Yuanchun Li

Kinematics of Reconfigurable Flexible- Manipulator Using a Local Product-of-Exponentials Formula

The kinematics of reconfigurable flexible-manipulator is automatically generated based on local POE method after investigating its effectiveness on geometric computing aspects. This article addresses both joint and link flexibilities at the same time. And also assumed mode model is provided to establish the flexible link kinematics. In the assumed mode model, all the parameters are considered as functions of time and time-dependent frequency equation is given. Finally, a RRP manipulator is set out to show the accurate kinematics model

A Combined Backstepping Terminal Sliding Mode Algorithm Based Decentralized Control Scheme for Reconfigurable Manipulators

A decentralized control scheme based on a combined backstepping terminal sliding mode algorithm for reconfigurable manipulators is proposed. Based on Lyapunov stability theory, backstepping technique and terminal sliding mode are utilized in the first and second order of the subsystem respectively, the unknown terms and interconnection term are approximated or compensated by neural networks whose weights are updated with adaptive laws. For the serious chatter of the controller with the linear sliding mode, the terminal sliding mode replaced the linear sliding mode. In contrast, the method improves the convergence rate and the tracking accuracy, the control signal is smoother. Finally, the simulation results show the effectiveness of proposed scheme for different configurations with no need to modify any parameters.

Distributed Adaptive Sliding Mode Control of Modular and Reconfigurable Robots

For modular and reconfigurable robots, it is very difficult to design effective controllers due to diverse configurations. Thus, a distributed adaptive sliding mode controller is proposed in this paper to satisfy the concept of modular software. Based on geometric formulation for the dynamics of rigid body, a robot dynamics system can be divided into some subsystems by a decomposing algorithm, and then an adaptive sliding mode controller is designed for each subsystem to handle the modeling uncertainty. These subsystem controllers together constitute a modular control network to achieve stable and reliable motion of a modular and reconfigurable robot. Finally, simulation results show the validity of the proposed distributed adaptive sliding mode controller.

Robust Control of Cooperating Flexible Manipulators Based on Distributed Parameter Model

In this paper, the distributed parameter dynamical model of cooperating flexible manipulators is derived. The obtained distributed parameter model is divided into a lumped parameter subsystem and a distributed parameter subsystem via the singular perturbation method. A combined cooperative control algorithm is proposed which include a robust hybrid controller for the lumped parameter subsystem to track the desired position/force and a distributed parameter feedback controller for the distributed parameter subsystem to suppress the vibration. Stabilization analysis and numerical simulations are carried out and a significant performance is well demonstrated

A New Distributed Control Scheme of Modular and Reconfigurable Robots

For modular and reconfigurable robots, it is very difficult to design effective controllers due to diverse configurations. Thus, a new distributed control scheme is proposed in this paper to satisfy the concept of modular software. Based on geometric formulation for the dynamics of rigid body, a robot dynamics system is divided into some subsystems by a decomposing algorithm, and then a sliding mode controller with an adaptive scheme, is designed for each subsystem to avoid uncertainty during decomposition. These subsystem controllers together constitute a modular control network to achieve stable and reliable motion of a modular and reconfigurable robot. Finally, simulation results show the validity of the decomposing algorithm and proposed sliding mode controller.

Design and Simulation of Theodolite DC Servo Control System Based on Neural Network

According to analysis of the nonlinearities and uncertainties of the theodolite DC servo control system, the RBF and CMAC+PD hybrid neural networks are proposed, and the effectiveness of the control algorithm and the simulations are verified. This has proved that it can be used in many other control fields

6-DOF adaptive sliding mode control of probe hovering in the irregular gravity field

This paper presents a 6-DOF control of probe hovering in the irregular gravity field in the asteroid orbital frame. Considering the requirements of the scientific instruments pointing direction and orbit position in practical missions, the coordinate control of relative attitude and orbit between the probe and target asteroid is imperative. First, a 6-DOF dynamic equation is derived taking the irregular gravitation, model and parameter uncertainties, and external disturbance into account. An adaptive sliding mode controller is designed to guarantee the convergence of the state error in the presence of external disturbances and model uncertainties. The closed-loop system is proved to be uniformly asymptotically stable theoretically. 4769 Castalia is chosen as the target asteroid, numerical simulation results demonstrate that the designed control law can perform well for a hovering mission with good control accuracy.

An energy-based position control and asymptotic stability analysis for manipulator handling a flexible payload

In this paper, an exact dynamic model of manipulator handling a flexible payload is derived by Hamitons principle. On the basis of the distributed parameter model, a position controller is designed by using Lyapunov function related to the total energy of the system. The controller can achieve the given desired link angles and suppress the vibrations of flexible payload. Using the LaSalles invariance principle and the characteristic of the differential operator, the asymptotic stability in the neighbor-hood of the desired states of the closed-loop system is proved. The effectiveness of the control strategy proposed is supported by some simulations.

Study on Decentralized Control of Reconfigurable Manipulator Based on Third-Order ESO

This paper presents a decentralized controller based on third-order extended state observers (ESO) for reconfigurable manipulator with interconnection terms. Coupling interconnection terms of the joints and modeling uncertainties are estimated and compensated real-timely by using third-order ESO. Using particle swarm optimization (PSO), the parameters of ESO were adaptively adjusted. The controller is applied to the trajectory tracking control of 4-DOF reconfigurable manipulator. Simulation results show the effectiveness of the proposed method in treatment of the interconnection terms.

Adaptive control of a rigid manipulator holding a flexible payload driven by an unknown force

This paper presents an adaptive control method for trajectory tracking of a rigid manipulator which holds a flexible payload driven by an unknown force. First, kinematics and dynamics of the payload is derived. After the analysis of the interaction force in the whole system, a model of manipulator is then combined with the payload model, by which the model of the whole system is obtained. The unknown force exerted on the left end of the payload could be identified by some sensors equipped at the wrist of the manipulator. The measurement error of the force is considered when the control scheme is designed. The proposed controller makes the position and orientation of the flexible payload track a desired trajectory while suppressing its vibration in the absence of the gravity force. A control scheme and a parameter update law are derived so that the reference states are guaranteed to converge to a closed ball. Stability of the system is proved by using Lyapunov stability theory. The validity of the proposed scheme is demonstrated by simulations.