This article presents a novel concept of the position estimator algorithm for voice coil actuators used in precision scanning applications. Here, a voice coil motor was used as an actuator and a sensor using the position estimator algorithm, which was derived from an electro-mechanical model of a voice coil motor. According to the proposed algorithm, the position of coil relative to the fixed magnet position depends on the current drawn, voltage across coil and motor constant of the voice coil motor. This eliminates the use of a sensor that is an integral part of all feedback control systems. Proposed position estimator was experimentally validated for the voice coil actuator in integration with electro-mechanical modeling of the flexural mechanism. The experimental setup consisted of the flexural mechanism, voice coil actuator, current and voltage monitoring circuitry and its interfacing with PC via a dSPACE DS1104 R&D microcontroller board. Theoretical and experimental results revealed successful implementation of the proposed novel algorithm in the feedback control system with positioning resolution of less than ±5 microns at the scanning speed of more than 5 mm/s. Further, proportional-integral-derivative (PID) control strategy was implemented along with developed algorithm to minimize the error. The position determined by the position estimator algorithm has an accuracy of 99.4% for single direction motion with the experimentally observed position at those instantaneous states.

Flexural structures are extensively beneficial when differentiated with conventional inflexible body structures where point accuracy positioning is strongly required extending in the range of microns. To fulfill clear and accurate positioning requirements, we come up with the solution of voice coil motors (VCM) with position estimator algorithm. Appropriate magnet and coil assembly is designed by considering the ultimate force for the application. Voice coil motor components are fabricated on milling machine and then assembled. This VCM is incorporated with dSPACE DS1104 R&D controller with the help of linear current amplifier (LCAM) which controls VCM with respect to desired amplitude and frequency. Displacement of coil of VCM is detected with respect to fixed magnet by using linear variable differential transformer (LVDT) which generates analog voltage signal in relation with motion of coil. Static characteristic such as stiffness is determined using force-deflection plot and dynamic characteristic like damping factor and frequency response are estimated with the help of transient response obtained by providing step input to the motor. Further, PID controller is implemented on this VCM and it is error observed is less than ±0.S microns.

Conventional mechanism (i.e. rigid link mechanisms) has limited accuracy and repeatability because of friction, backlash. Mechanism offers a relative motion between rigid links via joints. Conventionally these joints are pin, sliding, rolling, liquid film etc. These joints have inherent nonlinear frictional characteristics which are creating difficulty in control micro-nano positioning in precision mechanisms. To achieve high resolution and precision problems of friction, backlash in mechanism needs to be removed. These joints are replaced by flexible elements such as flexural hinge, flexural links which offers advantage of frictionless and smooth motion. Flexural mechanisms are developed using basic building blocks such as hinges and planar type. Flexural building blocks should be such that it offers lesser / zero resistance to motion in desired direction and maximum / infinite resistance in orthogonal direction. Motion generated in orthogonal direction is called parasitic motion. Double Flexural Manipulator (DFM) is a planar type building block which offers theoretically zero parasitic error motion with negligible amount of rotation of motion stage. This article presents design, development, system integration, system identification and PID control implementation on DFM. Developed flexural stage is integrated with desktop PC via dSPACE micro-controller. System identification (Static and Dynamic) is carried out and performance parameters such as stiffness, natural frequency, damping characteristics and frequency characterization of DFM are estimated and validated via due experimentations. Estimated transfer function of DFM is further used for development of control system, and PID control parameters are tuned. Real time PID implementation gives a position accuracy of few microns at high scanning speed of 2.5 mm/s.

Traditional mechanical systems (e.g. rigid mechanisms which use links, gears, chains, etc.) have restricted resolution and repeatability due to certain properties like friction and backlash. A mechanism is a mechanical system which provides relative displacement between rigid links by using certain joints. Commonly available joints are rolling, sliding, pin, hinges, liquid joints etc. These types of joints exhibit nonlinear frictional behaviour due to which it becomes difficult to control micro and nano positioning in high precision mechanisms. To accomplish high degree of resolution and precision, disadvantages such as backlash, friction in the mechanism needs to be eliminated. These mechanical joints are substituted by flexible components like flexural beams and hinges that provide benefits such as smooth and frictionless displacement. A single DOF flexural stage is developed by using basic building elements like flexural hinges and beams so that they offer negligible resistance to motion in targeted direction and maximum resistance in orthogonal which is also known as parasitic error. Double Flexural Mechanism (DFM) is a beam type of building element that provides analytically zero parasitic error displacement with imperceptible rotation of displacement stage. This research article presents design and development of DFM, its mechatronic integration with dSPACE DS1104 R&D Controller and its experimental validation and system identification. Static and dynamic experimentation was performed and various performance characteristics like stiffness, natural frequency and damping factor are determined experimentally. Further, a novel position estimator algorithm is designed and implemented on the mechanism that eliminates the need of high cost sensor and yields as accuracy of 25 microns at a speed of 6.4 mm/s.