobile mechanism and which measures an attitude of the mobile mechanism with respect to a vertical direction; and

wherein the control unit;

corrects time-series data on a centrifugal acceleration acting on the center of gravity of the mobile robot, the time-series data having been estimated for a travel on a level surface and the correction being made based on an inclination angle of a travel surface measured, by the inclination sensor while the mobile robot is traveling on the travel surface, in a direction lateral to the mobile robot and an attitude angle of the mobile mechanism with respect to a travel direction,

estimates, based on the correction thus made, a resultant acceleration vector of a gravitational acceleration acting on the center of gravity of the mobile robot and a centrifugal acceleration generated when the mobile robot makes a turn, and

determines, based on the estimate thus made, the swing attitude.

10. The mobile robot according to claim 8:

wherein the sensing means includes an inclination sensor which is provided for the mobile mechanism and which measures an attitude of the mobile mechanism with respect to a vertical direction; and

wherein the control unit;

corrects time-series data on a centrifugal acceleration acting on the center of gravity of the mobile robot, the time-series data having been estimated for a travel on a level surface and the correction being made based on an inclination angle of a travel surface measured, by the inclination sensor while the mobile robot is traveling on the travel surface, in a direction lateral to the mobile robot and an attitude angle of the mobile mechanism with respect to a travel direction,

estimates, based on the correction thus made, a resultant acceleration vector of a gravitational acceleration acting on the center of gravity of the mobile robot and a centrifugal acceleration generated when the mobile robot makes a turn, and

determines, based on the estimate thus made, the swing attitude.

11. A control method for a mobile robot having a coaxial two-wheeled mobile mechanism which controls a forward thrust using inverted pendulum control, a swing mechanism which actively swings an upper body laterally with respect to the mobile mechanism, and a control unit which controls the swing mechanism, the method comprising the steps of:

estimating a location of intersection of an extension of a composite vector of a centrifugal force and a gravitational force acting on a center of gravity of the mobile robot and a ground plane of wheels by a sensing means provided for the control unit; and

controlling, based on the estimate thus made, a swing attitude such that the location of intersection is kept in a prescribed area between left and right wheels.

12. The control method for a mobile robot according to claim 11, wherein:

the prescribed area for the location of intersection is set approximately at a center between the left and right wheels; and

the swing attitude is controlled such that the location of intersection is kept in the prescribed area thus set.