Moein Mehrtash

Bilateral Macro–Micro Teleoperation Using Magnetic Levitation

This paper introduces a novel magnetic-haptic micromanipulation platform with promising potential for extensive biological and biomedical applications. The platform has three basic subsystems: a magnetic untethered microrobotic system, a haptic device, and a scaled bilateral teleoperation system. A mathematical force model of the magnetic propulsion mechanism is developed, and used to design PID controllers for magnetic actuation mechanism. A gain-switching position-position teleoperation scheme is employed for this haptic application. In experimental verifications, a human operator controls the motion of the microrobot via a master manipulator for dexterous micromanipulation tasks. The operator can feel force during microdomain tasks if the microrobot encounters a stiff environment. The effect of hard contact is fed back to the operators hand in a 20 mm × 20 mm × 30 mm working envelope of the proposed platform. Conducting several experiments under different conditions, rms of position tracking errors varied from 20 to 40 μm.

Bilateral Magnetic Micromanipulation Using Off-Board Force Sensor

This paper introduces a novel haptic-enabled magnetic micromanipulation platform with promising potential for extensive biological and biomedical applications. This platform consists of two separated basic sites: 1) the slave site that uses a controlled magnetic field for manipulating a ferromagnetic microdevice and 2) the master site that uses a haptic-enabled device for the position and the force communication between the human operator and the microdevice. Due to the size restriction of the microdevice, attaching force sensors to the microdevice is impractical. Thus, to preserve a high feeling of a microdomain environment for the human operator, the applied force/torque from the environment to the microdevice is estimated with a novel off-board force sensing mechanism. This force sensing mechanism uses the produced magnetic flux information and the real position of the microdevice to estimate the environmental force applied to the microdevice. A scaled force-position teleoperation scheme is employed for this haptic application to scale down the macrodomain position for microdomain application and scale up the microdomain force for macrodomain sensing of the human operator. Conducting several experiments in different conditions, precise motion tracking with high accurate force transfer to human operator has been reported, RMS of position tracking errors of 0.2 mm with 1.27-μN accuracy force sensing for single-axis motion.

Magnetic telemanipulation device with mass uncertainty: Modeling, simulation and testing

Recently, magnetic telemanipulation devices have shown a great deal of promise in such areas as semi-conductor manufacturing, wind tunnels, drug delivery, and many more. However, these devices are generally associated with problems caused by payload variation and uncertainties in the parameters of the system which in turn, have limited the development and application of magnetic telemanipulation technology to its full capacity. This paper addresses and deals with these is sues by implementation of a precise position control method for a magnetic telemanipulation system with high level of uncertainties in its parameters. The levitation system used in this study is p rimarily designed for performing remote pick and place operations. The levitated object is a 28 gr microrobot capable of grasping and releasing payloads as heavy as 8 gr. To cope with the uncertainties in the modeling and payload variation, a model reference adaptive feedback linearization (MRAFL) controller is designed and its performance compared with an ordinary feedback linearization (FL) controller. Through experimental results it is shown that the MRAFL controller enables the microrobot to grasp and transport a payload as heavy as 30% of its own weight without a considerable effect on its positioning accuracy. In the presence of the payload, the MRAFL controller resulted in a RMS positioning error of 8 µm compared with 27.9 µm of the FL controller. The approach presented in this work is versatile as it leads to the modeling and control of a highly nonlinear system through a modular approach that can be applied to a variety of magnetic levitation and telemanipulation systems.

Modeling and Analysis of Eddy-Current Damping Effect in Horizontal Motions for a High-Precision Magnetic Navigation Platform

Recent advancements in micro/nano-domain technologies have led to a renewed interest in ultra-high resolution magnetic navigation platforms. A magnetic navigation platform (MNP) has been developed at the MagLev Microrobotics Lab of the University of Waterloo, Waterloo, ON, Canada. This platform consists of two separate basic components: a magnetic drive unit and a microrobot. The magnetic drive unit produces and regulates the magnetic field for noncontact propelling of the microrobot in an enclosed environment. The MNP is equipped with an eddy-current damper to enhance its inherent damping factor in the microrobots horizontal motions. This paper deals with the modeling and analysis of an eddy-current damper that is formed by a conductive plate placed below the levitated microrobot to overcome inherent dynamical vibrations and improve motion precision. The modeling of eddy-current distribution in the conductive plate is investigated by solving the diffusion equation for vector magnetic potential. An analytical expression for the horizontal damping force is presented and experimentally validated. It is demonstrated that eddy-current damping is a key technique to increase the damping coefficient in a noncontact way and improve levitation performance. This damping can be widely used in applications of magnetic actuation systems in micromanipulation and microfabrication.

