Fig. 6

The control block diagram of the force-position alternate control (FPA). Force-position alternate control (FPA) proposed for industrial robots with 6-component force sensors (UFS) attached at the effector and controlled under position commands. For the targeted position x*(n) and force f*(n) at the nth increment, the FPA controller takes alternately the position difference between x*(n) and the real position x(n) (fed back from the robot), and the force difference between f*(n) and the real force f(n) (fed back from the UFS) to give the new position command \(\bar{x}(n)\). The feedback iterations continue until the position and force errors are within an acceptable tolerance, at which point the test will continue to the next increment as described in the general procedure. The alternate input into the controller for each iteration is controlled by switch SW