An automated teller machine (ATM) is a highly sophisticated mechatronic device. Its core function-depositing and withdrawing banknotes-relies on a complex and reliable transport system. The heart of this system is, in most cases, a stepper motor.
Why a stepper motor?
ATM operating environments place extremely stringent demands on motion control:
Precise position control: Banknotes or cards must be accurately moved to a specific position, down to the millimeter level or even smaller (for example, to the cash dispenser, under the scanner, or into various cassettes).
Holding torque: When the motor is stopped, it must be able to securely lock its position to prevent movement due to external forces (such as a slight banknote jam), ensuring accurate positioning.
Open-loop control: Stepper motors achieve precise positioning without relying on feedback devices such as encoders (although high-end ATMs may also use closed-loop stepper or servo motors for improved reliability). This simplifies system architecture and reduces costs.
Smooth, low-speed operation is required to avoid tearing or abrading fragile banknotes caused by high-speed movement.
Stepper motors perfectly match these requirements. They operate by receiving a pulse signal, with each pulse driving the motor to rotate a fixed angle (one step). By sending a specific number of pulses, the controller can precisely control the angle and number of revolutions of the motor, thereby controlling the movement of the conveyor belt.
