scholarly journals Suppress Vibration on Robotic Polishing with Impedance Matching

Actuators ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 59
Author(s):  
Junjie Dai ◽  
Chin-Yin Chen ◽  
Renfeng Zhu ◽  
Guilin Yang ◽  
Chongchong Wang ◽  
...  
Keyword(s):  
Contact Force ◽  
Force Control ◽  
Impedance Control ◽  
Impedance Matching ◽  
Industrial Robots ◽  
Contact Phase ◽  
Dynamic Tracking ◽  
Force Tracking ◽  
The Difference ◽  
End Effectors

Installing force-controlled end-effectors on the end of industrial robots has become the mainstream method for robot force control. Additionally, during the polishing process, contact force stability has an important impact on polishing quality. However, due to the difference between the robot structure and the force-controlled end-effector, in the polishing operation, direct force control will have impact during the transition from noncontact to contact between the tool and the workpiece. Although impedance control can solve this problem, industrial robots still produce vibrations with high inertia and low stiffness. Therefore, this research proposes an impedance matching control strategy based on traditional direct force control and impedance control methods to improve this problem. This method’s primary purpose is to avoid force vibration in the contact phase and maintain force–tracking performance during the dynamic tracking phase. Simulation and experimental results show that this method can smoothly track the contact force and reduce vibration compared with traditional force control and impedance control.

Smooth adaptive hybrid impedance control for robotic contact force tracking in dynamic environments

2020 ◽  
Vol 47 (2) ◽  
pp. 231-242
Author(s):  
Hongli Cao ◽  
Ye He ◽  
Xiaoan Chen ◽  
Xue Zhao
Keyword(s):  
Contact Force ◽  
High Speed ◽  
Impedance Control ◽  
Tracking Error ◽  
Industrial Robots ◽  
Force Response ◽  
Impedance Function ◽  
Content Type ◽  
Robot Controller ◽  
Force Tracking

Purpose The purpose of this paper is to take transient contact force response, overshoots and steady-state force tracking error problems into account to form an excellent force controller. Design/methodology/approach The basic impedance function with a pre-PID tuner is designed to improve the force response. A dynamic adaptive adjustment function that combines the advantages of hybrid impedance and adaptive hybrid impedance control is presented to achieve both force overshoots suppressing and tracking ability. Findings The introduced pre-PID tuner impedance function can achieve more than the pure impedance function in aspects of converging to the desired value and reducing the force overshoots. The performance of force overshoots suppression and force tracking error are maintained by introducing the dynamic adaptive sigma adjustment function. The simulation and experimental results both show the achieved control performance by comparing with the previous control methods. Practical implications The implementation of the controller is easy and convenient in practical manufacture scenes that require force control using industrial robots. Originality/value A superior robot controller adapting to a variety of complex tasks owing to the following characteristics: maintenance of high-accuracy position tracking capability in free-space (basic capabilities of modern industrial robots); maintenance of high speed, stability and smooth contact performance in collision stage; and presentation of high-precision force tracking capability in steady contact.

scholarly journals Contact Force Control of Three-Dimensional Flexible Manipulator

2020 ◽  
Author(s):  
Minoru Sasaki ◽  
Shunta Ito ◽  
Daiki Maeno ◽  
Waweru Njeri ◽  
Muguro Josephh ◽  
...  
Keyword(s):  
Contact Force ◽  
Force Control ◽  
Degrees Of Freedom ◽  
Force Feedback ◽  
Three Dimensional ◽  
Flexible Manipulator ◽  
Force Tracking ◽  
Feedback Method ◽  
Three Degrees Of Freedom ◽  
Contact Force Control

This paper proposes a contact force controller for a constrained flexible manipulator in three-dimensional motion. This controller used the conversion formula obtained empirically and experimental results showed the effectiveness of the proposed contact force controller. First, the manipulator was operated with the tip of the second link restrained, then, time response of the root strain, joint angles and contact force were used to derive the relational between the three quantities. The effectiveness of the relational expression was verified by conducting a target contact force tracking experiment by inputting the angle from the relational expression. The contact force control using the strain feedback method was proposed with the strain amount estimated from the target contact force as the target value, and its effectiveness was verified by experiments. From the results obtained, controller using the strain feedback method was designed for the purpose of controlling the contact force at the tip of a flexible manipulator with two links and three degrees of freedom that performs three-dimensional spatial motion, and its effectiveness was shown by comparison with the contact force feedback method.

