Robot state estimation method, computer-readable storage medium, and legged robot

Patent metadata

Field	Value
Publication number	US-12344337-B2
Application number	US-202318144160-A
Country	US
Kind code	B2
Filing date	May 5, 2023
Priority date	Dec 24, 2020
Publication date	Jul 1, 2025
Grant date	Jul 1, 2025

Abstract

A robot state estimation method, a computer-readable storage medium, and a legged robot are provided. The method includes: obtaining force information of a left leg of a robot and a right leg of the robot; calculating a ZMP of the robot in a world coordinate system based on the force information of the left leg and the force information of the right leg; and calculating a position of a center of mass (CoM) of the robot based on a preset linear inverted pendulum model. In this manner, a brand-new linear inverted pendulum model is constructed in advance, which uses the ZMP of the robot as a supporting point of the model, thereby fully considering the influence of the change of the position of the ZMP of the robot on the position of the CoM.

First claim

What is claimed is:

1. A computer-implemented robot state estimation method, comprising:
providing a legged robot having a processor, a body, sensors, a left leg and a right leg, wherein the sensors are installed at parts where two feet of the robot and the legs of the robot are connected;
obtaining, through the sensors, force information of the left leg and force information of the right leg;
calculating, through the processor, a zero-moment point (ZMP) of the legs of the robot in a world coordinate system based on the force information of the left leg and the force information of the right leg;
obtaining, through the processor, a posture angle of the body of the robot and a planned center of mass (COM) position of the robot;
calculating, through the processor, a position of a CoM of the robot based on the planned COM position, the posture angle of the body, and the ZMP of the legs; and
controlling, through the processor, motions of the robot, based on the position of the COM of the robot.

2. The method of claim 1 , wherein the calculating the position of the CoM of the robot based on the planned COM position, the posture angle of the body, and the ZMP of the legs comprises:
calculating a pose transformation matrix from a body coordinate system of the robot to the world coordinate system based on the posture angle of the body; and
calculating the position of the CoM of the robot based on the planned COM position, the pose transformation matrix, and the ZMP of the legs.

3. The method of claim 2 , wherein the calculating the position of the COM of the robot based on the planned COM position, the pose transformation matrix, and the ZMP of the legs comprises:
calculating the position of the CoM of the robot using an equation of:
Com measure [3]= P[ 3]+ T body2world *( Com plan [3]− P[ 3]);

where, Com plan [3] is the planned COM position, T body2world is the pose transformation matrix, P[3] is the ZMP of the legs, and Com measure [3] is the position of the CoM of the robot.

4. The method of claim 1 , wherein the calculating the ZMP of the legs of the robot in the world coordinate system based on the force information of the left leg and the force information of the right leg comprises:
calculating the ZMP of the left leg of the robot based on the force information of the left leg;
calculating the ZMP of the right leg of the robot based on the force information of the right leg;
obtaining a first position and a second position, wherein the first position is a position of an origin of a six-dimensional force coordinate system of the left leg of the robot in the world coordinate system, and the second position is a position of an origin of a six-dimensional force coordinate system of the right leg of the robot in the world coordinate system; and
calculating the ZMP of the legs based on the first position, the second position, the ZMP of the left leg, and the ZMP of the right leg.

5. The method of claim 4 , wherein the calculating the ZMP of the left leg of the robot based on the force information of the left leg comprises:
calculating the ZMP of the left leg using an equation of:

p
lx

=

(

-

T
lx

-

F
lx

*

d
l

)

F
lz

;

p
ly

=

(

-

T
ly

-

F
ly

*

d
l

)

F
lz

;
and

p
l

=

[

p
lx

,

p
ly

;
0

]

;

where, p lx is the coordinate of the ZMP of the left leg on the x-axis of the six-dimensional force coordinate system of the left leg, and p ly is the coordinate of the ZMP of the left leg point on the y-axis of the six-dimensional force coordinate system of the left leg, F lx is a force component of the force information of the left leg on the x-axis of the six-dimensional force coordinate system of the left leg, F ly is a force component of the force information of the left leg on the y-axis of the six-dimensional force coordinate system of the left leg, F lz is a force component of the force information of the left leg on the z-axis of the six-dimensional force coordinate system of the left leg, T lx is a moment component of the force information of the left leg on the x-axis of the six-dimensional force coordinate system of the left leg, T ly is a moment component of the force information of the left leg on the y-axis of the six-dimensional force coordinate system of the left leg, d l is a height between the six-dimensional force sensor of the left leg and a ground, and p l is the ZMP of the left leg;
the calculating the ZMP of the right leg of the robot based on the force information of the right leg comprises:
calculating the ZMP of the right leg using an equation of:

p
rx

=

(

-

T
rx

-

F
rx

*

d

Assignees

• Ubtech Robotics Corp Ltd

Inventors

• Ge Ligang
• Lìu Yizhang
• Chen Chunyu
• Xie Zheng
• Xiong Youjun

Classifications

• G01M1/122

  Determining position of centre of gravity · CPC title

• B25J13/085

  Force or torque sensors (B25J13/082, B25J13/084 take precedence) · CPC title

• B25J9/1633

  compliant, force, torque control, e.g. combined with position control · CPC title

• B25J9/161

  Hardware, e.g. neural networks, fuzzy logic, interfaces, processor · CPC title

• B25J9/163

  learning, adaptive, model based, rule based expert control · CPC title