Voxel-grid reinforcement learning is widely adopted for path planning in redundant manipulators due to its simplicity and reproducibility. However, direct execution through point-wise numerical inverse kinematics on 7-DoF arms often yields step-size jitter, abrupt joint transitions, and instability near singular configurations. This work proposes a bridging framework between discrete planning and continuous execution without modifying the discrete planner itself. On the planning side, step-normalized 26-neighbor Cartesian actions and a geometric tie-breaking mechanism are introduced to suppress unnecessary turns and eliminate step-size oscillations. On the execution side, a task-priority damped least-squares (TP-DLS) inverse kinematics layer is implemented. This layer treats end-effector position as a primary task, while posture and joint centering are handled as subordinate tasks projected into the null space, combined with trust-region clipping and joint velocity constraints. On a 7-DoF manipulator in random sparse, medium, and dense environments, this bridge raises planning success in dense scenes from about 0.58 to 1.00, shortens representative path length from roughly 1.53 m to 1.10 m, and while keeping end-effector error below 1 mm, reduces peak joint accelerations by over an order of magnitude, substantially improving the continuous execution quality of voxel-based RL paths on redundant manipulators.
Figures & tables
Figure 1: Conceptual motivation . Left: classical planning - feasible collision-free path ( Q1 ); Right: practical deployment - high-quality path ( Q2 ). The proposed method meets the second requirement by bridging a voxel RL planner with a continuous execution layer on a redundant manipulator.
Figure 2: Overall architecture of the proposed bridging framework combining discrete Q-learning planning, geometric regularization, and continuous TP-DLS execution.
Figure 3: Qualitative comparison on a 7-DoF arm. (a) Baseline (unnormalised actions + Num-IK) shows irregular steps and joint-limit configurations. (b) Proposed bridge (normalised 26-neighbour + TP–DLS) equalises step size and keeps joints away from limits.
Density
Algorithm
Success rate
Length
Turns
MinClearance
Steps
Sparse
Original
0.68
192.572
1862.9
0.213
2126.72
Sparse
NoNorm
0.6
283.35
1451.42
0.213
2563.84
Sparse
Improved
1.0
0.602
4.26
0.216
7.02
Medium
Original
0.68
168.516
1681.98
0.157
1926.16
Medium
NoNorm
0.7
195.7
1122.5
0.152
1725.12
Medium
Improved
1.0
0.598
3.98
0.165
6.98
Table 1: Three Planners Under Different Obstacle Densities
Density
Solver
Success_rate
DQ_95
MaxVel
MaxAcc
JointMargin
Backtracks
Sparse
Num-IK
1.0
0.8211
141.8634
12701.6607
0.0053
7.18
0.7231
Sparse
TP-DLS
1.0
0.0113
84.2102
3943.5816
0.0126
19.44
Medium
Num-IK
1.0
0.6415
190.3101
16793.8613
0.0045
6.5
Medium
TP-DLS
1.0
0.0113
79.747
3860.0759
0.0112
37.6
Dense
Num-IK
1.0
0.937
175.8501
15659.236
0.0002
5.48
Dense
TP-DLS
1.0
0.0088
91.651
4438.005
0.014
22.16
Table 2: Two Execution Layers Under the Same Reference Trajectory
In real-world reinforcement learning (RL), the choice of action space can play a key role in shaping motion smoothness, safety, and overall task performance. In this study, we evaluate pose increment, pose velocity, joint position increment, and joint velocity across two vision-based manipulation tasks: object picking and pushing. We train policies in simulation and deploy them to the real world using sim-to-real transfer. We find that action-space representation indeed significantly affects sim-to-real performance. In particular, we find that the joint velocity action space is best for the vision-based picking and pushing tasks in terms of smoothness and final task performance. We also provide practical guidance for RL practitioners in choosing action spaces for both simulation and real-world experiments.
Department of Computing Science, University of Alberta · National Research Council Canada · School of Electrical Engineering and Computer Science, University of Ottawa +3
Reasoning-based robotic policies using large language and vision-language models achieve strong semantic planning capabilities but mostly suffer from a high inference latency that limits practical real-time deployment. In this work, we observe that robotic reasoning workloads contain substantial temporal redundancy, where consecutive observations frequently produce identical actions and subgoals. Based on this insight, we present REIS, a human cognition inspired robotic decision-making framework that minimizes unnecessary reasoning while preserving semantic adaptability. REIS combines lightweight scene gating, KV-steered affordance routing, and deliberative reasoning to accelerate robotic control under embodied constraints. Experiments on ALFRED, and real-world robotic tasks demonstrate that REIS significantly suppresses reasoning overhead while maintaining competitive task performance.
Joonhee Lee, Hyunseung Shin, Hyunmi Kim +2
School of Integrated Technology, College of Computing, Yonsei University · Department of Hyperscale AI SoC Research Section, ETRI · 3EECS - Electrical and Computer Engineering, University of Michigan
This paper addresses a fundamental problem of visuomotor policy learning for robotic manipulation: how to enhance robustness in out-of-distribution execution errors or dynamically re-routing trajectories, where the model relies solely on the original expert demonstrations for training. We introduce the Referring-Aware Visuomotor Policy (ReV), a closed-loop framework that can adapt to unforeseen circumstances by instantly incorporating sparse referring points provided by a human or a high-level reasoning planner. Specifically, ReV leverages the coupled diffusion heads to preserve standard task execution patterns while seamlessly integrating sparse referring via a trajectory-steering strategy. Upon receiving a specific referring point, the global diffusion head firstly generates a sequence of globally consistent yet temporally sparse action anchors, while identifies the precise temporal position for the referring point within this sequence. Subsequently, the local diffusion head adaptively interpolates adjacent anchors based on the current temporal position for specific tasks. This closed-loop process repeats at every execution step, enabling real-time trajectory replanning in response to dynamic changes in the scene. In practice, rather than relying on elaborate annotations, ReV is trained only by applying targeted perturbations to expert demonstrations. Without any additional data or fine-tuning scheme, ReV achieve higher success rates across challenging simulated and real-world tasks.