Optimal motion control of magnetically levitated microrobot

This paper deals with the three-dimensional (3-D) manipulation of a microrobot with levitation technology. A magnetic drive unit is developed to generate the magnetic field for propelling the microrobot in an enclosed environment. The drive unit consists of electromagnets, a disc pole-piece for connecting the magnetic poles, and a soft iron yoke. To handle 3-D high precision motion control of the microrobot, experimental magnetic field measurements coupled with numerical analysis were done to identify the dynamic model of levitation. This approach leads the design of linear quadratic integral (LQI) control system, based on the derived state-space model. The 3-D motion control capability of the LQI control method is verified experimentally, and it was demonstrated that the microrobot can be operated in the levitation system workspace, vertical range of 30 mm and the horizontal range of 20 × 20 mm2, with 10 µm resolution.

Motion simulator for a multi-degree-of-freedom magnetically levitated robot

Magnetically levitated robots can move without lubrication, they generally have advantages to the use in the various special environments such as in a dust-free room, in a vacuum, in a flammable atmosphere, and in vivo. Meanwhile, they have a disadvantage of small working volume corresponding to the allowable air gap between the levitated object and the electromagnets. In some cases, to construct a combination of a magnetically levitated robot and an external manipulation device which has a comparatively large working volume seems an effective way to expand the whole working volume. On that premise, we are developing an experimental system for collaborative work between a multi-degree-of-freedom (3-DOF) magnetically levitated robot and an external manipulation device. To make full use of the range of movement of the multi-degree-of-freedom magnetically levitated robot, we are also developing an simulator system of the robot in parallel. This paper presents the derivation and the configuration of the simulator system and the results of preliminary experiments and simulations which have been performed to evaluate the effectiveness of the simulator.

Coarse and fine motion simulator between a magnetically levitated robot and an industrial robot

Magnetically levitated robots are widely employed for non-contact manipulation that presents a great promise for using in the various special environments such as in a dust-free room, in a vacuum, in a flammable atmosphere, and in vivo. Meanwhile, they have a disadvantage of small working volume corresponding to the allowable air gap between the levitated object and the electromagnets. In some cases, to construct a combination of a magnetically levitated robot (which can generate a fine motion) and an industrial robot (which can generate a coarse motion and has a comparatively large working envelope) seems an effective way to expand the whole operational working space. On that premise, we are developing an experimental system and simulator for collaborative work between a magnetically levitated robot and an industrial robot. This paper presents the system concept and the configuration of the simulator, and the result of a preliminary simulation experiment which has been performed to evaluate mainly two elements: the numerical magnetically levitated robot model and the numerical industrial robot model.

Motion simulator for coarse and fine motion of combination of a magnetically levitated micro robot and an industrial macro robot

Magnetically levitated robots can move without lubrication, they generally have advantages to the use in the various special environments such as in a dust-free room, in a vacuum, in a flammable atmosphere, and in vivo. Meanwhile, they have a disadvantage of small working volume corresponding to the allowable air gap between the levitated object and the electromagnets. In some cases, to construct a combination of a magnetically levitated robot (which can generate a fine motion) and an industrial robot (which can generate a coarse motion and has a comparatively large working volume) seems an effective way to expand the whole working volume. On that premise, we are developing an experimental system and simulator for collaborative work between a magnetically levitated robot and an industrial robot. This paper presents the system concept and the configuration of the simulator, and the result of a preliminary simulation experiment which has been performed to evaluate mainly two elements: the numerical magnetically levitated robot model and the numerical industrial robot model.

Motion Simulator for Collaborative Work Planning Between a Magnetically Levitated Robot and an Industrial Robot

Magnetically levitated robots can move without lubrication, they generally have advantages to the use in the various special environments such as in a dust-free room, in a vacuum, in a flammable atmosphere, and in vivo. Meanwhile, they have a disadvantage of small working volume corresponding to the allowable air gap between the levitated object and the electromagnets. In some cases, to construct a combination of a magnetically levitated robot and an industrial robot which has a comparatively large working volume seems an effective way to expand the whole working volume. On that premise, we are developing an experimental system and simulator for collaborative work between a magnetically levitated robot and an industrial robot. This paper presents the system concept and the configuration of the simulator which is corresponding to the actual elements: magnetically levitated robot, industrial robot and manipulation device.Copyright

Position Control of a Magnetically Levitated Robot Based on Magnetic Flux Measurement

Magnetic actuation has opened a new horizon in biological/biomedical applications. A novel magnetic actuation platform has been developed at Maglev Microrobotics Laboratory, University of Waterloo. In the previous work, laser sensors were used for positioning the levitated microrobot. This technique can be used only in transparent environment. In this paper, for applications in an enclosed environment, which may not be transparent, a novel position estimation method was proposed. The proposed method uses hall sensors, mounted on the disk pole-piece. The hall sensors’ optimal installation position has been investigated, and a function which relates hall sensors’ output and the position of robot was derived. Based on this function, position control of horizontal axis using hall sensors in place of laser sensor can be achieved. Usability of two dimensional controls in horizontal axis without laser sensors will be experimentally validated as future work of this research.Copyright