Sensors and Control Applications 7 Rivers Robotics Coalition December, 2015 D. Foye

FIRST Robotics Challenges The robot must be functionally flexible- able to implement different strategies and adapt to the playing field environment Team members must provide most of the decision making and strategy- which cannot be pre-determined Some functions needed on the playing field can be pre-determined, and in fact must be- it is not practical to force all intelligent responses onto the operators/team So- what can the robot do autonomously???

Typical benefits of autonomous functions Consider a pre-designed, programmed function: When an identical sequence of operations must be performed multiple times- When a simple function must be performed quickly- more quickly than a human operator When a relatively simple function, aided by robot local sensors, must be effective, reliable, and result in good performance

Why sensors? Sensors allow us to implement “intelligent” robot autonomous functions Sensors provide information about the environment to the robot software we create BUT- CAREFULL ! Sensors don’t always operate and react the way we expect Sensors can be challenging to include in the robot and work the way we want them to

Reasons many teams do not use sensors Do not have them Do not understand what they do Have not seen successful applications Programming is complex

What do we use sensors for? In general, sensors are used to provide a measurement, which is then used to make a decision (in software) Sensors can also provide a measurement, which can then be used in continuous control

What can we do? Decide where the sensor will operate best Test ideas early by: Acting out the software sequence and watching for problems Running monitoring software for the sensor to: Try it and be sure it is working! Operate during operating walk-through to see if sensor is detecting what we want Try it when other sensor disturbances are present To use sensors well, you must understand and “be” the robot !

Internal Sensors vs. External Sensors Internal Time Wheel rotations Direction External Distance Barrier (touch) Sight- light, image, color

Two forms of Control Demonstrated Bang-Bang Robot program causes action to correct when target is exceeded Proportional Robot program causes proportional correction to error

Performance is related to the Error amount and strength of response Bang-Bang Too much correction can cause loss of control; I.E. -response outside of the control range Proportional Too much correction can cause loss of control; I.E. instability and rapid cycling, while too little may not be effective in maintaining control within the control range

Demonstrations- monitor

Demonstrations- Two sensors vs. One

Design Sequence Try the sensor, learn how it works and responds Operate the sensor in the application, add a monitoring function to watch for good or undesired responses Fine tune for the desired performance

Is it working well? Wow! You got your control system to work once ! Are you done? You can: Try it several times to see if success will repeat Change environment (within reason) to see when and if your design will fail Observe carefully for signs or hints of failure