Showing posts with label Friction Compensation. Show all posts
Showing posts with label Friction Compensation. Show all posts
Monday, March 23, 2009
Model and Friction Compensation
1. Model and Friction Compensation
2. Actuators Friction Compensation
3 Friction Compensation algorithms 1
4. Friction Compensation in position and speed control
5. Friction Modelling near Striebeck Velocities
Tuesday, March 17, 2009
Friction Compensation in position and speed control
Comparison of different control strategies and friction
Compensation algorithms in position and speed control
Abstract
Friction is present in almost every motion control application
and affect the quality of the position, velocity or force control.
This influence defends on the control strategy itself and on
the compensation algorithms that can be added to improve
the control further. This paper reports the experience of our
laboratory in this field
The mechanical system , bloc diagram, state transition diagram
more ( pdf )
Two Adaptive Friction Compensation for DC Servomotors
Abstract
Two advanced control strategies of adaptive friction compensation
For DC servomotor are presented in this paper, the first is used for
The direct on-line friction compensation in the velocity control system,
The second is making use of an adaptive inverse neural network controller
In the position control system. Both are composed of an adaptive
Compensator for the nonlinear stiction and Coulomp friction in
Parallel with a PID regulator. Experiments show that much improvement
Of performance has attained respect to conventional controller
more ( pdf )
Identification and Model-based Compensation
of Striebeck Friction1
Abstract:
The paper deals with the measurement, identification and
compensation of low velocity friction in positioning systems.
The introduced algorithms are based on a linearized friction model,
which can easily be introduced in tracking control algorithms.
The developed friction measurement and compensation methods
can be implemented in simple industrial controller architectures,
such as microcontrollers. Experimental measurements are provided
to show the performances of the proposed control algorithm.
Compensation algorithms in position and speed control
Abstract
Friction is present in almost every motion control application
and affect the quality of the position, velocity or force control.
This influence defends on the control strategy itself and on
the compensation algorithms that can be added to improve
the control further. This paper reports the experience of our
laboratory in this field
The mechanical system , bloc diagram, state transition diagram
more ( pdf )
Two Adaptive Friction Compensation for DC Servomotors
Abstract
Two advanced control strategies of adaptive friction compensation
For DC servomotor are presented in this paper, the first is used for
The direct on-line friction compensation in the velocity control system,
The second is making use of an adaptive inverse neural network controller
In the position control system. Both are composed of an adaptive
Compensator for the nonlinear stiction and Coulomp friction in
Parallel with a PID regulator. Experiments show that much improvement
Of performance has attained respect to conventional controller
more ( pdf )
Identification and Model-based Compensation
of Striebeck Friction1
Abstract:
The paper deals with the measurement, identification and
compensation of low velocity friction in positioning systems.
The introduced algorithms are based on a linearized friction model,
which can easily be introduced in tracking control algorithms.
The developed friction measurement and compensation methods
can be implemented in simple industrial controller architectures,
such as microcontrollers. Experimental measurements are provided
to show the performances of the proposed control algorithm.
Monday, March 16, 2009
Friction Compensation algorithms 1
On Methods for Low Velocity Friction Compensation
Theory and Experimental Study
Abstract
A study of different classes of controllers for mechanisms
under the influence of low velocity friction is conducted.
Many methods are proposed in the literature for friction
compensation, but there has been no significant analysis
of these methods with respect to each other. Also lacking
in the literature is some form of categorization, under which
it is possible to describe and study their performance.
This paper provides an experimental and analytic study of
controllers previously proposed for low velocity friction
compensation. Since each controller will be evaluated on
the same experimental platform, the results can be quantified
to provide an approach by which to evaluate the performance
of the controllers relative to each other. Some simulations will
also be performed to show the effect of certain system
parameters on the performance of these controllers.
1 Introduction
2 System Description
3 Linear Methods
3.1 PD schemes
3.2 PID Control
4 Nonlinear Methods
4.1 Smooth Continuous Nonlinear Compensation
4.2 Discontinuous Compensation
5 Experimental Results
5.1 Experimental Setup
5.2 Results and Discussion
6 Conclusions
more
Adaptive Compensation of Friction Forces with Differential Filter
Kouichi Mitsunaga, Takami Matsuo
Abstract:
In this paper, we design an adaptive controller to
compensate the nonlinear friction model when the output is the
position. First, we present an adaptive differential filter to estimate
the velocity. Secondly, the dynamic friction force is compensated
by a fuzzy adaptive controller with position measurements. Finally,
a simulation result for the proposed controller is demonstrated.
Keywords: nonlinear friction, adaptive controller, fuzzy basis
function expansion, adaptive differential filter.
Introduction
Friction is one of the greatest obstacles in high precision positioning
systems. Since it can cause steady state and tracking errors, its
influence on the response of the systems must be considered
seriously ([10]). Many friction models have been proposed that differ
on the friction effects that are modeled in a lubricated contact.
