Compliance error compensation of a robot end-effector with joint stiffness uncertainties for milling: An analytical model

2022 ◽  
Vol 170 ◽  
pp. 104717
Author(s):  
Vu Linh Nguyen ◽  
Chin-Hsing Kuo ◽  
Po Ting Lin
Keyword(s):  
Analytical Model ◽  
Error Compensation ◽  
Joint Stiffness ◽  
End Effector

scholarly journals Rotation-joint stiffness modeling for industrial robots considering contacts

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879306 ◽  
Author(s):  
Zhifeng Liu ◽  
Jingjing Xu ◽  
Qiang Cheng ◽  
Yongsheng Zhao ◽  
Yanhu Pei
Keyword(s):  
Fractal Theory ◽  
Joint Stiffness ◽  
Industrial Robots ◽  
Torsional Stiffness ◽  
Equivalent Stiffness ◽  
Force Analysis ◽  
Joint System ◽  
End Effector ◽  
Stiffness Modeling ◽  
High Speeds

Joint flexibility has a major impact on the motion accuracy of a robotic end effector, particularly at high speeds. This work proposes a technique of precisely modeling the torsional stiffness of the rotational joints for the industrial robots. This technique considers the contacts that exist in the joint system, which can have a significant effect on the overall joint stiffness. The torsional stiffness of the connections that commonly exist in the rotational joints, such as the belt connection, the connections using key, bolts, and pins, were modeled by combining the force analysis and the fractal theory. Through modeling the equivalent stiffness for the springs in serial and in parallel, the torsional stiffness of all joints for the ER3A-C60 robot were calculated and analyzed. The results show that the estimated stiffness based on the proposed technique is closer to the actual values than that based on the previous model without considering the contacts. The analysis is useful for controlling the dynamic characteristic of the industrial robots with the rotational joints while planning the trajectory for the end effector.

High-temperature effect on the mechanical performance of screwed CFRPI–TC4 alloy joints repaired with metal inserts

2019 ◽  
Vol 54 (17) ◽  
pp. 2245-2260
Author(s):  
Yun-Tao Zhu ◽  
Jun-Jiang Xiong
Keyword(s):  
High Temperature ◽  
Carbon Fiber ◽  
Temperature Effect ◽  
Analytical Model ◽  
Joint Strength ◽  
Mechanical Performance ◽  
Joint Stiffness ◽  
Repair Efficiency ◽  
Strength And Stiffness ◽  
High Temperature Effect

This paper seeks to study high-temperature effect on mechanical performance of screwed single-lap carbon fiber-reinforced polyimide–TC4 titanium alloy joints repaired with metal inserts. Quasi-static tension tests were conducted at room temperature (RT) and 250℃ to determine the joint strength and stiffness of repaired joints with metal inserts. Based on the experimental results, high-temperature effect on joint strength and stiffness and insert repair efficiency were analyzed and discussed. A new analytical model was established to evaluate the effect of high temperature on joint stiffness. It is concluded that (1) joint strength and stiffness for all configurations are lower at 250℃ than that at RT, showing the expected detrimental effect of high temperature on joint strength and stiffness. The reductions in joint strength and stiffness depend on the joint configuration; (2) the repair efficiencies of embedded conical nut for joint strengths of protruding and countersunk head screw joints decrease, but those for joint stiffness increase at 250℃ as against at RT. Unlike the repair efficiencies of embedded conical nut, the repair efficiency of bushing for joint strength is slightly greater, but that for joint stiffness is less at 250℃ than at RT; and (3) the developed analytical model is capable of predicting the displacement of screwed single-lap carbon fiber-reinforced polyimide–TC4 joints at RT and high temperature, and there is good agreement between the experimental data and the predicted curves.

Planar Manipulator with Mechanically Adjustable Joint Compliance

2012 ◽  
Vol 6 (1) ◽  
pp. 46-52 ◽  
Author(s):  
Hiroaki Seki ◽  
◽  
Yoshitsugu Kamiya ◽  
Masatoshi Hikizu
Keyword(s):  
Hollow Cylinder ◽  
Degrees Of Freedom ◽  
Joint Stiffness ◽  
Plane Motion ◽  
Leaf Spring ◽  
End Effector ◽  
Joint Compliance ◽  
Arbitrary Position ◽  
Joint Mechanism ◽  
Adjustable Compliance

A novel robot joint with mechanically adjustable compliance is presented. It utilizes a leaf spring and the joint compliance can be adjusted by rotating this spring, i.e., changing its bending direction. A joint actuatormoves an armlink via a connection that consists of a hollow cylinder and a leaf spring. This mechanism is compact to be installed in a joint and it can change the joint stiffness rapidly and stably. A planar manipulator using this joint mechanism is proposed for the contact or constraint tasks. Since four joints are necessary to obtain arbitrary stiffnesses and an arbitrary position of the end-effector in plane motion, a four DOF (degrees of freedom) manipulator with mechanically adjustable joint compliance is developed.

