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Krzysztof Wojciechowski

Publications and source records attributed to Krzysztof Wojciechowski.

3 recordsLinked to original sources

Learning-Guided Force-Feedback Model Predictive Control with Obstacle Avoidance for Robotic Deburring

Model Predictive Control (MPC) is widely used for torque-controlled robots, but classical formulations often neglect real-time force feedback and struggle with contact-rich industrial tasks under collision constraints. Deburring in particular requires precise tool insertion, stable force regulation, and collision-free circular motions in challenging configurations, which exceeds the capability of standard MPC pipelines. We propose a framework that integrates force-feedback MPC with diffusion-based motion priors to address these challenges. The diffusion model serves as a memory of motion strategies, providing robust initialization and adaptation across multiple task instances, while MPC ensures safe execution with explicit force tracking, torque feasibility, and collision avoidance. We validate our approach on a torque-controlled manipulator performing industrial deburring tasks. Experiments demonstrate reliable tool insertion, accurate normal force tracking, and circular deburring motions even in hard-to-reach configurations and under obstacle constraints. To our knowledge, this is the first integration of diffusion motion priors with force-feedback MPC for collision-aware, contact-rich industrial tasks.

cs.RO↗

Warm-Starting Collision-Free Model Predictive Control With Object-Centric Diffusion

Acting in cluttered environments requires predicting and avoiding collisions while still achieving precise control. Conventional optimization-based controllers can enforce physical constraints, but they struggle to produce feasible solutions quickly when many obstacles are present. Diffusion models can generate diverse trajectories around obstacles, yet prior approaches lacked a general and efficient way to condition them on scene structure. In this paper, we show that combining diffusion-based warm-starting conditioned with a latent object-centric representation of the scene and with a collision-aware model predictive controller (MPC) yields reliable and efficient motion generation under strict time limits. Our approach conditions a diffusion transformer on the system state, task, and surroundings, using an object-centric slot attention mechanism to provide a compact obstacle representation suitable for control. The sampled trajectories are refined by an optimal control problem that enforces rigid-body dynamics and signed-distance collision constraints, producing feasible motions in real time. On benchmark tasks, this hybrid method achieved markedly higher success rates and lower latency than sampling-based planners or either component alone. Real-robot experiments with a torque-controlled Panda confirm reliable and safe execution with MPC.

cs.RO↗

Synergistic effect of workfunction and acoustic impedance mismatch for improved thermoelectric performance in GeTe/WC composite

The preparation of composite materials is promising for concurrent optimization of electrical and thermal transport properties to realize an improved thermoelectric (TE) performance. We report the effect of work function and acoustic impedance mismatch (AIM) on the TE properties of (1-z)Ge0.87Mn0.05Sb0.08Te/(z)WC composite. In particular, a composite consisting of Mn and Sb co-doped GeTe as a matrix and WC as a dispersed phase is prepared, and its structural and TE properties are investigated. The simultaneous increase in electrical conductivity (σ) and Seebeck coefficient (α) with WC volume fraction (z) results in an enhanced power factor (α^2σ) in the composite. The rise in σ is attributed to increased carrier mobility in the composite. This is further established from the work function measurement using the Kelvin probe force microscopy (KPFM) technique and is also supported by the density functional theory (DFT) calculations. The difference in elastic properties (sound velocity) between Ge0.87Mn0.05Sb0.08Te and WC results in a high AIM that leads to a large interface thermal resistance (Rint) between the phases. The correlation between Rint and the Kapitza radius results in reduced phonon thermal conductivity (κ_ph) of the composite and is discussed using the Bruggeman asymmetrical model. The decrease in κ_{ph} is further established using phonon dispersion calculations that indicates the decrease in phonon group velocity in the composite. The simultaneous effect of enhanced α^2σ and reduced κ_ph results in a maximum figure of merit (zT) of 1.93 at 773K for (1-z)Ge0.87Mn0.05Sb0.08Te/(z)WC composite having z=0.010. This study shows promise to achieve higher zTav across a wide range of composite materials having similar electronic structure and different elastic properties.

physics.app-ph↗