What Is a Stepper Actuator?

A stepper actuator is an electric actuator type that makes use of a stepper motor capable of producing high levels of output accuracy. Stepper motors are a special class of brushless electric motor that may be rotated in very precise increments, or "steps." When used in stepper actuators in conjunction with precision mechanisms, this rotational control allows the actuator to be used to advance or retard through its range of motion and accurately stop at pre-defined points. These actuators are typically used in applications such as auto-focus cameras and telescope lenses, as well as precision engineering equipment that require high accuracy levels. The stepper actuator is generally used in low-torque applications and is driven by a dedicated stepper motor controller that dictates the actuator output according to pre-programmed data or system inputs.

Stepper motors are used in environments where very precise output control is required. Depending on the specific motor construction, stepper motors may have upwards of 60 individual positions at which they can be stopped during a full, 360° rotation. This allows very precise rotational control of the motor and, when integrated into a stepper actuator, accurate control of the range of actuation motion. In addition, the internal mechanisms of this type of actuator are machined to closer tolerances than is the norm with conventional types, further enhancing the degree of accuracy possible.

The stepper actuator may produce linear or rotary outputs and is commonly used in high-precision applications such as the auto-focus mechanism used in camera and telescope lenses and large microscopes. They are also utilized in manufacturing or engineering processes that require highly accurate advancement of machine process components. Robotics is another of the many industries where the precise control possible with stepper actuators is harnessed. Stepper motors are relatively low powered and have set, constant power output ranges, so, in most cases, the applications where they are used as actuation agents will only require moderate torque and be more focused on accuracy than power.

Control of a stepper actuator is achieved via a stepper motor controller that instructs the stepper motor to stop and start at predefined points, and on how fast or far it should extend. This control regimen may be pre-programmed or be dictated by specific system inputs. Generally, at least a set of positional sensors will be included to indicate to the controller exactly where the actuator mechanism is in relation to the rest of the system.