Mobile robot

• US 7,649,331 B2
• Filed: 11/10/2005
• Issued: 01/19/2010
• Est. Priority Date: 11/11/2004
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Hosoda, Yuji, Horiuchi, Toshihiko, Egawa, Saku, Nakamura, Ryosuke, Tamamoto, Junichi
• Primary Examiner(s): Benson; Walter
• Assistant Examiner(s): COLON SANTANA, EDUARDO
• Application Number:
  US11/270,599
• Publication Number:
  US 20060097683A1
• Time in Patent Office: 1,531 Days
• Field of Search: 318/568.12, 318/568.16, 318/568.18, 318/568.22, 700245-264, 901/1, 180/8.3
• 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, which controls a forward thrust using inverted pendulum control;

an upper body connected to an upper portion of the mobile mechanism;

a swing mechanism which actively swings the upper body laterally with respect to the mobile mechanisms; and

a control unit which controls the swing mechanism,

wherein the control unit includes 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 left and right wheels of the mobile mechanism, and controls a swing attitude angle of the upper body so as to keep, based on an estimate made by the sensing means, the location of intersection around a center laterally between the left and right wheels.

2. The mobile robot according to claim 1, wherein:

the sensing means includes an acceleration sensor which measures accelerations in a front-back direction, a left-right direction and a 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, the swing attitude angle.

3. The mobile robot according to claim 1, wherein:

the sensing means includes an acceleration sensor which measures accelerations in a front-back direction, a left-right direction and a 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, the swing attitude angle.

4. A mobile robot comprising:

a coaxial two-wheeled mobile mechanism having left and right wheels;

an upper body connected to an upper portion of the mobile mechanism;

a swing mechanism which actively swings the upper body laterally with respect to the mobile mechanism; and

a control unit which controls the swing mechanism,

wherein the control unit includes 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 left and right wheels of the mobile mechanism, 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 the left and right wheels, and

wherein the control unit is further configured to;

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

generate, based on the estimate, time-series data on the swing attitude angle; and

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

5. The mobile robot according to claim 4:

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

wherein the control unit is further configured to;

correct 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,

estimate, based on the correction, 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

determine, based on the estimate, the swing attitude.

6. A mobile robot comprising:

a coaxial two-wheeled mobile mechanism having left and right wheels;

an upper body connected to an upper portion of the mobile mechanism;

a swing mechanism which actively swings the upper body laterally with respect to the mobile mechanism; and

a control unit which controls the swing mechanism,

wherein the control unit includes 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 left and right wheels of the mobile mechanism, and controls a swing attitude so as to keep, based on an estimate made by the sensing means, the location of intersection around a center laterally between the left and right wheels, and

wherein the control unit is further configured to;

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

generate, based on the estimate time-series data on swing attitude angle; and

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

7. The mobile robot according to claim 6:

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

wherein the control unit is further configured to;

correct 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,

estimate, based on the correction, 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

determine, based on the estimate, the swing attitude.

8. A control method for a mobile robot comprising a coaxial two-wheeled mobile mechanism having left and right wheels which controls a forward thrust using inverted pendulum control, an upper body connected to an upper portion of the mobile mechanism, 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 method comprising:

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 the left and right wheels; and

controlling, based on the estimate thus made, a swing attitude angle of the upper body so as to keep the location of intersection around a center laterally between left and right wheels.