ROBOT AND CONTROL METHOD THEREOF

• US 20130079929A1
• Filed: 09/26/2012
• Published: 03/28/2013
• Est. Priority Date: 09/28/2011
• Status: Abandoned Application

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: LIM, Bok Man, ROH, Kyung Shik, KIM, Joo Hyung
• Application Number:
  US13/627,667
• Publication Number:
  US 20130079929A1
• Time in Patent Office: Days
• US Class Current: 700/250
• CPC Class Codes: B62D 57/032 with alternately or sequentially lifted supporting base and legs; with alternately or sequentially lifted feet or skid B62D57/024 takes precedence

Abstract

A robot and method of controlling the robot, the method including setting a target walking motion of the robot using an X-axis displacement, a y-axis displacement, and a z-axis rotation of a robot base, detecting and processing data of a position, a speed and a gradient of the robot base, a z-axis external force exerted on the foot, and a position, an angle, and a speed of each rotation joint using sensors, setting a support state and a coordination system of the robot, processing a state of the robot, performing an adaptive control by generating a target walking trajectory of the robot according to the target walking motion when a supporting leg of the robot is changed, setting a state machine representing a walking trajectory of the robot, and controlling a walking and a balancing of the robot by tracing the state machine that is set.

Claims

1. A method of controlling a robot, the method comprising:

setting a target walking motion of the robot using an X-axis displacement, a y-axis displacement, and a z-axis rotation of a robot base of the robot;

detecting and processing data of a position, a speed, and a gradient of the robot base, a z-axis external force exerted on a foot, and a position, an angle, and a speed of rotation joints of the robot, using sensors;

setting a support state and a coordination system of the robot based on the processed data;

processing a state of the robot based on the processed data;

performing an adaptive control by generating a target walking trajectory of the robot according to the set target walking motion when a supporting leg of the robot is changed;

setting a state machine representing a walking trajectory of the robot; and

controlling a walking and a balancing of the robot by tracing the state machine that is set.

2. The method of claim 1, wherein in the detecting and processing of the data, the sensors are installed at a torso, the foot, and the rotation joints of the robot, such that an inertial measurement unit (IMU) sensor installed on the torso of the robot detects the position, the speed, and the gradient of the robot base, a force/torque (F/T) sensor installed on the foot of the robot detects the z-axis external force exerted on the foot, and an encoder sensor installed on each rotation joint of the robot detects the position, the angle, and the speed of the each rotation joint.

3. The method of claim 2, wherein in the detecting and processing of the data, data detected by the IMU sensor and the HT sensor is subject to a smoothing filter or a Low Pass Filter, and data detected by the encoder sensor is subject to a Low Pass Filter.

4. The method of claim 1, wherein in the setting of the support state and the coordination system of the robot, the foot of the robot is determined as a supporting foot of the robot when the z-axis external force exerted on the foot of the robot exceeds a predetermined threshold value.

5. The method of claim 4, wherein in the setting of the support state and the coordination system of the robot, a position of the supporting foot of the robot in the coordination system is set as a zero point.

6. The method of claim 4, wherein in the setting of the support state and the coordination system of the robot, the support state of the robot is divided into a plurality of supporting states, including left side supporting state, a right side supporting state, and a both side supporting state.

7. The method of claim 1, wherein in the processing of the state of the robot, the state of the robot comprises the position, the speed and the gradient of the robot base, and the position, the angle, and the speed of each rotation joint.

8. The method of claim 7, wherein in the processing of the state of the robot, the position and the speed of the robot base are compensated and calculated according to equation 1 by use of the coordination system, wherein equation 1 is as follows:

pB_x′

=pB_x−

l_leg×

sin(B<sub>roll—

FK</sub>−

B<sub>roll—

IMU</sub>)

pB_y′

=pB_y−

l_leg×

sin(B<sub>pitch—

FK</sub>−

B<sub>pitch—

IMU</sub>),  

 

[Equation 1]

herein pBx′ and

pBy′

, respectively, represent an x-axis position of the robot base and a y-axis position of the robot base that are compensated, pBx and pBy, respectively, represent an x-axis position of the robot base and a y axis position of the robot base that are calculated using the coordination system, lleg represents a length of a leg of the robot, Broll_FK and Bpitch_FK, respectively, represent a roll gradient of the robot and a pitch gradient of the robot that are calculated through forward kinematics using the coordination system, and Broll_IMU, Bpitch_IMU, respectively, represent a roll gradient of the robot and a pitch gradient of the robot that are detected by the sensor installed on the torso of the robot.

9. The method of claim 8, wherein in the processing of the state of the robot, the position, the angle, and the speed of each rotation joint are compensated and calculated through forward kinematics and dynamics using of the coordination system based on the processed data.

