project specification

Fetch Mobile Manipulator

The Fetch Mobile Manipulator provides a fully integrated standard platform for mobile manipulation research. Fetch uses a relatively large and capable mobile manipulator (Fetch) to pick items off of warehouse shelves. The back-drivable 7 DOF arm is capable of lifting 6 kilograms, this is a large enough payload to handle the vast majority (90-95 percent) of all items in a typical warehouse.

Specifications

Weight113.3 kg
Height1,096 mm down
1,491 mm up
Base footprint
Max speed
Degrees of freedom
7-DOF arm
Payload 6 kg
Arm length to gripper mount940.5 mm
Max end effector speed1.0 m/s
Sensors
2D laser25 m
220 degrees
3D RGB-DPrimesense Carmine 1.09 in head
IMU (2)6 DOF IMU in base and gripper
Gripper
Max grasp force245 N
Max gripper opening100 mm
Computer
Processor
RAMIntel i5, Haswell
Hard drive120 GB SSD
WirelessIntegrated 802.11ABGN and 802.15.1
SpeakerStereo speaker in base
Installed softwareUbuntu Linux LTS, ROS
Installed applicationsROS Navigation, MoveIt!, joystick teleop

Overview

The robot consists of a differential drive mobile base, an arm, a pan and tilt head, a torso lift actuator, and a stan-dalone mobile robot platform. The mobile base includesa SICK laser scanner with a 220 degree field of view and 25 meter range.  It's base also includes a base-mounted 3D camera. Fetch includes a head-mounted Primesense Carmine 1.09 depth camera. The gripper is a modularity point, allows custom grippers to be swapped in, but supplied with a default parallel-jaw gripper capable of grasping a wide range of objects. Intel-based computersprovide processing power for navigation, manipulation and perception activities.

The back-drivable 7 DOF arm is capable of lifting 6 kilograms, this is a large enough payload to handle the vast majority (90-95 percent) of all items in a typical warehouse.

The robot is suitable for normal human work environments. Fetch is primarily developed for shelf picking, but the robot is also designed to work well in homes and labs. The arm is designed specifically to be able to reach items on the ground, enabling recovery if an item is dropped during manipulation.

The mobile base is driven by two brushless hub motors in a differential drive configuration.  Each hub motor is held in a drop suspension configuration, allowing the robot to keep traction when crossing obstacles, without allowing the robot to sway side-to-side when manipulating on flat ground. Four casters provide stability duringmovement.  

Each of the Fetch arm joints are built from a harmonic drive coupled to a brushless frameless motor, mounted inside a custom cast aluminum housing. Each joint has two 14-bit absolute magnetic encoders, one coupled to the joint output shaft, and one coupled to the motor backshaft.

The robot has sufficient battery power to work an 8-hour day. This requirement affects both the battery selection as well as other power-related trade-offs such as the choice of the computer processor and communication buses.

References

Elaborate overview of Fetch's specifications, it's degrees of freedom, and it's measurements.

https://fetchrobotics.com

Introduces the technology, related design, and goes into the Fetch robot design. Describes it's applications, and testing.

Melonee Wise, Michael Ferguson, Derek King, et al.

Wevolver 2022