Pulse Width Control for Precise Positioning of Structurally Flexible Systems Subject to Stiction and Coulomb Friction

2004 ◽  
Vol 126 (1) ◽  
pp. 131-138 ◽  
Author(s):  
David B. Rathbun ◽  
Martin C. Berg ◽  
Keith W. Buffinton
Keyword(s):  
Limit Cycle ◽  
Pulse Width ◽  
Coulomb Friction ◽  
Closed Loop ◽  
Position Control ◽  
Industrial Robot ◽  
Sufficient Conditions ◽  
Position Error ◽  
Mass System ◽  
Precise Positioning

Pulse width control refers to the use of a control law to determine the duration of fixed-height force pulses for point-to-point position control of a plant that is subject to mechanical friction, including stiction. The use of constant-gain pulse width control laws for precise positioning of structurally flexible plants subject to stiction and Coulomb friction is analyzed. It is shown that when the plant is a simple two-mass system subject to stiction and Coulomb friction, a position error limit cycle can result. Sufficient conditions for stability and self-sustained oscillation of this closed-loop system are derived. The sufficient conditions for stability are used to determine conditions on the plant parameters and the control gain that guarantee closed-loop stability and thus limit-cycle-free operation and zero steady-state position error. The analysis methods that are introduced are demonstrated in applications to the control of the position of the end-effector of an industrial robot.

Adaptive Pulse Width Control for Precise Positioning Under the Influence of Stiction and Coulomb Friction

1988 ◽  
Vol 110 (3) ◽  
pp. 221-227 ◽  
Author(s):  
Sangsik Yang ◽  
Masayoshi Tomizuka
Keyword(s):  
Pulse Width ◽  
Coulomb Friction ◽  
Sufficient Conditions ◽  
Control Object ◽  
Single Pulse ◽  
Static Friction ◽  
Adaptation Algorithm ◽  
Precise Positioning ◽  
Pulse Input ◽  
Point To Point

Conventional linear digital control fails to provide precise positioning of a control object under the influence of static friction, Coulomb friction, and backlash. This paper presents an adaptive pulse width control (PWC) scheme for a precise point-to-point positioning system. This scheme is developed based on the relationship between the displacement of a control object due to a single pulse input and the pulse width. The coefficient appearing in this relationship is estimated by a parameter adaptation algorithm. Sufficient conditions for asymptotic stability of this adaptive scheme are developed using Popov hyperstability theorem. This adaptive PWC is tested on a laboratory positioning table and is shown to be effective.

Reduction of Limit Cycle Amplitude in the Presence of Backlash

1999 ◽  
Vol 121 (2) ◽  
pp. 278-284 ◽  
Author(s):  
Ronen Boneh ◽  
Oded Yaniv
Keyword(s):  
Nonlinear Control ◽  
Limit Cycle ◽  
Closed Loop ◽  
Controller Design ◽  
Linear Time ◽  
Design Technique ◽  
Feedback Systems ◽  
Mass System ◽  
Cycle Amplitude ◽  
Limit Cycle Amplitude

The majority of feedback systems driven by an electric motor can be represented by a two-mass system connected via a flexible drive element. Owing to the presence of backlash, the closed-loop performance such as precision speed, position and force control that can be achieved using a linear time invariant controller is limited, and it is expected that a nonlinear control would be superior. In this paper a nonlinear control structure is proposed and a systematic design technique presented. The advantages of the proposed design technique are: (i) It is robust to plant and backlash uncertainty; (ii) it is quantitative to specifications on the maximum limit cycle amplitude; and (iii) the closed loop is superior to a linear controller design both in lower bandwidth and in lower limit cycle amplitude. A design example is included.

Limit Cycle Prediction Conditions for a Class of Hydraulic Control System

1986 ◽  
Vol 108 (1) ◽  
pp. 17-23 ◽  
Author(s):  
C. S. Cox ◽  
I. G. French
Keyword(s):  
Control Systems ◽  
Limit Cycle ◽  
Coulomb Friction ◽  
Position Control ◽  
Viscous Friction ◽  
Cycle Performance ◽  
Working Fluid ◽  
Hydraulic Control ◽  
Electrohydraulic System ◽  
Hydraulic Control System

This paper presents the conditions necessary to sustain a limit cycle in hydraulic position control systems with displacement feedback. The limit cycle performance of the system is then examined when the temperature of the working fluid varies between 283K(10°C) to 343K(70°C). Results are presented for an electrohydraulic system driving a load comprising inertia, viscous friction, and coulomb friction.

