Regulation with on-line gravity compensation for robots with elastic joints

2004 ◽  
Author(s):  
L. Zollo ◽  
A. De Luca ◽  
B. Siciliano
Keyword(s):  
Gravity Compensation ◽  
On Line ◽  
Elastic Joints

PD control with on-line gravity compensation for robots with elastic joints: Theory and experiments

Automatica ◽  
2005 ◽  
Vol 41 (10) ◽  
pp. 1809-1819 ◽  
Author(s):  
Alessandro De Luca ◽  
Bruno Siciliano ◽  
Loredana Zollo
Keyword(s):  
Gravity Compensation ◽  
Pd Control ◽  
On Line ◽  
Elastic Joints ◽  
Theory And Experiments

Robot Control Based on Coriolis and Centrifugal Terms Fuzzification

2001 ◽  
Author(s):  
Panos N. Politis ◽  
Vassilis C. Moulianitis ◽  
Nikos A. Aspragathos
Keyword(s):  
Fuzzy Inference System ◽  
Fuzzy Inference ◽  
Gravity Compensation ◽  
Pd Controller ◽  
Inference System ◽  
Robot Controller ◽  
On Line ◽  
Robot Configuration ◽  
Fuzzy Description ◽  
Fuzzy Pd

Abstract A new method for on-line tuning the gains of a decentralized PD controller with gravity compensation using fuzzy logic is proposed. The design of the controller is based on the fuzzy description of the robot configuration. The fuzzy inference system keeps track and takes decisions based on the robot configuration and joint velocities to adjust the derivative and proportional gains. The rules governing the controller are derived by studying the effects of the Coriolis and centrifugal terms on the robot dynamic behavior. The gravitational terms are computed using a fuzzy inference system for each joint. This FIS is trained with data taken from the simulated robot. The designed fuzzy-PD controller is compared with a centralized PD control law with gravity compensation and it is found that the fuzzy-PD controller is more robust in facing dynamic uncertainties. A two DOF robotic arm is used to demonstrate the performance of the proposed method for designing a robot controller.

scholarly journals PD control with on-line gravity compensation for robots with flexible links

2007 ◽  
Author(s):  
Loredana Zollo ◽  
Bruno Siciliano ◽  
Alessandro De Luca ◽  
Eugenio Guglielmelli
Keyword(s):  
Gravity Compensation ◽  
Pd Control ◽  
Flexible Links ◽  
On Line

An Accurate On-Line Correction Strategy for Gravity Compensation Aiming at Teaching by Touch of Collaborative Robots

2018 ◽  
Author(s):  
Yunfei Dong ◽  
Tianyu Ren ◽  
Dan Wu ◽  
Ken Chen
Keyword(s):  
Variable Stiffness ◽  
Industrial Robots ◽  
Torque Control ◽  
Joint Torque ◽  
Robot Dynamics ◽  
Gravity Compensation ◽  
End Effector ◽  
Collaborative Robots ◽  
Working Space ◽  
On Line

Modern industrial robots are increasing rapidly towards collaborating and physically interacting with people on complex tasks, and away from working in isolated cages that are separated from people. Collaborative robots are usually developed to perform variable stiffness control, teaching by touch, collision detection, and so on. Torque control with accurate gravity compensation becomes necessary. When the method of torque-based impedance force-control is used to achieve teaching by touch, the gravity compensation is added to the joint torque loop directly. As a result, the gravity model should be very accurate, otherwise the robot will not stay still even if no any artificial external force is applied. Unfortunately, it is very difficult to model and identify the robot dynamics such accurately in the whole working space because of the presence of the robot cables, joint and link flexibility, cables or tube of end-effector, the end-effector itself and so on. There are always some regions where the robot will drift due to the error of gravity compensation. This paper is motivated by the gravity compensation problem of collaborative robots equipped with joint torque sensors, and attempts to propose an accurate on-line correction strategy for gravity compensation especially aiming at the application of teaching by touch. The developed method has been tested on a 7-DOF collaborative robot and shown good performance.

