用频域方法让机器人学动作时既保路径又不超速。
SPECTRA: Context-Conditioned Spectral Movement Primitives for Robot Skill Generalization

- 用傅里叶系数表示动作,低频部分保留核心轨迹
- 在频域调控相位,使关节速度加速度合规且路径不变
- 适合需要精准路径和动态安全的机械臂操作任务
机器人模仿学习在操作任务中需保持示范动作的几何特征,同时生成动力学可执行的运动。现有方法通常先学习任务依赖轨迹,再通过滤波、平滑或时间缩放施加执行限制,可能导致关键末端执行器路径失真。本文提出频域模仿学习框架Spectral Movement Primitive(SMP),将任务空间技能生成与关节空间执行调节耦合。示范动作以截断的有限时长傅里叶系数表示,低频任务带捕获主导运动几何,高频谐波则显著贡献于导数增长。通过帧感知的上下文条件高斯混合模型/回归(GMM/GMR)先验预测标准任务帧中的任务带系数,再经顺序逆运动学映射至关节空间。相位耦合调节器在不修改谱系数的前提下限制请求的相位进展,从而在保持所表示路径的同时,强制满足关节速度与加速度约束。实验评估了任务带重建、复合示范污染下的鲁棒性、跨板分布外泛化、关节空间动力学合规性、末端执行器路径保持性,并在Franka Panda机器人上部署验证。结果表明:几何重建紧凑,跨未知任务帧传递一致,动态违规与抖动大幅降低,相位调节期间仍能保持预期末端路径。
原文摘要 · Abstract (English)
Robot imitation learning for manipulation should preserve demonstrated task geometry while producing dynamically admissible robot motions. Existing pipelines often learn task-dependent trajectories and impose execution limits afterward through filtering, smoothing, clipping, or time scaling, which may distort task-critical end-effector paths. We propose the Spectral Movement Primitive (SMP), a frequency-domain imitation learning framework that couples task-space skill generation with joint-space execution regulation. Demonstrations are represented by truncated finite-horizon Fourier coefficients. An empirically selected low-frequency task band captures the dominant motion geometry, while higher harmonics contribute disproportionately to derivative growth. A frame-aware context-conditioned GMM/GMR prior predicts the task-band coefficients in a canonical task frame, and the resulting Cartesian trajectory is mapped to joint space through sequential inverse kinematics. A phase-coupled regulator then limits the requested phase progression without modifying the spectral coefficients, thereby enforcing joint velocity and acceleration limits while preserving the represented path. Experiments evaluate task-band reconstruction, robustness to composite demonstration corruption, out-of-distribution cross-board generalization, joint-space dynamic admissibility, end-effector path preservation, and deployment on a Franka Panda robot. Results show compact geometric reconstruction, consistent transfer across unseen task frames, substantial reductions in dynamic violations and jerk, and preservation of the intended end-effector path during phase regulation.
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