UWE Bristol Engineering showcase 2015

Ben Pearson
MEng Mechanical Engineering
Project Supervisor
Ramin Amali
Introduction
The system constructed in this project is
intended to be used to calibrate hospital urine
flow meters. The simulator will pump precise
quantities of water at constant or varying
rates. The varying rates of flow will follow a
flow pattern that is parallel to how a healthy
patient or a patient with a health issue would
urinate. The system as a result could then be
used for training purposes to help
Design and Manufacture of a Urology flow Simulator
Research
Preliminary research needed to be done before the
design stage and manufacture could commence. This
was carried out on existing pumping systems and
how they could be modified to perform the required
tasks. Although this design is unique the system is
made up of commonly used components . Therefore
it is necessary to look at how to use these
components and their compatibility they are with
each other.
The control system needed research into how the
type of controller was needed and how the controller
worked. Along side this, research was needed on
different electrical components, to enable user
interface for a user to control the prototype.
Design of the Mechanical system
The design of the Urine flow simulator
implemented fluid mechanics so as to alter the
rate at which the piston would positively displace
a liquid, creating a positive displacement pump.
A ball screw was chosen in order to reduce the
friction. As a consequence a smaller motor could
be used making it more energy efficient.
Design of the Control system
The system uses an Arduino Uno board to control
the devise. The Arduino board hold all of the
necessary information for the prototype to
become stand-alone. The Arduino then transmits
this information to the motor controller, the
solenoid valve and the LCD display, while
receiving information from the rotary encoder,
the micro switches and the LVDT
Current Systems
Currently there are no systems like this to calibrate
the flow meters, instead there are bottles that have
fixed orifices that let air in and water out. These
propose a problem creating constant flow rates.
Firstly, because the air filling the bottle as bubbles
create a pulsing effect on the flow out and secondly
preventing the flow rate from being varied.
Manufacture of the Mechanical system
The building process of the main simulator unit consisted of 3 major sections; the
bearing and gear configuration, the motor with the supporting slotted tube and
the cylinder section, including the piston. The device was designed so that all the
major components could be manufactured using a lathe or a milling machine.
The water storage tank is the next process in the constructed of the simulator.
The manufacture of the electrical system occurs alongside the mechanical
construction.
Project summary
The following research is a continuation of previous
work that designed a urology flow simulator. The
purpose of the simulator is for Southmead hospital to
calibrate and test their current urology equipment.
The system will also help with training purposes,
being able to produce a variety of flow rates that will
simulate certain conditions. This research documents
the manufacture of the system, including controlling
techniques used to program the system. Testes are
run on the simulator, and from this, future research is
required.
Project Objectives
The objectives were to produce a working prototype
of a flow simulator that could produce the following
tolerances;
Table 1: This Table Shows the System Requirements
Parameter
Guideline value
Accuracy for flow rate
Accuracy for voided volume
Range for flow rate
Range for voided volume
Minimum flow reproducible
Bandwidth of flow signals
± 0.1ml/s
± 0.2 ml
0 – 50 ml/s
0 – 500 ml
0.5 ml/s
0 to 10 Hz
Project Conclusion
A device was conceived for a urine flow simulator.
This revolved around an in depth series of
calculations in order to choose the appropriate
components including manufacturing techniques.
Preliminary testing was completed so as to obtain an
insight into how the product performed with
different flow characteristics.
Testing
The Prototype was used to produce both
constant and varying flow rates, below is the
feed back response to three constant inputs.
The results highlight an issue with using the
gearing system due to it causing hysteresis in
the output response. The output of the device
was measured from the Transducer attached to
the side of the devise which measures the
distance of the piston within the cylinder. It is
assumed that the fluid is completely
incompressible and at this early stage in testing
this is the most accurate method,
The next step will be to improve the prototype and
carry out more extensive testing. A further aim is to
further develop the control system for the assembly
to enable it to fully simulate a urology flow.