Baxter

Baxter is a two-armed collaborative robot, or “cobot”, made by Rethink Robotics. It came out in 2012 as an industrial robot that could work next to people without a safety cage, and it became a popular robot for research and teaching. Rethink Robotics closed in 2018, so Baxter’s software has not been updated since then. Our robots run the last version, 1.2.0.

The society has two Baxters in the Robotics Lab. One of them stands on a Mobility Base, a wheeled platform that can carry it around the room.

The robot

• Arms. Two arms with seven joints each: two in the shoulder, two in the elbow and three in the wrist. Each joint is driven through a spring (a series elastic actuator), so the robot can feel the force on every joint. That makes Baxter much gentler to bump into than a classic industrial arm.
• Cuffs. Hold the ring just behind a hand and the arm goes limp, so you can guide it by hand. This is the easiest way to show the robot a position.
• Hands. Each arm takes a two-finger electric gripper or a suction cup.
• Head. The face is a 1024 × 600 screen that can show any picture. The head turns left and right and can nod.
• Cameras. There is one in the head and one in each hand. Only two of the three can be switched on at the same time.
• Sensors. Twelve ultrasound sensors in a ring around the head notice people and objects nearby. Each hand also has an infrared distance sensor (4 to 40 cm) and an accelerometer.
• Buttons and lights. Four navigators (a scroll wheel with three buttons) sit on the arms and the torso. There are more buttons on the cuffs and lights around the head.
• Computer. A computer inside the robot runs all of this. It speaks ROS 1, the Robot Operating System.

How you program it

Everything Baxter can do is offered as ROS 1 topics and services: streams of joint angles and sensor readings come out, and commands go in. You send those from a computer connected to the robot.

The original tools for this need a ROS 1 computer of the same age as the robot. We use the Baxter ROS 2 bridge instead. It lets you program both robots from current ROS 2 and Python, with a library called baxter_interface:

from baxter_interface import Limb, RobotEnable

RobotEnable().enable()
left = Limb('left')
left.move_to_neutral()
left.move_by(z=0.10)        # the hand 10 cm up

The tutorials below start from the very beginning.

Our two Baxters

Both robots have the same software, so a program written for one runs on the other. Each robot is a separate system on the network, and they never talk to each other directly. The bridge brings them together, so one program can control both. The robot on the Mobility Base can also drive around under program control.

How they are set up and connected is under Documentation.

What we have done with it

• A music video. Baxter’s first outing with the society, in January 2026.
• Baxter × Pepper dance. A 30-second routine for two very different robots.
• Baxter ROS 2 bridge. Bringing both robots and the Mobility Base to ROS 2.

Safety

Baxter’s arms are strong and can swing wide. Whenever the robot is enabled, someone stands at the e-stop (the big red button) and nobody is within reach of the arms. Before the Mobility Base drives, someone holds its joystick and the floor around it is clear. Try new programs slowly first.