Mir Behrad Khamesee

Design and control of a microrobotic system using magnetic levitation

Presents a prototype microrobot based on magnetic principles. Miniature items are to be transported and assembled in hazardous environments. A microrobot can be remotely operated with 3 DOF in an enclosed environment by transferring magnetic energy and optical signals from outside. The magnetic drive unit consists of 8 electromagnets (4 pairs), 2 permanent magnets, a return yoke and a pole piece. The microrobot is manipulated under the pole piece by regulating magnetic field. It consists of a magnetic head, a body (electronic circuit and batteries), and copper alloy ribbon ringers. A shape memory alloy actuator activates the fingers by illuminating/extinguishing several LED. PID controls were applied. To cope with uncertainties and variations in payload masses, an adaptive control law was also employed for positioning along the z axis to enable the controller parameters to be adjusted in real-time. Effectiveness of the control was verified by the results of several experiments. The microrobot has a net mass of 8.1 g and it can elevate and manipulate objects with masses up to 1.5 g within a volume of 29/spl times/29/spl times/26 mm/sup 3/ with a precision of 0.05 mm.

Design and Implementation of a Micromanipulation System Using a Magnetically Levitated MEMS Robot

Magnetic levitation of microrobots is presented as a new technology for micromanipulation tasks. The microrobots were fabricated based on microelectromechanical systems technology and weigh less than 1 g. The robots can be positioned in 3-D using magnetic field. It is shown that microrobots can be produced using commercially available magnets or electrodeposited magnetic films. A photothermal microgripper is integrated to the microrobots to perform micromanipulation operations. The microgrippers can be actuated remotely by laser focusing that makes the microrobot free of any wiring. This leads to increased motion range with more functionality in addition to dust-free motion and ability to work in closed environments. The 3-D motion capability of the microrobots is verified experimentally and it was demonstrated that the microgrippers can be operated in a vertical range of 4 mm and a horizontal range of 4 mm times 5 mm. Micromanipulation experiments such as pick-and-place, pushing, and pulling were demonstrated using objects with 100 mum and 1 mm diameter.

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.

Eddy current damper feasibility in automobile suspension: modeling, simulation and testing

This paper presents the modeling, simulation and testing of a novel eddy current damper (ECD) to be used in vehicle suspension systems. The conceived ECD utilizes permanent magnets (PMs), separated by iron poles that are screwed to an iron rod, and a conductive hollow cylinder to generate damping. Eddy currents develop in the conductor due to its relative motion with respect to the magnets. Since the eddy currents produce a repulsive force that is proportional to the velocity of the conductor, the moving magnet and conductor behave as a viscous damper. The structure of the new passive ECD is straightforward and does not require an external power supply or any other electronic devices. An accurate, analytical model of the system is obtained by applying electromagnetic theory to estimate the electromagnetic forces induced in the system. To optimize the design, simulations are conducted and the design parameters are evaluated. After a prototype ECD is fabricated, experiments are carried out to verify the accuracy of the theoretical model. The heat transfer analysis is established to ensure that the damper does not overheat, and the demagnetization effect is studied to confirm the ECD reliability. The eddy current model has 1.4?N RMS error in the damping force estimation, and a damping coefficient as high as 53?N?s?m?1 is achievable with the fabricated, scaled-down prototype. Finally, a full-size ECD is designed and its predicted performance is compared with that of commercial dampers, proving the applicability of the ECD in vehicle suspension systems.

A prototype mechanism for three-dimensional levitated movement of a small magnet

This paper deals with basic technologies for noncontact manipulation of small objects using magnets in micromachine applications. A small permanent magnet is manipulated by controlling the magnetic field applied to it. We propose a prototype mechanism to control the magnetic field for 3D levitated movement of an object. The prototype consists of eight electromagnets, pole-pieces to connect the magnetic poles, a soft iron yoke, and permanent magnets embedded in the yoke to compensate for the gravitational force of an object (a small permanent magnet). Regulation of a magnetic field and, as a result, motion of the object are strongly related to the geometric design of the pole-piece. A strategy for the pole-piece design is proposed and tested experimentally. Motion of the object in the vertical direction is realized by controlling the sum of the electromagnet currents for regulation of magnetic field gradient. Motion in the horizontal plane is realized by controlling the ratio of each electromagnet current for regulating the location of the maximum magnetic field. Results of several experiments show that the proposed prototype is effective.

