# Do DH parameters change for a scaled robot 3d model?

I have the actual DH parameters of a robot:

d1 = 0.4865 m
d2 = 0.600 m
d3 = 0.065 m
a1 = 0.150 m
a2 = 0.475 m


all other di's and ai's are zero.

Can I use these for an inverse kinematics analytic closed form computation or should I measure the virtual distances in the 3d environment?

I am actually asking if the theta angles that will be yeld after the computations are dependent on the scale of those distances.

EDIT: Scale factor is unknown

• or you could say i am asking that if some dh parameters work for a 3d robot model, would they work the exactly the same on another bigger or smaller one? I guess the desired transform of the end effector should be different, but what else? – hey Aug 21 '16 at 19:33

You will need to provide target coordinates (x,y,z, etc) to your inverse kinematics equations. As long as they have the same scale as your DH parameters, the joint angles calculated will be the same. But since you don't know the scale factor, you don't know how to scale your inputs.

• Exactly this. How does the end effector get to a Cartesian coordinate if you don't know how long any of the linkages are? – Chuck Aug 21 '16 at 22:17
• I wanted to see if there is any other problem aside the transform of the end effector, thanks for your responses – hey Aug 22 '16 at 10:35