Servo Motors: The First Step Towards Your Robot

These devices are considered one of the raw materials in the design and construction of robots. If we combine and manage the movements in a suitable mechanical assembly, a variable group of servomotors can give motricity and locomotion to locally or remotely controlled systems. From small didactic applications to the most complex robotic design . The limits are your imagination and your desire to learn. " Give me a point of support and I will move the world, " Archimedes of Syracuse would have said, perhaps driven by an unbridled enthusiasm for his discovery of the law of the lever. From there begins the history of simple machines, and the device that we will see and apply today in this article is a good example of this. A servomotor is basically a mechanical actuator based on a motor and a set of gears that allow multiplying the torque of the final system, which has control elements to constantly monitor the position of a mechanical element that will be the link to the outside world . That is to say, before an action induced electronically to a servomotor, we will obtain as a result a controlled mechanical response.

For example, the motors that are part of a printer, together with the control systems of advance or retraction of the paper, form a servomotor. A classic servomotor of recognized brand and for simple applications The applications of these slave systems can be observed mainly in model aircraft and robotics , but they are not exclusive to these uses. Any system that requires a precise and controlled mechanical positioning will depend on a servo system or servomechanism, acted, of course, by a servomotor. The zoom of a camera, the autofocus of an optical assembly, a system of mobilization of surveillance cameras and even the automatic doors of an elevator are simple examples of its application. The engine has the characteristic of turning at a good speed, which decreases by the gearboxes of the gearbox that take advantage of this speed to transform it into a work force. When rotating the last gear coupled to the output shaft we obtain a remarkably reduced speed, despite the fact that, inside the system, the motor is rotating at high speeds. Block diagram of the internal structure of a servomotor In addition, in this last coupling wheel we will find stops or limits of travel to deliver a 180 ° turn of the actuator arm in the final output. In most servomotors, this angular displacement is "copied" by a potentiometer incorporated into the control system and mechanically attached to the external axis. This resistive sensor will be responsible for informing the system the position of the external actuator in order to control with accuracy that the positioning instruction sent is being executed faithfully. Connecting a servo The connections are very simple and are based on a regulation of very elementary colors that involve the Red as positive of the main power, along with another cable that can be Black or Brown and that, logically, we can deduce that It's about the negative feed.

A third cable, corresponding to the positioning control of the mechanical actuator, is Yellow or White. In the first image you can see the set of colors Red - Black and Yellow for the connection in servomotors of the HITEC brand. The working voltage of the servomotors is usually between 3 and 7 Volts, with 5 Volts being the voltage used in most fixed applications where a power supply connected to the home power network intervenes, and 6 Volts for cases of battery power when it comes to mobile equipment. In all cases, a control signal of 5 Volts of amplitude is always required. The servo control signal As mentioned at the beginning, servomotors are controlled by variable-width pulses that must be refreshed periodically. This means that if we stop sending the control signal at the time in which the servomotor needs it, it (in spite of being energized) will stop maintaining the pre-established position and will adopt any guidance governed by the effort to which it is subjected. That is, if we do not maintain the control signal effectively as long as necessary, the system will be at the mercy of the external forces to which it is subjected. For example, a lever arm will stop holding an object and will drop the entire mechanical path that can travel, To lock the servomotor in one position it is necessary, then, to continuously send the signal to the desired position. In this way, the control system will continue to operate and the servo will retain its position and will resist external forces that try to change its position.