Robotics Sensors and Actuators Quiz

Sensors and Actuators

• Robotics use sensors to mimic human senses (vision, hearing, touch) enabling robots to interact with their environment.
• Sensor: A device measuring a world attribute, like a photoelectric cell responding to a signal or stimulus.
• Active Sensors: Input energy into the environment to alter or enhance the energy, often using an effector to position a sensor dynamically.
• Passive Sensors: Rely on the environment providing observation materials (e.g., a camera needs light).
• Transducer: Transfers energy from one system to another, often changing the form of the energy.
• Actuator: A mechanism that moves or controls something indirectly.

Types of Errors in Sensors

• Random Error: Fluctuations in the environment or sensor itself, reduced through multiple measurements and averaging.
• Systematic Error: Consistent biases in sensor or measurement system that can be corrected via calibration.
• Drift Error: Gradual shift in readings over time, despite constant external factors.
• Interference Error: Disturbances from other sources (like EMI or crosstalk).
• Nonlinearity Error: Non-linear relationship between input and output.
• Hysteresis Error: Readings affected by previous measurements, causing a delay.

Sensor Characteristics

• Resolution: Minimum measurable difference between two values.
• Sensitivity: Smallest detectable absolute change.
• Accuracy: Uncertainty in a sensor measurement compared to an absolute standard.
• Linearity: Whether the output is linearly dependent on the input.
• Precision: Reproducibility of the measurement.
• Bandwidth: Speed at which measurements are provided.
• Dynamic Range: Ratio of upper and lower sensor input limits during normal operation.

Types of Sensors

• Shaft encoders: Measure the number of turns a drive motor has made.
• Linear encoders: Measure straight-line motion.
• Accelerometers: Provide dead reckoning information, often better than odometry.
• Rotary encoders: Measure rotational movement.
• Gyroscopes: Measure orientation and angular velocity.
• Proximity sensors: Directly measure the distance between a sensor and an object.
• Ultrasonic sensors: Use acoustic energy to detect and measure distances.
• Motion sensors: Detect the presence of a moving object in the field of view.
• Hall sensors: Detect magnetic objects.
• Light sensors: Detect light, creating a voltage difference for feedback to the robot system (photoresistors, photodiodes).
• Infrared sensors (IR): Detect near-infrared energy to determine if an obstacle is present.
• Flame sensors: Detect fire or other wavelengths (760-1100 nm).
• Temperature sensors: Provide temperature feedback to controllers.
• Gas sensors: Detect various gases (LPG, Butane, Propane, Methane, etc.).
• Joystick modules: Provide X-Y movement control.
• Force sensors: Measure external mechanical forces.
• Tactile sensors: Mimic the sense of touch to measure small force variations.
• Bump sensors: Consist of two layers that touch when an object bumps into the robot.
• Digital tilt sensors: Provide tilt detection.
• Capacitive touch sensors: Detect objects with capacitive characteristics.
• Vibration sensors: Measure vibration from a spring and conductive material.
• Computer vision: Processes data from different modalities to create images.
• CMOS sensors: Arrays like memory chips enabling random pixel addressing.
• Charge-coupled devices (CCDs): Pixels transfer charges to next until read.
• Line-tracking sensors: Detect black or white lines.
• Color sensors: Measure and detect a wide range of colors.
• RGB-D sensors: Measure color and depth simultaneously.
• Sound sensors: Convert sound energy into signals like microphones.
• Voice recognition sensors: Convert human speech into signals.
• Radio-frequency identification (RFID) sensors: Provide unique identity using radio frequency signals to tags.
• Biometric sensors: Authenticate using biometric traits (iris, fingerprint, etc.).
• Laser sensors: Use laser beams for distance measurements.
• LIDAR (Light Detection and Ranging): 3D motion capture, object detection, and mapping.
• Global Positioning System (GPS): Receivers obtain location by detecting signals from orbiting satellites.

Actuators

• Actuators: Control the movement of robot parts (joints, wheels, grippers).
• Motors: Commonly used for robot joint and component control.
• Servo Motors: Controlled by electrical signals for precise position, speed, and torque control.
• DC Servo Motors: Speed proportional to voltage.
• AC Motors: Speed depends on frequency.
• Brushed motors: Have a stationary and rotating parts with magnets interacting.
• Brushless motors: No brushes, using electromagnets in the stator to control rotor movement.
• Stepper motors: Precise discrete angular movements.
• Linear motors: Provide linear motion.
• Hydraulic actuators: Operate via fluid pressure (e.g., in heavy equipment).
• Pneumatic actuators: Use compressed air for motion control.

Test your knowledge on sensors and actuators used in robotics. Explore how these devices mimic human senses and their types, including active and passive sensors. Understand the different types of errors associated with sensor measurements and their implications in robotics.