About

Dual-End Effector Robot (D-EER)
ME 314: Robot Dexterity

Professor Monroe Kennedy

Spring 2025
Stanford University

Objectives

xArm7 Robot

We were given the xArm7 robot, a robot with 7 revolute joints, making it perfect for table tasks in the realm of robot dexterity. We were allowed to modify existing end effectors (parallel gripper or pneumatic) or design our own to achieve the objectives.

The objective of this project was to perform dexterous manipulation by demonstrating four tasks using the xArm robot:

a) Pick and Place: Using visual perception to detect a red block and target the final location (a green square)

b) 'Peg in Hole': Using visual perception to detect a red cylinder, 'peg,' and place it in a blue area with a hole.

c) Coin Pickup: Using visual perception to detect a quarter on the table and target the final location (a green square)

d) Flat Dollar Bill Pickup: Using visual perception to detect the dollar bill on the table and target the final location (a green square)

Method/Strategy

We designed a custom dual-end effector that is capable of achieving all the tasks without having to swap the end effector. The design requires two servos and a pump. The arm servo allows us to switch between the gripper side and the pump side. The gripper servo opens and closes the gripper. The parallel jaw gripper was used to tackle tasks 1a and 1b. Similar to the gripper that comes with the xArm robot, the parallel jaw gripper is capable of picking up the block and the cylinder. The pump was used for tasks 1c and 1d. We make contact with the object and turn the pump on to retrieve the object. Then, we simply turn the pump off to release the object when we are slightly above the target location. We chose a suction cup that is smaller than the diameter of a quarter. Therefore, it can easily pick up a real quarter and a dollar bill without needing high precision or calculating orientation. The suction cup can easily pick up a real quarter, but has difficulties with the plastic quarter. That is because a real quarter is smoother. However, it can pick up the plastic quarter if the suction cup contacts the head side, right above the neck.