Engineering: Robotics Engineering: Sensors and Feedback Loops Worksheet

Question 1

A robot vacuum uses a distance sensor to detect a wall. When the wall is closer than 10 centimeters, the robot turns left. Identify the sensor input, the robot output, and the goal of the system.

Accepted Answer

The sensor input is the distance to the wall. The robot output is turning left. The goal of the system is to avoid hitting the wall while moving around the room.

Question 2

A line-following robot has two light sensors facing the floor. The left sensor reads dark and the right sensor reads light. The robot is supposed to stay centered on a black line. What should the robot do next, and why?

Accepted Answer

The robot should turn slightly left because the left sensor is over the dark line while the right sensor is off the line. Turning left helps the robot move back toward the center of the line.

Question 3

Explain the difference between open-loop control and closed-loop control in a robot.

Accepted Answer

Open-loop control follows a set action without checking the result. Closed-loop control uses sensor feedback to compare what is happening to the goal and adjust the robot's actions.

Question 4

A robot arm is programmed to move to 90 degrees. An angle sensor reports that the arm is at 75 degrees. What is the error, and what should the control system do?

Accepted Answer

The error is 15 degrees because 90 minus 75 equals 15. The control system should keep moving the arm toward 90 degrees, then slow or stop when the sensor shows it has reached the target.

Question 5

Name two sensors that could help a classroom delivery robot navigate safely through a hallway. Explain what each sensor would detect.

Accepted Answer

A distance sensor could detect walls, doors, or people in front of the robot. A camera or light sensor could detect hallway signs, floor markings, or changes in brightness. Other reasonable sensors include bump sensors, gyroscopes, or wheel encoders.

Question 6

A robot uses a temperature sensor to keep a plant greenhouse at 24 degrees Celsius. If the temperature is 28 degrees Celsius, what should the robot-controlled system do? Explain how this is feedback.

Accepted Answer

The system should turn on cooling, open a vent, or reduce heating to lower the temperature. This is feedback because the system measures the current temperature, compares it with the target temperature, and changes its output to reduce the error.

Question 7

A robot's ultrasonic sensor gives noisy readings: 42 cm, 41 cm, 80 cm, 43 cm, and 42 cm. The robot is near a box. Which reading is most likely an outlier, and what could the robot do to make a better decision?

Accepted Answer

The reading of 80 cm is most likely an outlier because it is much larger than the other readings. The robot could average several readings, ignore extreme values, or take another measurement before deciding what to do.

Question 8

A wheeled robot uses wheel encoders to measure how far each wheel turns. Why might wheel encoders be useful in a feedback loop?

Accepted Answer

Wheel encoders are useful because they tell the robot how much the wheels have actually turned. The robot can compare the measured movement with the desired movement and adjust motor power if one wheel is moving too slowly or too quickly.

Question 9

A robot is trying to drive straight. Its gyroscope reports that the robot has rotated 5 degrees to the right. What correction should the robot make?

Accepted Answer

The robot should steer slightly left or reduce power to the left wheel and increase power to the right wheel, depending on its drive design. This correction helps cancel the 5 degree right turn and return the robot to a straight path.

Question 10

Read this control rule: If distance is less than 20 cm, stop. If distance is 20 cm or more, move forward. Is this a feedback loop? Explain your answer.

Accepted Answer

Yes, this can be part of a feedback loop because the robot repeatedly measures distance and changes its motor output based on that measurement. The sensor reading affects the robot's next action.

Question 11

A robot claw uses a pressure sensor. If the pressure is too low, the object slips. If the pressure is too high, the object may break. Describe a feedback strategy the robot could use to hold the object safely.

Accepted Answer

The robot could measure pressure while closing the claw and compare it to a safe target range. If pressure is too low, it can tighten slightly. If pressure is too high, it can loosen slightly. It should keep adjusting until the pressure stays in the safe range.

Question 12

A mobile robot has a camera and a distance sensor. The camera identifies a doorway, but the distance sensor shows that a chair is blocking the path. Why is it useful to combine data from more than one sensor?

Accepted Answer

Combining data from more than one sensor gives the robot a more complete picture of its environment. The camera can identify the doorway, while the distance sensor can detect the obstacle, so the robot can avoid the chair instead of driving toward the doorway blindly.

Question 13

A robot's target speed is 1.5 meters per second. Its speed sensor reads 1.2 meters per second. What is the speed error, and should the robot increase or decrease motor power?

Accepted Answer

The speed error is 0.3 meters per second because 1.5 minus 1.2 equals 0.3. The robot should increase motor power because it is moving slower than the target speed.

Question 14

The diagram shows a feedback loop with four missing labels: sensor, controller, actuator, and environment. Put the parts in the correct order for a robot that follows a line on the floor.

Accepted Answer

The correct order is environment, sensor, controller, actuator, then back to environment. The floor line is part of the environment, the light sensors measure it, the controller decides how to steer, and the motors act as actuators that change the robot's position.

Question 15

Design a simple robot system that uses at least one sensor and one feedback loop. Describe the robot's goal, the sensor input, the controller decision, and the robot output.

Accepted Answer

Answers will vary. A strong answer should include a clear goal, a sensor measurement, a decision based on comparing the measurement to the goal, and an output that changes the robot's behavior. For example, a plant-watering robot could use a soil moisture sensor, compare the reading to a target moisture level, and turn a pump on or off.

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Engineering: Robotics Engineering: Sensors and Feedback Loops

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