10. The method of claim 1, wherein in the performing of the adaptive control, the target walking trajectory is generated using the position, the speed, and the gradient of the robot base, and the position, the angle, and the speed of each rotation joint.

11. The method of claim 10, wherein in the performing of adaptive control, a stride of the robot is determined according to equation 2 by use of a virtual inverted pendulum model, and a position stepped by the foot of the robot is determined by mapping the stride to each rotation joint, wherein equation 2 is as follows:

l_step=V_B√

{square root over (h₀/g+V_B²/(4g²))}

p_sweep=arc sin(l_step/l_leg)

λ

=x_des/x_des,max

p_torso=λ

²c_torso,max

p_sweep,max=√

{square root over (λ

)}c_sweep,max+c_sweep,min

p_knee=λ

c_knee,max+(1+λ

)c_knee,min

p_roll=λ

c_roll,max+(1−

λ

)c_roll,min

p_toeoff=λ

c_toeoff,max+(1−

λ

)c_toeoff,min  

 

[Equation 2]

herein, lstep represents the stride, VB represents the speed of the robot base, h0 represents an initial height of the robot base, g is an acceleration gravity, psweep is a control variable of controlling a motion of each rotation joint, lleg is a length of a leg of the robot, xdes is an x-axis displacement of the robot base, xdes,max is a maximum of the x-axis displacement of the robot base, ptorso is a control variable of controlling a rotation angle of a virtual torso, ctorso,max is a predetermined maximum of the rotation angle of the virtual torso, psweep,max is a maximum of a control variable of controlling a motion of each rotation joint, csweep,max is a predetermined maximum of the motion of each rotation joint, csweep,min is a predetermined minimum of the motion of each rotation joint, pknee is a control variable of controlling a rotation angle of a knee joint of the robot, cknee,max is a predetermined maximum of the rotation angle of the knee joint of the robot, cknee,min is a predetermined minimum of the rotation angle of the knee joint of the robot, proll is a control variable of controlling a roll rotation angle of each rotation joint, croll,max is a predetermined maximum of the roll rotation angle of each rotation joint, croll,min is a predetermined minimum of the roll rotation angle of each rotation joint, ptoeoff is a control variable of controlling the position stepped by the foot of the robot, ctoeoff,max is a predetermined maximum of the position stepped by the foot, and ctoeoff,min is a predetermined minimum of the position stepped by the foot.

12. The method of claim 10, wherein in the performing of the adaptive control, according to equation 3, a posture of the torso is controlled by correcting the target walking trajectory using a difference between an actual gradient of the robot base detected by the sensor installed on the torso of the robot and a target gradient of the robot base, wherein equation 3 is as follows:

q<sub>hip—

roll,d</sub>′

=q<sub>hip—

roll,d</sub>−

(B_roll,d−

B<sub>roll—

IMU</sub>)

q<sub>hip—

pitch,d</sub>′

=q<sub>hip—

pitch,d</sub>−

(B_pitch,d−

B<sub>pitch—

IMU</sub>),  

 

[Equation 3]

herein qhip_roll,d′ and

qhip_pitch,d, respectively, represent a roll rotation angle of a hip joint and a pitch rotation angle of the hip joint that are corrected, qhip_roll,d and qhip_pitch,d, respectively, represent a roll rotation angle of the hip joint and a pitch rotation angle of the hip joint that are on the target walking trajectory, Broll,d and Bpitch,d, respectively, represent a target roll gradient of the robot base and a target pitch gradient of the robot base, and Broll_IMU and Bpitch_IMU, respectively, represent a roll gradient of the robot base and a pitch gradient of the robot base that are detected by the sensor.

13. The method of claim 10, wherein in the performing of the adaptive control, a posture of a swinging leg of the robot is controlled to keep a roll rotation angle of an ankle joint of the robot in parallel to a ground according to equation 4 as follows:

q<sub>SW—

ankle—

roll,d</sub>′

=q<sub>SW—

ankle—

roll,d</sub>−

q<sub>SW—

ankle—

roll</sub>,  

 

[Equation 4]

wherein qsw_ankle_roll,d′

is a corrected roll rotation angle of an ankle joint of the swinging leg of the robot, qsw_ankle_roll,d is a roll rotation angle of an ankle joint of the swinging leg of the robot on the target walking trajectory, qsw_ankle_roll is a roll rotation angle of an ankle joint of the swinging leg of the robot that is calculated through the processed data and forward kinematics.

