Trajectory Tracking Control of Flexible Manipulators Considering Modeling Discrepancy

2005 ◽  
Author(s):  
S. Kilicaslan ◽  
S. K. Ider ◽  
M. K. Ozgoren
Keyword(s):  
Tracking Control ◽  
Control Method ◽  
Feedback Stabilization ◽  
Flexible Manipulators ◽  
Flexible Robot ◽  
Equilibrium Equations ◽  
Trajectory Tracking Control ◽  
Elastic Deformations ◽  
End Effector ◽  
Joint Variable

A new method is proposed for the end-effector motion control of flexible manipulators. The dynamic equations of flexible robot manipulators are partitioned as pseudostatic equilibrium equations and deviations from them. The pseudostatic equilibrium considered here is defined as a hypothetical state where the end-effector motion variables have their desired values while the elastic deformations are instantaneously constant. Then, the control torques for the pseudostatic equilibrium are computed and the feedback stabilization of the deviation equations is achieved using strain gage and joint variable or tip point variable measurements. A planar two link robot with flexible forearm is taken into consideration for demonstration of the method. The elasticity of the forearm is approximately described by the first two modes and a controller is designed using this two-mode model. Furthermore, in order to investigate the effects of modeling discrepancies, a “submodel controller” is considered using a model that has only the first mode. The performances of these two controllers are compared by means of simulations. It is observed that the proposed control method does not seem to be sensitive to the number of modes included in the model of the manipulator.

Control of Constrained Flexible Manipulators

2005 ◽  
Author(s):  
S. Kilicaslan ◽  
M. K. Ozgoren ◽  
S. K. Ider
Keyword(s):  
Force Control ◽  
Feedback Stabilization ◽  
Dynamic Equations ◽  
Flexible Manipulators ◽  
Strain Gages ◽  
Flexible Robot ◽  
Equilibrium Equations ◽  
End Effector ◽  
Tip Position ◽  
Contact Force Control

A new method is proposed for the end-effector motion and contact force control of flexible robot manipulators. The dynamic equations of flexible manipulators are partitioned as pseudostatic equilibrium equations and deviations from them. The pseudostatic equilibrium considered here is defined as a hypothetical state where the end-effector motion variables have their desired values while the elastic deformation variables are instantaneously constant. Then, the portion of the control torques for the pseudostatic equilibrium and the portion for the feedback stabilization of the deviations are generated using the measurement signals taken from the end-effector force and moment sensors, the strain gages and the joint encoders or the tip position sensors. The performance of the proposed method is illustrated on a planar two link robot with flexible forearm which is constrained to move on a cylindrical surface.

Dynamic trajectory-tracking control method of robotic transcranial magnetic stimulation with end-effector gravity compensation based on force sensors

2018 ◽  
Vol 45 (6) ◽  
pp. 722-731
Author(s):  
ZeCai Lin ◽  
Wang Xin ◽  
Jian Yang ◽  
Zhang QingPei ◽  
Lu ZongJie
Keyword(s):  
Neural Networks ◽  
Trajectory Tracking ◽  
Tracking Control ◽  
Magnetic Stimulation ◽  
Control Method ◽  
Gravity Compensation ◽  
Trajectory Tracking Control ◽  
End Effector ◽  
Content Type ◽  
Dynamic Trajectory

Purpose This paper aims to propose a dynamic trajectory-tracking control method for robotic transcranial magnetic stimulation (TMS), based on force sensors, which follows the dynamic movement of the patient’s head during treatment. Design/methodology/approach First, end-effector gravity compensation methods based on kinematics and back-propagation (BP) neural networks are presented and compared. Second, a dynamic trajectory-tracking method is tested using force/position hybrid control. Finally, an adaptive proportional-derivative (PD) controller is adopted to make pose corrections. All the methods are designed for robotic TMS systems. Findings The gravity compensation method, based on BP neural networks for end-effectors, is proposed due to the different zero drifts in different sensors’ postures, modeling errors in the kinematics and the effects of other uncertain factors on the accuracy of gravity compensation. Results indicate that accuracy is improved using this method and the computing load is significantly reduced. The pose correction of the robotic manipulator can be achieved using an adaptive PD hybrid force/position controller. Originality/value A BP neural network-based gravity compensation method is developed and compared with traditional kinematic methods. The adaptive PD control strategy is designed to make the necessary pose corrections more effectively. The proposed methods are verified on a robotic TMS system. Experimental results indicate that the system is effective and flexible for the dynamic trajectory-tracking control of manipulator applications.

