Apparatus, method, and medium for distinguishing the movement state of mobile robot

• US 20080154429A1
• Filed: 10/22/2007
• Published: 06/26/2008
• Est. Priority Date: 12/21/2006
• Status: Abandoned Application

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: BANG, Seok-won, LEE, Hyoung-ki, CHO, Joon-kee
• Application Number:
  US11/976,208
• Publication Number:
  US 20080154429A1
• Time in Patent Office: Days
• US Class Current: 700/258
• CPC Class Codes: G05D 1/027 comprising intertial navigation means, e.g. azimuth detector inertial navigation G01C21/16; inertial navigation combined with non-inertial navigation instruments G01C21/165
• CPC Class Codes: G05D 1/0272 comprising means for registering the travel distance, e.g. revolutions of wheels measuring distance traversed on the ground by vehicles, e.g. using odometers G01C22/00

Abstract

An apparatus, method, and medium for distinguishing the movement state of a mobile robot are provided. The apparatus includes at least one driving wheel rotatably driven by a driving motor, a first rotation sensor to sense rotation of the driving wheel, at least one caster wheel installed corresponding to the driving wheel and freely moving with respect to a bottom surface, a second rotation sensor to sense rotation of the caster wheel, an acceleration sensor to measure acceleration of the mobile robot, an angular velocity sensor to measure angular velocity of the mobile robot, and a movement-state-distinguishing unit to distinguish movement states of the mobile robot through comparison of the velocity or acceleration of the driving wheel obtained by the first rotation sensor, the velocity or acceleration of the caster wheel obtained by the second rotation sensor, the acceleration obtained by the acceleration sensor, and the angular velocity obtained by the angular velocity sensor.

Claims

1. An apparatus for distinguishing a movement state of a mobile robot, the apparatus comprising:

a driving wheel rotatably driven by a driving motor;

a first rotation sensor to sense rotation of the driving wheel and to determine velocity or acceleration of the driving wheel;

a caster wheel installed corresponding to the driving wheel and freely moving with respect to a bottom surface;

a second rotation sensor to sense rotation of the caster wheel and to determine velocity or acceleration of the caster wheel;

an acceleration sensor to measure the acceleration of the mobile robot;

an angular velocity sensor to measure the angular velocity of the mobile robot; and

a movement-state-distinguishing unit to distinguish movement states of the mobile robot through comparison of the velocity or acceleration of the driving wheel obtained by the first rotation sensor, the velocity or acceleration of the caster wheel obtained by the second rotation sensor, the acceleration obtained by the acceleration sensor, and the angular velocity obtained by the angular velocity sensor.

2. The apparatus of claim 1, wherein the caster wheel is formed at a side of the driving wheel on the same axis as that of the driving wheel and has the same diameter as the driving wheel.

3. The apparatus of claim 1, wherein the movement state includes a normal state in which the mobile robot normally moves with respect to the bottom surface, a slip state in which the driving wheel idles with respect to the bottom surface, a skid state in which the driving wheel skids with respect to the bottom surface, a treadmill state in which the bottom surface moves as the driving wheel moves, an external force stat in which an external force is applied to the mobile robot, and a lift state in which the mobile robot is lifted by an external force.

4. The apparatus of claim 3, wherein the movement-state-distinguishing unit determines that when A_acc≈

A_caster≈

A_drive, the mobile robot is in a rectilinearly normal state, where A_acc denotes an acceleration of the driving wheel, measured by the acceleration sensor, A_drive denotes an acceleration of the driving wheel, measured by the first rotation sensor, and A_caster denotes an acceleration of the caster wheel, measured by the second rotation sensor.

5. The apparatus of claim 3, wherein the movement-state-distinguishing unit determines that when ω

_gyro≈

ω

_caster≈

ω

_drive, the mobile robot is in a normal state in a rotational direction, where ω

_drive denotes an angular velocity of the driving wheel, measured by the first rotation sensor, ω

_caster denotes an angular velocity of the caster wheel, measured by the second rotation sensor, and ω

_gyro denotes an angular velocity measured by the angular velocity sensor.

