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 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.

Advanced force control of the 2-axes PAM-based manipulator using adaptive neural networks

Robotica ◽  
2018 ◽  
Vol 36 (9) ◽  
pp. 1333-1362
Author(s):  
Ho Pham Huy Anh ◽  
Cao Van Kien ◽  
Nguyen Thanh Nam
Keyword(s):  
Contact Force ◽  
Force Control ◽  
Control Method ◽  
Artificial Muscle ◽  
Experimental Tests ◽  
The Novel ◽  
Force Output ◽  
Force Dynamics ◽  
Output Performance ◽  
Highly Nonlinear

SUMMARYThis paper proposes a detailed investigation on the new neural-based feed-forward PID direct force control (FNN-PID-DF) approach applied to a highly nonlinear 2-axes pneumatic artificial muscle (PAM) manipulator in order to ameliorate its force output performance. Founded on the novel inverse neural NARX model dynamically identified to learn well all nonlinear characteristics of the contact force dynamics of the 2-axes PAM-based manipulator, the novel proposed neural FNN-PID-DF force controller is innovatively implemented in order to directly force control the 2-axes PAM robot system used as a rehabilitation device subjected to internal systematic interactions and external contact force deviations. The performance of the experimental tests has proven the advantages and merits of the new force control method compared to the classical PID force control method. The new neural FNN-PID-DF force controller guides the wrist/hand of subject/patient to successfully generate the predefined desired force values.

Control of an operator-assisted mobile robotic system

Robotica ◽  
2002 ◽  
Vol 20 (4) ◽  
pp. 439-446 ◽  
Author(s):  
Jae H. Chung
Keyword(s):  
Force Control ◽  
Control Method ◽  
Impedance Control ◽  
Robotic System ◽  
High Load ◽  
Mobile Platform ◽  
System Response ◽  
Control Performance ◽  
Wheel Slip ◽  
Simple Operator

In this paper, two different control methods are developed for an operator-assisted mobile robotic system for high load applications. For high load applications of mobile robots, an accurate tire model that considers wheel slip needs to be studied to achieve robustness of the system response. First, a simple operator-manipulator coordination system is developed based on explicit force control. Then, a position controller for the platform is designed to minimize the effect of wheel slip on control performance and integrated with the force controller for the operator-manipulator subsystem based on a motion coordination scheme. Then, a new type of human-robot coordination control method is developed, in which robust force control of the manipulator and impedance control of the mobile platform are integrated to achieve robust response and smooth interaction between the operator, the manipulator and the mobile platform. In simulation, the developed methods are compared for control performance on following the operator's motion intention.

Collision detection and force control based on the impedance approach and dynamic modelling

2019 ◽  
Vol 47 (6) ◽  
pp. 813-824
Author(s):  
Pengcheng Wang ◽  
Dengfeng Zhang ◽  
Baochun Lu
Keyword(s):  
Collision Detection ◽  
Force Control ◽  
Control Method ◽  
Impedance Control ◽  
Dynamic Modelling ◽  
Band Pass Filter ◽  
Pass Filter ◽  
Content Type ◽  
Control Approach ◽  
Collision Problem

Purpose This paper aims to address the collision problem between robot and the external environment (including human) in an unstructured situation. A new collision detection and torque optimization control method is proposed. Design/methodology/approach Firstly, when the collision appears, a second-order Taylor observer is proposed to estimate the residual value. Secondly, the band-pass filter is used to reduce the high-frequency torque modeling dynamic uncertainty. With the estimate information and the torque value, a variable impedance control approach is then synthesized to guarantee that the collision is avoided or the collision will be terminated with different contact models and positions. However, in terms of adaptive linear force error, the variation of the thickness of the boundary layer is controlled by the new proximity function. Findings Finally, the experimental results show the better performance of the proposed control method, realizing the force control during the collision process. Originality/value Origin approach and origin experiment.

High-bandwidth force and impedance control for industrial robots

Robotica ◽  
1998 ◽  
Vol 16 (1) ◽  
pp. 75-87 ◽  
Author(s):  
Eckhard Freund ◽  
Jürgen Pesara
Keyword(s):  
Force Control ◽  
Hybrid Control ◽  
Impedance Control ◽  
Industrial Robots ◽  
New Method ◽  
Control Methods ◽  
Robotic Grinding ◽  
High Bandwidth ◽  
High Control

Common geared industrial robots call for force control methods with special properties such as good rejection of frictional disturbances, smoothness of corrective motions, and more. A new method is presented which meets these requirements and provides a high control bandwidth. In the manner of hybrid control, directions of a task frame can be selected to be force, impedance or position controlled. A joint-based inner position loop and a superimposed predictive force controller are used. Practical results include data from a robotic grinding facility. Here, the controller proved robustness and good performance under rough conditions.

Development of an Active Worktable and Its Application to Force Control of Robot Manipulators

2000 ◽  
Vol 12 (3) ◽  
pp. 249-253
Author(s):  
Shin-ichi Nakajima ◽  
Keyword(s):  
Force Control ◽  
Degrees Of Freedom ◽  
Control Method ◽  
Robot Manipulator ◽  
Impedance Control ◽  
Robot Manipulators ◽  
Compliant Motion ◽  
Stiffness Control

An active worktable, which can be applied to force control tasks of commercial robot manipulators, has been designed and built. The active worktable has several degrees of freedom and accommodates its position/force in accordance with the motion of a robot manipulator. A stiffness control method and an impedance control method are implemented in the active worktable to achieve compliant motion. Several experiments were carried out to confirm basic effectiveness of the active worktable.

Robotic Force Control Using Virtual Trajectory Generation

1999 ◽  
Vol 121 (2) ◽  
pp. 320-322
Author(s):  
Timothy S. Fielding ◽  
James K. Mills
Keyword(s):  
Force Control ◽  
Control Algorithm ◽  
Control Method ◽  
Industrial Robot ◽  
Industrial Robots ◽  
Initial Value ◽  
Control Capability ◽  
Six Degree Of Freedom ◽  
Virtual Trajectory ◽  
Contact Force Control

A control method is introduced to permit the retrofit of a large class of commercially available industrial robots with a contact force control capability. In this control algorithm, the outer force loop modifies the desired position input trajectory by solving two sets of differential equations as initial value problems. Experimental results, obtained on a CRS Robotics Corporation A460 six degree of freedom industrial robot, are presented which demonstrate the effectiveness of the proposed approach.

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