Stepper motor out of step reasons analysis and solution - Database & Sql Blog Articles

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For the economical CNC ship in the process of machining, the reason for the stepping motor out of step is analyzed comprehensively, and the corresponding solutions are proposed.
The open-loop CNC system consisting of stepping motor and drive circuit has been widely used in economical CNC machine tools due to its simple structure, low price and reliable performance. It plays an important role in the numerical control process of China's machine tool industry. status. Stepper motors are often used for precise positioning, thus ensuring that the motor does not lose step.

Out-of-step and its harm to the normal operation of the stepper motor, each step of the control pulse is moved to move a step angle, that is, further. If the control pulse is continuously input, the motor continuously rotates accordingly. Stepping motor out of step includes lost steps and steps. When the step is lost, the number of steps the rotor advances is smaller than the number of pulses; when the step is exceeded, the number of steps the rotor advances is more than the number of pulses. The number of steps lost and stepped is equal to an integral multiple of the number of beats. When the step is lost, the rotor will stay in one position or vibrate around one position. When the step is serious, the machine will overshoot. The stepping motor is an important part of the open loop feed system, and its performance directly affects the performance of the CNC system. Motor out of step will affect the stability and control accuracy of the CNC system, resulting in a decrease in machining accuracy of CNC machine tools.

Reasons for loss of step and solution
1. Rotor's Acceleration Slow Substepping Motor's Rotating Magnetic Field The rotor's force n is slower than the stepping motor's rotating magnetic field, ie, below the commutation speed, the stepper motor produces an out-of-step. This is because the electric energy input to the motor is insufficient, and the synchronizing torque generated in the stepping motor cannot cause the rotor speed to follow the rotational speed of the stator magnetic field, thereby causing out-of-step. Since the dynamic output torque of the stepping motor decreases as the continuous operating frequency increases, any operating frequency higher than this frequency will result in a lost step. This out-of-step indicates that the torque of the stepping motor is insufficient and the dragging ability is insufficient. Solution: 1 Increase the electromagnetic torque generated by the stepping motor itself. Therefore, the drive current can be appropriately increased within the rated current range; when the torque in the high frequency range is insufficient, the drive voltage of the drive circuit can be appropriately increased; and the stepping motor with a large torque can be used instead. 2 Reduce the torque that the stepper motor needs to overcome. To this end, the motor operating frequency can be appropriately reduced to increase the output torque of the motor; a longer acceleration time is set so that the rotor obtains sufficient energy.

2. The average speed of the rotor is higher than the average rotational speed of the stator magnetic field. The average speed of the rotor is higher than the average rotational speed of the stator magnetic field. At this time, the stator energizes for a longer time, which is longer than the time required for the rotor step, and the rotor is in the stepping process. Excessive energy is obtained, so that the output torque generated by the stepping motor is increased, thereby making the motor step by step. When a stepping motor is used to drive those mechanisms that act to move the load up and down, it is more likely to cause a step-by-step phenomenon because the torque required by the motor decreases when the load moves downward. Solution: Reduce the drive current of the stepper motor to reduce the output torque of the stepper motor.

3. The inertia of the stepping motor and the loaded load is due to the inertia of the stepping motor itself and the loaded load, so that the motor can not be started and stopped immediately during the working process, but the lost step occurs during starting, and the step occurs when stopping. Solution: Through an acceleration and deceleration process, that is, start at a lower speed, then gradually accelerate to a certain speed, and then gradually slow down until it stops. Proper and smooth acceleration and deceleration control is the key to ensure reliable, efficient and accurate operation of the stepper drive system.
4. Resonance resonance of a stepper motor is also a cause of out-of-step. When the stepping motor is in continuous operation, if the frequency of the control pulse is equal to the natural frequency of the stepping motor, resonance will occur. During a control pulse period, the vibration is not sufficiently attenuated, and the next pulse comes, so that the dynamic error is greatest near the resonance frequency and causes the stepper motor to lose synchronization. Solution: Appropriately reduce the driving current of the stepping motor; adopt the subdivision driving method; adopt the damping method, including the mechanical damping method. The above methods can effectively eliminate motor oscillation and avoid out-of-step phenomenon.