14. The method of claim 2, wherein the supporting leg is changed, based on a load measured by the F/T sensor.

15. A method of controlling a robot, the method comprising:

setting a target walking motion of the robot using an x-axis displacement, a y-axis displacement, and a z-axis rotation of a robot base of the robot;

detecting and processing data of a position, a speed, and a gradient of the robot base, a z-axis external force exerted on a foot, and a position, an angle, and a speed of rotation joints of the robot, using sensors installed at a torso, the foot, and the rotation joints;

setting a support state and a coordination system of the robot based on the processed data;

processing a state of the robot based on the processed data;

performing an adaptive control by generating a target walking trajectory of the robot according to the target walking motion when a supporting leg of the robot is changed;

setting a state machine that represents a walking trajectory of the robot; and

distributing driving torques of the rotation joints of the robot, used to trace the state machine, to actuators of the rotation joints, respectively.

16. The method of claim 15, wherein in the distributing of the driving torques of the rotation joints to the actuators of the rotation joints, a driving torque of each rotation joint is calculated according to equation 5 as follows:

τ

_d=w₁τ

<sub>state—

machine</sub>+w₂τ

<sub>g—

comp</sub>+w₃τ

_model+w₄τ

_reflex,  

 

[Equation 5]

herein τ

d is a driving torque of each rotation joint, w1, w2, w3 and w4 are weighting factors, τ

state_machine is a torque of each rotation joint, used to trace the state machine, τ

g_comp is a gravity compensation torque, τ

model is a balancing torque, and τ

reflex is a reflex torque.

17. The method of claim 16, wherein in the distributing of the driving torques of the rotation joints to the actuators of the rotation joints, the torque of each rotation joint used to trace the state machine is calculated according to equation 6 as follows:

τ

<sub>state—

machine</sub>=k_p(q_d−

q)−

k_dq,  

 

[Equation 6]

herein τ

state_machine is the torque of each rotation joint, used to trace the state machine, kp and kd are parameters, qd is a target angle of each rotation joint, q is an angle of each rotation joint, and q is a speed of each rotation joint.

18. The method of claim 16, wherein in the distributing of the driving torques of the rotation joints to the actuators of the rotation joints, the gravity compensation torque is calculated according to equation 7 as follows:

τ

<sub>g—

comp</sub>=G(R_B,q_d),  

 

[Equation 7]

herein τ

g_comp is the gravity compensation torque, RB is a three by three matrix representing an azimuth of the robot base, qd is a target angle of each rotation joint, and G( ) is a gravity compensation function.

19. The method of claim 16, wherein in the distributing of the driving torques of the rotation joints to the actuators of the rotation joints, the balancing torque is calculated according to equation 8 as follows:

F_virtual=k_pm(p_B,des−

P_B)−

k_dmV_B

τ

_model =J^TF_virtual,  

 

[Equation 8]

herein Fvirtual is a virtual force exerted on the robot, kp and kd are parameters, PB,des is a target position of the robot base, PB is a position of the robot base, m is a mass of the robot, VB is a speed of the robot base, model is the balancing torque, and JT is a Jacobian matrix.

20. The method of claim 16, in the distributing of the driving torques of the rotation joints to the actuators of the rotation joints, the reflex torque is calculated according to equation 9 as follows:

21. A robot having a robot base and a plurality of rotation joints for walking, the robot comprising:

an input unit to obtain a target walking motion of the robot as an input;

a control unit configured to perform an adaptive control by generating a target walking trajectory of the robot according to the inputted target walking motion, to set a state machine representing a walking trajectory of the robot, and to distribute driving torques of the rotation joints, used to trace the state machine, to driving units of the rotation joints, respectively; and

a driving unit configured to drive the respective rotation joints of the robot according to the distributed driving torque.

22. The robot of claim 21, wherein the control unit determines a stride of the robot according to equation 2 by use of a virtual inverted pendulum model, and determines a position stepped by the foot of the robot by mapping the stride to each rotation joint of the robot, wherein equation 2 is as follows:

l_step=V_B√

{square root over (h₀/g+V_B²/(4g²))}

p_sweep=arc sin(l_step/l_leg)

λ

=x_des/x_des,max

p_torso=λ

²c_torso,max

p_sweep,max=√

{square root over (λ

)}c_sweep,max+c_sweep,min

p_knee=λ

c_knee,max+(1+λ

)c_knee,min

p_roll=λ

c_roll,max+(1−

λ

)c_roll,min

p_toeoff=λ

c_toeoff,max+(1−

λ

)c_toeoff,min  

 

