Experimental Evaluation of Dynamic Redundancy Resolution in a Nonholonomic Wheeled Mobile Manipulator

Abstract

Mobile manipulators derive significant novel capabilities for enhanced interactions with the world by merging mobility with manipulation. However, a careful resolution of the redundancy and active control of the reconfigurability, created by the surplus articulated DOFs and actuation, are the keys to unlocking this potential. Nonholonomic wheeled mobile manipulators, formed by mounting manipulator arms on disc-wheeled mobile bases, are a small but important subclass of mobile manipulators. The primary control challenges arise due to the dynamic-level coupling of the nonholonomy of the wheeled mobile bases with the inherent kinematic and actuation redundancy within the articulated chain. The solution approach in this paper builds upon a dynamically consistent and decoupled partitioning of the articulated system dynamics between the external (task) space and internal (null) space. The independent controllers, developed within each decoupled space, facilitate active internal reconfiguration, in addition to resolving redundancy at the dynamic level. Specifically, two variants of null-space controllers are implemented to improve disturbance rejection and active reconfiguration during performance of end-effector tasks by a primary end-effector impedance-mode controller. These algorithms are evaluated within an implementation framework that emphasizes both virtual prototyping and hardware-in-the-loop testing with representative case studies.Index Terms-Dynamic redundancy resolution, hardwarein-the-loop (HIL), nonholonomic wheeled mobile manipulator (NH-WMM), virtual prototyping (VP).

3D Simulator with Hardware-in-the-Loop capability for the Micromouse Competition

“…HIL can be used in mobile robots and manipulators, which are constantly optimizing their performance. The work developed in [10], uses the HIL to test and validate the dynamic and cinematic control of a non holonomic wheeled mobile manipulators. In [11], it was proposed the development of HIL to simulate robotic manipulators with n degrees of freedom, considering the dynamism that occurs when a load is inserted in the system.…”

Whole-Body Impedance Control for a Planetary Rover with Robotic Arm: Theory, Control Design, and Experimental Validation

“…), established techniques such as impedance control [6] can be applied. In [7], a Cartesian impedance controller is proposed for the whole-body coordination of a robotic arm and a two-wheeled nonholonomic, mobile platform. While the authors lay the focus on the redundancy resolution via decoupled null space control, no dedicated multi-task optimization is performed.…”

An Intelligent Robust Tracking Control for a Class of Electrically Driven Mobile Robots

“…In many industrial tasks, such as rolling and cutting motions, the kinematic constraint equations are classical nonholonomic and the dynamics are very well understood . Various control schemes have been developed to address the control design for perturbative nonholonomic mechanical systems .…”

“…In these schemes, only the kinematic model of the mobile robot is considered ( i.e ., the motion model of the vehicle dynamics has been neglected) and the control is designed at the kinematic level with velocity as input. Some approaches also have been presented that integrate a kinematic controller and a torque controller for nonholonomic mobile robots, and various hybrid robust/adaptive control schemes can be found in the literature . The principal limitation of all of the above control schemes is that it is assumed that torques can be applied directly to the mechanical system; that is, the control is designed at a dynamic level with torque as input, but the actuator dynamics are ignored.…”