Learning Visuomotor Policy for Multi-Robot Laser Tag Game
Authors: Kai Li, Shiyu Zhao
Organizations: College of Computer Science and Technology at Zhejiang University, Hangzhou, China. · School of Engineering at Westlake University, Hangzhou, China.
In this paper, we study multi robot laser tag, a simplified yet practical shooting-game-style task. Classic modular approaches on these tasks face challenges such as limited observability and reliance on depth mapping and inter robot communication. To overcome these issues, we present an end-to-end visuomotor policy that maps images directly to robot actions. We train a high performing teacher policy with multi agent reinforcement learning and distill its knowledge into a vision-based student policy. Technical designs, including a permutation-invariant feature extractor and depth heatmap input, improve performance over standard architectures. Our policy outperforms classic methods by 16.7% in hitting accuracy and 6% in collision avoidance, and is successfully deployed on real robots. Code will be released publicly.
Figures & tables
Fig. 1: Illustration of the multi-robot laser tag game. The laser beams shown are virtual for visualization purposes.
Fig. 2: This figure shows the pipeline of our method. The teacher policy takes privileged states and outputs velocity command, and is trained with MARL. The student policy takes a time series of images and outputs velocity command. The student policy imitates the action output of the teacher and is deployed onboard. Shape of each tensor in the policy is shown. N denotes the number of historical images used for the recurrent module. DATv2 is the monocular depth estimation method Depth Anything v2 [ 19 ] .
Fig. 3: Structure of the feature extractor of the teacher policy. Opponent, obstacle and teammate states are encoded with self-attention and summation pooling. Each entity token (White circle) in the figure represents one embedded instance of the obstacle or neighbor robot.
Fig. 4: The original image is sent into YOLOv5 and DATv2 to generate detection results and depth images. The detection results contain two classes, namely the enemy and the ally. A heat map that indicates the detection location is generated for each class. Then the two classes of heat maps are concatenated with the depth image along the channel axis to form the input tensor.
Visual Encoders
Input Types
Simulation Train
Simulation Test
Real-World Test
Time (ms)
AE ↓
Hit@15 ↑
CR[%] ↓
AE ↓
Hit@15 ↑
CR [%] ↓
AE ↓
Hit@15 ↑
CR [%] ↓
ResNet50 [ 23 ]
RGB
0.0012
25.8 ± 6.4
40.0
0.0075
14.3 ± 4.0
66.0
0.0115
0.0 ± 0.0
70.0
21.6 (28.1)
CLIP RNet [ 24 ]
RGB
0.0013
21.8 ± 3.0
54.0
0.0066
6.4 ± 2.4
58.0
0.0102
0.0 ± 0.0
54.0
20.1 (25.4)
DINOv2 [ 25 ]
RGB
0.0020
17.4 ± 3.0
30.0
0.0078
6.1 ± 2.6
40.0
0.0228
0.0 ± 0.0
50.0
137.2 (185.7)
MAE [ 26 ]
RGB
0.0009
33.8 ± 1.8
38.0
0.0015
19.7 ± 3.0
42.0
0.0099
7.8 ± 5.2
44.0
24.9 (28.0)
SimpleCNN
Edges [ 11 ]
0.0006
26.8 ± 2.8
38.0
0.0020
20.8 ± 4.1
46.0
0.0032
12.5 ± 5.9
72.0
7.8 (18.2)
TABLE I: Comparison and ablation of visual encoders and input types, evaluated by Action Error (AE), Collision Rate (CR), and Hit@15. SimpleCNN refers to a lightweight CNN with channel sizes [16, 32, 32] and filter sizes [5, 4, 3]. Onboard inference time (mean with 99% percentile in parentheses) is reported only for the visual encoder. “train” means in the same training environment, and “test” means in unseen test environments. We compare RGB, edge images [ 11 ] , depth, and our input (depth + heatmaps, see Fig. 4 ).
Fig. 5: The first row shows enemy and ally detection results, the second row shows depth maps, and the third row shows full-gradient attention maps [ 29 ] . The attention maps highlight task-relevant regions of the input image, typically focusing on enemy targets and obstacles, consistent with human intuition. The first three columns present simulation data, and the last column presents real-world data.
Action Methods
AE ↓
Hit@15 ↑
Hit@30 ↑
CR [%] ↓
Teacher-MLP
N/A
40.6 ± 1.6
19.0 ± 1.7
6.0
Teacher-SA+SDF [ 7 ]
N/A
40.9 ± 2.4
17.6 ± 2.0
6.0
Teacher-SA [ 6 ]
N/A
42.3 ± 2.0
18.0 ± 2.9
10.0
Teacher-SAP (Ours)
N/A
48.6 ± 1.7
22.1 ± 2.0
10.0
BC-MLP
0.0251
0.0 ± 0.0
0.0 ± 0.0
80.0
BC-LSTM
0.0059
5.3 ± 1.7
0.0 ± 0.0
48.0
TABLE II: The gray rows are results of different teacher policies, and the white are those of the students. Teacher-SAP refers to the teacher policy with our self-attention-and-pooling as the feature extractor. Teacher-SA refers to policy with vanilla self-attention feature extractor used in MARL [ 6 ] without permutation-invariant operators. Teacher-SA+SDF refers to [ 7 ] ’s feature extractor design. BC denotes behavioral cloning.