Motion control of flexible-link manipulators

2008 ◽  
Vol 222 (12) ◽  
pp. 2441-2453 ◽  
Author(s):  
S Kilicaslan ◽  
S K Ider ◽  
M K Özgören
Keyword(s):  
Equations Of Motion ◽  
Spillover Effect ◽  
Pole Placement ◽  
Feedback Gain ◽  
Control Input ◽  
Flexible Robot ◽  
Trajectory Tracking Control ◽  
End Effector ◽  
Joint Variable ◽  
Computed Torque

A new method is proposed for the end-effector trajectory tracking control of flexible robot manipulators. The equations of motion are separated into two parts that represent the pseudostatic equilibrium and the deviations from it. The part of the control input for the pseudostatic equilibrium is determined algebraically, and the other part of the control input for the stabilization of the deviations is obtained by a state variable feedback law, by using strain, joint variable, and end-effector position measurements. The feedback gain matrix is determined online by continuously updated pole placement. The pseudostatic equilibrium is defined here as a hypothetical state, in which the velocity and acceleration of the end-effector have their desired values whereas the elastic deformations are instantaneously constant. In order to demonstrate the method, a planar two-link robot with a flexible forearm is taken into consideration. The elasticity of the forearm is approximately described by the first two modes, and a controller is designed by using this two-mode model. Furthermore, in order to investigate the effects of modelling discrepancies, a ‘submodel controller’ is designed by using a model with only the first mode and it is applied to the same system with the two-mode model. The performances of these two controllers are compared by means of simulations. The behaviour of the flexible robot is also simulated by using the computed torque method as if the robot is rigid in order to illustrate the importance of including the flexibility effects in the formation of an appropriate control law. The spillover effect that causes the dominant poles to approach towards the imaginary axis is inspected by monitoring the real parts of the dominant poles of the closed-loop system under the effect of the ‘submodel’ and ‘computed torque’ controllers.

scholarly journals A 4-DOF Upper Limb Exoskeleton for Physical Assistance: Design, Modeling, Control and Performance Evaluation

2021 ◽  
Vol 11 (13) ◽  
pp. 5865
Author(s):  
Muhammad Ahsan Gull ◽  
Mikkel Thoegersen ◽  
Stefan Hein Bengtson ◽  
Mostafa Mohammadi ◽  
Lotte N. S. Andreasen Struijk ◽  
...  
Keyword(s):  
Upper Limb ◽  
Tracking Control ◽  
Degrees Of Freedom ◽  
Control Method ◽  
Mechanical Design ◽  
Trajectory Tracking Control ◽  
Upper Limb Exoskeleton ◽  
And Performance ◽  
Physically Disabled People ◽  
Human Upper Limb

Wheelchair mounted upper limb exoskeletons offer an alternative way to support disabled individuals in their activities of daily living (ADL). Key challenges in exoskeleton technology include innovative mechanical design and implementation of a control method that can assure a safe and comfortable interaction between the human upper limb and exoskeleton. In this article, we present a mechanical design of a four degrees of freedom (DOF) wheelchair mounted upper limb exoskeleton. The design takes advantage of non-backdrivable mechanism that can hold the output position without energy consumption and provide assistance to the completely paralyzed users. Moreover, a PD-based trajectory tracking control is implemented to enhance the performance of human exoskeleton system for two different tasks. Preliminary results are provided to show the effectiveness and reliability of using the proposed design for physically disabled people.

Robust finite-time trajectory tracking control for a space manipulator with parametric uncertainties and external disturbances

2021 ◽  
pp. 095441002110147
Author(s):  
Qijia Yao
Keyword(s):  
Trajectory Tracking ◽  
Finite Time ◽  
Tracking Control ◽  
Disturbance Observer ◽  
Control Method ◽  
Parametric Uncertainties ◽  
External Disturbances ◽  
Trajectory Tracking Control ◽  
Space Manipulator ◽  
Tracking Controller

Space manipulator is considered as one of the most promising technologies for future space activities owing to its important role in various on-orbit serving missions. In this study, a robust finite-time tracking control method is proposed for the rapid and accurate trajectory tracking control of an attitude-controlled free-flying space manipulator in the presence of parametric uncertainties and external disturbances. First, a baseline finite-time tracking controller is designed to track the desired position of the space manipulator based on the homogeneous method. Then, a finite-time disturbance observer is designed to accurately estimate the lumped uncertainties. Finally, a robust finite-time tracking controller is developed by integrating the baseline finite-time tracking controller with the finite-time disturbance observer. Rigorous theoretical analysis for the global finite-time stability of the whole closed-loop system is provided. The proposed robust finite-time tracking controller has a relatively simple structure and can guarantee the position and velocity tracking errors converge to zero in finite time even subject to lumped uncertainties. To the best of the authors’ knowledge, there are really limited existing controllers can achieve such excellent performance under the same conditions. Numerical simulations illustrate the effectiveness and superiority of the proposed control method.

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