Views: 21 Author: Site Editor Publish Time: 2023-01-03 Origin: Site
Most stepper motor based motion control systems operate in the open loop state and thus provide a low cost solution. However, when the stepper motor drives the load in the open loop mode, there is the possibility of step loss between the command step and the actual step. In order to avoid this possibility, closed-loop stepper servo system is developed.
Closed-loop stepper servo system, as an innovation of traditional open-loop stepper system, provides a cost-effective option for applications with higher safety, reliability or product quality requirements. A position feedback device is installed behind the stepper motor or a closed loop like a servo system is formed by some indirect parameter detecting the position, so as to detect the motor gridlock and ensure the motor with higher speed, accuracy and greater effective torque output. Closed-loop stepper servo system has the following advantages:
Under the same voltage and current control conditions, compared with the traditional open-loop stepper system, the speed range of closed-loop stepper servo system can run smoothly from 0.1-3000RPM, the effective torque is increased to more than 60% of the holding torque, and the temperature and noise are reduced at the same time.
In the case of 90 degrees short stroke positive and negative stepper motor, T-type acceleration and deceleration speed can reach 1000rad/s/s, speed can reach 800rpm, positioning time <80ms,1 minute round-trip frequency can reach more than 700 times, still can ensure the accurate positioning of the target position.
Because stepper motors have larger torques at low speeds, larger continuous torques can be used in the low-speed rotation zone compared with conventional servomotors, thus achieving miniaturization of system size.
Because the stepper motor has torque retention characteristic when it stops, unlike the servo system, which has micro-vibration when it stops, it can realize the complete stop of the motor, so as to improve the repeated positioning accuracy of the motion system.
500,1000,2000,4000,5000,20000 P/R encoder resolution optional, up to 80000 pulse per revolution position instruction resolution.
Because of the closed-loop sine wave vector control, like servo, the motor current is controlled according to the size of the load, so it can reduce the motor heating, reduce the motor operating temperature, and achieve high efficiency.
Closed-loop stepper systems, while gaining many benefits, introduce a little extra cost.However, compared with other closed-loop motion control technologies, closed-loop stepper servo system is still a low-cost solution, even if the cost of the feedback device is increased a little.
The accuracy of the results is worth the extra cost. The cost of an error in an important application is much higher than the cost of the feedback element. The encoder or rotary transformer acts as a kind of advance insurance to assure us that the stepper motor is working in the correct position.
Improved accuracy and quality of parts result from closed-loop control, which compares the actual measured position to the ideal position in the machine or motion system. If the two are inconsistent, the motor moves to compensate for any missteps. Whether the costs and benefits of feedback devices and closed-loop methods are reasonable will depend on the specific application. The amount of additional cost involved depends on the required machine performance, production efficiency, positional accuracy, and desired part quality.
The value of materials in the controlled process also affects the balance of costs. Stepper motors are often used to handle very expensive materials, from electronic components to DNA samples, and it is worth adding a little extra motor feedback to prevent failure.
It is generally believed that the stepper servo system is between the traditional open-loop stepper and AC servo in terms of cost and performance, and has little market value at all.However, we believe that the characteristics of high cost performance, small size and high dynamic response of stepper servo system have irreplaceable advantages in the application of short stroke and high speed forward and reverse rotation.It can not only meet the performance requirements that open-loop stepper can not achieve, but also has the advantages of miniaturization and low cost compared with AC servo system. It is especially suitable for application in semiconductor, textile, medical, numerical control industry in some special requirements of automation equipment, so it has a broad market application prospect.