These models are divided into two categories: the kinetic and dynamic
Friction models. The kinetic friction models take into account the
friction effects such as the viscous friction, the
Coulomb friction, and the Stribeck effect. Another category of friction
model includes dynamic friction model that embody the natural
mechanism of friction generation such as the LuGre model
Adaptive differential filter
Nonlinear friction model
Controller design
more
New Results in NPID Control: Tracking,
Integral Control, Friction Compensation
and Experimental Results
Brian Armstrong†, David Neevel, Todd Kusik
Abstract
Nonlinear (NPID) control is implemented by varying the controller
gains as a function of system state. NPID control has been previously
described and implemented, and recently a constructive Lyapunov
stability proof has been given. Here, NPID control analysis and design
methods are extended to tracking, and to systems with state feedback
and integral control. Experimental results are presented showing
improved tracking accuracy and friction compensation by NPID control.
Here we are interested in NPID control applied to linear systems with
the objective of improved performance. Past and recent studies have
shown that for linear systems NPID control can provide:
1. Increased damping,
2. Reduced rise time for step or rapid inputs,
3. Improved tracking accuracy, and
4. Friction Compensation.
2 NPID control in state space
2.1 System model
Theorem 1. Asymptotic stability of NPID regulator control for
state space systems
2.2 Design of NPID control
3 Tracking NPID control
Theorem 2. Bounded Input – Bounded Output stability of
NPID tracking control.
4 Augmented state vector: integral control
5 Friction compensation
Proposition 3. Friction compensation by NPID control.
6 Experimental results
more
Actuators Friction Compensation
Friction Compensation of Harmonic Drive Actuators
J.-P. Hauschilda, G. R. Hepplerb and J. J. McPheeb
Abstract
Friction models and methods of friction compensation as
applied to harmonic drive servo-actuators are investigated.
In the absence of output torque measurements and
output shaft encoder data nearly complete friction compensation
is achieved. Simulation and experimental results showing
the application of the friction compensation are given.
J.-P. Hauschilda, G. R. Hepplerb and J. J. McPheeb
Abstract
Friction models and methods of friction compensation as
applied to harmonic drive servo-actuators are investigated.
In the absence of output torque measurements and
output shaft encoder data nearly complete friction compensation
is achieved. Simulation and experimental results showing
the application of the friction compensation are given.
Friction compensation
The methods of friction compensation to be discussed here
are restricted to those that are applicable to HD actuators
without output torque measurements or encoders
mounted on the output shaft. The simplest way to compensate
friction in servo drives is a feed-forward element as shown
in Figure 1 (with the feed-back part removed). A friction
torque f () is added to the input torque as an offset to
the input signal for the motor depending on the sign of the
input. In the ideal case, this offset should be exactly the friction
torque but in practice the offset should always under compensate
the real friction to avoid instabilities. Feed-forward compensation
is limited to the reduction of the Coulomb friction. It cannot
compensate stiction effects nor viscous friction, does not
provide back drivability to the motor, would not prevent large
steady state errors and it would increase the non-linearities
of the motor[4]. Compensation based on Coulomb friction
based models has an infinite slope for a zero input which can
cause an undesirable chattering when the friction compensation
is used in a direct feedback loop. A remedy would be
a decreased slope at zero input[5], but the steady-state error
of the system can still increase due to the under compensation
of the friction at low velocities. An extension of the feed-forward
friction compensation is shown in Figure 1 where there is now
an additional feed-back element which provides a compensation
for viscous friction and can include the Stribeck effect.
A compensation of the stiction
The methods of friction compensation to be discussed here
are restricted to those that are applicable to HD actuators
without output torque measurements or encoders
mounted on the output shaft. The simplest way to compensate
friction in servo drives is a feed-forward element as shown
in Figure 1 (with the feed-back part removed). A friction
torque f () is added to the input torque as an offset to
the input signal for the motor depending on the sign of the
input. In the ideal case, this offset should be exactly the friction
torque but in practice the offset should always under compensate
the real friction to avoid instabilities. Feed-forward compensation
is limited to the reduction of the Coulomb friction. It cannot
compensate stiction effects nor viscous friction, does not
provide back drivability to the motor, would not prevent large
steady state errors and it would increase the non-linearities
of the motor[4]. Compensation based on Coulomb friction
based models has an infinite slope for a zero input which can
cause an undesirable chattering when the friction compensation
is used in a direct feedback loop. A remedy would be
a decreased slope at zero input[5], but the steady-state error
of the system can still increase due to the under compensation
of the friction at low velocities. An extension of the feed-forward
friction compensation is shown in Figure 1 where there is now
an additional feed-back element which provides a compensation
for viscous friction and can include the Stribeck effect.
