Admittance control with Type II Singularity evader

A compliant-admittance controller complemented with a Type II evader module is implemented on a 4-DOF parallel robot. The Type II singularity evader provides complete user control over the robot because the evader modifies online the actuators’ trajectory if a singularity is close. The proximity to a singularity is measured by the minimum angle Ω. The location of the actuator on limb 3 is presented to verify the activation of the evader module, while the robot's location on z_m measured by a 3D tracking system demonstrates the complete control over the robot. In the figures, the subindex “a” represents the admittance reference, the subindex “d” stands for evader modifications, the subindex “c” stands for measurements, and the “lim” represents the experimental limits.