The article is devoted to a motion control problem for a differentially driven mobile robot in the task of trajectory tracking in the presence of skid-slip effects. The kinematic control concept presented in the paper is the Vector Field Orientation (VFO) feedback approach with a nonlinear feed-forward skid-slip influence compensation scheme. The VFO control law guarantees asymptotic convergence of the position tracking error to zero in spite of the disturbing influence of skid-slip phenomena. The paper includes a control law design description, stability and convergence analysis of a closed-loop system, and practical verification of the proposed control concept. The experimental results illustrate control quality obtained on a laboratory setup equipped with vision feedback, where the Kalman filter algorithm was used in order to practically estimate skid-slip components.
Articulated mobile robots consisting of a tractor and passively off-hooked trailers belong to a class of highly nonlinear, nonholonomic, structurally unstable, differentially nonflat, and underactuated dynamic systems. Due to the mentioned properties of their kinematics, motion control problems related to N-trailer robots (N-trailers) are non-trivial and challenging. Cascaded control strategy presented in this paper provides unified solution to the set-point and trajectory tracking control tasks for articulated robots equipped with arbitrary number of passively off-axle hitched trailers. Practically useful features of the proposed controller come from its high scalability and from application of the VectorField-Orientation (VFO) controller in the outer loop, which ensures fast errors convergence and simplicity of control implementation and tuning. Control input limitations of the robot are directly taken into account by utilization of a simple velocity scaling procedure which preserves an instantaneous motion curvature of a tractor. Description
Abstract. The paper presents a localization system for a mobile robot using the vision system and LED markers and considers the problem of velocity and acceleration estimation in the case of planar motions. Theoretical considerations include the principle of measurement and the details of Kalman estimator with illustrations based on experimental setup. The presented measurement system can be used for a realization of advanced control algorithms for skid-steering mobile robots where significant slippage phenomenon appears.
In this paper a concept of ?.ision feedback in control of position of surgical tools for Minimal Invasive Surgery (MIS) is presented. Vision feedback of robotic laparoscope positioning system for MIS is based on recognition of surgical tools on the image coming from a laparoscope camem. This information has to be used for automatic moving of camera during such opemtion. This is particularly useful in surgery, where the tool executes only small displacements. For laparoscopic surgeon it is very most important to keep position of the surgical tool in center of the image. In the paper, experimental results obtained using described method are presented. The prototype surgery telerobotic system is based on the Staubli robot equipped with laparoscopic camera mounted at the force-torque sensor.
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