Problem with inverse kinematics

[VovaStelmashchuk]

Inverse kinematics doesn't work my robot. The inverse_kinematics function returns wrong values for joints (sush as 1.1111e-12, or other value around zero).

I checked the robot can achive the target point.

The robot is a simple two arms robot based on rotation plate. Rotation plate attach to movable plate which has ability to move by x and y.

My UDRF file:

<robot name="robot_arm">

    <link name="base_link">
        <visual>
            <origin xyz="1.5 0 0" rpy="0 0 0"/>
            <geometry>
                <box size="3 0.05 0.05"/>
            </geometry>
        </visual>
    </link>
        
    <link name="y">
        <visual>
        <origin xyz="0 1.5 0" rpy="0 0 0"/>
            <geometry>
                <box size="0.05 3 0.05"/>
            </geometry>
        </visual>
    </link>
    
    <joint name="y_to_x" type="prismatic">
        <parent link="base_link"/>
        <child link="y"/>
        <origin xyz="0 0 0.05" rpy="0 0 0"/>
        <axis xyz="1 0 0"/>
        <limit lower="0" upper="3"></limit>
    </joint>
    
        
    <link name="robotbase">
        <visual>
            <origin xyz="0 0 0" rpy="0 0 0"/>
            <geometry>
                <cylinder length="0.05" radius="0.1"/>
            </geometry>
            <material name="Red"/>
        </visual>
    </link>

    <joint name="robot_base_to_xy" type="prismatic">
        <parent link="y"/>
        <child link="robotbase"/>
        <origin xyz="0 0 0.05" rpy="0 0 0"/>
        <axis xyz="0 1 0"/>
        <limit lower="0" upper="3"></limit>
    </joint>
    
    <link name="robot_rotation_base">
        <visual>
            <origin xyz="0 0 0" rpy="0 0 0"/>
            <geometry>
                <box size="0.1 0.1 0.1"/>
            </geometry>
            <material name="Green"/>
        </visual>
    </link>
    
    <joint name="robot_rotation" type="revolute">
        <parent link="robotbase"/>
        <child link="robot_rotation_base"/>
        <origin xyz="0 0 0.05" rpy="0 0 1"/>
        <axis xyz="0 0 1"/>
    </joint>
    
        <link name="arm1">
        <visual>
            <origin xyz="0 0 0.5" rpy="0 0 0"/>
            <geometry>
                <box size="0.05 0.05 1"/>
            </geometry>            
            <material name="Blue"/>
        </visual>
    </link>

    <joint name="arm1_rotation" type="revolute">
        <parent link="robot_rotation_base"/>
        <child link="arm1"/>
        <origin xyz="0 0 0" rpy="0 0 0"/>
        <axis xyz="0 1 0"/>
        <limit lower="-1.25" upper="1.25"></limit>
    </joint>

    <link name="arm2">
        <visual>
            <origin xyz="0 0 0.5" rpy="0 0 0"/>
            <geometry>
                <box size="0.05 0.05 1"/>
            </geometry>            
            <material name="Pure"/>
        </visual>
    </link>
        
    <joint name="arm_to_arm" type="revolute">
        <parent link="arm1"/>
        <child link="arm2"/>
        <origin xyz="0 0 1" rpy="0 0 0"/>
        <axis xyz="0 1 0"/>
    </joint>
    
    <material name="Red">
        <color rgba="1.0 0 0 1.0"/>
    </material>
    
    <material name="Green">
        <color rgba="0 1.0 0 1.0"/>
    </material>

    <material name="Blue">
        <color rgba="0 0 1.0 1.0"/>
    </material>

    <material name="Pure">
        <color rgba="1.0 0 1.0 1.0"/>
    </material>

</robot>

My python code:

from ikpy.chain import Chain
from ikpy.link import OriginLink, URDFLink
import numpy as np

my_chain = Chain.from_urdf_file("arm_urdf.urdf")

target_position = [1, 1.5, 1.5]

joint_angles = my_chain.inverse_kinematics(target_position)

print("The angles of each joints are : ", joint_angles)

The python code returns the following:

The angles of each joints are :  [0.00000000e+00 1.65911074e-10 1.98866611e-10 0.00000000e+00
 4.95022040e-11 0.00000000e+00]