Approach to the Improvement of Laser Cutting Accuracy for Laminated Solid Manufacture by Dynamic Compensation

2004 ◽  
Vol 471-472 ◽  
pp. 736-740
Author(s):  
G. Wang ◽  
K. Liu
Keyword(s):  
Laser Cutting ◽  
Position Control ◽  
Identification Problem ◽  
Dynamic Parameter ◽  
Torque Control ◽  
Dynamic Compensation ◽  
Dynamic Factors ◽  
Control Scheme ◽  
Parameter Identification Problem ◽  
Dynamic Parameter Identification

Laser cutting process plays a key role in obtaining accurate parts in Laminated Solid Manufacture. Conventional laser cutting machine adopts motion control scheme. For further improving the cutting accuracy, dynamic factors are to be taken into account. The dynamic compensation scheme is proposed. The method combines the advantages of close-loop position control and computed torque control. Different from other presented schemes, the method is not model-based. A multilayer neural network is employed to realize the inverse mechanic dynamics. The complicated dynamic parameter identification problem becomes the learning process under supervision. Experiments have been conducted to verify the proposed method for improving the laser cutting accuracy.

A genetic algorithm-based computed torque control for slider–crank mechanism in the ship’s propeller

2013 ◽  
Vol 228 (12) ◽  
pp. 2090-2099 ◽  
Author(s):  
Farsam Farzadpour ◽  
Hossein Faraji
Keyword(s):  
Genetic Algorithm ◽  
Position Control ◽  
Torque Control ◽  
Process Noise ◽  
Piston Cylinder ◽  
Computed Torque Control ◽  
Control Scheme ◽  
Crank Mechanism ◽  
Parameter Deviation ◽  
Computed Torque

A lot of endeavors regarding the development of slider–crank mechanism in the ship’s propeller have been made and continue to be investigated. This paper presents the position control of a slider–crank mechanism, which is driven by the piston cylinder actuator to adjust the blade pitch angle. An effective motion control strategy known as the computed torque control can ensure global asymptotic stability. However, it is essential for this control scheme to have a precise and accurate system model. Moreover, large amounts of changes in the output and even instability of process are caused by a small amount of measurement or process noise, when the derivative gain is sufficiently large. Accordingly, in order to compensate any parameter deviation and disturbances as well as minimizing errors, we have presented a genetic algorithm-based computed torque control system which adjusts the proportional-derivative gains. Computer simulations are performed which reveals that asymptotically stability is reached and it confirms the effectiveness and high tracking capability of the proposed control scheme.

Position-Based Fractional-Order Impedance Control of a 2 DOF Serial Manipulator

Robotica ◽  
2021 ◽  
pp. 1-15
Author(s):  
Selçuk Kizir ◽  
Ali Elşavi
Keyword(s):  
Fractional Order ◽  
Position Control ◽  
Robot Manipulator ◽  
Impedance Control ◽  
Torque Control ◽  
Control Scheme ◽  
Absorption Performance ◽  
And Performance ◽  
Comparison Of The Results ◽  
Robotic Tasks

SUMMARY Impedance control is one of the interaction and force control methods that has been widely applied in the research of robotics. In this paper, a new position-based fractional-order impedance control scheme is proposed and applied to a 2 DOF serial manipulator. An RR robot manipulator with full arm dynamics and its environment were designed using Matlab/Simulink. The position control of the manipulator was utilized based on computed torque control to cancel out the nonlinearities existing on the dynamic model of the robot. Parameters of classical impedance controller (CIC) and proposed fractional-order impedance controller (FOIC) were optimized in order to minimize impact forces for comparison of the results in three conditions. In CIC condition: three constant parameters of the impedance controller were optimized: in Frac_λμ condition: Only non-integer parameters of the FOIC were re-optimized after the parameters in CIC had been accepted, and in Frac_all condition: all parameters of the FOIC were re-optimized. In order to show the effectiveness of the proposed method, simulations were conducted for all cases and performance indices were computed for the interaction forces. Results showed that impacts were reduced with an improvement of 26.12% from CIC to Frac_ λμ and an improvement of 47.21% from CIC to Frac_all. The proposed scheme improves the impedance behavior and robustness showing better impact absorption performance, which is needed in many challenging robotic tasks and intelligent mechatronic devices.

