JNTU B.Tech IV INTRODUCTION TO MECHATRONICS Previous Question Paper (July/August - 2022 - R16)

A digital camera with triangulation uses active or passive triangulation to determine the distance of an object from the camera. In an active triangulation system, the camera projects a structured light source, such as a laser line or a dot pattern, onto the target object. The camera sensor detects the position of the reflected light. Because the distance between the light source and the camera lens (the baseline) is known, the system uses the law of sines or trigonometric relationships to calculate the depth of the object based on the displacement of the reflected light on the imaging sensor.

The working principle relies on the geometry of the triangle formed by the light source, the object, and the camera sensor. As the object moves closer or further, the angle of the reflected light changes, causing the projected pattern to shift its position on the camera's CCD or CMOS sensor. By processing this shift, the camera calculates the precise distance, enabling 3D mapping and autofocus capabilities.

The fundamental difference between open and closed-loop control lies in the presence of feedback.

Open-loop control: In this system, the control action is independent of the output. The controller sends a signal to the actuator based on a predetermined input or timing, without monitoring the actual state of the process. It is simple, inexpensive, and stable, but it is highly sensitive to external disturbances and parameter variations. An example is a toaster, which heats for a set time regardless of the bread's actual temperature.

Closed-loop control: This system utilizes a feedback loop where the actual output is measured by a sensor and compared against a desired reference input. The difference, known as the error signal, is fed back to the controller to adjust the actuator's output continuously. This allows the system to compensate for disturbances and maintain accuracy. While more complex and costly to implement, it provides superior precision and reliability. An example is an air conditioning system that monitors room temperature to adjust its cooling output.