Motion Control Of Mobile Manipulators Research Articles

End-Effector Stabilization of a 10-DOF Mobile Manipulator using Nonlinear Model Predictive Control

Abstract Motion control of mobile manipulators (a robotic arm mounted on a mobile base) can be challenging for complex tasks such as material and package handling. In this paper, a task-space stabilization controller based on Nonlinear Model Predictive Control (NMPC) is designed and implemented to a 10 Degrees of Freedom (DOF) mobile manipulator which consists of a 7-DOF robotic arm and a 3-DOF mobile base. The system model is based on kinematic models where the end-effector orientation is parameterized directly by a rotation matrix. The state and control constraints as well as singularity constraints are explicitly included in the NMPC formulation. The controller is tested using real-time simulations, which demonstrate high positioning accuracy with tractable computational cost.

Discrete ZNN models of Adams-Bashforth (AB) type solving various future problems with motion control of mobile manipulator

Zhang neural network (ZNN), being a special type of recurrent neural network, has shown powerful abilities to solve a great variety of continuous time-varying problems. In order to solve future problems (or termed discrete time-varying problems), discrete ZNN (DZNN) models should be developed. In this paper, four kinds of future problems, i.e., future linear system (FLS), future division (FD), future quadratic minimization (FQM), and future equality-constrained quadratic programming (FECQP), are investigated. The DZNN models of Adams-Bashforth (AB) type are thus proposed for solving four kinds of future problems. Compared with conventional DZNN models of Euler type and Taylor type, the performances of DZNN models of AB type in terms of accuracy are better. Meanwhile, the numerical results substantiate the efficacy and superiority of DZNN models of AB type for solving future problems. Furthermore, the motion control of mobile robot manipulator is conducted to substantiate the efficacy of DZNN models of AB type for solving future problems.

Event-driven optimal control for a robotic exploration, pick-up and delivery problem

This paper addresses an Optimal Control Problem (OCP) for a robot that has to find and collect a finite number of objects and move them to a depot in minimum time. The robot has fourth-order dynamics that change instantaneously at any pick-up or drop-off of an object. The objects are represented by point masses in a bounded two-dimensional space that may contain unknown obstacles. The OCP is formulated assuming either a worst-case positioning, or a uniform distribution of the objects (probabilistic case). Modeling the robotic problem by a hybrid system facilitates an event-driven receding horizon solution based on motion parameterization and gradient-based optimization. A comparison of the proposed methods to two simple heuristic approaches in simulation suggests that the event-driven approach offers significant advantages – a lower execution time (on average) and the ability to handle obstacles – over the simple solutions, at the price of a moderately increased computational effort. The methods are relevant for various robotic applications, e.g. the motion control of mobile manipulators for home-care, search and rescue, harvesting, manufacturing etc.

Motion Control of a Nonholonomic Mobile Manipulator in Task Space

AbstractIn this paper, the motion control of a mobile manipulator subjected to nonholonomic constraints is investigated. The control objective is to design a computed‐torque controller based on the coupled dynamics of the mobile manipulator. The proposed controller achieves the capability of simultaneous tracking of a reference velocity for the mobile base and a reference trajectory for the end‐effector. The aforementioned reference velocity and trajectory are defined in the task space, such task setting imitates the actual working conditions of a mobile manipulator and thus makes the control problem practical. To solve this tracking problem, a steering velocity is firstly designed based on the first‐order kinematic model of the nonholonomic mobile base via dynamic feedback linearization. The main merit of the proposed steering velocity design is that it directly utilizes the reference velocity set in the task space without requiring the knowledge of a reference orientation. A torque controller is subsequently developed based on a proposed Lyapunov function which explicitly considers the coupled dynamics of the mobile manipulator to ensure the mobile base and end‐effector track the reference velocity and trajectory respectively. This proposed computed‐torque controller is able to realize asymptotic stability of both the base velocity tracking error and the end‐effector motion tracking error. Simulations are conducted to demonstrate the effectiveness of the proposed controller.

