Feedback Control and Exogenous Force Estimation for Improved Single-Molecule Experiments

2010 ◽  
Author(s):  
Daniel G. Cole
Keyword(s):  
Feedback Control ◽  
Single Molecule ◽  
Force Feedback ◽  
Open Loop ◽  
Optical Traps ◽  
Measured Signal ◽  
Force Estimation ◽  
Position Feedback ◽  
Integral Feedback

This article explores two types of feedback used to control optical traps: position feedback, which was shown to be equivalent to force feedback, and integral feedback. The ability of each of these types of feedback to lower the measurement SNR in single molecule experiments is evaluated and compared to the open-loop case. While position feedback did not result in any improvement in the SNR, the case of integral feedback results in an improvement. Integral feedback is shown to improve the SNR of the measured signal of interest, and is relatively robust and easy to implement. It is also shown that integral feedback acts as an exogenous force estimator.

Improving Single-Molecule Experiments With Feedback Control of Optical Traps

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
D. G. Cole
Keyword(s):  
Feedback Control ◽  
Single Molecule ◽  
Force Feedback ◽  
Open Loop ◽  
Optical Traps ◽  
Measured Signal ◽  
Experimental Conditions ◽  
Rate Feedback ◽  
Position Feedback ◽  
Integral Feedback

This article explores various types of feedback control—position feedback, which was shown to be equivalent to force feedback, rate feedback, and integral feedback—for the purpose of improving instrument performance for single-molecule experiments. The ability of each of each types of feedback to lower the measurement signal-to-noise ratio (SNR) is evaluated and compared to the open-loop case. While position feedback does not result in any improvement in the SNR, the cases of rate feedback and integral feedback both resulted in improvements in the measurement's SNR. Rate feedback is shown to effectively “cool” the beads held in the optical trap, thereby limiting the effect that Brownian disturbances have on the beads’ motion. Integral feedback is shown to improve the SNR of the measured signal of interest and is robust and easy to implement. It is also shown that integral feedback acts as an exogenous force estimator. Ultimately, feedback does not provide better resolution as measured by SNR than an open-loop filtering approach can but does provide other advantages, including the ability to control other variables and to make a more robust instrument that can be easily adapted to changes in experimental conditions or the environment.

Nonlinear Proportional Plus Integral Control of Optical Traps for Exogenous Force Estimation

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
D. G. Cole ◽  
J. G. Pickel
Keyword(s):  
Optical Trap ◽  
Open Loop ◽  
Optical Force ◽  
Optical Traps ◽  
Pi Control ◽  
Force Estimation ◽  
Nonlinear Controller ◽  
Closed Loop System ◽  
Integral Control ◽  
Servo Tracking

This article explores nonlinear proportional plus integral (PI) feedback for controlling the position of an object held in an optical trap. In general, nonlinearities in the spatial dependence of the optical force complicate feedback control for optical traps. Nonlinear PI control has been shown to provide all of the benefits of integral control: disturbance rejection, servo tracking, and force estimation. The controller also linearizes the closed-loop system. More importantly, the nonlinear controller is shown to be equivalent to an estimator of the exogenous force. The ability of nonlinear PI control to lower the measurement SNR is evaluated and compared to the variational open-loop case. A simulation demonstrating the performance of the nonlinear PI control is presented.

On Nonlinear Control of Optical Traps Using Pulling Trajectory Tracking for Single-Molecule Experiments

2011 ◽  
Author(s):  
Daniel G. Cole
Keyword(s):  
Single Molecule ◽  
Optical Trap ◽  
Static Condition ◽  
Optical Force ◽  
Optical Traps ◽  
Pi Control ◽  
Force Estimation ◽  
Integral Control ◽  
Servo Tracking ◽  
Additional Feedback

This article explores nonlinear position plus integral (PI) feedback for controlling an optical trap used in single-molecule experiments. In general, nonlinearities in the spatial dependence of the optical force complicate feedback control for optical traps. Furthermore, the extension of a molecule creates an additional feedback path that puts constraints on the PI control gains. The nonlinear PI control presented here is shown to provide all of the benefits of integral control: disturbance rejection, servo tracking, and force estimation. The ability of nonlinear PI control to lower the measurement SNR is evaluated. Finally, constraints on the pulling rate are given to ensure the system trajectory remains in a quasi-static condition, stable, and the bead remains held in the trap.

