Pan-preferential stereo IBVS on ARMOS TurtleBot: Design and experimental evaluation

Image-based visual servoing (IBVS) on nonholonomic platforms often suffers from transient conflicts between camera alignment and base motion when the viewpoint is fixed. This work addresses that difficulty by mounting a rectified stereo pair on a controllable pan axis and commanding a two-channel pan-preferential IBVS that regulates image features while the base heading follows the camera yaw. Depth at feature locations is recovered from disparity to build a well-conditioned visual Jacobian, and a damped least-squares inversion with feature weighting produces bounded linear speed and pan-rate commands. The methodology is implemented on the ARMOS TurtleBot differential base equipped with a low-cost ESP32+OV7670 stereo rig, and underpinned by fast encoder-based motor loops and disturbance-observer augmented PD control. Two experimental scenarios (static target and lateral target motion at roughly constant depth) demonstrate consistent feature tracking, smooth camera-base alignment, and tolerance to transient disparity dropouts through outlier rejection and command projection. Across repeated runs the proposed scheme reduces steady error and settling time compared with a fixed-camera baseline while respecting modest computing and driver limits. All components, rates, and bounds are reported to enable replication, and the results indicate that stereo-depth IBVS with pan alignment is feasible on affordable hardware for indoor mobile manipulation and navigation.