Virtual fixtures with autonomous error compensation for human–robot cooperative tasks

Robotica ◽  
2009 ◽  
Vol 28 (2) ◽  
pp. 267-277 ◽  
Author(s):  
Raúl A. Castillo-Cruces ◽  
Jürgen Wahrburg
Keyword(s):  
Control Strategy ◽  
Error Compensation ◽  
Robotic System ◽  
Cooperative System ◽  
Complete Control ◽  
End Effector ◽  
Surgical Interventions ◽  
Virtual Fixtures ◽  
Cooperative Tasks

SUMMARYThis paper presents a control strategy for surgical interventions, applied on a human–robot cooperative system, which facilitates the sharing of responsibilities between surgeon and robot. The controller utilizes virtual fixtures to constrain the movements of the end-effector into a predefined path or region. Possible deviation error can be compensated in two different ways: (a) manual compensation and (b) autonomous compensation. With manual compensation, the system defines both virtual fixtures and error compensation directions, but the surgeon must apply manual forces himself/herself in order to generate end-effector motion. With autonomous compensation, a clear distribution of responsibilities between surgeon and robotic system is present, meaning the surgeon has complete control of the end-effector along the preferred directions, while the robot autonomously compensates for any deviation along the non-preferred directions.

scholarly journals Estimation and Adjustment of Polarization Errors in Conical Scan Method

2018 ◽  
pp. 47-54
Author(s):  
A. A. Bludov ◽  
G. A. Gorbatovskij ◽  
V. S. Pavlov ◽  
A. F. Suvorov
Keyword(s):  
Signal Processing ◽  
Analytical Model ◽  
Error Compensation ◽  
Computational Procedure ◽  
Direction Finding ◽  
Processing Level ◽  
Quantitative Estimates ◽  
Conical Scan ◽  
Algorithmic Technique ◽  
Finding Method

The article proposes a solution of a problem of polarization error compensation for radar object direction finding by means of conical scan method. The solution is considered at signal processing level that makes possible to avoid polarization limitations in antennas engineering. The purpose of the article is to substantiate a model for polarization-induced errors by conical scan direction finding method and to develop an algorithmic technique for the considered method correction with regard to arbitrary polarization conditions of radar interaction. The results are presented by analytical model along with quantitative estimates of polarization-induced errors of direction finding and the computational procedure of the error compensation as well as by analysis of imperfectness factors for the proposed procedure exposing its practical applicability.

scholarly journals Joint stiffness identification of industrial serial robots

Robotica ◽  
2011 ◽  
Vol 30 (4) ◽  
pp. 649-659 ◽  
Author(s):  
Claire Dumas ◽  
Stéphane Caro ◽  
Mehdi Cherif ◽  
Sébastien Garnier ◽  
Benoît Furet
Keyword(s):  
Measurement Errors ◽  
Joint Stiffness ◽  
Experimental Tests ◽  
End Effector ◽  
Identification Method ◽  
Serial Robots ◽  
Stiffness Identification ◽  
Actuated Joints

SUMMARYThis paper presents a new methodology for the joint stiffness identification of industrial serial robots and as consequence for the evaluation of both translational and rotational displacements of the robot's end-effector subject to an external wrench (force and torque). In this paper, the robot's links are supposed to be quite stiffer than the actuated joints as it is usually the case with industrial serial robots. The robustness of the identification method and the sensitivity of the results to measurement errors, and the number of experimental tests are also analyzed. The Kuka KR240-2 robot is used as an illustrative example throughout the paper.

scholarly journals Visual end-effector position error compensation for planetary robotics

2007 ◽  
Vol 24 (5) ◽  
pp. 399-420 ◽  
Author(s):  
Max Bajracharya ◽  
Matthew DiCicco ◽  
Paul Backes ◽  
Kevin Nickels
Keyword(s):  
Error Compensation ◽  
Position Error ◽  
End Effector ◽  
Planetary Robotics

Comparing model-based control methods for simultaneous stiffness and position control of inflatable soft robots

2020 ◽  
pp. 027836492091196
Author(s):  
Charles M. Best ◽  
Levi Rupert ◽  
Marc D. Killpack
Keyword(s):  
Dynamic Models ◽  
Position Control ◽  
Sliding Mode ◽  
Joint Stiffness ◽  
Variable Stiffness ◽  
Soft Robots ◽  
End Effector ◽  
Simultaneous Control ◽  
Stiffness Model ◽  
Stiffness Control

