A variety of sensors can enhance a FIRST robotics competition robot's operation, including ultrasonic sensors, gyroscopes, accelerometers, encoders, photoelectric sensors, and joysticks. These sensors provide input to drive the robot and make autonomous decisions. Common sensors include ultrasonic detectors for measuring distance, gyroscopes and accelerometers for sensing motion, encoders for monitoring wheel rotations and gear health, and photoelectric sensors for detecting objects. Joysticks also act as sensors, providing directional control and buttons that can be programmed to control additional robot functions. Diagrams and sample code are provided to illustrate how these sensors integrate with the robot control system.

1. FIRSTFare 2010Sensors for FRC Robots Dennis C. Erickson ~ Senior Mentor for Teams 1510 and 2898 Daniel Bramblett ~ Team 1510 Amy Wiegand ~ Team 2915 1

2. Introduction A Wide Variety of Sensors can be Used to enhance the operation of the Robot Primarily used in the Offensive Mode but are also used in Defensive Operations as an Environment Monitor (e.g., Something’s Coming) 2

3. The FRC Topology 3

4. Sensors Input devices used to aid in driving the robot and to make autonomous decisions 4

6. Shaft Encoder Sensor

7. Yaw Rate Gyro Sensor

8. 3-Axis Accelerometer Sensor

9. Ultrasonic Detector Sensor

10. Gear Tooth Sensor

11. Misc Pneumatic SensorsAlso joysticks and video cameras could be considered sensors 5

12. Ultrasonic Sensor Use to determine distance to friend or foe. Good from about 8 inches to 20 feet Suggest using a software filter to smooth the data 6 Operates at 42kHz with readings every 50ms

13. Ultrasonic Sensor 7 The Block Diagram and the Front Panel Used in the Main Robot Application

14. Gyroscope Sensor Yaw Rate Gyro Senses angular changes about the top surface axis of the device and provides an output voltage proportional to the instantaneous angular rate change. The output is useful for guidance, stability, rate of closure and control of the robot platform. Inertial guidance Especially useful in designing “smart” Autonomous software 8 Best to mount flat near the robot’s center of rotation

15. Gyroscope Sensor 9 Front Panel and Diagram

16. Accelerometer Sensor Use to determine rate of closure, vibration, dynamic or static motion 10

17. Accelerometer Sensor Sample code used to read the sensor and apply bounds to the data for alarming 11

18. Gyroscope and Accelerometer Sensors 12 Knowing the instantaneous robot angle and distance traveled at that angle, the position on the field can be determined.

19. Differential Peak-Detecting Gear Tooth Sensor Hall Effect sensor used for detecting and counting magnetic fields from ferrous gear teeth related to a robot’s drive operations. For example, it can count teeth on a gear to measure and, through the RC, control robot speed. 13 Use counter VIs for analysis.

20. Encoder Sensor Use to determine rate of closure, count events (wheel rotations), monitor chain health Used in conjunction with the counter VIs Mostly located on a gear box or a motor 14

21. Encoder Sensor 15 Diagram and Front Panel Example

23. Transmissive (Beam Break) – A light beam is interrupted by an objectUse to determine the presence or absence of objects (balls, etc) 16

26. In Arcade mode, one joystick is needed

27. If switches are required, a joystick is a simple way to control belts and other robot motors, relays, solenoids, etc.17

28. The Joystick 18 Front Panel and Diagram

29. The Joystick – Using the Buttons as Input Controls 19

30. The Joystick – Using the Buttons as Input Controls 20 Front Panel and Diagram

31. Questions? Dennis C. Erickson - dcerickson1@comcast.net