Computer Control of a treadmill and
feedback control using heart rate for rehabilitation and other
purposes
Yehia El Hgar
Supervisor: Professor Branko Cellar
Special Thanks: Dr Daoming Zhang
Aims and Motivation
Aims:
- Control of a PowerJog Treadmill using a personal computer.
- Build a GUI (Graphical User Interface) to input preset
and custom exercise protocols.
- Device a feedback system to allow control of the treadmill
in order to follow a certain heart rate profile.
Motivation:
- Exercise: for a person to be able to exercise for as
long and fast as they please.
- Human performance testing: Many exercise physiology studies
have gained valuable information from certain preset protocols
that test how a human reacts to certain exercise routines.
- Rehabilitation: In the past 30 years there has been a
movement away from the conservative approach of discouraging
heart disease patients from exercising. Strict bed rest
has been shown to have a significant detrimental effect
on physiological function. After just a few days or weeks,
the patient has significantly decreased cardiorespiratory
fitness, blood volume, RBC count, nitrogen and protein balance,
strength, flexibility and increased problems of orthosatic
hypotension and thromboembolism.
- Training: Optimal training requires that an optimal heart
rate (HR) be attained (60-80% of maximum heart rate) during
maximal exercise, and specific targets met (30-50%) during
warm-up and cool-down.
1. User Interface and features
The user interface encompasses two levels: a physical level
and a computer level. Physically the user interacts with the
system through a HR (heart rate) acquisition system* and the
PowerJog treadmill. The PowerJog treadmill features speeds
of 0-25km/h with 0.1km increments and gradients of 0-15% with
0.5% increments.
On the computer side, the programme written in Delphi, allows
the user to set custom exercise protocols, choose from preset
protocols or be able to select the special HR profiles (for
optimum performance). The system features fully customisable
options for the use of the treadmill, along with being user
friendly and giving feedback to the user about their current
status.
2. Computer interface and HR acquisition
The computer interfaces to the treadmill through a USB-to-Serial
Port(RS-323) converter. This is required due to the ever increasing
removal of serial ports from PCs and provides excellent response
time. The programme is able to interact through a variety
of commands that tell the treadmill at what speed and gradient
to adjust itself, ask for feedback, clear the screen or stop
the treadmill in its tracks.
The HR acquisition system also interfaces with a USB-to-Serial
Port converter. The system sends many types of information,
however, only the HR is important. This will be used for the
feedback system.
3. Feedback methods
The feedback (FB) methods that could be used are many and
the number of variables taken into accounts are just as many.
The FB method is used in order to keep the user’s HR
the same as the HR profile chosen. FB methods will be looking
at the error between the real HR and the proposed one, the
lag between the command to change the speed and the speed
actually changing and the lag between the speed changing and
the HR changing to a settled level.
The factors that could be taken into account include temperature,
humidity, age, weight, gender and mood. For our purposes,
however, we will use HR as a starting point.
Proposed Functioning
Summary
The Treadmill control system provides robust custom features
and excellent response time. It allows the user to choose
from a purely custom workout to preset developed workouts,
or even allows the ability to use the user’s own HR
as feedback to the system allowing maximum performance.
* HR acquisition developed by Dr Daoming
Zhang of the electrical engineering department, UNSW.
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