this is our robot stacking a tetra
the arm is two combined four bar linkages and is powered by a cable pulled by the van door motor
our arm moves very smoothly and is easy to control
we have a limit switch with a spring on the gripper which tells us when we have a tetra supported by the gripper good for autonomous and to tell when it is safe to pull out the arm when stacking
we also have a microswitch/pulley combination to warn us if we lose tension in our cable