Eddy current damping for magnetic levitation: downscaling from macro- to micro-levitation

Magnetic levitation of miniaturized objects is investigated in this paper. A magnetic levitation setup is built to implement one-dimensional magnetic levitation motion. It was observed that as the levitated object becomes smaller, magnetic levitation suffers more from undesired vibrations. As a solution, eddy current damping is offered and implemented successfully by placing conductive plates close to the levitated object. An analytical expression for damping coefficient is derived. Experimentally, it is shown that eddy current damping can reduce the RMS positioning error to the level of more than one third of its original value for a 0.386 g object levitated in an air-gap region of 290 mm. The proposed system has the potential to be used for micro-manipulation purposes in a high motion range of 39.8 mm.

A hybrid electromagnetic shock absorber for active vehicle suspension systems

The use of electromagnetic dampers (ED) in vehicle active suspension systems has drawn considerable attention in the past few years, attributed to the fact that active suspension systems have shown superior performance in improving ride comfort and road handling of terrain vehicles, compared with their passive and semi-active counterparts. Although demonstrating superb performance, active suspensions still have some shortcomings that must be overcome. They have high energy consumption, weight, and cost and are not fail-safe in case of a power breakdown. The novel hybrid ED, which is proposed in this paper, is a potential solution to the above-mentioned drawbacks of conventional active suspension systems. The proposed hybrid ED is designed to inherit the high-performance characteristics of an active ED with the reliability of a passive damper in a single package. The eddy current damping effect is utilised as a source of the passive damping. First, a prototype ED is designed and fabricated. The prototype ED is then utilised to experimentally establish the design requirements for a real-size active ED. This is accomplished by comparing its vibration isolation performance in a 1-DOF quarter-car test rig with that of a same-class semi-active damper. Then, after a real-size active ED is designed, the concept of hybrid damper is introduced to the damper design to address the drawbacks of the active ED. Finally, the finite-element method is used to accurately model and analyse the designed hybrid damper. It is demonstrated that by introducing the eddy current damping effect to the active part, a passive damping of approximately 1570 Ns/m is achieved. This amount of passive damping guarantees that the damper is fail-safe and reduces the power consumption more than 70%, compared with an active ED in an automotive active suspension system.

A novel eddy current damper: theory and experiment

A novel eddy current damper is developed and its damping characteristics are studied analytically and experimentally. The proposed eddy current damper consists of a conductor as an outer tube, and an array of axially magnetized ring-shaped permanent magnets separated by iron pole pieces as a mover. The relative movement of the magnets and the conductor causes the conductor to undergo motional eddy currents. Since the eddy currents produce a repulsive force that is proportional to the velocity of the conductor, the moving magnet and the conductor behave as a viscous damper. The eddy current generation causes the vibration to dissipate through the Joule heating generated in the conductor part.An accurate, analytical model of the system is obtained by applying electromagnetic theory to estimate the damping properties of the proposed eddy current damper. A prototype eddy current damper is fabricated, and experiments are carried out to verify the accuracy of the theoretical model. The experimental test bed consists of a one-degree-of-freedom vibration isolation system and is used for the frequency and transient time response analysis of the system. The eddy current damper model has a 0.1 m s−2 (4.8%) RMS error in the estimation of the mass acceleration. A damping coefficient as high as 53 Ns m−1 is achievable with the fabricated prototype.This novel eddy current damper is an oil-free, inexpensive damper that is applicable in various vibration isolation systems such as precision machinery, micro-mechanical suspension systems and structure vibration isolation.

Motion control of a large gap magnetic suspension system for microrobotic manipulation

Magnetic suspension systems have shown a great deal of promise in the field of microrobotics. This paper discusses the performance of a new large gap magnetic suspension system developed by the researchers. The magnetic drive unit consists of six electromagnets attached to a soft iron pole piece and yoke. Levitation of an 11.19 g microrobot prototype is demonstrated for step, ramp and periodic input trajectories using PID control. The working envelope of the microrobot is 30 × 22 × 20 mm3, with an RMS error on the order of 18 µm in the vertical direction and 8 µm in the horizontal direction. It is demonstrated that the levitated microrobot is able to track the desired trajectory precisely and that the system has potential application for micromanipulation.

The design of an intelligent mechanical Active Prosthetic Knee

With the cost of active prostheses continuing to rise, war amputees, specifically in developing war-torn countries are unable to partake in the advancement of intelligent limbs. Many of the commercial prosthetic knee joints available are either wholly passive or provide only partial active feedback and control. The purpose of the proposed Active Prosthetic Knee (APK) design is to investigate a new schema that allows the device to provide the full necessary torque at the knee joint. Utilizing gait trend detection and streaming it to an intelligent logic, allows autonomous movement that mimics human locomotion. This study involves the design methodology of both the mechanical aspects as well as the fuzzy-based control system. The logic behind the fuzzy system can replicate the human gait cycle by dividing the cycle into its own unique phases.