scholarly journals Robust state dependent Riccati equation variable impedance control for robotic force-tracking tasks

2020 ◽  
Vol 4 (4) ◽  
pp. 507-519
Author(s):  
Loris Roveda ◽  
Dario Piga
Keyword(s):  
Riccati Equation ◽  
High Performance ◽  
Impedance Control ◽  
Industrial Robots ◽  
Intrinsic Variability ◽  
State Dependent ◽  
Force Tracking ◽  
Lqr Controller ◽  
Improved Performance ◽  
The Stability

AbstractIndustrial robots are increasingly used in highly flexible interaction tasks, where the intrinsic variability makes difficult to pre-program the manipulator for all the different scenarios. In such applications, interaction environments are commonly (partially) unknown to the robot, requiring the implemented controllers to take in charge for the stability of the interaction. While standard controllers are sensor-based, there is a growing need to make sensorless robots (i.e., most of the commercial robots are not equipped with force/torque sensors) able to sense the environment, properly reacting to the established interaction. This paper proposes a new methodology to sensorless force control manipulators. On the basis of sensorless Cartesian impedance control, an Extended Kalman Filter (EKF) is designed to estimate the interaction exchanged between the robot and the environment. Such an estimation is then used in order to close a robust high-performance force loop, designed exploiting a variable impedance control and a State Dependent Riccati Equation (SDRE) force controller. The described approach has been validated in simulations. A Franka EMIKA panda robot has been considered as a test platform. A probing task involving different materials (i.e., with different stiffness properties) has been considered to show the capabilities of the developed EKF (able to converge with limited errors) and controller (preserving stability and avoiding overshoots). The proposed controller has been compared with an LQR controller to show its improved performance.

An Adaptive Approach to Motion and Force Control of Multiple Coordinated Robots

1993 ◽  
Vol 115 (1) ◽  
pp. 60-69 ◽  
Author(s):  
Yan-Ru Hu ◽  
A. A. Goldenberg
Keyword(s):  
Contact Force ◽  
Force Control ◽  
Lyapunov Stability Theory ◽  
Internal Force ◽  
Object Motion ◽  
Tracking Accuracy ◽  
Unknown Parameters ◽  
Adaptive Law ◽  
Control Scheme ◽  
Force Tracking

In this paper an approach to motion and force control of multiple coordinated robots, based on an adaptive scheme, is developed. The approach can be used to control the motion of an object held by the robots, the contact force between the object and the environment, and the internal force which do not contribute to the object motion and contact force. Three subsystem error equations are generated, i.e., position error subsystem, contact force error subsystem, and internal force error subsystem. The adaptive law is derived to estimate the unknown parameters of the multiple coordinated robots, the object, and the environment in terms of the three error subsystem equations. The convergence of the position, contact, internal force errors, and parameter errors is analyzed based on the Lyapunov stability theory. The paper shows that the adaptive control scheme improves the position, and the internal and contact force tracking accuracy for a class of robotic systems with uncertain knowledge of the dynamic model.

Force Control of a Robot Arm During Contact Task

2002 ◽  
Author(s):  
A. Yetik ◽  
V. Karadag
Keyword(s):  
Force Control ◽  
Control Algorithm ◽  
Force Feedback ◽  
Impedance Control ◽  
Mechanical Impedance ◽  
Contact Forces ◽  
Working Environment ◽  
Robot Arm ◽  
Simulation Results ◽  
End Effectors

There are extremely important applications to investigate the control of contact between the end-effectors and the object. During controlling an object, static or in motion, the robot arm should not be damaged. Forces are important in such conditions. The forces between the end-effectors and the object have to be controlled. The motion of the robot arm changes forces. Thats why, to control forces, a force kontrol algorithm must be developed. Previous conventional force control algorithms could not control the robot effectively by only considering the variation of working environment. In this study, a control algorithm strategy to achieve the desired interactions forces between the robot end-effector and the environment during contact tasks, has been developed. The surface of the object and robot are very stiff, thus contact spring coefficient Kc is very large, because of this Kc effect, the results of the forces simulation results, but we get suitable results. Study include, modelling robot arm, evaluating measured forces during contact and constructing a suitable force control algorithm, dynamics, kinematics and simulation results. In this study, we used impedans control which the surface of the object is very stiff, as known as impedance control does not try to track position and force trajectories directly, but rather to regulate the dynamic relationship between the contact forces and manipulator positions, namely the mechanical impedance. Impedance control focused on the design of a robot’s dynamic behavior as seen from the environment. In this control strategy, no hardware or software, switch is needed in the robot’s control system when the robot travels from the free motion space to the constrained space. The force feedback loop closes naturally as soon as the robot interacts with the environment, which changes the robot’s impedance as seen from the environment. By controlling the manipulator positions, and regulating their relationship to the contact forces, the manipulator can be controlled to maintain appropriate contact forces.

