Transform matrix, whom to whom?

[leemengwei]

Hi, thanks for your work. Great one, I like it. I'm doing some deeplearning research, thus I'm not quite familiar with robotics. Sorry for my innocent,
So here's my problem about what is 'real_frame' in code, does that mean to transform from end-effector to old one? (I think it is, but not sure)
Take two frame for example, world_frame and new_frame, when joint is given:

> <joint                 
>   name="joint1"        
>   type="revolute">     
>   <origin              
>     xyz="0 -0.43 0"    
>     rpy="1.5708 0 0" />        <-------rotation around axis X?    counter-clock wise? I guess?
>   <parent              
>     link="base_link" />
>   <child               
>     link="link1" />    
>   <axis                
>     xyz="0 0 1" />     
>   <limit               
>     lower="0"          
>     upper="0"          
>     effort="0"         
>     velocity="0" />    
> </joint>               

then returned two frames are:
[[[ 1. 0. 0. 0. ]
[ 0. 1. 0. 0. ]
[ 0. 0. 1. 0. ]
[ 0. 0. 0. 1. ]]

[[ 1. 0. 0. 0. ]
[ 0. -0. -1. -0.43]
[ 0. 1. -0. 0. ]
[ 0. 0. 0. 1. ]]

[Phylliade]

Hello @leemengwei,

could you paste the code that procuded these outputs?

[leemengwei]

Ops the codes are gone, I've modified them, yet my uncertain remains the same. The first matrix I gave out
[[[ 1. 0. 0. 0. ]
[ 0. 1. 0. 0. ]
[ 0. 0. 1. 0. ]
[ 0. 0. 0. 1. ]]
is something like base frame, world frame or say, I guess.
The second matrix
[[ 1. 0. 0. 0. ]
[ 0. -0. -1. -0.43]
[ 0. 1. -0. 0. ]
[ 0. 0. 0. 1. ]]
is frame I got after forward kinematic , something I got by:
new_frame = np.array(my_chain.forward_kinematics(six_axis)

what does the second matrix mean? Is't transformation from base to new, or from new to base? (I think is the new to base, am I right?)
Thanks

[Phylliade]

This matrix is a position/orientation of the end-effector encoded as homogeneous coordinates;

[[ 1. 0. 0. 0. ]
[ 0. -0. -1. -0.43]
[ 0. 1. -0. 0. ]
[ 0. 0. 0. 1. ]]

With this, you can see that your position is matrix[3, :3], so here the position of your end-effector is [0, -0.43, 0]