Servo drive - what is it? Device, installation and operating principle of the servo drive

Many people ask: servo - what is it? The classic design of the servo drive includes a motor, a position sensor and a three-loop control system (position, speed and current control).

The word "servo" has the Latin origin "servus", literally translated as "slave", "helper", "servant".

In the machine building industry, the devices acted as auxiliary components (feed drive in a machine, robot, etc.). However, today the situation has changed, and the main purpose of the servo drive is to implement in the field of servomechanisms.

Installing the servo drive is justified when conventional frequency converters regulate the accuracy of the operation inadequately.

The use of high-quality devices is necessary in equipment characterized by a high level of productivity.

This article will tell you about the servo drive, what it is and how it functions.

Areas of use for the device

In the modern world, when automation has taken a strong position in all areas of engineering, the design of all mechanisms is noticeably unified. At the same time, modern individual drives are used.

In order to understand the servo, what it is, you should know the scope of the device.

The devices contain precise speed-keeping designs in industrial robots and machine tools with high accuracy. They are mounted on drilling equipment, in various transport systems and mechanisms of ancillary nature.

The widest application of devices found in the following areas:

• Manufacture of paper and packages;
• Manufacturing of sheets from metal;
• Processing of materials;
• Production of transport equipment;
• Woodworking industry ;
• Manufacturing of building materials.

Servodrives on the trunk of the car

There are many models of servo drives for the trunk of the car from different manufacturers. Consider the functionality of such a device as the trunk servo from the domestic manufacturer Avtozebra. The device is designed for Russian cars, but not only. For example, it can be used in a Renault Logan car.

According to user feedback, this design is convenient. It allows, without leaving the car, to open and close the trunk.

The device is controlled by means of a button mounted in the car interior or in the alarm keychain.

Reason for wide use of the device

The reason for the frequent use of servo drives are:

• The possibility of obtaining control, which is distinguished by high accuracy and stable functioning;
• Wide range of speed control;
• High level of immunity to interference;
• Small size and weight of the device.

Principle of servo operation

How does the device work? Servo, the principle of operation of which is based on feedback with one or more system signals, regulates the object. The output value of the device goes to the input, where a comparison with the setting action takes place.

Features of the mechanism

The servo device has two main features:

• Ability to increase power;
• Provision of feedback information.

The amplification is required for the purpose that the energy needed at the output is very high (it comes from an external source), and its input is insignificant at the input.

Feedback is nothing more than a circuit with a closed circuit in which signals are not matched at the input and output. This process is used for management.

Hence the conclusion: the contour in the forward direction serves as the energy transmitter, and in the reverse direction it is the transmitter of information that is needed for the accuracy of control.

Power and pinout connectors

Servo, the principle of operation of which is applicable in radio-controlled configurations, usually has three wires:

1. Signaling. It transfers the control pulse. Typically, the wire is painted white, yellow or red.
2. Feeding. The indicator of its power is from 4.8 to 6 V. It is often a red wire.
3. Earthing. The wire is black or brown.

Dimensions of actuators

In size, the aggregates are divided into three categories:

• Microdrives;
• Standard modifications;
• Large devices.

There are servos and with other dimensions, however, the above types are 95% of all devices.

Main characteristics of the product

Servo operation is characterized by two main indicators: the speed of rotation and the force on the shaft. The first value serves as an indicator of the time, which is measured in seconds. The effort is measured in kg / cm, that is, what level of effort the mechanism develops from the center of rotation.

In general, this parameter depends on the main purpose of the device, and only then on the number of transmissions of the reducer and the units used in the device.

As already mentioned, now produce mechanisms that operate at a power supply voltage from 4.8 to 6 V. This is often equal to 6 V. However, not all models are designed for a wide range of voltages. Sometimes the servo motor works only at 4.8 V or only at 6 V (the latter configuration is extremely rare).

Analog and Digital Modifications

A few years ago, all servos were analog. Now there are also digital designs. What is the difference between their work? Let's look at the official information.

From the report of the company Futaba it follows that over the last decade, servo drives have become more technically better than before, as well as small size, high level of rotation speed and the index of torsion elements.

The last stage of development is the appearance of the device on a digital basis. These units have significant advantages even before the motors of the collector type. Although there are some disadvantages.

Externally, analog and digital devices are indistinguishable. The differences are fixed only on the device boards. Instead of a chip on the digital unit, you can see a microprocessor analyzing the receiver's signal. He controls the engine.

It is completely wrong to say that the analog and digital modifications radically differ in their functioning. They can have the same engines, mechanisms and potentiometers (variable resistors).

The main difference is the way of processing the incoming signal of the receiver and controlling the motor. Both the servo drives the same signal of the radio receiver.

So, it becomes clear, servo, what is it?

Principle of operation of analog modification

In the analog modification, the received signal is comparable to the current position of the servomotor, and then the signal of the amplifier is applied to the motor, causing the motor to move to the specified position. The frequency of the process is 50 times per second. This is the minimum response time. If you turn the knob on the transmitter, short pulses will start to act on the servo, the gap between them will be equal to 20 m / sec. There is nothing between the pulses on the motor, and external influences can change the operation of the device in any direction. This time period is called the "dead zone".

Principle of operation of digital construction

Digital devices use a special processor that operates at high frequencies. It processes the receiver signal and sends control pulses to the engine with a frequency response 300 times per second. Since the frequency indicator is much higher, the reaction is much faster and keeps the position better. This causes optimal centering and a high level of torsion. But this method requires a lot of energy, so the battery used in the analog mechanism will be discharged much faster in this design.

However, all users who once faced the digital model say that its difference with the analog design is so great that they would never use the latter any more.

Conclusion

Your choice will be digital analogs, if you need:

• High level of resolution ;
• Minimum number of "dead zones";
• Exact positioning level;
• Quick response to the team;
• Uninterrupted force on the shaft when turning;
• High power level.

Now you know what a servo is and how to use it.