SeeBFMBehavior Foundation Model That Sees

Prompt the what, perceive the how.
Thanh Ly1,✉, Truong-Duy Dang1, Hung Nguyen2, Duy M. H. Nguyen3,4,5, Vien Anh Ngo1,6, An T. Le1,6,7,✉
1VinRobotics, Vietnam  ·  2UC San Diego, USA  ·  3DFKI, Germany  ·  4University of Stuttgart, Germany  ·  5IMPRS-IS, Germany  ·  6CAIR, VinUni, Vietnam  ·  7IAS, TU Darmstadt, Germany  ·  ✉corresponding authors
Paper, after reviewCode, laterPlayground

SeeBFM is BFM-Zero trained further with a height scan of the ground around the robot. A reward, a motion or a typed sentence becomes one prompt, and the policy reads the ground to carry it out.

54%
of 0.10–0.15 m stairs crossed going up, where BFM-Zero crosses none
Trained further from BFM-Zero's released weights, the model learns to see the ground and keeps its prompts.

With its scan made to read level ground, it crosses 4%.

76% · 12%
of flat-ground speed kept on stairs and boxes, walking forward and walking backward
On stairs and boxes it keeps walking forward but nearly stops walking backward.

Trained the same way without the scan, it keeps 76% of its backward speed there, and falls.

2 cameras
on the robot, in place of the scan
The same policy runs from depth cameras and takes typed commands.

A student turns the two cameras' depth into the scan, and a sentence encoder turns a command into a prompt.

Same prompt, every terrain

Pick a prompt and a model to see them on four grounds at once. The bar under each clip shows how all its attempts on 0.10–0.15 m steps ended.

PROMPT
COMPARE
MODEL
TERRAIN
 

Ways to prompt it

Each clip names its prompt. The numbers under it count all attempts of that kind.

Playground

Pick a model, a prompt and a terrain, and replay any of its attempts in 3D. It holds 31,528 attempts from simulation: SeeBFM with 22 reward prompts and 121 typed sentences, and the three other models with the six locomotion prompts.

Open the playground

How it works

01

Every network that acts or judges sees the ground

A 598-point height scan enters the policy and the networks that score it, each through a layer that starts at zero, so training begins exactly at BFM-Zero.

02

Prompts stay as they were

The network that turns a reward into a prompt still reads only the body, so one reward gives one prompt on every terrain. Subtracting that network's average from each prompt keeps every walking prompt going the way it names.

03

Cameras replace the scan

A student learns to predict the scan from a head and a body camera, first by matching the scan and then by matching the policy's actions.

04

Words become prompts

A sentence encoder and a small network, trained on the descriptions that come with the motion data, map a typed command to a prompt.

The SeeBFM pipeline: motion data, pretraining with a height scan, prompting, and the depth student
The pipeline. Select to open it full size.
height scan, 598 pointshead camera

The scan's points on the stairs ahead, which the policy reads, and the head camera's view, which the depth student uses.

379 hof motion from seven datasets, against BFM-Zero's 2.4 h
78 hof it on stairs, boxes and other terrain
598scan points on two grids around the feet
97.7%of footholds in the next half second land inside the scan

Results

How the six locomotion prompts do on 0.10–0.15 m steps. On flat ground SeeBFM also tracks motion better than BFM-Zero, with an error of 0.68 against 0.93.

MODEL, FOR THE TWO CHARTS BELOW

What we learned

01

Keep the prompt network blind

The network that turns a reward into a prompt gives the same prompt on every terrain if it never sees the ground. Giving it the scan made terrain tracking worse, with an error of 1.31 against 1.14.

How it works
02

Remove the prompt network's average

Without that, every prompt leans toward one shared behavior. On flat ground the sideways prompt then moves at only 0.05 to 0.36 m/s in its direction, and at 0.73 to 0.88 m/s once the average is removed.

How it works
03

Seeing the ground can make a prompt stop

Backward and sideways walking nearly stop on stairs and boxes, and the robot learns this along with the scan. Adding 30 h of that motion on stairs and boxes to the data left both below a third of their flat-ground speed there, so the cause is still open.

Speed kept on relief
04

Words inherit the terrain skill

Typed wordings that make the robot walk on flat ground cross stairs, boxes, slopes and obstacles in 86 to 97% of attempts, against 93% for the reward prompt. One prompt per command cannot hold a jump.

Typed commands

With depth cameras

A real robot has no height scan, so a student learns to predict it from a head camera and a body camera, and the policy reads the prediction instead. It crosses stairs nearly as often as with the perfect scan but falls more, mostly on ground the cameras had not yet seen.

TERRAIN
The depth student: teacher rollouts, two depth cameras, the student network, training in two stages
How the student is trained. Select to open it full size.

Limitations

  • Walking backward or sideways nearly stops on stairs and boxes.
  • Blocks much taller than 25 cm are not climbed.
  • The camera student is weakest going down stairs.
  • It follows about half of the typed wordings it has never seen, and none that ask it to jump or to wave while walking.
  • Tracking recorded stair climbs, it climbs in only 10 of 70 clips.
  • Tracking on terrain improves no faster than on flat ground.
  • Everything so far is in simulation. We are preparing tests on a real Unitree G1 with the camera student, on flat ground first and then on steps.
Overview
The pipeline
The SeeBFM pipeline, full size
The depth student
The depth student's pipeline, full size