6. The apparatus of claim 3, wherein the movement-state-distinguishing unit determines that when |V_drive|>

|V_caster|, the mobile robot is in a slip state in a rectilinear direction, where V_drive denotes a velocity of the driving wheel, measured by the first rotation sensor, and V_caster denotes a velocity of the caster wheel, measured by the second rotation sensor.

7. The apparatus of claim 3, wherein the movement-state-distinguishing unit determines that when |ω

_drive|>

|ω

_caster|, mobile robot is in a slip state in a rotational direction, where ω

_drive denotes an angular velocity of the driving wheel, measured by the first rotation sensor, and ω

_caster denotes an angular velocity of the caster wheel, measured by the second rotation sensor.

8. The apparatus of claim 3, wherein the movement-state-distinguishing unit determines that when |V_drive|<

|V_caster|, the mobile robot is in a skid state in a rectilinear direction, where V_drive denotes a velocity of the driving wheel, measured by the first rotation sensor, and V_caster denotes a velocity of the caster wheel, measured by the second rotation sensor.

9. The apparatus of claim 3, wherein the movement-state-distinguishing unit determines that when |ω

_drive|<

|ω

_caster|, the mobile robot is in a skid state in a rotational direction, where ω

_drive denotes an angular velocity of the driving wheel, measured by the first rotation sensor, and ω

_caster denotes an angular velocity of the caster wheel, measured by the second rotation sensor.

10. The apparatus of claim 3, wherein the movement-state-distinguishing unit determines that when A_acc≠

A_drive≈

A_caster, the mobile robot is in a treadmill state in a rectilinear direction, where A_acc denotes an acceleration of the driving wheel, measured by the acceleration sensor, A_drive denotes an acceleration of the driving wheel, measured by the first rotation sensor, and A_caster denotes an acceleration of the caster wheel, measured by the second rotation sensor.

11. The apparatus of claim 3, wherein the movement-state-distinguishing unit determines that when ω

_gyro≠

ω

_caster≈

ω

_drive, the mobile robot is in a treadmill state in a rotational direction, where ω

_drive denotes an angular velocity of the driving wheel, measured by the first rotation sensor, ω

_caster denotes an angular velocity of the caster wheel, measured by the second rotation sensor, and ω

_gyro denotes an angular velocity measured by the angular velocity sensor.

12. The apparatus of claim 3, wherein the movement-state-distinguishing unit determines that when |A_X—

_acc−

A<sub>X—

drive</sub>|>

>

0 or A<sub>Y—

acc</sub>≠

0, the mobile robot is in an external-force-applied state, where A<sub>X—

acc</sub> denotes an acceleration in the moving direction of the mobile robot, measured by the acceleration sensor, A<sub>X—

drive</sub> denotes an acceleration in the moving direction of the mobile robot, measured by the first rotation sensor, and A<sub>Y—

acc</sub> denotes an acceleration in a direction perpendicular to the moving direction of the mobile robot, measured by the acceleration sensor.

13. The apparatus of claim 3, wherein the movement-state-distinguishing unit determines that when |ω

_gyro−

ω

_drive|>

>

0, the mobile robot is in an external-force-applied state, where ω

_gyro denotes an angular velocity measured by the angular velocity sensor, and ω

_drive denotes an angular velocity of the driving wheel, measured by the first rotation sensor.

14. The apparatus of claim 3, wherein the movement-state-distinguishing unit determines that when |A_Z—

_acc|≠

0, the mobile robot is in an external-force-applied state in a direction perpendicular to a bottom surface, where A<sub>Z—

acc</sub> denotes an acceleration in a direction perpendicular to the bottom surface, measured by the acceleration sensor.

15. The apparatus of claim 3, further comprising a pose estimator to estimate a pose of the mobile robot according to the movement state of the mobile robot.

16. The apparatus of claim 15, wherein the pose includes a position (X, Y) on the x-y plane and orientation (θ

) of the mobile robot.

