InverseKinematics

A new inverse kinematics for humanoid biped robot, whose leg has six degrees of freedom orthogonally.

Prerequisites

The inverse kinematics module depends on Eigen3. Please install Eigen3 in advance.

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Parameters

InvKin

For different-planned robots, the geometry parameters differ. So you have to changes several variables in InverseKinematics.cpp line 14 to 19.

• upper_leg_length: Length of robot's thigh.
• lower_leg_length: Length of robot's calf.
• ankle_from_ground: When robot is standing vertical to the ground with all leg joints stretched, the distance from intersection of ankle_roll joint and ankle_pitch joint to the ground.
• half_hip_width: Half the length of two hip_yaw joints, i.e hip_y_from_origin of left leg.
• hi_x_from_origin: The x_offset between hip axis' intersection and body center point.
• hi_z_from_origin: The z_offset between hip axis' intersection and body center point.

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Important function

The constructor of InvKin class should be given whether your object is right leg or not.

InvKin

This class can be used for calculate the inverse kinematics solution of single leg.

• InvKin

  • Constructor of this class, in which you should give the target leg is right or left.

• LegInvKin

  • Input: The position(x,y,z) and orientation(r,p,y) of one foot.
  • Output: Angles of each joint in the order from up to down.

• CosineTheorem

  • Using the law of cosines to get one angle's value in a triangle.
  • This function have been moved into dmotion_math.cpp

• GetDelta

  • Get the angle between two vector(2D or 3D).
  • This function have been moved into dmotion_math.hpp

WholeBodyIK

This class can be used for calculate the inverse kinematics solution of two legs when the two feet are set in a plane. The plane orientation can be set when you initialize a object.

• WholeBodyIK
  • Constructor of this class, in which you should give the feet distance in x, y, z directions, left leg relative to right leg.
• GetIKResult
  • Input: The position of body center relative to the middle point of between two feet.
  • Output: The servo angles of 12 servos, from left to right, form up to down.
• ChangeFootPos
  • Change the relative foot position.

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Test

Clone this repository to your computer, and build the project.

git clone https://github.com/hannbusann/InverseKinematics.git
cd InverseKinematics
mkdir build 
cd build
cmake ..
make
./InvKin_test