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Mechanisms are essentially used for converting motion from one form to another. Mechanical actuation systems mainly consist of mechanisms. If a number of rigid bodies are assembled together in such a way that the motion of one causes constrained or predictable motion of the others, it is called a mechanism. Thus, a mechanism transmits and modifies a motion.  The mechanism can be used for the following purposes: Transform linear motion into rotational motion (Example: IC engine) Transform a rotary motion into translating motion (Example: Cam and follower) Transform motion in one direction into another direction at right angles (Example: bevel gear or worm gear) Change (increase or decrease) and change the direction of the rotational speed of one drive to another (Example: gear trains) Figure 1. Linear to rotational motion transformation in IC engines Figure 2. Rotary to linear motion transformation in cam and follower Figure 3 Transformation of motion in one direction into another using

In a modern camera using film, we can see automatic focusing and exposure facilities. The basic elements of the control system used in an automatic camera are body, lenses, and flash. Figure 1 depicts an automatic camera system. Figure 1: Components of an automatic camera Figure 2. Key components of an automatic camera and its block representation Depending upon the model selected, the required combination of aperture and shutter speed and focus are automatically taken care of by the camera.  A typical camera system comprises drives and sensors, interfaces for lenses, flash, and user.  Drives are required for film advance, rewind, shutter movement, focusing, zoom, etc.  The sensors are essentially used for sensing film speed, counters, focus, exposure, zoom, etc. Microprocessor systems for lenses, a user(s), and flash are incorporated for controlling various operations. Figure 3 Working of autofocus system of automatic camera The user is expected to feed information for achieving the

The washing machine is an example of a  sequential control system.  A system operating with sequential control is one where a number of preset operations are performed in sequence.  The control may be implemented as  event-based,  where the next action cannot be performed until the previous action is completed.  Another mode of sequential control is termed  "time-based",  where the operations are sequenced with respect to time. Example: An example of a time-based sequential control system is shown in the following Figure 1. The pump (fill valve) is switched ON for a particular time to fill enough water into the tank to fill it to approximately the correct level. Following this, the pump is switched OFF.   Figure 1: Time-based sequential control Among these two modes,  event-based control  is intrinsically  more reliable  than time-based control.  An example of an event-based sequential control system is a washing machine. In this system, a number of operations or events h