Pulse Width Modulation Control of Robots With Structural Flexibility

2000 ◽  
Author(s):  
David B. Rathbun ◽  
Martin C. Berg
Keyword(s):  
Pulse Width ◽  
Pulse Width Modulation ◽  
Position Control ◽  
Industrial Robot ◽  
Robot Dynamics ◽  
Structural Flexibility ◽  
Friction Behavior ◽  
Modulation Control ◽  
Point To Point ◽  
Fidelity Model

Abstract The accuracy to which the end effector of a robotic manipulator can be positioned is often limited by structural flexibilities and nonlinear friction. This paper develops a control design methodology for such systems based on pulse width modulation. This methodology achieves comparatively very accurate point-to-point position control and does not require a high fidelity model of either the robot dynamics or the friction behavior. Conditions under which the controller must directly treat plant structural flexibility are presented. Conditions on parameters of the closed loop system that guarantee stability and a well defined level of performance are given. The methodology is demonstrated by application to a six axis industrial robot.

Capacitance-Based Droplet Position Sensing Optimization Through Digital Microfluidic Parameters

2011 ◽  
Author(s):  
Miguel Angel Murran ◽  
Abbas S. Milani ◽  
Homayoun Najjaran
Keyword(s):  
Empirical Model ◽  
Closed Loop ◽  
Position Control ◽  
Microfluidic Devices ◽  
Position Error ◽  
Droplet Radius ◽  
Dielectric Thickness ◽  
Position Sensing ◽  
Electrode Pitch ◽  
Digital Microfluidic

Design of a closed-loop droplet position control is an essential step towards the development of fully automated digital microfluidic devices. However, the performance of any closed-loop controller is ultimately limited by the accuracy and precision of the feedback sensors. In this paper, an effective capacitance based droplet sensor was designed and optimized through simulation to reduce the droplet position error. A full factorial design was conducted on the droplet sensor simulation model to observe the behavior of the position error as a function of the parameters of a digital microfluidic device. An empirical model was then fitted to the data obtained from the designed simulations and optimized to reduce the position estimate error. Results suggest that the performance of the capacitance based droplet sensor studied in this work is most dependent on the dielectric thickness, droplet radius, electrode pitch, electrode separation, filler fluid permittivity, and plate gap. Isoperformance curves of the sensor performance were obtained using the empirical model to show the interaction between digital microfluidic parameters, as well as to aid in the design of digital microfluidic devices equipped with a similar capacitance based droplet sensor.

Piecewise-Linear-Gain Pulse Width Control for Precise Positioning of Structurally Flexible Systems Subject to Stiction and Coulomb Friction

2004 ◽  
Vol 126 (1) ◽  
pp. 139-143 ◽  
Author(s):  
David B. Rathbun ◽  
Martin C. Berg ◽  
Keith W. Buffinton
Keyword(s):  
Pulse Width ◽  
Position Control ◽  
Design Method ◽  
Industrial Robot ◽  
Piecewise Linear ◽  
Gain Control ◽  
Quantitative Measure ◽  
Performance Measure ◽  
Control Law ◽  
Control Laws

Pulse width control refers to the use of a control law to determine the duration of fixed-height force pulses for point-to-point position control of a plant that is subject to mechanical friction, including stiction. A quantitative measure of the performance of a pulse width control system is introduced. Applications of this measure suggest that piecewise-linear-gain pulse width control laws will often provide better performance than constant-gain pulse width control laws. A method for designing piecewise-linear-gain pulse width control laws is introduced. The performance measure and piecewise-linear-gain control law design method are demonstrated in applications to the control of the position of the end-effector of an industrial robot.

scholarly journals Research of Calibration Method for Industrial Robot Based on Error Model of Position

2021 ◽  
Vol 11 (3) ◽  
pp. 1287
Author(s):  
Tianyan Chen ◽  
Jinsong Lin ◽  
Deyu Wu ◽  
Haibin Wu
Keyword(s):  
Coordinate System ◽  
Industrial Robot ◽  
Calibration Method ◽  
Error Model ◽  
Position Error ◽  
Industrial Robots ◽  
Positioning Error ◽  
Robot Position ◽  
General Measurement ◽  
Parameter Error

Based on the current situation of high precision and comparatively low APA (absolute positioning accuracy) in industrial robots, a calibration method to enhance the APA of industrial robots is proposed. In view of the "hidden" characteristics of the RBCS (robot base coordinate system) and the FCS (flange coordinate system) in the measurement process, a comparatively general measurement and calibration method of the RBCS and the FCS is proposed, and the source of the robot terminal position error is classified into three aspects: positioning error of industrial RBCS, kinematics parameter error of manipulator, and positioning error of industrial robot end FCS. The robot position error model is established, and the relation equation of the robot end position error and the industrial robot model parameter error is deduced. By solving the equation, the parameter error identification and the supplementary results are obtained, and the method of compensating the error by using the robot joint angle is realized. The Leica laser tracker is used to verify the calibration method on ABB IRB120 industrial robot. The experimental results show that the calibration method can effectively enhance the APA of the robot.

Sign in / Sign up

Export Citation Format

Share Document