A compensation of the stiction
force is theoretically possible, but in practice not applicable
because an infinite slope of both compensators for zero velocity
would cause chattering. Reducing this slope would result in a zero
velocity reading and therefore prevent any feed-back
compensation. This type of friction compensation introduces
an increased non-linearity as in the pure feed-forward case.
more
SUBMICROMETER FRICTION COMPENSATION USING
VARIABLE-GAIN SLIDING MODE CONTROL
Paul I. Ro
ABSTRACT
The paper discusses a sliding mode control suitable
for compensation of nonlinear microdynamic friction
and parameter changes in a ball-screw driven slide
system. The conventional, fixed-gain sliding mode
control has a limited range of performance in the
presence of varying nonlinear friction in submicrometer
trajectory tracking. In this work, an
algorithm that effectively calculates variable
switching gain based on the observation of parameter
variation and friction disturbance is proposed. To
verify the effectiveness of the proposed algorithm, the
comparison with the conventional slide mode control
is presented and experimentally verified. It is shown,
from the result of this work, that a variable switching
gain was critically important in compensating for
varying nonlinear friction in the sub-micrometer
motion range for ball-screw driven systems.
because an infinite slope of both compensators for zero velocity
would cause chattering. Reducing this slope would result in a zero
velocity reading and therefore prevent any feed-back
compensation. This type of friction compensation introduces
an increased non-linearity as in the pure feed-forward case.
more
SUBMICROMETER FRICTION COMPENSATION USING
VARIABLE-GAIN SLIDING MODE CONTROL
Paul I. Ro
ABSTRACT
The paper discusses a sliding mode control suitable
for compensation of nonlinear microdynamic friction
and parameter changes in a ball-screw driven slide
system. The conventional, fixed-gain sliding mode
control has a limited range of performance in the
presence of varying nonlinear friction in submicrometer
trajectory tracking. In this work, an
algorithm that effectively calculates variable
switching gain based on the observation of parameter
variation and friction disturbance is proposed. To
verify the effectiveness of the proposed algorithm, the
comparison with the conventional slide mode control
is presented and experimentally verified. It is shown,
from the result of this work, that a variable switching
gain was critically important in compensating for
varying nonlinear friction in the sub-micrometer
motion range for ball-screw driven systems.
A simple conceptual model for the system was
developed in Figure 1 that shows the idealized model
of the mechanical components of the system. In the
current system setup, as seen in Figure 1, the slide
position, 2 x , is the only state measured by a laser
interferometer. The slide velocity, 2 x& , is gathered
digitally by first order difference of 2 x . The nut
position and its velocity, 1 x and 1 x& , are not
measurable. The built-in tachometer can be used for
measuring the angular velocity of the ball-screw but
the signal output is very noisy. The tachometer
signal is usually good for motor speeds orders of
magnitude greater than that used in submicrometer
motion. The ball-screw rotation and its angular
velocity, and & , are thus estimated. The
unmeasurable state variables, x1 and 1 x& , are estimated
by a Kalman filter (Ro, Shim and Jeong, in press).
more
developed in Figure 1 that shows the idealized model
of the mechanical components of the system. In the
current system setup, as seen in Figure 1, the slide
position, 2 x , is the only state measured by a laser
interferometer. The slide velocity, 2 x& , is gathered
digitally by first order difference of 2 x . The nut
position and its velocity, 1 x and 1 x& , are not
measurable. The built-in tachometer can be used for
measuring the angular velocity of the ball-screw but
the signal output is very noisy. The tachometer
signal is usually good for motor speeds orders of
magnitude greater than that used in submicrometer
motion. The ball-screw rotation and its angular
velocity, and & , are thus estimated. The
unmeasurable state variables, x1 and 1 x& , are estimated
by a Kalman filter (Ro, Shim and Jeong, in press).
more
Model and Friction Compensation
Friction Models and Friction Compensation
H. Olsson† K.J. Åström† C. Canudas de Wit‡
M. Gäfvert† P. Lischinsky††
Introduction
Friction occurs in all mechanical systems,e.g. bearings,
transmissions, hydraulic and pneumatic cylinders, valves, brakes
and wheels. Friction appears at the physical interface between
two surfaces in contact. Lubricants such as grease or oil are often
used but the there may also be a dry contact between the
surfaces. Friction is strongly influenced by contaminations. There
is a wide range of physical phenomena that cause friction, this
includes elastic and plastic deformations, fluid mechanics and
wave phenomena, and material sciences
Friction phenomena
Static models
Dynamic models
Comparison of the Bliman-Sorine and the LuGre
Models
Control Systems Applications
Friction Compensation
There are many ways to compensate for friction. A very simple
way to eliminate some effects of friction is to use a dither signal,
that is a high frequency signal that is added to the control signal.