Fig. 6: The first row shows the trajectories of robots in the laser tag game in simulation. When the firing condition is met, an ally robot fires a laser beam toward the enemy, indicated by the red line. The second row shows the robot motions, with enemies in red and allies in white. Allies maneuver strategically to aim and attack the enemies, while the enemy maneuver to escape.
Fig. 7: Snapshots from the real-world experiment.
Fig. 8: Left : Cumulative distribution function (CDF) of radial distances from the crosshair center. A steeper rise near the origin indicates that more shots are concentrated close to the crosshair, reflecting better laser aiming accuracy. Right : Hit@15 score under different maximum velocities. Both figures illustrate that ours have an improved laser hitting performance.
Methods
Hit@15 ↑
Hit@30 ↑
CR[%] ↓
State Estimation
Control Policy
GT
PD
44.0 ± 1.8
20.0 ± 1.7
34.0
GT
MLP [ 16 ]
44.2 ± 3.0
20.2 ± 1.3
50.0
GT
IBVS [ 30 ]
35.2 ± 5.5
16.0 ± 5.1
68.0
GT
Ours-Teacher
48.6 ± 1.7
22.1 ± 2.0
10.0
BA [ 4 ]
PD
33.0 ± 1.8
13.9 ± 2.4
42.0
TABLE III: Comparison with other methods. GT uses ground-truth states as input. Ours-Teacher refers to the state-based teacher policy, and Ours-Student to the vision-based student policy. Gray rows indicate methods relying on onboard sensing.
Fig. 9: Relative distance and heading between the ally and enemy in one episode, with red segments marking when the enemy is within the shooting zone. The visuomotor policy yields more successful targeting frames than the PD policy.
Visuomotor policy learning trains robots to turn camera observations, often with language and proprioception, into actions for manipulation and navigation.
VLA models are trained to predict robot actions from visual and language observations. This is a natural choice, but it creates a mismatch: VLMs encode rich, high-level representations of scenes and goals, while robot actions are low-level signals with limited task structure. We ask whether changing what the policy is trained to predict, rather than how it is architecturally designed, can yield better and more efficiently trained policies. We propose UVT (Unified Visuomotor Target), a unified latent prediction target that jointly encodes motor control and visual scene transition information, requiring no architectural changes and no additional data. Applied to two representative VLA systems across simulation benchmarks and real bimanual manipulation tasks, UVT improves training efficiency, final task performance, and policy robustness, with particularly strong gains under limited training budgets and challenging environmental conditions. Rollout videos and additional qualitative results are available at our project webpage: https://unified-visuomotor-targets.github.io/
Zhenyang Feng, Unnat Jain
Department of Computer Science, University of California, Irvine
Multi-robot collaboration allows robots to efficiently take on a wide range of tasks, from moving a couch through a doorway to assembling structures on a construction site. However, achieving such coordination in mobile multi-robot settings remains challenging: centralized methods conditioned on the combined observations of a team scale poorly with team size, and decentralized methods that train one policy per robot often require explicit alignment procedures or information sharing at inference time to overcome partial observability. Our key insight is that the visuomotor priors of pretrained vision-language-action (VLA) models should enable reactive, decentralized collaboration from each robot's local observations alone, without these inference-time assumptions. We propose CHORUS, a framework that adapts a single VLA backbone to control diverse, multi-robot teams. At inference time, each robot runs an independent copy of CHORUS, conditioned only on its own observations and a robot-identifying prompt. In real-world experiments including mobile tape measurement, library book handovers, and laundry basket lifting, CHORUS achieves a 64% point improvement over decentralized, from-scratch models, improves reactivity to teammate behavior by 40% points, and outperforms centralized baselines. Together, these results show that a shared VLA backbone is capable of achieving decentralized multi-robot collaboration, without per-robot policies or inter-robot communication at inference.
Adapting visuomotor policies to new manipulation tasks often requires substantial manual engineering or teleoperated data collection. Simulation can provide task-specific data at scale, but constructing the scene, designing expert behavior, and configuring data generation still require significant per-task effort. We present ARSTAG, an agentic Real2Sim2Real system that turns a single RGB image and a natural-language instruction directly into robot policy-learning data. A hierarchy of language agents constructs a task-scoped simulation scene, generates robot-feasible demonstrations, and expands the training distribution through task-consistent randomization, while a coordinator agent manages cross-stage feedback and recovery. Across seven manipulation tasks spanning grasping, placement, and stacking, the ARSTAG-generated demonstrations enable sim-to-real transfer of three visuomotor policy architectures to a dual-arm robot, with pi0.5 achieving an average real-world success rate of 74.6%. Ablations show that task-consistent randomization substantially improves robustness, and policy performance increases with generated dataset size. Project webpage: https://boweili666.github.io/ARSTAG/.
Bowei Li, Yuner Zhang, Changliu Liu
Carnegie Mellon University, Pittsburgh, PA 15213, USA