APPARATUS AND METHOD FOR STABILIZING HUMANOID ROBOT

• US 20110040407A1
• Filed: 08/04/2010
• Published: 02/17/2011
• Est. Priority Date: 08/12/2009
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: LIM, Bok Man, Xu, Guo Chun, Kim, Myung Hee, Roh, Kyung Shik, Lim, San
• Granted Patent: US 8,798,793 B2
• Time in Patent Office: Days
• US Class Current: 700/253
• CPC Class Codes: B25J 9/162 Mobile manipulator, movable base with manipulator arm mounted on it
• CPC Class Codes: B25J 9/1638 compensation for arm bending/inertia, pay load weight/inertia
• CPC Class Codes: G05B 2219/39215 Adaptive control with stabilizing compensation
• CPC Class Codes: G05B 2219/39325 External force control, additional loop comparing forces corrects position
• CPC Class Codes: G05B 2219/40264 Human like, type robot arm

Abstract

Disclosed is a humanoid robot apparatus, method and computer-readable medium thereof related to lifting and holding a heavy object having a weight unknown to the robot, by measuring an external force acting on the robot. Linear momentum and rotational momentum are compensated for stepwise according to the degree of stability of the robot which is determined based on the measured external force. Accordingly, the robot stably lifts and holds the object without losing its balance.

Claims

1. An apparatus stabilizing a humanoid robot, the apparatus comprising:

a sensor to measure external force acting on the robot while the robot lifts and holds an object; and

a robot controller to compensate for linear momentum and rotational momentum using the measured external force and to control an operation to lift and hold the object having a weight unknown to the robot by the whole-body motion of the robot generated using the compensated momentums.

2. The apparatus according to claim 1, wherein the sensor includes an ankle Force and Torque (F/T) sensor and a wrist F/T sensor.

3. The apparatus according to claim 2, wherein:

the robot controller includes a linear momentum compensation unit, a rotational momentum compensation unit, and a robot stabilization unit,

the linear momentum compensation unit compensates for the linear momentum using the measured value of the F/T sensor attached to wrists of the robot, and

the rotational momentum compensation unit compensates for the rotational momentum using the measured value of the F/T sensor attached to ankles of the robot.

4. The apparatus according to claim 3, wherein the robot stabilization unit estimates reference linear momentum and reference rotational momentum without considering the external force according to Equation 1:

P_ref,x=Mk₁(x_ref−

x_CoG)+Mx′

_ref

P_ref,y=Mk₂(y_ref−

y_CoG)+My′

_ref

P_ref,z=Mk₃(z_ref−

z_CoG)+Mz′

_ref

L_ref,x=L_ref,y=L_ref,z=0 

 

Equation 1

where, M denotes the weight of the robot, k₁, k₂ and k₃ denote gains, x_ref, y_ref and z_ref respectively denote planned robot center-of-gravity position trajectories in axial directions (x-axis, y-axis and z-axis directions), x′

_ref, y′

_ref and z′

_ref respectively denote planned robot center-of-gravity velocity trajectories in the axial directions (x-axis, y-axis and z-axis directions), and x_CoG, y_CoG and z_CoG respectively denote current robot center-of-gravity positions in the axial directions (x-axis, y-axis and z-axis directions).

5. The apparatus according to claim 3, wherein the robot controller further includes a Zero Momentum Point (ZMP) calculation unit, only compensating for the linear momentum or compensating for both the linear momentum and the rotational momentum stepwise according to the stability of the robot, which is determined based on a calculated ZMP.