The on-line use of histogram data for high-speed correction and alignment of electron microscope images

1984 ◽  
Vol 42 ◽  
pp. 556-557
Author(s):  
William Krakow
Keyword(s):  
Power Spectrum ◽  
High Speed ◽  
Direct Memory Access ◽  
Digital Television ◽  
Contrast Transfer Function ◽  
The Past ◽  
High Resolution Tem ◽  
On Line ◽  
Correction Of Astigmatism ◽  
The Fourier Transform

In the past few years on-line digital television frame store devices coupled to computers have been employed to attempt to measure the microscope parameters of defocus and astigmatism. The ultimate goal of such tasks is to fully adjust the operating parameters of the microscope and obtain an optimum image for viewing in terms of its information content. The initial approach to this problem, for high resolution TEM imaging, was to obtain the power spectrum from the Fourier transform of an image, find the contrast transfer function oscillation maxima, and subsequently correct the image. This technique requires a fast computer, a direct memory access device and even an array processor to accomplish these tasks on limited size arrays in a few seconds per image. It is not clear that the power spectrum could be used for more than defocus correction since the correction of astigmatism is a formidable problem of pattern recognition.

Image registration with a computer driven S.T.E.M.

1978 ◽  
Vol 36 (1) ◽  
pp. 98-99
Author(s):  
A.M.H. Schepman ◽  
J.A.P. van der Voort ◽  
J.E. Mellema
Keyword(s):  
Spot Size ◽  
Scanning Transmission Electron Microscope ◽  
Small Computer ◽  
Structural Studies ◽  
Area Of Interest ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Specimen Area ◽  
On Line ◽  
Minimum Distances

A Scanning Transmission Electron Microscope (STEM) was coupled to a small computer. The system (see Fig. 1) has been built using a Philips EM400, equipped with a scanning attachment and a DEC PDP11/34 computer with 34K memory. The gun (Fig. 2) consists of a continuously renewed tip of radius 0.2 to 0.4 μm of a tungsten wire heated just below its melting point by a focussed laser beam (1). On-line operation procedures were developped aiming at the reduction of the amount of radiation of the specimen area of interest, while selecting the various imaging parameters and upon registration of the information content. Whereas the theoretical limiting spot size is 0.75 nm (2), routine resolution checks showed minimum distances in the order 1.2 to 1.5 nm between corresponding intensity maxima in successive scans. This value is sufficient for structural studies of regular biological material to test the performance of STEM over high resolution CTEM.

Design and calibration of an IVEM for general 3-dimensional imaging of non-diffracting materials

1992 ◽  
Vol 50 (2) ◽  
pp. 1040-1041
Author(s):  
Neil Rowlands ◽  
Jeff Price ◽  
Michael Kersker ◽  
Seichi Suzuki ◽  
Steve Young ◽  
...  
Keyword(s):  
3D Imaging ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
3 Dimensional ◽  
3D Microstructure ◽  
Image Translation ◽  
Digital Correlation ◽  
On Line ◽  
Mechanical Stage ◽  
Projection Angle

Three-dimensional (3D) microstructure visualization on the electron microscope requires that the sample be tilted to different positions to collect a series of projections. This tilting should be performed rapidly for on-line stereo viewing and precisely for off-line tomographic reconstruction. Usually a projection series is collected using mechanical stage tilt alone. The stereo pairs must be viewed off-line and the 60 to 120 tomographic projections must be aligned with fiduciary markers or digital correlation methods. The delay in viewing stereo pairs and the alignment problems in tomographic reconstruction could be eliminated or improved by tilting the beam if such tilt could be accomplished without image translation.A microscope capable of beam tilt with simultaneous image shift to eliminate tilt-induced translation has been investigated for 3D imaging of thick (1 μm) biologic specimens. By tilting the beam above and through the specimen and bringing it back below the specimen, a brightfield image with a projection angle corresponding to the beam tilt angle can be recorded (Fig. 1a).

Software pattern recognition applied to nanodiffraction patterns from a STEM instrument

1986 ◽  
Vol 44 ◽  
pp. 694-695
Author(s):  
G.Y. Fan ◽  
J.M. Cowley
Keyword(s):  
Image Processing ◽  
Pattern Recognition ◽  
Computer Software ◽  
Processing System ◽  
Light Level ◽  
Host Computer ◽  
Low Light ◽  
Image Processing System ◽  
Recent Developments ◽  
On Line

In recent developments, the ASU HB5 has been modified so that the timing, positioning, and scanning of the finely focused electron probe can be entirely controlled by a host computer. This made the asynchronized handshake possible between the HB5 STEM and the image processing system which consists of host computer (PDP 11/34), DeAnza image processor (IP 5000) which is interfaced with a low-light level TV camera, array processor (AP 400) and various peripheral devices. This greatly facilitates the pattern recognition technique initiated by Monosmith and Cowley. Software called NANHB5 is under development which, instead of employing a set of photo-diodes to detect strong spots on a TV screen, uses various software techniques including on-line fast Fourier transform (FFT) to recognize patterns of greater complexity, taking advantage of the sophistication of our image processing system and the flexibility of computer software.

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