Global finite-time adaptive control for uncalibrated robot manipulator based on visual servoing

Adaptive cooperative control of networked uncalibrated robotic systems with time‐varying communicating delays

“…For the control of separate robotic systems, various techniques are reported, including adaptive control, variable structure control, adaptive neural control, adaptive fuzzy tracking control, finite‐time control, and visual servo . With the above techniques, different control objectives are accordingly achieved, including finite‐time stability, processing of noncalibration and systemic time‐delays, collision avoidance, and trajectory tracking …”

“…With the advances of servoing control, in particular, the visual servo, control tasks tend to be defined in task space. How to design the controller to conduct task‐space‐defined tasks has been widely discussed in a separated robot system control field, eg . At the mention of the task space, the homogeneous transformation is usually required in the controller design that is obtained from manipulator kinematics.…”

“…But numerical differentiation of the positions, as the most common way is noise prone and the noisy velocities existing in the control input can further deteriorate the system performance.The controllers in the articles all require velocity signal measurements and performances of these controllers will be dramatically deteriorated when feedback state signals contain more noise. To address such problem, some schemes are proposed for the independent robot system visual servoing control . As for the networked robotic system, Liang et al design an observer to estimate the velocities and the estimates that are to replace the actual velocities obtained from the numerical differentiation.…”

“…How to design the controller to conduct task-space-defined tasks has been widely discussed in a separated robot system control field, eg. 8,19,31 At the mention of the task space, the homogeneous transformation is usually required in the controller design that is obtained from manipulator kinematics. Unfortunately, the kinematic parameters may not be accessible or may change during tasks in many industrial circumstances.…”

“…To address such problem, some schemes are proposed for the independent robot system visual servoing control. 19,20 As for the networked robotic system, Liang et al 38 design an observer to estimate the velocities and the estimates that are to replace the actual velocities obtained from the numerical differentiation.On the basis of all above analyses, we can conclude that there are three main difficulties that should be considered in the networked robotic system: uncertainties (of dynamics and camera), time-vary communicating delays and, task-space velocity measurements. When these three facets overlap each other, especially in the highly nonlinear robotic system, it will be a challenge to design a proper controller to achieve cooperative synchronization.…”