The user interface to the system should allow the user to specify the desired motion of the manipulator in different ways depending on the nature of the job the manipulator is designed to do. The following are some of the possible input types the user can use:
to point 
in Cartesian
space.
. This is called
position planning.
. This is called velocity planning.
. This is called force control.
The input type will affect the placement of the inverse kinematics module: outside the update loop, as in the first case, or inside the update loop, as in the last three cases. For the last three cases we have two possible solutions; we can include the inverse kinematics module in the main update loop as we mentioned before, or we can plan ahead in the joint space before we start the update loop. We should calculate the time required for each case plus the time required to make a decision.