6. The apparatus according to claim 5, wherein, if the calculated ZMP is outside a stable zone and is within a linear momentum correction zone, the linear momentum compensation unit provides linear momentum P′

_ref,x and P′

_ref,y compensated for according to Equation 3 to the robot stabilization unit;

P′

_ref,x=Mk₁(x_ref−

x′

_CoG)+Mx′

_ref

P′

_ref,y=Mk₂(y_ref−

y′

_CoG)+My′

_ref

P′

_ref,z=P_ref,z

x′

_CoG=((−

P_x,RH+ZMP_x)×

f_z,RH+(−

P_x,LH+ZMP_x)×

f_z,LH))/Mg

y′

_CoG=((−

P_y,RH+ZMP_y)×

f_z,RH+(−

P_y,LH+ZMP_y)×

f_z,LH))/Mg 

 

Equation 3

where, RH denotes a right hand, LH denotes a left hand, P_x,RH denotes the position of the right hand, P_y,LH denotes the position of the left hand, f_z,RH denotes force acting on the right hand, f_z,LH denotes force acting on the left hand, g denotes acceleration due to gravity, ZMP_x denotes a ZMP in an x-axis direction, and ZMP_y denotes a ZMP in a y-axis direction.

7. The apparatus according to claim 5, wherein, if the calculated ZMP is excessively outside of a stable zone and is within a rotational momentum correction zone, the rotational momentum compensation unit provides rotational momentums L′

_ref,x and L′

_ref,y compensated for according to Equation 4 to the robot stabilization unit;

L′

_ref,x=k₄m_x

L′

_ref,y=k₅m_y 

 

Equation

where, k₄ and k₅ denote gains, and m_x and m_y respectively denote the moments of the x-axis direction and the y-axis direction measured by the F/T sensor attached to an ankle.

8. An apparatus stabilizing a humanoid robot, the apparatus comprising:

an ankle Force and Torque (F/T) sensor to measure external force acting on ankles of the robot when lifting and holding an object;

a wrist F/T sensor to measure external force acting on wrists of the robot when lifting and holding the object; and

a robot controller to change whole-body motion which is initially generated before lifting and holding the object according to the measured external forces and to control an operation to lift and hold the object by the changed whole-body motion.

9. A method of stabilizing a humanoid robot, the method comprising:

measuring, by a processor, external force acting on the robot lifting and holding an object;

calculating, by the processor, a Zero Momentum Point (ZMP); and

compensating for linear momentum and rotational momentum if the calculated ZMP is outside a stable zone and lifting and holding the object by whole-body motion generated using the compensated momentums.

10. The method according to claim 9, wherein at least one of the momentums is compensated for stepwise according to a degree which the calculated ZMP is outside the stable zone.

11. The method according to claim 10, wherein, only the linear momentum is compensated for if the calculated ZMP is outside the stable zone and is present in a linear momentum correction zone.

12. The method according to claim 10, wherein, the linear momentum and the rotational momentum are compensated for stepwise if the calculated ZMP is a rotational momentum correction zone located outside a linear momentum correction zone.

14. At least one computer readable medium comprising computer readable instructions that control at least one processor to implement the method of claim 9.

15. At least one computer readable medium comprising computer readable instructions that control at least one processor to implement the method of claim 10.

16. At least one computer readable medium comprising computer readable instructions that control at least one processor to implement the method of claim 11.

17. At least one computer readable medium comprising computer readable instructions that control at least one processor to implement the method of claim 12.

13. A method of stabilizing a humanoid robot, the method comprising:

estimating, by a processor, reference linear momentum and reference rotational momentum without considering external force before lifting and holding an object;

calculating, by the processor a Zero Momentum Point (ZMP) using a value measured by a Force and Torque (F/T) sensor attached to ankles;

compensating, by the processor, for the planned reference linear momentum using a value measured by an F/T sensor attached to wrists if the calculated ZMP is in a first zone located outside a stable zone;

compensating, by the processor, for the planned reference rotational momentum using a value measured by the F/T sensor attached to the ankles if the calculated ZMP is in a second zone located outside the first zone; and

changing whole-body motion using one of the compensated linear momentum and the compensated rotational momentum and controlling an operation to lift and hold the object.

18. At least one computer readable medium comprising computer readable instructions that control at least one processor to implement the method of claim 13.