Design of linear servo motor and its drive controller for compressor

Abstract: This paper introduces a linear servo motor for refrigeration compressors. The motor is small in size, exhibits low vibration, and has a long lifespan. The basic structure of the motor and the design of its drive controller are described, and some key technologies and challenges in the design are analyzed.

Keywords: Linear motor, Servo motor, Driver, PID control, Refrigeration compressor application

0 Introduction

As a key component of Stirling refrigerators, the linear servo motor's control performance directly affects the entire system. Currently, permanent magnet brushless linear motors are generally used as servo motors. This paper presents a system using dual linear motors to drive the compressor. The integrated design of the dual linear motors and compressor effectively utilizes space and reduces the size of the Stirling refrigerator. Dual linear motors driving the compressor result in symmetrical force distribution and low vibration. To further reduce vibration and electromagnetic interference, the motors employ sinusoidal wide-range modulation (SLP) drive, and temperature regulation uses digital incremental PID control. The entire drive controller operates under the coordination of a microcontroller.

1. Basic structure of an electric motor

The basic principle of the electric motor is that a conductive coil carrying a sinusoidal alternating current reciprocates under the action of a constant magnetic field, driving a piston to compress or pull out the working gas in a cylinder, generating an alternating pressure wave. This wave is transmitted through a hollow tube to an expander and converted into cooling energy, which in turn allows infrared devices to sensitively observe the infrared signal of the target. After processing by a computer, an image is formed.

To maximize space utilization and reduce volume, the motor and compressor of the refrigeration unit are integrated into a single structure. The compressor and dual linear motor are combined, with the compressor's cylinder and piston located inside the motor. The cylinder body serves as the motor's internal magnet, and the piston also supports the motor's reciprocating motion. Due to the short motor stroke, the mover coil uses a brushless structure with flexible wire connections. The spring within the coil acts as both a support and an energy storage element. Under conditions of parameter matching between the spring, motor, and compressor, the system operates in resonance, achieving maximum efficiency.


For details, please click: Design of Linear Servo Motor and Drive Controller for Compressors