Overview: Stepper motors are mainly classified according to the number of phases, with two-phase and five-phase stepper motors being the most widely used in the market. A two-phase stepper motor can be divided into 400 equal parts per revolution, while a five-phase stepper motor can be divided into 1000 equal parts. Therefore, the characteristics of a five-phase stepper motor are better, with shorter acceleration and deceleration times and lower dynamic inertia. Comparison of two-phase/five-phase stepper motors: [table][tr][td] [/td][td]Two-phase stepper motor[/td][td]Five-phase stepper motor[/td][/tr][tr][td]Motor structure (please refer to Figure 3)[/td][td]8 main poles ; 4-phase (2-phase) 4-pole coil[/td][td]10 main poles; 5-phase 2-pole coil[/td][/tr][ tr ][td]Decomposition energy[/td][td]1.8°/0.9° (200, 400 divisions/turn)[/td][td]0.72°/0.36° (500, 1000 divisions/turn) 2.5 times higher decomposition energy than the two-phase stepper motor. [tr][tr][td]Vibration[/td][td]The low-speed resonance range is between 100-200 PPS, with relatively large vibrations.[/td][td]Low vibration with no significant resonance point.[/td][/tr][tr][td]Speed-Torque Characteristics[/td][td]Inferior to five-phase stepper motors in terms of speed.[/td][td]High speed, high torque.[/td][/tr][/table] A stepper motor is a discrete motion device, fundamentally linked to modern digital control technology. Stepper motors are widely used in current domestic digital control systems. With the emergence of fully digital AC servo systems, AC servo motors are increasingly being used in digital control systems. To adapt to the development trend of digital control, most motion control systems use stepper motors or fully digital AC servo motors as actuators. Although the two are similar in control methods (pulse trains and direction signals), there are significant differences in their performance and application scenarios. A comparison of their performance is presented below. I. Different Control Precision Two-phase hybrid stepper motors typically have a step angle of 3.6° or 1.8°, while five-phase hybrid stepper motors typically have a step angle of 0.72° or 0.36°. Some high-performance stepper motors have even smaller step angles. For example, a stepper motor produced by Sitong Company for wire EDM machines has a step angle of 0.09°; a three-phase hybrid stepper motor produced by Berger Lahr in Germany has a step angle that can be set to 1.8°, 0.9°, 0.72°, 0.36°, 0.18°, 0.09°, 0.072°, and 0.036° via a DIP switch, making it compatible with the step angles of both two-phase and five-phase hybrid stepper motors. The control precision of AC servo motors is ensured by a rotary encoder at the rear end of the motor shaft. Taking Panasonic's all-digital AC servo motor as an example, for a motor with a standard 2500-line encoder, due to the quadruple frequency technology used in the driver, its pulse equivalent is 360°/10000 = 0.036°. For a motor with a 17-bit encoder, the motor rotates once for every 2^17 = 131072 pulses received by the driver, meaning its pulse equivalent is 360°/131072 = 9.89 seconds. This is 1/655 of the pulse equivalent of a stepper motor with a step angle of 1.8°. Secondly, the low-frequency characteristics differ . Stepper motors are prone to low-frequency vibration at low speeds. The vibration frequency is related to the load and driver performance, and is generally considered to be half the motor's no-load starting frequency. This low-frequency vibration, determined by the working principle of the stepper motor, is very detrimental to the normal operation of the machine. When the stepper motor operates at low speeds, damping technology should generally be used to overcome the low-frequency vibration, such as adding a damper to the motor or using microstepping technology in the driver. AC servo motors operate very smoothly, without vibration even at low speeds. AC servo systems have resonance suppression capabilities, covering insufficient mechanical rigidity, and internal frequency analysis (FFT) functionality to detect mechanical resonance points, facilitating system adjustments. III. Different Torque-Frequency Characteristics Stepper motors' output torque decreases with increasing speed, dropping sharply at higher speeds, thus their maximum operating speed is generally 300-600 RPM. AC servo motors provide constant torque output, meaning they output rated torque up to their rated speed (typically 2000 or 3000 RPM), and constant power output above the rated speed. IV. Different Overload Capabilities Stepper motors generally lack overload capability. AC servo motors have strong overload capability. For example, Panasonic AC servo systems have speed and torque overload capabilities. Their maximum torque is three times the rated torque, which can be used to overcome the inertial torque of inertial loads at startup. Because stepper motors lack overload capacity, a larger torque motor is often selected to overcome this inertial torque during selection. However, the machine does not need such a large torque during normal operation, resulting in wasted torque. V. Different Operating Performance Stepper motor control is open-loop control. Excessive starting frequency or heavy load can easily lead to missed steps or stalling. Excessive speed at stop can cause overshoot. Therefore, to ensure control accuracy, acceleration and deceleration must be properly managed. AC servo drive systems are closed-loop control. The driver can directly sample the encoder feedback signal, internally forming position and speed loops. Generally, the missed steps or overshoot of stepper motors are not present, resulting in more reliable control performance. VI. Different Speed ​​Response Performance Stepper motors require 200-400 milliseconds to accelerate from a standstill to operating speed (typically several hundred revolutions per minute). AC servo systems offer superior acceleration performance. For example, the Panasonic MSMA 400W AC servo motor accelerates from a standstill to its rated speed of 3000 RPM in just milliseconds, making it suitable for applications requiring rapid start-stop. In summary, AC servo systems outperform stepper motors in many aspects. However, stepper motors are still frequently used as actuators in less demanding applications. Therefore, the design of a control system must comprehensively consider factors such as control requirements and cost to select an appropriate control motor. A stepper motor is a discrete motion device, fundamentally linked to modern digital control technology. Stepper motors are widely used in current domestic digital control systems. With the emergence of fully digital AC servo systems, AC servo motors are increasingly being applied in digital control systems. To adapt to the development trend of digital control, most motion control systems use stepper motors or fully digital AC servo motors as actuators. Although their control methods are similar (pulse trains and direction signals), there are significant differences in their performance and application scenarios. A comparison of their performance is presented below. The control precision varies. Two-phase hybrid stepper motors typically have step angles of 3.6 degrees and 1.8 degrees, while five-phase hybrid stepper motors typically have step angles of 0.72 degrees and 0.36 degrees. Some high-performance stepper motors have even smaller step angles. For example, a stepper motor produced by Sitong Company for wire EDM machines has a step angle of 0.09 degrees. A three-phase hybrid stepper motor produced by Berger Lahr in Germany has a step angle that can be set to 1.8 degrees, 0.9 degrees, 0.72 degrees, 0.36 degrees, 0.18 degrees, 0.09 degrees, 0.072 degrees, and 0.036 degrees via a DIP switch, making it compatible with both two-phase and five-phase hybrid stepper motors. The control precision of an AC servo motor is ensured by a rotary encoder at the rear end of the motor shaft. Taking Panasonic's all-digital AC servo motor as an example, for a motor with a standard 2500-line encoder, due to the use of quadruple frequency technology in the driver, its pulse equivalent is 360 degrees/10000 = 0.036 degrees. For a motor with a 17-bit encoder, the motor rotates once for every 2^17 = 131072 pulses received by the driver, meaning its pulse equivalent is 360 degrees/131072 = 9.89 seconds. This is 1/655 of the pulse equivalent of a stepper motor with a step angle of 1.8 degrees. Different stepper motors are prone to low-frequency vibration at low speeds. The vibration frequency is related to the load and driver performance, and is generally considered to be half the motor's no-load starting frequency. This low-frequency vibration, determined by the working principle of the stepper motor, is very detrimental to the normal operation of the machine. When the stepper motor operates at low speeds, damping technology should generally be used to overcome the low-frequency vibration, such as adding a damper to the motor or using microstepping technology in the driver. AC servo motors operate very smoothly, without vibration even at low speeds. AC servo systems have resonance suppression capabilities, covering insufficient mechanical rigidity, and internal frequency analysis (FFT) functionality to detect mechanical resonance points, facilitating system adjustments. The torque-frequency characteristics of motors differ from those of synchronous motors. The output torque decreases with increasing speed, dropping sharply at higher speeds, thus their maximum operating speed is generally between 300 and 600 RPM. AC servo motors provide constant torque output, meaning they output rated torque up to their rated speed (typically 2000 or 3000 RPM), and constant power output above the rated speed. Overload capacity differs from that of synchronous motors, which generally lack overload capacity. AC servo motors, however, possess strong overload capacity. For example, Panasonic AC servo systems have speed and torque overload capabilities. Their maximum torque is three times the rated torque, which can be used to overcome the inertial torque of inertial loads at startup. Because stepper motors lack overload capacity, a larger torque motor is often selected to overcome this inertial torque during selection. However, the machine does not require such a large torque during normal operation, resulting in wasted torque. The operating performance differs from stepper motors. Stepper motor control is open-loop control; excessively high starting frequency or heavy load can easily lead to missed steps or stalling, while excessively high stopping speed can cause overshoot. Therefore, to ensure control accuracy, acceleration and deceleration issues must be properly addressed. AC servo drive systems use closed-loop control. The driver can directly sample the motor encoder feedback signal, internally forming position and speed loops. Generally, the missed steps or overshoot of stepper motors are not observed, resulting in more reliable control performance. Speed ​​response performance differs from stepper motors. Stepper motors require 200-400 milliseconds to accelerate from a standstill to operating speed (typically several hundred revolutions per minute). AC servo systems have better acceleration performance. For example, the Panasonic MSMA 400W AC servo motor accelerates from a standstill to its rated speed of 3000 RPM in just a few milliseconds, making it suitable for control applications requiring rapid start and stop. In summary, AC servo systems outperform stepper motors in many aspects. However, stepper motors are still frequently used as actuators in applications with less stringent requirements. Therefore, in the design of control systems, factors such as control requirements and cost must be comprehensively considered to select an appropriate control motor. A stepper motor is an actuator that converts electrical pulses into angular displacement. Simply put, when a stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle (the step angle) in a set direction. You can control the amount of angular displacement by controlling the number of pulses, thereby achieving accurate positioning; simultaneously, you can control the motor's speed and acceleration by controlling the pulse frequency, thereby achieving speed regulation. Stepper motors are divided into three types: permanent magnet (PM), reactive (VR), and hybrid (HB). Permanent magnet stepper motors are generally two-phase, with smaller torque and size, and a step angle of 7.5 degrees or 15 degrees; reactive stepper motors are generally three-phase, capable of high torque output, with a step angle of 1.5 degrees, but with significantly higher noise and vibration. In developed countries like Europe and America, this technology was phased out in the 1980s. Hybrid stepper motors combine the advantages of permanent magnet and reactive motors. They are further divided into two-phase and five-phase: two-phase stepping angles are generally 1.8 degrees, while five-phase stepping angles are generally 0.72 degrees. This type of stepper motor is the most widely used. [b]1. How to correctly choose a servo motor and a stepper motor?[/b][/align][align=left] It mainly depends on the specific application. Simply put, you need to determine: the nature of the load (e.g., horizontal or vertical load), torque, inertia, speed, accuracy, acceleration/deceleration requirements, upper-level control requirements (e.g., port interface and communication requirements), and the main control method (position, torque, or speed). Also, determine whether the power supply is DC, AC, or battery-powered, and the voltage range. Based on this, determine the model of the motor and the corresponding driver or controller. [b]2. Should I choose a stepper motor or a servo motor system?[/b] Actually, the choice of motor depends on the specific application, as each has its own characteristics. Please see the table below for clarification. [table=552][tr][td=1,1,96] Parameters [/td][td=1,1,228] Stepper Motor System [/td][td=1,1,228] Servo Motor System [/td][/tr][tr][td=1,1,96] Torque Range [/td][td=1,1,228]Small to Medium Torque (generally below 20Nm)[/td][td=1,1,228]Small, Medium, Large, Full Range[/td][/tr][tr][td=1,1,96] Speed ​​Range [/td][td=1,1,228]Low (generally below 2000RPM, high torque motors less than 1000RPM) [td=1,1,228]High speed (up to 5000 RPM), DC servo motors can reach 10,000 to 20,000 RPM[/td][/tr][tr][td=1,1,96] Control methods [/td][td=1,1,228]Primarily position control[/td][td=1,1,228]Diverse and intelligent control methods, position/speed/torque[/td][/tr][tr][td=1,1,96] Smoothness[/td][td=1,1,228]Vibration at low speeds (but can be significantly improved with microstepping drivers)[/td][td=1,1,228]Good, smooth operation[/td][/tr][tr][td=1,1,96]Precision [/td][/tr][tr][td= 1,1,96 ] The torque characteristic is generally low, but higher in microstepping drives. It depends on the resolution of the feedback device. At high speeds, the torque decreases quickly, resulting in good torque characteristics, but the characteristics are relatively stiff. Overload characteristics are also important. [td=1,1,228]Overload will cause loss of synchronization[/td][td=1,1,228]Can withstand 3 to 10 times overload (short time)[/td][/tr][tr][td=1,1,96] Feedback method [/td][td=1,1,228]Mostly open-loop control, but can also be connected to an encoder[/td][td=1,1,228]Closed-loop method to prevent loss of synchronization, encoder feedback[/td][/tr][tr][td=1,1,96] Encoder type [/td][td= [1,1,228]Photoelectric rotary encoder[/td][td=1,1,228](Incremental/Absolute), rotary transformer type[/td][/tr][tr][td=1,1,96] Response speed [/td][td=1,1,228]General[/td][td=1,1,228]Fast[/td][/tr][tr][td=1,1,96] Vibration resistance [/td][td=1,1,228]Good[/td][td=1,1,228] Generally (rotary transformer type, vibration resistant) Temperature rise: High operating temperature, moderate maintenance, basically maintenance- free. Price: Low. (b) 3. How to use a stepper motor driver? Based on the motor's current , use a driver with a current greater than or equal to that current. If low vibration or high precision is required, a microstepping driver can be used. For high-torque motors, use high-voltage drivers whenever possible to achieve good high-speed performance. [b]4. What are the differences between 2-phase and 5-phase stepper motors, and how to choose between them?[/b] 2-phase motors are low-cost, but they vibrate more at low speeds and their torque drops quickly at high speeds. 5-phase motors have less vibration, better high-speed performance, and are 30-50% faster than 2-phase motors, and can replace servo motors in some applications. [b]5. When to choose a DC servo system, and what are the differences between it and an AC servo system?[/b] DC servo motors are divided into brushed and brushless motors. Brushed motors are low-cost, simple in structure, have high starting torque, wide speed range, and are easy to control. They require maintenance, but maintenance is convenient (replacing carbon brushes). They generate electromagnetic interference and have environmental requirements. Therefore, they can be used in cost-sensitive general industrial and civilian applications. Brushless motors are small in size, light in weight, have high output, fast response, high speed, low inertia, smooth rotation, and stable torque. Control is complex, but intelligent control is easily achieved. Their electronic commutation method is flexible, allowing for square wave or sine wave commutation. The motor is maintenance-free, highly efficient, operates at low temperatures, has minimal electromagnetic radiation, and a long lifespan, making it suitable for various environments. AC servo motors are also brushless motors, available in synchronous and asynchronous versions. Currently, synchronous motors are generally used in motion control due to their wide power range and ability to achieve high power outputs. They have high inertia, low maximum rotational speed, and their speed decreases rapidly with increasing power. Therefore, they are suitable for low-speed, stable operation applications. [b]6. What issues should be considered when using the motor?[/b] Before powering on, the following checks should be performed: 1) Is the power supply voltage appropriate (overvoltage may damage the drive module); the +/- polarity of the DC input must not be incorrect; is the motor model or current setting on the drive controller appropriate (do not set it too high initially); 2) Ensure the control signal lines are securely connected; in industrial settings, shielding should be considered (e.g., using twisted-pair cables); 3) Do not connect all the necessary wires at the beginning; only connect the most basic system. After it runs well, gradually connect the others. 4) Be sure to understand the grounding method, whether to use a floating connection or not. 5) During the first half hour of operation, closely observe the motor's status, such as whether the movement is normal, the sound, and the temperature rise. If any problems are found, stop the machine immediately for adjustment.