Robot and method of controlling balance thereof
A finite state machine (FSM)-based biped robot, to which a limit cycle is applied to balance the robot right and left on a two-dimensional space, and a method of controlling balance of the robot. In order to balance an FSM-based biped robot right and left on a two-dimensional space, control angles to balance the robot according to states of the FSM-based biped robot are set. The range of the control angles is restricted to reduce the maximum right and left moving distance of the biped robot and thus to reduce the maximum right and left moving velocity of the biped robot, thereby reducing the sum total of the moments of the biped robot and thus allowing the ankles of the biped robot to balance the biped robot to be controlled, and causing the soles of the feet of the biped robot to parallel contact the ground.
1. A method of controlling balance of a finite state machine (FSM)-based biped walking robot having a right foot and a left foot comprising:
reducing a range of control angles to balance the robot; and
controlling the control angles using a sinusoidal function to balance the robot within a limit cycle,
wherein the states of the FSM include a double support (DS) state, in which the robot is supported with both feet, and
the reduction of the range of the control angles is achieved by reducing an interval between both feet on the ground by drawing both legs inward in the DS state.
2. The method according to claim 1 , wherein the control angles are reduced in consideration of the center of gravity of the robot moving according to states of the FSM.
3. The method according to claim 1 , wherein the states of the FSM include a single support right (SS(R)) state, in which the robot is supported with its right foot, and a single support left (SS(L)) state, in which the robot is supported with its left foot.
4. The method according to claim 1 , wherein the reduction of the range of the control angles is achieved by reducing the maximum right and left moving distance of the robot.
5. The method according to claim 1 , wherein the range of the control angels is designated using zero moment point (ZMP) data based on inertia and acceleration of the robot such that the radius of the limit cycle is reduced.
6. The method according to claim 1 , wherein the control angles arise from the contact point of the robot with the ground, and control ankles of the robot.
7. The method according to claim 6 , wherein the control angles are set to angles between a vector being perpendicular to the ground and a vector coming up to the center of gravity of the robot.
8. The method according to claim 3 , wherein the control of the control angles using the sinusoidal function is achieved such that the limit cycle forms a stable closed loop according to the states of the FSM.
9. The method according to claim 8 , wherein the control of the control angles using the sinusoidal function is achieved such that relations of the control angles and control angular velocities, which are differential components of the control angles, form the limit cycle in the stable closed loop on a two-dimensional space.
10. The method according to claim 9 , wherein the control angle and the control angular velocity in the DS state are maximum.
11. The method according to claim 9 , wherein the control angle and the control angular velocity in the SS(R) or SS(L) state are minimum.
12. A finite state machine (FSM)-based biped walking robot comprising:
ankles;
a set unit to set control angles of the ankles, the set unit setting the control angles corresponding to states of the FSM to balance the robot; and
a control unit to reduce a range of the set control angles and control the control angles using a sinusoidal function to control the angles of the ankles within a limit cycle,
wherein the control unit reduces the range of the control angles by reducing an interval between both feet on the ground by drawing both legs inward in the DS state.
13. The robot according to claim 12 , wherein the control unit controls the control angles using the sinusoidal function such that the limit cycle forms a stable closed loop according to the states of the FSM.
14. The robot according to claim 12 , further comprising force and torque (F/T) sensors to measure zero moment point (ZMP) data based on inertia and acceleration of the robot,
wherein the control unit reduces the range of the control angles set according to the states of the FSM using the ZMP data.
15. The method according to claim 12 , wherein the control unit reduces the range of the control angles by reducing the maximum right and left moving distance of the robot.