Balance Feedback Interface

The Balance Feedback Interface (BFI) is a human interface designed for whole-body tracking and bilateral teleoperation control of legged robots. It works as a large haptic device that is able to apply large forces (up to 80N) at the human Center of Mass (CoM). It also has a force plate that measures contact forces with the ground and the human Center of Pressure (CoP).

Some of the early versions: cable driven and underactuated arms

The following version was a 2 DOF pantograph design that just allows planar 2D translation of the end-effector.

The actuators are color coded to the linkages they drive. As a result the end-effector translates in X and Y by moving the motors in parallel.

The following video shows impedance control in each translation axis.

 

 

The final version of the BFI allows unconstrained 6DoF motion of the operator torso and can apply forces and torque on the transversal plane. It was used for most of the experiments controlling HERMES robot. It has three underactuated arms that generate forces and torque on the operator CoM. The Motion Capture Suit is a low-latency acquisiton device (up to 10kHz sampling) that captures the position and orientation of the operator's limbs; it was designed and built by Wyatt Ubellacker.

Here is how if works:

 

Operator first person view of HERMES:

 

Some manipulation tasks:

 

6-axis Force Plate:

For the teleoperation the user stands on a custom made 6-axis large force plate. This design is considerably cheaper ($45 per load cell) than off-the-shelf products (a few thousand of dollars); it also allows me to customize the size of the board for my needs. Current design is about 3ft x 3ft.

It utilizes 7 S-type load cells, thus the design is overconstrained. This was necessary due to the compliance of the board: a 6 load cell design suffers too much deformation. To deal with the overdefined problem a standart Least Squares Regression was sufficient for calibration.