Analog vs Digital Digital on/off voltage Analog variable voltage
Environment Robot What do we want to know? Position Velocity Color Position Velocity Topography Temperature Size/shape Acceleration Orientation
Sensors Sonar Accelerometer Gyroscope Encoder Camera Potentiometer Compass Laser
Potentiometers Variable resistance Voltage divider Linear or rotary
Accelerometer and Gyroscope Measure deflection of micro-mass Variation in output voltage V α a and V α ω Resolution V/gcounts/V=> counts/g V/°/scounts/V => counts/°
Analog to Digital Computers sample analog signals Voltage of sample corresponds to digital number
Using Accel/Gyro Info Sampling Period = ΔT Angular Velocity x Time => Angle Change Acceleration x Time => Velocity Change Velocity x Time => Position Change
Sonar sound navigation and ranging Point Source Emitter and receiver Calculate distance Reflected Signal Calculate distance to an object
Sonar Shortfalls Object interference Radial Distance How can we overcome it? - Rotating sensors - Multiple sensors
Sonar with Multiple Sensors Sensor Interference Solutions: - Different frequency sensors - Double-Pulse Coding
Controlling Sonar Sonar board configuration Give command/pulse signal Start counter Receive response – stop counter Calculate distance
Mapping with Sonar Distance represents a 3D surface ○ 2D if you make good assumptions Digital representation (map) Shaded cells MAY contain an object
Rotary Encoders Diode light passes through slits in disk Photocell gives high voltage
Encoders with Direction 2 Channels with slight offset A or B will be read first
Absolute Encoder Standard Binary Encoding Contact 1Contact 2Contact 3Angle 1offoffoff0° to 45° 2offoffon45° to 90° 3offonoff90° to 135° 4offonon135° to 180° 5onoffoff180° to 225° 6onoffon225° to 270° 7ononoff270° to 315° 8ononon315° to 360°
Compass Direction relative to defined direction Analog output
Bringing it Together Many sensors interfacing with microcontroller