Electric screwdriver control is a typical triple closed-loop control system. The controller contains various tightening strategies, such as the torque/angle method, which uses these control algorithms to real-time regulate the operation of the servo motor.

An electric screwdriver uses a servo motor as its power unit, connected to a reduction mechanism to increase output torque, and then linked to a torque sensor to detect the applied torque. This setup enables precise control of output torque, angle, number of rotations, and other parameters.

The servo motor in the electric screwdriver is equipped with temperature sensors and encoders, which feed back the motor’s temperature and current position to the controller. The torque sensor is installed at the front of the screwdriver to detect the torque output at the front end of the spindle. Different reduction ratios can be configured via the gearbox to achieve different torque outputs.

Servo motors can accurately control speed and position, and industrial-grade electric screwdrivers primarily use servo motors as their power source. Due to the mainstream development trend of high maintenance-free performance, brushless motors are more commonly used.

The servo motor is one of the core components of the electric screwdriver. There are two main types:

• Permanent magnet synchronous AC servo motors

• Induction asynchronous AC servo motors

With the advent of permanent magnet AC servo motors, development has progressed from square-wave-driven motors to sine-wave-driven motors. These motors offer high performance and high torque, making them the preferred choice for high-end electric screwdrivers. Their use significantly extends the service life of the tool, lengthens maintenance intervals, and reduces actual maintenance costs.

The torque output of the electric screwdriver is one of the key factors determining the upper torque limit of the entire tool design. Currently, top international electric screwdriver brands use either proprietary or custom permanent magnet AC servo motors.

A key characteristic of threaded tightening is:

• High-speed operation under no load

• Low-speed operation under overload

At the final stage of thread tightening, general servo motors can only produce a momentary overload of 3 times the rated torque, which falls far short of the multiple overload requirements. Therefore, the unique demands of threaded tightening make it difficult for general-purpose servo motors to adapt to this environment.

Main features of electric screwdrivers:

• Almost noiseless (65 dB)

• Excellent ergonomics

• High precision

• Suitable for various joint types

• Compact size

• Programmable torque

• Data storable

• Wide torque range