Brushless Servo Drive
A servo motor is a motor with an encoder mounted in it, making highly accurate position, speed, and torque control possible. It also has a complex electronic system for commutation.
A microprocessor constantly monitors the currents in the rotor and stator to achieve the desired position, velocity or torque that is commanded through a network interface.
Power
As the name suggests, a brushless servo motor does not use brushes to connect current to the moving armature. Instead, they are powered electronically and a controller manages the power distribution to keep them rotating. This system eliminates mechanical contact between the brushes and commutator, resulting in higher torque, lower noise and longer lifespan of the motor.
These motors use a fixed armature with permanent magnets and a stator of coils arranged along the diameter. When current flows through these coils they generate magnetic fields that attract or repel the rotor’s permanent magnets, keeping the armature turning. These motors are a popular choice in applications that require reliability, accuracy and efficiency.
The high speed and dynamic accuracy required by servo control–speed regulation, dynamic positioning and settling time–require a motor that is responsive, both electromagnetically and mechanically. This requires a fast electrical time constant that minimizes steady-state torque droop and an inertia that provides a high torque-to-inertia ratio so more of the available peak torque can be used to accelerate the load.
The broad range of brushless servo drives from Everest S NET offers solutions for all of these demanding applications. Their flexibility and ease of use help engineers cut commissioning times and enable them to rapidly set up their servo drive for optimal performance. They support a wide range of control brushless servo drive methods from pulse & direction, analogue torque/velocity and streaming serial commands to full execution of stored programs.
Torque
Brushless servo motors operate within a closed-loop feedback system that continually monitors their position, speed and torque. This real-time feedback lets them adjust their performance to maintain optimal efficiency and accuracy under varying load conditions.
The rotor has permanent magnet segments fitted into a shaft that rotates around a fixed stator. The stator has copper wire windings with a pattern that compliments the rotor magnets. The motor has an insulation system that keeps the copper wires a full 65oC below their rated maximum temperature to avoid thermal damage.
When the servo drive detects that the rotor position sensor is no longer producing a valid signal, it shuts off the current flow to the rotor. It then uses a control loop to monitor the output position sensor and speed of the servo motor to determine whether or not it should restart. This feature is called Safe Torque Off (STO) and allows you to gain access to moving mechanical parts without worrying about the motor restarting.
Brushless servo drives control the voltage to the rotor and stator windings using high-performance microprocessors that continuously check the status of the motor’s currents to ensure a desired position, velocity or torque is achieved through closed loop control. This close integration reduces the amount of heat generated by the servo motor and helps to extend its lifespan. It also lowers the total cost of ownership as it reduces application power requirements.
Speed
A high-performance servo motor requires a fast electrical and mechanical response. This is needed to achieve dynamic accuracy and velocity regulation and provide short settling times. Fast electrical response minimizes steady-state torque droop, and fast mechanical response reduces torque ripple and vibration to create smooth motion.
Brushless servo drives have the power to meet the needs of demanding applications. They are used in robotics, brushless servo drive manufacturer CNC automation, medical imaging, wafer spinning and more. With the right brushless servo drive, you can achieve position control with high precision and a good power-to-weight ratio at an affordable cost.
Compared to traditional DC motors, a brushless servo drive provides enhanced reliability and efficiency through electronic commutation. Instead of physical brushes interacting with a physical commutator, a servo motor uses Hall Effect ICs to detect the position of the moving parts and direct current accordingly. This allows for continuous, closed-loop speed control and prevents voltage surges that can damage the commutator and cause unwanted operation such as servo hunting. As a result, the drive is maintenance-free and more reliable. It also reduces sparks and fire hazards in the machine, and makes the workplace safer for human operators. The motor also has a lower power-to-weight ratio and is smaller and lighter than brushed DC motors, making it easier to integrate into the application and reduce space requirements.
Position
A servo drive is the device that takes command signals from a motion controller and a feedback encoder and escalates them into a servo motor current to control position, speed or torque. They are used in a variety of machines including robots, CNC machining and power steering in cars.
They commutate motors that are either brushed DC or AC brushless designs. They are able to do this because the servo drives use intelligent microprocessors that produce pulse width modulated (PWM) waveforms to energize motors by making electrical contacts with segments on a rotary electrical switch called a commutator, which is located in the rotor.
In applications that require only a current loop, the servo drives may close that only, but more commonly they will also need to close the velocity and position loops. The position loop employs a sensor that provides velocity information to the servo drive, and the drive then relays that data back to the current loop to regulate torque.
In some cases, a person can function as the controller and manually adjust the potentiometers on analog or digital servo drives to achieve the desired result. This is not a recommended practice, however, as it can create instability in the system. It is far better to have a motion controller or an expert technician set up the machine and install a properly calibrated servo drive for maximum performance.