scholarly journals Efficient Force Control Learning System for Industrial Robots Based on Variable Impedance Control

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2539 ◽  
Author(s):  
Chao Li ◽  
Zhi Zhang ◽  
Guihua Xia ◽  
Xinru Xie ◽  
Qidan Zhu
Keyword(s):  
Force Control ◽  
Process Model ◽  
Control Method ◽  
Impedance Control ◽  
Experimental Tests ◽  
Industrial Robots ◽  
Learning System ◽  
Control Learning ◽  
Efficient Learning

Learning variable impedance control is a powerful method to improve the performance of force control. However, current methods typically require too many interactions to achieve good performance. Data-inefficiency has limited these methods to learn force-sensitive tasks in real systems. In order to improve the sampling efficiency and decrease the required interactions during the learning process, this paper develops a data-efficient learning variable impedance control method that enables the industrial robots automatically learn to control the contact force in the unstructured environment. To this end, a Gaussian process model is learned as a faithful proxy of the system, which is then used to predict long-term state evolution for internal simulation, allowing for efficient strategy updates. The effects of model bias are reduced effectively by incorporating model uncertainty into long-term planning. Then the impedance profiles are regulated online according to the learned humanlike impedance strategy. In this way, the flexibility and adaptivity of the system could be enhanced. Both simulated and experimental tests have been performed on an industrial manipulator to verify the performance of the proposed method.

scholarly journals Adjusting the parameters of the mechanical impedance for velocity, impact and force control

Robotica ◽  
2011 ◽  
Vol 30 (4) ◽  
pp. 583-597 ◽  
Author(s):  
Ranko Zotovic Stanisic ◽  
Ángel Valera Fernández
Keyword(s):  
Force Control ◽  
Impedance Control ◽  
Mechanical Impedance ◽  
Optimal Switching ◽  
Additional Measure ◽  
Force Tracking ◽  
Impact Attenuation ◽  
Active Impedance ◽  
The Impact ◽  
Selection Of

SUMMARYThis work is dedicated to the analysis of the application of active impedance control for the realisation of three objectives simultaneously: velocity regulation in free motion, impact attenuation and finally force tracking. At first, a brief analysis of active impedance control is made, deducing the value of each parameter in order to achieve the three objectives. It is demonstrated that the system may be made overdamped with the adequate selection of the parameters if the characteristics of the environment are known, avoiding high overshoots of force during the impact. The second and most important contribution of this work is an additional measure for impact control in the case when the characteristics of the environment are unknown. It consists in switching among different values of the parameters of the impedance in order to dissipate faster the energy of the system, limiting the peaks of force and avoiding losses of contact. The optimal switching criteria are deduced for every parameter in order to dissipate the energy of the system as fast as possible. The results are verified in simulation.

scholarly journals Adaptive Impedance Control of a Novel Automated Umbilical System for Propellant Loading

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4900
Author(s):  
Han Tao ◽  
Dacheng Cong
Keyword(s):  
Control Algorithm ◽  
Impedance Control ◽  
Hydraulic Drive ◽  
State Feedback Control ◽  
Dynamic Tracking ◽  
Force Tracking ◽  
High Measurement ◽  
Nonlinear Compensation ◽  
Adaptive Impedance Control ◽  
And Control

In this paper, an automated umbilical system based on a 6-dof (degree of freedom) hydraulic parallel mechanism is proposed to automate the rocket propellant loading process. The mechanical structure, vision acquisition algorithm, and control algorithm used in the system are described in detail in the paper. To address the fluid nonlinearity problem of the hydraulic drive system, nonlinear compensation and three-state feedback control are used in the paper to enhance the performance of the hydraulic system. For the problem of force tracking during the docking process between the umbilical system and the rocket, an adaptive impedance control algorithm based on the online environmental parameter estimation is proposed in the paper, which effectively reduces the contact force during the docking process. The dynamic tracking and docking experiments indicate that this automated umbilical system features rapid reaction speed, high measurement precision, and good flexibility, which can be used to realize the auto-mating and following task for the propellant loading robot in a hazardous environment.

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