Mechanical Heart Pump

Mechanical Heart Pump

Replicating the pulsile flow of the human heart

The aim of the project was to design and build an electromechanical system to simulate the pulsatile flow of the human heart. By using various flow rate waveforms, the system is able to replicate a healthy heart as well as an unhealthy heart caused by various health conditions.

To simulate the heart, two mechanical piston pumps (one for the right ventricle and another for the left ventricle) and a piping system were designed to replicate the flow of blood to the body. This design also includes a rig to accurately position the pumps, LCD display and buttons as well as house the electrical components. Finally, two pressure vessels were designed which represent the volume of blood held in the body and lungs. These can be pressurised separately as required for the left and right ventricle pressures.

The specific design objectives set at the beginning of the project are summarised in terms of mechanical and electrical objectives. The mechanical objectives include: confirmation of current motor capability and selection of a suitable motor for the problem; the redesign of the left ventricle pump to improve performance; the design of an additional pump for right ventricle simulation including suitable stepper motor; the design of pressure vessels suitable for left and right ventricle pressure changes; and finally an improved piping system to minimise frictional forces in the system.

The electrical objectives include: selecting a suitable microcontroller platform; designing and building an electrical circuit to drive the motors; writing programs to control the motors and conduct simulations of the circuit. In order for the mechanical system to work, stepper motors were used to drive the pistons and produce the required flow rate. By controlling the rate at which the motors turn, the pumps can displace the required volume at each step interval to match the various flow rates of different heart conditions.

An external electronic circuitry was designed to power the system as well as drive the motors. To simulate different heart conditions, the speed of the motor is controlled to produce the required flow rates for each condition.

For that purpose, a microcontroller has been used and programmed to control the motor speed which can mimic the real heart operation based on specific heart conditions, taken from set parameters outlined in previous research. Those parameters are Heart Rate, Stroke Volume and Systole-Diastole Ratio which vary for each heart condition.

Moreover, an LCD display is used to display the specific parameters for each heart condition whilst push buttons can be used to select different parameters for each one. Both the buttons and display are controlled by a microcontroller.

The overall operation of the system generates different types of flow rates which can be analysed and discussed for further works and improvement.