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Robotics Engineering: Sense, Think, Act
Sensors, Processors, Motors, and Feedback
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Robots are engineered systems that interact with the world by following a basic cycle: sense, think, and act. They use sensors to gather information, computers to interpret that information, and actuators to produce movement or other outputs. This cycle is the foundation of everything from factory arms to self-driving vehicles and medical robots. Understanding it helps students see how mechanical, electrical, and computer engineering work together in one machine.
In a robot, sensing begins with devices like cameras, distance sensors, force sensors, and encoders that convert physical conditions into signals. The thinking stage uses algorithms, control logic, and feedback to estimate the robot's state, compare it to a goal, and choose the next command. The acting stage turns electrical energy into motion through motors, gears, wheels, grippers, or joints. When feedback from sensors is continuously returned to the controller, the robot can correct errors and operate more accurately in changing environments.
Key Facts
- Robotics follows a repeating loop: Sense -> Think -> Act -> Sense.
- Sensors convert physical quantities such as light, distance, force, or position into electrical signals.
- A controller often computes error as e = target - measured value.
- In proportional control, command = Kp * e.
- Mechanical power delivered by an actuator can be estimated with P = Fv or P = tau * omega.
- Feedback improves accuracy because the robot measures results and adjusts its actions.
Vocabulary
- Sensor
- A sensor is a device that detects a physical quantity and converts it into a usable signal for the robot.
- Controller
- A controller is the hardware or software system that processes sensor data and decides what the robot should do next.
- Actuator
- An actuator is a component such as a motor or hydraulic device that creates motion or force.
- Feedback
- Feedback is information about the robot's actual output that is sent back to the controller for correction.
- Encoder
- An encoder is a sensor that measures rotation or position, often used to track motor shaft movement.
Common Mistakes to Avoid
- Confusing sensors with actuators, which is wrong because sensors measure conditions while actuators produce motion or force. A camera senses, but a motor acts.
- Assuming the robot thinks only once before moving, which is wrong because most robots run the sense-think-act loop continuously. Repeated updates are needed to respond to changes and reduce error.
- Ignoring feedback in control problems, which is wrong because open-loop commands cannot correct for disturbances or slippage. Always check whether measured output is used to adjust the next action.
- Treating all sensor data as perfectly accurate, which is wrong because real sensors have noise, delay, and limited resolution. Good robot design accounts for uncertainty when making decisions.
Practice Questions
- 1 A robot is programmed to move 5.0 m forward, but its sensors report it has moved only 4.2 m. Using e = target - measured value, what is the position error?
- 2 A motor applies a force of 12 N to move a robot at 0.50 m/s. Using P = Fv, what mechanical power is delivered?
- 3 A line-following robot suddenly loses track of the line because the floor becomes darker. Explain which part of the sense-think-act cycle is most directly affected first, and describe how feedback could help the robot recover.