Inflatable robots are naturally lightweight and compliant, which may make them well suited for operating in unstructured environments or in close proximity to people. The inflatable joints used in this article consist of a strong fabric exterior that constrains two opposing compliant air bladders that generate torque (unlike McKibben actuators where pressure changes cause translation). This antagonistic structure allows the simultaneous control of position and stiffness. However, dynamic models of soft robots that allow variable stiffness control have not been well developed. In this work, a model that includes stiffness as a state variable is developed and validated. Using the stiffness model, a sliding mode controller and model predictive controller are developed to control stiffness and position simultaneously. For sliding mode control (SMC), the joint stiffness was controlled to within 0.07 Nm/rad of a 45 Nm/rad command. For model predictive control (MPC) the joint stiffness was controlled to within 0.045 Nm/rad of the same stiffness command. Both SMC and MPC were able to control to within 0.5° of a desired position at steady state. Stiffness control was extended to a multiple-degree-of-freedom soft robot using MPC. Controlling stiffness of a 4-DOF arm reduced the end-effector deflection by approximately 50% (from 17.9 to 12.2cm) with a 4 lb (1.8 kg) step input applied at the end effector when higher joint stiffness (40 Nm/rad) was used compared with low stiffness (30 Nm/rad). This work shows that the derived stiffness model can enable effective position and stiffness control.

Accuracy calibration of a 3-CRU translational parallel robot based on the subset of error measurements

2020 ◽  
pp. 095440622096769
Author(s):  
Tie Zhang ◽  
Guangcai Ma ◽  
Yachao Cao ◽  
Yingwu He
Keyword(s):  
Linear Combination ◽  
Error Compensation ◽  
Calibration Method ◽  
Parallel Robot ◽  
Laser Tracker ◽  
End Effector ◽  
Structural Error ◽  
Robot Accuracy ◽  
Calibration Methods ◽  
Complete Set

Robot accuracy calibration is an effective method to improve its kinematic accuracy. However, most of the existing calibration methods need to measure the complete set of 6-dimensional pose errors of the end-effector, which makes the calibration process especially complicated. In this paper, an accuracy calibration method for a 3-CRU translational parallel robot is proposed based on the subset of error measurements. The process is implemented by four steps: 1) the error model is established based on matrix method. Then the structural errors to be identified are separated. 2) part of pose errors of the end-effector are measured by laser tracker and used to form the subset of error measurements. 3) the minimum structural error linear combination affecting robot accuracy is determined according to the minimum parameter error linear combination theorem. After that, the structural errors can be identified based on the subset of error measurements. 4) error compensation based on the identification results. This method can not only ensure the identifiability of the structural errors, but also can realize error identification based on the subset of error measurements, which will significantly reduce the calibration workload and improve the calibration efficiency. Experiments are carried out to prove the effectiveness of the calibration method.

Active Joint Stiffness Regulation to Achieve Isotropic Compliance in the Euclidean Space

2012 ◽  
Vol 4 (4) ◽  
Author(s):  
Nicola P. Belfiore ◽  
Matteo Verotti ◽  
Paolo Di Giamberardino ◽  
Imre J. Rudas
Keyword(s):  
Euclidean Space ◽  
Joint Stiffness ◽  
Classical Problem ◽  
Euclidean Group ◽  
End Effector ◽  
Closed Form Solutions ◽  
In Series ◽  
Static Conditions ◽  
The Relationship ◽  
Force Displacement

This paper is dedicated to the relationship between the external force applied on a point of a robot end-effector and its consequent displacement in static conditions. Both the force and the displacement are herein considered in the Euclidean space E(3). This fact represents a significant simplification of the approach, since it avoids some problems related to the absence of a natural positive definite metric on the Special Euclidean Group SE(3). On the other hand, such restriction allows the method to find closed-form solutions to a large class of problems in robot statics. The peculiar goal of this investigation consists of setting up a procedure which guarantees at least one pose at which any force applied (in E(3)) to an end-effector point is always parallel to its consequent displacement (also in E(3)). This property, which will be referred to as isotropic compliance in E(3), makes the robot tip static behavior uniform with respect to all directions, namely, isotropic, although not homogeneous, since it holds only in some poses. Achieving isotropic compliance in E(3) is a task more general than the classical problem of finding a pose with unit condition number, which does not include the case of different elements in the diagonal joint stiffness matrix. For this reason, the object of the present investigation could not be furtherer simplified to the classical kinetostatic problem in terms of the jacobian matrix alone. The paper reveals how the force–displacement parallelism can be achieved by using a method based on a simple proportional-derivative (PD) controller strategy. The method can be applied when the passive and active stiffness act, on the joints, either in parallel or in series, and the magnitude of the displacement response can be chosen by imposing appropriate values for the overall joints compliance. Results show that for the three analyzed examples, namely, the RR, RRP, and RRR manipulators, with arbitrary lengths of the links, there is, at least, one pose for which the sought property is achieved.

Sign in / Sign up

Export Citation Format

Share Document