Robot controller, robot control method, and legged robot

1. A robot controller that drives joints of a robot having a plurality of legs to make the robot walk, the robot controller being configured to:

determine a permissible range for a trunk vertical position of the robot based on measured environmental parameters, the measured environmental parameters being information of an environment around the robot; and

make the robot walk based on measured posture parameters representing a posture of the robot so that the trunk vertical position remains within the permissible range,

wherein in order to adjust the trunk vertical position within the permissible range, a trunk vertical position reference input, which is a target value of the trunk vertical position of the robot, is set to the lower bound when the trunk vertical position calculated based on the measured posture parameters is smaller than a lower bound of the permissible range, whereas the trunk vertical position reference input is set to the upper bound when the trunk vertical position is larger than an upper bound of the permissible range, and

wherein the measured posture parameters include a thigh angle, a knee angle, and an idling-leg angle of the robot,

wherein a target value of a knee absolute angle, which is a sum of a thigh angle and a knee angle of the robot, is used as a knee absolute angle reference input, and the knee absolute angle reference input is a function of the thigh angle of the robot, and

the robot controller being further configured to:

obtain the knee absolute angle reference input by subtracting a product of a thigh length and the thigh angle of the robot from the trunk vertical position reference input;

divide the subtracted value by a shank length; and

apply arccosine function to the divided value.

2. The robot controller according to claim 1 , comprising:

a thigh angular speed controller that controls a thigh angular speed of the robot;

a knee absolute angle controller that controls a knee absolute angle of the robot; and

an idling-leg angle controller that controls an idling-leg angle of the robot.

3. The robot controller according to claim 1 , further comprising:

a thigh angular speed reference input generator that generates a thigh angular speed reference input; and

a trunk vertical position reference input generator that generates a trunk vertical position reference input based on the measured environmental parameters and the measured posture parameters, the trunk vertical position reference input being a target value of the trunk vertical position of the robot.

4. The robot controller according to claim 1 , wherein a linear-part torque used to control a linear part of a robot mechanism is calculated, the robot mechanism being a mechanism of the robot.

5. The robot controller according to claim 4 , wherein the linear-part torque includes a linear part of ankle torque used to control a thigh angular speed of the robot, a linear part of knee torque used to control a knee absolute angle of the robot, and a linear part of idling-leg torque used to control an idling-leg angle of the robot.

6. The robot controller according to claim 1 , further comprising an environment sensor that outputs the measured environmental parameters.

7. The robot controller according to claim 1 , further comprising a posture sensor that outputs the measured posture parameters.

8. The robot controller according to claim 1 , wherein the idling-leg angle reference input, which is a target value of an idling-leg angle of the robot, is a function of the thigh angle of the robot.

9. The robot controller according to claim 8 , wherein the idling-leg angle reference input is obtained by reversing a sign of the thigh angle.

10. A legged robot comprising the robot controller according to claim 1 and a plurality of legs.

11. A robot controller that makes a robot comprising a plurality of legs walk by driving joints of the robot, the robot controller being configured to:

determine a permissible range for a trunk vertical position of the robot based on measured environmental parameters, the measured environmental parameters being information of an environment around the robot; and

make the robot walk based on measured posture parameters representing a posture of the robot so that the trunk vertical position remains within the permissible range,

wherein the measured environmental parameters include a position of an obstacle located above the robot and a ground temperature.

12. The robot controller according to claim 11 , the robot controller being further configured to:

set a trunk vertical position reference input upper bound, which is an upper bound of a permissible range of the trunk vertical position according to a position of an obstacle located above the robot, and set a trunk vertical position reference input lower bound, which is a lower bound of the permissible range of the trunk vertical position according to a ground temperature;

set a trunk vertical position reference input to the trunk vertical position reference input lower bound when the trunk vertical position is smaller than the trunk vertical position reference input lower bound, the trunk vertical position reference input being a target value of the trunk vertical position of the robot;

set the trunk vertical position reference input to the trunk vertical position reference input upper bound when the trunk vertical position is larger than the trunk vertical position reference input upper bound; and

set the trunk vertical position reference input to the trunk vertical position when the trunk vertical position is within the permissible range.

13. A robot control method to drive joints of a robot having a plurality of legs to make the robot walk, the robot control method comprising:

determining a permissible range for a trunk vertical position of the robot based on measured environmental parameters, the measured environmental parameters being information of an environment around the robot; and

making the robot walk based on measured posture parameters representing a posture of the robot so that the trunk vertical position remains within the permissible range,

wherein in order to adjust the trunk vertical position within the permissible range, a trunk vertical position reference input, which is a target value of the trunk vertical position of the robot, is set to the lower bound when the trunk vertical position calculated based on the measured posture parameters is smaller than a lower bound of the permissible range, whereas the trunk vertical position reference input is set to the upper bound when the trunk vertical position is larger than an upper bound of the permissible range, and

wherein the measured posture parameters include a thigh angle, a knee angle, and an idling-leg angle of the robot,

wherein a target value of a knee absolute angle, which is a sum of a thigh angle and a knee angle of the robot, is used as a knee absolute angle reference input, and the knee absolute angle reference input is a function of the thigh angle of the robot; and

obtaining the knee absolute reference input by subtracting a product of a thigh length and the thigh angle of the robot from the trunk vertical position reference input;

dividing the subtracted value by a shank length; and

applying arccosine function to the divided value.

14. The robot control method according to claim 13 , further comprising generating a trunk vertical position reference input based on the measured environmental parameters and the measured posture parameters, the trunk vertical position reference input being a target value of the trunk vertical position of the robot.

15. The robot control method according to claim 13 , wherein a linear-part torque used to control a linear part of a robot mechanism is calculated, the robot mechanism being a mechanism of the robot.

16. The robot control method according to claim 15 , wherein the linear-part torque includes a linear part of ankle torque used to control a thigh angular speed of the robot, a linear part of knee torque used to control a knee absolute angle of the robot, and a linear part of idling-leg torque used to control an idling-leg angle of the robot.

17. The robot control method according to claim 13 , wherein the idling-leg angle reference input, which is a target value of an idling-leg angle of the robot, is a function of the thigh angle of the robot.

18. The robot control method according to claim 17 , wherein the idling-leg angle reference input is obtained by reversing a sign of the thigh angle.

19. A robot control method to make a robot comprising a plurality of legs walk by driving joints of the robot, the robot control method comprising:

determining a permissible range for a trunk vertical position of the robot based on measured environmental parameters, the measured environmental parameters being information of an environment around the robot; and

making the robot walk based on measured posture parameters representing a posture of the robot so that the trunk vertical position remains within the permissible range,

wherein the measured environmental parameters include a position of an obstacle located above the robot and a ground temperature.

20. The robot control method according to claim 19 , further comprising:

setting a trunk vertical position reference input upper bound, which is an upper bound of a permissible range of the trunk vertical position, according to a position of an obstacle located above the robot, and setting a trunk vertical position reference input lower bound, which is a lower bound of the permissible range of the trunk vertical position according to a ground temperature;

setting a trunk vertical position reference input to the trunk vertical position reference input lower bound when the trunk vertical position is smaller than the trunk vertical position reference input lower bound, the trunk vertical position reference input being a target value of the trunk vertical position of the robot;

setting the trunk vertical position reference input to the trunk vertical position reference input upper bound when the trunk vertical position is larger than the trunk vertical position reference input upper bound; and

setting the trunk vertical position reference input to the trunk vertical position when the trunk vertical position is within the permissible range.