Tip Position Control of a Flexible Robot Arm Considering the Reduction Gear's Friction

1990 ◽  
Vol 2 (2) ◽  
pp. 91-96
Author(s):  
Yasuo Yoshida ◽  
◽  
Masato Tanaka
Keyword(s):  
Feedback Control ◽  
Dynamic Characteristics ◽  
Position Control ◽  
Viscous Friction ◽  
Open Loop ◽  
Robot Arm ◽  
Flexible Robot ◽  
Position Feedback ◽  
Linear Friction ◽  
Tip Position

The reduction gear's friction strongly affects the dynamic characteristics of a one-link flexible robot arm. Experiments of open loop response by motor torque were performed in two cases of large and small values of the reduction gear's friction, and compared with simulation. The reduction gear's friction has both viscous and Coulomb aspects and can be approximately treated as an equivalent viscous friction. However, tip position control was very difficult in the case of large friction with an equivalent viscous friction. Experiments indicated that tip position feedback control was possible by using a dither signal and linearizing the non-linear friction.

Bilateral Force Feedback Control for a Vehicle-Type Tele-Mobility System

2013 ◽  
Vol 133 (8) ◽  
pp. 795-803
Author(s):  
Kazuki Nagase ◽  
Shutaro Yorozu ◽  
Takahiro Kosugi ◽  
Yuki Yokokura ◽  
Seiichiro Katsura
Keyword(s):  
Feedback Control ◽  
Force Feedback ◽  
Vehicle Type ◽  
Mobility System

Open-loop adaptive feedback control of deposited zinc in hot-dip galvanizing

1993 ◽  
Vol 1 (5) ◽  
pp. 779-790 ◽  
Author(s):  
C. Fenot ◽  
F. Rolland ◽  
G. Vigneron ◽  
I.D. Landau
Keyword(s):  
Feedback Control ◽  
Open Loop ◽  
Adaptive Feedback ◽  
Adaptive Feedback Control

Design and control of 2-DoF joystick using MR-fluid rotary actuator

2021 ◽  
pp. 1045389X2110639
Author(s):  
Bao Tri Diep ◽  
Quoc Hung Nguyen ◽  
Thanh Danh Le
Keyword(s):  
Pid Controller ◽  
Force Feedback ◽  
Control Method ◽  
Open Loop ◽  
Friction Torque ◽  
Feedback Controls ◽  
Loop Control ◽  
Fuzzy Logic Algorithm ◽  
Experimental Apparatus ◽  
Close Loop Control

The purpose of this paper is to design a control algorithm for a 2-DoF rotary joystick model. Firstly, the structure of the joystick, which composes of two magneto-rheological fluid actuators (shorten MRFA) with optimal configuration coupled perpendicularly by the gimbal mechanism to generate the friction torque for each independent rotary movement, is introduced. The control strategy of the designed joystick is then suggested. Really, because of two independent rotary movements, it is necessary to design two corresponding controllers. Due to hysteresis and nonlinear dynamic characteristics of the MRFA, controllers based an accurate dynamic model are difficult to realize. Hence, to release this issue, the proposed controller (named self-turning fuzzy controllers-STFC) will be built through the fuzzy logic algorithm in which the parameters of controllers are learned and trained online by Levenberg-Marquardt training algorithm. Finally, an experimental apparatus will be constructed to assess the effectiveness of the force feedback controls. Herein, three experimental cases are performed to compare the control performance of open-loop and close-loop control method, where the former is done through relationship between the force at the knob and the current supplied to coil while the latter is realized based on the proposed controller and PID controller. The experimental results provide strongly the ability of the proposed controller, meaning that the STFC is robust and tracks well the desirable force with high accuracy compared with both the PID controller and the open-loop control method.

Passive optimal feedback control of an articulated flexible arm

2020 ◽  
pp. 107754632095676
Author(s):  
Raja Tebbikh ◽  
Hicham Tebbikh ◽  
Sihem Kechida
Keyword(s):  
Optimal Control ◽  
Feedback Control ◽  
Closed Loop ◽  
Open Loop ◽  
Optimal Feedback Control ◽  
Convolution Operators ◽  
High Frequencies ◽  
Zero Initial Condition ◽  
Flexible Arm ◽  
Euler Bernoulli Beam

This article deals with stabilization and optimal control of an articulated flexible arm by a passive approach. This approach is based on the boundary control of the Euler–Bernoulli beam by means of wave-absorbing feedback. Due to the specific propagative properties of the beam, such controls involve long-memory, non-rational convolution operators. Diffusive realizations of these operators are introduced and used for elaborating an original and efficient wave-absorbing feedback control. The globally passive nature of the closed-loop system gives it the unconditional robustness property, even with the parameters uncertainties of the system. This is not the case in active control, where the system is unstable, because the energy of high frequencies is practically uncontrollable. Our contribution comes in the achievement of optimal control by the diffusion equation. The proposed approach is original in considering a non-zero initial condition of the diffusion as an optimization variable. The optimal arm evolution, in a closed loop, is fixed in an open loop by optimizing a criterion whose variable is the initial diffusion condition. The obtained simulation results clearly illustrate the effectiveness and robustness of the optimal diffusive control.

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