Working Principle of Linear Servo Motor

Linear servo motors, also called permanent magnet linear servo motors, generate thrust and speed based on supply current and voltage, and perform linear motion along the driven axis. A linear servo motor is an integral part of a closed-loop system, providing thrust and speed based on commands from the servo controller using a feedback device to achieve a closed-loop.

How does a linear servo motor work?

A screw and a nut are engaged, and some method is used to prevent the relative rotation of the screw and nut, so that the screw is moved axially. Generally speaking, there are currently two ways to achieve this transformation. The first is to build a rotor with an internal thread in the motor, and the internal thread of the rotor and the screw are meshed to achieve linear motion. The second is to use the screw as the the motor exits the shaft, and an external drive nut engages with the screw outside the motor to achieve linear motion. The result is a greatly simplified design, enabling the use of linear servo motors for precise linear motion without the need for external mechanical linkages in many applications.

If the current is switched in the order of ①, ②, ③, and ④, the coil current is used to excite the two magnetic poles to generate opposite polarities, which are superimposed with the magnetic flux generated by the permanent magnet. Subtraction, when the magnetic flux generated by the winding is the same as that of the permanent magnet, the magnetic flux of the subtracting magnetic pole is zero. At this time, the magnetic flux of the permanent magnet passes through the excitation magnetic pole in the same direction, and passes through the two magnetic poles of the stator yoke and the mover. , return to the other pole of the permanent magnet, ①, ②, ③, ④ switch the excitation current in sequence, and the rotor moves to the right by 1/ 4 of the stator tooth pitch each time.

Advantages of linear servo motor

• High-speed response: Generally speaking, the dynamic response time of mechanical transmission parts is several orders of magnitude larger than that of electrical components. Because some mechanical transmission parts such as lead screws with large response time constants are eliminated in the system, the dynamic response performance of the entire closed-loop control system is greatly improved, and the response is extremely sensitive and fast.
• High precision: Since the mechanical transmission mechanism such as the lead screw is cancelled, the tracking error caused by the lag of the transmission system during interpolation is reduced. Through the linear position detection feedback control, the positioning accuracy of the machine tool can be greatly improved.
• High transmission rigidity and stable thrust.
• Fast speed, short acceleration and deceleration process.