Lect 8 Flashcards
What are DC motors?
They are available in all types and sizes
The control is achieved by voltages or PWM
For precision encoders and feedback is used.
Generally DC motors have high speed and low torques, so the use of gears are almost always necessary.
Why do we need reduction of gears?
When we reducde the gearsi we achieve low speed and higher torques.
What is an open loop?
An open loop is a control loop for motors. It has u(input) voltage or pwm command
P (X) x: internal states
y: output as a function of x.
In open loops, we don’t have a measure or a control of the output. For example: Clothes drier
What is a closed loop? Why we need closed loops?
We need a closed loop motor control because, if we want our robot to go to a position, without controlling the output, it wont be a good choice. Therefore we need control over the output. And it can be achieved by adding a controller C. The output is feed back to the system and an error is produced as the difference between the reference and the output of the system.
What is a PID controller?
It is a motor control loop.
P: proportional gain (KP) : reduces the error
I: Integral gain(ki) removes the steady state error
D: Differential gain(Kd): how fast the error is removed (if the error is removed too fast than the differential gain is too slow)
What is a reference filtering?
In addition to the feedback, we also add a feedforward,which helps inserting additional knowledge.
It reduces the work of feedback controller.
What is the robot speed when the wheels turn?
It is very hard for the robot to understand the interaction of the wheels and the environment.
Non ideal elements: -friction , - softness of the wheels
In order to understand how much the robot moved, we need to make calibration.
If you want to figure how much your robot moves, you spin the wheels and you apply calibration. EMPIRICAL CALIBRATION
What is position based path planning?
If my robot has a localization, and knows where it is relative to a fixed coordinate frame, then it can move in a precise way along a sequence of predefined waypoints.
