Closed Loop Stepper Motor

 Traditional stepper systems operate in open loop condition provide position control without feedback from stepper motors to the controlling stepper drives. In a stepper system, the stepper drive keeps outputting preset current into the controlled stepper motor to move the attached load to the target positions. It does not know the current motor movement position, even when loss of movement synchronization (difference between desired move distance and actual moved distance) has happened and caused "Loss of Steps". Therefore, engineers have to make huge torque reservation (30-50%) to ensure "NO" loss of steps would happen. But because of the "open loop" feature of stepper systems, it is still commonly seen that loss of steps happens, especially in quick acceleration or quick torque require changes. That could result in wasting processed materials, crushing control systems, or even damaging machines. That's one of the main reasons limiting the adoption of stepper technology in many motion control applications.

In the past, when an application requires real-time closed loop "servo" operation, engineers are forced to choose servo systems at much higher costs and with more complexity. But in many applications, because traditional servo systems lack of high torque feature of stepper systems, high power servo motors have to be chosen, or expensive planetary gearboxes have to be added to achieve desired torque. In addition, hard to tune, hunting ("shaking when moving"), overshooting, and long settling time are also known problematic issues for many servo systems

With the implementation of high resolution encoders, Leadshine easy servo systems apply servo controls on stepper motors. In an easy servo system, the shaft position of the driven stepper motor is fed back to the controlling easy servo drive in real time (every 50 micro second for 1000 line encoders). The easy servo drive can then correct the position error, close the position loop between the drive & motor, and totally eliminate the possibility of loss of movement synchronization. Because Leadshine easy servo systems are actually hybrid of stepper and brushless servo systems, they inherit desired features available in both technologies. Leadshine easy servos are easy to implement (almost "plug and play"), low cost, high torque, high precision, no loss of steps, extra low motor heating, no hunting, no overshooting, almost zero settling time, broad application range. They have been successfully implemented in many industrial such as CNC machinery (CNC routers, plasma, laser engravers/cutters, grinding machines, milling machines, etc), semiconductor, medical, lab automation, packaging..