力覚情報による動作修正を用いた移動マニピュレータによる壁拭き動作制御

Mobile manipulation has several control problems such as grasping, pushing and wiping. In this paper, we present a wipe motion control of mobile manipulator which consists of nonholonomic mobile robot and 2-DOF manipulator using hybrid control of position and force. We obtain estimation of first-order approximation of force as a function of control input using actually observed information. To verify effectivity of the inplemented control method, we conducted an experiment of wipe motion control using the approximated linear function.

A New Performance Index for the Repetitive Motion of Mobile Manipulators

A mobile manipulator is a robotic device composed of a mobile platform and a stationary manipulator fixed to the platform. To achieve the repetitive motion control of mobile manipulators, the mobile platform and the manipulator have to realize the repetitive motion simultaneously. To do so, a novel quadratic performance index is, for the first time, designed and presented in this paper, of which the effectiveness is analyzed by following a neural dynamics method. Then, a repetitive motion scheme is proposed by combining the criterion, physical constraints, and integrated kinematical equations of mobile manipulators, which is further reformulated as a quadratic programming (QP) subject to equality and bound constraints. In addition, two important Bridge theorems are established to prove that such a QP can be converted equivalently into a linear variational inequality, and then equivalently into a piecewise-linear projection equation (PLPE). A real-time numerical algorithm based on PLPE is thus developed and applied for the online solution of the resultant QP. Two tracking-path tasks demonstrate the effectiveness and accuracy of the repetitive motion scheme. In addition, comparisons between the nonrepetitive and repetitive motion further validate the superiority and novelty of the proposed scheme.

Adaptive unified motion control of mobile manipulators

This paper presents a unified motion controller for mobile manipulators which not only solves the problems of point stabilization and trajectory tracking but also the path following problem. The control problem is solved based on the kinematic model of the robot. Then, a dynamic compensation is considered based on a dynamic model with inputs being the reference velocities to the mobile platform and the manipulator joints. An adaptive controller for on-line updating the robot dynamics is also proposed. Stability and robustness of the complete control system are proved through the Lyapunov method. The performance of the proposed controller is shown through real experiments.

704 凹凸路面を走行する移動マニュピレータの運動制御 : 実機による路面外乱の定量的評価

704 凹凸路面を走行する移動マニュピレータの運動制御 : 実機による路面外乱の定量的評価

A motion control of mobile manipulator with external force

Describes a stable motion control of a mobile manipulator with the consideration of external force. As is well known, the mobile manipulator has infinite motion area, which brings several sophisticated advantages to the manipulator control. However, the unexpected external force to the mobile manipulator makes its motion unstable since there are no fixed points in the stationary coordinate. To obtain the stable motion independently of the external force, the cooperative control of the manipulator and vehicle parts is strongly required. To address the above issue, the paper presents a stable control strategy for mobile manipulator in the case that an eternal force exists. The validity of the proposed method is confirmed by several experimental results.

A Unified Approach to Motion Control of Mobile Manipulators

This paper presents a simple on-line approach for motion control of mobile manipulators comprising a manipulator arm mounted on a mobile base. The proposed approach is equally applicable to nonholonomic mobile robots such as rover-mounted manipulators and holonomic mobile robots such as tracked robots and compound manipulators. For wheeled mobile robots, the nonholonomic base constraints are incorporated directly into the task formulation as kinematic constraints. The configuration control approach is ex tended to exploit the redundancy introduced by the base mobility to perform a set of user-specified additional tasks during the end- effector motion while satisfying the nonholonomic base constraints (if applicable). This approach treats the base nonholonomy and the kinematic redundancy in a unified manner to formulate new task constraints. The computational efficiency of the proposed control scheme makes it particularly suitable for real-time implementation. Two simulation studies are presented to demonstrate the applica tions of the motion control scheme to a rover-mounted arm (non holonomic system) and to a tracked robot (holonomic system).