1.6. Interacting with the Real World#
For a mechatronic device to respond and interact with the real world it needs three other components:
Sensors that measure some aspect of the environment and turn it into data.
Actuators that create a physical action
Control system that reads sensor values, compares them with its goal and commands the actuators
1.6.1. Example - Washing Machine#
As an example let’s consider each of the components in a Washing Machine
Sensors
Water-level switch tells the controller when the tub is full enough.
Thermistor reports the actual water temperature.
Door sensor to make sure the door is closed.
Actuators
Solenoid valves open to let hot or cold water in.
Heating element raises the water temperature.
Motor to rotate the drum slowly for washing and spin drying.
Drain pump to empty the tub.
Door lock solenoid
Control System
A microcontroller waits for the user to select a wash program and press start. Afterwards it sends signals to each of the actuators so that the tub fills, is heated to the required temperature, drained as well as setting the drum speed via the motor. Within the stages it uses a control algorithm to make sure the desired goal is reached such as heating the water sufficiently.
