Servos are devices that are used for operating remote-controlled cars. This gets done by determining the direction of the motion. Aside from the fact that they get used for RC vehicles, they also get used in electronic toys, robots, and electrical appliances. In this piece, we will be looking at how to control a digital servo controller.

What is a digital servo?

The original servos were the analog ones which function on a 10-volt input. The digital servo functioned over Fieldbus networks which are now common in the market. The main difference that exists between analog and digital servos is that the digital servo comes with a microprocessor that implements computation. The microprocessors help determine the output control signal based on a mathematical model of the behavior of the system.

The majority of digital drives can accept feedback from resolvers, tachometers, encoders, and different switch and sensor types. Added to managing the velocity, torque, and position control loops, digital servo drives usually come with higher levels of functionality. They include certain operations like path generation which is usually handled by the machine controller.

How to control a digital servo

Digital servos receive the same pulse repetition rate and pulse width as the regular analog servos. Digital servos get controlled by microcontrollers. The standard servo composes of a potentiometer, electric motor, and gearbox, and control electronics. The output position of the shaft gets measured using the internal potentiometer and this gets controlled using the controller.

Based on the error, the control electronics change the real position of the output shaft to ensure that it matches the position targeted. This system is the control-loop system.

The gearbox then lowers the motor speed and increases the output shaft torque. Servo motors get controlled by relaying a pulse-width modulation signal to the signal line of the servo. The pulse width determines the output shaft position.

What are the differences between using a digital and analog servo?

Digital servos have different ways of relaying pulse signals to the servo motor. For instance, if the analog signal relays 50 pulse volts each second, the digital servo will be able to send 300 pulses per second. With the rapid pulse signals come a significant increase in the speed of the motor. Also, there will be an increase in the torque consistency as the Deadband gets reduced. Due to this, when a digital servo gets used, it gives a prompter response and quicker acceleration to the RC component.

With fewer Deadband, there will be a better holding capacity for the torque. Thus, when you use a digital servo, you will be able to experience a prompt feeling of control. For instance, if you connect an analog and digital servo to a receiver when you switch the servo wheel off-center, you will see it takes a while to respond. But if you turn the wheel of the digital servo off-center, there will be a prompt response of the shaft and wheel. It will also hold the position which you set quite smooth and quick.

Benefits of using a digital servo

Even though analog servo drives are quite cheaper and easier to set up, some advantages make digital servos outstanding. For instance, digital servo drives can get tuned using software, as against using potentiometers.

A lot of digital drives can be self-tuned or auto-tuned which is quite beneficial when the inertia or load parameters are too complex to predict or model. This also ensures the simplification of the tuning process and gives a system that is quite responsive. Because all the tuning and configuration settings get stored within the drives, it is very easier to recreate a particular setup across the diverse drives.

Auto tuning involves setting the servo-loop gains. The drive then excites an attached motor at diverse frequencies to sense the response and inertia of the system. It then proceeds to set and determine the requisite gains to make sure that there is stability at different frequencies.

Using a digital servo, the voltage pulses get sent to the motor at a frequency that is up to five times higher than with an analog drive. This ensures that the motor responds to commands quicker. It also makes available a smoother deceleration and acceleration. It makes sure the servo system has a bigger holding torque.

Digital servos have diverse functions. The majority of digital servos can operate using analog voltage signals like analog servo drives. Some of them can also accept direction and step signals to function as a stepper drive. They may also get used when slave and master axes are needed using an electronic cam or gearing between the axes.

Conclusion

Using digital servo motors has revolutionized how certain electronics work. Understanding the working principles of digital servo motors is vital for making the most of their potential.