Robot Motion Flashcards
What is a holonomic robot?
moves instantaneously in any direction in space of degrees of freedom
What does differential drive mean?
2 driving wheels on left and right with own motor
What does pinion drive mean?
2 motors for drive and steer
What is wheel odometry?
calculating robot motion based on angles of motors and how much wheels have turned
How do DC motors work?
- power signal sent using PWM
- encoder measure angular position
- set amount of power to motor with voltage
How does feedback control using encoders work?
at high rate:
1. check where motor angular position actually is from
encoder
2. record error difference
3. send power demand to motor to reduce error
How does PID control work?
- send required demand to PID controller
- includes term to reduce power oscillations
What is servoing?
closed loop control: control parameters coupled directly to sensor reading and updated regularly in negative feedback loop
How do we set demand for servoing for proportional control?
set demand proportional to negative error
How does visual servoing to control steering work?
subtract offset to avoid collision with obstacle
Algorithm for sonar wall following
- use sideways sensor to measure distance z to wall
- velocity control and loop at specific frequency
- goal to maintain desired distance d
What is a likelihood function?
- describes sensor performance
- function of measurement variables and ground truth
What is temporal filtering?
- smoothing/finding median of last few measurements
- to reduce effect of outliers
What is geometric filtering/feature detection?
fit geometric shapes to sensor data which reports array of measurements
Dynamic window approach algorithm
- consider robot dynamics and possible change in motion it can make within small time dt
- for each possible motion look ahead time tao
- calculate benefit/cost based on distance from target/obstacle
- choose best and execute for time dt
- repeat
