Closed-loop Control Brings More Application Value To Stepper Motor

- Jun 12, 2018-

Closed-loop Control Brings more Application value to Stepper Motor

Closed-loop stepper motors,(hybrid servo motor) provide high accuracy and efficiency for applications that require performance of servo motor.

Technological advancements are changing the price/performance ratio between stepper motors and servomotors to meet a variety of demanding industrial automation applications. With closed-loop technology, some of the economical stepper motors have entered applications that are considered unsuitable for more expensive servomotor applications. Technological advancements are changing the price/performance ratio between stepper motors and servomotors to meet a variety of demanding industrial automation applications. By using closed-loop technology, cheaper stepper motors are moving into areas that are considered to be only more expensive servo motors.


Conventional wisdom holds that servo control systems are advantageous for applications that require speeds higher than 800rpm and require highly dynamic response. Stepper motors are a better choice for applications that operate at low speeds, produce low-to-moderate acceleration, and require high holding torque.

When the closed-loop stepper motors(hybrid servo motor) are overloaded to stall, they will remain without losing torque. After removing the blocking load, they will continue to run. The maximum torque at any set speed can be guaranteed without the position sensor losing the number of steps. Therefore, the selection of closed-loop stepper motors can closely match the torque requirements of their application without the need for 40% extra margin.

For an open-loop stepper motor, the requirement of high instantaneous torque is difficult to achieve due to the risk of losing the number of steps. Closed-loop stepper motors can achieve very fast accelerations, can operate silently, have less resonance than traditional stepper motors, and can operate at higher bandwidths. Stepper motor designers integrate electronic systems with motors to reduce cabling, simplify implementation, and implement cabinetless machines.


A global automation company improved its precision CNC machine tools for window and wood frame production and sales. Instead of using servo motors, it used closed-loop stepper motors instead. Prior to the transition, the application and process of manufacturing wooden frames required the use of 20 to 30 pneumatic and electronic servo motors in each machine. The cost of servo motors is a major factor in the overall cost of each machine. The extra number of cables required for a single, servo encoder mounted in the cabinet lengthens the installation time and further complicates the maintenance work.

In a cost-reduction pilot project, closed-loop stepper motors were used instead of servo motors in a woodworking machine to see if the stepper motors achieved their performance goals. Only change the motor, motion controller and communication protocol remain unchanged. A few months later, with technical support, the company determined that its stepper motor-based machine had achieved its goal of implementation. Thanks to the integration of the stepper motor and the electronic system, fewer cables are required, so the maintenance work is also simpler.


The next step is to determine if the machine on which the stepper motor is installed meets accuracy, acceleration, energy consumption, and other performance criteria. After a one-month trial run, the company discovered that closed-loop stepper motors allowed its machines to meet all technical specifications and machine performance requirements while reducing complexity and reducing the cost of each machine by more than 5%.


Closed-loop stepper motors can change the cost-effectiveness of motion control. Superior accuracy and energy efficiency allow stepper motors to operate in areas where more expensive servo motors dominate. Closed-loop stepper motors can be used in multi-axis applications, positioning tasks when the load changes, and applications that require quiet operation, short settling time, and high accuracy requirements.

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