How Does a Servo Drive Work? Understanding the Power Behind Precision

A Servo Drive vs. a Standard Drive

Standard drives, like those you might find in fans or drills, simply start and stop their motors, maybe changing speed in a rough way. But servo drives are different — they're all about control. They monitor the motor's every move, adjusting it in real-time to be as accurate as possible.

If a standard drive is like using a light switch to turn a lamp on and off, a servo drive is like having a dimmer switch plus a color and angle adjuster — it gives you complete control over the light's intensity, color, and direction. This level of control makes servo drives invaluable in modern machinery, where precision is essential.

Built-In Versatility

Servo drives are versatile and can regulate motors of varying sizes. For instance, they might control smaller motors found in the elbow joint of a robotic arm. On the other end of the spectrum, they also handle larger motors used in heavy industrial equipment or in the wheels of electric vehicles. Essentially, the more powerful the motor, the more robust the servo drive needs to be.

The Controller

It all starts with the controller, which ranges from something as basic as a knob to as sophisticated as a computer program.

This controller dispatches a signal — a precise, minor burst of electricity — to the servo drive's command input. The servo drive, in turn, boosts this signal to generate the necessary current or voltage for the motor.

The Power Source

The servo drive gets the energy to boost the signal from the drive's power source, which could be a battery or a main electricity connection. This source supplies a steady flow of voltage. The servo drive then allocates this power to the motor, modifying it as required in response to the controller's commands.

The Motor

An electric motor consists of two principal components: the rotor, which rotates and is connected to the shaft, and the stator, which remains stationary and is fixed to the frame. One of these elements contains permanent magnets, while the other houses wire coils, also known as electromagnets, which are activated when the servo drive sends current through them.

Activating different sets of these coils in sequence creates a rotating magnetic field. This interacts with the fixed magnets, causing the rotor to turn.

The amount of current flowing through the coils controls the torque, while the voltage governs the motor's speed. By meticulously adjusting the current and voltage, the servo drive precisely manages the motor's torque, speed, and position.

Feedback Mechanism

Feedback is part of everyday life. Your car's speedometer lets you know if you need to adjust your speed. A kitchen thermometer tells you if your roast is cooked to perfection. Similarly, a feedback mechanism or encoder lets a servo drive know if it needs to adjust the current or voltage.

This feedback loop is critical as it enables the servo drive to adjust the electricity flowing to the motor in real-time. The encoder's role in the feedback loop is vital. It acts as the eyes of the system, providing constant, real-time updates on the motor's status. This feedback enables the servo drive to make instantaneous adjustments, ensuring the motor's performance aligns precisely with the set commands. This adjustment lets the motor operate with the correct torque, speed, and position despite any external disturbances.

Take the incremental encoder, a typical feedback mechanism that monitors rotational movement. Imagine an external force unexpectedly slows down the motor. The feedback device records the motor's actual speed and sends this information back to the servo drive. The servo drive then compares the actual speed against the desired speed and adjusts the motor's power accordingly, ensuring it returns to the correct speed.

Servo Drive Working Principle

The fundamental working principle of a servo drive is based on the closed-loop control system. This system is pivotal in achieving the high levels of precision and efficiency for which servo drives are known. In a closed-loop system, the servo drive operates in a cycle of continuous feedback and adjustment to maintain the motor's operation within the desired parameters. The controller, power source, and feedback mechanism all work together to create the continuous feedback cycle that allows the servo drive to control the motor.