CSymPlan: Certified Symbolic Planning and Control for High-DOF Manipulators

Changes in a robot's observations do not automatically imply changes in the task it is solving, but language-conditioned manipulation systems often fail to separate the two. If an object moves, for example, the locations at which actions should be executed may change while the underlying manipulation plan remains valid. We introduce Sequential Planning via Anchored Robotic Keypoints (SPARK), which separates a task's symbolic plan from its execution-time perceptual grounding, and we experimentally isolate whether a fixed symbolic plan can survive substantial changes to the scene through execution-time re-grounding. SPARK represents the task as a symbolic behavior tree whose object references are grounded to current 3D observations during execution, allowing the robot to update where actions are performed while preserving the plan. Runtime verification then enables local recovery and renewed grounding, only resorting to a new plan if necessary. To test the separation between plan and perceptual-grounding, we perform a set of manipulation experiments with a fixed plan while moving objects during execution. Under a 10 cm displacement, verification and adaptation maintain $66.7\%$ task success, compared with $2.2\%$ when disabled, demonstrating the importance of the underlying principle. Without task-specific model training and with an open-weight planner, SPARK also achieves $66.8\%$ mean success across six LIBERO-PRO settings, and $68\%$ across eleven physical task-embodiment settings on three robot platforms. Together, these results show that robustness does not require re-planning the task and for an important class of failures, it is sufficient to preserve the plan and update the system's perception of a changing world. Code and videos can be found at https://cwru-aism.github.io/spark-page/

Large language models can translate natural-language instructions into plausible manipulation plans, but robotic execution requires physically grounded decisions that respect robot embodiment, workspace geometry, reachability, collision constraints, and grasp feasibility. This paper presents a hardware-aware large language model-vision-language model (LLM-VLM) manipulation framework for a simulated Franka Research 3 robot in NVIDIA Isaac Sim. The framework separates symbolic reasoning from metric execution: an API-hosted LLM planner receives a structured scene summary and generates only symbolic task information, including the object to manipulate, target relation, approach preference, and objects to avoid. A local Qwen3-VL 8B VLM verifier supports semantic confirmation of ambiguous objects and open-container surrogates. Both the LLM planner and the VLM verifier are prohibited from generating robot coordinates, grasp poses, keepout dimensions, gripper commands, trajectory waypoints, or success labels. Instead, these decisions are handled by deterministic grounding and execution modules that use the robot model, scene geometry, MoveIt 2 collision checking, inverse kinematics, grasp validation, release verification, and final visual assessment. Execution feedback is returned only as symbolic context for replanning. The framework is evaluated through simulated digital-twin trials involving pickup, occluded-source access, keepout reasoning, relation placement, and sequential manipulation tasks.

Inverting a robotic task requires more than reversing symbolic state transitions or rewinding motor trajectories. In robot manipulation tasks, symbolic inverse plans often fail to fully restore the effects of forward executions under continuous interaction dynamics. We present a hybrid framework for inverse manipulation that derives inverse-skill objectives from STRIPS-like operators automatically extracted from demonstrations through soft geometric predicates. For each extracted operator, we construct an inverse restoration objective that preserves preconditions, restores delete effects, and negates add effects. A task planner first attempts to satisfy this objective using available action primitives. Unresolved symbolic predicates then induce a residual operator learning problem solved through Reinforcement Learning (RL). We evaluate the framework on the ManiSkill3 PushCube task. For a forward pushing skill, the symbolic inverse performs a coarse pick-and-place restoration, while a residual Soft Actor-Critic policy refines the cube pose to satisfy the remaining inverse predicates. Our results show that predicate-derived residual control can turn an approximate symbolic inverse into a physically grounded inverse skill.