Industrial Robot. Barrett Technology. WAM Arm

The WAM™ Arm is a highly dexterous, naturally backdrivable manipulator. The only arm sold in the world with direct-drive capability supported by Transparent Dynamics™ between the motors and joints, so its control of contact forces is robust – independent of mechanical force or torque sensors. It is built to outperform conventional robots with unmatched human-like grace and dexterity.

The WAM™ Arm is available in two main configurations, 4-degree-of-freedom and  7-degree-of-freedom, both with human-like kinematics. The joint ranges exceed  those for conventional robotic arms.

Higher Performance than Conventional Manipulators

Matching advanced electronics with inherently backdrivable cable drives results in superbly graceful motions. Barrett owns the technology for the highest performance servo-electronics available in the world today. These electronics are also the smallest (43 grams) and most power-efficient servo-drive electronics available today.


Shoulder Yaw:
Shoulder Pitch:
Shoulder Roll:
Elbow Joint:
Wrist Yaw:
Wrist Pitch:
Wrist Roll:

Mechanisms Mechanical transmissions based on advanced, patented high-speed cable transmissions and patented zero-backlash, low-friction, cabled differentials.
Mechanical Stiffness 1.5E6 N/m 1.5E6 N/m
Payload 4 kg 3 kg
Reach (w/ hand or gripper tool) 1000 mm 1000 mm
Work Volume 3.5 m3 3.5 m3
Agility Index* (avg. joint mobility in radians raised to the # of dofs) 466 44,000

Peak Velocity

3 m/s 3 m/s
Peak Accel. (at endtip with 1-kg load) 30 m/s2 20 m/s2
Repeatability 1000 µm
100 µm**
2000 µm
200 µm**
Entire Assembly 25 kg 27 kg
Arm beyond shoulder 3.3 kg 5.8 kg
Footprint 0.1 m2
Base Height 160 mm
Motors Neodymium-iron, brushless motors with Pucks providing high-performance space-vector-commutated current amplifier/control
High-Level Interface High-speed network cable (Ethernet and CANbus) and (Ethernet) wireless
High-Level Cartesian Control (Trajectory and/or Force) 500 Hz 500 Hz
Low-Level Joint-Torque Resolution 14-bits 14-bits
Lower-Level Position Feedback
Type 12-bit digital motor position feedback
18-20-bit** joint position feedback
Minimum Joint Resolution 0.005°
Power Requirement
(AC Operation)
100-240 vac    1Φ    50-60 Hz @ 60 watts minimum
(DCN Operation)
24-80 vdc @ 50 watts minimum
Amplifier Cabinet + Controller PC***
Weight 0 kg 0 kg
Depth 0 mm 0 mm
Height 0 mm 0 mm
Arm Cabinet 0 mm 0 mm
Tether Length 0 m 0 m

*The agility index presumes adherence to optimal kinematics, defined as

  • 3 axes intersecting at right angles at the shoulder;
  • 3 axes intersecting at right angles at the wrist as close as possible to the grasp center; and
  • 1 elbow axis at the midpoint between the shoulder and grasp center.

**For high-precision operation, a special, custom version of the WAM may be ordered with precision (metrology-level) joint encoders integrated into all 4 joints of the 4-dof WAM.

***The zero values dramatize the point that Puck electronics eliminate the need for any external amplifier cabinet.  In addition, a PC is incorporated into the base of the WAM, complete with its own video monitor and USB-keyboard jacks.  DC power (24-80 vdc native) operation for mobile applications requires no external power supply.  A simple laptop-sized power supply is included with every WAM for AC operation in any country.  In addition to the embedded-PC jacks, users can control the PC remotely via either standard wired or wireless Ethernet.  Users may also circumvent the internal PC and use their own realtime PC with opto-isolated CANbus card to communicate via CANbus with the motor Pucks™ in the WAM.  Barrett will support users in setting up their own PC if the system is still under warranty or extended warranty.  Alternatively, for a modest fee Barrett will supply a properly configured and tested realtime external PC with opto-isolated CANbus card.  The advantage is that the user can add PCI cards (e.g. for machine vision) so that all realtime actions are handled under a single PC.

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