Modern man cannot imagine his life without the automation of production processes. More and more work is performed by robots and manipulators, replacing humans. Servo drives are widely used in all of these mechanisms. In everyday life, they are found in air conditioning systems, cars, heating appliances, etc. In this article, we will look at the device, principle of operation and scope of the servo drive, so that readers site Electrician himself it became clear what this mechanism is.
Content:
- Purpose and device
- Servo types
- Application area
- Advantages and disadvantages
- Conclusion
Purpose and device
The servo drive is widely used in robotics, mechanical engineering, automobile manufacturing, and process automation in production. With its help, manipulators are activated, opening (full or incomplete) or closing is performed (cover) dampers, in machine tools for the supply of cutting tools and other actuators.
It is a device consisting of an electric motor, a gearbox, a position sensor (encoder) or a resistor and a controller (control device).
In simple words, it is an electromechanical drive that, through internal feedback, sets the exact position of the mechanism shaft depending on external control signals.
The figure shows a section of the device:
Servo drives are available in various capacities and purposes: low power from 0.05 kW, used in automotive and robotics, for example, sg90 and significant power of 15 kW. The latter are mounted in industrial manipulators, CNC machines, for valve control in the oil and gas industry, etc.
An electric motor is not always mounted on a servo drive as a motor. The drive can be a cylinder with a rod, driven by compressed air or liquid.
Servo types
Servos are subdivided into electromechanical. In them, the mechanism consists of an electric motor and a gearbox. They differ in relatively low speed.
Distinguish by the type of engine used:
- synchronous, have a high accuracy of rotation of the output shaft, quickly gain momentum;
- asynchronous, characterized by stable shaft rotation;
- with collector DC or AC motor (universal).
Servos, where the driving mechanism is a piston with a cylinder, have a high speed of response. It is used in a car to switch gears in an automatic transmission. Mounted in robots that move loads over a hundred kilograms. In industrial installations, for switching the dampers in packaging machines, where compressed air is used as an energy carrier.
Main characteristics of the servo:
- The main parameter is the torque or the force on the shaft. In the passport data, two values are indicated, relative to different supply voltages.
- Speed, shows how long it will take to turn the output shaft by 600. Values are indicated for different magnitudes of voltages.
- Whether the control signal is used, analog or digital.
- Supply voltage. Most small drives are powered from 4.8 to 7.2 volts. Used, for example, in radio-controlled models. It is supplied with three wires and has a standard pinout. The control signal is applied to white, brown or yellow, the supply voltage is to red, and the black is the common wire.
- Working angle of rotation, usually 1800 or 3600. Upgraded drives with constant shaft rotation are available;
- Material of manufacture of gears of the reducer. They are made of brass, carbon fiber, plastic or can be combined.
The electromechanical servo drive uses electric motors with a core, which vibrate when the pendulum rotates. This reduces the turning accuracy of the output shaft. Motors with minimal kinetic energy of the rotor are free from this drawback. Such drives are necessary for the CNC machine tool to accurately position the actuator. However, they are more expensive than core motors.
The most common gearbox is gear, which is designed to reduce the speed and increase the torque on the output shaft. Less commonly, a worm gear drive is used, which has a large gear ratio, but is more expensive and more difficult to manufacture.
Application area
The servo is widely used in robotics and manipulators. When creating small mechanisms, use the mg995 servo drive and the like.
Representatives of the Arduino family are often used to control modern drives in amateur radio products. It represents a set of electronic devices designed to control robots and automation devices, where a servo drive is used. The control signal can be analog or digital.
The diagram for connecting the drive to the control device is shown in the figure. The device can control multiple drives.
For underfloor heating, automation is used that maintains the set temperature. And the supply of the coolant, which is hot water from the heating boiler, is regulated by a servo drive.
It is connected to a control device that monitors the temperature using a temperature sensor and issues a command to an electrothermal servo drive RBM 24V. The AC230V servo drive with a regulator can also be used.
Temperature control in heating is carried out automatically, for which a servo drive of the ICMA NC230V or NC24V type is used. The devices are available for various supply voltages.
The unified servo used in the car is small in size. Designed to work with 12 Volt on-board voltage. It is integrated with the central locking system and is installed on all doors of the car, including the fifth door (tailgate).
The mechanism also controls the supply of hot liquid to the stove. It works in tandem with a thermoelectric sensor, the signal from which is sent to the control device. After analysis, the sensor sends a command to the servo, which increases or decreases the flow of fluid.
For example, for VAZ cars, an electric drive with an SL-5 gearbox is used.
This is not a complete list of applications for such devices.
Advantages and disadvantages
The servo drive has advantages over similar devices such as stepper motors. Due to the feedback, the mechanism can correct the position of the shaft, regardless of the axle load, which allows the installation of the working mechanism with high accuracy.
The main advantages are:
- high positioning accuracy;
- with the help of the gearbox, the revolutions are reduced and the torque is increased;
- the positioning of the working body can be easily adjusted by making a change to the control program;
- the ability to achieve large accelerations during operation, which makes the servo more suitable for use in high-speed devices, compared to stepper motors;
- uniform moment in almost the entire speed range;
- well tolerate overload.
The disadvantages include:
- the presence of a gearbox (especially critical if it contains plastic gears or made of soft metals);
- wear of the resistive tracks (if a potentiometer is used for positioning feedback);
- complex adjustment of the control program to obtain high-precision results;
- high cost of equipment (compared to stepper motors, for example);
- accuracy is often less than that of stepper motors.
But keep in mind that all the advantages and disadvantages are averaged, there can be both stepper motors, which in a certain application will show themselves better than a servo, and vice versa.
Conclusion
Automatic control of household and industrial systems has become a part of our life. Recently, the drive under the control of programmable blocks for various purposes, such as arduino, has become widely used.
This made it possible to create fundamentally new amateur flying radio-controlled devices, robots, and children's toys. In industry, the servo drive is used in machine tools, on an excavator, on an ATV, etc. Today it is impossible to imagine our life without servos.
The video shows the operation of the sg90 analog servos in the spider robot model:
Now you know what a servo is, how it works and what it is for. We hope the information provided has helped you master this topic and understand the main points. If you have any questions, ask them in the comments below the article!
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