Gripping strategy of pneumatic robot arm for industrial fields wrist control in consideration of compensation of gravity

In previous research, we developed a pneumatic robot arm driven by pneumatic actuators as a versatile end effector of a material handling system. Also, we constructed a PI controller through simulations. However, in industrial fields, robots for a material handling system must be able to work while holding objects. We did not consider this in previous research, so this research aims to construct the PI controller for when the hand holds an object. In this research, we experimented in three situations: one is the hand holding nothing, another is holding a tennis ball, and the last is holding a baseball. In all situations, the robot arm has a hysteresis loop, which means the angle changes in spite of the same pressure being applied. Then we constructed a model through these experiments. Moreover, we could decide the optical PI gain with simulation. Finally, using these gains, we could obtain experimental results that match the simulation results.