Cosi119a

Reading: <a href="/content/topics/homeworks/hw_readings_119/130_hw_119_realrobots/">Read Real Robots Don't Drive Straight</a>

*Reminder: Readings are your responsibility. You will be expected to come to class prepared, having read the material, and ready to participate in the discussion*

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### Logistics

* Let's do the post-it-note exercise
* Lets talk about the use of ChatGPT to produce code
  * James asked in Lab last week, why not just use the PID algorithm that is provided by ChatGPT
  * Further discussion...
* Note about due dates for all assigments. There is always a 3 day grace period.
* About the reading for today: [CLick Here](https://moodle.brandeis.edu/mod/assign/view.php?id=70275)

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### How do Robots Perceive? Sensors

* What is a sensor? Is a sensor an input or output device?
* What happens to the sensing information
* How is it stored and detected and acted upon?

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### Types of Sensors

* Is a sensor an input or output device?
* Proprioception
* Is a keyboard a sensor?
* Is a joystick a sensor?
* Is a map a sensor?
* Active Vs. Passive
* Sensor Fusion

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### What do all sensors have in common?

* They generate a stream of data
* They have an electrical connection to the computer onboard the robot
* Usually it is to the microcontroller because of real time capability
* Software on the microcontroller (e.g, arduino) is called firmware
* Firware does some processing of the data (case by case)
* Delivers it to the SBC (Single Board Computer, e.g. Rasberry Pi) in the form of topics published

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### What kinds of electrical connections?

* Very dependent on the sensor
* Analog and Binary pins
* I2C Bus
* And others
* Almost always there is an arduino library to interface

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### Lidar

* What is a Lidar
* What does it look like and how does it work?
* "Time of travel" or "Time of Flight"
* What does the data look like? 
  * [Look here fore the message definition](http://docs.ros.org/melodic/api/sensor_msgs/html/msg/LaserScan.html)
  * `roslaunch turtlebot3_gazebo turtlebot3_stage_1.launch`
  * `roslaunch turtlebot3_gazebo turtlebot3_gazebo_rviz.launch`
  * `rostopic echo --noarr -c /scan`

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### Subtleties

* What do the directions mean?
* Are the directions absolute or relative?
* What if the robot is not pointing to where you think?
* Do they go clockwise or counterclockwise?
* Lets look at the data!
* It's not clean! (This is typical for all sensors)
* It is not accurate!
* It's sometimes wildly inaccurate
* It is constantly flooding in

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### Breakout (15 Minutes)

* Documentation for [LaserScan Data](http://docs.ros.org/melodic/api/sensor_msgs/html/msg/LaserScan.html)
* Given
   1. angle_min = 0 # exactly forward
   2. angle_max = 359 (deg)
   3. range_min = 0.12 (m)
   4. range_max = 3.5 (m)
* With your teammates write a few lines of python
* Set the variable wall_ahead to true or false
* One or two lines of python
* True means that there's an obstacle ahead at < 0.3 m

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### GPS

* They vary tremendously in price
* For example: [GPS Receiver Module](https://www.robotshop.com/products/dfrobot-gravity-gnss-gps-beidou-receiver-module-i2c-uart)

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### Motor (encoder)

* How it works
* Key characteristics or features
* What data it provides

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### Camera

* How it works
* Key Characteristics or features
* What Data it provides

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### Depth Camera

* How it works
* Key Characteristics or features
* Example [ToF Camera](https://www.dfrobot.com/product-2740.html)
* What data it provides

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### Ultra Sonic Sensor

* How it works
* Key Characteristics or features
* Example: [Ultrasonic Distance Sensor](https://www.sparkfun.com/products/15569)
* What data it provides

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### Bumper sensors

* How it works
* Key Characteristics or features
* Example: [Bumper Sensopr](https://www.robotshop.com/products/bumper-sensor-robot)
* What data it provides

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### IMU - Inertial Measurement Unit

* Acceleration: dynamic and static (as in gravity)
* See [Accelerometer, Gyro, IMU buying guide](https://www.sparkfun.com/pages/accel_gyro_guide)
* Gyro: Angular velocity - how fast spinning around an acciss
* Can have them independently or combined into an IMU

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<h2 class="shadow p-3 bg-white rounded">Thank you. Questions?<img class="img-fluid w-100" src="https://picsum.photos/800/100.jpg" /> <small> (random Image from picsum.photos)</small></h2>