Continuous Finite-Time Torque Control for Flexible Assistance Exoskeleton with Delay Variation Input

Robotica ◽  
2020 ◽  
pp. 1-26
Author(s):  
Tao Xue ◽  
ZiWei Wang ◽  
Tao Zhang ◽  
Ou Bai ◽  
Meng Zhang ◽  
...  
Keyword(s):  
Finite Time ◽  
Disturbance Rejection ◽  
High Performance ◽  
Control Strategies ◽  
Fractional Power ◽  
Critical Issue ◽  
Human Robot Interaction ◽  
Torque Control ◽  
Finite Time Stability ◽  
Control Scheme

SUMMARY Accurate torque control is a critical issue in the compliant human–robot interaction scenario, which is, however, challenging due to the ever-changing human intentions, input delay, and various disturbances. Even worse, the performances of existing control strategies are limited on account of the compromise between precision and stability. To this end, this paper presents a novel high-performance torque control scheme without compromise. In this scheme, a new nonlinear disturbance observer incorporated with equivalent control concept is proposed, where the faster convergence and stronger anti-noise capability can be obtained simultaneously. Meanwhile, a continuous fractional power control law is designed with an iteration method to address the matched/unmatched disturbance rejection and global finite-time convergence. Moreover, the finite-time stability proof and prescribed control performance are guaranteed using constructed Lyapunov function with adding power integrator technique. Both the simulation and experiments demonstrate enhanced control accuracy, faster convergence rate, perfect disturbance rejection capability, and stronger robustness of the proposed control scheme. Furthermore, the evaluated assistance effects present improved gait patterns and reduced muscle efforts during walking and upstair activity.

CONTROL OF FOREARM MODULE IN UPPER-LIMB REHABILITATION ROBOT FOR REDUCTION AND BIOMECHANICAL ASSESSMENT OF PRONATOR HYPERTONIA OF STROKE PATIENTS

2016 ◽  
Vol 16 (02) ◽  
pp. 1650008 ◽  
Author(s):  
PIN-CHENG KUNG ◽  
CHOU-CHING K. LIN ◽  
SHU-MIN CHEN ◽  
MING-SHAUNG JU
Keyword(s):  
Upper Limb ◽  
Position Control ◽  
Biomechanical Properties ◽  
Torque Control ◽  
Rehabilitation Robot ◽  
Stroke Patients ◽  
Upper Limb Rehabilitation ◽  
Biomechanical Assessment ◽  
Custom Made ◽  
Limb Rehabilitation

Spastic hypertonia causes loss of range of motion (ROM) and contractures in patients with post-stroke hemiparesis. The pronation/supination of the forearm is an essential functional movement in daily activities. We developed a special module for a shoulder-elbow rehabilitation robot for the reduction and biomechanical assessment of pronator/supinator hypertonia of the forearm. The module consisted of a rotational drum driven by an AC servo motor and equipped with an encoder and a custom-made torque sensor. By properly switching the control algorithm between position control and torque control, a hybrid controller able to mimic a therapist’s manual stretching movements was designed. Nine stroke patients were recruited to validate the functions of the module. The results showed that the affected forearms had significant increases in the ROM after five cycles of stretching. Both the passive ROM and the average stiffness were highly correlated to the spasticity of the forearm flexor muscles as measured using the Modified Ashworth Scale (MAS). With the custom-made module and controller, this upper-limb rehabilitation robot may be able to aid physical therapists to reduce hypertonia and quantify biomechanical properties of the muscles for forearm rotation in stroke patients.

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