Design a Control System for a Treadmill
What is the treadmill
A treadmill is an exercise machine for running or walking while staying in one place. The word treadmill traditionally refers to a type of mill which was operated by a person or animal treading steps of a wheel to grind grain (see treadwheel.)
The machine provides a moving platform with a wide conveyor belt and an electric motor or a flywheel. The belt moves to the rear allowing a person to walk or run an equal, and necessarily opposite, velocity. The rate at which the belt moves is the rate of walking or running. Thus, the speed of running may be controlled and measured. The more expensive, heavy-duty versions are motor-driven. The simpler, lighter, and less expensive versions passively resist the motion, moving only when the walker pushes the belt with their feet.
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Figure 1: Treadmill Mechanical Frame
objective and Importance
The main objective of this project is to design a hardware and software control system for a motorized machine handling with variable conveyed loads by using a programmable PID controller, in addition of some controlling features like tuning the controller and reading many measurements from digital and analog sensors for closed - loop control System.
Since we can control this machine, we can control many similar industrial machines with conveyors, also we can observe the response of tuned controller, which is very important for variable speed motorized machines.
System Map
As we see in the figure below, the two microcontrollers transmitting asynchronous data between each other to control the two motors and to give output information to the user through LCD display while receiving the feedback measurements and instructions from system sensors and user keypad. User’s safety is the first priority of the system controller, so the usual decision of the controllers is stop system motors and writing a user-warning message when the I.R sensor gives safety distance exceeding indication.
Figure 2: System Map
Project features
- Closed - loop speed control of conveyor motor.
- Closed - loop position control of the incline motor.
- Programmable PID controller with ability of tuning from the machine control panel.
- LCD display.
- Measuring heart rate and user weight.
- calculate the burned calories per min.
- Shock absorber.
- Wireless safety switch.
My Contribution
- Team leader and coordinator.
- System mathematical modeling.
- Control panel and driver motors microcontrollers programmer.
- Control panel designer.
- Control panel PCB design and implementation.
- Controller designer.
system response
the figures below shows the closed - loop system response for a step input before and after adding the designed PID controller.F
Figure 3: Closed - Loop System Step Response Before Adding The Designed PID Controller
Figure 4: Closed - Loop System Step Response After Adding The Designed PID Controller
Control panel real parts implementation
Project test
This is the first test of the project in design phase, we used breadboards to implement the circuits instead of PCB at first for modifiying purposes.
