Switch controllers of an n-link revolute manipulator with a prismatic end-effector for landmark navigation

Abstract

Robotic arms play an indispensable role in multiple sectors such as manufacturing, transportation and healthcare to improve human livelihoods and make possible their endeavors and innovations, which further enhance the quality of our lives. This paper considers such a robotic arm comprised of n revolute links and a prismatic end-effector, where the articulated arm is anchored in a restricted workspace. A new set of stabilizing switched velocity-based continuous controllers was derived using the Lyapunov-based Control Scheme (LbCS) from the category of classical approaches where switching of these nonlinear controllers is invoked by a new rule. The switched controllers enable the end-effector of the robotic arm to navigate autonomously via a series of landmarks, known as hierarchal landmarks, and finally converge to its equilibrium state. The interaction of the inherent attributes of LbCS that are the safeness, shortness and smoothness of paths for motion planning bring about cost and time efficiency of the controllers. The stability of the switched system was proven using Branicky’s stability criteria for switched systems based on multiple Lyapunov functions and was numerically validated using the RK4 method (Runge–Kutta method). Finally, computer simulation results are presented to show the effectiveness of the continuous time-invariant velocity-based controllers.

Linear manipulator: Motion control of an n-link robotic arm mounted on a mobile slider

“…The proposed system has higher flexibility as it can move easily along the rail to perform assigned tasks. Its increased mobility offers better use of space and has the ability to contribute towards high productivity when compared to the anchored manipulators presented in [13] and [18] . The linear manipulator system presented in this study is a modification of existing robotic arms due to its ability to reposition and navigate to distant targets, resulting from a change in work requirements.…”

“…Iqbal et al [42] in 2012 kinematically analyzed and modeled the workspace of the commonly used 6-DOF, 5-link revolute arm manipulator called ED7220C. Unfortunately, in their research, position precision could not be acquired ideally due to inappropriate joint angles arising from non-linearity in mapping angles and improper mechanical coupling of the joints [18] . Asadi et al [43] in 2019 utilized a 6-link revolute arm on a mobile unmanned ground vehicle (UGV) with a stereo camera that was capable of removing obstacles across the UGV's path.…”

“…A predictive control process was taken to determine appropriate input control torques and optimum velocities for the robotic system in the existence of model uncertainties. However, as pointed out in [47] and [18] , executing safe motion of manipulators of various sizes and geometry is challenging yet crucial for any robotic system.…”

“…Several modern applications have benefited from unanchored manipulators, including medical services from wheelchair robots [15] , food delivery services from Segways [16] , and the transportation sector from Uber services [17] . Moreover, the demands of tasks that include repeatability, reduced variability, quality expectations, and lower manufacturing costs have paved the way for unanchored robotic arms to be included in real-life applications such as mining, forestry, exploration, and military [18] . While specific robotic arms offer the best cost investment as they can be reprogrammed or repurposed to meet product variety and life cycles, linear robots, in particular, offer a more versatile solution for these challenges [19] , [7] .…”

“…This modification of the robotic arm concept and the two-step switch movement enables the linear slider to extend the arm's workspace by advancing linearly along the rail towards an elusive target with increased reachability. In comparison, the anchored robotic arm systems mentioned in [13] , [30] , [18] offer a restricted workspace and minimal operational functionalities of the end-effector in performing designated tasks. The proposed unanchored linear manipulator can have real-world applications in industrial sectors requiring process repeatability tasks like material handling and pick-and-place.…”