Walking robot and control method thereof
A torque-based walking robot and a control method thereof which stably controls walking of the robot. In the control method, in which high rigidity, equal to that achieved through a position-based control method, is achieved using a torque-based control method without switching between the position-based control method and the torque-based control method while the robot is in motion, a difference between a target torque and a measured torque is forcibly generated by limiting a torque range measurable by each torque sensor, thereby increasing voltage applied to each actuator, and thus achieving high rigidity, equal to that achieved through the position-based control method, using the torque-based control method without switching between the position-based control method and the torque-based control method.
1. A control method of a torque-based walking robot having actuators and torque sensors, the method comprising:
measuring a torque of each actuator of the robot through each torque sensor of the robot;
calculating a target torque of each actuator;
setting, in accordance with the calculated target torque of each actuator, a specific value to be added to the torque measured by each torque sensor, adding the set specific value to the torque measured by each torque sensor, and using the torque measured by each torque sensor and having the set specific value added thereto to calculate a voltage to be applied to each actuator to thereby control each actuator; and
applying the calculated voltage to each actuator, wherein
the setting of the specific value includes:
limiting a torque range measurable by each torque sensor; and
setting a difference between the torque measured by each torque sensor having the limited measurement torque range and the calculated target torque to the specific value.
2. The control method according to claim 1 , wherein the limitation of the torque range is achieved by setting a maximum value and a minimum value of the torque range measurable by each torque sensor.
3. The control method according to claim 2 , wherein the voltage applied to each actuator is controlled by adjusting the specific value by adjusting the maximum value and the minimum value of the torque range.
4. The control method according to claim 1 , wherein the calculation of the target torque includes:
calculating a difference between a target angle of an encoder and an actual angle of the encoder; and
minimizing the difference therebetween.
5. The control method according to claim 1 , wherein the waking robot is controlled by combination of proportional gain control, integral gain control, and differential gain control.
6. A walking robot comprising:
torque sensors to measure torques of actuators of the robot; and
a control unit to calculate a target torque of each actuator, to calculate a voltage to be applied to each actuator using the torque measured by the torque sensors and the calculated target torque, and to apply the calculated voltage to each actuator to thereby control each actuator, wherein
the voltage applied to each actuator is calculated by
setting, in accordance with the calculated torque of each actuator, a specific value to be added to the torque measured by the torque sensors,
adding the set specific value to the measured torques, and
using the measured torques having the set specific value added thereto to calculate said voltage, and
the specific value is obtained by limiting a torque range measurable by each torque sensor through the control unit and setting a difference between the torque measured by each torque sensor having the limited measurement torque range and the target torque to the specific value.
7. The walking robot according to claim 6 , wherein the limitation of the torque range is achieved by setting a maximum value and a minimum value of the torque range measurable by each torque sensor.
8. The walking robot according to claim 6 , wherein the target torque is obtained by calculating a difference between a target angle of an encoder and an actual angle of the encoder and minimizing the difference therebetween.
9. The walking robot according to claim 6 , wherein the control unit controls walking of the robot by combination of proportional gain control, integral gain control, and differential gain control.
10. A method comprising:
setting, in accordance with a target torque, a specific value to be added to a measured torque of an actuator of a walking robot, adding the set specific value to measured torque, and using the measured torque having the set specific value added thereto to calculate a voltage to be applied to the actuator to control the actuator; and
applying the calculated voltage to the actuator to thereby control the actuator, wherein
the torque of the actuator is measured by a torque sensor, and
the setting of the specific value includes limiting a torque range measurable by the torque sensor, and setting a difference between the torque measured by the torque sensor having the limited measurable torque range and the target torque to the specific value.
11. The method according to claim 10 , wherein said setting, adding and using are performed by a computer.
12. The method according to claim 10 , wherein the limitation of the torque range is achieved by setting a maximum value and a minimum value of the torque range measurable by the torque sensor.
13. The method according to claim 10 , wherein the voltage, V, is calculated in accordance with the following expression:
V
=
k
p
2
(
τ
d
-
(
τ
a
+
α
)
)
+
k
i
2
∫
(
τ
d
-
(
τ
a
+
α
)
)
ⅆ
t
=
k
p
2
(
τ
d
-
τ
a
)
+
k
i
2
∫
(
τ
d
-
τ
d
)
ⅆ
t
-
k
p
2
α
-
k
i
2
∫
(
α
)
ⅆ
t
where kp2 is a P gain in PI control, ki2 is an I gain in PI control, T d is the target torque, T is the measured torque, T a is torque measured by a torque sensor having a limited measurement range, and α a difference between the target torque and the measured torque.