Sensorless action-reaction-based residual vibration suppression for multi-degree-of-freedom flexible systems

This paper demonstrates the feasibility of controlling motion and vibration of a class of flexible systems with inaccessible or unknown outputs through measurements taken from their actuators which are used as single platforms for measurements, whereas flexible dynamical systems are kept free from any attached sensors. Based on the action reaction law of dynamics, the well-known disturbance observer is used to determine the incident reaction forces from these dynamical systems on the interface planes with their actuators. Reaction forces are considered as feedback-like signals that can be used as alternatives to the inaccessible system outputs. The sensorless action reaction based motion and vibration control technique is implemented on a flexible system with finite modes and all results are verified experimentally

Sensorless torque/force control

Motion control systems represent a main subsystem for majority of processing systems that can be found in the industrial sector. These systems are concerned with the actuation of all devices in the manufacturing process such as machines, robots, conveyor systems and pick and place mechanisms such that they satisfy certain motion requirements, e.g., the pre specified reference trajectories are followed along with delivering the proper force or torque to the point of interest at which the process occurs. In general, the aim of force/torque control is to impose the desired force on the environment even if the environment has dynamical motion

Sensorless wave based control

Mechanical waves naturally propagate through dynamical systems that are subjected to initial excitation. These mechanical waves carry enough information about the dynamical system including its dynamics and parameters, in addition to the externally applied forces or torques due to the system's interaction with the environment. In other words, mechanical waves carry all the dynamical system's information in a coupled fashion. This thesis proposes an estimation algorithm that enables estimating flexible systems' dynamics, parameters, externally applied forces and disturbances. The proposed algorithm is implemented on a lumped system with an actuator located at one of its boundaries, that is used as a single platform for measurements where actuator's current and velocity are measured and used to estimate the reflected mechanical waves. Only these two measurements from the actuator are required to accomplish the motion and vibration control, keeping the dynamical system free from any attached sensors by considering the reflected mechanical waves as a natural feedback from the system. In this thesis the notion of position estimation is proposed including both rigid and flexible motion estimation, where the position of each lumped mass is estimated and experimentally compared with the actual measurements. This in turn implies the possibility of using these position estimates as a virtual feedback to the controllers instead of using the actual sensor's feedback. System's global behavior can be investigated by monitoring lumped system dynamics, to guarantee the accomplishment of motion control task and the minimization of system's residual vibrations. Since the dynamics of the system can be obtained, the externally applied forces or torques can be estimated. The experimental results show the validity of the proposed algorithm and the possibility of using two actuator parameters in order to estimate the uniform system parameters, rigid system's position, flexible system's lumped mass positions and external disturbances due to system's interaction with the environment

An energy based formalism for state estimation and motion control

This work presents an energy based state estimation formalism for a class of dynamical systems with inaccessible/unknown outputs and systems at which sensor utilization is costly, impractical or measurements can not be taken. The physical interactions among most of the dynamical subsystems represented mathematically in terms of Dirac structures allow power exchange through the power ports of these subsystems. Power exchange is conceptually considered as information exchange among the dynamical subsystems and further utilized to develop a natural feedback-like information from a class of dynamical systems with inaccessible/unknown outputs. The feedback-like information is utilized in realizing state observers for this class of dynamical systems. Necessary and sufficient conditions for observability are studied. In addition, estimation error asymptotic convergence stability of the proposed energy based state variable observer is proved for systems with linear and nonlinear dynamics. Robustness of the asymptotic convergence stability is analyzed over a range of parameter deviations, model uncertainties and unknown initial conditions. The proposed energy based state estimation formalism allows realization of the motion and force control from measurements taken from a single subsystem within the entire dynamical system. This in turn allows measurements to be taken from this single subsystem, whereas the rest of the dynamical system is kept free from measurements. Experiments are conducted on dynamical systems with single input and multiple inaccessible outputs in order to verify the validity of the proposed energy based state estimation and control formalism

An energy-based state observer for dynamical subsystems with inaccessible state variables

This work presents an energy-based state estimation formalism for a class of dynamical systems with inaccessible/ unknown outputs, and systems at which sensor utilization is impractical, or when measurements can not be taken. The power-conserving physical interconnections among most of the dynamical subsystems allow for power exchange through their power ports. Power exchange is conceptually considered as information exchange among the dynamical subsystems and further utilized to develop a natural feedback-like information from a class of dynamical systems with inaccessible/unknown outputs. This information is used in the design of an energybased state observer. Convergence stability of the estimation error for the proposed state observer is proved for systems with linear dynamics. Furthermore, robustness of the convergence stability is analyzed over a range of parameter deviation and model uncertainties. Experiments are conducted on a dynamical system with a single input and multiple inaccessible outputs (Fig. 1) to demonstrate the validity of the proposed energybased state estimation formalism

Motion control and vibration suppression of flexible lumped systems via sensorless LQR control

This work attempts to achieve motion control along with vibration suppression of flexible systems by developing a sensorless closed loop LQR controller. Vibration suppression is used as a performance index that has to be minimized so that motion control is achieved with zero residual vibration. An estimation algorithm is combined with the regular LQR to develop sensorless motion and vibration controller that is capable of positioning multi degrees of freedom flexible system point of interest to a pre-specified target position with zero residual vibration. The validity of the proposed controller is verified experimentally by controlling a sensorless dynamical system with finite degrees of freedom through measurements taken from its actuator

Design and control of laser micromachining workstation

The production process of miniature devices and microsystems requires the utilization of non-conventional micromachining techniques. In the past few decades laser micromachining has became micro-manufacturing technique of choice for many industrial and research applications. This paper discusses the design of motion control system for a laser micromachining workstation with particulars about automatic focusing and control of work platform used in the workstation. The automatic focusing is solved in a sliding mode optimization framework and preview controller is used to control the motion platform. Experimental results of both motion control and actual laser micromachining are presented

A novel algorithm for sensorless motion control of flexible structures

This article demonstrates the validity of using an actuator as a single platform for measurements during a motion control assignment of flexible systems kept free from any kind of measurement. System acceleration level dynamics, parameters and interaction forces with the environment are coupled in an incident reaction torque that naturally rises when a flexible system is subjected to an action imposed by an attached actuator to the system. This work attempts to decouple each of the system parameters out of the incident coupled reaction torque at the interface point of the actuator with the flexible system by way of measurements taken from the actuator, not from the system. The identified parameters, along with the estimated states, are used to achieve sensorless motion control for flexible systems

SU mikro montaj istasyonu gerçek zamanlı kontrol mimarisi

Günümüzde mikro montaj mikro elektronikten biyolojiye birçok alanda kullanılmaktadır ve kullanımı günden güne yaygınlaşmaktadır. Mikro hassasiyette çalışan sistemlerin geliştirilmesi günümüzde önemli bir yer tutmaktadır. Mikro montaj sistemlerinin önemli bir unsuru gerçek zamanlı kontrollerinin koştuğu platformlar ve bu platformlarda oluşturan algoritmalardır. Bu makale mikron ve daha küçük parçaların yüksek hassasiyetli manipülasyon ve montaj işlemlerini gerçekleştirebilmek amacıyla geliştirilen Mikro Montaj İş İstasyonunun yazılımsal ve donanımsal yapısını anlatmaktadır. Hassas hareket kontrolü için kullanılan bilgisayar mimarisinde işlemcideki çekirdeklerin nasıl kullanıldığından ve gerçek zamanlı kontrol uygulayabilmek için Linux tabanlı işletim sisteminde hangi iş parçacıklarının hangi çekirdeklere atanarak koştuğundan bahsedilmektedir