Servo motors are the name given to the structural unit of a servo system, used alongside servo drives and servo drive controllers. This unit includes a motor, which will drive the load in question, along with an encoder or other position detection device, and power transmission mechanism. By using a servo system, the user can vary factors such as speed, torque, and position, in order to achieve precise control over the machine's operation.

As such, a typical servo system is comprised of three sections: the command section, which features a servo drive controller, in which the target value commands for the machine's operation are output, and feedback signals are received; the control section, which features the servo drive and forwards the input target value commands to the motor; and the drive and detection section, which comprises the servo motor itself. The system, therefore, controls the machine's operation through a loop, with the speed, torque and position of the working servo motor being fed back to the servo drive and the servo drive controller, allowing for comparison to the chosen target values for these variables in real-time. The servo drive can then adjust and correct any errors or variations between the target values and the actual values for torque, speed, or positioning, ensuring that the machine operates as intended.

Unlike a typical motor, such as a stepper motor, servo motors feature a positioning detection device such as an encoder. This means that there are many benefits of using a servo motor, including the excellent positioning and speed control, in which even flexible and precise positioning may be achieved. Thanks to the use of an encoder (or other position detection device) which acts to correct any deviations caused by external forces, servo motors do not stall, even at the highest speeds.

When using servo drives, there are three options to choose from: a closed loop, semi-closed loop, or an open loop. For the highest degree of precision, a closed loop system is advisable. This sees the servo motor controlled whilst directly reading the machine's position with a linear encoder. This position is then compared to the target value for position and avoids the need to compensate for factors such as gear backlash between the servo motor and the mechanical system, or for errors caused by screw torsion or expansion.

A semi-closed loop, meanwhile, offers fast and accurate positioning, and is typically used with servo systems. In this type of system set-up, the encoder or other positioning detection device is installed behind the servo motor, and works to detect the rotation angle of a feeder ball screw, thereby using this to return feedback of the servo machine's travel position. This means that the position of the machine is not detected directly, and so some compensation for deviations due to the screw's torsion, expansion, or pitch error may be required.

In an open loop system, a servo motor is replaced with a stepper motor, so no positioning detection device is included, and no ball screw errors can be corrected. However, this kind of set-up is useful as a low-cost, low-speed solution where precision is not essential.

Here at Olsen Actuators, our extensive product range includes a wide variety of devices for creating your ideal servo system. Our selection includes servo drive controllers, servo drives, and servo motors, enabling you to configure the set-up that best suits your needs. Our range includes market leading servo drives, as well as the highly customisable and high performance Mil-Spec ready range servo drives by ESI Motion.

Delivering revolutionary efficiency, our range of servo motors and drives is ideal for even the most rugged of applications, allowing you to achieve maximum precision and incredible power, whilst being small, lightweight, and scalable. That's why our modular product range has been field tested successfully in Space, Defence, and Aerospace applications. Furthermore, as the experts in this area, we can create a bespoke solution for any specification you may require: simply get in touch to find out more.