17. The apparatus of claim 16, wherein the pose, including the position X(t+T) and Y(t+T), and orientation θ

(t+T) of the mobile robot when a sampling time T has elapsed at arbitrary time t, is obtained by;

X(t+T)=X(t)+sin θ

(t)*V_body(t)*T, Y(t+T)=Y(t)+cos θ

(t)*V_body(t)*T, and θ

(t+T)=θ

(t)+ω

_body(t)*T,

where X(t), Y(t), and θ

(t) denote the position and the orientation at arbitrary time t, X(t+T), Y(t+T), and θ

(t+T) denote the position and orientation of the mobile robot after a sampling time T has elapsed at arbitrary time t, and V_body(t) and ω

_body(t) are a velocity robot and angular velocity of the mobile at time t.

18. The apparatus of claim 17, wherein when the mobile robot moves, including two wheels left and right, and the movement state of the mobile robot is one of the normal state, the slip state, and the skid state,

$V_{\mathrm{body}}$

( t ) = V caster_left 

( t ) + V caster_right 

( t ) 2 ,

and ω

_body(t)=ω

_gyro(t), where V<sub>caster—

left</sub>(t) denotes a velocity of the left caster wheel, measured by the second rotation sensor at time t, V<sub>caster—

light</sub>(t) denotes a velocity of the right caster wheel, measured by the first rotation sensor at time t, and ω

_gyro denotes an angular velocity measured by the angular velocity sensor.

19. The apparatus of claim 17, wherein when the mobile robot moves, including two wheels left and right, and the movement state of the mobile robot is one of the treadmill state and the external-force-applied state, V_body(t)=∫

₀(A_acc+D(t))dt+V_acc(t₀), ω

_body(t)=ω

_gyro(t), where t₀ denotes a time at which the movement states of the mobile robot are turned into the above states, A_acc denotes an acceleration measured by the acceleration sensor, D(t) denotes a bias value of the acceleration sensor at time t, and V_acc(t₀) denotes a velocity measured by the acceleration sensor at time t₀.

20. The apparatus of claim 19, wherein

$D$

( t ) = V caster 

( t ) - V caster 

( t - T int 



er ) - ∫

t - T int 



er t 

A acc 





t T int 



er ,

where the divisor T_{int er} denotes a time interval used to obtain the bias value.

21. A method for distinguishing the movement state of a mobile robot, the method comprising:

(a) measuring a value of a first rotation sensor which senses rotation of a driving motor for rotating a first driving wheel while the mobile robot is moving and which determines velocity or acceleration of the driving wheel, a value of a second rotation sensor which senses rotation of a driving motor for rotating a caster wheel installed corresponding to the driving wheel and moving freely with respect to a bottom surface and which determines velocity or acceleration of the driving wheel, a value of an acceleration sensor which senses an acceleration of the mobile robot, and a value of an angular velocity sensor which measures an angular velocity of the mobile robot; and

(b) distinguishing the movement state of the mobile robot through comparison of the velocity or acceleration of the driving wheel obtained by the first rotation sensor, the velocity or acceleration of the caster wheel obtained by the second rotation sensor, the acceleration obtained by the acceleration sensor, and an angular velocity obtained by the angular velocity sensor.

22. The method of claim 21, further comprising:

(c) estimating a pose of the mobile robot according to the movement state of the mobile robot.

23. At least one computer readable medium (comprising) storing computer readable instructions that control at least one processor to implement the method of claim 21.

24. An apparatus for estimating a pose of a mobile robot, the apparatus comprising:

a movement-state-distinguishing unit to determine a movement state of the mobile robot through comparison of a measured velocity or measured acceleration of a driving wheel of a robot, a measured velocity or measured acceleration of a caster wheel installed corresponding to the driving wheel and freely moving with respect to a bottom surface, an acceleration of the mobile robot obtained by an acceleration sensor, and an angular velocity obtained by an angular velocity sensor; and

a pose estimator to estimate a pose of the mobile robot according to the movement state of the mobile robot.