[Equation 2]

herein, lstep represents the stride, VB represents the speed of the robot base, h0 represents an initial height of the robot base, g is an acceleration gravity, psweep is a control variable of controlling a motion of each rotation joint, lleg is a length of a leg of the robot, xdes is an x-axis displacement of the robot base, xdes,max is a maximum of the x-axis displacement of the robot base, ptorso is a control variable of controlling a rotation angle of a virtual torso, ctorso,max is a predetermined maximum of the rotation angle of the virtual torso, psweep,max is a maximum of a control variable of controlling a motion of each rotation joint, csweep,max is a predetermined maximum of the motion of each rotation joint, csweep,min is a predetermined minimum of the motion of each rotation joint, pknee is a control variable of controlling a rotation angle of a knee joint of the robot, cknee,max is a predetermined maximum of the rotation angle of the knee joint of the robot, cknee,min is a predetermined minimum of the rotation angle of the knee joint of the robot, proll is a control variable of controlling a roll rotation angle of each rotation joint, croll,max is a predetermined maximum of the roll rotation angle of each rotation joint, croll,min is a predetermined minimum of the roll rotation angle of each rotation joint, ptoeoff is a control variable of controlling the position stepped by the foot of the robot, ctoeoff,max is a predetermined maximum of the position stepped by the foot, and ctoeoff,min is a predetermined minimum of the position stepped by the foot.

23. The robot of claim 22, wherein the control unit controls a posture of the torso by correcting the target walking trajectory using a difference between an actual gradient of the robot base detected by the sensor installed on the torso of the robot and a target gradient of the robot base according to equation 3 as follows:

q<sub>hip—

roll,d</sub>′

=q<sub>hip—

roll,d</sub>−

(B_roll,d−

B<sub>roll—

IMU</sub>)

q<sub>hip—

pitch,d</sub>′

=q<sub>hip—

pitch,d</sub>−

(B_pitch,d−

B<sub>pitch—

IMU</sub>),  

 

[Equation 3]

herein qhip_roll,d′ and

qhip_pitch,d′

, respectively, represent a roll rotation angle of a hip joint and a pitch rotation angle of the hip joint that are corrected, qhip_roll,d and qhip_pitch,d respectively represent a roll rotation angle of the hip joint and a pitch rotation angle of the hip joint that are on the target walking trajectory, Broll,d and Bpitch,d respectively represent a target roll gradient of the robot base and a target pitch gradient of the robot base, and Broll_IMU and Bpitch_IMU respectively represent a roll gradient of the robot base and a pitch gradient of the robot base that are detected by the sensor.

24. The robot of claim 22, wherein the control unit controls a posture of a swinging leg of the robot by keeping a roll rotation angle of an ankle joint of the robot in parallel to a ground according to equation 4 as follows:

q<sub>SW—

ankle—

roll,d</sub>′

=q<sub>SW—

ankle—

roll,d</sub>−

q<sub>SW—

ankle—

roll</sub>,  

 

[Equation 4]

herein qsw_ankle_roll,d′

is a corrected roll rotation angle of an ankle joint of the swinging leg of the robot, qsw_ankle_roll,d is a roll rotation angle of an ankle joint of the swinging leg of the robot on the target walking trajectory, qsw_ankle_roll is a roll rotation angle of an ankle joint of the swinging leg of the robot that is calculated through the processed data and forward kinematics.

25. The robot of claim 21, wherein the control unit calculates a driving torque of each rotation joint according to equation 5 as follows:

τ

_d=w₁τ

<sub>state—

machine</sub>+w₂τ

<sub>g—

comp</sub>+w₃τ

_model+w₄τ

_reflex,  

 

[Equation 5]

herein τ

d is a driving torque of each rotation joint, w1, w2, w3 and w4 are weighting factors, τ

state_machine is a torque of each rotation joint, used to trace the state machine, τ

g_comp is a gravity compensation torque, τ

model is a balancing torque, and τ

reflex is a reflex torque.

26. The robot of claim 25, wherein the control unit calculates the torque of each rotation joint used to trace the state machine according to equation 6 as follows:

τ

<sub>state—

machine</sub>=k_p(q_d−

q)−

k_dq,  

 

[Equation 6]

herein τ

state_machine is the torque of each rotation joint, used to trace the state machine, kp and kd are parameters, qd is a target angle of each rotation joint, q is an angle of each rotation joint, and q is a speed of each rotation joint.

27. The robot of claim 25, wherein the control unit calculates the gravity compensation torque according to equation 7 as follows:

τ

<sub>g—

comp</sub>=G(R_B,q_d),  

 

[Equation 7]

herein τ

g_comp is the gravity compensation torque, RB is a three by three matrix representing an azimuth of the robot base, qd is a target angle of each rotation joint, and G( ) is a gravity compensation function.

28. The robot of claim 25, wherein the control unit calculates the balancing torque according to equation 8 as follows:

F_virtual=k_pm(p_B,des−

P_B)−

k_dmV_B

τ

_model =J^TF_virtual,  

 

[Equation 8]

herein Fvirtual is a virtual force exerted on the robot, kp and kd are parameters, PB,des is a target position of the robot base, PB is a position of the robot base, m is a mass of the robot, VB is a speed of the robot base, τ

model is the balancing torque, and JT is a Jacobian matrix.

29. The robot of claim 25, wherein the control unit calculates the reflex torque according to equation 9 as follows: