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HomeNewsStepper motors replace some servo motors at low cost

Stepper motors replace some servo motors at low cost

2020-09-12
After adopting the closed-loop technology, the closed-loop Stepper Motor provides users with excellent accuracy and efficiency, which can not only achieve the performance of a servo motor, but also has the low price advantage of a Stepper motor. Lower-cost stepper motors are gradually penetrating into the application fields originally dominated by high-cost servo motors.

The comparison of stepping motor and servo motor
According to the traditional concept, the performance of the servo control system is better in applications that require speeds exceeding 800rpm and high dynamic response. Stepper motors are more suitable for applications with low to medium acceleration, low speed, and high holding torque.


The detailed analysis of stepper motor and servo motor is as follows:

1. Simplicity and cost
Stepping motors are not only cheaper than servo motors, but also easier to debug and maintain. The stepper motor is stable at rest and can maintain its position (even with dynamic loads). However, if certain applications have higher performance requirements, more expensive and more complex servo motors must be used.

2, positioning
In applications that need to know the exact position of the machine at any time, there are important differences between stepper motors and servo motors. In an open-loop motion application controlled by a stepper motor, the control system believes that the motor is always in the correct motion state. However, after encountering a problem, such as a motor stall due to a stuck component, the controller cannot understand the actual position of the machine, resulting in a loss of position. The closed-loop system of the servo motor itself has an advantage: if it gets stuck by an object, it will be detected immediately. The machine will stop operating and never lose its position.

3, structure
The stepping motor rotates in a step-by-step manner, using a magnetic coil to gradually pull a magnet from one position to the next. To make the motor move 100 positions in any direction, the circuit needs to perform 100 steps on the motor. Stepper motors use pulses to achieve incremental motion, which can achieve precise positioning without using any feedback sensors.
The movement method of the servo motor is different. It connects a position sensor-an encoder-to the magnetic rotor to continuously detect the exact position of the motor. The servo will monitor the difference between the actual motor position and the commanded position, and adjust the current accordingly. This closed-loop system can keep the motor in the correct state of motion.

4. Heat and energy consumption
The open loop stepper motor uses a fixed current and emits a lot of heat. The closed-loop control only provides the current required by the speed loop, thus avoiding the problem of motor heating.
Servo control system is most suitable for high-speed applications involving dynamic load changes, such as robotic arms. Stepping control systems are more suitable for applications that require low to medium acceleration and high holding torque, such as 3D printers, conveyor belts, and countershafts. Because the cost of stepping motors is lower, after use, the cost of the automation system can be reduced. If the motion control system needs to use the characteristics of servo motors, it must prove that these higher-cost motors are worth the money.
Driven by the progress of closed-loop technology, stepper motors can penetrate into the high-performance and high-speed application fields that were formerly servo motors.

5, speed and torque
The performance difference between stepper motor and servo motor stems from their different motor design schemes. The number of poles of a stepper motor is much more than that of a servo motor. Therefore, a stepper motor rotates a full circle, and the required winding current exchange times are much more, which causes its torque to drop rapidly as the speed increases. In addition, if the maximum torque is reached, the stepper motor may lose the speed synchronization function. For these reasons, in most high-speed applications, servo motors are the preferred solution. In contrast, a stepper motor with more poles has an advantage at low speeds, because a stepper motor has a torque advantage compared to a servo motor of the same size.
As the speed increases, the torque of the stepper motor will decrease.


How does the advantage of closed-loop servo technology apply to stepper motors?
Can we realize the cost advantages of stepper motors while achieving performance similar to that of servo motors?
By combining closed-loop control technology, stepper motors will become a low-cost comprehensive product with the advantages of both servo and stepper motors. Because closed-loop stepper motors can significantly improve performance and energy efficiency, they can replace more expensive servo motors in more and more high-standard applications.
Next, we take Zhengde intelligent control stepper motor with embedded closed-loop control function as an example to analyze the performance and advantages and disadvantages of stepper motor using closed-loop technology.
The stepper motor of Zhengde intelligent control products adopting closed-loop control after integrated electronic control is equivalent to a two-phase Brushless DC Motor, which can perform position loop control, speed loop control, DQ control, and other algorithms. A single-turn absolute encoder is used to achieve closed-loop commutation to ensure that the best torque can be achieved at any speed.


Low energy consumption and keep cool
MAINTEX stepping motor has high energy efficiency. Unlike the open loop stepper motor that always operates in accordance with the full current command, which will cause heating and noise problems, the current of Zhengde Intelligent Control will change according to the actual situation of the movement, such as during acceleration and deceleration. Similar to servos, at any moment, the current consumed by these stepper motors is proportional to the actual torque required. Because the motor and integrated electronic control board run at a lower temperature, Zhengde intelligent control stepping motors can achieve higher peak torque similar to servo motors.
Even at high speeds, Zhengde intelligent control stepping motors require less current.


Exactly match performance requirements
In order to ensure that there is enough torque to overcome interference and avoid out-of-step, open-loop stepper motors usually have to ensure that the torque is at least 40% higher than the value required by the application. The closed-loop Zhengde intelligent control stepper motor does not have this problem. When these stepper motors reach a stall state due to overload, they will continue to maintain the load state without losing torque. After the overload condition is eliminated, they will continue to run. At any specified speed, the maximum torque can be guaranteed, and the position sensor can be used to ensure that it will not lose step. Therefore, the specifications of the closed-loop stepper motor can accurately match the torque requirements of the relevant application without an additional 40% margin.
For an open-loop stepper motor, it is difficult to meet the high transient torque demand because of the risk of losing step. Zhengde intelligent control closed-loop stepper motor can achieve fast acceleration, lower running noise, and has less resonance than traditional stepper motors. They can operate at higher bandwidths and achieve excellent performance.
Closed-loop stepper motors have changed the performance-cost ratio in many motion control applications. Because of its excellent precision and energy efficiency, Zhengde intelligent control stepping motors can be used in the fields that used to be more expensive servo motors. Zhengde intelligent control closed-loop progressive motor can replace high-cost servo motors with low-cost stepper motors.

Shenzhen Maintex Intelligent Control Co., Ltd.
Business Type:Manufacturer
Product Range:DC Motor , AC Motor , Stepper Motor
Products/Service:Stepper Motor , Brushless motor , Dc motor , treadmill used motor , Brushed Dc Motor , Fuji motor
Certificate:ISO14001 , ISO/TS16949 , ISO9001 , RoHS
Company Address:Zhengde Science Park, No. 8, Pingdi Street, Longgang District, Shenzhen, Guangdong, China

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