HALBACH ARRAY LINEAR MOTOR ACTUATOR FOR THE TOTAL ARTIFICIAL HEART A. E. ElGebaly, M. El-Nemr and M. ElKhazendar Faculty of Engineering, Tanta University, EGYPT Ladies and Gentlemen, It is my honor to introduce the paper ………………………….prepared by eng…….dr……….prof.dr………….

Analysis of total artificial heart drive Simulated study Today’s Agenda Introduction Analysis of total artificial heart drive Simulated study Results and discussion Conclusion Now, it is today’s agenda first we present an introduction about why total artificial heart second analysis of total artificial heart drive third simulation study forth results and discussion finally conclusion

The need of total artificial heart Cont. Introduction Worldwide, 3,500 heart transplants performed every year. About 800,000 people have a Class IV heart defect and need a new organ. Due to a severe shortage in donor hearts, more and more patients die while waiting for heart transplantation. In order to offer an alternative to those patients, total artificial hearts (TAH) are being developed. Three thousand five hundred…………………………Eight hundred thousand .

Natural Heart and Total Artificial Heart Cont. Introduction The TAH is completely contained inside the chest. A battery powers this TAH. Energy from the external charger reaches the internal battery through an transcutaneous energy transmission, or TET. The controller controls the pumping speed of the heart according body requirments. Now this slide illustrates how TAH installed in the body instead of defective heart

Requirements of TAH designs Cont. Introduction All designs for TAH should fulfill basic requirements to be suitable for human body. These requirements are - simple design - small size - small weight - small losses - high sufficient force to pump blood

Disadvantages of previous TAH designs Cont. Introduction Previous drive concepts, based on rotary brushless DC motor have some problems associated with the conversion gear mechanism such as - less reliability - more voluminous. There are some

Advantages of linear motor for TAH Cont. Introduction Linear motor actuator doesn’t require a system to convert the motion. So, more reliability and less design complication will be obtained. Reliability is strengthen by using a linear motor actuator has the advantage of no wear-prone components. But, using linear motor will provide the following advantages

Advantages of Halbach array linear motor actuator Cont. Introduction Halbach array concept is used to develop a TAH linear motor actuator because of its advantages of having: no wear-prone power connection of the coils, where static coil and moving permanent magnets are used no back iron no cogging force. Now we will illustrate the Advantages of Halbach array linear motor actuator

Prototype of TAH Halbach array linear motor Cont. Analysis Due to previous advantages for Halbach array linear motor actuator, we analyze this motor to obtain its performance. This figure illustrates a prototype for this drive Analog to the natural heart, TAH comprise two blood chambers. To pump the blood into the aorta/pulmonary artery, these blood chambers are compressed by pusher plates. Additional specifications can also be added such as one directional valve in the beginning and end of two chambers The magnets are aligned in a special manner known as Halbach array. Through this alignment, the magnetic flux density is augmented on the outer side, while it is partially cancelled on the inner side of the magnets

Construction Cont. Analysis NdFeB52 permanent magnet is used in this model because it has good characteristics, coercivity of 891300 A/m and residual flux density of 1.48 T, for obtaining high magnetic field for small model. Coils are arranged from left to right as coil 1 to coil 5. Each coil of the five coils has 1500 turns of copper 30 AWG.

Dimensions Cont. Analysis The linear motor actuator has the following dimensions 66mm outer diameter, 16mm inner diameter, and a width of 45mm and 63mm for full expansion. It has a weight of 1kg approximately near to the weight of the first AbioCor to be surgically implanted in a patient on July 3, 2001 where the AbioCor is made of titanium and plastic with a weight of 2pounds. The year two thousand and one

3. Simulated study Cont. Simulation Finite-element calculation with the package FEMM is used to analyze the model. The analysis of this magnetostatic problem depends on the following equation. (1) Where, (μ) is permeability, A is the magnetic vector potential and J is the current density. Now we introduce the magnetostatic equations which FEMM package solves to obtain required force from model

Magnetic flux density is calculated as follows: Cont. Simulation Magnetic flux density is calculated as follows: (2) So, produced force can be calculated using Lorenz force equation to be: (3)

Magnetic flux density is calculated as follows: Cont. Simulation Magnetic flux density is calculated as follows: (2) So, produced force can be calculated using Lorenz force equation to be: (3) 12

The sequence of current flow during full heart beat Cont. Simulation This slide illustrates The sequence of current flow during full heart beat. Only those coils, penetrated by high radial flux, are powered. Direction of force is determined by coils current direction Current sequence for negative force Current sequence for positive force

Magnetic flux density distribution 4. Results Cont. Results Magnetic flux density distribution Through magnets alignment, the magnetic flux density is augmented on the outer side, while it is partially cancelled on the inner side of the magnets. Only those coils, penetrated by high radial flux, are powered

Required force over displacement for heart operation Cont. Results Heart pumps blood in the aorta and pulmonary artery according to the illustrated force. Where, dashed line represents high force on aorta where high pressure and solid line represents low force on the pulmonary artery

Produced force compared with required force Cont. Results Proposed actuator can produce approximately the same required force of the natural heart

Current in coil 1 at each displacement Cont. Results Now we illustrates the current in each coil to make the motor produce required force. First coil one at positions 0 and 18 mm the current reaches maximum values the current reaches zero at 9mm where flux pass through it in x direction dashed line represents current for positive and dashed for negative force

Current in coil 2 at each displacement Cont. Results the current reaches zero at 0, 18mm where flux pass through coil 2 in x direction .dashed line represents current for positive and dashed for negative force

Current in coil 3 at each displacement Cont. Results As coil one but with negative sign where the fluxes on coil 1 and 3 are in opposite direction

Current in coil 4 at each displacement Cont. Results As coil 2 but with negative sign where the fluxes on coil 2 and 5 are in opposite direction

Current in coil 5 at each displacement Cont. Results The current in coil 5 reaches zero in position from 9:18 mm where the coil isn’t cut by considerable flux

Total motor losses at each displacement Cont. Results Figure illustrates the losses at each position. The losses doesn’t exceed 20 watt. Because 20 watt is acceptable loss for TAH actuator

Conclusion Required force for total artificial heart can be obtained by small Halbach array linear motor. The required force was obtained with less volume actuator and frees wear-prone motor working with less loss. All dimensions is determined and tested with FEMM package to obtained required performance. The losses are much lower than the permissible losses from TAH which is approximately equal 20watt. Fewer losses enable to obtain flexible range of larger forces, if required, without suffering from losses limitation. Future work will study the dynamics of model during making full heart beat. After obtaining dynamic model, the design of control system can be done to integrate with the actuator system for obtaining robust system.

Thank You ???