An interesting form of this was used in gyroscopes for auto pilots
in the 1940s. There the dither signal was obtained simply by
a mechanical vibrator, see J41K. The effect of the dither is that it
introduces extra forces that makes the system move before the
stiction level is reached. The effect is thus similar to removing
the stiction. A modern version is the Knocker, introduced in J32K,
for use in industrial valves. The effects of dither in systems with
dynamic friction HLuGreI was recently studied in J43K.
more
Model Based Friction Compensation in a DC Motor
Tegoeh Tjahjowidodo, Farid Al-Bender, Hendrik Van Brussel
1 Introduction
Friction modeling and identification is a prerequisite for
the accurate control of electromechanical systems. In the
literature, identification of friction in a motor system
usually considers only classical friction models, such as
Coulomb and Viscous friction. Presliding motion, which is
apparent in many friction investigations, is usually
neglected. The presliding regime is taken into account in
some advanced models, such as LuGre model and the most
recent Generalized Maxwell-Slip (GMS) model.
Unfortunatelly, LuGre does not accommodate the unique
behavior of presliding faithfully. The GMS model manages
to overcome those difficulties by modeling friction as a
Maxwell-Slip model where the slip elements satisfy a
certain, new state equations [1,2].
Once the friction models have been optimized, position
control incorporating friction compensation is performed
[1,3]. For this purpose, the inertial force and friction
behavior are compensated for using a feedforward control,
while a simple (PID) feedback part is included to track setpoint
changes and to suppress unmeasured disturbances.
2 Modeling and Results
more
H. Olsson† K.J. Åström† C. Canudas de Wit‡
M. Gäfvert† P. Lischinsky††
Introduction
Friction occurs in all mechanical systems,e.g. bearings,
transmissions, hydraulic and pneumatic cylinders, valves, brakes
and wheels. Friction appears at the physical interface between
two surfaces in contact. Lubricants such as grease or oil are often
used but the there may also be a dry contact between the
surfaces. Friction is strongly influenced by contaminations. There
is a wide range of physical phenomena that cause friction, this
includes elastic and plastic deformations, fluid mechanics and
wave phenomena, and material sciences
Friction phenomena
Static models
Dynamic models
Comparison of the Bliman-Sorine and the LuGre
Models
Control Systems Applications
Friction Compensation
There are many ways to compensate for friction. A very simple
way to eliminate some effects of friction is to use a dither signal,
that is a high frequency signal that is added to the control signal.
An interesting form of this was used in gyroscopes for auto pilots
in the 1940s. There the dither signal was obtained simply by
a mechanical vibrator, see J41K. The effect of the dither is that it
introduces extra forces that makes the system move before the
stiction level is reached. The effect is thus similar to removing
the stiction. A modern version is the Knocker, introduced in J32K,
for use in industrial valves. The effects of dither in systems with
dynamic friction HLuGreI was recently studied in J43K.
Friction Models and Friction Compensation
Karl J. Åström
Slide Content
1. Introduction
2. Friction Models
3. The LuGre Model
4. Effects of Friction on Control Systems
5. Friction Compensation
6. Summary
Friction Models and Friction Compensation
1. Introduction
2. Friction Models
3. The LuGre Model
4. Effects of Friction on Control Systems
5. Friction Compensation
6. Summary
Static Models
Karl J. Åström
Slide Content
1. Introduction
2. Friction Models
3. The LuGre Model
4. Effects of Friction on Control Systems
5. Friction Compensation
6. Summary
Friction Models and Friction Compensation
1. Introduction
2. Friction Models
3. The LuGre Model
4. Effects of Friction on Control Systems
5. Friction Compensation
6. Summary
Static Models
more
Model Based Friction Compensation in a DC Motor
Tegoeh Tjahjowidodo, Farid Al-Bender, Hendrik Van Brussel
1 Introduction
Friction modeling and identification is a prerequisite for
the accurate control of electromechanical systems. In the
literature, identification of friction in a motor system
usually considers only classical friction models, such as
Coulomb and Viscous friction. Presliding motion, which is
apparent in many friction investigations, is usually
neglected. The presliding regime is taken into account in
some advanced models, such as LuGre model and the most
recent Generalized Maxwell-Slip (GMS) model.
Unfortunatelly, LuGre does not accommodate the unique
behavior of presliding faithfully. The GMS model manages
to overcome those difficulties by modeling friction as a
Maxwell-Slip model where the slip elements satisfy a
certain, new state equations [1,2].
Once the friction models have been optimized, position
control incorporating friction compensation is performed
[1,3]. For this purpose, the inertial force and friction
behavior are compensated for using a feedforward control,
while a simple (PID) feedback part is included to track setpoint
changes and to suppress unmeasured disturbances.
2 Modeling and Results
more
Subscribe to:
Posts (Atom)
